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Ameku KA, Berggren CC, Pedrigi RM. Implantation of a capsular tension ring during cataract surgery attenuates predicted remodeling of the post-surgical lens capsule along the visual axis. Front Bioeng Biotechnol 2024; 11:1300830. [PMID: 38312508 PMCID: PMC10834774 DOI: 10.3389/fbioe.2023.1300830] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Accepted: 12/26/2023] [Indexed: 02/06/2024] Open
Abstract
Introduction: Cataract surgery permanently alters the mechanical environment of the lens capsule by placing a hole in the anterior portion and implanting an intraocular lens (IOL) that has a very different geometry from the native lens. We hypothesized that implant configuration and mechanical interactions with the post-surgical lens capsule play a key role in determining long-term fibrotic remodeling. Methods: We developed the first finite element-growth and remodeling (FE-G&R) model of the post-surgical lens capsule to evaluate how implantation of an IOL with and without a capsular tension ring (CTR) impacted evolving lens capsule mechanics and associated fibrosis over time after cataract surgery. Results: Our models predicted that implantation of a CTR with the IOL into the post-surgical lens capsule reduced the mechanical perturbation, thickening, and stiffening along the visual axis in both the remnant anterior and posterior portions compared to implantation of the IOL alone. Discussion: These findings align with patient studies and suggest that implantation of a CTR with the IOL during routine cataract surgery would attenuate the incidence of visually-debilitating capsule fibrosis. Our work demonstrates that use of such modeling techniques has substantial potential to aid in the design of better surgical strategies and implants.
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Affiliation(s)
| | | | - Ryan M. Pedrigi
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, United States
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2
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Fogell NAT, Patel M, Yang P, Ruis RM, Garcia DB, Naser J, Savvopoulos F, Davies Taylor C, Post AL, Pedrigi RM, de Silva R, Krams R. Considering the Influence of Coronary Motion on Artery-Specific Biomechanics Using Fluid-Structure Interaction Simulation. Ann Biomed Eng 2023; 51:1950-1964. [PMID: 37436564 PMCID: PMC10409843 DOI: 10.1007/s10439-023-03214-0] [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: 03/16/2022] [Accepted: 04/18/2023] [Indexed: 07/13/2023]
Abstract
The endothelium in the coronary arteries is subject to wall shear stress and vessel wall strain, which influences the biology of the arterial wall. This study presents vessel-specific fluid-structure interaction (FSI) models of three coronary arteries, using directly measured experimental geometries and boundary conditions. FSI models are used to provide a more physiologically complete representation of vessel biomechanics, and have been extended to include coronary bending to investigate its effect on shear and strain. FSI both without- and with-bending resulted in significant changes in all computed shear stress metrics compared to CFD (p = 0.0001). Inclusion of bending within the FSI model produced highly significant changes in Time Averaged Wall Shear Stress (TAWSS) + 9.8% LAD, + 8.8% LCx, - 2.0% RCA; Oscillatory Shear Index (OSI) + 208% LAD, 0% LCx, + 2600% RCA; and transverse wall Shear Stress (tSS) + 180% LAD, + 150% LCx and + 200% RCA (all p < 0.0001). Vessel wall strain was homogenous in all directions without-bending but became highly anisotropic under bending. Changes in median cyclic strain magnitude were seen for all three vessels in every direction. Changes shown in the magnitude and distribution of shear stress and wall strain suggest that bending should be considered on a vessel-specific basis in analyses of coronary artery biomechanics.
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Affiliation(s)
- Nicholas A T Fogell
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK.
| | - Miten Patel
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - Pan Yang
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - Roosje M Ruis
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - David B Garcia
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - Jarka Naser
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - Fotios Savvopoulos
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | | | - Anouk L Post
- Amsterdam UMC, Department of Biomedical Engineering and Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - Ryan M Pedrigi
- Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, USA
| | - Ranil de Silva
- National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Cale Street, London, SW3 6LY, UK
| | - Rob Krams
- School for Material Sciences and Engineering, Queen Mary University, London, UK
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Schake MA, McCue IS, Curtis ET, Ripperda TJ, Harvey S, Hackfort BT, Fitzwater A, Chatzizisis YS, Kievit FM, Pedrigi RM. Restoration of normal blood flow in atherosclerotic arteries promotes plaque stabilization. iScience 2023; 26:106760. [PMID: 37235059 PMCID: PMC10206490 DOI: 10.1016/j.isci.2023.106760] [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] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/23/2023] [Accepted: 04/24/2023] [Indexed: 05/28/2023] Open
Abstract
Blood flow is a key regulator of atherosclerosis. Disturbed blood flow promotes atherosclerotic plaque development, whereas normal blood flow protects against plaque development. We hypothesized that normal blood flow is also therapeutic, if it were able to be restored within atherosclerotic arteries. Apolipoprotein E-deficient (ApoE-/-) mice were initially instrumented with a blood flow-modifying cuff to induce plaque development and then five weeks later the cuff was removed to allow restoration of normal blood flow. Plaques in decuffed mice exhibited compositional changes that indicated increased stability compared to plaques in mice with the cuff maintained. The therapeutic benefit of decuffing was comparable to atorvastatin and the combination had an additive effect. In addition, decuffing allowed restoration of lumen area, blood velocity, and wall shear stress to near baseline values, indicating restoration of normal blood flow. Our findings demonstrate that the mechanical effects of normal blood flow on atherosclerotic plaques promote stabilization.
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Affiliation(s)
- Morgan A. Schake
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Ian S. McCue
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Evan T. Curtis
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Thomas J. Ripperda
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Samuel Harvey
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Bryan T. Hackfort
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Anna Fitzwater
- Institutional Animal Care Program, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Yiannis S. Chatzizisis
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Division of Cardiovascular Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Forrest M. Kievit
- Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE 68583, USA
| | - Ryan M. Pedrigi
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Nebraska Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
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4
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Liu M, Samant S, Vasa CH, Pedrigi RM, Oguz UM, Ryu S, Wei T, Anderson DR, Agrawal DK, Chatzizisis YS. Co-culture models of endothelial cells, macrophages, and vascular smooth muscle cells for the study of the natural history of atherosclerosis. PLoS One 2023; 18:e0280385. [PMID: 36662769 PMCID: PMC9858056 DOI: 10.1371/journal.pone.0280385] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 12/28/2022] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND This work aims to present a fast, affordable, and reproducible three-cell co-culture system that could represent the different cellular mechanisms of atherosclerosis, extending from atherogenesis to pathological intimal thickening. METHODS AND RESULTS We built four culture models: (i) Culture model #1 (representing normal arterial intima), where human coronary artery endothelial cells were added on top of Matrigel-coated collagen type I matrix, (ii) Culture model #2 (representing atherogenesis), which demonstrated the subendothelial accumulation and oxidative modification of low-density lipoproteins (LDL), (iii) Culture model #3 (representing intimal xanthomas), which demonstrated the monocyte adhesion to the endothelial cell monolayer, transmigration into the subendothelial space, and transformation to lipid-laden macrophages, (iv) Culture model #4 (representing pathological intimal thickening), which incorporated multiple layers of human coronary artery smooth muscle cells within the matrix. Coupling this model with different shear stress conditions revealed the effect of low shear stress on the oxidative modification of LDL and the upregulation of pro-inflammatory molecules and matrix-degrading enzymes. Using electron microscopy, immunofluorescence confocal microscopy, protein and mRNA quantification assays, we showed that the behaviors exhibited by the endothelial cells, macrophages and vascular smooth muscle cells in these models were very similar to those exhibited by these cell types in nascent and intermediate atherosclerotic plaques in humans. The preparation time of the cultures was 24 hours. CONCLUSION We present three-cell co-culture models of human atherosclerosis. These models have the potential to allow cost- and time-effective investigations of the mechanobiology of atherosclerosis and new anti-atherosclerotic drug therapies.
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Affiliation(s)
- Martin Liu
- Division of Cardiovascular Medicine, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Saurabhi Samant
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Charu Hasini Vasa
- Division of Cardiovascular Medicine, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Ryan M. Pedrigi
- Department of Biological System Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Usama M. Oguz
- Division of Cardiovascular Medicine, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Sangjin Ryu
- Department of Mechanical and Materials Engineering, College of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Timothy Wei
- Department of Mechanical and Materials Engineering, College of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Daniel R. Anderson
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Devendra K. Agrawal
- Department of Translational Research, Western University of Health Science, Pomona, California, United States of America
| | - Yiannis S. Chatzizisis
- Division of Cardiovascular Medicine, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
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Sahni J, Arshad M, Schake MA, Brooks JR, Yang R, Weinberg PD, Pedrigi RM. Characterizing nuclear morphology and expression of eNOS in vascular endothelial cells subjected to a continuous range of wall shear stress magnitudes and directionality. J Mech Behav Biomed Mater 2023; 137:105545. [PMID: 36368188 PMCID: PMC10371053 DOI: 10.1016/j.jmbbm.2022.105545] [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: 05/24/2022] [Revised: 09/30/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022]
Abstract
Complex patterns of hemodynamic wall shear stress occur in regions of arterial branching and curvature. Areas within these regions can be highly susceptible to atherosclerosis. Although many studies have characterized the response of vascular endothelial cells to shear stress in a categorical manner, our study herein addresses the need of characterizing endothelial behaviors over a continuous range of shear stress conditions that reflect the extensive variations seen in the vasculature. We evaluated the response of human umbilical vein endothelial cell monolayers to orbital flow at 120, 250, and 350 revolutions per minute (RPM) for 24 and 72 h. The orbital shaker model uniquely provides a continuous range of shear stress conditions from low and multidirectional at the center of each well of a culture plate to high and unidirectional at the periphery. We found distinct patterns of endothelial nuclear area, nuclear major and minor diameters, nuclear aspect ratio, and expression of endothelial nitric oxide synthase over this range of shear conditions and relationships were fit with linear and, where appropriate, power functions. Nuclear area was particularly sensitive with increases in the low and multidirectional WSS region that incrementally decreased as WSS became higher in magnitude and more unidirectional over the radius of the cell layers. The patterns of all endothelial behaviors exhibited high correlations (positive and negative) with metrics of shear stress magnitude and directionality that have been shown to strongly associate with atherosclerosis. Our findings demonstrate the exquisite sensitivity of these endothelial behaviors to incremental changes in shear stress magnitude and directionality, and provide critical quantitation of these relationships for predicting the susceptibility of an arterial segment to diseases such as atherosclerosis, particularly within complex flow environments in the vasculature such as around bifurcations.
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Affiliation(s)
- Jaideep Sahni
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA
| | - Mehwish Arshad
- Department of Bioengineering, Imperial College London, UK
| | - Morgan A Schake
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA
| | - Justin R Brooks
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA
| | - Ruiguo Yang
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA
| | | | - Ryan M Pedrigi
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, USA.
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Ameku KA, Pedrigi RM. A Biomechanical Model for Evaluating the Performance of Accommodative Intraocular Lenses. J Biomech 2022; 136:111054. [PMID: 35344827 PMCID: PMC9119028 DOI: 10.1016/j.jbiomech.2022.111054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 12/19/2021] [Accepted: 03/15/2022] [Indexed: 12/22/2022]
Abstract
Accommodation alters the shape of the eye lens to change focus from distant to near vision. This function declines with age in the development of presbyopia and most people experience a near total loss of accommodative ability by 55 years. Currently, there are no surgical procedures that correct presbyopia, but considerable work has been done in the development of accommodative intraocular lenses (AIOLs) implanted during cataract surgery. Despite these efforts, AIOLs only restore ∼ 20% of youthful accommodative amplitude and they suffer from high rates of visually-debilitating fibrosis. An important design tool that is lacking that could aid in improving AIOL designs is modeling. Herein, we addressed this need through the development of a fully 3-D finite element model that was used to predict the behavior of a dual-optic AIOL implanted within the post-surgical lens capsule. Models of the native human lens were developed to identify the stress-free configuration of the lens capsule needed to accurately predict the accommodated state of the lens and the configuration of the zonular traction needed for the disaccommodated state. The AIOL model demonstrated the functional importance of implant stiffness and predicted an approximately linear relationship between zonular traction magnitude and axial displacement of the optics. To our knowledge, this is the first model that can be used to gain insights into AIOL efficacy. It provides a foundation for continued development of a predictive tool that could ultimately improve AIOL designs that seek to restore youthful accommodative function.
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Miller HA, Schake MA, Bony BA, Curtis ET, Gee CC, McCue IS, Ripperda TJ, Chatzizisis YS, Kievit FM, Pedrigi RM. Smooth muscle cells affect differential nanoparticle accumulation in disturbed blood flow-induced murine atherosclerosis. PLoS One 2021; 16:e0260606. [PMID: 34882722 PMCID: PMC8659666 DOI: 10.1371/journal.pone.0260606] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [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: 04/17/2021] [Accepted: 11/12/2021] [Indexed: 11/19/2022] Open
Abstract
Atherosclerosis is a lipid-driven chronic inflammatory disease that leads to the formation of plaques in the inner lining of arteries. Plaques form over a range of phenotypes, the most severe of which is vulnerable to rupture and causes most of the clinically significant events. In this study, we evaluated the efficacy of nanoparticles (NPs) to differentiate between two plaque phenotypes based on accumulation kinetics in a mouse model of atherosclerosis. This model uses a perivascular cuff to induce two regions of disturbed wall shear stress (WSS) on the inner lining of the instrumented artery, low (upstream) and multidirectional (downstream), which, in turn, cause the development of an unstable and stable plaque phenotype, respectively. To evaluate the influence of each WSS condition, in addition to the final plaque phenotype, in determining NP uptake, mice were injected with NPs at intermediate and fully developed stages of plaque growth. The kinetics of artery wall uptake were assessed in vivo using dynamic contrast-enhanced magnetic resonance imaging. At the intermediate stage, there was no difference in NP uptake between the two WSS conditions, although both were different from the control arteries. At the fully-developed stage, however, NP uptake was reduced in plaques induced by low WSS, but not multidirectional WSS. Histological evaluation of plaques induced by low WSS revealed a significant inverse correlation between the presence of smooth muscle cells and NP accumulation, particularly at the plaque-lumen interface, which did not exist with other constituents (lipid and collagen) and was not present in plaques induced by multidirectional WSS. These findings demonstrate that NP accumulation can be used to differentiate between unstable and stable murine atherosclerosis, but accumulation kinetics are not directly influenced by the WSS condition. This tool could be used as a diagnostic to evaluate the efficacy of experimental therapeutics for atherosclerosis.
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Affiliation(s)
- Hunter A. Miller
- Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Morgan A. Schake
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Badrul Alam Bony
- Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Evan T. Curtis
- Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Connor C. Gee
- Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Ian S. McCue
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Thomas J. Ripperda
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
| | - Yiannis S. Chatzizisis
- Cardiovascular Division, University of Nebraska Medical Center, Omaha, NE, United States of America
| | - Forrest M. Kievit
- Department of Biological Systems Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
- * E-mail: (RMP); (FMK)
| | - Ryan M. Pedrigi
- Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE, United States of America
- * E-mail: (RMP); (FMK)
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8
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Berggren CC, Ameku KA, Pedrigi RM. Altered stress field of the human lens capsule after cataract surgery. J Biomech 2020; 115:110127. [PMID: 33223144 DOI: 10.1016/j.jbiomech.2020.110127] [Citation(s) in RCA: 3] [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] [Received: 05/18/2020] [Revised: 10/16/2020] [Accepted: 11/04/2020] [Indexed: 10/23/2022]
Abstract
The lens capsule of the eye is important in focusing light onto the retina during the process of accommodation and, in later life, housing a prosthetic lens implanted during cataract surgery. Though considerable modeling work has characterized the mechanics of accommodation, little has been done to understand the mechanics of the lens capsule after cataract surgery. As such, we present the first 3-D finite element model of the post-surgical human lens capsule with an implanted tension ring and, separately, an intraocular lens to characterize the altered stress field compared to that in a model of the native lens capsule. All finite element models employed a Holzapfel hyperelastic constitutive model with regional variations in anisotropy. The post-surgical lens capsule demonstrated a dramatic perturbation to the stress field with mostly large reductions in stresses (except at the equator where the implant contacts the capsule) compared to native, wherein maximal changes in Cauchy stress were -100% and -145% for the tension ring and intraocular lens, respectively. However, implantation of the tension ring produced a more uniform stress field compared to the IOL. The magnitudes and distribution of the perturbed stress field may be an important driver of the fibrotic response of inhabiting lens epithelial cells and associated lens capsule remodeling after cataract surgery. Thus, the mechanical effects of an implant on the lens capsule could be an essential consideration in the design of intraocular lenses, particularly those with an accommodative feature.
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Affiliation(s)
- Caleb C Berggren
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, United States
| | - Kurt A Ameku
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, United States
| | - Ryan M Pedrigi
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, United States.
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9
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Poulsen CB, Pedrigi RM, Pareek N, Kilic ID, Holm NR, Bentzon JF, Bøtker HE, Falk E, Krams R, de Silva R. Plaque burden influences accurate classification of fibrous cap atheroma by in vivo optical coherence tomography in a porcine model of advanced coronary atherosclerosis. EUROINTERVENTION 2018; 14:1129-1135. [PMID: 29616625 DOI: 10.4244/eij-d-17-01028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
AIMS In vivo validation of coronary optical coherence tomography (OCT) against histology and the effects of plaque burden (PB) on plaque classification remain unreported. We aimed to investigate this in a porcine model with human-like coronary atherosclerosis. METHODS AND RESULTS Five female Yucatan D374Y-PCSK9 transgenic hypercholesterolaemic minipigs were implanted with a coronary shear-modifying stent to induce advanced atherosclerosis. OCT frames (n=201) were obtained 34 weeks after implantation. Coronary arteries were perfusion-fixed, serially sectioned and co-registered with OCT using a validated algorithm. Lesions were adjudicated using the Virmani classification and PB assessed from histology. OCT had a high sensitivity, but modest specificity (92.9% and 74.6%), for identifying fibrous cap atheroma (FCA). The reduced specificity for OCT was due to misclassification of plaques with histologically defined pathological intimal thickening (PIT) as FCA (46.1% of the frames with histological PIT were misclassified). PIT lesions misclassified as FCA by OCT had a statistically higher PB than in other OCT frames (median 32.0% versus 13.4%; p<0.0001). Misclassification of PIT lesions by OCT occurred when PB exceeded approximately 20%. CONCLUSIONS Compared with histology, in vivo OCT classification of FCA had high sensitivity but reduced specificity due to misclassification of PITs with high PB.
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10
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Pedrigi RM, Mehta VV, Bovens SM, Mohri Z, Poulsen CB, Gsell W, Tremoleda JL, Towhidi L, de Silva R, Petretto E, Krams R. Influence of shear stress magnitude and direction on atherosclerotic plaque composition. R Soc Open Sci 2016; 3:160588. [PMID: 27853578 PMCID: PMC5099003 DOI: 10.1098/rsos.160588] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 09/19/2016] [Indexed: 05/19/2023]
Abstract
The precise flow characteristics that promote different atherosclerotic plaque types remain unclear. We previously developed a blood flow-modifying cuff for ApoE-/- mice that induces the development of advanced plaques with vulnerable and stable features upstream and downstream of the cuff, respectively. Herein, we sought to test the hypothesis that changes in flow magnitude promote formation of the upstream (vulnerable) plaque, whereas altered flow direction is important for development of the downstream (stable) plaque. We instrumented ApoE-/- mice (n = 7) with a cuff around the left carotid artery and imaged them with micro-CT (39.6 µm resolution) eight to nine weeks after cuff placement. Computational fluid dynamics was then performed to compute six metrics that describe different aspects of atherogenic flow in terms of wall shear stress magnitude and/or direction. In a subset of four imaged animals, we performed histology to confirm the presence of advanced plaques and measure plaque length in each segment. Relative to the control artery, the region upstream of the cuff exhibited changes in shear stress magnitude only (p < 0.05), whereas the region downstream of the cuff exhibited changes in shear stress magnitude and direction (p < 0.05). These data suggest that shear stress magnitude contributes to the formation of advanced plaques with a vulnerable phenotype, whereas variations in both magnitude and direction promote the formation of plaques with stable features.
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Affiliation(s)
- Ryan M. Pedrigi
- Department of Bioengineering, Imperial College London, London, UK
| | - Vikram V. Mehta
- Department of Bioengineering, Imperial College London, London, UK
| | - Sandra M. Bovens
- Department of Bioengineering, Imperial College London, London, UK
| | - Zahra Mohri
- Department of Bioengineering, Imperial College London, London, UK
| | | | - Willy Gsell
- MRC-Clinical Sciences Centre, Imperial College London, London, UK
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Jordi L. Tremoleda
- MRC-Clinical Sciences Centre, Imperial College London, London, UK
- Centre for Trauma Sciences, Queen Mary University of London, London, UK
| | - Leila Towhidi
- Department of Bioengineering, Imperial College London, London, UK
| | - Ranil de Silva
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Enrico Petretto
- MRC-Clinical Sciences Centre, Imperial College London, London, UK
- Duke-NUS Medical School, Singapore, Republic of Singapore
| | - Rob Krams
- Department of Bioengineering, Imperial College London, London, UK
- Author for correspondence: Rob Krams e-mail:
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11
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Towhidi L, Khodadadi D, Maimari N, Pedrigi RM, Ip H, Kis Z, Kwak BR, Petrova TW, Delorenzi M, Krams R. Comparison between direct and reverse electroporation of cells in situ: a simulation study. Physiol Rep 2016; 4:4/6/e12673. [PMID: 27009275 PMCID: PMC4814886 DOI: 10.14814/phy2.12673] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/10/2015] [Indexed: 01/12/2023] Open
Abstract
The discovery of the human genome has unveiled new fields of genomics, transcriptomics, and proteomics, which has produced paradigm shifts on how to study disease mechanisms, wherein a current central focus is the understanding of how gene signatures and gene networks interact within cells. These gene function studies require manipulating genes either through activation or inhibition, which can be achieved by temporarily permeabilizing the cell membrane through transfection to deliver cDNA or RNAi. An efficient transfection technique is electroporation, which applies an optimized electric pulse to permeabilize the cells of interest. When the molecules are applied on top of seeded cells, it is called “direct” transfection and when the nucleic acids are printed on the substrate and the cells are seeded on top of them, it is termed “reverse” transfection. Direct transfection has been successfully applied in previous studies, whereas reverse transfection has recently gained more attention in the context of high‐throughput experiments. Despite the emerging importance, studies comparing the efficiency of the two methods are lacking. In this study, a model for electroporation of cells in situ is developed to address this deficiency. The results indicate that reverse transfection is less efficient than direct transfection. However, the model also predicts that by increasing the concentration of deliverable molecules by a factor of 2 or increasing the applied voltage by 20%, reverse transfection can be approximately as efficient as direct transfection.
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Affiliation(s)
- Leila Towhidi
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Delaram Khodadadi
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Nataly Maimari
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Ryan M Pedrigi
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Henry Ip
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Zoltan Kis
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Brenda R Kwak
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - Tatiana W Petrova
- Department of Oncology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Mauro Delorenzi
- Department of Oncology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Rob Krams
- Department of Bioengineering, Imperial College London, London, United Kingdom
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12
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David G, Pedrigi RM, Humphrey JD. Accommodation of the human lens capsule using a finite element model based on nonlinear regionally anisotropic biomembranes. Comput Methods Biomech Biomed Engin 2016; 20:302-307. [PMID: 27609339 DOI: 10.1080/10255842.2016.1228907] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [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: 10/21/2022]
Abstract
Accommodation of the eyes, the mechanism that allows humans to focus their vision on near objects, naturally diminishes with age via presbyopia. People who have undergone cataract surgery, using current surgical methods and artificial lens implants, are also left without the ability to accommodate. The process of accommodation is generally well known; however the specific mechanical details have not been adequately explained due to difficulties and consequences of performing in vivo studies. Most studies have modeled the mechanics of accommodation under assumptions of a linearly elastic, isotropic, homogenous lens and lens capsule. Recent experimental and numerical studies showed that the lens capsule exhibits nonlinear elasticity and regional anisotropy. In this paper we present a numerical model of human accommodation using a membrane theory based finite element approach, incorporating recent findings on capsular properties. This study seeks to provide a novel perspective of the mechanics of accommodation. Such findings may prove significant in seeking biomedical solutions to restoring loss of visual power.
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Affiliation(s)
- G David
- a Institute of Mathematics , University of the Philippines , Quezon City , Philippines
| | - R M Pedrigi
- b Department of Bioengineering , Imperial College London , London , UK
| | - J D Humphrey
- c Department of Biomedical Engineering , Yale University , New Haven , CT , USA
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13
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Antonacci G, Pedrigi RM, Kondiboyina A, Mehta VV, de Silva R, Paterson C, Krams R, Török P. Quantification of plaque stiffness by Brillouin microscopy in experimental thin cap fibroatheroma. J R Soc Interface 2016; 12:rsif.2015.0843. [PMID: 26559685 DOI: 10.1098/rsif.2015.0843] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Plaques vulnerable to rupture are characterized by a thin and stiff fibrous cap overlaying a soft lipid-rich necrotic core. The ability to measure local plaque stiffness directly to quantify plaque stress and predict rupture potential would be very attractive, but no current technology does so. This study seeks to validate the use of Brillouin microscopy to measure the Brillouin frequency shift, which is related to stiffness, within vulnerable plaques. The left carotid artery of an ApoE(-/-)mouse was instrumented with a cuff that induced vulnerable plaque development in nine weeks. Adjacent histological sections from the instrumented and control arteries were stained for either lipids or collagen content, or imaged with confocal Brillouin microscopy. Mean Brillouin frequency shift was 15.79 ± 0.09 GHz in the plaque compared with 16.24 ± 0.15 (p < 0.002) and 17.16 ± 0.56 GHz (p < 0.002) in the media of the diseased and control vessel sections, respectively. In addition, frequency shift exhibited a strong inverse correlation with lipid area of -0.67 ± 0.06 (p < 0.01) and strong direct correlation with collagen area of 0.71 ± 0.15 (p < 0.05). This is the first study, to the best of our knowledge, to apply Brillouin spectroscopy to quantify atherosclerotic plaque stiffness, which motivates combining this technology with intravascular imaging to improve detection of vulnerable plaques in patients.
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Affiliation(s)
- Giuseppe Antonacci
- Department of Physics, Imperial College London, London, UK Center for Life Nano Science, Istituto Italiano di Tecnologia, Rome, Italy
| | - Ryan M Pedrigi
- Department of Bioengineering, Imperial College London, London, UK
| | | | - Vikram V Mehta
- Department of Bioengineering, Imperial College London, London, UK
| | - Ranil de Silva
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Carl Paterson
- Department of Physics, Imperial College London, London, UK
| | - Rob Krams
- Department of Bioengineering, Imperial College London, London, UK
| | - Peter Török
- Department of Physics, Imperial College London, London, UK
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14
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Kis Z, Rodin T, Zafar A, Lai Z, Freke G, Fleck O, Del Rio Hernandez A, Towhidi L, Pedrigi RM, Homma T, Krams R. Development of a synthetic gene network to modulate gene expression by mechanical forces. Sci Rep 2016; 6:29643. [PMID: 27404994 PMCID: PMC4940741 DOI: 10.1038/srep29643] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [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: 02/17/2016] [Accepted: 06/24/2016] [Indexed: 12/14/2022] Open
Abstract
The majority of (mammalian) cells in our body are sensitive to mechanical forces, but little work has been done to develop assays to monitor mechanosensor activity. Furthermore, it is currently impossible to use mechanosensor activity to drive gene expression. To address these needs, we developed the first mammalian mechanosensitive synthetic gene network to monitor endothelial cell shear stress levels and directly modulate expression of an atheroprotective transcription factor by shear stress. The technique is highly modular, easily scalable and allows graded control of gene expression by mechanical stimuli in hard-to-transfect mammalian cells. We call this new approach mechanosyngenetics. To insert the gene network into a high proportion of cells, a hybrid transfection procedure was developed that involves electroporation, plasmids replication in mammalian cells, mammalian antibiotic selection, a second electroporation and gene network activation. This procedure takes 1 week and yielded over 60% of cells with a functional gene network. To test gene network functionality, we developed a flow setup that exposes cells to linearly increasing shear stress along the length of the flow channel floor. Activation of the gene network varied logarithmically as a function of shear stress magnitude.
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Affiliation(s)
- Zoltán Kis
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
| | - Tania Rodin
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
| | - Asma Zafar
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
- Government College University, GC University, Katchery Road, Lahore, 54000, Pakistan
| | - Zhangxing Lai
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
| | - Grace Freke
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
- Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1EH, United Kingdom
| | - Oliver Fleck
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, United Kingdom
| | - Armando Del Rio Hernandez
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
| | - Leila Towhidi
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
| | - Ryan M. Pedrigi
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
| | - Takayuki Homma
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
- Institute for Integrated Cell-Material Sciences, Kyoto University, Yoshida Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Rob Krams
- Department of Bioengineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom
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15
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Abstract
In this review, we discuss new emerging medical applications of the rapidly evolving field of mammalian synthetic biology. We start with simple mammalian synthetic biological components and move towards more complex and therapy-oriented gene circuits. A comprehensive list of ON-OFF switches, categorized into transcriptional, post-transcriptional, translational and post-translational, is presented in the first sections. Subsequently, Boolean logic gates, synthetic mammalian oscillators and toggle switches will be described. Several synthetic gene networks are further reviewed in the medical applications section, including cancer therapy gene circuits, immuno-regulatory networks, among others. The final sections focus on the applicability of synthetic gene networks to drug discovery, drug delivery, receptor-activating gene circuits and mammalian biomanufacturing processes.
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Affiliation(s)
- Zoltán Kis
- Department of Bioengineering, Imperial College London, London, UK
| | | | - Takayuki Homma
- Department of Bioengineering, Imperial College London, London, UK
| | - Ryan M Pedrigi
- Department of Bioengineering, Imperial College London, London, UK
| | - Rob Krams
- Department of Bioengineering, Imperial College London, London, UK
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16
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Maimari N, Pedrigi RM, Russo A, Broda K, Krams R. Integration of flow studies for robust selection of mechanoresponsive genes. Thromb Haemost 2016; 115:474-83. [PMID: 26842798 DOI: 10.1160/th15-09-0704] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 11/13/2015] [Indexed: 11/05/2022]
Abstract
Blood flow is an essential contributor to plaque growth, composition and initiation. It is sensed by endothelial cells, which react to blood flow by expressing > 1000 genes. The sheer number of genes implies that one needs genomic techniques to unravel their response in disease. Individual genomic studies have been performed but lack sufficient power to identify subtle changes in gene expression. In this study, we investigated whether a systematic meta-analysis of available microarray studies can improve their consistency. We identified 17 studies using microarrays, of which six were performed in vivo and 11 in vitro. The in vivo studies were disregarded due to the lack of the shear profile. Of the in vitro studies, a cross-platform integration of human studies (HUVECs in flow cells) showed high concordance (> 90 %). The human data set identified > 1600 genes to be shear responsive, more than any other study and in this gene set all known mechanosensitive genes and pathways were present. A detailed network analysis indicated a power distribution (e. g. the presence of hubs), without a hierarchical organisation. The average cluster coefficient was high and further analysis indicated an aggregation of 3 and 4 element motifs, indicating a high prevalence of feedback and feed forward loops, similar to prokaryotic cells. In conclusion, this initial study presented a novel method to integrate human-based mechanosensitive studies to increase its power. The robust network was large, contained all known mechanosensitive pathways and its structure revealed hubs, and a large aggregate of feedback and feed forward loops.
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Affiliation(s)
| | | | | | | | - Rob Krams
- Prof. Rob Krams, Chair in Molecular Bioengineering, Dept. Bioengineering, Imperial College London, Room 3.15, Royal School of Mines, Exhibition Road, SW7 2AZ London, UK, Tel.:+44 2075941473, E-mail:
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17
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Pfenniger A, Meens MJ, Pedrigi RM, Foglia B, Sutter E, Pelli G, Rochemont V, Petrova TV, Krams R, Kwak BR. Shear stress-induced atherosclerotic plaque composition in ApoE(-/-) mice is modulated by connexin37. Atherosclerosis 2015; 243:1-10. [PMID: 26342936 DOI: 10.1016/j.atherosclerosis.2015.08.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 08/17/2015] [Accepted: 08/21/2015] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Shear stress patterns influence atherogenesis and plaque stability; low laminar shear stress (LLSS) promotes unstable plaques whereas oscillatory shear stress (OSS) induces more stable plaques. Endothelial connexin37 (Cx37) expression is also regulated by shear stress, which may contribute to localization of atherosclerotic disease. Moreover, Cx37 reduces initiation of atherosclerosis by inhibiting monocyte adhesion. The present work investigates the effect of Cx37 on the phenotype of plaques induced by LLSS or OSS. METHODS Shear stress-modifying casts were placed around the common carotid artery of ApoE(-/-) or ApoE(-/-)Cx37(-/-) mice, and animals were placed on a high-cholesterol diet for 6 or 9 weeks. Atherosclerotic plaque size and composition were assessed by immunohistochemistry. RESULTS Plaque size in response to OSS was increased in ApoE(-/-)Cx37(-/-) mice compared to ApoE(-/-) animals. Most plaques contained high lipid and macrophage content and a low amount of collagen. In ApoE(-/-) mice, macrophages were more prominent in LLSS than OSS plaques. This difference was reversed in ApoE(-/-)Cx37(-/-) animals, with a predominance of macrophages in OSS plaques. The increase in macrophage content in ApoE(-/-)Cx37(-/-) OSS plaques was mainly due to increased accumulation of M1 and Mox macrophage subtypes. Cx37 expression in macrophages did not affect their proliferation or their polarization in vitro. CONCLUSION Cx37 deletion increased the size of atherosclerotic lesions in OSS regions and abrogated the development of a stable plaque phenotype under OSS in ApoE(-/-) mice. Hence, local hemodynamic factors may modify the risk for adverse atherosclerotic disease outcomes associated to a polymorphism in the human Cx37 gene.
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Affiliation(s)
- A Pfenniger
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - M J Meens
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - R M Pedrigi
- Department of Bioengineering, Imperial College, London, UK
| | - B Foglia
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - E Sutter
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - G Pelli
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - V Rochemont
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland
| | - T V Petrova
- Department of Oncology, CHUV and University of Lausanne, Epalinges, Switzerland
| | - R Krams
- Department of Bioengineering, Imperial College, London, UK
| | - B R Kwak
- Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, University of Geneva, Geneva, Switzerland.
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18
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Pedrigi RM, Poulsen CB, Mehta VV, Ramsing Holm N, Pareek N, Post AL, Kilic ID, Banya WAS, Dall'Ara G, Mattesini A, Bjørklund MM, Andersen NP, Grøndal AK, Petretto E, Foin N, Davies JE, Di Mario C, Fog Bentzon J, Erik Bøtker H, Falk E, Krams R, de Silva R. Inducing Persistent Flow Disturbances Accelerates Atherogenesis and Promotes Thin Cap Fibroatheroma Development in D374Y-PCSK9 Hypercholesterolemic Minipigs. Circulation 2015; 132:1003-12. [PMID: 26179404 DOI: 10.1161/circulationaha.115.016270] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [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: 03/02/2015] [Accepted: 07/06/2015] [Indexed: 12/22/2022]
Abstract
BACKGROUND Although disturbed flow is thought to play a central role in the development of advanced coronary atherosclerotic plaques, no causal relationship has been established. We evaluated whether inducing disturbed flow would cause the development of advanced coronary plaques, including thin cap fibroatheroma. METHODS AND RESULTS D374Y-PCSK9 hypercholesterolemic minipigs (n=5) were instrumented with an intracoronary shear-modifying stent (SMS). Frequency-domain optical coherence tomography was obtained at baseline, immediately poststent, 19 weeks, and 34 weeks, and used to compute shear stress metrics of disturbed flow. At 34 weeks, plaque type was assessed within serially collected histological sections and coregistered to the distribution of each shear metric. The SMS caused a flow-limiting stenosis, and blood flow exiting the SMS caused regions of increased shear stress on the outer curvature and large regions of low and multidirectional shear stress on the inner curvature of the vessel. As a result, plaque burden was ≈3-fold higher downstream of the SMS than both upstream of the SMS and in the control artery (P<0.001). Advanced plaques were also primarily observed downstream of the SMS, in locations initially exposed to both low (P<0.002) and multidirectional (P<0.002) shear stress. Thin cap fibroatheroma regions demonstrated significantly lower shear stress that persisted over the duration of the study in comparison with other plaque types (P<0.005). CONCLUSIONS These data support a causal role for lowered and multidirectional shear stress in the initiation of advanced coronary atherosclerotic plaques. Persistently lowered shear stress appears to be the principal flow disturbance needed for the formation of thin cap fibroatheroma.
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Affiliation(s)
- Ryan M Pedrigi
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Christian Bo Poulsen
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Vikram V Mehta
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Niels Ramsing Holm
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Nilesh Pareek
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Anouk L Post
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Ismail Dogu Kilic
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Winston A S Banya
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Gianni Dall'Ara
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Alessio Mattesini
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Martin M Bjørklund
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Niels P Andersen
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Anna K Grøndal
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Enrico Petretto
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Nicolas Foin
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Justin E Davies
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Carlo Di Mario
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Jacob Fog Bentzon
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Hans Erik Bøtker
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Erling Falk
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Rob Krams
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.)
| | - Ranil de Silva
- From Department of Bioengineering, Imperial College London, United Kingdom (R.M.P., V.V.M., A.L.P., R.K.); Institute of Clinical Medicine, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., E.F.); Department of Cardiology, Aarhus University Hospital, Denmark (C.B.P., N.R.H., M.M.B., N.P.A., A.K.G., J.F.B., H.E.B., E.F.); NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (I.D.K., W.A.S.B., G.D.'A., A.M., C.D.M., R.d.S.); Graduate Medical School, Duke-National University of Singapore, Singapore (E.P.); National Heart Centre, NHRIS, Singapore (N.F.); National Heart and Lung Institute, Imperial College London, United Kingdom (C.D.M., R.d.S.); and Institute of Cardiovascular Medicine and Science, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (C.D.M., R.d.S.).
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19
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Poulsen CB, Pedrigi RM, Mehta VV, Post A, Pareek N, Holm NR, Kilic D, El-Bahnasawi M, Bjørklund MM, Andersen NP, Grøndal AK, Nachiappan A, Foin N, Davies JER, Di Mario C, Bøtker HE, Bentzon JF, Falk E, Krams R, de Silva R. INDUCTION OF PERTURBED SHEAR STRESS LEADS TO FOCAL ADVANCED ATHEROSCLEROTIC PLAQUE FORMATION IN TRANSGENIC MINIPIGS WITH HYPERCHOLESTEROLEMIA. J Am Coll Cardiol 2015. [DOI: 10.1016/s0735-1097(15)61927-1] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Braakman ST, Pedrigi RM, Read AT, Smith JAE, Stamer WD, Ethier CR, Overby DR. Biomechanical strain as a trigger for pore formation in Schlemm's canal endothelial cells. Exp Eye Res 2014; 127:224-35. [PMID: 25128579 PMCID: PMC4175173 DOI: 10.1016/j.exer.2014.08.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [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: 03/14/2014] [Revised: 08/01/2014] [Accepted: 08/05/2014] [Indexed: 02/08/2023]
Abstract
The bulk of aqueous humor passing through the conventional outflow pathway must cross the inner wall endothelium of Schlemm's canal (SC), likely through micron-sized transendothelial pores. SC pore density is reduced in glaucoma, possibly contributing to obstructed aqueous humor outflow and elevated intraocular pressure (IOP). Little is known about the mechanisms of pore formation; however, pores are often observed near dome-like cellular outpouchings known as giant vacuoles (GVs) where significant biomechanical strain acts on SC cells. We hypothesize that biomechanical strain triggers pore formation in SC cells. To test this hypothesis, primary human SC cells were isolated from three non-glaucomatous donors (aged 34, 44 and 68), and seeded on collagen-coated elastic membranes held within a membrane stretching device. Membranes were then exposed to 0%, 10% or 20% equibiaxial strain, and the cells were aldehyde-fixed 5 min after the onset of strain. Each membrane contained 3-4 separate monolayers of SC cells as replicates (N = 34 total monolayers), and pores were assessed by scanning electron microscopy in 12 randomly selected regions (∼65,000 μm(2) per monolayer). Pores were identified and counted by four independent masked observers. Pore density increased with strain in all three cell lines (p < 0.010), increasing from 87 ± 36 pores/mm(2) at 0% strain to 342 ± 71 at 10% strain; two of the three cell lines showed no additional increase in pore density beyond 10% strain. Transcellular "I-pores" and paracellular "B-pores" both increased with strain (p < 0.038), however B-pores represented the majority (76%) of pores. Pore diameter, in contrast, appeared unaffected by strain (p = 0.25), having a mean diameter of 0.40 μm for I-pores (N = 79 pores) and 0.67 μm for B-pores (N = 350 pores). Pore formation appears to be a mechanosensitive process that is triggered by biomechanical strain, suggesting that SC cells have the ability to modulate local pore density and filtration characteristics of the inner wall endothelium based on local biomechanical cues. The molecular mechanisms of pore formation and how they become altered in glaucoma may be studied in vitro using stretched SC cells.
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Affiliation(s)
- Sietse T Braakman
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Ryan M Pedrigi
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - A Thomas Read
- Department of Ophthalmology and Vision Sciences, University of Toronto, Canada
| | - James A E Smith
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - W Daniel Stamer
- Department of Ophthalmology, Duke University Medical School, USA
| | - C Ross Ethier
- Department of Bioengineering, Imperial College London, London, United Kingdom; Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, USA
| | - Darryl R Overby
- Department of Bioengineering, Imperial College London, London, United Kingdom.
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21
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Pedrigi RM, de Silva R, Bovens SM, Mehta VV, Petretto E, Krams R. Thin-Cap Fibroatheroma Rupture Is Associated With a Fine Interplay of Shear and Wall Stress. Arterioscler Thromb Vasc Biol 2014; 34:2224-31. [DOI: 10.1161/atvbaha.114.303426] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this review, we summarized the effect of mechanical factors (shear and wall stress) on thin-cap fibroatheroma formation and rupture. To make this review understandable for a biology-oriented audience, we start with detailed definitions of relevant mechanical metrics. We then describe how biomechanics has supported histopathologic efforts to understand the basis of plaque rupture. In addition to plaque rupture, biomechanics also contributes toward the progression of thin-cap fibroatheroma through a multitude of reported mechanobiological mechanisms. We thus propose a new mechanism whereby both shear stress and wall stress interact to create thin-cap fibroatheromas. Specifically, when regions of certain blood flow and wall mechanical stimuli coincide, they synergistically create inflammation within the cellular environment that can lead to thin-cap fibroatheroma rupture. A consequence of this postulate is that local shear stress is not sufficient to cause rupture, but it must coincide with regions of local tissue stiffening and stress concentrations that can occur during plaque progression. Because such changes to the wall mechanics occur over a micrometer scale, high spatial resolution imaging techniques will be necessary to evaluate this hypothesis and ultimately predict plaque rupture in a clinical environment.
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Affiliation(s)
- Ryan M. Pedrigi
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
| | - Ranil de Silva
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
| | - Sandra M. Bovens
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
| | - Vikram V. Mehta
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
| | - Enrico Petretto
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
| | - Rob Krams
- From the Department of Bioengineering, Imperial College London, London, United Kingdom (R.M.P., S.M.B., V.V.M., R.K.); NHLI, Imperial College London and NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom (R.d.S.); and MRC-Clinical Sciences Centre, Imperial College London, London, United Kingdom (E.P.)
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22
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Abstract
This review provides an overview of the effect of blood flow on endothelial cell (EC) signalling pathways, applying microarray technologies to cultured cells, and in vivo studies of normal and atherosclerotic animals. It is found that in cultured ECs, 5-10% of genes are up- or down-regulated in response to fluid flow, whereas only 3-6% of genes are regulated by varying levels of fluid flow. Of all genes, 90% are regulated by the steady part of fluid flow and 10% by pulsatile components. The associated gene profiles show high variability from experiment to experiment depending on experimental conditions, and importantly, the bioinformatical methods used to analyse the data. Despite this high variability, the current data sets can be summarized with the concept of endothelial priming. In this concept, fluid flows confer protection by an up-regulation of anti-atherogenic, anti-thrombotic, and anti-inflammatory gene signatures. Consequently, predilection sites of atherosclerosis, which are associated with low-shear stress, confer low protection for atherosclerosis and are, therefore, more sensitive to high cholesterol levels. Recent studies in intact non-atherosclerotic animals confirmed these in vitro studies, and suggest that a spatial component might be present. Despite the large variability, a few signalling pathways were consistently present in the majority of studies. These were the MAPK, the nuclear factor-κB, and the endothelial nitric oxide synthase-NO pathways.
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Affiliation(s)
- Jennifer Frueh
- Department of Bioengineering, Royal School of Mines, Imperial College London, Exhibition Road, SW7 2AZ London, UK
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23
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Lei Y, Rajabi S, Pedrigi RM, Overby DR, Read AT, Ethier CR. In vitro models for glaucoma research: effects of hydrostatic pressure. Invest Ophthalmol Vis Sci 2011; 52:6329-39. [PMID: 21693606 DOI: 10.1167/iovs.11-7836] [Citation(s) in RCA: 24] [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: 11/24/2022] Open
Abstract
PURPOSE The response of cells (e.g., optic nerve head [ONH] cells) to mechanical stress is important in glaucoma. Studies have reported the biological effects of hydrostatic pressure on ONH cells cultured on a rigid substrate. An apparatus, designed to independently vary hydrostatic pressure and gas tension (including oxygen tension) in culture medium, was used to evaluate the effects of pressure and tension on cell migration, shape, and α-tubulin architecture in a transformed cell line (DITNC1 rat cortical astrocytes). METHODS During the assay period, cells were exposed to one of four experimental configurations: (1) control pressure and control gas tension; (2) high-pressure (7.4 mm Hg) and reduced gas tension; (3) control pressure and reduced gas tension; and (4) high-pressure and control gas tension. RESULTS Calculations suggested that the cells in configurations 2 and 3 were hypoxic, as confirmed by direct measurements in configuration 2. No effects of hydrostatic pressure were observed on cell migration or α-tubulin architecture. However, cells cultured under low gas tension (configurations 2 and 3) showed increased migration at 48 and 72 hours (P < 0.05). CONCLUSIONS A hydrostatic pressure of 7.4 mm Hg has no effect on DITNC1 astrocytes cultured on rigid coverslips, whereas hypoxia associated with a fluid column creating this pressure does. These results differ from those in a previous report, the results of which may be explained by altered gas tensions in the culture medium. Steps are recommended for control of secondary effects when testing the effect of pressure on cultured cells.
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Affiliation(s)
- Yuan Lei
- Department of Bioengineering, Imperial College London, London, United Kingdom
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24
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Pedrigi RM, Humphrey JD. Computational model of evolving lens capsule biomechanics following cataract-like surgery. Ann Biomed Eng 2010; 39:537-48. [PMID: 20665113 DOI: 10.1007/s10439-010-0133-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [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: 07/14/2010] [Indexed: 10/19/2022]
Abstract
Cataract surgery is an invasive procedure whereby lens fibers are removed through a permanent central hole, or capsulorhexis, in the surrounding lens capsule and replaced with an artificial intraocular lens (IOL). Remnant lens epithelial cells subsequently transdifferentiate to a more contractile and synthetic wound-healing phenotype, which causes significant structural and mechanical adaptations of the residual lens capsule. The goal of this study is to present a computational model capable of capturing salient features of the biomechanical evolution of the lens capsule following cataract-like surgery. The model is shown to predict marked long-term increases in thickness and stiffness of the lens capsule nearest the edge of the capsulorhexis comparable to reported measurements. Such models represent a first step toward understanding better the long-term interactions between the residual lens capsule and implanted IOL, thus initiating a new paradigm for the design of improved IOLs, including those having an accommodative feature.
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Affiliation(s)
- R M Pedrigi
- Department of Bioengineering, Royal School of Mines, Imperial College London, London, SW7 2AZ, UK.
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25
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Pedrigi RM, Dziezyc J, Kalodimos HA, Humphrey JD. Ex vivo quantification of the time course of contractile loading of the porcine lens capsule after cataract-like surgery. Exp Eye Res 2009; 89:869-75. [PMID: 19638277 DOI: 10.1016/j.exer.2009.07.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Revised: 07/20/2009] [Accepted: 07/20/2009] [Indexed: 11/30/2022]
Abstract
Cataract surgery is an invasive procedure that replaces the quasi-spherical native lens fibers with a flat prosthetic device, which initially reduces mechanical stress within the remnant lens capsule and, ultimately, leads to contraction of the capsule about the implant. Although resultant changes in geometry have been quantified previously, little is known about the loads associated with this contraction. We present a novel experimental culture device to quantify ex vivo the time course of increases in tension within the contracting lens capsule after cataract-like surgery. Results demonstrate that contraction reaches steady state within approximately one month with a mean tension of 1.45 mN/mm and Cauchy (true) stress of 13.4 kPa. A significant increase in alpha-smooth muscle actin (alpha-SMA) was also found in post-cultured compared to fresh lens capsules, thus suggesting that transdifferentiated lens epithelial cells (LECs) modulated the contraction. Quantification of loads imparted by the contracting lens capsule is important for assessing implant/capsule interactions and implant stability in vivo. Because contraction of the capsule may be modulated in part by LECs attempting to restore their native mechanical environment, our results further suggest a possible mechanism for the long-term errant changes in capsular structure commonly observed after surgery.
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Affiliation(s)
- R M Pedrigi
- Dept. of Biomedical Engineering, Texas A&M University, College Station, TX 77843-3120, USA.
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Pedrigi RM, Staff E, David G, Glenn S, Humphrey JD. Altered multiaxial mechanical properties of the porcine anterior lens capsule cultured in high glucose. J Biomech Eng 2007; 129:121-5. [PMID: 17227107 DOI: 10.1115/1.2401192] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [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
Hyperglycemia can alter the mechanical properties of tissues through the formation of advanced glycation endproducts in matrix proteins that have long half-lives. We used a custom experimental system and subdomain finite element method to quantify alterations in the regional multiaxial mechanical properties of porcine lens capsules that were cultured for 8 or 14 weeks in high glucose versus control media. Findings revealed that high glucose significantly stiffened the capsules in both the circumferential and the meridional directions, but it did not affect the known regional variations in anisotropy. Such information could be important in the design of both improved clinical procedures and intraocular implants for diabetic patients.
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Affiliation(s)
- R M Pedrigi
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843-3120, USA
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27
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Abstract
The lens capsule of the eye plays fundamental biomechanical roles in both normal physiological processes and clinical interventions. There has been modest attention given to the mechanical properties of this important membrane, however, and prior studies have focused on 1-D analyses of the data. We present results that suggest that the porcine anterior lens capsule has a complex, regionally dependent, nonlinear, anisotropic behavior. Specifically, using a subdomain inverse finite element method to analyze data collected via a new biplane video-based test system, we found that the lens capsule is nearly isotropic (in-plane) near the pole but progressively stiffer in the circumferential compared to the meridional direction as one approaches the equator. Because the porcine capsule is a good model of the young human capsule, there is strong motivation to determine if similar regional variations exist in the human lens capsule for knowledge of such complexities may allow us to improve the design of surgical procedures and implants.
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Affiliation(s)
- G David
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
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Pedrigi RM, David G, Dziezyc J, Humphrey JD. Regional mechanical properties and stress analysis of the human anterior lens capsule. Vision Res 2007; 47:1781-9. [PMID: 17467027 DOI: 10.1016/j.visres.2007.03.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [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: 10/18/2006] [Revised: 01/25/2007] [Indexed: 10/23/2022]
Abstract
The lens capsule of the eye functions, in part, as a deformable support through which the ciliary body applies tractions that can alter lens curvature and corresponding refractive power during the process of accommodation. Although it has long been recognized that characterization of the mechanical properties of the lens capsule is fundamental to understanding this physiologic process as well as clinical interventions, prior data have been limited by one-dimensional testing of excised specimens despite the existence of multiaxial loading in vivo. In this paper, we employ a novel experimental approach to study in situ the regional, multiaxial mechanical behavior of both normal and diabetic human anterior lens capsules. Furthermore, we use these data to calculate material parameters in a nonlinear stress-strain relation via a custom sub-domain inverse finite element method (FEM). These parameters are then used to predict capsular stresses in response to imposed loads using a forward FEM model. Our results for both normal and diabetic human eyes show that the anterior lens capsule exhibits a nonlinear pseudoelastic behavior over finite strains that is typical of soft tissues, and that strains are principal relative to meridional and circumferential directions. Experimental data and parameter estimation suggest further that the capsule is regionally anisotropic, with the circumferential direction becoming increasingly stiffer than the meridional direction towards the equator. Although both normal and diabetic lens capsules exhibited these general characteristic behaviors, diabetic capsules were significantly stiffer at each distension. Finally, the forward FEM model predicted a nearly uniform, equibiaxial stress field during normalcy that will be perturbed by cataract surgery. Such mechanical perturbations may be an underlying modulator of the sustained errant epithelial cell behavior that is observed well after cataract surgery and may ultimately contribute to opacification of the posterior lens capsule.
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Affiliation(s)
- R M Pedrigi
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
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29
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Heistand MR, Pedrigi RM, Dziezyc J, Humphrey JD. Redistribution of strain and curvature in the porcine anterior lens capsule following a continuous circular capsulorhexis. J Biomech 2006; 39:1537-42. [PMID: 16024027 DOI: 10.1016/j.jbiomech.2005.04.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [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: 01/14/2005] [Accepted: 04/13/2005] [Indexed: 11/26/2022]
Abstract
Cataract surgery is the most commonly performed surgical procedure in the US, it consists of three steps: introduction of a hole into the lens capsule, removal of the clouded lens through this access hole, and insertion of an artificial lens. We hypothesize that errant behavior by the residual epithelial cells of the lens capsule following surgery are due, in part, to surgically-induced changes of the native stress and strain fields in the lens capsule. Because the capsular bag can be regarded mechanically as a membrane, here we study changes in curvature and strains due to the most common means of introducing the initial access hole: a continuous circular capsulorhexis (CCC). We show that a modest sized CCC increases circumferential strains and decreases meridional strains by up to approximately 20% and that curvatures change by up to approximately 13%, particularly near the edge of the CCC. We submit that such changes can induce mechanobiological responses that are responsible, in part, for some of the long-term complications following cataract surgery.
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Affiliation(s)
- M R Heistand
- Department of Biomedical Engineering, Dwight Look College of Engineering, Texas A and M University, College Station, TX 77845, USA
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Heistand MR, Pedrigi RM, Delange SL, Dziezyc J, Humphrey JD. Multiaxial mechanical behavior of the porcine anterior lens capsule. Biomech Model Mechanobiol 2005; 4:168-77. [PMID: 15973538 DOI: 10.1007/s10237-005-0073-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [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: 01/14/2005] [Accepted: 04/08/2005] [Indexed: 10/25/2022]
Abstract
The biomechanics of the lens capsule of the eye is important both in physiologic processes such as accommodation and clinical treatments such as cataract surgery. Although the lens capsule experiences multiaxial stresses in vivo, there have been no measurements of its multiaxial properties or possible regional heterogeneities. Rather all prior mechanical data have come from 1-D pressure-volume or uniaxial force-length tests. Here, we report a new experimental approach to study in situ the regional, multiaxial mechanical behavior of the lens capsule. Moreover, we report multiaxial data suggesting that the porcine anterior lens capsule exhibits a typical nonlinear pseudo-elastic behavior over finite strains, that the in situ state is pre-stressed multi-axially, and that the meridional and circumferential directions are principal directions of strain, which is nearly equi-biaxial at the pole but less so towards the equator. Such data are fundamental to much needed constitutive formulations.
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Affiliation(s)
- M R Heistand
- Department of Biomedical Engineering, Texas A&M University, 337 Zachry Engineering Center 3120 TAMU, College Station, 77843-3120 TX, USA
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