@article{huang_huang_2015, title={Biaxial stress relaxation of semilunar heart valve leaflets during simulated collagen catabolism: Effects of collagenase concentration and equibiaxial strain state}, volume={229}, ISSN={0954-4119 2041-3033}, url={http://dx.doi.org/10.1177/0954411915604336}, DOI={10.1177/0954411915604336}, abstractNote={ Heart valve leaflet collagen turnover and remodeling are innate to physiological homeostasis; valvular interstitial cells routinely catabolize damaged collagen and affect repair. Moreover, evidence indicates that leaflets can adapt to altered physiological (e.g. pregnancy) and pathological (e.g. hypertension) mechanical load states, tuning collagen structure and composition to changes in pressure and flow. However, while valvular interstitial cell-secreted matrix metalloproteinases are considered the primary effectors of collagen catabolism, the mechanisms by which damaged collagen fibers are selectively degraded remain unclear. Growing evidence suggests that the collagen fiber strain state plays a key role, with the strain-dependent configuration of the collagen molecules either masking or presenting proteolytic sites, thereby protecting or accelerating collagen proteolysis. In this study, the effects of equibiaxial strain state on collagen catabolism were investigated in porcine aortic valve and pulmonary valve tissues. Bacterial collagenase (0.2 and 0.5 mg/mL) was utilized to simulate endogenous matrix metalloproteinases, and biaxial stress relaxation and biochemical collagen concentration served as functional and compositional measures of collagen catabolism, respectively. At a collagenase concentration of 0.5 mg/mL, increasing the equibiaxial strain imposed during stress relaxation (0%, 37.5%, and 50%) yielded significantly lower median collagen concentrations in the aortic valve ( p = 0.0231) and pulmonary valve ( p = 0.0183), suggesting that relatively large strain magnitudes may enhance collagen catabolism. Collagen concentration decreases were paralleled by trends of accelerated normalized stress relaxation rate with equibiaxial strain in aortic valve tissues. Collectively, these in vitro results indicate that biaxial strain state is capable of affecting the susceptibility of valvular collagens to catabolism, providing a basis for further investigation of how such phenomena may manifest at different strain magnitudes or in vivo. }, number={10}, journal={Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine}, publisher={SAGE Publications}, author={Huang, Siyao and Huang, Hsiao-Ying Shadow}, year={2015}, month={Sep}, pages={721–731} }
 @inproceedings{huang_huang_gettys_prim_harrysson_2014, title={A biomechanical study of directional mechanical properties of porcine skin tissues}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2013, vol 9}, author={Huang, H. Y. S. and Huang, S. Y. and Gettys, T. and Prim, P. M. and Harrysson, O. L.}, year={2014} }
 @article{huang_huang_frazier_prim_harrysson_2014, title={Directional biomechanical properties of porcine skin tissue}, volume={14}, number={5}, journal={Journal of Mechanics in Medicine and Biology}, author={Huang, H. Y. S. and Huang, S. Y. and Frazier, C. P. and Prim, P. M. and Harrysson, O.}, year={2014} }
 @article{huang_huang_2014, title={Prediction of matrix-to-cell stress transfer in heart valve tissues}, volume={41}, ISSN={0092-0606 1573-0689}, url={http://dx.doi.org/10.1007/s10867-014-9362-z}, DOI={10.1007/s10867-014-9362-z}, abstractNote={Non-linear and anisotropic heart valve leaflet tissue mechanics manifest principally from the stratification, orientation, and inhomogeneity of their collagenous microstructures. Disturbance of the native collagen fiber network has clear consequences for valve and leaflet tissue mechanics and presumably, by virtue of their intimate embedment, on the valvular interstitial cell stress–strain state and concomitant phenotype. In the current study, a set of virtual biaxial stretch experiments were conducted on porcine pulmonary valve leaflet tissue photomicrographs via an image-based finite element approach. Stress distribution evolution during diastolic valve closure was predicted at both the tissue and cellular levels. Orthotropic material properties consistent with distinct stages of diastolic loading were applied. Virtual experiments predicted tissue- and cellular-level stress fields, providing insight into how matrix-to-cell stress transfer may be influenced by the inhomogeneous collagen fiber architecture, tissue anisotropic material properties, and the cellular distribution within the leaflet tissue. To the best of the authors’ knowledge, this is the first study reporting on the evolution of stress fields at both the tissue and cellular levels in valvular tissue and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling the further study of valvular cell–matrix interactions.}, number={1}, journal={Journal of Biological Physics}, publisher={Springer Science and Business Media LLC}, author={Huang, Siyao and Huang, Hsiao-Ying Shadow}, year={2014}, month={Oct}, pages={9–22} }
 @inproceedings{huang_huang_2014, title={Tissue- and cell-level stress distributions of the heart valve tissue during diastole}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2013, vol 9}, author={Huang, S. Y. and Huang, H. Y. S.}, year={2014} }
 @inproceedings{huang_huang_gettys_harrysson_2013, title={A biomechanical study of directional mechanical properties of porcine skin tissues}, booktitle={ASME 2013 International Mechanical Engineering Congress & Exposition}, author={Huang, H.-Y. S. and Huang, S. and Gettys, T. A. and Harrysson, O.}, year={2013} }
 @inproceedings{huang_huang_2013, place={San Diego, CA}, title={Tissue- and cell-levels stress distribution of heart valve tissue during diastole}, DOI={10.1115/imece2013-63229}, abstractNote={Heart valves are inhomogeneous microstructure with nonlinear anisotropic properties and constantly experience different stress states during cardiac cycles. However, how tissue-level mechanical forces can translate into altered cellular stress states remains unclear, and associated biomechanical regulation in the tissue has not been fully understood. In the current study, we use an image-based finite element method to investigate factors contributing the stress distributions at both tissue- and cell-levels inside the healthy heart valve tissues. Effects of tissue microstructure, inhomogeneity, and anisotropic material property at different diastole states are discussed to provide a better understanding of structure-mechanics-property interactions, which alters tissue-to-cell stress transfer mechanisms in heart valve tissue. To the best of the authors’ knowledge, this is the first study reporting on the evolution of stress fields at both the tissue- and cellular-levels in valvular tissue, and thus contributes toward refining our collective understanding of valvular tissue micromechanics while providing a computational tool enabling further study of valvular cell-tissue interactions.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition}, author={Huang, Siyao and Huang, Hsiao-Ying Shadow}, year={2013} }
 @article{huang_huang_2013, title={Virtualisation of stress distribution in heart valve tissue}, volume={17}, ISSN={1025-5842 1476-8259}, url={http://dx.doi.org/10.1080/10255842.2013.763937}, DOI={10.1080/10255842.2013.763937}, abstractNote={This study presents an image-based finite element analysis incorporating histological photomicrographs of heart valve tissues. We report stress fields inside heart valve tissues, where heterogeneously distributed collagen fibres are responsible for transmitting forces into cells. Linear isotropic and anisotropic tissue material property models are incorporated to quantify the overall stress distributions in heart valve tissues. By establishing an effective predictive method with new computational tools and by performing virtual experiments on the heart valve tissue photomicrographs, we clarify how stresses are transferred from matrix to cell. The results clearly reveal the roles of heterogeneously distributed collagen fibres in mitigating stress developments inside heart valve tissues. Moreover, most local peak stresses occur around cell nuclei, suggesting that higher stress may be mediated by cells for biomechanical regulations.}, number={15}, journal={Computer Methods in Biomechanics and Biomedical Engineering}, publisher={Informa UK Limited}, author={Huang, Siyao and Huang, Hsiao-Ying Shadow}, year={2013}, month={Mar}, pages={1696–1704} }
 @inproceedings{huang_balhouse_huang_2012, place={Houston TX}, title={A Biomechanical and Biochemical Synergy Study of Heart Valve Tissue}, DOI={10.1115/imece2012-87997}, abstractNote={The function of heart valves is to allow blood to flow through the heart smoothly and to prevent retrograde flow of blood. Previous studies have shown that the mechanical properties of heart valve tissues, microstructures of extracellular matrix, and collagen concentrations are the keys to the healthy heart valves and, therefore, are crucial to the development of viable tissue-engineered heart valve replacements. Therefore, this study investigates the relationship between these factors in native porcine aortic and pulmonary valves and provides insights to the healthy heart valves. Heart valve leaflets are prepared for biaxial stretching to obtain mechanical properties. The average collagen concentrations of heart valve leaflets are determined via an assay kit. The results indicate that aortic valves are stiffer than pulmonary valves macroscopically and stiffness varies more in the circumferential direction for the aortic valve than it does for the pulmonary valve. Microscopically, it is due to collagen fibers in aortic valves are more in alignment than ones in pulmonary valves, which are more randomly in direction. Collagen assay results show that collagen concentrations are higher in the edges of pulmonary valves than in aortic valves. The results also suggest the duration of extraction may have significant affects on the concentration results. This work provides quantified stress and strain environment within heart valve tissues to help further studies on how to treat heart valve disease and create more viable heart valve replacements.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition}, author={Huang, Hsiao-Ying Shadow and Balhouse, Brittany N. and Huang, Siyao}, year={2012}, pages={235–240} }
 @article{huang_balhouse_huang_2012, title={Application of simple biomechanical and biochemical tests to heart valve leaflets: Implications for heart valve characterization and tissue engineering}, volume={226}, ISSN={0954-4119 2041-3033}, url={http://dx.doi.org/10.1177/0954411912455004}, DOI={10.1177/0954411912455004}, abstractNote={ A simple biomechanical test with real-time displacement and strain mapping is reported, which provides displacement vectors and principal strain directions during the mechanical characterization of heart valve tissues. The maps reported in the current study allow us to quickly identify the approximate strain imposed on a location in the samples. The biomechanical results show that the aortic valves exhibit stronger anisotropic mechanical behavior than that of the pulmonary valves before 18% strain equibiaxial stretching. In contrast, the pulmonary valves exhibit stronger anisotropic mechanical behavior than aortic valves beyond 28% strain equibiaxial stretching. Simple biochemical tests are also conducted. Collagens are extracted at different time points (24, 48, 72, and 120 h) at different locations in the samples. The results show that extraction time plays an important role in determining collagen concentration, in which a minimum of 72 h of extraction is required to obtain saturated collagen concentration. This work provides an easy approach for quantifying biomechanical and biochemical properties of semilunar heart valve tissues, and potentially facilitates the development of tissue engineered heart valves. }, number={11}, journal={Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine}, publisher={SAGE Publications}, author={Huang, Hsiao-Ying S and Balhouse, Brittany N and Huang, Siyao}, year={2012}, month={Aug}, pages={868–876} }
 @inproceedings{huang_huang_2012, title={Real-time strain mapping via biaxial stretching in heart valve tissues}, booktitle={IEEE Engineering in Medicine and Biology Society Conference Proceedings}, author={Huang, H.-Y. S. and Huang, S.}, year={2012}, pages={324–349} }
 @inproceedings{huang_huang_2012, title={Virtual experiments of heart valve tissues}, booktitle={IEEE Engineering in Medicine and Biology Society Conference Proceedings}, author={Huang, S. and Huang, H.-Y. S.}, year={2012}, pages={324–349} }