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Motchon YD, Sack KL, Sirry MS, Nchejane NJ, Abdalrahman T, Nagawa J, Kruger M, Pauwels E, Van Loo D, De Muynck A, Van Hoorebeke L, Davies NH, Franz T. In silico Mechanics of Stem Cells Intramyocardially Transplanted with a Biomaterial Injectate for Treatment of Myocardial Infarction. Cardiovasc Eng Technol 2024:10.1007/s13239-024-00734-1. [PMID: 38782879 DOI: 10.1007/s13239-024-00734-1] [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: 08/17/2023] [Accepted: 05/12/2024] [Indexed: 05/25/2024]
Abstract
PURPOSE Biomaterial and stem cell delivery are promising approaches to treating myocardial infarction. However, the mechanical and biochemical mechanisms underlying the therapeutic benefits require further clarification. This study aimed to assess the deformation of stem cells injected with the biomaterial into the infarcted heart. METHODS A microstructural finite element model of a mid-wall infarcted myocardial region was developed from ex vivo microcomputed tomography data of a rat heart with left ventricular infarct and intramyocardial biomaterial injectate. Nine cells were numerically seeded in the injectate of the microstructural model. The microstructural and a previously developed biventricular finite element model of the same rat heart were used to quantify the deformation of the cells during a cardiac cycle for a biomaterial elastic modulus (Einj) ranging between 4.1 and 405,900 kPa. RESULTS The transplanted cells' deformation was largest for Einj = 7.4 kPa, matching that of the cells, and decreased for an increase and decrease in Einj. The cell deformation was more sensitive to Einj changes for softer (Einj ≤ 738 kPa) than stiffer biomaterials. CONCLUSIONS Combining the microstructural and biventricular finite element models enables quantifying micromechanics of transplanted cells in the heart. The approach offers a broader scope for in silico investigations of biomaterial and cell therapies for myocardial infarction and other cardiac pathologies.
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Affiliation(s)
- Y D Motchon
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa.
| | - K L Sack
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
- Cardiac Rhythm Management, Medtronic Inc, Minneapolis, MN, USA
| | - M S Sirry
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
- Department of Biomedical Engineering, School of Engineering and Computing, American International University, Al Jahra, Kuwait
| | - N J Nchejane
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - T Abdalrahman
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - J Nagawa
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - M Kruger
- Cardiovascular Research Unit, University of Cape Town, Observatory, South Africa
| | - E Pauwels
- Centre for X-ray Tomography, Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - D Van Loo
- Centre for X-ray Tomography, Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- XRE nv, Bollebergen 2B box 1, Ghent, 9052, Belgium
| | - A De Muynck
- Centre for X-ray Tomography, Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - L Van Hoorebeke
- Centre for X-ray Tomography, Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - N H Davies
- Cardiovascular Research Unit, University of Cape Town, Observatory, South Africa
| | - T Franz
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa.
- Bioengineering Science Research Group, Department of Mechanical Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK.
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2
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Avendaño R, Midgett D, Melvinsdottir I, Thorn SL, Uman S, Pickell Z, Lee SR, Liu Z, Mamarian M, Duncan JS, Spinale FG, Burdick JA, Sinusas AJ. Improvement in cardiac function and regional LV strain following intramyocardial injection of a theranostic hydrogel early postmyocardial infarction in a porcine model. J Appl Physiol (1985) 2023; 135:405-420. [PMID: 37318987 PMCID: PMC10538987 DOI: 10.1152/japplphysiol.00342.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 05/23/2023] [Accepted: 06/14/2023] [Indexed: 06/17/2023] Open
Abstract
Myocardial infarction (MI) is often complicated by left ventricular (LV) remodeling and heart failure. We evaluated the feasibility of a multimodality imaging approach to guide delivery of an imageable hydrogel and assessed LV functional changes with therapy. Yorkshire pigs underwent surgical occlusions of branches of the left anterior descending and/or circumflex artery to create an anterolateral MI. We evaluated the hemodynamic and mechanical effects of intramyocardial delivery of an imageable hydrogel in the central infarct area (Hydrogel group, n = 8) and a Control group (n = 5) early post-MI. LV and aortic pressure and ECG were measured and contrast cineCT angiography was performed at baseline, 60 min post-MI, and 90 min post-hydrogel delivery. LV hemodynamic indices, pressure-volume measures, and normalized regional and global strains were measured and compared. Both Control and Hydrogel groups demonstrated a decline in heart rate, LV pressure, stroke volume, ejection fraction, and pressure-volume loop area, and an increase in myocardial performance (Tei) index and supply/demand (S/D) ratio. After hydrogel delivery, Tei index and S/D ratio were reduced to baseline levels, diastolic and systolic functional indices either stabilized or improved, and radial strain and circumferential strain increased significantly in the MI regions (ENrr: +52.7%, ENcc: +44.1%). However, the Control group demonstrated a progressive decline in all functional indices to levels significantly below those of Hydrogel group. Thus, acute intramyocardial delivery of a novel imageable hydrogel to MI region resulted in rapid stabilization or improvement in LV hemodynamics and function.NEW & NOTEWORTHY Our study demonstrates that contrast cineCT imaging can be used to evaluate the acute effects of intramyocardial delivery of a therapeutic hydrogel to the central MI region early post MI, which resulted in a rapid stabilization of LV hemodynamics and improvement in regional and global LV function.
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Affiliation(s)
- Ricardo Avendaño
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Dan Midgett
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States
| | - Inga Melvinsdottir
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Stephanie L Thorn
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Selen Uman
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Zachary Pickell
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Shin Rong Lee
- Department of Surgery, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Zhao Liu
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States
| | - Marina Mamarian
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
| | - James S Duncan
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, Connecticut, United States
| | - Francis G Spinale
- Department of Cell Biology & Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina, United States
| | - Jason A Burdick
- Biofrontiers Institute, University of Colorado Boulder, Boulder, Colorado, United States
- Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado, United States
| | - Albert J Sinusas
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States
- Department of Biomedical Engineering, Yale University, New Haven, Connecticut, United States
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, Connecticut, United States
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3
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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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4
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Midgett DE, Thorn SL, Ahn SS, Uman S, Avendano R, Melvinsdottir I, Lysyy T, Kim JS, Duncan JS, Humphrey JD, Papademetris X, Burdick JA, Sinusas AJ. CineCT platform for in vivo and ex vivo measurement of 3D high resolution Lagrangian strains in the left ventricle following myocardial infarction and intramyocardial delivery of theranostic hydrogel. J Mol Cell Cardiol 2022; 166:74-90. [PMID: 35227737 PMCID: PMC9035115 DOI: 10.1016/j.yjmcc.2022.02.004] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 02/10/2022] [Accepted: 02/16/2022] [Indexed: 02/07/2023]
Abstract
Myocardial infarction (MI) produces acute changes in strain and stiffness within the infarct that can affect remote areas of the left ventricle (LV) and drive pathological remodeling. We hypothesized that intramyocardial delivery of a hydrogel within the MI region would lower wall stress and reduce adverse remodeling in Yorkshire pigs (n = 5). 99mTc-Tetrofosmin SPECT imaging defined the location and geometry of induced MI and border regions in pigs, and in vivo and ex vivo contrast cine computed tomography (cineCT) quantified deformations of the LV myocardium. Serial in vivo cineCT imaging provided data in hearts from control pigs (n = 3) and data from pigs (n = 5) under baseline conditions before MI induction, post-MI day 3, post-MI day 7, and one hour after intramyocardial delivery of a hyaluronic acid (HA)-based hydrogel with shear-thinning and self-healing properties to the central infarct area. Isolated, excised hearts underwent similar cineCT imaging using an ex vivo perfused heart preparation with cyclic LV pressurization. Deformations were evaluated using nonlinear image registration of cineCT volumes between end-diastole (ED) and end-systole (ES), and 3D Lagrangian strains were calculated from the displacement gradients. Post-MI day 3, radial, circumferential, maximum principal, and shear strains were reduced within the MI region (p < 0.04) but were unchanged in normal regions (p > 0.6), and LV end diastolic volume (LV EDV) increased (p = 0.004), while ejection fraction (EF) and stroke volume (SV) decreased (p < 0.02). Post-MI day 7, radial strains in MI border zones increased (p = 0.04) and dilation of LV EDV continued (p = 0.052). There was a significant negative linear correlation between regional radial and maximum principal/shear strains and percent infarcted tissue in all hearts (R2 > 0.47, p < 0.004), indicating that cineCT strain measures could predict MI location and degree of injury. Post-hydrogel day 7 post-MI, LV EDV was significantly reduced (p = 0.009), EF increased (p = 0.048), and radial (p = 0.021), maximum principal (p = 0.051), and shear strain (p = 0.047) increased within regions bordering the infarct. A smaller strain improvement within the infarct and normal regions was also noted on average along with an improvement in SV in 4 out of 5 hearts. CineCT provides a reliable method to assess regional changes in strains post-MI and the therapeutic effects of intramyocardial hydrogel delivery.
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Affiliation(s)
- D E Midgett
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States of America; Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
| | - S L Thorn
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States of America
| | - S S Ahn
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
| | - S Uman
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States of America
| | - R Avendano
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States of America
| | - I Melvinsdottir
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States of America
| | - T Lysyy
- Department of Surgery, Yale University School of Medicine, New Haven, CT, United States of America
| | - J S Kim
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States of America
| | - J S Duncan
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America; Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States of America
| | - J D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
| | - X Papademetris
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America; Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States of America
| | - J A Burdick
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States of America
| | - A J Sinusas
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, United States of America; Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America; Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT, United States of America.
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5
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Dieterle MP, Husari A, Steinberg T, Wang X, Ramminger I, Tomakidi P. From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues. Biomolecules 2021; 11:824. [PMID: 34073044 PMCID: PMC8228498 DOI: 10.3390/biom11060824] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/25/2021] [Accepted: 05/27/2021] [Indexed: 02/07/2023] Open
Abstract
Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.
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Affiliation(s)
- Martin Philipp Dieterle
- Center for Dental Medicine, Division of Oral Biotechnology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany; (M.P.D.); (X.W.); (I.R.); (P.T.)
| | - Ayman Husari
- Center for Dental Medicine, Department of Orthodontics, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany;
- Faculty of Engineering, University of Freiburg, Georges-Köhler-Allee 101, 79110 Freiburg, Germany
| | - Thorsten Steinberg
- Center for Dental Medicine, Division of Oral Biotechnology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany; (M.P.D.); (X.W.); (I.R.); (P.T.)
| | - Xiaoling Wang
- Center for Dental Medicine, Division of Oral Biotechnology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany; (M.P.D.); (X.W.); (I.R.); (P.T.)
| | - Imke Ramminger
- Center for Dental Medicine, Division of Oral Biotechnology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany; (M.P.D.); (X.W.); (I.R.); (P.T.)
| | - Pascal Tomakidi
- Center for Dental Medicine, Division of Oral Biotechnology, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hugstetterstr. 55, 79106 Freiburg, Germany; (M.P.D.); (X.W.); (I.R.); (P.T.)
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6
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Fan Y, Ronan W, Teh I, Schneider JE, Varela CE, Whyte W, McHugh P, Leen S, Roche E. A comparison of two quasi-static computational models for assessment of intra-myocardial injection as a therapeutic strategy for heart failure. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3213. [PMID: 31062508 DOI: 10.1002/cnm.3213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
Myocardial infarction, or heart attack, is the leading cause of mortality globally. Although the treatment of myocardial infarct has improved significantly, scar tissue that persists can often lead to increased stress and adverse remodeling of surrounding tissue and ultimately to heart failure. Intra-myocardial injection of biomaterials represents a potential treatment to attenuate remodeling, mitigate degeneration, and reverse the disease process in the tissue. In vivo experiments on animal models have shown functional benefits of this therapeutic strategy. However, a poor understanding of the optimal injection pattern, volume, and material properties has acted as a barrier to its widespread clinical adoption. In this study, we developed two quasistatic finite element simulations of the left ventricle to investigate the mechanical effect of intra-myocardial injection. The first model employed an idealized left ventricular geometry with rule-based cardiomyocyte orientation. The second model employed a subject-specific left ventricular geometry with cardiomyocyte orientation from diffusion tensor magnetic resonance imaging. Both models predicted cardiac parameters including ejection fraction, systolic wall thickening, and ventricular twist that matched experimentally reported values. All injection simulations showed cardiomyocyte stress attenuation, offering an explanation for the mechanical reinforcement benefit associated with injection. The study also enabled a comparison of injection location and the corresponding effect on cardiac performance at different stages of the cardiac cycle. While the idealized model has lower fidelity, it predicts cardiac function and differentiates the effects of injection location. Both models represent versatile in silico tools to guide optimal strategy in terms of injection number, volume, site, and material properties.
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Affiliation(s)
- Yiling Fan
- Mechanical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - William Ronan
- Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Irvin Teh
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Jurgen E Schneider
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Claudia E Varela
- Institute for Medical Engineering Science, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Harvard-MIT Program in Health Sciences and Technology, Cambridge, Massachusetts
| | - William Whyte
- Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland (RCSI), Dublin, 2, Ireland
- Trinity Centre for Bioengineering, Trinity College Dublin (TCD), College Green, Dublin, 2, Ireland
- Advanced Materials and BioEngineering Research (AMBER) Centre, RCSI, NUIG & TCD, Dublin, 2, Ireland
- John A Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts
| | - Peter McHugh
- Biomechanics Research Centre, Biomedical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Sean Leen
- Mechanical Engineering, College of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
| | - Ellen Roche
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Institute for Medical Engineering Science, Massachusetts Institute of Technology, Cambridge, Massachusetts
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7
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Ngoepe M, Passos A, Balabani S, King J, Lynn A, Moodley J, Swanson L, Bezuidenhout D, Davies NH, Franz T. A Preliminary Computational Investigation Into the Flow of PEG in Rat Myocardial Tissue for Regenerative Therapy. Front Cardiovasc Med 2019; 6:104. [PMID: 31448288 PMCID: PMC6692440 DOI: 10.3389/fcvm.2019.00104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 07/16/2019] [Indexed: 11/30/2022] Open
Abstract
Myocardial infarction (MI), a type of cardiovascular disease, affects a significant proportion of people around the world. Traditionally, non-communicable chronic diseases were largely associated with aging populations in higher income countries. It is now evident that low- to middle-income countries are also affected and in these settings, younger individuals are at high risk. Currently, interventions for MI prolong the time to heart failure. Regenerative medicine and stem cell therapy have the potential to mitigate the effects of MI and to significantly improve the quality of life for patients. The main drawback with these therapies is that many of the injected cells are lost due to the vigorous motion of the heart. Great effort has been directed toward the development of scaffolds which can be injected alongside stem cells, in an attempt to improve retention and cell engraftment. In some cases, the scaffold alone has been seen to improve heart function. This study focuses on a synthetic polyethylene glycol (PEG) based hydrogel which is injected into the heart to improve left ventricular function following MI. Many studies in literature characterize PEG as a Newtonian fluid within a specified shear rate range, on the macroscale. The aim of the study is to characterize the flow of a 20 kDa PEG on the microscale, where the behavior is likely to deviate from macroscale flow patterns. Micro particle image velocimetry (μPIV) is used to observe flow behavior in microchannels, representing the gaps in myocardial tissue. The fluid exhibits non-Newtonian, shear-thinning behavior at this scale. Idealized two-dimensional computational fluid dynamics (CFD) models of PEG flow in microchannels are then developed and validated using the μPIV study. The validated computational model is applied to a realistic, microscopy-derived myocardial tissue model. From the realistic tissue reconstruction, it is evident that the myocardial flow region plays an important role in the distribution of PEG, and therefore, in the retention of material.
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Affiliation(s)
- Malebogo Ngoepe
- Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa.,Wallenberg Research Centre, Stellenbosch Institute of Advanced Study, Stellenbosch University, Stellenbosch, South Africa
| | - Andreas Passos
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Stavroula Balabani
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Jesse King
- Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa
| | - Anastasia Lynn
- Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa
| | - Jasanth Moodley
- Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa
| | - Liam Swanson
- Department of Mechanical Engineering, University of Cape Town, Rondebosch, South Africa
| | - Deon Bezuidenhout
- Cardiovascular Research Unit, Department of Surgery, University of Cape Town, Observatory, South Africa
| | - Neil H Davies
- Cardiovascular Research Unit, Department of Surgery, University of Cape Town, Observatory, South Africa
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa.,Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom
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8
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Peirlinck M, Sack KL, De Backer P, Morais P, Segers P, Franz T, De Beule M. Kinematic boundary conditions substantially impact in silico ventricular function. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3151. [PMID: 30188608 DOI: 10.1002/cnm.3151] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/28/2018] [Accepted: 09/01/2018] [Indexed: 06/08/2023]
Abstract
Computational cardiac mechanical models, individualized to the patient, have the potential to elucidate the fundamentals of cardiac (patho-)physiology, enable non-invasive quantification of clinically significant metrics (eg, stiffness, active contraction, work), and anticipate the potential efficacy of therapeutic cardiovascular intervention. In a clinical setting, however, the available imaging resolution is often limited, which limits cardiac models to focus on the ventricles, without including the atria, valves, and proximal arteries and veins. In such models, the absence of surrounding structures needs to be accounted for by imposing realistic kinematic boundary conditions, which, for prognostic purposes, are preferably generic and thus non-image derived. Unfortunately, the literature on cardiac models shows no consistent approach to kinematically constrain the myocardium. The impact of different approaches (eg, fully constrained base, constrained epi-ring) on the predictive capacity of cardiac mechanical models has not been thoroughly studied. For that reason, this study first gives an overview of current approaches to kinematically constrain (bi) ventricular models. Next, we developed a patient-specific in silico biventricular model that compares well with literature and in vivo recorded strains. Alternative constraints were introduced to assess the influence of commonly used mechanical boundary conditions on both the predicted global functional behavior of the in-silico heart (cavity volumes, stroke volume, ejection fraction) and local strain distributions. Meaningful differences in global functioning were found between different kinematic anchoring strategies, which brought forward the importance of selecting appropriate boundary conditions for biventricular models that, in the near future, may inform clinical intervention. However, whilst statistically significant differences were also found in local strain distributions, these differences were minor and mostly confined to the region close to the applied boundary conditions.
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Affiliation(s)
- Mathias Peirlinck
- Biofluid, Tissue and Solid Mechanics for Medical Applications Lab (IBiTech, bioMMeda), Ghent University, Ghent, Belgium
| | - Kevin L Sack
- Department of Surgery, University of California at San Francisco, San Francisco, CA, USA
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, Observatory, South Africa
| | | | - Pedro Morais
- Lab on Cardiovascular Imaging and Dynamics, Department of Cardiovascular Sciences, KULeuven-University of Leuven, Leuven, Belgium
| | - Patrick Segers
- Biofluid, Tissue and Solid Mechanics for Medical Applications Lab (IBiTech, bioMMeda), Ghent University, Ghent, Belgium
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, Observatory, South Africa
- Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - Matthieu De Beule
- Biofluid, Tissue and Solid Mechanics for Medical Applications Lab (IBiTech, bioMMeda), Ghent University, Ghent, Belgium
- FEops nv, Ghent, Belgium
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9
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Sack KL, Davies NH, Guccione JM, Franz T. Personalised computational cardiology: Patient-specific modelling in cardiac mechanics and biomaterial injection therapies for myocardial infarction. Heart Fail Rev 2018; 21:815-826. [PMID: 26833320 PMCID: PMC4969231 DOI: 10.1007/s10741-016-9528-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Predictive computational modelling in biomedical research offers the potential to integrate diverse data, uncover biological mechanisms that are not easily accessible through experimental methods and expose gaps in knowledge requiring further research. Recent developments in computing and diagnostic technologies have initiated the advancement of computational models in terms of complexity and specificity. Consequently, computational modelling can increasingly be utilised as enabling and complementing modality in the clinic—with medical decisions and interventions being personalised. Myocardial infarction and heart failure are amongst the leading causes of death globally despite optimal modern treatment. The development of novel MI therapies is challenging and may be greatly facilitated through predictive modelling. Here, we review the advances in patient-specific modelling of cardiac mechanics, distinguishing specificity in cardiac geometry, myofibre architecture and mechanical tissue properties. Thereafter, the focus narrows to the mechanics of the infarcted heart and treatment of myocardial infarction with particular attention on intramyocardial biomaterial delivery.
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Affiliation(s)
- Kevin L Sack
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Private Bag X3, 7935, Observatory, South Africa
| | - Neil H Davies
- Cardiovascular Research Unit, MRC IUCHRU, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Julius M Guccione
- Department of Surgery, University of California at San Francisco, San Francisco, CA, USA
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Private Bag X3, 7935, Observatory, South Africa.
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10
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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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11
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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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12
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Wise P, Davies NH, Sirry MS, Kortsmit J, Dubuis L, Chai CK, Baaijens FPT, Franz T. Excessive volume of hydrogel injectates may compromise the efficacy for the treatment of acute myocardial infarction. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2016; 32:e02772. [PMID: 26822845 DOI: 10.1002/cnm.2772] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 01/11/2016] [Accepted: 01/25/2016] [Indexed: 06/05/2023]
Abstract
Biomaterial injectates are promising as a therapy for myocardial infarction to inhibit the adverse ventricular remodeling. The current study explored interrelated effects of injectate volume and infarct size on treatment efficacy. A finite element model of a rat heart was utilized to represent ischemic infarcts of 10%, 20%, and 38% of left ventricular wall volume and polyethylene glycol hydrogel injectates of 25%, 50%, and 75% of the infarct volume. Ejection fraction was 49.7% in the healthy left ventricle and 44.9%, 46.4%, 47.4%, and 47.3% in the untreated 10% infarct and treated with 25%, 50%, and 75% injectate, respectively. Maximum end-systolic infarct fiber stress was 41.6, 53.4, 44.7, 44.0, and 45.3 kPa in the healthy heart, the untreated 10% infarct, and when treated with the three injectate volumes, respectively. Treating the 10% and 38% infarcts with the 25% injectate volume reduced the maximum end-systolic fiber stress by 16.3% and 34.7% and the associated strain by 30.2% and 9.8%, respectively. The results indicate the existence of a threshold for injectate volume above which efficacy does not further increase but may decrease. The efficacy of an injectate in reducing infarct stress and strain changes with infarct size. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Peter Wise
- Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Neil H Davies
- Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Mazin S Sirry
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
- Department of Biomedical Engineering, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Jeroen Kortsmit
- Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
| | - Laura Dubuis
- Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory, South Africa
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - Chen-Ket Chai
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Frank P T Baaijens
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Thomas Franz
- Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
- Research Office, University of Cape Town, Mowbray, South Africa
- Center for High Performance Computing, Rosebank, South Africa
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13
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Abstract
The heart pumps blood to maintain circulation and ensure the delivery of oxygenated blood to all the organs of the body. Mechanics play a critical role in governing and regulating heart function under both normal and pathological conditions. Biological processes and mechanical stress are coupled together in regulating myocyte function and extracellular matrix structure thus controlling heart function. Here, we offer a brief introduction to the biomechanics of left ventricular function and then summarize recent progress in the study of the effects of mechanical stress on ventricular wall remodeling and cardiac function as well as the effects of wall mechanical properties on cardiac function in normal and dysfunctional hearts. Various mechanical models to determine wall stress and cardiac function in normal and diseased hearts with both systolic and diastolic dysfunction are discussed. The results of these studies have enhanced our understanding of the biomechanical mechanism in the development and remodeling of normal and dysfunctional hearts. Biomechanics provide a tool to understand the mechanism of left ventricular remodeling in diastolic and systolic dysfunction and guidance in designing and developing new treatments.
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Affiliation(s)
- Andrew P. Voorhees
- Department of Mechanical Engineering, The University of Texas at San Antonio, Biomedical Engineering Program, UTSA-UTHSCSA
| | - Hai-Chao Han
- Department of Mechanical Engineering, The University of Texas at San Antonio, Biomedical Engineering Program, UTSA-UTHSCSA
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14
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Komeri R, Thankam FG, Muthu J. Influence of matrix and bulk behaviour of an injectable hydrogel on the survival of encapsulated cardiac cells. RSC Adv 2015. [DOI: 10.1039/c4ra16254d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The influence of physicochemical, morphological and mechanical behaviour of an injectable poly(propylene fumarate-co-ethylene glycol)/PEGDA hydrogel on the viability and proliferation of encapsulated cardiac cells was investigated.
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Affiliation(s)
- Remya Komeri
- Sree Chitra Tirunal Institute for Medical Sciences and Technology
- Polymer Science Division
- Thiruvananthapuram – 695 012
- India
| | - Finosh Gnanaprakasam Thankam
- Sree Chitra Tirunal Institute for Medical Sciences and Technology
- Polymer Science Division
- Thiruvananthapuram – 695 012
- India
| | - Jayabalan Muthu
- Sree Chitra Tirunal Institute for Medical Sciences and Technology
- Polymer Science Division
- Thiruvananthapuram – 695 012
- India
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15
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Legner D, Skatulla S, MBewu J, Rama RR, Reddy BD, Sansour C, Davies NH, Franz T. Studying the influence of hydrogel injections into the infarcted left ventricle using the element-free Galerkin method. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2014; 30:416-429. [PMID: 24574184 DOI: 10.1002/cnm.2610] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Revised: 09/07/2013] [Accepted: 10/11/2013] [Indexed: 06/03/2023]
Abstract
Myocardial infarction is an increasing health problem worldwide. Because of an under-supply of blood, the cardiomyocytes in the affected region permanently lose their ability to contract. This in turn gradually weakens the overall heart function. A new therapeutic approach based on the injection of a gel into the infarcted area aims to support the healing and to inhibit adverse remodelling that can lead to heart failure. A computational model is the basis for obtaining a better understanding of the heart mechanics, in particular, how myocardial infarction and gel injections affect its pumping performance. A strain invariant-based stored energy function is proposed to account for the passive mechanical behaviour of the model, which also makes provision for active contraction. To incorporate injections an additive homogenization approach is introduced. The numerical framework is developed using an in-house code based on the element-free Galerkin method. The main focus of this contribution is to investigate the influence of gel injections on the mechanics of the left ventricle during the diastolic filling and systolic isovolumetric (isochoric) contraction phases. It is found that gel injections are able to reduce the elevated fibre stresses caused by an infarct.
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Affiliation(s)
- D Legner
- Centre for Research in Computational and Applied Mechanics, University of Cape Town, Cape Town, South Africa; Computational Continuum Mechanics Group, Department of Civil Engineering, University of Cape Town, Cape Town, South Africa
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16
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Experimental and computational investigation of altered mechanical properties in myocardium after hydrogel injection. Ann Biomed Eng 2013; 42:1546-56. [PMID: 24271262 DOI: 10.1007/s10439-013-0937-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 11/08/2013] [Indexed: 10/26/2022]
Abstract
The material properties of myocardium are an important determinant of global left ventricular function. Myocardial infarction results in a series of maladaptive geometric alterations which lead to increased stress and risk of heart failure. In vivo studies have demonstrated that material injection can mitigate these changes. More importantly, the material properties of these injectates can be tuned to minimize wall thinning and ventricular dilation. The current investigation combines experimental data and finite element modeling to correlate how injectate mechanics and volume influence myocardial wall stress. Experimentally, mechanics were characterized with biaxial testing and injected hydrogel volumes were measured with magnetic resonance imaging. Injection of hyaluronic acid hydrogel increased the stiffness of the myocardium/hydrogel composite region in an anisotropic manner, significantly increasing the modulus in the longitudinal direction compared to control myocardium. Increased stiffness, in combination with increased volume from hydrogel injection, reduced the global average fiber stress by ~14% and the transmural average by ~26% in the simulations. Additionally, stiffening in an anisotropic manner enhanced the influence of hydrogel treatment in decreasing stress. Overall, this work provides insight on how injectable biomaterials can be used to attenuate wall stress and provides tools to further optimize material properties for therapeutic applications.
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17
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Sirry MS, Davies NH, Kadner K, Dubuis L, Saleh MG, Meintjes EM, Spottiswoode BS, Zilla P, Franz T. Micro-structurally detailed model of a therapeutic hydrogel injectate in a rat biventricular cardiac geometry for computational simulations. Comput Methods Biomech Biomed Engin 2013; 18:325-31. [PMID: 23682845 DOI: 10.1080/10255842.2013.793765] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Biomaterial injection-based therapies have showed cautious success in restoration of cardiac function and prevention of adverse remodelling into heart failure after myocardial infarction (MI). However, the underlying mechanisms are not well understood. Computational studies utilised simplified representations of the therapeutic myocardial injectates. Wistar rats underwent experimental infarction followed by immediate injection of polyethylene glycol hydrogel in the infarct region. Hearts were explanted, cryo-sectioned and the region with the injectate histologically analysed. Histological micrographs were used to reconstruct the dispersed hydrogel injectate. Cardiac magnetic resonance imaging data from a healthy rat were used to obtain an end-diastolic biventricular geometry which was subsequently adjusted and combined with the injectate model. The computational geometry of the injectate exhibited microscopic structural details found the in situ. The combination of injectate and cardiac geometry provides realistic geometries for multiscale computational studies of intra-myocardial injectate therapies for the rat model that has been widely used for MI research.
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Affiliation(s)
- Mazin S Sirry
- a Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town , Private Bag X3, 7935 Observatory , South Africa
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