101
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Yalcin HC, Shekhar A, McQuinn TC, Butcher JT. Hemodynamic patterning of the avian atrioventricular valve. Dev Dyn 2011; 240:23-35. [PMID: 21181939 DOI: 10.1002/dvdy.22512] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In this study, we develop an innovative approach to rigorously quantify the evolving hemodynamic environment of the atrioventricular (AV) canal of avian embryos. Ultrasound generated velocity profiles were imported into Micro-Computed Tomography generated anatomically precise cardiac geometries between Hamburger-Hamilton (HH) stages 17 and 30. Computational fluid dynamic simulations were then conducted and iterated until results mimicked in vivo observations. Blood flow in tubular hearts (HH17) was laminar with parallel streamlines, but strong vortices developed simultaneous with expansion of the cushions and septal walls. For all investigated stages, highest wall shear stresses (WSS) are localized to AV canal valve-forming regions. Peak WSS increased from 19.34 dynes/cm(2) at HH17 to 287.18 dynes/cm(2) at HH30, but spatiotemporally averaged WSS became 3.62 dynes/cm(2) for HH17 to 9.11 dynes/cm(2) for HH30. Hemodynamic changes often preceded and correlated with morphological changes. These results establish a quantitative baseline supporting future hemodynamic analyses and interpretations.
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Affiliation(s)
- Huseyin C Yalcin
- Department of Biomedical Engineering, Cornell University, Ithaca, New York 14853-7501, USA
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102
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Yip CYY, Simmons CA. The aortic valve microenvironment and its role in calcific aortic valve disease. Cardiovasc Pathol 2011; 20:177-82. [DOI: 10.1016/j.carpath.2010.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 12/01/2010] [Indexed: 12/01/2022] Open
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103
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Butcher JT, Mahler GJ, Hockaday LA. Aortic valve disease and treatment: the need for naturally engineered solutions. Adv Drug Deliv Rev 2011; 63:242-68. [PMID: 21281685 DOI: 10.1016/j.addr.2011.01.008] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 01/05/2011] [Accepted: 01/14/2011] [Indexed: 01/21/2023]
Abstract
The aortic valve regulates unidirectional flow of oxygenated blood to the myocardium and arterial system. The natural anatomical geometry and microstructural complexity ensures biomechanically and hemodynamically efficient function. The compliant cusps are populated with unique cell phenotypes that continually remodel tissue for long-term durability within an extremely demanding mechanical environment. Alteration from normal valve homeostasis arises from genetic and microenvironmental (mechanical) sources, which lead to congenital and/or premature structural degeneration. Aortic valve stenosis pathobiology shares some features of atherosclerosis, but its final calcification endpoint is distinct. Despite its broad and significant clinical significance, very little is known about the mechanisms of normal valve mechanobiology and mechanisms of disease. This is reflected in the paucity of predictive diagnostic tools, early stage interventional strategies, and stagnation in regenerative medicine innovation. Tissue engineering has unique potential for aortic valve disease therapy, but overcoming current design pitfalls will require even more multidisciplinary effort. This review summarizes the latest advancements in aortic valve research and highlights important future directions.
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104
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Yap CH, Saikrishnan N, Yoganathan AP. Experimental measurement of dynamic fluid shear stress on the ventricular surface of the aortic valve leaflet. Biomech Model Mechanobiol 2011; 11:231-44. [PMID: 21465260 DOI: 10.1007/s10237-011-0306-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 03/21/2011] [Indexed: 12/20/2022]
Abstract
Aortic valve (AV) calcification is a highly prevalent disease with serious impact on mortality and morbidity. The exact causes and mechanisms of AV calcification are unclear, although previous studies suggest that mechanical forces play a role. It has been clinically demonstrated that calcification preferentially occurs on the aortic surface of the AV. This is hypothesized to be due to differences in the mechanical environments on the two sides of the valve. It is thus necessary to characterize fluid shear forces acting on both sides of the leaflet to test this hypothesis. The current study is one of two studies characterizing dynamic shear stress on both sides of the AV leaflets. In the current study, shear stresses on the ventricular surface of the AV leaflets were measured experimentally on two prosthetic AV models with transparent leaflets in an in vitro pulsatile flow loop using two-component Laser Doppler Velocimetry (LDV). Experimental measurements were utilized to validate a theoretical model of AV ventricular surface shear stress based on the Womersley profile in a straight tube, with corrections for the opening angle of the valve leaflets. This theoretical model was applied to in vivo data based on MRI-derived volumetric flow rates and valve dimension obtained from the literature. Experimental results showed that ventricular surface shear stress was dominated by the streamwise component. The systolic shear stress waveform resembled a half-sinusoid during systole and peaks at 64-71 dyn/cm(2), and reversed in direction at the end of systole for 15-25 ms, and reached a significant negative magnitude of 40-51 dyn/cm(2). Shear stresses from the theoretical model applied to in vivo data showed that shear stresses peaked at 77-92 dyn/cm(2) and reversed in direction for substantial period of time (108-110 ms) during late systole with peak negative shear stress of 35-38 dyn/cm(2).
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Affiliation(s)
- Choon Hwai Yap
- Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332-0535, USA
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105
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Yap CH, Saikrishnan N, Tamilselvan G, Yoganathan AP. Experimental measurement of dynamic fluid shear stress on the aortic surface of the aortic valve leaflet. Biomech Model Mechanobiol 2011; 11:171-82. [PMID: 21416247 DOI: 10.1007/s10237-011-0301-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 03/04/2011] [Indexed: 11/30/2022]
Abstract
Aortic valve (AV) calcification is a highly prevalent disease with serious impact on mortality and morbidity. Although exact causes and mechanisms of AV calcification are unclear, previous studies suggest that mechanical forces play a role. Since calcium deposits occur almost exclusively on the aortic surfaces of AV leaflets, it has been hypothesized that adverse patterns of fluid shear stress on the aortic surface of AV leaflets promote calcification. The current study characterizes AV leaflet aortic surface fluid shear stresses using Laser Doppler velocimetry and an in vitro pulsatile flow loop. The valve model used was a native porcine valve mounted on a suturing ring and preserved using 0.15% glutaraldehyde solution. This valve model was inserted in a mounting chamber with sinus geometries, which is made of clear acrylic to provide optical access for measurements. To understand the effects of hemodynamics on fluid shear stress, shear stress was measured across a range of conditions: varying stroke volumes at the same heart rate and varying heart rates at the same stroke volume. Systolic shear stress magnitude was found to be much higher than diastolic shear stress magnitude due to the stronger flow in the sinuses during systole, reaching up to 20 dyn/cm(2) at mid-systole. Upon increasing stroke volume, fluid shear stresses increased due to stronger sinus fluid motion. Upon increasing heart rate, fluid shear stresses decreased due to reduced systolic duration that restricted the formation of strong sinus flow. Significant changes in the shear stress waveform were observed at 90 beats/min, most likely due to altered leaflet dynamics at this higher heart rate. Overall, this study represents the most well-resolved shear stress measurements to date across a range of conditions on the aortic side of the AV. The data presented can be used for further investigation to understand AV biological response to shear stresses.
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Affiliation(s)
- Choon Hwai Yap
- Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Room 2119 U. A. Whitaker Building, 313 Ferst Drive, Atlanta, GA 30332-0535, USA
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106
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Woo KV, Qu X, Babaev VR, Linton MF, Guzman RJ, Fazio S, Baldwin HS. Tie1 attenuation reduces murine atherosclerosis in a dose-dependent and shear stress-specific manner. J Clin Invest 2011; 121:1624-35. [PMID: 21383501 DOI: 10.1172/jci42040] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 01/12/2011] [Indexed: 01/11/2023] Open
Abstract
Although the response of endothelial cells to the disturbed blood flow in the vicinity of atherosclerotic lesions is known to be distinct from that elicited by nonatherogenic laminar flow, the mechanisms involved are poorly understood. Our initial studies confirmed that expression of the endothelial receptor tyrosine kinase Tie1 was evident at regions of atherogenic flow in mature animals. We therefore hypothesized that Tie1 plays a role in the endothelial response to atherogenic shear stress. Consistent with this, we found that Tie1+/- mice bred to the apoE-deficient background displayed a 35% reduction in atherosclerosis relative to Tie1+/+;Apoe-/- mice. Since deletion of Tie1 results in embryonic lethality secondary to vascular dysfunction, we used conditional and inducible mutagenesis to study the effect of endothelial-specific Tie1 attenuation on atherogenesis in Apoe-/- mice and found a dose-dependent decrease in atherosclerotic lesions. Analysis of primary aortic endothelial cells indicated that atheroprotective laminar flow decreased Tie1 expression in vitro. Attenuation of Tie1 was associated with an increase in eNOS expression and Tie2 phosphorylation. In addition, Tie1 attenuation increased IkBα expression while decreasing ICAM levels. In summary, we have found that shear stress conditions that modulate atherogenic events also regulate Tie1 expression. Therefore, Tie1 may play a novel proinflammatory role in atherosclerosis.
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Affiliation(s)
- Kel Vin Woo
- Department of Pediatrics, Division of Cardiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0439, USA
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107
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Miragoli M, Moshkov A, Novak P, Shevchuk A, Nikolaev VO, El-Hamamsy I, Potter CMF, Wright P, Kadir SHSA, Lyon AR, Mitchell JA, Chester AH, Klenerman D, Lab MJ, Korchev YE, Harding SE, Gorelik J. Scanning ion conductance microscopy: a convergent high-resolution technology for multi-parametric analysis of living cardiovascular cells. J R Soc Interface 2011; 8:913-25. [PMID: 21325316 PMCID: PMC3104336 DOI: 10.1098/rsif.2010.0597] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiovascular diseases are complex pathologies that include alterations of various cell functions at the levels of intact tissue, single cells and subcellular signalling compartments. Conventional techniques to study these processes are extremely divergent and rely on a combination of individual methods, which usually provide spatially and temporally limited information on single parameters of interest. This review describes scanning ion conductance microscopy (SICM) as a novel versatile technique capable of simultaneously reporting various structural and functional parameters at nanometre resolution in living cardiovascular cells at the level of the whole tissue, single cells and at the subcellular level, to investigate the mechanisms of cardiovascular disease. SICM is a multimodal imaging technology that allows concurrent and dynamic analysis of membrane morphology and various functional parameters (cell volume, membrane potentials, cellular contraction, single ion-channel currents and some parameters of intracellular signalling) in intact living cardiovascular cells and tissues with nanometre resolution at different levels of organization (tissue, cellular and subcellular levels). Using this technique, we showed that at the tissue level, cell orientation in the inner and outer aortic arch distinguishes atheroprone and atheroprotected regions. At the cellular level, heart failure leads to a pronounced loss of T-tubules in cardiac myocytes accompanied by a reduction in Z-groove ratio. We also demonstrated the capability of SICM to measure the entire cell volume as an index of cellular hypertrophy. This method can be further combined with fluorescence to simultaneously measure cardiomyocyte contraction and intracellular calcium transients or to map subcellular localization of membrane receptors coupled to cyclic adenosine monophosphate production. The SICM pipette can be used for patch-clamp recordings of membrane potential and single channel currents. In conclusion, SICM provides a highly informative multimodal imaging platform for functional analysis of the mechanisms of cardiovascular diseases, which should facilitate identification of novel therapeutic strategies.
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Affiliation(s)
- Michele Miragoli
- Cardiovascular Science, National Heart and Lung Institute, Imperial College London, , Dovehouse Street, London SW36LY, UK
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108
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Ferdous Z, Jo H, Nerem RM. Differences in valvular and vascular cell responses to strain in osteogenic media. Biomaterials 2011; 32:2885-93. [PMID: 21284997 DOI: 10.1016/j.biomaterials.2011.01.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 01/12/2011] [Indexed: 10/18/2022]
Abstract
Calcification is the primary cause of failure of bioprosthetic and tissue-engineered vascular and valvular grafts. We used tissue-engineered collagen gels containing human aortic smooth muscle cells (HASMC) and human aortic valvular interstitial cells (HAVIC) as a model to investigate cell-mediated differences in early markers of calcification. The HASMCs and HAVICs were isolated from non-sclerotic human tissues. After 21 days of culture in either regular or osteogenic media with or without 10% cyclic strain at 1 Hz, the collagen gels were assessed for DNA content, collagen I, matrix metalloproteinase (MMP)-2 and glycosaminoglycan (GAG) content. The collagen gels containing HASMCs contained significantly greater amounts of collagen I and GAG compared to HAVICs. Although strain increased MMP-2 activity for both cell types, this trend was significant (p ≤ 0.05) only for HAVICs. Cultured gels were also assessed for osteogenic markers calcium content, alkaline phosphatase (ALP), and Runx2 and were present at greater amounts in gels containing HASMCs than HAVICs. Calcium content, Runx2 expression, and ALP activity were also modulated by mechanical strain. The results indicate that cell-mediated differences exist between the vascular and valvular calcification processes. Further investigation is necessary for improved understanding and to detect biomarkers for early detection or prevention of these diseases.
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Affiliation(s)
- Zannatul Ferdous
- Institute of Bioengineering and Biosciences, Georgia Institute of Technology, 315 Ferst Drive, Mail code 0363, Atlanta, GA 30332, USA.
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109
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Chiu JJ, Chien S. Effects of disturbed flow on vascular endothelium: pathophysiological basis and clinical perspectives. Physiol Rev 2011; 91:327-87. [PMID: 21248169 PMCID: PMC3844671 DOI: 10.1152/physrev.00047.2009] [Citation(s) in RCA: 1416] [Impact Index Per Article: 108.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Vascular endothelial cells (ECs) are exposed to hemodynamic forces, which modulate EC functions and vascular biology/pathobiology in health and disease. The flow patterns and hemodynamic forces are not uniform in the vascular system. In straight parts of the arterial tree, blood flow is generally laminar and wall shear stress is high and directed; in branches and curvatures, blood flow is disturbed with nonuniform and irregular distribution of low wall shear stress. Sustained laminar flow with high shear stress upregulates expressions of EC genes and proteins that are protective against atherosclerosis, whereas disturbed flow with associated reciprocating, low shear stress generally upregulates the EC genes and proteins that promote atherogenesis. These findings have led to the concept that the disturbed flow pattern in branch points and curvatures causes the preferential localization of atherosclerotic lesions. Disturbed flow also results in postsurgical neointimal hyperplasia and contributes to pathophysiology of clinical conditions such as in-stent restenosis, vein bypass graft failure, and transplant vasculopathy, as well as aortic valve calcification. In the venous system, disturbed flow resulting from reflux, outflow obstruction, and/or stasis leads to venous inflammation and thrombosis, and hence the development of chronic venous diseases. Understanding of the effects of disturbed flow on ECs can provide mechanistic insights into the role of complex flow patterns in pathogenesis of vascular diseases and can help to elucidate the phenotypic and functional differences between quiescent (nonatherogenic/nonthrombogenic) and activated (atherogenic/thrombogenic) ECs. This review summarizes the current knowledge on the role of disturbed flow in EC physiology and pathophysiology, as well as its clinical implications. Such information can contribute to our understanding of the etiology of lesion development in vascular niches with disturbed flow and help to generate new approaches for therapeutic interventions.
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Affiliation(s)
- Jeng-Jiann Chiu
- Division of Medical Engineering Research, National Health Research Institutes, Taiwan
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110
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Abstract
Heart valves are solely responsible for maintaining unidirectional blood flow through the cardiovascular system. These thin, fibrous tissues are subjected to significant mechanical stresses as they open and close several billion times over a lifespan. The incredible endurance of these tissues is due to the resident valvular endothelial (VEC) and interstitial cells (VIC) that constantly repair and remodel in response to local mechanical and biological signals. Only recently have we begun to understand the unique behaviors of these cells, for which in vitro experimentation has played a key role. Particularly challenging is the isolation and culture of VEC. Special care must be used from the moment the tissue is removed from the host through final plating. Here we present protocols for direct isolation, side specific isolation, culture, and verification of pure populations of VEC. We use enzymatic digestion followed by a gentle swab scraping technique to dislodge only surface cells. These cells are then collected into a tube and centrifuged into a pellet. The pellet is then resuspended and plated into culture flasks pre-coated with collagen I matrix. VEC phenotype is confirmed by contact inhibited growth and the expression of endothelial specific markers such as PECAM1 (CD31), Von Willebrand Factor (vWF), and negative expression of alpha-smooth muscle actin (α-SMA). The functional characteristics of VEC are associated with high levels of acetylated LDL. Unlike vascular endothelial cells, VEC have the unique capacity to transform into mesenchyme, which normally occurs during embryonic valve formation. This can also occur during significantly prolonged post confluent in vitro culture, so care should be made to passage at or near confluence. After VEC isolation, pure populations of VIC can then be easily acquired.
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111
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Hermans H, Herijgers P, Holvoet P, Verbeken E, Meuris B, Flameng W, Herregods MC. Statins for calcific aortic valve stenosis: into oblivion after SALTIRE and SEAS? An extensive review from bench to bedside. Curr Probl Cardiol 2010; 35:284-306. [PMID: 20451759 DOI: 10.1016/j.cpcardiol.2010.02.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Calcific aortic stenosis is the most frequent heart valve disease and the main indication for valve replacement in western countries. For centuries attributed to a passive wear and tear process, it is now recognized that aortic stenosis is an active inflammatory and potentially modifiable pathology, with similarities to atherosclerosis. Statins were first-line candidates for slowing down progression of the disease, as established drugs in primary and secondary cardiovascular prevention. Despite promising animal experiments and nonrandomized human trials, the prospective randomized trials SEAS and SALTIRE did not confirm the expected benefit. We review SEAS and SALTIRE starting with the preceding studies and discuss basic science experiments covering the major known contributors to the pathophysiology of calcific aortic valve disease, to conclude with a hypothesis on the absent effect of statins, and suggestions for further research paths.
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112
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Berry JL, Steen JA, Koudy Williams J, Jordan JE, Atala A, Yoo JJ. Bioreactors for Development of Tissue Engineered Heart Valves. Ann Biomed Eng 2010; 38:3272-9. [DOI: 10.1007/s10439-010-0148-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Accepted: 12/30/2009] [Indexed: 01/14/2023]
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113
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Burridge KA, Friedman MH. Environment and vascular bed origin influence differences in endothelial transcriptional profiles of coronary and iliac arteries. Am J Physiol Heart Circ Physiol 2010; 299:H837-46. [PMID: 20543076 PMCID: PMC2944485 DOI: 10.1152/ajpheart.00002.2010] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 06/10/2010] [Indexed: 12/20/2022]
Abstract
Atherosclerotic plaques tend to form in the major arteries at certain predictable locations. As these arteries vary in atherosusceptibility, interarterial differences in endothelial cell biology are of considerable interest. To explore the origin of differences observed between typical atheroprone and atheroresistant arteries, we used DNA microarrays to compare gene expression profiles of harvested porcine coronary (CECs) and iliac artery endothelial cells (IECs) grown in static culture out to passage 4. Fewer differences were observed between the transcriptional profiles of CECs and IECs in culture compared with in vivo, suggesting that most differences observed in vivo were due to distinct environmental cues in the two arteries. One-class significance of microarrays revealed that most in vivo interarterial differences disappeared in culture, as fold differences after passaging were not significant for 85% of genes identified as differentially expressed in vivo at 5% false discovery rate. However, the three homeobox genes, HOXA9, HOXA10, and HOXD3, remained underexpressed in coronary endothelium for all passages by at least nine-, eight-, and twofold, respectively. Continued differential expression, despite removal from the in vivo environment, suggests that primarily heritable or epigenetic mechanism(s) influences transcription of these three genes. Quantitative real-time polymerase chain reaction confirmed expression ratios for seven genes associated with atherogenesis and over- or underexpressed by threefold in CECs relative to IECs. The present study provides evidence that both local environment and vascular bed origin modulate gene expression in arterial endothelium. The transcriptional differences observed here may provide new insights into pathways responsible for coronary artery susceptibility.
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Affiliation(s)
- Kelley A Burridge
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
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114
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Abstract
Drug-induced valvulopathy is a serious liability for certain compound classes in development and for some marketed drugs intended for human use. Reports of valvulopathy led to the withdrawal of fenfluramines (anorexigens) and pergolide (antiparkinson drug) from the United States market in 1997 and 2007, respectively. The mechanism responsible for the pathogenesis of valvulopathy by these drugs is likely a result of an "off-target" effect via activation of 5-hydroxytryptamine (5-HT) 2B receptor (5-HT2BR) expressed on heart valve leaflets. Microscopically, the affected valve leaflets showed plaques of proliferative myofibroblasts in an abundant extracellular matrix, composed primarily of glycosaminoglycans. However, the valvular effects caused by fenfluramines and pergolide were not initially predicted from routine preclinical toxicity studies, and to date there are no specific validated animal models or preclinical/toxicologic screens to accurately predict drug-induced valvulopathy. This review covers the structure and function of heart valves and highlights major advances toward understanding the 5-HT2BR-mediated pathogenesis of the lesion and subsequently, development of appropriate animal models using novel techniques/experiments, use of functional screens against 5-HT2BR, and more consistent sampling and pathologic evaluation of valves in preclinical studies that will aid in avoidance of future drug-induced valvulopathy in humans.
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115
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Yalcin HC, Shekhar A, Nishimura N, Rane AA, Schaffer CB, Butcher JT. Two-photon microscopy-guided femtosecond-laser photoablation of avian cardiogenesis: noninvasive creation of localized heart defects. Am J Physiol Heart Circ Physiol 2010; 299:H1728-35. [PMID: 20709864 DOI: 10.1152/ajpheart.00495.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Embryonic heart formation is driven by complex feedback between genetic and hemodynamic stimuli. Clinical congenital heart defects (CHD), however, often manifest as localized microtissue malformations with no underlying genetic mutation, suggesting that altered hemodynamics during embryonic development may play a role. An investigation of this relationship has been impaired by a lack of experimental tools that can create locally targeted cardiac perturbations. Here we have developed noninvasive optical techniques that can modulate avian cardiogenesis to dissect relationships between alterations in mechanical signaling and CHD. We used two-photon excited fluorescence microscopy to monitor cushion and ventricular dynamics and femtosecond pulsed laser photoablation to target micrometer-sized volumes inside the beating chick hearts. We selectively photoablated a small (∼100 μm radius) region of the superior atrioventricular (AV) cushion in Hamburger-Hamilton 24 chick embryos. We quantified via ultrasound that the disruption causes AV regurgitation, which resulted in a venous pooling of blood and severe arterial constriction. At 48 h postablation, quantitative X-ray microcomputed tomography imaging demonstrated stunted ventricular growth and pronounced left atrial dilation. A histological analysis demonstrated that the laser ablation produced defects localized to the superior AV cushion: a small quasispherical region of cushion tissue was completely obliterated, and the area adjacent to the myocardial wall was less cellularized. Both cushions and myocardium were significantly smaller than sham-operated controls. Our results highlight that two-photon excited fluorescence coupled with femtosecond pulsed laser photoablation should be considered a powerful tool for studying hemodynamic signaling in cardiac morphogenesis through the creation of localized microscale defects that may mimic clinical CHD.
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Affiliation(s)
- Huseyin C Yalcin
- Department of Biomedical Engineering, Cornell University, Ithaca, New York 14853, USA
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116
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Hoehn D, Sun L, Sucosky P. Role of Pathologic Shear Stress Alterations in Aortic Valve Endothelial Activation. Cardiovasc Eng Technol 2010. [DOI: 10.1007/s13239-010-0015-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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117
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Hakuno D, Kimura N, Yoshioka M, Mukai M, Kimura T, Okada Y, Yozu R, Shukunami C, Hiraki Y, Kudo A, Ogawa S, Fukuda K. Periostin advances atherosclerotic and rheumatic cardiac valve degeneration by inducing angiogenesis and MMP production in humans and rodents. J Clin Invest 2010; 120:2292-306. [PMID: 20551517 DOI: 10.1172/jci40973] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 04/21/2010] [Indexed: 12/19/2022] Open
Abstract
Valvular heart disease (VHD) is the term given to any disease process involving one or more of the heart valves. The condition can be congenital or acquired, for example as a result of atherosclerosis or rheumatic fever. Despite its clinical importance, the molecular mechanisms underlying VHD remain unknown. We investigated the pathophysiologic role and molecular mechanism of periostin, a protein that plays critical roles in cardiac valve development, in degenerative VHD. Unexpectedly, we found that periostin levels were drastically increased in infiltrated inflammatory cells and myofibroblasts in areas of angiogenesis in human atherosclerotic and rheumatic VHD, whereas periostin was localized to the subendothelial layer in normal valves. The expression patterns of periostin and chondromodulin I, an angioinhibitory factor that maintains cardiac valvular function, were mutually exclusive. In WT mice, a high-fat diet markedly increased aortic valve thickening, annular fibrosis, and MMP-2 and MMP-13 expression levels, concomitant with increased periostin expression; these changes were attenuated in periostin-knockout mice. In vitro and ex vivo studies revealed that periostin promoted tube formation and mobilization of ECs. Furthermore, periostin prominently increased MMP secretion from cultured valvular interstitial cells, ECs, and macrophages in a cell type-specific manner. These findings indicate that, in contrast to chondromodulin I, periostin plays an essential role in the progression of cardiac valve complex degeneration by inducing angiogenesis and MMP production.
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Affiliation(s)
- Daihiko Hakuno
- Department of Regenerative Medicine and Advanced Cardiac Therapeutics, Keio University School of Medicine, Tokyo 160-8582, Japan
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118
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Einstein DR, Del Pin F, Jiao X, Kuprat AP, Carson JP, Kunzelman KS, Cochran RP, Guccione JM, Ratcliffe MB. Fluid-Structure Interactions of the Mitral Valve and Left Heart: Comprehensive Strategies, Past, Present and Future. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2010; 26:348-380. [PMID: 20454531 PMCID: PMC2864615 DOI: 10.1002/cnm.1280] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The remodeling that occurs after a posterolateral myocardial infarction can alter mitral valve function by creating conformational abnormalities in the mitral annulus and in the posteromedial papillary muscle, leading to mitral regurgitation (MR). It is generally assumed that this remodeling is caused by a volume load and is mediated by an increase in diastolic wall stress. Thus, mitral regurgitation can be both the cause and effect of an abnormal cardiac stress environment. Computational modeling of ischemic MR and its surgical correction is attractive because it enables an examination of whether a given intervention addresses the correction of regurgitation (fluid-flow) at the cost of abnormal tissue stress. This is significant because the negative effects of an increased wall stress due to the intervention will only be evident over time. However, a meaningful fluid-structure interaction model of the left heart is not trivial; it requires a careful characterization of the in-vivo cardiac geometry, tissue parameterization though inverse analysis, a robust coupled solver that handles collapsing Lagrangian interfaces, automatic grid-generation algorithms that are capable of accurately discretizing the cardiac geometry, innovations in image analysis, competent and efficient constitutive models and an understanding of the spatial organization of tissue microstructure. In this manuscript, we profile our work toward a comprehensive fluid-structure interaction model of the left heart by reviewing our early work, presenting our current work and laying out our future work in four broad categories: data collection, geometry, fluid-structure interaction and validation.
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Affiliation(s)
- Daniel R. Einstein
- Biological Monitoring & Modeling, Pacific Northwest National Laboratory, Richland, WA. {,,
| | | | - Xiangmin Jiao
- Department of Applied Mathematics & Statistics, Stony Brook University, Stony Brook, NY.
| | - Andrew P. Kuprat
- Biological Monitoring & Modeling, Pacific Northwest National Laboratory, Richland, WA. {,,
| | - James P. Carson
- Biological Monitoring & Modeling, Pacific Northwest National Laboratory, Richland, WA. {,,
| | | | | | - Julius M. Guccione
- Department of Surgery, San Francisco VA Medical Center, San Francisco, CA. ,
| | - Mark B. Ratcliffe
- Department of Surgery, San Francisco VA Medical Center, San Francisco, CA. ,
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119
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El-Hamamsy I, Chester AH, Yacoub MH. Cellular regulation of the structure and function of aortic valves. J Adv Res 2010. [DOI: 10.1016/j.jare.2010.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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120
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Xu S, Liu AC, Gotlieb AI. Common pathogenic features of atherosclerosis and calcific aortic stenosis: role of transforming growth factor-beta. Cardiovasc Pathol 2009; 19:236-47. [PMID: 19942455 DOI: 10.1016/j.carpath.2009.09.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Revised: 09/22/2009] [Accepted: 09/24/2009] [Indexed: 12/20/2022] Open
Abstract
Calcific aortic stenosis and atherosclerosis have been investigated separately in experimental in vitro and in vivo studies and in clinical studies. The similarities identified in both diseases suggest that similar pathogenic pathways are involved in both conditions. Most current therapeutic studies are focused on statins. The evidence suggests that statin effects on valves may, in large part, be independent of the lipid lowering effects of the drug. There are several molecules that play significant regulatory roles on the development and progression of valve sclerosis and calcification and on growth and complications of atherosclerotic plaques. The purpose of this review is to discuss the pathogenic features of the two conditions, highlight the important similarities, and then review the data that suggest that transforming growth factor-beta may play a key regulatory role in both diseases and that this is worthy of study as a potential therapeutic target for both conditions.
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Affiliation(s)
- Songyi Xu
- Toronto General Research Institute and Laboratory Medicine Program, University Health Network, Toronto, ON, Canada
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121
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Guerraty MA, Grant GR, Karanian JW, Chiesa OA, Pritchard WF, Davies PF. Hypercholesterolemia induces side-specific phenotypic changes and peroxisome proliferator-activated receptor-gamma pathway activation in swine aortic valve endothelium. Arterioscler Thromb Vasc Biol 2009; 30:225-31. [PMID: 19926833 DOI: 10.1161/atvbaha.109.198549] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
UNLABELLED Background- The endothelium of healthy aortic valves expresses different phenotypes on the aortic and ventricular sides. On the aortic side, which is susceptible to aortic valve sclerosis, there is a balanced coexpression of both propathological and protective pathways. Side-specific global gene expression can address endothelial phenotype balance in early aortic valve sclerosis. METHODS AND RESULTS Adult male swine were fed a hypercholesterolemic or an isocaloric normal diet for 2-week and 6-month periods. Hypercholesterolemia induced localized lipid insudation confined to the aortic side of the leaflet. Transcript profiling of valve endothelial populations showed that the susceptible aortic side was more sensitive to 2-week hypercholesterolemia than the ventricular side (1,325 vs 87 genes were differentially expressed). However, greater sensitivity was not evidence of a dysfunctional phenotype. Instead, pathway analyses identified differential expression of caspase 3-, peroxisome proliferator-activated receptor gamma-, TNF-alpha-, and nuclear factor-kappaB-related pathways that were consistent with a protective endothelial phenotype. This was confirmed at the protein level at 2 weeks and persisted at 6 months. CONCLUSIONS In a large animal model at high spatial resolution, endothelium on the pathosusceptible side of the aortic valve leaflet is responsive to hypercholesterolemia. Transcript profiles indicative of a protective phenotype were induced and persisted on the side prone to aortic valve sclerosis.
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Affiliation(s)
- Marie A Guerraty
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia 19104, USA
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122
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Yap CH, Kim HS, Balachandran K, Weiler M, Haj-Ali R, Yoganathan AP. Dynamic deformation characteristics of porcine aortic valve leaflet under normal and hypertensive conditions. Am J Physiol Heart Circ Physiol 2009; 298:H395-405. [PMID: 19915178 DOI: 10.1152/ajpheart.00040.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Calcific aortic valve (AV) disease has a high prevalence in the United States, and hypertension is correlated to early onset of the disease. The cause of the disease is poorly understood, although biological and remodeling responses to mechanical forces, such as membrane tension, have been hypothesized to play a role. The mechanical behavior of the native AV has, therefore, been the focus of many recent studies. In the present study, the dynamic deformation characteristics of the AV leaflet and the effects of hypertension on leaflet deformation are quantified. Whole porcine aortic roots were trimmed and mounted in an in vitro pulsatile flow loop and subjected to normal (80/120 mmHg), hypertensive (120/160 mmHg), or severe hypertensive (150/190 mmHg) conditions. Local valve leaflet deformations were calculated with dual-camera photogrammetry method: by tracking the motion of markers placed on the AV leaflets in three dimensions and calculating their spatial deformations. The results demonstrate that, first, during diastole, high transvalvular pressure induces a stretch waveform which plateaus over the diastolic duration in both circumferential and radial directions. During systole, the leaflet stretches in the radial direction due to forward flow drag forces but compresses in the circumferential direction in a manner in agreement with Poisson's effect. Second, average diastolic and systolic stretch ratios were quantified in the radial and circumferential directions in the base and belly region of the leaflet, and diastolic stretch was found to increase with increasing pressure conditions.
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Affiliation(s)
- Choon Hwai Yap
- School of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA
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123
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Farcas MA, Rouleau L, Fraser R, Leask RL. The development of 3-D, in vitro, endothelial culture models for the study of coronary artery disease. Biomed Eng Online 2009; 8:30. [PMID: 19863806 PMCID: PMC2773771 DOI: 10.1186/1475-925x-8-30] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 10/28/2009] [Indexed: 02/04/2023] Open
Abstract
The response of the vascular endothelium to wall shear stress plays a central role in the development and progression of atherosclerosis. Current studies have investigated endothelial response using idealized in vitro flow chambers. Such cell culture models are unable to accurately replicate the complex in vivo wall shear stress patterns arising from anatomical geometries. To better understand this implication, we have created both simplified/tubular and anatomically realistic in vitro endothelial flow models of the human right coronary artery. A post-mortem vascular cast of the human left ventricular outflow tract was used to create geometrically accurate silicone elastomer models. Straight, tubular models were created using a custom made mold. Following the culture of human abdominal aortic endothelial cells within the inner lumen, cells were exposed to steady flow (Re = 233) for varying time periods. The resulting cell morphology was analyzed in terms of shape index and angle of orientation relative to the flow direction. In both models a progressive elongation and alignment of the endothelium in the flow direction was observed following 8, 12, and 24 hours. This change, however, was significantly less pronounced in the anatomical model (as observed from morphological variations indicative of localized flow features). Differences were also observed between the inner and outer walls at the disease-prone proximal region. Since morphological adaptation is a visual indication of endothelial shear stress activation, the use of anatomical models in endothelial genetic and biochemical studies may offer better insight into the disease process.
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Affiliation(s)
- Monica A Farcas
- Department of Chemical Engineering, McGill University, Montreal, Canada.
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124
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Carson JP, Kuprat AP, Jiao X, Dyedov V, Del Pin F, Guccione JM, Ratcliffe MB, Einstein DR. Adaptive generation of multimaterial grids from imaging data for biomedical Lagrangian fluid-structure simulations. Biomech Model Mechanobiol 2009; 9:187-201. [PMID: 19727874 DOI: 10.1007/s10237-009-0170-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 08/10/2009] [Indexed: 11/24/2022]
Abstract
Spatial discretization of complex imaging- derived fluid-solid geometries, such as the cardiac environment, is a critical but often overlooked challenge in biomechanical computations. This is particularly true in problems with Lagrangian interfaces, where the fluid and solid phases share a common interface geometrically. For simplicity and better accuracy, it is also highly desirable for the two phases to have a matching surface mesh at the interface between them. We outline a method for solving this problem, and illustrate the approach with a 3D fluid-solid mesh of the mouse heart. An MRI dataset of a perfusion-fixed mouse heart with 50 microm isotropic resolution was semi-automatically segmented using a customized multimaterial connected-threshold approach that divided the volume into non-overlapping regions of blood, tissue, and background. Subsequently a multimaterial marching cubes algorithm was applied to the segmented data to produce two detailed, compatible isosurfaces, one for blood and one for tissue. Both isosurfaces were simultaneously smoothed with a multimaterial smoothing algorithm that exactly conserves the volume for each phase. Using these two isosurfaces, we developed and applied novel automated meshing algorithms to generate anisotropic hybrid meshes on arbitrary biological geometries with the number of layers and the desired element anisotropy for each phase as the only input parameters. Since our meshes adapt to the local feature sizes and include boundary layer prisms, they are more efficient and accurate than non-adaptive, isotropic meshes, and the fluid-structure interaction computations will tend to have relative error equilibrated over the whole mesh.
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Affiliation(s)
- James P Carson
- Biological Monitoring and Modeling, Pacific Northwest National Laboratory, Richland, WA, USA.
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125
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Abstract
This article discusses the importance of the endothelium for successful vascular grafts derived from both native arteries and synthetic materials. It also discusses the fundamental strategies to endothelialize synthetic grafts in animal experiments and in the clinic, as well as the use of endothelial progenitor cells (EPCs), bone marrow-derived cells, and mesothelium as endothelial substitutes.
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Affiliation(s)
- Michel R Hoenig
- Centre for Research in Vascular Biology, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Australia
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126
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Csiszar A, Lehoux S, Ungvari Z. Hemodynamic forces, vascular oxidative stress, and regulation of BMP-2/4 expression. Antioxid Redox Signal 2009; 11:1683-97. [PMID: 19320562 PMCID: PMC2842584 DOI: 10.1089/ars.2008.2401] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Changes in the hemodynamic environment (e.g., hypertension, disturbed-flow conditions) are known to promote atherogenesis by inducing proinflammatory phenotypic alterations in endothelial and smooth muscle cells; however, the mechanisms underlying mechanosensitive induction of inflammatory gene expression are not completely understood. Bone morphogenetic protein-2 and -4 (BMP-2/4) are TGF-beta superfamily cytokines that are expressed by both endothelial and smooth muscle cells and regulate a number of cellular processes involved in atherogenesis, including vascular calcification and endothelial activation. This review considers how hemodynamic forces regulate BMP-2/4 expression and explores the role of mechanosensitive generation of reactive oxygen species by NAD(P)H oxidases in the control of BMP signaling.
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Affiliation(s)
- Anna Csiszar
- Department of Physiology, New York Medical College, Valhalla, New York, USA
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127
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El-Hamamsy I, Balachandran K, Yacoub MH, Stevens LM, Sarathchandra P, Taylor PM, Yoganathan AP, Chester AH. Endothelium-dependent regulation of the mechanical properties of aortic valve cusps. J Am Coll Cardiol 2009; 53:1448-55. [PMID: 19371829 DOI: 10.1016/j.jacc.2008.11.056] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 11/05/2008] [Accepted: 11/06/2008] [Indexed: 11/30/2022]
Abstract
OBJECTIVES The aim of this study was to evaluate the role of valve endothelium in regulating the mechanical properties of aortic valve cusps. BACKGROUND Mechanical properties of valve cusps are key to their function and durability; however, little is known about the regulation of valve biomechanics. METHODS Mechanical properties of porcine aortic valve leaflets were evaluated in response to serotonin (5-hydroxytryptamine [5-HT]), with and without N-nitro-L-arginine-methyl-ester (L-NAME) or endothelial denudation, and endothelin (ET)-1, with and without cytochalasin-B. RESULTS Under physiological loading conditions, 5-HT induced a decrease in the areal stiffness of the cusp (-25.0 +/- 4.0%; p < 0.01 vs. control), which was reversed by L-NAME or endothelial denudation (+17.5 +/- 5.3%, p = 0.07, and +14.7 +/- 1.8%, p < 0.05 vs. control, respectively). ET-1 caused an increase in stiffness (+34.4 +/- 13.8%; p < 0.05 vs. control), but not in the presence of cytochalasin-B (p = 0.29 vs. control). Changes in cusp stiffness were accompanied by aortic cusp relaxations to 5-HT (-0.29% +/- 0.1% change in load per 10-fold increase in 5-HT concentration; p = 0.03), which were reversed by endothelial denudation (+0.29 +/- 0.06% change in load per 10-fold increase in 5-HT concentration; p = 0.02) and by L-NAME (p < 0.05). Valve cusps contracted in response to ET-1 (+0.29 +/- 0.08% change in load per 10-fold increase in ET-1 concentration; p = 0.02), which was inhibited by cytochalasin-B. CONCLUSIONS These data highlight the role of the endothelium in regulating the mechanical properties of aortic valve cusps and underline the importance of valve cellular integrity for optimal valve function.
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Affiliation(s)
- Ismail El-Hamamsy
- Tissue Engineering Department, Harefield Heart Science Centre, National Heart and Lung Institute, Imperial College London, Harefield, United Kingdom
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128
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Dasi LP, Sucosky P, De Zelicourt D, Sundareswaran K, Jimenez J, Yoganathan AP. Advances in Cardiovascular Fluid Mechanics: Bench to Bedside. Ann N Y Acad Sci 2009; 1161:1-25. [DOI: 10.1111/j.1749-6632.2008.04320.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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130
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Calin MV, Manduteanu I, Dragomir E, Dragan E, Nicolae M, Gan AM, Simionescu M. Effect of depletion of monocytes/macrophages on early aortic valve lesion in experimental hyperlipidemia. Cell Tissue Res 2009; 336:237-48. [PMID: 19301037 DOI: 10.1007/s00441-009-0765-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 12/16/2008] [Indexed: 11/24/2022]
Abstract
Monocytes/macrophages are key players throughout atheroma development. The aim of this study was to determine the role of macrophages in lesion formation in heart valves in hyperlipidemia. We examined whether systemic depletion of monocytes/macrophages had a beneficial or adverse effect on the development of lesions in hyperlipemic hamsters injected twice weekly (for 2 months) with clodronate-encapsulated liposomes (H+Lclod), a treatment that selectively induces significant monocyte apoptosis. Hyperlipemic hamsters were employed as controls, as were hyperlipemic hamsters treated with plain liposomes. We assayed serum cholesterol (CH) and triglycerides (TG), the lipid and collagen contents and the size of the valve lesions, the matrix metalloproteinases (MMPs) in the serum and vessel wall, apolipoprotein E (ApoE), interleukin-1beta (IL-1beta), and superoxide anion production. In comparison with controls, H+Lclod hamsters exhibited: (1) increased lipid and collagen accumulation within the lesions, (2) decreased activity of MMP-9 and MMP-2 in sera and aortic homogenates, (3) decreased serum CH and TG and decreased expression of ApoE in sera and liver, (4) reduced expression of IL-1beta in aorta and liver homogenates, and (5) no change in the level of superoxide anion in the aorta. Thus, initially, the presence of the macrophages is beneficial in valvular lesion formation. Depletion of monocytes/macrophages is a two-edged sword having a beneficial effect by decreasing the expression of IL-1beta and MMP activities but an adverse effect by inducing a significant increase in the lipid and collagen content and expansion of valvular lesions.
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Affiliation(s)
- Manuela Voinea Calin
- Institute of Cellular Biology and Pathology Nicolae Simionescu, Bucharest, Romania.
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131
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132
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Schoen FJ. Evolving concepts of cardiac valve dynamics: the continuum of development, functional structure, pathobiology, and tissue engineering. Circulation 2008; 118:1864-80. [PMID: 18955677 DOI: 10.1161/circulationaha.108.805911] [Citation(s) in RCA: 269] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Considerable progress has been made in recent years toward elucidating a conceptual framework that integrates the dynamic functional structure, mechanical properties, and pathobiological behavior of the cardiac valves. This communication reviews the evolving paradigm of a continuum of heart valve structure, function, and pathobiology and explores its implications. Specifically, we discuss (1) the interactions of valve biology and biomechanics (eg, correlations of function with structure at the cell, tissue, and organ levels and mechanical considerations, development, endothelial cell and interstitial cell biology, extracellular matrix biology, homeostasis, and adaptation to environmental change); (2) mechanisms of disease (eg, valve cell and matrix pathobiology in congenital anomalies, aortic valve calcification, and mitral valve prolapse); (3) considerations in replacement and repair (eg, cell/matrix biology of tissue valve substitutes and their degeneration and durability of repairs); and (4) the potential for tissue engineering approaches to therapeutic regeneration of the cardiac valves. Opportunities for research and clinical translation are highlighted.
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Affiliation(s)
- Frederick J Schoen
- Department of Pathology, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115, USA.
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133
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Sucosky P, Balachandran K, Elhammali A, Jo H, Yoganathan AP. Altered shear stress stimulates upregulation of endothelial VCAM-1 and ICAM-1 in a BMP-4- and TGF-beta1-dependent pathway. Arterioscler Thromb Vasc Biol 2008; 29:254-60. [PMID: 19023092 DOI: 10.1161/atvbaha.108.176347] [Citation(s) in RCA: 183] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
OBJECTIVE Hemodynamics has been associated with aortic valve (AV) inflammation, but the underlying mechanisms are not well understood. Here we tested the hypothesis that altered shear stress conditions stimulate the expression of cytokines and adhesion molecules in AV leaflets via a bone morphogenic protein (BMP)- and transforming growth fact (TGF)-beta1-dependent pathway. METHODS AND RESULTS The ventricularis or aortic surface of porcine AV leaflets were exposed for 48 hours to unidirectional pulsatile and bidirectional oscillatory shear stresses ex vivo. Immunohistochemistry was performed to detect expressions of the 4 inflammatory markers VCAM-1, ICAM-1, BMP-4, and TGF-beta1. Exposure of the aortic surface to pulsatile shear stress (altered hemodynamics), but not oscillatory shear stress, increased expression of the inflammatory markers. In contrast, neither pulsatile nor oscillatory shear stress affected expression of the inflammatory markers on the ventricularis surface. The shear stress-dependent expression of VCAM-1, ICAM-1, and BMP-4, but not TGF-beta1, was significantly reduced by the BMP inhibitor noggin, whereas the TGF-beta1 inhibitor SB431542 blocked BMP-4 expression on the aortic surface exposed to pulsatile shear stress. CONCLUSIONS The results demonstrate that altered hemodynamics stimulates the expression of AV leaflet endothelial adhesion molecules in a TGF-beta1- and BMP-4-dependent manner, providing some potential directions for future drug-based therapies for AV diseases.
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Affiliation(s)
- Philippe Sucosky
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556-5637, USA.
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134
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Zhang J, Burridge KA, Friedman MH. In vivo differences between endothelial transcriptional profiles of coronary and iliac arteries revealed by microarray analysis. Am J Physiol Heart Circ Physiol 2008; 295:H1556-61. [PMID: 18689496 PMCID: PMC2593512 DOI: 10.1152/ajpheart.00540.2008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Accepted: 08/04/2008] [Indexed: 12/21/2022]
Abstract
Endothelial cells (ECs) from different vascular beds display a remarkable heterogeneity in both structure and function. Phenotypic heterogeneity among arterial ECs is particularly relevant to atherosclerosis since the disease occurs predominantly in major arteries, which vary in their atherosusceptibility. To explore EC heterogeneity between typical atheroprone and atheroresistant arteries, we used DNA microarrays to compare gene expression profiles of freshly harvested porcine coronary (CECs) and iliac artery (IECs) ECs. Statistical analysis revealed 51 genes that were differentially expressed in CECs relative to IECs at a false discovery rate of 5%. Seventeen of these genes are known to be involved in atherogenesis. Consistent with coronary arteries being more atherosusceptible, almost all putative atherogenic genes were overexpressed in CECs, whereas all atheroprotective genes were downregulated, relative to IECs. A subset of the identified genes was validated by quantitative polymerase chain reaction (PCR). PCR results suggest that the differences in expression levels between CECs and IECs for the HOXA10 and HOXA9 genes were >100-fold. Gene ontology (GO) and biological pathway analysis revealed a global expression difference between CECs and IECs. Genes in twelve GO categories, including complement immune activation, immunoglobulin-mediated response, and system development, were significantly upregulated in CECs. CECs also overexpressed genes involved in several inflammatory pathways, including the classical pathway of complement activation and the IGF-1-mediated pathway. The in vivo transcriptional differences between CECs and IECs found in this study may provide new insights into the factors responsible for coronary artery atherosusceptibility.
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Affiliation(s)
- Ji Zhang
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
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135
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Pantos I, Patatoukas G, Efstathopoulos EP, Katritsis D. In vivo wall shear stress measurements using phase-contrast MRI. Expert Rev Cardiovasc Ther 2008; 5:927-38. [PMID: 17867922 DOI: 10.1586/14779072.5.5.927] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
There is growing evidence to suggest that endothelial biology and atherosclerosis depend on arterial wall shear stress (WSS). We review the existing literature on in vivo measurements of WSS in healthy individuals using phase-contrast MRI, which is a promising, noninvasive technique for determining various blood flow characteristics. WSS data exist for the following arteries: carotid, brachial, aorta and femoral. Measured values indicate that WSS is site specific, a finding which opposes the notion that physiological WSS values are maintained at a constant magnitude in all parts of the arterial system. Among the WSS values obtained at the same site by different investigators there is qualitative agreement; however, differences exist in absolute values mainly due to the dependence on the method used to obtain WSS values from velocity data.
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Affiliation(s)
- Ioannis Pantos
- Athens Euroclinic, Department of Cardiology, 9 Athanassiadou St, Athens 11521, Greece.
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136
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Chang K, Weiss D, Suo J, Vega JD, Giddens D, Taylor WR, Jo H. Bone Morphogenic Protein Antagonists Are Coexpressed With Bone Morphogenic Protein 4 in Endothelial Cells Exposed to Unstable Flow In Vitro in Mouse Aortas and in Human Coronary Arteries. Circulation 2007; 116:1258-66. [PMID: 17785623 DOI: 10.1161/circulationaha.106.683227] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
Exposure to disturbed flow, including oscillatory shear stress, stimulates endothelial cells (ECs) to produce bone morphogenic protein (BMP) 4, which in turn activates inflammation, a critical atherogenic step. BMP activity is regulated by the level of BMP antagonists. Until now it was not known whether shear also regulates the expression of BMP antagonists and whether they play a role in EC pathophysiology.
Methods and Results—
BMP antagonists follistatin, noggin, and matrix Gla protein were expressed in cultured bovine and human arterial ECs. Surprisingly, oscillatory shear stress increased expression of the BMP antagonists in ECs, whereas unidirectional laminar shear decreased such expression. Immunohistochemical studies with mouse aortas showed data consistent with in vitro findings: Only ECs in the lesser curvature exposed to disturbed flow, but not those in the greater curvature and straight arterial regions exposed to undisturbed flow, showed coexpression of BMP4 and the BMP antagonists. Similarly, in human coronary arteries, expression of BMP4 and BMP antagonists in ECs positively correlated with the severity of atherosclerosis. Monocyte adhesion induced by oscillatory shear stress was inhibited by knockdown of BMP4 or treatment with recombinant follistatin or noggin, whereas it was increased by knockdown of follistatin and/or noggin.
Conclusions—
The present results suggest that ECs coexpress BMP antagonists along with BMP4 in an attempt to minimize the inflammatory response by oscillatory shear stress as part of a negative feedback mechanism. The balance between the agonist, BMP4, and its antagonists may play an important role in the overall control of inflammation and atherosclerosis.
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Affiliation(s)
- Kyunghwa Chang
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech and Emory University, Atlanta, GA 30322, USA
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137
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Liu AC, Joag VR, Gotlieb AI. The emerging role of valve interstitial cell phenotypes in regulating heart valve pathobiology. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:1407-18. [PMID: 17823281 PMCID: PMC2043503 DOI: 10.2353/ajpath.2007.070251] [Citation(s) in RCA: 435] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The study of the cellular and molecular pathogenesis of heart valve disease is an emerging area of research made possible by the availability of cultures of valve interstitial cells (VICs) and valve endothelial cells (VECs) and by the design and use of in vitro and in vivo experimental systems that model elements of valve biological and pathobiological activity. VICs are the most common cells in the valve and are distinct from other mesenchymal cell types in other organs. We present a conceptual approach to the investigation of VICs by focusing on VIC phenotype-function relationships. Our review suggests that there are five identifiable phenotypes of VICs that define the current understanding of their cellular and molecular functions. These include embryonic progenitor endothelial/mesenchymal cells, quiescent VICs (qVICs), activated VICs (aVICs), progenitor VICs (pVICs), and osteoblastic VICs (obVICs). Although these may exhibit plasticity and may convert from one form to another, compartmentalizing VIC function into distinct phenotypes is useful in bringing clarity to our understanding of VIC pathobiology. We present a conceptual model that is useful in the design and interpretation of studies on the function of an important phenotype in disease, the activated VIC. We hope this review will inspire members of the investigative pathology community to consider valve pathobiology as an exciting new frontier exploring pathogenesis and discovering new therapeutic targets in cardiovascular diseases.
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Affiliation(s)
- Amber C Liu
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, M5G 1L5, ON, Canada
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138
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Butcher JT, McQuinn TC, Sedmera D, Turner D, Markwald RR. Transitions in Early Embryonic Atrioventricular Valvular Function Correspond With Changes in Cushion Biomechanics That Are Predictable by Tissue Composition. Circ Res 2007; 100:1503-11. [PMID: 17478728 DOI: 10.1161/circresaha.107.148684] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endocardial cushions are critical to maintain unidirectional blood flow under constantly increasing hemodynamic forces, but the interrelationship between endocardial cushion structure and the mechanics of atrioventricular junction function is poorly understood. Atrioventricular (AV) canal motions and blood velocities of embryonic chicks at Hamburger and Hamilton (HH) stages 17, 21, and 25 were quantified using ultrasonography. Similar to the embryonic zebrafish heart, the HH17 AV segment functions like a suction pump, with the cushions expanding in a wave during peak myocardial contraction and becoming undetectable during the relaxation phase. By HH25, the AV canal contributes almost nothing to the piston-like propulsion of blood, but the cushions function as stoppers apposing blood flow with near constant thickness. Using a custom built mesomechanical testing system, we quantified the nonlinear pseudoelastic biomechanics of developing AV cushions, and found that both AV cushions increased in effective modulus between HH17 and HH25. Enzymatic digestion of major structural constituent collagens or glycosaminoglycans resulted in distinctly different stress-strain curves suggestive of their individual contributions. Mixture theory using histologically determined volume fractions of cells, collagen, and glycosaminoglycans showed good prediction of cushion material properties regardless of stage and cushion position. These results have important implications in valvular development, as biomechanics may play a larger role in stimulating valvulogenic events than previously thought.
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Affiliation(s)
- Jonathan T Butcher
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Children's Research Institute, Medical University of South Carolina, Charleston, SC, USA.
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Katritsis D, Kaiktsis L, Chaniotis A, Pantos J, Efstathopoulos EP, Marmarelis V. Wall shear stress: theoretical considerations and methods of measurement. Prog Cardiovasc Dis 2007; 49:307-29. [PMID: 17329179 DOI: 10.1016/j.pcad.2006.11.001] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In arterial blood flow, the wall shear stress expresses the force per unit area exerted by the wall on the fluid in a direction on the local tangent plane. There is substantial evidence that the wall shear stress induced by the pulsatile blood flow in the arterial system affects the atherogenic process. It is now widely accepted that the vessel segments that appear to be at the highest risk for development of atherosclerosis are those with low wall shear stress or oscillating wall shear stress. The purpose of this article is to define wall shear stress, to introduce relevant concepts of fluid mechanics to nonexperts, and to critically review the various methods that have been used for the assessment of wall shear stress in animal and human blood circulation, paying special attention to the case of coronary arteries.
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Abstract
Endothelial cells, which form the inner cellular lining of blood vessels and lymphatics, display remarkable heterogeneity in structure and function. This is the second of a 2-part review on the phenotypic heterogeneity of blood vessel endothelial cells. The first part discusses the scope, the underlying mechanisms, and the diagnostic and therapeutic implications of phenotypic heterogeneity. Here, these principles are applied to an understanding of organ-specific phenotypes in representative vascular beds including arteries and veins, heart, lung, liver, and kidney. The goal is to underscore the importance of site-specific properties of the endothelium in mediating homeostasis and focal vascular pathology, while at the same time emphasizing the value of approaching the endothelium as an integrated system.
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Affiliation(s)
- William C Aird
- Division of Molecular and Vascular Medicine, Department of Medicine, and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass 02215, USA.
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Csiszar A, Labinskyy N, Smith KE, Rivera A, Bakker ENTP, Jo H, Gardner J, Orosz Z, Ungvari Z. Downregulation of bone morphogenetic protein 4 expression in coronary arterial endothelial cells: role of shear stress and the cAMP/protein kinase A pathway. Arterioscler Thromb Vasc Biol 2007; 27:776-82. [PMID: 17272757 DOI: 10.1161/01.atv.0000259355.77388.13] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Bone morphogenetic protein 4 (BMP-4) is a transforming growth factor beta family member cytokine that exerts proinflammatory effects on the endothelium and is likely to play a role in atherogenesis. Recent studies suggested that atheroprotective levels of shear stress control endothelial BMP-4 expression; however, the underlying mechanisms remained unknown. METHODS AND RESULTS We found that shear stress downregulated BMP-4 expression in human and rat coronary arterial endothelial cells (CAECs) as well as in cultured mesenteric arterioles, although it had no effect on the expression of BMP-2, a related cytokine. In human coronary arterial endothelial cells, 8-bromo-cAMP, the adenylate cyclase activator forskolin, or a cAMP-dependent protein kinase (PKA) activator effectively decreased BMP-4 expression, mimicking the effects of shear stress. Indeed, shear stress induced the nuclear translocation of PKA-c, and inhibition of PKA attenuated the effects of shear stress and forskolin on BMP-4 expression. RNA decay assay and BMP-4 promoter-driven luciferase reporter gene assay showed that cAMP regulates BMP-4 expression at the transcriptional level. CONCLUSIONS Laminar shear stress and the cAMP/PKA pathway are important negative regulators of BMP-4 expression in the vascular endothelium. Because BMP-4 elicits endothelial activation and dysfunction, hypertension, and vascular calcification, inhibition of BMP-4 expression by shear stress and the cAMP/PKA pathway is likely to exert antiatherogenic and vasculoprotective effects.
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Affiliation(s)
- Anna Csiszar
- Department of Physiology, New York Medical College, Valhalla, New York 10595, USA
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Schoen FJ. New frontiers in the pathology and therapy of heart valve disease: 2006 Society for Cardiovascular Pathology, Distinguished Achievement Award Lecture, United States–Canadian Academy of Pathology, Atlanta, GA, February 12, 2006. Cardiovasc Pathol 2006; 15:271-279. [PMID: 16979034 DOI: 10.1016/j.carpath.2006.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Accepted: 05/01/2006] [Indexed: 11/28/2022] Open
Abstract
This review summarizes several areas relative to the pathology of heart valve disease in which there has been rapid and ongoing evolution, namely, our understanding of: (a) the dynamic functional biology of cardiac valves; and (b) the pathology/pathobiology of valvular heart diseases; (c) new developments in valve repair and substitution using percutaneous approaches; and (d) progress toward the exciting potential of therapeutic valvular tissue engineering and regeneration, including the challenges that will need to be overcome before such therapeutic advances can become clinically useful.
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Affiliation(s)
- Frederick J Schoen
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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