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Liu M, Dong H, Mazlout A, Wu Y, Kalyanasundaram A, Oshinski JN, Sun W, Elefteriades JA, Leshnower BG, Gleason RL. The role of anatomic shape features in the prognosis of uncomplicated type B aortic dissection initially treated with optimal medical therapy. Comput Biol Med 2024; 170:108041. [PMID: 38330820 DOI: 10.1016/j.compbiomed.2024.108041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 12/28/2023] [Accepted: 01/26/2024] [Indexed: 02/10/2024]
Abstract
OBJECTIVE Currently, the long-term outcomes of uncomplicated type B aortic dissection (TBAD) patients managed with optimal medical therapy (OMT) remain poor. Aortic expansion is a major factor that determines patient long-term survival. The objective of this study was to investigate the association between anatomic shape features and (i) OMT outcome; (ii) aortic growth rate for TBAD patients initially treated with OMT. METHODS 108 CT images of TBAD in the acute and chronic phases were collected from 46 patients who were initially treated with OMT. Statistical shape models (SSM) of TBAD were constructed to extract shape features from the earliest initial CT scans of each patient by using principal component analysis (PCA) and partial least square (PLS) regression. Additionally, conventional shape features (e.g., aortic diameter) were quantified from the earliest CT scans as a baseline for comparison. We identified conventional and SSM features that were significant in separating OMT "success" and failure patients. Moreover, the aortic growth rate was predicted by SSM and conventional features using linear and nonlinear regression with cross-validations. RESULTS Size-related SSM and conventional features (mean aortic diameter: p=0.0484, centerline length: p=0.0112, PCA score c1: p=0.0192, and PLS scores t1: p=0.0004, t2: p=0.0274) were significantly different between OMT success and failure groups, but these features were incapable of predicting the aortic growth rate. SSM shape features showed superior results in growth rate prediction compared to conventional features. Using multiple linear regression, the conventional, PCA, and PLS shape features resulted in root mean square errors (RMSE) of 1.23, 0.85, and 0.84 mm/year, respectively, in leave-one-out cross-validations. Nonlinear support vector regression (SVR) led to improved RMSE of 0.99, 0.54, and 0.43 mm/year, for the conventional, PCA, and PLS features, respectively. CONCLUSION Size-related shape features of the earliest scan were correlated with OMT failure but led to large errors in the prediction of the aortic growth rate. SSM features in combination with nonlinear regression could be a promising avenue to predict the aortic growth rate.
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Affiliation(s)
- Minliang Liu
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Department of Mechanical Engineering, Texas Tech University, Lubbock, TX, USA
| | - Hai Dong
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Division of Cardiothoracic Surgery, Department of Surgery, Emory University School of Medicine, Atlanta, GA, USA
| | - Adam Mazlout
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Yuxuan Wu
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Asanish Kalyanasundaram
- Aortic Institute at Yale-New Haven Hospital, Yale University School of Medicine, New Haven, CT, USA
| | - John N Oshinski
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Department of Radiology & Imaging Science, Emory University, Atlanta, GA, USA
| | - Wei Sun
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - John A Elefteriades
- Aortic Institute at Yale-New Haven Hospital, Yale University School of Medicine, New Haven, CT, USA
| | - Bradley G Leshnower
- Division of Cardiothoracic Surgery, Department of Surgery, Emory University School of Medicine, Atlanta, GA, USA
| | - Rudolph L Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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2
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Sedaghati F, Dixon JB, Gleason RL. A 1D model characterizing the role of spatiotemporal contraction distributions on lymph transport. Sci Rep 2023; 13:21241. [PMID: 38040740 PMCID: PMC10692214 DOI: 10.1038/s41598-023-48131-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 11/22/2023] [Indexed: 12/03/2023] Open
Abstract
Lymphedema is a condition in which lymph transport is compromised. The factors that govern the timing of lymphatic contractions are largely unknown; however, these factors likely play a central role in lymphatic health. Computational models have proven useful in quantifying changes in lymph transport; nevertheless, there is still much unknown regarding the regulation of contractions. The purpose of this paper is to utilize computational modeling to examine the role of pacemaking activity in lymph transport. A 1D fluid-solid modeling framework was utilized to describe the interaction between the contracting vessel and the lymph flow. The distribution of contractions along a three-lymphangion chain in time and space was determined by specifying the pacemaking sites and parameters obtained from experimentation. The model effectively replicates the contractility patterns in experiments. Quantitatively, the flow rates were measured at 5.44 and 2.29 [Formula: see text], and the EF values were 78% and less than 33% in the WT and KO models, respectively, which are consistent with the literature. Applying pacemaking parameters in this modeling framework effectively captures lymphatic contractile wave propagations and their relation to lymph transport. It can serve as a motivation for conducting novel studies to evaluate lymphatic pumping function during the development of lymphedema.
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Affiliation(s)
- Farbod Sedaghati
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - J Brandon Dixon
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- The Wallace H. Coulter Georgia Tech/Emory Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
- The Wallace H. Coulter Georgia Tech/Emory Department of Biomedical Engineering, Georgia Institute of Technology, 387 Technology Circle, Room 216F, Atlanta, GA, 30313, USA.
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3
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Dong H, Liu M, Woodall J, Leshnower BG, Gleason RL. Effect of Nonlinear Hyperelastic Property of Arterial Tissues on the Pulse Wave Velocity Based on the Unified-Fiber-Distribution (UFD) Model. Ann Biomed Eng 2023; 51:2441-2452. [PMID: 37326947 DOI: 10.1007/s10439-023-03275-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 06/01/2023] [Indexed: 06/17/2023]
Abstract
Pulse wave velocity (PWV) is a key, independent risk factor for future cardiovascular events. The Moens-Korteweg equation describes the relation between PWV and the stiffness of arterial tissue with an assumption of isotopic linear elastic property of the arterial wall. However, the arterial tissue exhibits highly nonlinear and anisotropic mechanical behaviors. There is a limited study regarding the effect of arterial nonlinear and anisotropic properties on the PWV. In this study, we investigated the impact of the arterial nonlinear hyperelastic properties on the PWV, based on our recently developed unified-fiber-distribution (UFD) model. The UFD model considers the fibers (embedded in the matrix of the tissue) as a unified distribution, which expects to be more physically consistent with the real fiber distribution than existing models that separate the fiber distribution into two/several fiber families. With the UFD model, we fitted the measured relation between the PWV and blood pressure which obtained a good accuracy. We also modeled the aging effect on the PWV based on observations that the stiffening of arterial tissue increases with aging, and the results agree well with experimental data. In addition, we did parameter studies on the dependence of the PWV on the arterial properties of fiber initial stiffness, fiber distribution, and matrix stiffness. The results indicate the PWV increases with increasing overall fiber component in the circumferential direction. The dependences of the PWV on the fiber initial stiffness, and matrix stiffness are not monotonic and change with different blood pressure. The results of this study could provide new insights into arterial property changes and disease information from the clinical measured PWV data.
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Affiliation(s)
- Hai Dong
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Minliang Liu
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Julia Woodall
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Bradley G Leshnower
- Division of Cardiothoracic Surgery, Department of Surgery, Emory University School of Medicine, Atlanta, GA, USA
| | - Rudolph L Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 204, 387 Technology Circle, Atlanta, GA, 30313-2412, USA.
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4
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Dong H, Ferruzzi J, Liu M, Brewster LP, Leshnower BG, Gleason RL. Effect of Aging, Sex, and Gene (Fbln5) on Arterial Stiffness of Mice: 20 Weeks Adult Fbln5-knockout Mice Have Older Arteries than 100 Weeks Wild-Type Mice. bioRxiv 2023:2023.05.30.542920. [PMID: 37398425 PMCID: PMC10312538 DOI: 10.1101/2023.05.30.542920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The arterial stiffening is a strong independent predictor of cardiovascular risk and has been used to characterize the biological age of arteries ('arterial age'). Here we revealed that the Fbln5 gene knockout (Fbln5 -/- ) significantly increases the arterial stiffening for both male and female mice. We also showed that the arterial stiffening increases with natural aging, but the stiffening effect of Fbln5 -/- is much more severe than aging. The arterial stiffening of 20 weeks old mice with Fbln5 -/- is much higher than that at 100 weeks in wild-type (Fbln5 +/+ ) mice, which indicates that 20 weeks mice (equivalent to ∼26 years old humans) with Fbln5 -/- have older arteries than 100 weeks wild-type mice (equivalent to ∼77 years humans). Histological microstructure changes of elastic fibers in the arterial tissue elucidate the underlying mechanism of the increase of arterial stiffening due to Fbln5-knockout and aging. These findings provide new insights to reverse 'arterial age' due to abnormal mutations of Fbln5 gene and natural aging. This work is based on a total of 128 biaxial testing samples of mouse arteries and our recently developed unified-fiber-distribution (UFD) model. The UFD model considers the fibers in the arterial tissue as a unified distribution, which is more physically consistent with the real fiber distribution of arterial tissues than the popular fiber-family-based models (e.g., the well-know Gasser-Ogden-Holzapfel [GOH] model) that separate the fiber distribution into several fiber families. Thus, the UFD model achieves better accuracies with less material parameters. To our best knowledge, the UFD model is the only existing accurate model that could capture the property/stiffness differences between different groups of the experimental data discussed here.
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5
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Sedaghati F, Gleason RL. A mathematical model of vascular and hemodynamics changes in early and late forms of preeclampsia. Physiol Rep 2023; 11:e15661. [PMID: 37186372 PMCID: PMC10132946 DOI: 10.14814/phy2.15661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 03/15/2023] [Accepted: 03/16/2023] [Indexed: 05/17/2023] Open
Abstract
Preeclampsia-eclampsia syndrome is a leading cause of maternal mortality. The precise etiology of preeclampsia is still not well-defined and different forms exist, including early and late forms or preeclampsia, which may arise via distinctly different mechanisms. Low-dose aspirin administered at the end of the first trimester in women identified as high risk has been shown to reduce the incidence of early, but not late, preeclampsia; however, current risk factors show only fair predictive capability. There is a pressing need to develop accurate descriptions for the different forms of preeclampsia. This paper presents 1D fluid, solid, growth, and remodeling models for pregnancies complicated with early and late forms of preeclampsia. Simulations affirm a broad set of literature results that early forms of preeclampsia are characterized by elevated uterine artery pulsatility index (UA-PI) and total peripheral resistance (TPR) and lower cardiac output (CO), with modestly increased mean arterial blood pressure (MAP) in the first half of pregnancy, with elevation of TPR and MAP beginning at 20 weeks. Conversely, late forms of preeclampsia are characterized by only slightly elevated UA-PI and normal pre-term TPR, and slightly elevated MAP and CO throughout pregnancy, with increased TPR and MAP beginning after 34 weeks. Results suggest that preexisting arterial stiffness may be elevated in women that develop both early forms and late forms of preeclampsia; however, data that verify these results are lacking in the literature. Pulse wave velocity increases in early- and late-preeclampsia, coincident with increases in blood pressure; however, these increases are mainly due to the strain-stiffening response of larger arteries, rather than arterial remodeling-derived changes in material properties. These simulations affirm that early forms of preeclampsia may be associated with abnormal placentation, whereas late forms may be more closely associated with preexisting maternal cardiovascular factors; simulations also highlight several critical gaps in available data.
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Affiliation(s)
- Farbod Sedaghati
- The George W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaGeorgiaUSA
| | - Rudolph L. Gleason
- The George W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaGeorgiaUSA
- The Wallace H. Coulter Department of Biomedical EngineeringGeorgia Institute of TechnologyAtlantaGeorgiaUSA
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6
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Brewster LP, Li F, Omojola V, Kumar S, Gleason RL, Jo H. Role of Cellular Communication Network Factor 2 and Male Sex on Flow-mediated Arterial Remodeling and Atherosclerotic Plaque Formation. JVS Vasc Sci 2022. [DOI: 10.1016/j.jvssci.2022.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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7
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Brewster LP, Li F, Omojola V, Kumar S, Gleason RL, Jo H. Abstract 137: Role Of Cellular Communication Network Factor 2 (ccn2) And Male Sex On Flow-mediated Arterial Remodeling And Atherosclerotic Plaque Formation. Arterioscler Thromb Vasc Biol 2022. [DOI: 10.1161/atvb.42.suppl_1.137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
CCN2 or connective tissue growth factor is up-regulated in response to disturbed flow and arterial stiffening. Carotid artery disease and peripheral arterial disease (PAD) are associated with disturbed flow and arterial stiffening. We have identified a key role for CCN2 in stiffened arterial remodeling and flow-mediated focal atherosclerotic plaque formation in translational models of carotid and PAD and in patient carotid plaques/PAD arteries. The objective of this project was to determine the modifiability of CCN2 pathways in pathologic arterial remodeling and atherosclerosis.
Methods:
To test our hypothesis that CCN2 was an important mediator of pathology arterial remodeling in vascular disease , we utilized murine models of stiffened arteries (fibulin-5 KO) in atherogenic conditions (PCSK9 + HFD) and clinical arterial tissue from patients with PAD and carotid artery disease.
Results:
Disturbed flow increases EC expression of CCN2 3.5 fold in WT carotid arteries. This is doubled again in Fibulin 5 KO (
KO
) carotid arteries. These KO carotid arteries are ~3x stiffer than littermate control arteries, which is a similar ratio of PAD compared to healthy control arteries (
1A
). Under disturbed flow and atherogenic conditions KO arteries had more elastin breaks (P=.04), greater plaque area (P=.007) and more lipid deposition (P=.02), and Glagov’s outward remodeling (P=.02) (
1B/C
). This was most pronounced in male mice. CCN2 staining is significantly increased in PAD arteries and carotid endarterectomy plaques (P<.05) (
1D/E
). To evaluate the modifiability of CCN2, we utilized CCN2
ECKO
animals. We found that male (but not female) CCN2
ECKO
animals had significantly less atherosclerotic plaque burden (P=.001) and similar elastin breaks/lipid deposition compared to littermate controls (
1F/G
).
Conclusion:
CCN2 may play an important and modifiable role in flow-mediated pathologic arterial remodeling and focal atherosclerotic plaque burden.
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Affiliation(s)
| | - Feifei Li
- EMORY UNIVERSITY HOSPITAL, Atlanta, GA
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8
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Dong H, Liu M, Qin T, Liang L, Ziganshin B, Ellauzi H, Zafar M, Jang S, Elefteriades J, Sun W, Gleason RL. A novel computational growth framework for biological tissues: Application to growth of aortic root aneurysm repaired by the V-shape surgery. J Mech Behav Biomed Mater 2022; 127:105081. [DOI: 10.1016/j.jmbbm.2022.105081] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/28/2021] [Accepted: 01/08/2022] [Indexed: 01/15/2023]
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9
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Razavi MS, Dixon JB, Gleason RL. Characterization of rat tail lymphatic contractility and biomechanics: incorporating nitric oxide-mediated vasoregulation. J R Soc Interface 2020; 17:20200598. [PMID: 32993429 DOI: 10.1098/rsif.2020.0598] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The lymphatic system transports lymph from the interstitial space back to the great veins via a series of orchestrated contractions of chains of lymphangions. Biomechanical models of lymph transport, validated with ex vivo or in vivo experimental results, have proved useful in revealing novel insight into lymphatic pumping; however, a need remains to characterize the contributions of vasoregulatory compounds in these modelling tools. Nitric oxide (NO) is a key mediator of lymphatic pumping. We quantified the active contractile and passive biaxial biomechanical response of rat tail collecting lymphatics and changes in the contractile response to the exogenous NO administration and integrated these findings into a biomechanical model. The passive mechanical response was characterized with a three-fibre family model. Nonlinear regression and non-parametric bootstrapping were used to identify best-fit material parameters to passive cylindrical biaxial mechanical data, assessing uniqueness and parameter confidence intervals; this model yielded a good fit (R2 = 0.90). Exogenous delivery of NO via sodium nitroprusside (SNP) elicited a dose-dependent suppression of contractions; the amplitude of contractions decreased by 30% and the contraction frequency decreased by 70%. Contractile function was characterized with a modified Rachev-Hayashi model, introducing a parameter that is related to SNP concentration; the model provided a good fit (R2 = 0.89) to changes in contractile responses to varying concentrations of SNP. These results demonstrated the significant role of NO in lymphatic pumping and provide a predictive biomechanical model to integrate the combined effect of mechanical loading and NO on lymphatic contractility and mechanical response.
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Affiliation(s)
- Mohammad S Razavi
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA 30313, USA
| | - J Brandon Dixon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA 30313, USA.,Wallace H. Coulter Department of Biomedical Engineering, 313 Ferst Drive, Atanta, GA 30332, USA.,Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA
| | - Rudolph L Gleason
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA 30313, USA.,Wallace H. Coulter Department of Biomedical Engineering, 313 Ferst Drive, Atanta, GA 30332, USA.,Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA
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10
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Razavi MS, Leonard-Duke J, Hardie B, Dixon JB, Gleason RL. Axial stretch regulates rat tail collecting lymphatic vessel contractions. Sci Rep 2020; 10:5918. [PMID: 32246026 PMCID: PMC7125298 DOI: 10.1038/s41598-020-62799-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 03/19/2020] [Indexed: 01/07/2023] Open
Abstract
Lymphatic contractions play a fundamental role in maintaining tissue and organ homeostasis. The lymphatic system relies on orchestrated contraction of collecting lymphatic vessels, via lymphatic muscle cells and one-way valves, to transport lymph from the interstitial space back to the great veins, against an adverse pressure gradient. Circumferential stretch is known to regulate contractile function in collecting lymphatic vessels; however, less is known about the role of axial stretch in regulating contraction. It is likely that collecting lymphatic vessels are under axial strain in vivo and that the opening and closing of lymphatic valves leads to significant changes in axial strain throughout the pumping cycle. The purpose of this paper is to quantify the responsiveness of lympatic pumping to altered axial stretch. In situ measurements suggest that rat tail collecting lymphatic vessels are under an axial stretch of ~1.24 under normal physiological loads. Ex vivo experiments on isolated rat tail collecting lymphatics showed that the contractile metrics such as contractile amplitude, frequency, ejection fraction, and fractional pump flow are sensitive to axial stretch. Multiphoton microscopy showed that the predominant orientation of collagen fibers is in the axial direction, while lymphatic muscle cell nuclei and actin fibers are oriented in both circumferential and longitudinal directions, suggesting an axial component to contraction. Taken together, these results demonstrate the significance of axial stretch in lymphatic contractile function, suggest that axial stretch may play an important role in regulating lymph transport, and demonstrate that changes in axial strains could be an important factor in disease progression.
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Affiliation(s)
- Mohammad S Razavi
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Dr., Atlanta, GA, 30332, USA
| | - Julie Leonard-Duke
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr., Atlanta, GA, 30332, USA
| | - Becky Hardie
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr., Atlanta, GA, 30332, USA
| | - J Brandon Dixon
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Dr., Atlanta, GA, 30332, USA.,The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr., Atlanta, GA, 30332, USA.,The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Dr., Atlanta, GA, 30332, USA. .,The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Dr., Atlanta, GA, 30332, USA. .,The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Dr., Atlanta, GA, 30332, USA.
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11
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Song H, Keegan PM, Anbazhakan S, Rivera CP, Feng Y, Omojola VO, Clark AA, Cai S, Selma J, Gleason RL, Botchwey EA, Huo Y, Tan W, Platt MO. Sickle Cell Anemia Mediates Carotid Artery Expansive Remodeling That Can Be Prevented by Inhibition of JNK (c-Jun N-Terminal Kinase). Arterioscler Thromb Vasc Biol 2020; 40:1220-1230. [PMID: 32160775 DOI: 10.1161/atvbaha.120.314045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVE Sickle cell anemia (SCA) causes chronic inflammation and multiorgan damage. Less understood are the arterial complications, most evident by increased strokes among children. Proteolytic mechanisms, biomechanical consequences, and pharmaceutical inhibitory strategies were studied in a mouse model to provide a platform for mechanistic and intervention studies of large artery damage due to sickle cell disease. Approach and Results: Townes humanized transgenic mouse model of SCA was used to test the hypothesis that elastic lamina and structural damage in carotid arteries increased with age and was accelerated in mice homozygous for SCA (sickle cell anemia homozygous genotype [SS]) due to inflammatory signaling pathways activating proteolytic enzymes. Elastic lamina fragmentation observed by 1 month in SS mice compared with heterozygous littermate controls (sickle cell trait heterozygous genotype [AS]). Positive immunostaining for cathepsin K, a powerful collagenase and elastase, confirmed accelerated proteolytic activity in SS carotids. Larger cross-sectional areas were quantified by magnetic resonance angiography and increased arterial compliance in SS carotids were also measured. Inhibiting JNK (c-jun N-terminal kinase) signaling with SP600125 significantly reduced cathepsin K expression, elastin fragmentation, and carotid artery perimeters in SS mice. By 5 months of age, continued medial thinning and collagen degradation was mitigated by treatment of SS mice with JNK inhibitor. CONCLUSIONS Arterial remodeling due to SCA is mediated by JNK signaling, cathepsin proteolytic upregulation, and degradation of elastin and collagen. Demonstration in Townes mice establishes their utility for mechanistic studies of arterial vasculopathy, related complications, and therapeutic interventions for large artery damage due to SCA.
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Affiliation(s)
- Hannah Song
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Philip M Keegan
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Suhaas Anbazhakan
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Christian P Rivera
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.).,Department of Mechanics and Engineering Science at Peking University, Beijing, China (C.P.R., Y.F., Y.H., W.T.)
| | - Yundi Feng
- Department of Mechanics and Engineering Science at Peking University, Beijing, China (C.P.R., Y.F., Y.H., W.T.)
| | - Victor O Omojola
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Alexus A Clark
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Shuangyi Cai
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Jada Selma
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.)
| | - Rudolph L Gleason
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.).,Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta (R.L.G., E.A.B., M.O.P.)
| | - Edward A Botchwey
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.).,Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta (R.L.G., E.A.B., M.O.P.)
| | - Yunlong Huo
- Department of Mechanics and Engineering Science at Peking University, Beijing, China (C.P.R., Y.F., Y.H., W.T.)
| | - Wenchang Tan
- Department of Mechanics and Engineering Science at Peking University, Beijing, China (C.P.R., Y.F., Y.H., W.T.)
| | - Manu O Platt
- From the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta (H.S., P.M.K., S.A., C.P.R., V.O.O., A.A.C., S.C., J.S., R.L.G., E.A.B., M.O.P.).,Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta (R.L.G., E.A.B., M.O.P.)
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12
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Nelson TS, Nepiyushchikh Z, Hooks JST, Razavi MS, Lewis T, Clement CC, Thoresen M, Cribb MT, Ross MK, Gleason RL, Santambrogio L, Peroni JF, Dixon JB. Lymphatic remodelling in response to lymphatic injury in the hind limbs of sheep. Nat Biomed Eng 2019; 4:649-661. [PMID: 31873209 DOI: 10.1038/s41551-019-0493-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 11/15/2019] [Indexed: 02/06/2023]
Abstract
Contractile activity in the lymphatic vasculature is essential for maintaining fluid balance within organs and tissues. However, the mechanisms by which collecting lymphatics adapt to changes in fluid load and how these adaptations influence lymphatic contractile activity are unknown. Here we report a model of lymphatic injury based on the ligation of one of two parallel lymphatic vessels in the hind limb of sheep and the evaluation of structural and functional changes in the intact, remodelling lymphatic vessel over a 42-day period. We show that the remodelled lymphatic vessel displayed increasing intrinsic contractile frequency, force generation and vessel compliance, as well as decreasing flow-mediated contractile inhibition via the enzyme endothelial nitric oxide synthase. A computational model of a chain of lymphatic contractile segments incorporating these adaptations predicted increases in the flow-generation capacity of the remodelled vessel at the expense of normal mitochondrial function and elevated oxidative stress within the lymphatic muscle. Our findings may inform interventions for mitigating lymphatic muscle fatigue in patients with dysfunctional lymphatics.
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Affiliation(s)
- Tyler S Nelson
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Zhanna Nepiyushchikh
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Joshua S T Hooks
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Mohammad S Razavi
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Tristan Lewis
- College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Cristina C Clement
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Merrilee Thoresen
- College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Matthew T Cribb
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Mindy K Ross
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Rudolph L Gleason
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.,Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Laura Santambrogio
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - John F Peroni
- College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - J Brandon Dixon
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA. .,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA. .,Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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13
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Tolentino L, Yigeremu M, Teklu S, Attia S, Weiler M, Frank N, Dixon JB, Gleason RL. Three-dimensional camera anthropometry to assess risk of cephalopelvic disproportion-related obstructed labour in Ethiopia. Interface Focus 2019; 9:20190036. [PMID: 31485318 DOI: 10.1098/rsfs.2019.0036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2019] [Indexed: 11/12/2022] Open
Abstract
Cephalopelvic disproportion (CPD)-related obstructed labour requires delivery via Caesarean section (C/S); however, in low-resource settings around the world, facilities with C/S capabilities are often far away. This paper reports three low-cost tools to assess the risk of CPD, well before labour, to provide adequate time for referral and planning for delivery. We performed tape measurement- and three-dimensional (3D) camera-based anthropometry, using two 3D cameras (Kinect and Structure) on primigravida, gestational age ≥ 36 weeks, from Addis Ababa, Ethiopia. Novel risk scores were developed and tested to identify models with the highest predicted area under the receiver-operator characteristic curve (AUC), detection rate (true positive rate at a 5% false-positive rate, FPR) and triage rate (true negative rate at a 0% false-negative rate). For tape measure, Kinect and Structure, the detection rates were 53%, 61% and 64% (at 5% FPR), the triage rates were 30%, 56% and 63%, and the AUCs were 0.871, 0.908 and 0.918, respectively. Detection rates were 77%, 80% and 84% at the maximum J-statistic, which corresponded to FPRs of 10%, 15% and 11%, respectively, for tape measure, Kinect and Structure. Thus, tape measurement anthropometry was a very good predictor and Kinect and Structure anthropometry were excellent predictors of CPD risk.
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Affiliation(s)
| | - Mahlet Yigeremu
- Department of Obstetrics and Gynecology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Sisay Teklu
- Department of Obstetrics and Gynecology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Shehab Attia
- The Wallace H. Coulter Department of Biomedical Engineering, Atlanta, GA, USA
| | | | | | - J Brandon Dixon
- LymphaTech, Inc., Atlanta, GA, USA.,The George W. Woodruff School of Mechanical Engineering, Atlanta, GA, USA
| | - Rudolph L Gleason
- Because of Kennedy, Inc., Acworth, GA, USA.,The Wallace H. Coulter Department of Biomedical Engineering, Atlanta, GA, USA.,The George W. Woodruff School of Mechanical Engineering, Atlanta, GA, USA
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14
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Clark GL, Pokutta-Paskaleva AP, Lawrence DJ, Lindsey SH, Desrosiers L, Knoepp LR, Bayer CL, Gleason RL, Miller KS. Smooth muscle regional contribution to vaginal wall function. Interface Focus 2019; 9:20190025. [PMID: 31263538 PMCID: PMC6597518 DOI: 10.1098/rsfs.2019.0025] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2019] [Indexed: 12/16/2022] Open
Abstract
Pelvic organ prolapse is characterized as the descent of the pelvic organs into the vaginal canal. In the USA, there is a 12% lifetime risk for requiring surgical intervention. Although vaginal childbirth is a well-established risk factor for prolapse, the underlying mechanisms are not fully understood. Decreased smooth muscle organization, composition and maximum muscle tone are characteristics of prolapsed vaginal tissue. Maximum muscle tone of the vaginal wall was previously investigated in the circumferential or axial direction under uniaxial loading; however, the vaginal wall is subjected to multiaxial loads. Further, the contribution of vaginal smooth muscle basal (resting) tone to mechanical function remains undetermined. The objectives of this study were to determine the contribution of smooth muscle basal and maximum tone to the regional biaxial mechanical behaviour of the murine vagina. Vaginal tissue from C57BL/6 mice was subjected to extension-inflation protocols (n = 10) with and without basal smooth muscle tone. Maximum tone was induced with KCl under various circumferential (n = 5) and axial (n = 5) loading conditions. The microstructure was visualized with multiphoton microscopy (n = 1), multiaxial histology (n = 4) and multiaxial immunohistochemistry (n = 4). Smooth muscle basal tone decreased material stiffness and increased anisotropy. In addition, maximum vaginal tone was decreased with increasing intraluminal pressures. This study demonstrated that vaginal muscle tone contributed to the biaxial mechanical response of murine vaginal tissue. This may be important in further elucidating the underlying mechanisms of prolapse, in order to improve current preventative and treatment strategies.
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Affiliation(s)
- Gabrielle L. Clark
- Department of Biomedical Engineering, Tulane University, 6823 St Charles Avenue, New Orleans, LA 70118, USA
| | - Anastassia P. Pokutta-Paskaleva
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 801 Ferst Drive NW, Atlanta, GA 30332, USA
| | - Dylan J. Lawrence
- Department of Biomedical Engineering, Tulane University, 6823 St Charles Avenue, New Orleans, LA 70118, USA
| | - Sarah H. Lindsey
- Department of Pharmacology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
| | - Laurephile Desrosiers
- Department of Female Pelvic Medicine and Reconstructive Surgery, University of Queensland Ochsner Clinical School, 1514 Jefferson Highway, New Orleans, LA 70121, USA
| | - Leise R. Knoepp
- Department of Female Pelvic Medicine and Reconstructive Surgery, University of Queensland Ochsner Clinical School, 1514 Jefferson Highway, New Orleans, LA 70121, USA
| | - Carolyn L. Bayer
- Department of Biomedical Engineering, Tulane University, 6823 St Charles Avenue, New Orleans, LA 70118, USA
| | - Rudolph L. Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 801 Ferst Drive NW, Atlanta, GA 30332, USA
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Kristin S. Miller
- Department of Biomedical Engineering, Tulane University, 6823 St Charles Avenue, New Orleans, LA 70118, USA
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15
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Breed ER, Hilliard CA, Yoseph B, Mittal R, Liang Z, Chen CW, Burd EM, Brewster LP, Hansen LM, Gleason RL, Pandita TK, Ford ML, Hunt CR, Coopersmith CM. The small heat shock protein HSPB1 protects mice from sepsis. Sci Rep 2018; 8:12493. [PMID: 30131526 PMCID: PMC6104051 DOI: 10.1038/s41598-018-30752-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 05/01/2018] [Indexed: 12/29/2022] Open
Abstract
In vitro studies have implicated the small heat shock protein HSPB1 in a range of physiological functions. However, its in vivo relevance is unclear as the phenotype of unstressed HSPB1−/− mice is unremarkable. To determine the impact of HSPB1 in injury, HSPB1−/− and wild type (WT) mice were subjected to cecal ligation and puncture, a model of polymicrobial sepsis. Ten-day mortality was significantly higher in HSPB1−/− mice following the onset of sepsis (65% vs. 35%). Ex vivo mechanical testing revealed that common carotid arteries from HSPB1−/− mice were more compliant than those in WT mice over pressures of 50–120 mm Hg. Septic HSPB1−/− mice also had increased peritoneal levels of IFN-γ and decreased systemic levels of IL-6 and KC. There were no differences in frequency of either splenic CD4+ or CD8+ T cells, nor were there differences in apoptosis in either cell type. However, splenic CD4+ T cells and CD8+ T cells from HSPB1−/− mice produced significantly less TNF and IL-2 following ex vivo stimulation. Systemic and local bacterial burden was similar in HSPB1−/− and WT mice. Thus while HSPB1−/− mice are uncompromised under basal conditions, HSPB1 has a critical function in vivo in sepsis, potentially mediated through alterations in arterial compliance and the immune response.
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Affiliation(s)
- Elise R Breed
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Carolyn A Hilliard
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Benyam Yoseph
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Rohit Mittal
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Zhe Liang
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Ching-Wen Chen
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Eileen M Burd
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Luke P Brewster
- Department of Surgery, Division of Vascular Surgery, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Laura M Hansen
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, Georgia
| | - Rudolph L Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, Georgia
| | - Tej K Pandita
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Mandy L Ford
- Department of Surgery and Emory Transplant Center, Emory University School of Medicine, Atlanta, GA, Georgia
| | - Clayton R Hunt
- Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, TX, USA
| | - Craig M Coopersmith
- Department of Surgery and Emory Critical Care Center, Emory University School of Medicine, Atlanta, GA, Georgia.
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16
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Kim CW, Pokutta-Paskaleva A, Kumar S, Timmins LH, Morris AD, Kang DW, Dalal S, Chadid T, Kuo KM, Raykin J, Li H, Yanagisawa H, Gleason RL, Jo H, Brewster LP. Disturbed Flow Promotes Arterial Stiffening Through Thrombospondin-1. Circulation 2017; 136:1217-1232. [PMID: 28778947 DOI: 10.1161/circulationaha.116.026361] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 07/26/2017] [Indexed: 12/18/2022]
Abstract
BACKGROUND Arterial stiffness and wall shear stress are powerful determinants of cardiovascular health, and arterial stiffness is associated with increased cardiovascular mortality. Low and oscillatory wall shear stress, termed disturbed flow (d-flow), promotes atherosclerotic arterial remodeling, but the relationship between d-flow and arterial stiffness is not well understood. The objective of this study was to define the role of d-flow on arterial stiffening and discover the relevant signaling pathways by which d-flow stiffens arteries. METHODS D-flow was induced in the carotid arteries of young and old mice of both sexes. Arterial stiffness was quantified ex vivo with cylindrical biaxial mechanical testing and in vivo from duplex ultrasound and compared with unmanipulated carotid arteries from 80-week-old mice. Gene expression and pathway analysis was performed on endothelial cell-enriched RNA and validated by immunohistochemistry. In vitro testing of signaling pathways was performed under oscillatory and laminar wall shear stress conditions. Human arteries from regions of d-flow and stable flow were tested ex vivo to validate critical results from the animal model. RESULTS D-flow induced arterial stiffening through collagen deposition after partial carotid ligation, and the degree of stiffening was similar to that of unmanipulated carotid arteries from 80-week-old mice. Intimal gene pathway analyses identified transforming growth factor-β pathways as having a prominent role in this stiffened arterial response, but this was attributable to thrombospondin-1 (TSP-1) stimulation of profibrotic genes and not changes to transforming growth factor-β. In vitro and in vivo testing under d-flow conditions identified a possible role for TSP-1 activation of transforming growth factor-β in the upregulation of these genes. TSP-1 knockout animals had significantly less arterial stiffening in response to d-flow than wild-type carotid arteries. Human arteries exposed to d-flow had similar increases TSP-1 and collagen gene expression as seen in our model. CONCLUSIONS TSP-1 has a critical role in shear-mediated arterial stiffening that is mediated in part through TSP-1's activation of the profibrotic signaling pathways of transforming growth factor-β. Molecular targets in this pathway may lead to novel therapies to limit arterial stiffening and the progression of disease in arteries exposed to d-flow.
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Affiliation(s)
- Chan Woo Kim
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Anastassia Pokutta-Paskaleva
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Sandeep Kumar
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Lucas H Timmins
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Andrew D Morris
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Dong-Won Kang
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Sidd Dalal
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Tatiana Chadid
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Katie M Kuo
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Julia Raykin
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Haiyan Li
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Hiromi Yanagisawa
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Rudolph L Gleason
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.)
| | - Hanjoong Jo
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.).
| | - Luke P Brewster
- From Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (C.W.K., A.P.-P., S.K., D.-W.K., J.R., R.L.G., H.J., L.P.B.); Department of Microbiology, College of Medicine, Inha University, Incheon, Republic of Korea (C.W.K.); Department of Surgery, Emory University, Atlanta, GA (A.P.-P., A.D.M., T.C., K.M.K., H.L., L.P.B.); Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA (L.H.T.); Department of Bioengineering, University of Utah, Salt Lake City (L.H.T.); Mercer University School of Medicine, Macon, GA (S.D.); Life Science Center, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan (H.Y.); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta (R.L.G.); Surgical and Research Services, Atlanta VA Medical Center, Decatur, GA (L.P.B.); and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta (L.P.B.).
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17
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Razavi MS, Nelson TS, Nepiyushchikh Z, Gleason RL, Dixon JB. The relationship between lymphangion chain length and maximum pressure generation established through in vivo imaging and computational modeling. Am J Physiol Heart Circ Physiol 2017; 313:H1249-H1260. [PMID: 28778909 DOI: 10.1152/ajpheart.00003.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The intrinsic contraction of collecting lymphatic vessels serves as a pumping system to propel lymph against hydrostatic pressure gradients as it returns interstitial fluid to the venous circulation. In the present study, we proposed and validated that the maximum opposing outflow pressure along a chain of lymphangions at which flow can be achieved increases with the length of chain. Using minimally invasive near-infrared imaging to measure the effective pumping pressure at various locations in the rat tail, we demonstrated increases in pumping pressure along the length of the tail. Computational simulations based on a microstructurally motivated model of a chain of lymphangions informed from biaxial testing of isolated vessels was used to provide insights into the pumping mechanisms responsible for the pressure increases observed in vivo. These models suggest that the number of lymphangions in the chain and smooth muscle cell force generation play a significant role in determining the maximum outflow pressure, whereas the frequency of contraction has no effect. In vivo administration of nitric oxide attenuated lymphatic contraction, subsequently lowering the effective pumping pressure. Computational simulations suggest that the reduction in contractile strength of smooth muscle cells in the presence of nitric oxide can account for the reductions in outflow pressure observed along the lymphangion chain in vivo. Thus, combining modeling with multiple measurements of lymphatic pumping pressure provides a method for approximating intrinsic lymphatic muscle activity noninvasively in vivo while also providing insights into factors that determine the extent that a lymphangion chain can transport fluid against an adverse pressure gradient. NEW & NOTEWORTHY Here, we report the first minimally invasive in vivo measurements of the relationship between lymphangion chain length and lymphatic pumping pressure. We also provide the first in vivo validation of lumped parameter models of lymphangion chains previously developed through data obtained from isolated vessel testing.
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Affiliation(s)
- Mohammad S Razavi
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia
| | - Tyler S Nelson
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia
| | - Zhanna Nepiyushchikh
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia.,The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology , Atlanta, Georgia
| | - J Brandon Dixon
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia.,The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology , Atlanta, Georgia
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18
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Mebrat Y, Amogne W, Mekasha A, Gleason RL, Seifu D. Lipid Peroxidation and Altered Antioxidant Profiles with Pediatric HIV Infection and Antiretroviral Therapy in Addis Ababa, Ethiopia. J Trop Pediatr 2017; 63:196-202. [PMID: 27940963 DOI: 10.1093/tropej/fmw076] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
HIV- and highly active antiretroviral therapy (HAART)-associated elevations in oxidative stress likely play a role in incomplete immune reconstitution, opportunistic infections and non-AIDS co-morbidities. We aimed to test the hypothesis that children living with HIV exhibit elevated markers of oxidative stress and reduced antioxidant profiles and that HAART-therapy will exacerbate these differences. HIV-positive HAART-naïve (n = 50) and HAART-treated (n = 50) and HIV-negative control (n = 50) participants, 3-15 years of age, were recruited from Black Lion Hospital in Ethiopia. Serum malondialdehyde (MDA) and bilirubin were higher and vitamin C and zinc were lower in HAART-naïve and HAART-treated compared with HIV-negative subjects and higher in HAART-treated compared with HAART-naïve subjects. Uric acid was higher in HAART-naïve compared with HAART-treated and HIV-negative subjects. Differences in MDA and several antioxidants were also observed across treatment regimens. Thus, children living with HIV exhibited systemic elevations in oxidative stress and reduction in antioxidants, which are exacerbated with HAART therapy.
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Affiliation(s)
- Yiglet Mebrat
- Department of Medicine, College of Medicine and Health, Ambo University, Ambo, Ethiopia
| | - Wondwossen Amogne
- Department of Internal Medicine, College of Health Science, Addis Ababa University, Addis Ababa, Ethiopia
| | - Amha Mekasha
- Department of Pediatric and Child Health, College of Health Science, Addis Ababa University, Addis Ababa, Ethiopia
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, The Wallace H. Coulter Department of Biomedical Engineering, and The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Daniel Seifu
- Department of Biochemistry, College of Health Science, Addis Ababa University, Addis Ababa, Ethiopia
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19
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Wang R, Raykin J, Brewster LP, Gleason RL. A Novel Approach to Assess the In Situ Versus Ex Vivo Mechanical Behaviors of the Coronary Artery. J Biomech Eng 2017; 139:2588204. [PMID: 27893049 DOI: 10.1115/1.4035262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Indexed: 11/08/2022]
Abstract
Ex vivo mechanical testing has provided tremendous insight toward prediction of the in vivo mechanical behavior and local mechanical environment of the arterial wall; however, the role of perivascular support on the local mechanical behavior of arteries is not well understood. Here, we present a novel approach for quantifying the impact of the perivascular support on arterial mechanics using intravascular ultrasound (IVUS) on cadaveric porcine hearts. We performed pressure-diameter tests (n = 5) on the left anterior descending coronary arteries (LADCAs) in situ while embedded in their native perivascular environment using IVUS imaging and after removal of the perivascular support of the artery. We then performed standard cylindrical biaxial testing on these vessels ex vivo and compared the results. Removal of the perivascular support resulted in an upward shift of the pressure-diameter curve. Ex vivo testing, however, showed significantly lower circumferential compliance compared to the in situ configuration. On a second set of arteries, local axial stretch ratios were quantified (n = 5) along the length of the arteries. The average in situ axial stretch ratio was 1.28 ± 0.16; however, local axial stretch ratios showed significant variability, ranging from 1.01 to 1.70. Taken together, the data suggest that both the perivascular loading and the axial tethering have an important role in arterial mechanics. Combining nondestructive testing using IVUS with traditional ex vivo cylindrical biaxial testing yields a more comprehensive assessment of the mechanical behavior of arteries.
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Affiliation(s)
- Ruoya Wang
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
| | - Julia Raykin
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
| | - Luke P Brewster
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Woodruff Memorial Research Building, 101 Woodruff Circle, Suite 5105, Atlanta, GA 30332;Department of Surgery, Emory University School of Medicine, Atlanta, GA 30307; Surgical and Research Services, Atlanta VA Medical Center, Atlanta, GA 30033 e-mail:
| | - Rudolph L Gleason
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332;Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332;Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, IBB 2305, Atlanta, GA 30332 e-mail:
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20
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Caulk AW, Dixon JB, Gleason RL. A lumped parameter model of mechanically mediated acute and long-term adaptations of contractility and geometry in lymphatics for characterization of lymphedema. Biomech Model Mechanobiol 2016; 15:1601-1618. [PMID: 27043026 PMCID: PMC5050061 DOI: 10.1007/s10237-016-0785-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 03/23/2016] [Indexed: 12/19/2022]
Abstract
A primary purpose of the lymphatic system is to transport fluid from peripheral tissues to the central venous system in order to maintain tissue-fluid balance. Failure to perform this task results in lymphedema marked by swelling of the affected limb as well as geometric remodeling and reduced contractility of the affected lymphatic vessels. The mechanical environment has been implicated in the regulation of lymphatic contractility, but it is unknown how changes in the mechanical environment are related to loss of contractile function and remodeling of the tissue. The purpose of this paper was to introduce a new theoretical framework for acute and long-term adaptations of lymphatic vessels to changes in mechanical loading. This theoretical framework combines a simplified version of a published lumped parameter model for lymphangion function and lymph transport, a published microstructurally motivated constitutive model for the active and passive mechanical behavior of isolated rat thoracic ducts, and novel models for acute mechanically mediated vasoreactive adaptations and long-term volumetric growth to simulate changes in muscle contractility and geometry of a single isolated rat thoracic duct in response to a sustained elevation in afterload. The illustrative examples highlight the potential role of the mechanical environment in the acute maintenance of contractility and long-term geometric remodeling, presumably aimed at meeting fluid flow demands while also maintaining mechanical homeostasis. Results demonstrate that contractility may adapt in response to shear stress to meet fluid flow demands and show that pressure-induced long-term geometric remodeling may attenuate these adaptations and reduce fluid flow. The modeling framework and illustrative simulations help suggest relevant experiments that are necessary to accurately quantify and predict the acute and long-term adaptations of lymphangions to altered mechanical loading.
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Affiliation(s)
- Alexander W Caulk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA, 30332, USA
| | - J Brandon Dixon
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA, 30332, USA
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA, 30332, USA
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA, 30332, USA.
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA, 30332, USA.
- The Wallace H. Coulter Georgia Tech/Emory Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive, Atlanta, GA, 30332, USA.
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21
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Platt MO, Evans D, Keegan PM, McNamara L, Parker IK, Roberts LM, Caulk AW, Gleason RL, Seifu D, Amogne W, Penny C. Low-Cost Method to Monitor Patient Adherence to HIV Antiretroviral Therapy Using Multiplex Cathepsin Zymography. Mol Biotechnol 2016; 58:56-64. [PMID: 26589706 DOI: 10.1007/s12033-015-9903-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Monitoring patient adherence to HIV antiretroviral therapy (ART) by patient survey is inherently error prone, justifying a need for objective, biological measures affordable in low-resource settings where HIV/AIDS epidemic is highest. In preliminary studies conducted in Ethiopia and South Africa, we observed loss of cysteine cathepsin activity in peripheral blood mononuclear cells of HIV-positive patients on ART. We optimized a rapid protocol for multiplex cathepsin zymography to quantify cysteine cathepsins, and prospectively enrolled 350 HIV-positive, ART-naïve adults attending the Themba Lethu Clinic, Johannesburg, South Africa, to test if suppressed cathepsin activity could be a biomarker of ART adherence (103 patients were included in final analysis). Poor adherence was defined as detectable viral load (>400 copies/ml) or simplified medication adherence questionnaire, 4-6 months after ART initiation. 86 % of patients with undetectable viral loads after 6 months were cathepsin negative, and cathepsin-positive patients were twice as likely to have detectable viral loads (RR 2.32 95 % CI 1.26-4.29). Together, this demonstrates proof of concept that multiplex cathepsin zymography may be an inexpensive, objective method to monitor patient adherence to ART. Low cost of this electrophoresis-based assay makes it a prime candidate for implementation in resource-limited settings.
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Affiliation(s)
- Manu O Platt
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 315 Ferst Drive, IBB 1308, Atlanta, GA, 30332, USA. .,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Denise Evans
- Health Economics and Epidemiology Research Office, Department of Internal Medicine, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa
| | - Philip M Keegan
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 315 Ferst Drive, IBB 1308, Atlanta, GA, 30332, USA.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Lynne McNamara
- Clinical HIV Research Unit, Department of Internal Medicine, School of Clinical Medicine, University of the Witwatersrand, Johannesburg, South Africa
| | - Ivana K Parker
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,The George W. Woodruff School of Mechanical Engineering, Atlanta, GA, USA
| | - LaDeidra M Roberts
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 315 Ferst Drive, IBB 1308, Atlanta, GA, 30332, USA.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Alexander W Caulk
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,The George W. Woodruff School of Mechanical Engineering, Atlanta, GA, USA
| | - Rudolph L Gleason
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 315 Ferst Drive, IBB 1308, Atlanta, GA, 30332, USA.,The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,The George W. Woodruff School of Mechanical Engineering, Atlanta, GA, USA
| | - Daniel Seifu
- Department of Biochemistry, Addis Ababa University, Addis Ababa, Ethiopia
| | - Wondwossen Amogne
- Department of Internal Medicine, Addis Ababa University, Addis Ababa, Ethiopia
| | - Clement Penny
- Oncology Division, Department of Internal Medicine, University of the Witwatersrand, Johannesburg, South Africa
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22
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Gleason RL, Caulk AW, Seifu D, Rosebush JC, Shapiro AM, Schwartz MH, Eckard AR, Amogne W, Abebe W. Efavirenz and ritonavir-boosted lopinavir use exhibited elevated markers of atherosclerosis across age groups in people living with HIV in Ethiopia. J Biomech 2016; 49:2584-2592. [PMID: 27270208 DOI: 10.1016/j.jbiomech.2016.05.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 05/03/2016] [Accepted: 05/15/2016] [Indexed: 11/18/2022]
Abstract
BACKGROUND HIV patients on highly-active antiretroviral therapy (HAART) have shown elevated incidence of dyslipidemia, lipodystrophy, and markers of cardiovascular disease. Evidence is beginning to emerge that implicates efavirenz (EFV) as a potential mediator of early on-set cardiovascular disease. METHODS Pediatric and adult HIV-infected HAART-naïve, EFV-treated, nevirapine (NVP)-treated, and ritonavir-boosted lopinavir (LPV/r)-treated subjects were recruited from Black Lion Hospital in Addis Ababa, Ethiopia. Pulse wave velocity (PWV), carotid intima-media thickness (cIMT), carotid arterial stiffness, brachial artery flow-mediated dilation (FMD), body mass index, waist-to-hip circumference ratio, and skinfold thickness were measured. CD4+ cell count, fasting glucose, lipoprotein profiles and triglycerides were also determined. Results were segmented into pediatric (6-17 years of age), young adults (25-39 years old) and older adults (40-60 years old). RESULTS PWV was generally elevated in EFV- and LPV/r-treated subjects compared to NVP-treated subjects across age groups. cIMT was elevated in EFV- and LPV/r-treated compared to NVP-treated older adults and in EFV-treated compared to HAART-naïve older adults. FMD was impaired in EFV- and LPV/r-treated compared to HAART-naïve younger adults, in EFV-treated compared to NVP-treated young and older adults, and in LPV/r-treated compared to NVP-treated older adults. Differences in lipoprotein profiles and skinfold thickness with HAART regimen were observed in pediatric and young adults, but less so in older adults. CONCLUSIONS Whereas LPV/r and other protease inhibitors have long been recognized as mediators of HIV/HAART-associated atherosclerosis, this report supports the emerging evidence that EFV may also mediate cardiovascular disease in people living with HIV on HAART.
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Affiliation(s)
- Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA; The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA; Department of Biochemistry, Addis Ababa University, Addis Ababa, Ethiopia.
| | - Alexander W Caulk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Daniel Seifu
- Department of Biochemistry, Addis Ababa University, Addis Ababa, Ethiopia
| | | | - Alyssa M Shapiro
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Matthew H Schwartz
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | | | - Wondwossen Amogne
- Department of Internal Medicine, Addis Ababa University, Addis Ababa, Ethiopia
| | - Workeabeba Abebe
- Department of Pediatrics and Child Health, Addis Ababa University, Addis Ababa, Ethiopia
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23
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Caulk AW, Nepiyushchikh ZV, Shaw R, Dixon JB, Gleason RL. Quantification of the passive and active biaxial mechanical behaviour and microstructural organization of rat thoracic ducts. J R Soc Interface 2016; 12:20150280. [PMID: 26040600 DOI: 10.1098/rsif.2015.0280] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mechanical loading conditions are likely to play a key role in passive and active (contractile) behaviour of lymphatic vessels. The development of a microstructurally motivated model of lymphatic tissue is necessary for quantification of mechanically mediated maladaptive remodelling in the lymphatic vasculature. Towards this end, we performed cylindrical biaxial testing of Sprague-Dawley rat thoracic ducts (n = 6) and constitutive modelling to characterize their mechanical behaviour. Spontaneous contraction was quantified at transmural pressures of 3, 6 and 9 cmH2O. Cyclic inflation in calcium-free saline was performed at fixed axial stretches between 1.30 and 1.60, while recording pressure, outer diameter and axial force. A microstructurally motivated four-fibre family constitutive model originally proposed by Holzapfel et al. (Holzapfel et al. 2000 J. Elast. 61, 1-48. (doi:10.1023/A:1010835316564)) was used to quantify the passive mechanical response, and the model of Rachev and Hayashi was used to quantify the active (contractile) mechanical response. The average error between data and theory was 8.9 ± 0.8% for passive data and 6.6 ± 2.6% and 6.8 ± 3.4% for the systolic and basal conditions, respectively, for active data. Multi-photon microscopy was performed to quantify vessel wall thickness (32.2 ± 1.60 µm) and elastin and collagen organization for three loading conditions. Elastin exhibited structural 'fibre families' oriented nearly circumferentially and axially. Sample-to-sample variation was observed in collagen fibre distributions, which were often non-axisymmetric, suggesting material asymmetry. In closure, this paper presents a microstructurally motivated model that accurately captures the biaxial active and passive mechanical behaviour in lymphatics and offers potential for future research to identify parameters contributing to mechanically mediated disease development.
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Affiliation(s)
- Alexander W Caulk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Zhanna V Nepiyushchikh
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Ryan Shaw
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - J Brandon Dixon
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Rudolph L Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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24
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Abstract
Residual deformations strongly influence the local biomechanical environment in a number of connective tissues. The sclera is known to be biomechanically important in healthy and diseased eyes, such as in glaucoma. Here, we study the residual deformations of the sclera, as well as the adjacent choroid and retina. Using freshly harvested porcine eyes, we developed two approaches of quantifying residual deformations in the spherically shaped tissues of interest. The first consisted of punching discs from the posterior wall of the eye and quantifying the changes in the area and eccentricity of these samples. The second consisted of cutting a ring from the equatorial sclera and making stress-relieving cuts in it. Measurements of curvature were made before and after the stress-relieving cuts. Using the first approach, we observed a 42% areal contraction of the choroid, but only modest contractions of the sclera and retina. The observed contractions were asymmetric. In the second approach, we observed an opening of the scleral rings (approx. 10% decrease in curvature). We conclude that residual bending deformations are present in the sclera, which we speculate may be due to radially heterogeneous growth and remodelling of the tissue during normal development. Further, residual areal deformations present in the choroid may be due to the network of elastic fibres in this tissue and residual deformations in the constituent vascular bed. Future studies of ocular biomechanics should attempt to include effects of these residual deformations into mechanical models in order to gain a better understanding of the biomechanics of the ocular wall.
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Affiliation(s)
- Ruoya Wang
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
| | - Julia Raykin
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
| | - Rudolph L Gleason
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
| | - C Ross Ethier
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
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Kleinhenz JM, Murphy TC, Pokutta-Paskaleva AP, Gleason RL, Lyle AN, Taylor WR, Blount MA, Cheng J, Yang Q, Sutliff RL, Hart CM. Smooth Muscle-Targeted Overexpression of Peroxisome Proliferator Activated Receptor-γ Disrupts Vascular Wall Structure and Function. PLoS One 2015; 10:e0139756. [PMID: 26451838 PMCID: PMC4599849 DOI: 10.1371/journal.pone.0139756] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 09/15/2015] [Indexed: 12/15/2022] Open
Abstract
Activation of the nuclear hormone receptor, PPARγ, with pharmacological agonists promotes a contractile vascular smooth muscle cell phenotype and reduces oxidative stress and cell proliferation, particularly under pathological conditions including vascular injury, restenosis, and atherosclerosis. However, pharmacological agonists activate both PPARγ-dependent and -independent mechanisms in multiple cell types confounding efforts to clarify the precise role of PPARγ in smooth muscle cell structure and function in vivo. We, therefore, designed and characterized a mouse model with smooth muscle cell-targeted PPARγ overexpression (smPPARγOE). Our results demonstrate that smPPARγOE attenuated contractile responses in aortic rings, increased aortic compliance, caused aortic dilatation, and reduced mean arterial pressure. Molecular characterization revealed that compared to littermate control mice, aortas from smPPARγOE mice expressed lower levels of contractile proteins and increased levels of adipocyte-specific transcripts. Morphological analysis demonstrated increased lipid deposition in the vascular media and in smooth muscle of extravascular tissues. In vitro adenoviral-mediated PPARγ overexpression in human aortic smooth muscle cells similarly increased adipocyte markers and lipid uptake. The findings demonstrate that smooth muscle PPARγ overexpression disrupts vascular wall structure and function, emphasizing that balanced PPARγ activity is essential for vascular smooth muscle homeostasis.
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Affiliation(s)
- Jennifer M. Kleinhenz
- Atlanta VA Medical Center, Decatur, GA, United States of America
- Emory University, Atlanta, GA, United States of America
| | - Tamara C. Murphy
- Atlanta VA Medical Center, Decatur, GA, United States of America
- Emory University, Atlanta, GA, United States of America
| | | | | | | | - W. Robert Taylor
- Atlanta VA Medical Center, Decatur, GA, United States of America
- Emory University, Atlanta, GA, United States of America
- Georgia Institute of Technology, Atlanta, GA, United States of America
| | | | - Juan Cheng
- Emory University, Atlanta, GA, United States of America
| | - Qinglin Yang
- University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Roy L. Sutliff
- Atlanta VA Medical Center, Decatur, GA, United States of America
- Emory University, Atlanta, GA, United States of America
| | - C. Michael Hart
- Atlanta VA Medical Center, Decatur, GA, United States of America
- Emory University, Atlanta, GA, United States of America
- * E-mail:
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Gleason RL, Caulk AW, Seifu D, Parker I, Vidakovic B, Getenet H, Assefa G, Amogne W. Current Efavirenz (EFV) or ritonavir-boosted lopinavir (LPV/r) use correlates with elevate markers of atherosclerosis in HIV-infected subjects in Addis Ababa, Ethiopia. PLoS One 2015; 10:e0117125. [PMID: 25915208 PMCID: PMC4411122 DOI: 10.1371/journal.pone.0117125] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 12/18/2014] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND HIV patients on antiretroviral therapy have shown elevated incidence of dyslipidemia, lipodystrophy, and cardiovascular disease (CVD). Most studies, however, focus on cohorts from developed countries, with less data available for these co-morbidities in Ethiopia and sub-Saharan Africa. METHODS Adult HIV-negative (n = 36), treatment naïve (n = 51), efavirenz (EFV)-treated (n = 91), nevirapine (NVP)-treated (n = 95), or ritonavir-boosted lopinavir (LPV/r)-treated (n=44) subjects were recruited from Black Lion Hospital in Addis Ababa, Ethiopia. Aortic pressure, augmentation pressure, and pulse wave velocity (PWV) were measured via applanation tonometry and carotid intima-media thickness (cIMT) and carotid arterial stiffness, and brachial artery flow-mediated dilation (FMD) were measured via non-invasive ultrasound. Body mass index, waist-to-hip circumference ratio (WHR), skinfold thickness, and self-reported fat redistribution were used to quantify lipodystrophy. CD4+ cell count, plasma HIV RNA levels, fasting glucose, total-, HDL-, and LDL-cholesterol, triglycerides, hsCRP, sVCAM-1, sICAM-1, leptin and complete blood count were measured. RESULTS PWV and normalized cIMT were elevate and FMD impaired in EFV- and LPV/r-treated subjects compared to NVP-treated subjects; normalized cIMT was also elevated and FMD impaired in the EFV- and LPV/r-treated subjects compared to treatment-naïve subjects. cIMT was not statistically different across groups. Treated subjects exhibited elevated markers of dyslipidemia, inflammation, and lipodystrophy. PWV was associated with age, current EFV and LPV/r used, heart rate, blood pressure, triglycerides, LDL, and hsCRP, FMD with age, HIV duration, WHR, and glucose, and cIMT with age, current EFV use, skinfold thickness, and blood pressure. CONCLUSIONS Current EFV- or LPV/r-treatment, but not NVP-treatment, correlated with elevated markers of atherosclerosis, which may involve mechanisms distinct from traditional risk factors.
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Affiliation(s)
- Rudolph L. Gleason
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Alexander W. Caulk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Daniel Seifu
- Department of Biochemistry, Medical Faculty, Addis Ababa University, Addis Ababa, Ethiopia
| | - Ivana Parker
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Brani Vidakovic
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Helena Getenet
- Department of Internal Medicine, Medical Faculty, Addis Ababa University, Addis Ababa, Ethiopia
| | - Getachew Assefa
- Department of Radiology, Medical Faculty, Addis Ababa University, Addis Ababa, Ethiopia
| | - Wondwossen Amogne
- Department of Internal Medicine, Medical Faculty, Addis Ababa University, Addis Ababa, Ethiopia
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Abstract
Quantifying arterial residual deformations is critical for understanding the stresses and strains within the arterial wall during physiological and pathophysiological conditions. This study presents novel findings on residual shear deformations in the left anterior descending coronary artery. Residual shear deformations are most evident when thin, long axial strips are cut from the artery. These strips deform into helical configurations when placed in isotonic solution. A residual shear angle is introduced as a parameter to quantify the residual shear deformations. Furthermore, a stress analysis is performed to study the effects of residual shear deformations on the intramural shear stress distribution of an artery subjected to pressure, axial stretch, and torsion using numerical simulation. The results from the stress analyses suggest that residual shear deformations can significantly modulate the intramural shear stress across the arterial wall.
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Wang R, Raykin J, Li H, Gleason RL, Brewster LP. Differential mechanical response and microstructural organization between non-human primate femoral and carotid arteries. Biomech Model Mechanobiol 2014; 13:1041-51. [PMID: 24532266 DOI: 10.1007/s10237-014-0553-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 01/08/2014] [Indexed: 01/13/2023]
Abstract
Unique anatomic locations and physiologic functions predispose different arteries to varying mechanical responses and pathologies. However, the underlying causes of these mechanical differences are not well understood. The objective of this study was to first identify structural differences in the arterial matrix that would account for the mechanical differences between healthy femoral and carotid arteries and second to utilize these structural observations to perform a microstructurally motivated constitutive analysis. Femoral and carotid arteries were subjected to cylindrical biaxial loading and their microstructure was quantified using two-photon microscopy. The femoral arteries were found to be less compliant than the carotid arteries at physiologic loads, consistent with previous studies, despite similar extracellular compositions of collagen and elastin ([Formula: see text]). The femoral arteries exhibited significantly less circumferential dispersion of collagen fibers ([Formula: see text]), despite a similar mean fiber alignment direction as the carotid arteries. Elastin transmural distribution, in vivo axial stretch, and opening angles were also found to be distinctly different between the arteries. Lastly, we modeled the arteries' mechanical behaviors using a microstructural-based, distributed collagen fiber constitutive model. With this approach, the material parameters of the model were solved using the experimental microstructural observations. The findings of this study support an important role for microstructural organization in arterial stiffness.
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Affiliation(s)
- Ruoya Wang
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA,
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Wang R, Brewster LP, Gleason RL. In-situ characterization of the uncrimping process of arterial collagen fibers using two-photon confocal microscopy and digital image correlation. J Biomech 2013; 46:2726-9. [PMID: 24050510 DOI: 10.1016/j.jbiomech.2013.08.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 08/10/2013] [Accepted: 08/12/2013] [Indexed: 11/24/2022]
Abstract
Uncrimping of collagen fibers in the arterial wall is an integral process in regulating the macro-level mechanical response of arteries. Uncrimping of collagen fibers leads to a gradual, but significant strain-stiffening response of the artery at physiological pressures and prevents overdistention at elevated pressures. In this study, we imaged adventitial collagen fibers from fresh primate arteries using two-photon excitation microscopy while subjecting the arteries to physiological inflation pressures and axial stretches. The imaging focal plane was fixed at a constant radial location in the adventitial wall by adjusting the focal distance as the arteries inflated, allowing for the continuously monitoring of the uncrimping process of a single region of collagen fibers. Digital image correlation was then applied to the sequential images to assess and correlate the local displacements to manual traces of selected reference fibers and their engagements. We found that the collagen fibers of interest became fully engaged at a luminal pressure of 20mmHg, this was then followed by rotation of these fibers as the bulk artery continued to dilate. This technique helps to further the understanding of the uncrimping process of collagen fibers under physiological loads, which can aid in the development of more accurate microstructural constitutive models.
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Affiliation(s)
- Ruoya Wang
- George W. Woodruff School of Mechanical Engineering, USA; Department of Surgery, Division of Vascular Surgery, Emory University School of Medicine, Atlanta, GA, USA.
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Sutliff RL, Hilenski LL, Amanso AM, Parastatidis I, Dikalova AE, Hansen L, Datla SR, Long JS, El-Ali AM, Joseph G, Gleason RL, Taylor WR, Hart CM, Griendling KK, Lassègue B. Polymerase delta interacting protein 2 sustains vascular structure and function. Arterioscler Thromb Vasc Biol 2013; 33:2154-61. [PMID: 23825363 DOI: 10.1161/atvbaha.113.301913] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE On the basis of previous evidence that polymerase delta interacting protein 2 (Poldip2) increases reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (Nox4) activity in vascular smooth muscle cells, we hypothesized that in vivo knockdown of Poldip2 would inhibit reactive oxygen species production and alter vascular function. APPROACH AND RESULTS Because homozygous Poldip2 deletion is lethal, Poldip2(+/-) mice were used. Poldip2 mRNA and protein levels were reduced by ≈50% in Poldip2(+/-) aorta, with no change in p22phox, Nox1, Nox2, and Nox4 mRNAs. NADPH oxidase activity was also inhibited in Poldip2(+/-) tissue. Isolated aortas from Poldip2(+/-) mice demonstrated impaired phenylephrine and potassium chloride-induced contractions, increased stiffness, and reduced compliance associated with disruption of elastic lamellae and excessive extracellular matrix deposition. Collagen I secretion was elevated in cultured vascular smooth muscle cells from Poldip2(+/-) mice and restored by H2O2 supplementation, suggesting that this novel function of Poldip2 is mediated by reactive oxygen species. Furthermore, Poldip2(+/-) mice were protected against aortic dilatation in a model of experimental aneurysm, an effect consistent with increased collagen secretion. CONCLUSIONS Poldip2 knockdown reduces H2O2 production in vivo, leading to increases in extracellular matrix, greater vascular stiffness, and impaired agonist-mediated contraction. Thus, unaltered expression of Poldip2 is necessary for vascular integrity and function.
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Affiliation(s)
- Roy L Sutliff
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Atlanta Veterans Affairs Medical Center and Emory University School of Medicine, Decatur, GA, USA
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31
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Hansen L, Parker I, Roberts LM, Sutliff RL, Platt MO, Gleason RL. Azidothymidine (AZT) leads to arterial stiffening and intima-media thickening in mice. J Biomech 2013; 46:1540-7. [PMID: 23623314 PMCID: PMC4518204 DOI: 10.1016/j.jbiomech.2013.03.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 03/15/2013] [Accepted: 03/16/2013] [Indexed: 02/07/2023]
Abstract
HIV positive patients on highly active antiretroviral therapy (HAART) have shown elevated incidence of a number of non-AIDS defining co-morbidities, including cardiovascular disease. Given that HAART regimens contain a combination of at least three drugs, that disease management often requires adjustment of these regimens, and HIV, independent of HAART, also plays a role in development of co-morbidities, determining the role of specific HAART drugs and HIV infection itself from clinical data remains challenging. To characterize specific mediators and underlying mechanisms of disease, in vitro and in vivo animal models are required, in parallel with clinical data. Given its low cost azidothymidine (AZT) contributes to the backbone of a large proportion of HAART treated patients in the developing world where much of the global burden of HIV resides. The goal of this study was to test the hypothesis that AZT can lead to proatherogenic changes including the subclinical markers of arterial stiffening and intima-media thickening in mice. AZT (100mg/kg) or vehicle was administered to wild-type FVB/N mice via oral gavage for 35 days. Cylindrical biaxial biomechanical tests on the common carotid arteries and suprarenal aortas exhibited arterial stiffening in AZT mice compared to controls. Multiphoton microscopy and histology demonstrated that AZT led to increased intima-media thickness. These data correlated with decreased elastin content and increased protease activity as measured by cathepsin zymography; no differences were observed in collagen content or organization, in vivo axial stretch, or opening angle. Thus, this study suggests the drug AZT has significant effects on the development of subclinical markers of atherosclerosis.
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Affiliation(s)
- Laura Hansen
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Ivana Parker
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - LaDeidra Monet Roberts
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Roy L. Sutliff
- Department of Medicine, Emory University, Atlanta VAMC, Atlanta, GA, USA
| | - Manu O. Platt
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Rudolph L. Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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32
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Hansen L, Parker I, Sutliff RL, Platt MO, Gleason RL. Endothelial dysfunction, arterial stiffening, and intima-media thickening in large arteries from HIV-1 transgenic mice. Ann Biomed Eng 2013; 41:682-93. [PMID: 23180031 PMCID: PMC4487412 DOI: 10.1007/s10439-012-0702-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 11/09/2012] [Indexed: 11/25/2022]
Abstract
HIV patients on highly active antiretroviral therapy (HAART) exhibit elevated incidence of cardiovascular disease (CVD), including a higher risk of myocardial infarction and prevalence of atherosclerotic lesions, as well as increases in markers of subclinical atherosclerosis including increased carotid artery intima-media thickness (c-IMT), increased arterial stiffness, and impaired flow-mediated dilation. Both HAART and HIV-infection are independent risk factors for atherosclerosis and myocardial infarction. Studies implicate the HIV proteins tat, gp120, vpu, and nef in early on-set atherosclerosis. The objective of this study was to quantify the role of expression of HIV-1 proteins on the vascular function, biomechanics, and geometry of common carotid arteries and aortas. This study employed NL4-3Δ gag/pol transgenic mice (HIV-Tg), which contain the genetic sequence for the HIV-1 proteins env, tat, nef, rev, vif, vpr, and vpu but lacks the gag and pol genes and reports that HIV-Tg mice have impaired aortic endothelial function, increased c-IMT, and increased arterial stiffness. Further, HIV-Tg arteries show decreased elastin content, increased cathepsin K and cathepsin S activity, and increased mechanical residual stress. Thus, mice that express HIV proteins exhibit pre-clinical markers of atherosclerosis and these markers correlate with changes in markers of vascular remodeling. These findings are consistent with the hypothesis that HIV-proteins, independent of HAART treatment or HIV infection, could play a role in of the development of CVD.
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Affiliation(s)
- Laura Hansen
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA
| | - Ivana Parker
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA
| | - Roy L. Sutliff
- Department Medicine, Emory University/Atlanta VAMC, Atlanta, GA
| | - Manu O. Platt
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA
| | - Rudolph L. Gleason
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA
- The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA
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Wan W, Gleason RL. Dysfunction in elastic fiber formation in fibulin-5 null mice abrogates the evolution in mechanical response of carotid arteries during maturation. Am J Physiol Heart Circ Physiol 2012; 304:H674-86. [PMID: 23241326 DOI: 10.1152/ajpheart.00459.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Elastin fragmentation is a common characteristic of vascular diseases, such as abdominal aortic aneurysms, peripheral arterial disease, and aortic dissection. Examining growth and remodeling in the presence of dysfunctional elastic fibers provides insight into the adaptive or maladaptive changes that tissues undergo in compensating for structural deficiencies. This study used the maturation of fibulin-5 knockout (KO) and wild-type mice to study the effects of fragmented elastic fibers on the growth and remodeling of carotid arteries. The microstructural content and organization and the biaxial mechanical behavior of common carotid arteries were measured, and parameter estimation performed from KO and WT mice aged 3, 4, 8, and 13 wk. Gross measurements and biaxial tests revealed significant differences in pressure-diameter behavior, in vivo axial stretch, opening angle, compliance, and wall stresses during maturation of wild-type arteries, but little change in these values in KO mice. Multiphoton microscopy used to image collagen fibers across the vessel wall in pressurized and stretched arteries suggests that there is little variation in fiber angles between different ages. Parameter estimation revealed significant differences in material parameters between genotypes and age groups. This study suggests that neonatal formation and cross-linking of functional elastic fibers, followed by increases in artery size due to growth with little remodeling of the elastic fibers, endow arteries with large distensibility and contribute to the evolution of mechanical behavior of arteries during maturation. Dysfunction in neonatal formation of elastic fibers abrogates many of the changes in mechanical response that take place during the maturation.
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Affiliation(s)
- William Wan
- The George W. Woodruff School of Mechanical Engineering, The Wallace H. Coulter Department of Biomedical Engineering, The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
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Wan W, Dixon JB, Gleason RL. Constitutive modeling of mouse carotid arteries using experimentally measured microstructural parameters. Biophys J 2012; 102:2916-25. [PMID: 22735542 DOI: 10.1016/j.bpj.2012.04.035] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 04/13/2012] [Accepted: 04/24/2012] [Indexed: 10/28/2022] Open
Abstract
Changes in the local mechanical environment and tissue mechanical properties affect the biological activity of cells and play a key role in a variety of diseases, such as cancer, arthritis, nephropathy, and cardiovascular disease. Constitutive relations have long been used to predict the local mechanical environment within biological tissues and to investigate the relationship between biological responses and mechanical stimuli. Recent constitutive relations for soft tissues consider both material and structural properties by incorporating parameters that describe microstructural organization, such as fiber distributions, fiber angles, fiber crimping, and constituent volume fractions. The recently developed technique of imaging the microstructure of a single artery as it undergoes multiple deformations provides quantitative structural data that can reduce the number of estimated parameters by using parameters that are truly experimentally intractable. Here, we employed nonlinear multiphoton microscopy to quantify collagen fiber organization in mouse carotid arteries and incorporated measured fiber distribution data into structurally motivated constitutive relations. Microscopy results demonstrate that collagen fibers deform in an affine manner over physiologically relevant deformations. The incorporation of measured fiber angle distributions into constitutive relations improves the model's predictive accuracy and does not significantly reduce the goodness of fit. The use of measured structural parameters rather than estimated structural parameters promises to improve the predictive capabilities of the local mechanical environment, and to extend the utility of intravital imaging methods for estimating the mechanical behavior of tissues using in situ structural information.
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Affiliation(s)
- William Wan
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
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Maiellaro-Rafferty K, Weiss D, Joseph G, Wan W, Gleason RL, Taylor WR. Catalase overexpression in aortic smooth muscle prevents pathological mechanical changes underlying abdominal aortic aneurysm formation. Am J Physiol Heart Circ Physiol 2011; 301:H355-62. [PMID: 21551275 DOI: 10.1152/ajpheart.00040.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The causality of the associations between cellular and mechanical mechanisms of abdominal aortic aneurysm (AAA) formation has not been completely defined. Because reactive oxygen species are established mediators of AAA growth and remodeling, our objective was to investigate oxidative stress-induced alterations in aortic biomechanics and microstructure during subclinical AAA development. We investigated the mechanisms of AAA in an angiotensin II (ANG II) infusion model of AAA in apolipoprotein E-deficient (apoE(-/-)) mice that overexpress catalase in vascular smooth muscle cells (apoE(-/-)xTg(SMC-Cat)). At baseline, aortas from apoE(-/-)xTg(SMC-Cat) exhibited increased stiffness and the microstructure was characterized by 50% more collagen content and less elastin fragmentation. ANG II treatment for 7 days in apoE(-/-) mice altered the transmural distribution of suprarenal aortic circumferential strain (quantified by opening angle, which increased from 130 ± 1° at baseline to 198 ± 8° after 7 days of ANG II treatment) without obvious changes in the aortic microstructure. No differences in aortic mechanical behavior or suprarenal opening angle were observed in apoE(-/-)xTg(SMC-Cat) after 7 days of ANG II treatment. These data suggest that at the earliest stages of AAA development H(2)O(2) is functionally important and is involved in the control of local variations in remodeling across the vessel wall. They further suggest that reduced elastin integrity at baseline may predispose the abdominal aorta to aneurysmal mechanical remodeling.
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Affiliation(s)
- Kathryn Maiellaro-Rafferty
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University Atlanta, GA, USA
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Wan W, Yanagisawa H, Gleason RL. Biomechanical and microstructural properties of common carotid arteries from fibulin-5 null mice. Ann Biomed Eng 2010; 38:3605-17. [PMID: 20614245 DOI: 10.1007/s10439-010-0114-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 06/22/2010] [Indexed: 01/15/2023]
Abstract
Alteration in the mechanical properties of arteries occurs with aging and disease, and arterial stiffening is a key risk factor for subsequent cardiovascular events. Arterial stiffening is associated with the loss of functional elastic fibers and increased collagen content in the wall of large arteries. Arterial mechanical properties are controlled largely by the turnover and reorganization of key structural proteins and cells, a process termed growth and remodeling. Fibulin-5 (fbln5) is a microfibrillar protein that binds tropoelastin, interacts with integrins, and localizes to elastin fibers; tropoelastin and microfibrillar proteins constitute functional elastic fibers. We performed biaxial mechanical testing and confocal imaging of common carotid arteries (CCAs) from fibulin-5 null mice (fbln5 ⁻(/)⁻) and littermate controls (fbln5 (+/+)) to characterize the mechanical behavior and microstructural content of these arteries; mechanical testing data were fit to a four-fiber family constitutive model. We found that CCAs from fbln5 ⁻(/)⁻ mice exhibited lower in vivo axial stretch and lower in vivo stresses while maintaining a similar compliance over physiological pressures compared to littermate controls. Specifically, for fbln5 ⁻(/)⁻ the axial stretch λ = 1.41 ± 0.07, the circumferential stress σ(θ) = 101 ± 32 kPa, and the axial stress σ ( z ) = 74 ± 28 kPa; for fbln5 (+/+) λ = 1.64 ± 0.03, σ(θ) = 194 ± 38 kPa, and σ(z) = 159 ± 29 kPa. Structurally, CCAs from fbln5 ⁻(/)⁻ mice lack distinct functional elastic fibers defined by the lamellar structure of alternating layers of smooth muscle cells and elastin sheets. These data suggest that structural differences in fbln5 ⁻(/)⁻ arteries correlate with significant differences in mechanical properties. Despite these significant differences fbln5 ⁻(/)⁻ CCAs exhibited nearly normal levels of cyclic strain over the cardiac cycle.
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Affiliation(s)
- William Wan
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, 30332, USA
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37
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Zaucha MT, Gauvin R, Auger FA, Germain L, Gleason RL. Biaxial biomechanical properties of self-assembly tissue-engineered blood vessels. J R Soc Interface 2010; 8:244-56. [PMID: 20554564 DOI: 10.1098/rsif.2010.0228] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Along with insights into the potential for graft success, knowledge of biomechanical properties of small diameter tissue-engineered blood vessel (TEBV) will enable designers to tailor the vessels' mechanical response to closer resemble that of native tissue. Composed of two layers that closely mimic the native media and adventitia, a tissue-engineered vascular adventitia (TEVA) is wrapped around a tissue-engineered vascular media (TEVM) to produce a self-assembled tissue-engineered media/adventia (TEVMA). The current study was undertaken to characterize the biaxial biomechanical properties of TEVM, TEVA and TEVMA under physiological pressures as well as characterize the stress-free reference configuration. It was shown that the TEVA had the greatest compliance over the physiological loading range while the TEVM had the lowest compliance. As expected, compliance of the SA-TEBV fell in between with an average compliance of 2.73 MPa(-1). Data were used to identify material parameters for a microstructurally motivated constitutive model. Identified material parameters for the TEVA and TEVM provided a good fit to experimental data with an average coefficient of determination of 0.918 and 0.868, respectively. These material parameters were used to develop a two-layer predictive model for the response of a TEVMA which fit well with experimental data.
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Affiliation(s)
- Michael T Zaucha
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, , 801 Ferst Drive, Atlanta, GA 30332-0405, USA
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Rachev A, Gleason RL. Theoretical study on the effects of pressure-induced remodeling on geometry and mechanical non-homogeneity of conduit arteries. Biomech Model Mechanobiol 2010; 10:79-93. [PMID: 20473704 DOI: 10.1007/s10237-010-0219-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 04/19/2010] [Indexed: 11/28/2022]
Abstract
A structure-based mathematical model for the remodeling of arteries in response to sustained hypertension is proposed. The model is based on the concepts of volumetric growth and constitutive modeling of the arterial tissue within the framework of the constrained mixture theory. The major novel result of this study is that remodeling is associated with a local change in the mass fractions of the wall constituents that ultimately leads to mechanical non-homogeneity of the arterial wall. In the new homeostatic state that develops after a sustained increase in arterial pressure, the mass fraction of elastin decreases from the intimal side to the adventitial side of arteries, while the collagen fraction manifests an opposite trend. The results obtained are supported by some experimental observations reported in the literature.
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Affiliation(s)
- Alexander Rachev
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA.
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Zaucha MT, Raykin J, Wan W, Gauvin R, Auger FA, Germain L, Michaels TE, Gleason RL. A novel cylindrical biaxial computer-controlled bioreactor and biomechanical testing device for vascular tissue engineering. Tissue Eng Part A 2010; 15:3331-40. [PMID: 19385725 DOI: 10.1089/ten.tea.2008.0369] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
It is becoming evident that tissue-engineered constructs adapt to altered mechanical loading, and that specific combinations of multidirectional loads appear to have a synergistic effect on the remodeling. However, most studies of mechanical stimulation of engineered vascular tissue engineering employ only uniaxial stimulation. Here we present a novel computer-controlled bioreactor and biomechanical testing device designed to precisely and simultaneously control mean and cyclic values of transmural pressure (at rates up to 1 Hz and ranges of 40 mmHg), luminal flow rate, and axial length (or load) applied to gel-derived, scaffold-derived, and self-assembly-derived tissue-engineered blood vessels during culture, while monitoring vessel geometry with a resolution of 6.6 mum. Intermittent monitoring of the extracellular matrix and cells is accomplished on live tissues using multi-photon confocal microscopy under unloaded and loaded conditions at multiple time-points in culture (on the same vessel) to quantify changes in cell and extracellular matrix content and organization. This same device is capable of performing intermittent cylindrical biaxial biomechanical testing at multiple time-points in culture (on the same vessel) to quantify changes in the mechanical behavior during culture. Here we demonstrate the capabilities of this new device on self-assembly-derived and collagen-gel-derived tissue-engineered blood vessels.
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Affiliation(s)
- Michael T Zaucha
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
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40
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Wang R, Gleason RL. A mechanical analysis of conduit arteries accounting for longitudinal residual strains. Ann Biomed Eng 2010; 38:1377-87. [PMID: 20087772 DOI: 10.1007/s10439-010-9916-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 01/05/2010] [Indexed: 10/19/2022]
Abstract
Identification of an appropriate stress-free reference configuration is critically important in providing a reasonable prediction of the intramural stress distribution when performing biomechanical analyses on arteries. The stress-free state is commonly approximated as a radially cut ring that typically opens into a nearly circular sector, relieving much of the circumferential residual strains that exist in the traction-free configuration. An opening angle is often used to characterize this sector. In this study, we first present experimental results showing significant residual deformations in the longitudinal direction of two commonly studied arteries in the pig: the common carotid artery and the left anterior descending coronary artery. We concluded that a radially cut ring cannot completely describe the stress-free state of the arteries. Instead, we propose the use of a longitudinal opening angle, in conjunction with the traditional circumferential opening angle, to experimentally quantify the stress-free state of an artery. Secondly, we propose a new kinematic model to account for the addition of longitudinal residual strains through employing the longitudinal opening angle and performed a stress analysis. We found that with the inclusion of longitudinal residual strains in the stress analysis, the predicted circumferential stress gradient was decreased by 3-fold and the predicted longitudinal stress gradient was increased by 5.7-fold. Thus, inclusion of longitudinal residual strains has a significant effect on the predicted stress distribution in arteries.
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Affiliation(s)
- Ruoya Wang
- George W Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA
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41
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Raykin J, Rachev AI, Gleason RL. A phenomenological model for mechanically mediated growth, remodeling, damage, and plasticity of gel-derived tissue engineered blood vessels. J Biomech Eng 2010; 131:101016. [PMID: 19831486 DOI: 10.1115/1.4000124] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mechanical stimulation has been shown to dramatically improve mechanical and functional properties of gel-derived tissue engineered blood vessels (TEBVs). Adjusting factors such as cell source, type of extracellular matrix, cross-linking, magnitude, frequency, and time course of mechanical stimuli (among many other factors) make interpretation of experimental results challenging. Interpretation of data from such multifactor experiments requires modeling. We present a modeling framework and simulations for mechanically mediated growth, remodeling, plasticity, and damage of gel-derived TEBVs that merge ideas from classical plasticity, volumetric growth, and continuum damage mechanics. Our results are compared with published data and suggest that this model framework can predict the evolution of geometry and material behavior under common experimental loading scenarios.
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Affiliation(s)
- Julia Raykin
- Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, 30332, USA
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42
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Hansen L, Wan W, Gleason RL. Microstructurally motivated constitutive modeling of mouse arteries cultured under altered axial stretch. J Biomech Eng 2010; 131:101015. [PMID: 19831485 DOI: 10.1115/1.3207013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Good predictions of the local mechanical environment of the tissue with known geometry and applied loads are fundamental to quantifying the biological response of tissues to mechanical stimuli. Whereas mean stresses in cylindrical sections of blood vessels may be calculated directly from measured loads and vessel geometry (e.g., Laplace's law), predicting how these stresses are distributed across the wall requires knowledge of the constitutive behavior of the tissue. Previously, we reported biaxial biomechanical data for mouse carotid arteries before and after exposure to altered axial extension in organ culture. Here we considered phenomenological and microstructurally motivated constitutive models and identified material parameters for each via nonlinear regression. Specifically, we considered the model of Chuong and Fung, a four fiber-family model, and several new variants of a rule-of-mixtures model; in the latter, we modeled the artery as a mixture of collagen, elastin, muscle, and water. We found that the four fiber-family model fitted data significantly better than the model of Chuong and Fung. When identifying parameters for the rule-of-mixtures models, we imposed penalties that required each constituent to be structurally significant; e.g., elastin contributing significantly to the overall response over low loads and collagen dominating the response over high loads. Such constraints ascribe additional microstructural "meaning" to the constitutive model. Although imposing such penalties necessarily reduces the goodness of fit of model predictions to experimental data compared to regression without such penalties, the modest reduction in the goodness of fit observed in our results was off-set by the improved structural interpretation such models provide. Such microstructurally motivated models will be useful in characterizing vascular growth and remodeling in terms of the evolution of microstructural metrics that may be quantified experimentally.
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Affiliation(s)
- Laura Hansen
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, 30332, USA
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Wan W, Hansen L, Gleason RL. A 3-D constrained mixture model for mechanically mediated vascular growth and remodeling. Biomech Model Mechanobiol 2009; 9:403-19. [PMID: 20039091 DOI: 10.1007/s10237-009-0184-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 12/08/2009] [Indexed: 11/29/2022]
Abstract
In contrast to the widely applied approach to model soft tissue remodeling employing the concept of volumetric growth, microstructurally motivated models are capable of capturing many of the underlying mechanisms of growth and remodeling; i.e., the production, removal, and remodeling of individual constituents at different rates and to different extents. A 3-dimensional constrained mixture computational framework has been developed for vascular growth and remodeling, considering new, microstructurally motivated kinematics and constitutive equations and new stress and muscle activation mediated evolution equations. Our computational results for alterations in flow and pressure, using reasonable physiological values for rates of constituent growth and turnover, concur with findings in the literature. For example, for flow-induced remodeling, our simulations predict that, although the wall shear stress is restored completely, the circumferential stress is not restored employing realistic physiological rate parameters. Also, our simulations predict different levels of thickening on inner versus outer wall locations, as shown in numerous reports of pressure-induced remodeling. Whereas the simulations are meant to be illustrative, they serve to highlight the experimental data currently lacking to fully quantify mechanically mediated adaptations in the vasculature.
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Affiliation(s)
- William Wan
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, 30332, USA
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Humphrey JD, Eberth JF, Dye WW, Gleason RL. Fundamental role of axial stress in compensatory adaptations by arteries. J Biomech 2008; 42:1-8. [PMID: 19070860 DOI: 10.1016/j.jbiomech.2008.11.011] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2008] [Revised: 11/11/2008] [Accepted: 11/13/2008] [Indexed: 10/21/2022]
Abstract
Arteries exhibit a remarkable ability to adapt to diverse genetic defects and sustained alterations in mechanical loading. For example, changes in blood flow induced wall shear stress tend to control arterial caliber and changes in blood pressure induced circumferential wall stress tend to control wall thickness. We submit, however, that the axial component of wall stress plays a similarly fundamental role in controlling arterial geometry, structure, and function, that is, compensatory adaptations. This observation comes from a review of findings reported in the literature and a comparison of four recent studies from our laboratory that quantified changes in the biaxial mechanical properties of mouse carotid arteries in cases of altered cell-matrix interactions, extracellular matrix composition, blood pressure, or axial extension. There is, therefore, a pressing need to include the fundamental role of axial wall stress in conceptual and theoretical models of arterial growth and remodeling and, consequently, there is a need for increased attention to evolving biaxial mechanical properties in cases of altered genetics and mechanical stimuli.
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Affiliation(s)
- J D Humphrey
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843-3120, USA.
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45
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Gleason RL, Dye WW, Wilson E, Humphrey JD. Quantification of the mechanical behavior of carotid arteries from wild-type, dystrophin-deficient, and sarcoglycan-delta knockout mice. J Biomech 2008; 41:3213-8. [PMID: 18842267 DOI: 10.1016/j.jbiomech.2008.08.012] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 05/21/2008] [Accepted: 08/09/2008] [Indexed: 11/30/2022]
Abstract
As patients with muscular dystrophy live longer because of improved clinical care, they will become increasingly susceptible to many of the cardiovascular diseases that affect the general population. There is, therefore, a pressing need to better understand both the biology and the mechanics of the arterial wall in these patients. In this paper, we use nonlinear constitutive relations to model, for the first time, the biaxial mechanical behavior of carotid arteries from two common mouse models of muscular dystrophy (dystrophin-deficient and sarcoglycan-delta null) and wild-type controls. It is shown that a structurally motivated four-fiber family stress-strain relation describes the passive behavior of all three genotypes better than does a commonly used phenomenological exponential model, and that a Rachev-Hayashi model describes the mechanical contribution of smooth muscle contraction under basal tone. Because structurally motivated constitutive relations can be extended easily to model adaptations to altered hemodynamics, results from this study represent an important step toward the ultimate goal of understanding better the mechanobiology and pathophysiology of arteries in muscular dystrophy.
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Affiliation(s)
- Rudolph L Gleason
- George W. Woodruff School of Mechanical Engineering, Wallace H. Coulter Department of Biomedical Engineering, and The Petite Institute for Biomedical Engineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.
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Abstract
Muscular dystrophy is characterized by skeletal muscle weakness and wasting, but little is known about possible alterations to the vasculature. Many muscular dystrophies are caused by a defective dystrophin-glycoprotein complex (DGC), which plays an important role in mechanotransduction and maintenance of structural integrity in muscle cells. The DGC is a group of membrane-associated proteins, including dystrophin and sarcoglycan-delta, that helps connect the cytoskeleton of muscle cells to the extracellular matrix. In this paper, mice lacking genes encoding dystrophin (mdx) or sarcoglycan-delta (sgcd-/-) were studied to detect possible alterations to vascular wall mechanics. Pressure-diameter and axial force-length tests were performed on common carotid arteries from mdx, sgcd-/-, and wild-type mice in active (basal) and passive smooth muscle states, and functional responses to three vasoactive compounds were determined at constant pressure and length. Apparent biomechanical differences included the following: mdx and sgcd-/- arteries had decreased distensibilities in pressure-diameter tests, with mdx arteries exhibiting elevated circumferential stresses, and mdx and sgcd-/- arteries generated elevated axial loads and stresses in axial force-length tests. Interestingly, however, mdx and sgcd-/- arteries also had significantly lower in vivo axial stretches than did the wild type. Accounting for this possible adaptation largely eliminated the apparent differences in circumferential and axial stiffness, thus suggesting that loss of DGC proteins may induce adaptive biomechanical changes that can maintain overall wall mechanics in response to normal loads. Nevertheless, there remains a need to understand better possible vascular adaptations in response to sustained altered loads in patients with muscular dystrophy.
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Affiliation(s)
- W W Dye
- Dept. of Biomedical Engineering, M. E. DeBakey Institute, Texas A&M University, College Station, TX 77843-3120, USA
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47
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Gleason RL, Wilson E, Humphrey JD. Biaxial biomechanical adaptations of mouse carotid arteries cultured at altered axial extension. J Biomech 2006; 40:766-76. [PMID: 16750537 DOI: 10.1016/j.jbiomech.2006.03.018] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 03/29/2006] [Indexed: 11/28/2022]
Abstract
Many have studied the roles of altered blood flow and pressure on adaptive responses of blood vessels, but few have studied the role of altered axial loads. We exposed common carotid arteries from wild-type mice to low, medium, or high axial extensions while maintaining the same pressure and luminal flow rate for two days in culture, and studied adaptations in vessel geometry, in vitro loads, and stresses while collecting biaxial biomechanical (pressure-diameter and axial force-length) data on Day 0 (initial control conditions), Day 1, and Day 2. In addition, we compared vasoreactive responses to phenylephrine, carbamylcholine chloride, and sodium nitroprusside at the end of the 2-day culture period. We found significant differences in the structural (e.g., pressure-axial force and axial force-length) responses between groups as well as within each group over time. These adaptations seem to be aimed at restoring the mechanical state from a perturbed condition (e.g., low or high axial extension) toward a normal 'homeostatic' condition. Although structural responses (e.g., pressure-axial force and axial force-length) differed between groups on Day 2, the material behavior (e.g., circumferential and axial stress-stretch responses) did not differ significantly between groups.
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MESH Headings
- Animals
- Biomechanical Phenomena
- Blood Pressure
- Carotid Artery, Common/cytology
- Carotid Artery, Common/drug effects
- Carotid Artery, Common/physiology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/physiology
- Fibroblasts/cytology
- Male
- Mice
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Organ Culture Techniques
- Stress, Mechanical
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Affiliation(s)
- Rudolph L Gleason
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
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48
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Gleason RL, Humphrey JD. A 2D constrained mixture model for arterial adaptations to large changes in flow, pressure and axial stretch. Math Med Biol 2006; 22:347-69. [PMID: 16319121 DOI: 10.1093/imammb/dqi014] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Soft tissue growth and remodelling (G&R) are achieved through highly complex, temporally regulated mechanisms that lead to the adaptation of structurally significant cells and extracellular matrix proteins. Herein we present a constrained mixture model to describe vascular adaptations in response to large perturbations in luminal flow rate, transmural pressure and axial extension. In the associated simulations, G&R occur in evolving loaded (i.e. current) configurations. Although several hypotheses are employed with regard to vasoregulatory mechanisms and rates of growth and turnover of individual constituents, the main hypothesis is that each structural constituent is produced within a range of homeostatic stresses (or stretches). As a result, although material that was produced in one configuration may have the same mechanical behaviour as that produced in another configuration, these materials will possess different natural configurations and contribute a different structural response to the mixture. Our simulations illustrate how, by simply evolving the reference states of individual constituents, blood vessels can adapt their structure and function to restore wall stresses.
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Affiliation(s)
- Rudolph L Gleason
- Department of Biomedical Engineering and M.E. DeBakey Institute, Texas A&M University, 337 Zachry Engineering Center, TAMU 3120, College Station, 77843, USA
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Gleason RL, Gray SP, Wilson E, Humphrey JD. A multiaxial computer-controlled organ culture and biomechanical device for mouse carotid arteries. J Biomech Eng 2005; 126:787-95. [PMID: 15796337 DOI: 10.1115/1.1824130] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Much of our understanding of vascular mechanotransduction has come from studies using either cell culture or in vivo animal models, but the recent success of organ culture systems offers an exciting alternative. In studying cell-mediated vascular adaptations to altered loading, organ culture allows one to impose well-controlled mechanical loads and to perform multiaxial mechanical tests on the same vessel throughout the culture period, and thereby to observe cell-mediated vascular adaptations independent of neural and hormonal effects. Here, we present a computer-controlled perfused organ culture and biomechanical testing device designed for small caliber (50-5000 micron) blood vessels. This device can control precisely the pulsatile pressure, luminal flow, and axial load (or stretch) and perform intermittent biaxial (pressure-diameter and axial load-length) and functional tests to quantify adaptations in mechanical behavior and cellular function, respectively. Device capabilities are demonstrated by culturing mouse carotid arteries for 4 days.
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Affiliation(s)
- R L Gleason
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
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50
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Gleason RL, Humphrey JD. Effects of a sustained extension on arterial growth and remodeling: a theoretical study. J Biomech 2004; 38:1255-61. [PMID: 15863110 DOI: 10.1016/j.jbiomech.2004.06.017] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2003] [Revised: 04/02/2004] [Accepted: 06/22/2004] [Indexed: 10/26/2022]
Abstract
Three recent studies reveal that the unloaded length of a carotid artery increases significantly and rapidly in response to sustained increases in axial extension. Moreover, such lengthening involves an "unprecedented" increase in the rate of turnover of cells and matrix. Although current data are not sufficient for detailed biomechanical analyses, we present general numerical simulations that are consistent with the reported observations and support the hypothesis that rates of turnover correlate with the extent that stresses are perturbed from normal. In particular, a 3-D analysis of wall stress suggests that moderate (15%) increases in axial extension can increase the axial stress to a much greater extent than marked (50%) increases in blood pressure increase the circumferential stress. Furthermore, such increases in axial stress can occur without inducing significant gradients in stress within the wall. Consequently, we use a new, 2-D constrained mixture model to study evolving changes in the geometry, structure, and properties of carotid arteries in response to a sustained increase in axial extension. These simulations are qualitatively similar to the reports in the literature and support the notion that the stress-free lengths of individual constituents evolve during growth and remodeling.
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Affiliation(s)
- R L Gleason
- Department of Biomedical Engineering, M.E. DeBakey Institute, Texas A&M University, 233 Zachry Engineering Center, College Station, TX 77843-3120, USA
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