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Roth K, Liu W, LeBar K, Ahern M, Wang Z. Establishment of a Biaxial Testing System for Characterization of Right Ventricle Viscoelasticity Under Physiological Loadings. Cardiovasc Eng Technol 2024:10.1007/s13239-024-00722-5. [PMID: 38468114 DOI: 10.1007/s13239-024-00722-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 02/19/2024] [Indexed: 03/13/2024]
Abstract
PURPOSE Prior studies have indicated an impact of cardiac muscle viscoelasticity on systolic and diastolic functions. However, the studies of ventricular free wall viscoelasticity, particularly for that of right ventricles (RV), are limited. Moreover, investigations on ventricular passive viscoelasticity have been restricted to large animals and there is a lack of data on rodent species. To fill this knowledge gap, this study aims to develop a biaxial tester that induces high-speed physiological deformations to characterize the passive viscoelasticity of rat RVs. METHODS The biaxial testing system was fabricated so that planar deformation of rat ventricle tissues at physiological strain rates was possible. The testing system was validated using isotropic polydimethylsiloxane (PDMS) sheets. Next, viscoelastic measurements were performed in healthy rat RV free walls by equibiaxial cyclic sinusoidal loadings and stress relaxation. RESULTS The biaxial tester's consistency, accuracy, and stability was confirmed from the PDMS samples measurements. Moreover, significant viscoelastic alterations of the RV were found between sub-physiological (0.1 Hz) and physiological frequencies (1-8 Hz). From hysteresis loop analysis, we found as the frequency increased, the elasticity and viscosity were increased in both directions. Interestingly, the ratio of storage energy to dissipated energy (Wd/Ws) remained constant at 0.1-5 Hz. We did not observe marked differences in healthy RV viscoelasticity between longitudinal and circumferential directions. CONCLUSION This work provides a new experimental tool to quantify the passive, biaxial viscoelasticity of ventricle free walls in both small and large animals. The dynamic mechanical tests showed frequency-dependent elastic and viscous behaviors of healthy rat RVs. But the ratio of dissipated energy to stored energy was maintained between frequencies. These findings offer novel baseline information on the passive viscoelasticity of healthy RVs in adult rats.
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Affiliation(s)
- Kellan Roth
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA
| | - Wenqiang Liu
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
| | - Kristen LeBar
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA
| | - Matt Ahern
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA
| | - Zhijie Wang
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, USA.
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA.
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Wang Q, Spurlock B, Liu J, Qian L. Fibroblast Reprogramming in Cardiac Repair. JACC Basic Transl Sci 2024; 9:145-160. [PMID: 38362341 PMCID: PMC10864899 DOI: 10.1016/j.jacbts.2023.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 06/22/2023] [Accepted: 06/27/2023] [Indexed: 02/17/2024]
Abstract
Cardiovascular disease is one of the major causes of death worldwide. Limited proliferative capacity of adult mammalian cardiomyocytes has prompted researchers to exploit regenerative therapy after myocardial injury, such as myocardial infarction, to attenuate heart dysfunction caused by such injury. Direct cardiac reprogramming is a recently emerged promising approach to repair damaged myocardium by directly converting resident cardiac fibroblasts into cardiomyocyte-like cells. The achievement of in vivo direct reprogramming of fibroblasts has been shown, by multiple laboratories independently, to improve cardiac function and mitigate fibrosis post-myocardial infarction, which holds great potential for clinical application. There have been numerous pieces of valuable work in both basic and translational research to enhance our understanding and continued refinement of direct cardiac reprogramming in recent years. However, there remain many challenges to overcome before we can truly take advantage of this technique to treat patients with ischemic cardiac diseases. Here, we review recent progress of fibroblast reprogramming in cardiac repair, including the optimization of several reprogramming strategies, mechanistic exploration, and translational efforts, and we make recommendations for future research to further understand and translate direct cardiac reprogramming from bench to bedside. Challenges relating to these efforts will also be discussed.
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Affiliation(s)
- Qiaozi Wang
- Department of Pathology and Laboratory Medicine, McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Brian Spurlock
- Department of Pathology and Laboratory Medicine, McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Jiandong Liu
- Department of Pathology and Laboratory Medicine, McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Li Qian
- Department of Pathology and Laboratory Medicine, McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA
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Telle Å, Bargellini C, Chahine Y, Del Álamo JC, Akoum N, Boyle PM. Personalized biomechanical insights in atrial fibrillation: opportunities & challenges. Expert Rev Cardiovasc Ther 2023; 21:817-837. [PMID: 37878350 PMCID: PMC10841537 DOI: 10.1080/14779072.2023.2273896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Accepted: 10/18/2023] [Indexed: 10/26/2023]
Abstract
INTRODUCTION Atrial fibrillation (AF) is an increasingly prevalent and significant worldwide health problem. Manifested as an irregular atrial electrophysiological activation, it is associated with many serious health complications. AF affects the biomechanical function of the heart as contraction follows the electrical activation, subsequently leading to reduced blood flow. The underlying mechanisms behind AF are not fully understood, but it is known that AF is highly correlated with the presence of atrial fibrosis, and with a manifold increase in risk of stroke. AREAS COVERED In this review, we focus on biomechanical aspects in atrial fibrillation, current and emerging use of clinical images, and personalized computational models. We also discuss how these can be used to provide patient-specific care. EXPERT OPINION Understanding the connection betweenatrial fibrillation and atrial remodeling might lead to valuable understanding of stroke and heart failure pathophysiology. Established and emerging imaging modalities can bring us closer to this understanding, especially with continued advancements in processing accuracy, reproducibility, and clinical relevance of the associated technologies. Computational models of cardiac electromechanics can be used to glean additional insights on the roles of AF and remodeling in heart function.
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Affiliation(s)
- Åshild Telle
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Clarissa Bargellini
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Yaacoub Chahine
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | - Juan C Del Álamo
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA, USA
| | - Nazem Akoum
- Department of Bioengineering, University of Washington, Seattle, WA, USA
- Division of Cardiology, University of Washington, Seattle, WA, USA
| | - Patrick M Boyle
- Department of Bioengineering, University of Washington, Seattle, WA, USA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA, USA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, USA
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Pearce DP, Nemcek MT, Witzenburg CM. Don't go breakin' my heart: cardioprotective alterations to the mechanical and structural properties of reperfused myocardium during post-infarction inflammation. Biophys Rev 2023; 15:329-353. [PMID: 37396449 PMCID: PMC10310682 DOI: 10.1007/s12551-023-01068-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 05/21/2023] [Indexed: 07/04/2023] Open
Abstract
Myocardial infarctions (MIs) kickstart an intense inflammatory response resulting in extracellular matrix (ECM) degradation, wall thinning, and chamber dilation that leaves the heart susceptible to rupture. Reperfusion therapy is one of the most effective strategies for limiting adverse effects of MIs, but is a challenge to administer in a timely manner. Late reperfusion therapy (LRT; 3 + hours post-MI) does not limit infarct size, but does reduce incidences of post-MI rupture and improves long-term patient outcomes. Foundational studies employing LRT in the mid-twentieth century revealed beneficial reductions in infarct expansion, aneurysm formation, and left ventricle dysfunction. The mechanism by which LRT acts, however, is undefined. Structural analyses, relying largely on one-dimensional estimates of ECM composition, have found few differences in collagen content between LRT and permanently occluded animal models when using homogeneous samples from infarct cores. Uniaxial testing, on the other hand, revealed slight reductions in stiffness early in inflammation, followed soon after by an enhanced resistance to failure for cases of LRT. The use of one-dimensional estimates of ECM organization and gross mechanical function have resulted in a poor understanding of the infarct's spatially variable mechanical and structural anisotropy. To resolve these gaps in literature, future work employing full-field mechanical, structural, and cellular analyses is needed to better define the spatiotemporal post-MI alterations occurring during the inflammatory phase of healing and how they are impacted following reperfusion therapy. In turn, these studies may reveal how LRT affects the likelihood of rupture and inspire novel approaches to guide scar formation.
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Affiliation(s)
- Daniel P. Pearce
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Mark T. Nemcek
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Colleen M. Witzenburg
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
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Liu W, LeBar K, Roth K, Pang J, Ayers J, Chicco AJ, Puttlitz CM, Wang Z. Alterations of biaxial viscoelastic properties of the right ventricle in pulmonary hypertension development in rest and acute stress conditions. Front Bioeng Biotechnol 2023; 11:1182703. [PMID: 37324443 PMCID: PMC10266205 DOI: 10.3389/fbioe.2023.1182703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 05/17/2023] [Indexed: 06/17/2023] Open
Abstract
Introduction: The right ventricle (RV) mechanical property is an important determinant of its function. However, compared to its elasticity, RV viscoelasticity is much less studied, and it remains unclear how pulmonary hypertension (PH) alters RV viscoelasticity. Our goal was to characterize the changes in RV free wall (RVFW) anisotropic viscoelastic properties with PH development and at varied heart rates. Methods: PH was induced in rats by monocrotaline treatment, and the RV function was quantified by echocardiography. After euthanasia, equibiaxial stress relaxation tests were performed on RVFWs from healthy and PH rats at various strain-rates and strain levels, which recapitulate physiological deformations at varied heart rates (at rest and under acute stress) and diastole phases (at early and late filling), respectively. Results and Discussion: We observed that PH increased RVFW viscoelasticity in both longitudinal (outflow tract) and circumferential directions. The tissue anisotropy was pronounced for the diseased RVs, not healthy RVs. We also examined the relative change of viscosity to elasticity by the damping capacity (ratio of dissipated energy to total energy), and we found that PH decreased RVFW damping capacity in both directions. The RV viscoelasticity was also differently altered from resting to acute stress conditions between the groups-the damping capacity was decreased only in the circumferential direction for healthy RVs, but it was reduced in both directions for diseased RVs. Lastly, we found some correlations between the damping capacity and RV function indices and there was no correlation between elasticity or viscosity and RV function. Thus, the RV damping capacity may be a better indicator of RV function than elasticity or viscosity alone. These novel findings on RV dynamic mechanical properties offer deeper insights into the role of RV biomechanics in the adaptation of RV to chronic pressure overload and acute stress.
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Affiliation(s)
- Wenqiang Liu
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, United States
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, United States
| | - Kristen LeBar
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, United States
| | - Kellan Roth
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, United States
| | - Jassia Pang
- Laboratory Animal Resources, Colorado State University, Fort Collins, CO, United States
| | - Jessica Ayers
- Laboratory Animal Resources, Colorado State University, Fort Collins, CO, United States
| | - Adam J. Chicco
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Christian M. Puttlitz
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, United States
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, United States
| | - Zhijie Wang
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, United States
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, United States
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Motchon YD, Sack KL, Sirry MS, Kruger M, Pauwels E, Van Loo D, De Muynck A, Van Hoorebeke L, Davies NH, Franz T. Effect of biomaterial stiffness on cardiac mechanics in a biventricular infarcted rat heart model with microstructural representation of in situ intramyocardial injectate. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2023; 39:e3693. [PMID: 36864599 PMCID: PMC10909490 DOI: 10.1002/cnm.3693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 11/19/2022] [Accepted: 01/29/2023] [Indexed: 05/13/2023]
Abstract
Intramyocardial delivery of biomaterials is a promising concept for treating myocardial infarction. The delivered biomaterial provides mechanical support and attenuates wall thinning and elevated wall stress in the infarct region. This study aimed at developing a biventricular finite element model of an infarcted rat heart with a microstructural representation of an in situ biomaterial injectate, and a parametric investigation of the effect of the injectate stiffness on the cardiac mechanics. A three-dimensional subject-specific biventricular finite element model of a rat heart with left ventricular infarct and microstructurally dispersed biomaterial delivered 1 week after infarct induction was developed from ex vivo microcomputed tomography data. The volumetric mesh density varied between 303 mm-3 in the myocardium and 3852 mm-3 in the injectate region due to the microstructural intramyocardial dispersion. Parametric simulations were conducted with the injectate's elastic modulus varying from 4.1 to 405,900 kPa, and myocardial and injectate strains were recorded. With increasing injectate stiffness, the end-diastolic median myocardial fibre and cross-fibre strain decreased in magnitude from 3.6% to 1.1% and from -6.0% to -2.9%, respectively. At end-systole, the myocardial fibre and cross-fibre strain decreased in magnitude from -20.4% to -11.8% and from 6.5% to 4.6%, respectively. In the injectate, the maximum and minimum principal strains decreased in magnitude from 5.4% to 0.001% and from -5.4% to -0.001%, respectively, at end-diastole and from 38.5% to 0.06% and from -39.0% to -0.06%, respectively, at end-systole. With the microstructural injectate geometry, the developed subject-specific cardiac finite element model offers potential for extension to cellular injectates and in silico studies of mechanotransduction and therapeutic signalling in the infarcted heart with an infarct animal model extensively used in preclinical research.
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Affiliation(s)
- Y. D. Motchon
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human BiologyUniversity of Cape TownCape TownSouth Africa
| | - Kevin L. Sack
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human BiologyUniversity of Cape TownCape TownSouth Africa
- Department of SurgeryUniversity of California at San FranciscoSan FranciscoCaliforniaUSA
| | - M. S. Sirry
- Department of Biomedical Engineering, School of Engineering and ComputingAmerican International UniversityAl JahraKuwait
| | - M. Kruger
- Cardiovascular Research Unit, MRC IUCHRUUniversity of Cape TownCape TownSouth Africa
| | - E. Pauwels
- Centre for X‐ray Tomography, Department of Physics and AstronomyGhent UniversityGhentBelgium
- Nuclear MedicineUniversity Hospitals LeuvenLeuvenBelgium
| | - D. Van Loo
- Centre for X‐ray Tomography, Department of Physics and AstronomyGhent UniversityGhentBelgium
- XRE nv, Bollebergen 2B box 1, 9052GhentBelgium
| | - A. De Muynck
- Centre for X‐ray Tomography, Department of Physics and AstronomyGhent UniversityGhentBelgium
| | - L. Van Hoorebeke
- Centre for X‐ray Tomography, Department of Physics and AstronomyGhent UniversityGhentBelgium
| | - Neil H. Davies
- Cardiovascular Research Unit, MRC IUCHRUUniversity of Cape TownCape TownSouth Africa
| | - Thomas Franz
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human BiologyUniversity of Cape TownCape TownSouth Africa
- Bioengineering Science Research Group, Faculty of Engineering and Physical SciencesUniversity of SouthamptonSouthamptonUK
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Ren M, Ong C, Buist ML, Yap CH. Biventricular biaxial mechanical testing and constitutive modelling of fetal porcine myocardium passive stiffness. J Mech Behav Biomed Mater 2022; 134:105383. [DOI: 10.1016/j.jmbbm.2022.105383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 07/02/2022] [Accepted: 07/15/2022] [Indexed: 11/15/2022]
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Biomechanical analysis of sheep oesophagus subjected to biaxial testing including hyperelastic constitutive model fitting. Heliyon 2022; 8:e09312. [PMID: 35615432 PMCID: PMC9124710 DOI: 10.1016/j.heliyon.2022.e09312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 01/11/2022] [Accepted: 04/19/2022] [Indexed: 11/23/2022] Open
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9
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Determination of Cross-Directional and Cross-Wall Variations of Passive Biaxial Mechanical Properties of Rat Myocardia. Processes (Basel) 2022. [DOI: 10.3390/pr10040629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Heart myocardia are critical to the facilitation of heart pumping and blood circulating around the body. The biaxial mechanical testing of the left ventricle (LV) has been extensively utilised to build the computational model of the whole heart with little importance given to the unique mechanical properties of the right ventricle (RV) and cardiac septum (SPW). Most of those studies focussed on the LV of the heart and then applied the obtained characteristics with a few modifications to the right side of the heart. However, the assumption that the LV characteristics applies to the RV has been contested over time with the realisation that the right side of the heart possesses its own unique mechanical properties that are widely distinct from that of the left side of the heart. This paper evaluates the passive mechanical property differences in the three main walls of the rat heart based on biaxial tensile test data. Fifteen mature Wistar rats weighing 225 ± 25 g were euthanised by inhalation of 5% halothane. The hearts were excised after which all the top chambers comprising the two atria, pulmonary and vena cava trunks, aorta, and valves were all dissected out. Then, 5 × 5 mm sections from the middle of each wall were carefully dissected with a surgical knife to avoid overly pre-straining the specimens. The specimens were subjected to tensile testing. The elastic moduli, peak stresses in the toe region and stresses at 40% strain, anisotropy indices, as well as the stored strain energy in the toe and linear region of up to 40% strain were used for statistical significance tests. The main findings of this study are: (1) LV and SPW tissues have relatively shorter toe regions of 10–15% strain as compared to RV tissue, whose toe region extends up to twice as much as that; (2) LV tissues have a higher strain energy storage in the linear region despite being lower in stiffness than the RV; and (3) the SPW has the highest strain energy storage along both directions, which might be directly related to its high level of anisotropy. These findings, though for a specific animal species at similar age and around the same body mass, emphasise the importance of the application of wall-specific material parameters to obtain accurate ventricular hyperelastic models. The findings further enhance our understanding of the desired mechanical behaviour of the different ventricle walls.
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Wang H, Wisneski A, Imbrie-Moore AM, Paulsen MJ, Wang Z, Xuan Y, Lopez Hernandez H, Hironaka CE, Lucian HJ, Shin HS, Anilkumar S, Thakore AD, Farry JM, Eskandari A, Williams KM, Grady F, Wu MA, Jung J, Stapleton LM, Steele AN, Zhu Y, Woo YJ. Natural cardiac regeneration conserves native biaxial left ventricular biomechanics after myocardial infarction in neonatal rats. J Mech Behav Biomed Mater 2022; 126:105074. [PMID: 35030471 PMCID: PMC8899021 DOI: 10.1016/j.jmbbm.2022.105074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 12/23/2021] [Accepted: 01/02/2022] [Indexed: 02/03/2023]
Abstract
After myocardial infarction (MI), adult mammals exhibit scar formation, adverse left ventricular (LV) remodeling, LV stiffening, and impaired contractility, ultimately resulting in heart failure. Neonatal mammals, however, are capable of natural heart regeneration after MI. We hypothesized that neonatal cardiac regeneration conserves native biaxial LV mechanics after MI. Wistar rat neonates (1 day old, n = 46) and adults (8-10 weeks old, n = 20) underwent sham surgery or permanent left anterior descending coronary artery ligation. At 6 weeks after neonatal MI, Masson's trichrome staining revealed negligible fibrosis. Echocardiography for the neonatal MI (n = 15) and sham rats (n = 14) revealed no differences in LV wall thickness or chamber diameter, and both groups had normal ejection fraction (72.7% vs 77.5%, respectively, p = 0.1946). Biaxial tensile testing revealed similar stress-strain curves along both the circumferential and longitudinal axes across a full range of physiologic stresses and strains. The circumferential modulus (267.9 kPa vs 274.2 kPa, p = 0.7847), longitudinal modulus (269.3 kPa vs 277.1 kPa, p = 0.7435), and maximum shear stress (3.30 kPa vs 3.95 kPa, p = 0.5418) did not differ significantly between the neonatal MI and sham groups, respectively. In contrast, transmural scars were observed at 4 weeks after adult MI. Adult MI hearts (n = 7) exhibited profound LV wall thinning (p < 0.0001), chamber dilation (p = 0.0246), and LV dysfunction (ejection fraction 45.4% vs 79.7%, p < 0.0001) compared to adult sham hearts (n = 7). Adult MI hearts were significantly stiffer than adult sham hearts in both the circumferential (321.5 kPa vs 180.0 kPa, p = 0.0111) and longitudinal axes (315.4 kPa vs 172.3 kPa, p = 0.0173), and also exhibited greater maximum shear stress (14.87 kPa vs 3.23 kPa, p = 0.0162). Our study is the first to show that native biaxial LV mechanics are conserved after neonatal heart regeneration following MI, thus adding biomechanical support for the therapeutic potential of cardiac regeneration in the treatment of ischemic heart disease.
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Affiliation(s)
- Hanjay Wang
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
| | - Andrew Wisneski
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Annabel M Imbrie-Moore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Michael J Paulsen
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Zhongjie Wang
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Yue Xuan
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | | | - Camille E Hironaka
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Haley J Lucian
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Hye Sook Shin
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Shreya Anilkumar
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Akshara D Thakore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Justin M Farry
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Anahita Eskandari
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Kiah M Williams
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Frederick Grady
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Matthew A Wu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Jinsuh Jung
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Lyndsay M Stapleton
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Amanda N Steele
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Yuanjia Zhu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Y Joseph Woo
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA.
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Perveen S, Rossin D, Vitale E, Rosso R, Vanni R, Cristallini C, Rastaldo R, Giachino C. Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions. Int J Mol Sci 2021; 22:ijms222313054. [PMID: 34884856 PMCID: PMC8658014 DOI: 10.3390/ijms222313054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 12/14/2022] Open
Abstract
Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.
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Affiliation(s)
- Sadia Perveen
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
| | - Daniela Rossin
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
| | - Emanuela Vitale
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
| | - Rachele Rosso
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
| | - Roberto Vanni
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
| | | | - Raffaella Rastaldo
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
- Correspondence:
| | - Claudia Giachino
- Department of Clinical and Biological Sciences, University of Turin, 10043 Orbassano, Italy; (S.P.); (D.R.); (E.V.); (R.R.); (R.V.); (C.G.)
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Emig R, Zgierski-Johnston CM, Timmermann V, Taberner AJ, Nash MP, Kohl P, Peyronnet R. Passive myocardial mechanical properties: meaning, measurement, models. Biophys Rev 2021; 13:587-610. [PMID: 34765043 PMCID: PMC8555034 DOI: 10.1007/s12551-021-00838-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/26/2021] [Indexed: 02/06/2023] Open
Abstract
Passive mechanical tissue properties are major determinants of myocardial contraction and relaxation and, thus, shape cardiac function. Tightly regulated, dynamically adapting throughout life, and affecting a host of cellular functions, passive tissue mechanics also contribute to cardiac dysfunction. Development of treatments and early identification of diseases requires better spatio-temporal characterisation of tissue mechanical properties and their underlying mechanisms. With this understanding, key regulators may be identified, providing pathways with potential to control and limit pathological development. Methodologies and models used to assess and mimic tissue mechanical properties are diverse, and available data are in part mutually contradictory. In this review, we define important concepts useful for characterising passive mechanical tissue properties, and compare a variety of in vitro and in vivo techniques that allow one to assess tissue mechanics. We give definitions of key terms, and summarise insight into determinants of myocardial stiffness in situ. We then provide an overview of common experimental models utilised to assess the role of environmental stiffness and composition, and its effects on cardiac cell and tissue function. Finally, promising future directions are outlined.
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Affiliation(s)
- Ramona Emig
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Callum M. Zgierski-Johnston
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Viviane Timmermann
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew J. Taberner
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
- Department of Engineering Science, The University of Auckland, Auckland, New Zealand
| | - Martyn P. Nash
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
- Department of Engineering Science, The University of Auckland, Auckland, New Zealand
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Faculty of Engineering, University of Freiburg, Freiburg, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg, Bad Krozingen, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
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13
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Liu W, Nguyen-Truong M, Ahern M, Labus KM, Puttlitz CM, Wang Z. Different Passive Viscoelastic Properties Between the Left and Right Ventricles in Healthy Adult Ovine. J Biomech Eng 2021; 143:1115540. [PMID: 34350934 DOI: 10.1115/1.4052004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Indexed: 01/03/2023]
Abstract
Ventricle dysfunction is the most common cause of heart failure, which leads to high mortality and morbidity. The mechanical behavior of the ventricle is critical to its physiological function. It is known that the ventricle is anisotropic and viscoelastic. However, the understanding of ventricular viscoelasticity is much less than that of its elasticity. Moreover, the left and right ventricles (LV&RV) are different in embryologic origin, anatomy, and function, but whether they distinguish in viscoelastic properties is unclear. We hypothesized that passive viscoelasticity is different between healthy LVs and RVs. Ex vivo cyclic biaxial tensile mechanical tests (1, 0.1, 0.01 Hz) and stress relaxation (strain of 3, 6, 9, 12, 15%) were performed for ventricles from healthy adult sheep. Outflow track direction was defined as the longitudinal direction. Hysteresis stress-strain loops and stress relaxation curves were obtained to quantify the viscoelastic properties. We found that the RV had more pronounced frequency-dependent viscoelastic changes than the LV. Under the physiological frequency (1 Hz), the LV was more anisotropic in the elasticity and stiffer than the RV in both directions, whereas the RV was more anisotropic in the viscosity and more viscous than the LV in the longitudinal direction. The LV was quasi-linear viscoelastic in the longitudinal but not circumferential direction, and the RV was nonlinear viscoelastic in both directions. This study is the first to investigate passive viscoelastic differences in healthy LVs and RVs, and the findings will deepen the understanding of biomechanical mechanisms of ventricular function.
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Affiliation(s)
- Wenqiang Liu
- School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523
| | - Michael Nguyen-Truong
- School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523
| | - Matt Ahern
- School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523
| | - Kevin M Labus
- Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery,Fort Collins, CO 80523
| | - Christian M Puttlitz
- School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523; Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523; Department of Clinical Sciences, Colorado State University, 1678 Campus Delivery, Fort Collins, CO 80523
| | - Zhijie Wang
- Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523; School of Biomedical Engineering, Colorado State University, 1376 Campus Delivery, Fort Collins, CO 80523; 1301 Campus Delivery, Fort Collins, CO 80523
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14
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Martonová D, Alkassar M, Seufert J, Holz D, Dương MT, Reischl B, Friedrich O, Leyendecker S. Passive mechanical properties in healthy and infarcted rat left ventricle characterised via a mixture model. J Mech Behav Biomed Mater 2021; 119:104430. [PMID: 33780851 DOI: 10.1016/j.jmbbm.2021.104430] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 02/21/2021] [Accepted: 02/22/2021] [Indexed: 11/29/2022]
Abstract
During the cardiac cycle, electrical excitation is coupled with mechanical response of the myocardium. Besides the active contraction, passive mechanics plays an important role, and its behaviour differs in healthy and diseased hearts as well as among different animal species. The aim of this study is the characterisation of passive mechanical properties in healthy and infarcted rat myocardium by means of mechanical testing and subsequent parameter fitting. Elasticity assessments via uniaxial extension tests are performed on healthy and infarcted tissue samples from left ventricular rat myocardium. In order to fully characterise the orthotropic cardiac tissue, our experimental data are combined with other previously published tests in rats - shear tests on healthy myocardium and equibiaxial tests on infarcted tissue. In a first step, we calibrate the Holzapfel-Ogden strain energy function in the healthy case. Sa far, this orthotropic constitutive law for the passive myocardium has been fitted to experimental data in several species, however there is a lack of an appropriate parameter set for the rat. With our determined parameters, a finite element simulation of the end-diastolic filling is performed. In a second step, we propose a model for the infarcted tissue. It is represented as a mixture of intact myocardium and a transversely isotropic scar structure. In our mechanical experiments, the tissue after myocardial infarction shows significantly stiffer behaviour than in the healthy case, and the stiffness correlates with the amount of fibrosis. A similar relationship is observed in the computational simulation of the end-diastolic filling. We conclude that our new proposed material model can capture the behaviour of two kinds of tissues - healthy and infarcted rat myocardium, and its calibration with the fitted parameters represents the experimental data well.
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Affiliation(s)
- Denisa Martonová
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Dynamics, Immerwahrstraße 1, 91058 Erlangen, Germany.
| | - Muhannad Alkassar
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Pediatric Cardiology, Loschgestraße 15, 91054 Erlangen, Germany
| | - Julia Seufert
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Pediatric Cardiology, Loschgestraße 15, 91054 Erlangen, Germany
| | - David Holz
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Dynamics, Immerwahrstraße 1, 91058 Erlangen, Germany
| | - Minh Tuấn Dương
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Dynamics, Immerwahrstraße 1, 91058 Erlangen, Germany; School of Mechanical Engineering, Hanoi University of Science and Technology, 1 DaiCoViet Road, Hanoi, Vietnam
| | - Barbara Reischl
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Medical Biotechnology, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
| | - Oliver Friedrich
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Medical Biotechnology, Paul-Gordan-Str. 3, 91052 Erlangen, Germany
| | - Sigrid Leyendecker
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Applied Dynamics, Immerwahrstraße 1, 91058 Erlangen, Germany
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Jorba I, Mostert D, Hermans LH, van der Pol A, Kurniawan NA, Bouten CV. In Vitro Methods to Model Cardiac Mechanobiology in Health and Disease. Tissue Eng Part C Methods 2021; 27:139-151. [PMID: 33514281 PMCID: PMC7984657 DOI: 10.1089/ten.tec.2020.0342] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/26/2021] [Indexed: 12/17/2022] Open
Abstract
In vitro cardiac modeling has taken great strides in the past decade. While most cell and engineered tissue models have focused on cell and tissue contractile function as readouts, mechanobiological cues from the cell environment that affect this function, such as matrix stiffness or organization, are less well explored. In this study, we review two-dimensional (2D) and three-dimensional (3D) models of cardiac function that allow for systematic manipulation or precise control of mechanobiological cues under simulated (patho)physiological conditions while acquiring multiple readouts of cell and tissue function. We summarize the cell types used in these models and highlight the importance of linking 2D and 3D models to address the multiscale organization and mechanical behavior. Finally, we provide directions on how to advance in vitro modeling for cardiac mechanobiology using next generation hydrogels that mimic mechanical and structural environmental features at different length scales and diseased cell types, along with the development of new tissue fabrication and readout techniques. Impact statement Understanding the impact of mechanobiology in cardiac (patho)physiology is essential for developing effective tissue regeneration and drug discovery strategies and requires detailed cause-effect studies. The development of three-dimensional in vitro models allows for such studies with high experimental control, while integrating knowledge from complementary cell culture models and in vivo studies for this purpose. Complemented by the use of human-induced pluripotent stem cells, with or without predisposed genetic diseases, these in vitro models will offer promising outlooks to delineate the impact of mechanobiological cues on human cardiac (patho)physiology in a dish.
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Affiliation(s)
- Ignasi Jorba
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
| | - Dylan Mostert
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
| | - Leon H.L. Hermans
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
| | - Atze van der Pol
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
| | - Nicholas A. Kurniawan
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
| | - Carlijn V.C. Bouten
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems (ICMS), Eindhoven, The Netherlands
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16
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Biomechanical properties of acellular scar ECM during the acute to chronic stages of myocardial infarction. J Mech Behav Biomed Mater 2021; 116:104342. [PMID: 33516128 DOI: 10.1016/j.jmbbm.2021.104342] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 01/14/2021] [Accepted: 01/17/2021] [Indexed: 02/08/2023]
Abstract
After myocardial infarction (MI), the infarcted tissue undergoes dynamic and time-dependent changes. Previous knowledge on MI biomechanical alterations has been obtained by studying the explanted scar tissues. In this study, we decellularized MI scar tissue and characterized the biomechanics of the obtained pure scar ECM. By thoroughly removing the cellular content in the MI scar tissue, we were able to avoid its confounding effects. Rat MI hearts were obtained from a reliable and reproducible model based on permanent left coronary artery ligation (PLCAL). MI heart explants at various time points (15 min, 1 week, 2 weeks, 4 weeks, and 12 weeks) were subjected to decellularization with 0.1% sodium dodecyl sulfate solution for ~1-2 weeks to obtain acellular scar ECM. A biaxial mechanical testing system was used to characterize the acellular scar ECM under physiologically relevant loading conditions. After decellularization, large decrease in wall thickness was observed in the native heart ECM and 15 min scar ECM, implying the collapse of cardiomyocyte lacunae after removal of heart muscle fibers. For scar ECM 1 week, 2 weeks, and 4 weeks post infarction, the decrease in wall thickness after decellularization was small. For scar ECM 12 weeks post infarction, the reduction amount of wall thickness due to decellularization was minimal. We found that the scar ECM preserved the overall mechanical anisotropy of the native ventricle wall and MI scar tissue, in which the longitudinal direction is more extensible. Acellular scar ECM from 15 min to 12 weeks post infarction showed an overall stiffening trend in biaxial behavior, in which longitudinal direction was mostly affected and manifested with a decreased extensibility and increased modulus. This reduction trend of longitudinal extensibility also led to a decreased anisotropy index in the scar ECM from the acute to chronic stages of MI. The post-MI change in biomechanical properties of the scar ECM reflected the alterations of collagen fiber network, confirmed by the histology of scar ECM. In short, the reported structure-property relationship reveals how scar ECM biophysical properties evolve from the acute to chronic stages of MI. The obtained information will help establish a knowledge basis about the dynamics of scar ECM to better understand post-MI cardiac remodeling.
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17
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Dempsey S, Jafari P, So A, Samani A. A Composite Material Based Neural Network for Tissue Mechanical Properties Estimation Toward Stage Assessment of Infarction. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:2800-2803. [PMID: 33018588 DOI: 10.1109/embc44109.2020.9176151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cardiac biomechanical modelling is a promising new tool to be used in prognostic medicine and therapy planning for patients suffering from a variety of cardiovascular diseases and injuries. In order to have an accurate biomechanical model, personalized parameters to define loading, boundary conditions and mechanical properties are required. Achieving personalized modelling parameters often requires inverse optimization which is computationally expensive; hence techniques to reduce the multivariable complexity are in need. Presented in this paper is the fundamental blueprint to create a library of scar tissue mechanical properties to be used in modelling the healing mechanics of hearts that have suffered acute myocardial infarction. This library can be used to reduce the number of variables necessary to capture the scar tissue mechanical properties down to 1. This single parameter also carries information pertaining to staging of the scar tissue healing, predict its rate, and predict its collagen density. This information can be potentially used as valuable biomarkers to adjust existing or develop new treatment plans for patients.
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18
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Wang H, Bennett-Kennett R, Paulsen MJ, Hironaka CE, Thakore AD, Farry JM, Eskandari A, Lucian HJ, Shin HS, Wu MA, Imbrie-Moore AM, Steele AN, Stapleton LM, Zhu Y, Dauskardt RH, Woo YJ. Multiaxial Lenticular Stress-Strain Relationship of Native Myocardium is Preserved by Infarct-Induced Natural Heart Regeneration in Neonatal Mice. Sci Rep 2020; 10:7319. [PMID: 32355240 PMCID: PMC7193551 DOI: 10.1038/s41598-020-63324-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/13/2020] [Indexed: 12/16/2022] Open
Abstract
Neonatal mice exhibit natural heart regeneration after myocardial infarction (MI) on postnatal day 1 (P1), but this ability is lost by postnatal day 7 (P7). Cardiac biomechanics intricately affect long-term heart function, but whether regenerated cardiac muscle is biomechanically similar to native myocardium remains unknown. We hypothesized that neonatal heart regeneration preserves native left ventricular (LV) biomechanical properties after MI. C57BL/6J mice underwent sham surgery or left anterior descending coronary artery ligation at age P1 or P7. Echocardiography performed 4 weeks post-MI showed that P1 MI and sham mice (n = 22, each) had similar LV wall thickness, diameter, and ejection fraction (59.6% vs 60.7%, p = 0.6514). Compared to P7 shams (n = 20), P7 MI mice (n = 20) had significant LV wall thinning, chamber enlargement, and depressed ejection fraction (32.6% vs 61.8%, p < 0.0001). Afterward, the LV was explanted and pressurized ex vivo, and the multiaxial lenticular stress-strain relationship was tracked. While LV tissue modulus for P1 MI and sham mice were similar (341.9 kPa vs 363.4 kPa, p = 0.6140), the modulus for P7 MI mice was significantly greater than that for P7 shams (691.6 kPa vs 429.2 kPa, p = 0.0194). We conclude that, in neonatal mice, regenerated LV muscle has similar biomechanical properties as native LV myocardium.
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Affiliation(s)
- Hanjay Wang
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA
| | - Ross Bennett-Kennett
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Michael J Paulsen
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Camille E Hironaka
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Akshara D Thakore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Justin M Farry
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Anahita Eskandari
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Haley J Lucian
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Hye Sook Shin
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Matthew A Wu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Annabel M Imbrie-Moore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Amanda N Steele
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Lyndsay M Stapleton
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Yuanjia Zhu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Reinhold H Dauskardt
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Y Joseph Woo
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA.
- Stanford Cardiovascular Institute, Stanford University, Stanford, CA, USA.
- Department of Bioengineering, Stanford University, Stanford, CA, USA.
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19
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Liu W, Wang Z. Current Understanding of the Biomechanics of Ventricular Tissues in Heart Failure. Bioengineering (Basel) 2019; 7:bioengineering7010002. [PMID: 31861916 PMCID: PMC7175293 DOI: 10.3390/bioengineering7010002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/17/2019] [Accepted: 12/18/2019] [Indexed: 12/17/2022] Open
Abstract
Heart failure is the leading cause of death worldwide, and the most common cause of heart failure is ventricular dysfunction. It is well known that the ventricles are anisotropic and viscoelastic tissues and their mechanical properties change in diseased states. The tissue mechanical behavior is an important determinant of the function of ventricles. The aim of this paper is to review the current understanding of the biomechanics of ventricular tissues as well as the clinical significance. We present the common methods of the mechanical measurement of ventricles, the known ventricular mechanical properties including the viscoelasticity of the tissue, the existing computational models, and the clinical relevance of the ventricular mechanical properties. Lastly, we suggest some future research directions to elucidate the roles of the ventricular biomechanics in the ventricular dysfunction to inspire new therapies for heart failure patients.
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Affiliation(s)
- Wenqiang Liu
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA;
| | - Zhijie Wang
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA;
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA
- Correspondence:
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20
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Shah M, KC P, Zhang G. In Vivo Assessment of Decellularized Porcine Myocardial Slice as an Acellular Cardiac Patch. ACS APPLIED MATERIALS & INTERFACES 2019; 11:23893-23900. [PMID: 31188555 PMCID: PMC6948015 DOI: 10.1021/acsami.9b06453] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Acellular cardiac patches made of various biomaterials have shown to improve heart function after myocardial infarction (MI). Extracellular matrix scaffold derived from a decellularized tissue has unique advantages to serve as an acellular cardiac patch due to its biomimetic nature. In this study, we examined the therapeutic outcomes of using a decellularized porcine myocardium slice (dPMS) as an acellular patch in a rat acute MI model. dPMSs with two different thicknesses (300 and 600 μm) were patched to the infarcted area of the rat myocardium, and their effects on cardiac function and host interactions were assessed. We found that the implanted dPMS firmly attached to host myocardium after implantation and prevented thinning of the left ventricular (LV) wall after an MI. A large number of host cells were identified to infiltrate into the implanted dPMS, and a significant number of vessel structures was observed in the dPMS and infarcted area. We detected a significantly higher density of M2 macrophages in the groups treated with dPMSs as compared to the MI group. Contraction of the LV wall and cardiac functional parameters (left ventricular ejection fraction and fractional shortening) was significantly improved in the treatment groups (300 and 600 μm dPMS) 4 weeks after surgery. Our results proved the therapeutic benefits of using dPMS as an acellular cardiac patch for the treatment of acute myocardial infarction.
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Affiliation(s)
- Mickey Shah
- Integrated Bioscience Program, The University of Akron, Akron, Ohio 44325-0302, United States
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio 44325-0302, United States
| | - Pawan KC
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio 44325-0302, United States
| | - Ge Zhang
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio 44325-0302, United States
- Corresponding Author: . Phone: 330-972-5237. Fax: 330-374-8834
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21
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Wang H, Wisneski A, Paulsen MJ, Imbrie-Moore A, Wang Z, Xuan Y, Hernandez HL, Lucian HJ, Eskandari A, Thakore AD, Farry JM, Hironaka CE, von Bornstaedt D, Steele AN, Stapleton LM, Williams KM, Wu MA, MacArthur JW, Woo YJ. Bioengineered analog of stromal cell-derived factor 1α preserves the biaxial mechanical properties of native myocardium after infarction. J Mech Behav Biomed Mater 2019; 96:165-171. [PMID: 31035067 DOI: 10.1016/j.jmbbm.2019.04.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 02/04/2019] [Accepted: 04/11/2019] [Indexed: 01/08/2023]
Abstract
Adverse remodeling of the left ventricle (LV) after myocardial infarction (MI) results in abnormal tissue biomechanics and impaired cardiac function, often leading to heart failure. We hypothesized that intramyocardial delivery of engineered stromal cell-derived factor 1α analog (ESA), our previously-developed supra-efficient pro-angiogenic chemokine, preserves biaxial LV mechanical properties after MI. Male Wistar rats (n = 45) underwent sham surgery (n = 15) or permanent left anterior descending coronary artery ligation. Rats sustaining MI were randomized for intramyocardial injections of either saline (100 μL, n = 15) or ESA (6 μg/kg, n = 15), delivered at four standardized borderzone sites. After 4 weeks, echocardiography was performed, and the hearts were explanted. Tensile testing of the anterolateral LV wall was performed using a displacement-controlled biaxial load frame, and modulus was determined after constitutive modeling. At 4 weeks post-MI, compared to saline controls, ESA-treated hearts had greater wall thickness (1.68 ± 0.05 mm vs 1.42 ± 0.08 mm, p = 0.008), smaller end-diastolic LV internal dimension (6.88 ± 0.29 mm vs 7.69 ± 0.22 mm, p = 0.044), and improved ejection fraction (62.8 ± 3.0% vs 49.4 ± 4.5%, p = 0.014). Histologic analysis revealed significantly reduced infarct size for ESA-treated hearts compared to saline controls (29.4 ± 2.9% vs 41.6 ± 3.1%, p = 0.021). Infarcted hearts treated with ESA exhibited decreased modulus compared to those treated with saline in both the circumferential (211.5 ± 6.9 kPa vs 264.3 ± 12.5 kPa, p = 0.001) and longitudinal axes (194.5 ± 6.5 kPa vs 258.1 ± 14.4 kPa, p < 0.001). In both principal directions, ESA-treated infarcted hearts possessed similar tissue compliance as sham non-infarcted hearts. Overall, intramyocardial ESA therapy improves post-MI ventricular remodeling and function, reduces infarct size, and preserves native LV biaxial mechanical properties.
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Affiliation(s)
- Hanjay Wang
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Andrew Wisneski
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Michael J Paulsen
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Annabel Imbrie-Moore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Zhongjie Wang
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Yue Xuan
- Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | | | - Haley J Lucian
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Anahita Eskandari
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Akshara D Thakore
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Justin M Farry
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Camille E Hironaka
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | | | - Amanda N Steele
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Lyndsay M Stapleton
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Kiah M Williams
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Matthew A Wu
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - John W MacArthur
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA
| | - Y Joseph Woo
- Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA.
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Ahmad F, Prabhu RJ, Liao J, Soe S, Jones MD, Miller J, Berthelson P, Enge D, Copeland KM, Shaabeth S, Johnston R, Maconochie I, Theobald PS. Biomechanical properties and microstructure of neonatal porcine ventricles. J Mech Behav Biomed Mater 2018; 88:18-28. [PMID: 30118921 DOI: 10.1016/j.jmbbm.2018.07.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 06/26/2018] [Accepted: 07/27/2018] [Indexed: 12/29/2022]
Abstract
Neonatal heart disorders represent a major clinical challenge, with congenital heart disease alone affecting 36,000 new-borns annually within the European Union. Surgical intervention to restore normal function includes the implantation of synthetic and biological materials; however, a lack of experimental data describing the mechanical behaviour of neonatal cardiac tissue is likely to contribute to the relatively poor short- and long-term outcome of these implants. This study focused on characterising the mechanical behaviour of neonatal cardiac tissue using a porcine model, to enhance the understanding of how this differs to the equivalent mature tissue. The biomechanical properties of neonatal porcine cardiac tissue were characterised by uniaxial tensile, biaxial tensile, and simple shear loading modes, using samples collected from the anterior and posterior walls of the right and left ventricles. Histological images were prepared using Masson's trichrome staining, to enable assessment of the microstructure and correlation with tissue behaviour. The mechanical tests demonstrated that the neonatal cardiac tissue is non-linear, anisotropic, viscoelastic and heterogeneous. Our data provide a baseline describing the biomechanical behaviour of immature porcine cardiac tissue. Comparison with published data also indicated that the neonatal porcine cardiac tissue exhibits one-half the stiffness of mature porcine tissue in uniaxial extension testing, one-third in biaxial extension testing, and one-fourth stiffness in simple shear testing; hence, it provides an indication as to the relative change in characteristics associated with tissue maturation. These data may prove valuable to researchers investigating neonatal cardiac mechanics.
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Affiliation(s)
| | - Ra J Prabhu
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
| | - Jun Liao
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA; Department of Bioengineering, The University of Texas at Arlington, USA.
| | - Shwe Soe
- School of Engineering, Cardiff University, UK
| | | | - Jonathan Miller
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
| | - Parker Berthelson
- Centre for Advanced Vehicular Systems and Department of Biological Engineering, Mississippi State University, USA
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23
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Nemavhola F. Fibrotic infarction on the LV free wall may alter the mechanics of healthy septal wall during passive filling. Biomed Mater Eng 2017; 28:579-599. [PMID: 29171965 DOI: 10.3233/bme-171698] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effect of myocardial infarction on the global functioning of the heart is well known. Less is understood regarding the effect of LV fibrotic infarction on the cardiac mechanics of the septal wall. To determine this unknown, the stress and strain of septal wall on the healthy and infarcted rat heart model is measured by using finite element models of rat heart geometries. The main objective of this study was to utilized computational methods to study the effect of LV free wall fibrotic infarction on the healthy septal wall. Three-dimensional biventricular rat heart geometries were developed from cardiac magnetic resonance images of a healthy heart and a heart with left ventricular (LV) fibrotic infarction after infarct induction. From these geometries, FE models were established. Three-dimensional biventricular rat heart geometries developed from cardiac magnetic resonance images were used in creating FE models of healthy and infarcted rat hearts. The average radial strain percentage change of the healthy septal wall on the epicardium, mid-wall and endocardium was 61%, 52% and 14% higher than the infarcted septal wall, respectively. It was concluded that the fibrotic infarction has a potential cause the malfunction of the heart due to high myocardial stress and strain that the septal wall experiences.
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Affiliation(s)
- Fulufhelo Nemavhola
- Department of Mechanical and Industrial Engineering, College of science, Engineering and Technology, University of South Africa, Florida, 1710, South Africa. Tel.: +27 (0)11 471 2765; Fax: +27 (0)11 471 2963; E-mail:
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24
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Abdalrahman T, Dubuis L, Green J, Davies N, Franz T. Cellular mechanosensitivity to substrate stiffness decreases with increasing dissimilarity to cell stiffness. Biomech Model Mechanobiol 2017; 16:2063-2075. [PMID: 28733924 DOI: 10.1007/s10237-017-0938-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 07/11/2017] [Indexed: 01/07/2023]
Abstract
Computational modelling has received increasing attention to investigate multi-scale coupled problems in micro-heterogeneous biological structures such as cells. In the current study, we investigated for a single cell the effects of (1) different cell-substrate attachment (2) and different substrate modulus [Formula: see text] on intracellular deformations. A fibroblast was geometrically reconstructed from confocal micrographs. Finite element models of the cell on a planar substrate were developed. Intracellular deformations due to substrate stretch of [Formula: see text], were assessed for: (1) cell-substrate attachment implemented as full basal contact (FC) and 124 focal adhesions (FA), respectively, and [Formula: see text]140 KPa and (2) [Formula: see text], 140, 1000, and 10,000 KPa, respectively, and FA attachment. The largest strains in cytosol, nucleus and cell membrane were higher for FC (1.35[Formula: see text], 0.235[Formula: see text] and 0.6[Formula: see text]) than for FA attachment (0.0952[Formula: see text], 0.0472[Formula: see text] and 0.05[Formula: see text]). For increasing [Formula: see text], the largest maximum principal strain was 4.4[Formula: see text], 5[Formula: see text], 5.3[Formula: see text] and 5.3[Formula: see text] in the membrane, 9.5[Formula: see text], 1.1[Formula: see text], 1.2[Formula: see text] and 1.2[Formula: see text] in the cytosol, and 4.5[Formula: see text], 5.3[Formula: see text], 5.7[Formula: see text] and 5.7[Formula: see text] in the nucleus. The results show (1) the importance of representing FA in cell models and (2) higher cellular mechanical sensitivity for substrate stiffness changes in the range of cell stiffness. The latter indicates that matching substrate stiffness to cell stiffness, and moderate variation of the former is very effective for controlled variation of cell deformation. The developed methodology is useful for parametric studies on cellular mechanics to obtain quantitative data of subcellular strains and stresses that cannot easily be measured experimentally.
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Affiliation(s)
- Tamer Abdalrahman
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, South Africa
| | - Laura Dubuis
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, South Africa
| | - Jason Green
- Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Neil Davies
- Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, South Africa. .,Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK.
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25
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Sirry MS, Butler JR, Patnaik SS, Brazile B, Bertucci R, Claude A, McLaughlin R, Davies NH, Liao J, Franz T. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression. J Mech Behav Biomed Mater 2016; 63:252-264. [DOI: 10.1016/j.jmbbm.2016.06.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 06/20/2016] [Accepted: 06/29/2016] [Indexed: 11/26/2022]
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26
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Sirry MS, Butler JR, Patnaik SS, Brazile B, Bertucci R, Claude A, McLaughlin R, Davies NH, Liao J, Franz T. Infarcted rat myocardium: Data from biaxial tensile and uniaxial compressive testing and analysis of collagen fibre orientation. Data Brief 2016; 8:1338-43. [PMID: 27579338 PMCID: PMC4992040 DOI: 10.1016/j.dib.2016.08.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 07/27/2016] [Accepted: 08/01/2016] [Indexed: 11/29/2022] Open
Abstract
Myocardial infarction was experimentally induced in rat hearts and harvested immediately, 7, 14 and 28 days after the infarction induction. Anterior wall infarct samples underwent biaxial tensile and uniaxial compressive testing. Orientation of collagen fibres was analysed following mechanical testing. In this paper, we present the tensile and compressive stress–strain raw data, the calculated tensile and compressive moduli and the measured angles of collagen orientation. The presented data is associated with the research article titled “Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression” (Sirry et al., 2016) [1].
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Affiliation(s)
- Mazin S Sirry
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory 7925, South Africa; Department of Biomedical Engineering, University of Medical Sciences and Technology, P.O. Box 12810, Khartoum, Sudan
| | - J Ryan Butler
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, MS 39762, USA
| | - Sourav S Patnaik
- Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi, MS 39762, USA
| | - Bryn Brazile
- Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi, MS 39762, USA
| | - Robbin Bertucci
- Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi, MS 39762, USA
| | - Andrew Claude
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, MS 39762, USA
| | - Ron McLaughlin
- Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi, MS 39762, USA
| | - Neil H Davies
- Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory 7925, South Africa
| | - Jun Liao
- Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi, MS 39762, USA
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory 7925, South Africa; Centre for High Performance Computing, Rosebank 7700, South Africa; Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO171BJ, UK
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