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Sadeghinia MJ, Persson RM, Ellensen VS, Haaverstad R, Holzapfel GA, Skallerud B, Prot V, Urheim S. Quantified planar collagen distribution in healthy and degenerative mitral valve: biomechanical and clinical implications. Sci Rep 2024; 14:15670. [PMID: 38977735 PMCID: PMC11231298 DOI: 10.1038/s41598-024-65598-w] [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: 03/19/2024] [Accepted: 06/21/2024] [Indexed: 07/10/2024] Open
Abstract
Degenerative mitral valve disease is a common valvular disease with two arguably distinct phenotypes: fibroelastic deficiency and Barlow's disease. These phenotypes significantly alter the microstructures of the leaflets, particularly the collagen fibers, which are the main mechanical load carriers. The predominant method of investigation is histological sections. However, the sections are cut transmurally and provide a lateral view of the microstructure of the leaflet, while the mechanics and function are determined by the planar arrangement of the collagen fibers. This study, for the first time, quantitatively examined planar collagen distribution quantitatively in health and disease using second harmonic generation microscopy throughout the thickness of the mitral valve leaflets. Twenty diseased samples from eighteen patients and six control samples were included in this study. Healthy tissue had highly aligned collagen fibers. In fibroelastic deficiency they are less aligned and in Barlow's disease they are completely dispersed. In both diseases, collagen fibers have two preferred orientations, which, in contrast to the almost constant one orientation in healthy tissues, also vary across the thickness. The results indicate altered in vivo mechanical stresses and strains on the mitral valve leaflets as a result of disease-related collagen remodeling, which in turn triggers further remodeling.
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Affiliation(s)
- Mohammad Javad Sadeghinia
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
| | - Robert Matongo Persson
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
| | | | - Rune Haaverstad
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
| | - Gerhard A Holzapfel
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
- Institute of Biomechanics, Graz University of Technology, Graz, Austria
| | - Bjørn Skallerud
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway
| | - Victorien Prot
- Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands Vei 1A, 7034, Trondheim, Norway.
| | - Stig Urheim
- Department of Heart Disease, Haukeland University Hospital, Bergen, Norway
- Institute of Clinical Science, Medical Faculty, University of Bergen, Bergen, Norway
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2
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Mathur M, Malinowski M, Jazwiec T, Timek TA, Rausch MK. Leaflet remodeling reduces tricuspid valve function in a computational model. J Mech Behav Biomed Mater 2024; 152:106453. [PMID: 38335648 PMCID: PMC11048730 DOI: 10.1016/j.jmbbm.2024.106453] [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: 07/28/2023] [Revised: 01/23/2024] [Accepted: 01/31/2024] [Indexed: 02/12/2024]
Abstract
Tricuspid valve leaflets have historically been considered "passive flaps". However, we have recently shown that tricuspid leaflets actively remodel in sheep with functional tricuspid regurgitation. We hypothesize that these remodeling-induced changes reduce leaflet coaptation and, therefore, contribute to valvular dysfunction. To test this, we simulated the impact of remodeling-induced changes on valve mechanics in a reverse-engineered computer model of the human tricuspid valve. To this end, we combined right-heart pressures and tricuspid annular dynamics recorded in an ex vivo beating heart, with subject-matched in vitro measurements of valve geometry and material properties, to build a subject-specific finite element model. Next, we modified the annular geometry and boundary conditions to mimic changes seen in patients with pulmonary hypertension. In this model, we then increased leaflet thickness and stiffness and reduced the stretch at which leaflets stiffen, which we call "transition-λ." Subsequently, we quantified mean leaflet stresses, leaflet systolic angles, and coaptation area as measures of valve function. We found that leaflet stresses, leaflet systolic angle, and coaptation area are sensitive to independent changes in stiffness, thickness, and transition-λ. When combining thickening, stiffening, and changes in transition-λ, we found that anterior and posterior leaflet stresses decreased by 26% and 28%, respectively. Furthermore, systolic angles increased by 43%, and coaptation area decreased by 66%; thereby impeding valve function. While only a computational study, we provide the first evidence that remodeling-induced leaflet thickening and stiffening may contribute to valvular dysfunction. Targeted suppression of such changes in diseased valves could restore normal valve mechanics and promote leaflet coaptation.
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Affiliation(s)
- Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, 78712, TX, United States of America
| | - Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, 221 Michigan Street NE Suite 300, Grand Rapids, 49503, MI, United States of America; Department of Cardiac Surgery, Medical University of Silesia, Katowice, Poland
| | - Tomasz Jazwiec
- Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, 221 Michigan Street NE Suite 300, Grand Rapids, 49503, MI, United States of America
| | - Manuel K Rausch
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, 78712, TX, United States of America; Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, 2617 Wichita Street, Austin, 78712, TX, United States of America; Department of Biomedical Engineering, University of Texas at Austin, 107 W Dean Keeton Street, Austin, 78712, TX, United States of America; Oden Institute for Computational Engineering and Sciences, University of Texas at Austin, 201 E 24th Street, Austin, 78712, TX, United States of America.
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3
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Peters MC, Kruithof BPT, Bouten CVC, Voets IK, van den Bogaerdt A, Goumans MJ, van Wijk A. Preservation of human heart valves for replacement in children with heart valve disease: past, present and future. Cell Tissue Bank 2024; 25:67-85. [PMID: 36725733 PMCID: PMC10902036 DOI: 10.1007/s10561-023-10076-2] [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: 01/12/2023] [Accepted: 01/29/2023] [Indexed: 02/03/2023]
Abstract
Valvular heart disease affects 30% of the new-borns with congenital heart disease. Valve replacement of semilunar valves by mechanical, bioprosthetic or donor allograft valves is the main treatment approach. However, none of the replacements provides a viable valve that can grow and/or adapt with the growth of the child leading to re-operation throughout life. In this study, we review the impact of donor valve preservation on moving towards a more viable valve alternative for valve replacements in children or young adults.
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Affiliation(s)
- M C Peters
- Department of Pediatric Cardiothoracic Surgery, Wilhelmina Children's Hospital, University Medical Center Utrecht, 3584 EA, Utrecht, The Netherlands.
- Department of Cardiovascular Cell Biology, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands.
- Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
| | - B P T Kruithof
- Department of Cardiovascular Cell Biology, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
- Department of Cardiology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands
| | - C V C Bouten
- Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - I K Voets
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - A van den Bogaerdt
- Heart Valve Department, ETB-BISLIFE Multi Tissue Center, 2333 BD, Beverwijk, The Netherlands
| | - M J Goumans
- Department of Cardiovascular Cell Biology, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | - A van Wijk
- Department of Pediatric Cardiothoracic Surgery, Wilhelmina Children's Hospital, University Medical Center Utrecht, 3584 EA, Utrecht, The Netherlands
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Iwasieczko A, Gaddam M, Gaweda B, Goodyke A, Mathur M, Lin CY, Zagorski J, Solarewicz M, Cohle S, Rausch M, Timek TA. Valvular complex and tissue remodelling in ovine functional tricuspid regurgitation. Eur J Cardiothorac Surg 2023; 63:ezad115. [PMID: 36951551 DOI: 10.1093/ejcts/ezad115] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 03/06/2023] [Accepted: 03/22/2023] [Indexed: 03/24/2023] Open
Abstract
OBJECTIVES Pathophysiology of function tricuspid regurgitation (FTR) is incompletely understood. We set out to comprehensively evaluate geometric and tissue remodelling of the tricuspid valve complex in ovine FTR. METHODS Twenty adult sheep underwent left thoracotomy and pulmonary artery banding (PAB) to induce right heart pressure overload and FTR. After 8 weeks, 17 surviving animals and 10 healthy controls (CTL) underwent sternotomy, echocardiography and implantation of sonomicrometry crystals on right ventricle and tricuspid valvular apparatus. Haemodynamic and sonomicrometry data were acquired in all animals after weaning from cardiopulmonary bypass. Leaflet tissue was harvested for pentachrome histologic analysis and biomechanical testing. RESULTS Animal weight was 62 ± 5 and 63 ± 3 kg for CTL and PAB, respectively (P = 0.6). At terminal procedure, systolic pulmonary artery pressure was 22 ± 3 and 40 ± 7 mmHg for CTL and PAB, respectively (P = 0.0001). The mean TR grade (+0-4) was 0.8 ± 0.4 and 3.2 ± 1.2 (P = 0.0001) for control and banded animals, respectively. Right ventricle volume (126 ± 13 vs 172 ± 34 ml, P = 0.0019), tricuspid annular area (651 ± 109 vs 865 ± 247 mm2, P = 0.037) and area between papillary muscle tips (162 ± 51 vs 302 ± 75 mm2, P = 0.001) increased substantially while systolic excursion of anterior leaflet decreased significantly (23.8 ± 6.1° vs 7.4 ± 4.5°, P = 0.001) with banding. Total leaflet surface area increased from 806 ± 94 to 953 ± 148 mm2 (P = 0.009), and leaflets became thicker and stiffer. CONCLUSIONS Detailed analysis of the tricuspid valve complex revealed significant ventricular, annular, subvalvular and leaflet remodelling to be associated with ovine functional tricuspid regurgitation. Durable surgical repair of severe FTR may require a multi-level approach to the valvular apparatus.
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Affiliation(s)
- Artur Iwasieczko
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac Surgery, State Clinical Hospital Number 2, University of Rzeszow, Rzeszow, Poland
| | | | - Boguslaw Gaweda
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
- Department of Cardiac Surgery, State Clinical Hospital Number 2, University of Rzeszow, Rzeszow, Poland
| | - Austin Goodyke
- Research Department, Spectrum Health, Grand Rapids, MI, USA
| | - Mrudang Mathur
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA
| | - Chien-Yu Lin
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA
| | | | - Monica Solarewicz
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
| | - Stephen Cohle
- Department of Pathology, Spectrum Health, Grand Rapids, MI, USA
| | - Manuel Rausch
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, USA
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, USA
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5
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Sadeghinia MJ, Aguilera HM, Holzapfel GA, Urheim S, Persson RM, Ellensen VS, Haaverstad R, Skallerud B, Prot V. Mechanical Behavior and Collagen Structure of Degenerative Mitral Valve Leaflets and a Finite Element Model of Primary Mitral Regurgitation. Acta Biomater 2023; 164:269-281. [PMID: 37003496 DOI: 10.1016/j.actbio.2023.03.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/03/2023] [Accepted: 03/20/2023] [Indexed: 04/03/2023]
Abstract
Degenerative mitral valve disease is the main cause of primary mitral regurgitation with two phenotypes: fibroelastic deficiency (FED) often with localized myxomatous degeneration and diffuse myxomatous degeneration or Barlow's disease. Myxomatous degeneration disrupts the microstructure of the mitral valve leaflets, particularly the collagen fibers, which affects the mechanical behavior of the leaflets. The present study uses biaxial mechanical tests and second harmonic generation microscopy to examine the mechanical behavior of Barlow and FED tissue. Three tissue samples were harvested from a FED patient and one sample is from a Barlow patient. Then we use an appropriate constitutive model by excluding the collagen fibers under compression. Finally, we built an FE model based on the echocardiography of patients diagnosed with FED and Barlow and the characterized material model and collagen fiber orientation. The Barlow sample and the FED sample from the most affected segment showed different mechanical behavior and collagen structure compared to the other two FED samples. The FE model showed very good agreement with echocardiography with 2.02±1.8 mm and 1.05±0.79 mm point-to-mesh distance errors for Barlow and FED patients, respectively. It has also been shown that the exclusion of collagen fibers under compression provides versatility for the material model; it behaves stiff in the belly region, preventing excessive bulging, while it behaves very softly in the commissures to facilitate folding. STATEMENT OF SIGNIFICANCE: None.
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Affiliation(s)
- Mohammad Javad Sadeghinia
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway.
| | - Hans Martin Aguilera
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
| | - Gerhard A Holzapfel
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway; Institute of Biomechanics, Graz University of Technology, Austria
| | - Stig Urheim
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | - Robert Matongo Persson
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | | | - Rune Haaverstad
- Haukeland University Hospital, Department of Heart Disease, Bergen, Norway; Institute of Clinical Science, University of Bergen, Bergen, Norway
| | - Bjørn Skallerud
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
| | - Victorien Prot
- Department of Structural Engineering, Norwegian University of Science and Technology, Trondheim, Norway
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6
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Kidambi S, Moye SC, Lee J, Cowles TH, Strong EB, Wilkerson R, Paulsen MJ, Woo YJ, Ma MR. Force Profiles of Single Ventricle Atrioventricular Leaflets in Response to Annular Dilation and Leaflet Tethering. Semin Thorac Cardiovasc Surg 2022; 36:216-229. [PMID: 36455710 PMCID: PMC10225476 DOI: 10.1053/j.semtcvs.2022.09.012] [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: 09/13/2022] [Accepted: 09/15/2022] [Indexed: 11/30/2022]
Abstract
We sought to understand how leaflet forces change in response to annular dilation and leaflet tethering (LT) in single ventricle physiology. Explanted fetal bovine tricuspid valves were sutured onto image-derived annuli and ventricular mounts. Control valves (CON) were secured to a size-matched hypoplastic left heart syndrome (HLHS)-type annulus and compared to: (1) normal tricuspid valves secured to a size-matched saddle-shaped annulus, (2) HLHS-type annulus with LT, (3) HLHS-type annulus with annular dilation (dilation valves), or (4) a combined disease model with both dilation and tethering (disease valves). The specimens were tested in a systemic heart simulator at various single ventricle physiologies. Leaflet forces were measured using optical strain sensors sutured to each leaflet edge. Average force in the anterior leaflet was 43.2% lower in CON compared to normal tricuspid valves (P < 0.001). LT resulted in a 6.6% increase in average forces on the anterior leaflet (P = 0.04), 10.7% increase on the posterior leaflet (P = 0.03), and 14.1% increase on the septal leaflet (P < 0.001). In dilation valves, average septal leaflet forces increased relative to the CON by 42.2% (P = 0.01). In disease valves, average leaflet forces increased by 54.8% in the anterior leaflet (P < 0.001), 37.6% in the posterior leaflet (P = 0.03), and 79.9% in the septal leaflet (P < 0.001). The anterior leaflet experiences the highest forces in the normal tricuspid annulus under single ventricle physiology conditions. Annular dilation resulted in an increase in forces on the septal leaflet and LT resulted in an increase in forces across all 3 leaflets. Annular dilation and LT combined resulted in the largest increase in leaflet forces across all 3 leaflets.
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Affiliation(s)
- Sumanth Kidambi
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - Stephen C Moye
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - James Lee
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - Teaghan H Cowles
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - E Brandon Strong
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - Rob Wilkerson
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - Michael J Paulsen
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California
| | - Y Joseph Woo
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California; Department of Bioengineering, Stanford University, Stanford, California
| | - Michael R Ma
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, California.
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7
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Salinas SD, Farra YM, Amini Khoiy K, Houston J, Lee CH, Bellini C, Amini R. The role of elastin on the mechanical properties of the anterior leaflet in porcine tricuspid valves. PLoS One 2022; 17:e0267131. [PMID: 35560311 PMCID: PMC9106221 DOI: 10.1371/journal.pone.0267131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 04/02/2022] [Indexed: 11/19/2022] Open
Abstract
Elastin is present in the extracellular matrix (ECM) of connective tissues, and its mechanical properties are well documented. In Marfan syndrome, however, the inability to properly code for the protein fibrillin-1 prematurely leads to the degradation and loss of elastin fiber integrity in the ECM. In this study, the role of elastin in the ECM of the anterior leaflet of the tricuspid valve was investigated by examining the biomechanical behavior of porcine leaflets before and after the application of the enzyme elastase. Five loading protocols were applied to the leaflet specimens in two groups (elastase-treated and control samples). The mechanical response following elastase application yielded a significantly stiffer material in both the radial and circumferential directions. At a physiological level of stress (85 kPa), the elastase group had an average strain of 26.21% and 6.32% in the radial and circumferential directions, respectively, at baseline prior to elastase application. Following elastase treatment, the average strain was 5.28% and 0.97% in the radial and circumferential directions, respectively. No statistically significant change was found in the control group following sham treatment with phosphate-buffered saline (PBS). Two-photon microscopy images confirmed that after the removal of elastin, the collagen fibers displayed a loss of undulation. With a significant reduction in radial compliance, the ability to withstand physiological loads may be compromised. As such, an extracellular matrix that is structurally deficient in elastin may hinder normal tricuspid valve function.
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Affiliation(s)
- Samuel D. Salinas
- Department of Bioengineering, Northeastern University, Boston, MA, United States of America
- Department of Biomedical Engineering, The University of Akron, Akron, OH, United States of America
| | - Yasmeen M. Farra
- Department of Bioengineering, Northeastern University, Boston, MA, United States of America
| | - Keyvan Amini Khoiy
- Department of Biomedical Engineering, The University of Akron, Akron, OH, United States of America
| | - James Houston
- Department of Psychology, Middle Tennessee State University, Murfreesboro, TN, United States of America
| | - Chung-Hao Lee
- School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, United States of America
| | - Chiara Bellini
- Department of Biomedical Engineering, The University of Akron, Akron, OH, United States of America
| | - Rouzbeh Amini
- Department of Bioengineering, Northeastern University, Boston, MA, United States of America
- Department of Biomedical Engineering, The University of Akron, Akron, OH, United States of America
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, United States of America
- * E-mail:
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8
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Toma M, Singh-Gryzbon S, Frankini E, Wei Z(A, Yoganathan AP. Clinical Impact of Computational Heart Valve Models. MATERIALS (BASEL, SWITZERLAND) 2022; 15:3302. [PMID: 35591636 PMCID: PMC9101262 DOI: 10.3390/ma15093302] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 04/26/2022] [Accepted: 04/29/2022] [Indexed: 12/17/2022]
Abstract
This paper provides a review of engineering applications and computational methods used to analyze the dynamics of heart valve closures in healthy and diseased states. Computational methods are a cost-effective tool that can be used to evaluate the flow parameters of heart valves. Valve repair and replacement have long-term stability and biocompatibility issues, highlighting the need for a more robust method for resolving valvular disease. For example, while fluid-structure interaction analyses are still scarcely utilized to study aortic valves, computational fluid dynamics is used to assess the effect of different aortic valve morphologies on velocity profiles, flow patterns, helicity, wall shear stress, and oscillatory shear index in the thoracic aorta. It has been analyzed that computational flow dynamic analyses can be integrated with other methods to create a superior, more compatible method of understanding risk and compatibility.
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Affiliation(s)
- Milan Toma
- Department of Osteopathic Manipulative Medicine, New York Institute of Technology College of Osteopathic Medicine, Northern Boulevard, P.O. Box 8000, Old Westbury, NY 11568, USA;
| | - Shelly Singh-Gryzbon
- Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA; (S.S.-G.); (A.P.Y.)
| | - Elisabeth Frankini
- Department of Osteopathic Manipulative Medicine, New York Institute of Technology College of Osteopathic Medicine, Northern Boulevard, P.O. Box 8000, Old Westbury, NY 11568, USA;
| | - Zhenglun (Alan) Wei
- Department of Biomedical Engineering, Francis College of Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA;
| | - Ajit P. Yoganathan
- Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA; (S.S.-G.); (A.P.Y.)
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9
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Chitosan/PVA Hetero-Composite Hydrogel Containing Antimicrobials, Perfluorocarbon Nanoemulsions, and Growth Factor-Loaded Nanoparticles as a Multifunctional Dressing for Diabetic Wound Healing: Synthesis, Characterization, and In Vitro/In Vivo Evaluation. Pharmaceutics 2022; 14:pharmaceutics14030537. [PMID: 35335913 PMCID: PMC8951566 DOI: 10.3390/pharmaceutics14030537] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 02/04/2023] Open
Abstract
Diabetic foot ulcers remain one of the most difficult-to-treat complications of diabetes and may seriously threaten the life of patients since it frequently results in limb loss due to amputation, suggesting that an effective therapeutic strategy is still urgently needed. In this study, a chitosan-based heterogeneous composite hydrogel encapsulating perfluorocarbon emulsions, epidermal growth factor (EGF)-loaded chitosan nanoparticles, and polyhexamethylene biguanide (PHMB) named PEENPPCH was developed for diabetic wound healing. The PEENPPCH could sustainably release EGF and PHMB in an ion-rich environment to exert antibacterial effects and promote cell growth for wound repair. In addition, the PEENPPCH can provide anti-inflammatory effects functioned by its main constituent of chitosan. Moreover, the PEENPPCH can proactively offer oxygen delivery through the incorporation of perfluorocarbon and, therefore, is able to alleviate hypoxia conditions on diabetic wounds. These functionalities enabled a markedly enhanced wound healing efficacy on diabetic rats treated with the PEENPPCHs, including thorough re-epithelization, a reduced inflammatory response, faster collagen deposition, and advanced collagen maturation resulting in a 95% of wound closure degree after 15 days that was 12.6% (p < 0.05) higher than the value of the group treated with the commercial dressing HeraDerm. Given the aforementioned advantages, together with the known merits of hydrogels, the developed PEENPPCH is anticipated to be a feasible tool for clinical diabetic wound treatment.
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10
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Novel silver and nanoparticle-encapsulated growth factor co-loaded chitosan composite hydrogel with sustained antimicrobility and promoted biological properties for diabetic wound healing. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2021; 118:111385. [DOI: 10.1016/j.msec.2020.111385] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 07/09/2020] [Accepted: 08/06/2020] [Indexed: 12/16/2022]
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11
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Mathur M, Meador WD, Jazwiec T, Malinowski M, Timek TA, Rausch MK. Tricuspid Valve Annuloplasty Alters Leaflet Mechanics. Ann Biomed Eng 2020; 48:2911-2923. [PMID: 32761558 PMCID: PMC8000450 DOI: 10.1007/s10439-020-02586-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 07/27/2020] [Indexed: 10/23/2022]
Abstract
Tricuspid valve regurgitation is associated with significant morbidity and mortality. Its most common treatment option, tricuspid valve annuloplasty, is not optimally effective in the long-term. Toward identifying the causes for annuloplasty's ineffectiveness, we have previously investigated the technique's impact on the tricuspid annulus and the right ventricular epicardium. In our current work, we are extending our analysis to the anterior tricuspid valve leaflet. To this end, we adopted our previous strategy of performing DeVega suture annuloplasty as an experimental methodology that allows us to externally control the degree of cinching during annuloplasty. Thus, in ten sheep we successively cinched the annulus and quantified changes to leaflet motion, dynamics, and strain in the beating heart by combining sonomicrometry with our well-established mechanical framework. We found that successive cinching of the valve enforced earlier coaptation and thus reduced leaflet range of motion. Additionally, leaflet angular velocity during opening and closing decreased. Finally, we found that leaflet strains were also reduced. Specifically, radial and areal strains decreased as a function of annular cinching. Our findings are critical as they suggest that suture annuloplasty alters the mechanics of the tricuspid valve leaflets which may disrupt their resident cells' mechanobiological equilibrium. Long-term, such disruption may stimulate tissue maladaptation which could contribute to annuloplasty's sub-optimal effectiveness. Additionally, our data suggest that the extent to which annuloplasty alters leaflet mechanics can be controlled via degree of cinching. Hence, our data may provide direct surgical guidelines.
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Affiliation(s)
- Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, TX, 78712, USA
| | - William D Meador
- Department of Biomedical Engineering, University of Texas at Austin, 107 W Dean Keeton Street, Austin, TX, 78712, USA
| | - Tomasz Jazwiec
- Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Silesian Centre for Heart Diseases, Medical University of Silesia in Katowice, Zabrze, Poland
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Marcin Malinowski
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
- Department of Cardiac Surgery, School of Medicine in Katowice, Medical University of Silesia, Katowice, Poland
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Manuel K Rausch
- Departments of Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, University of Texas at Austin, 2617 Wichita Street, Austin, TX, 78712, USA.
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12
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A Pilot Study on Linking Tissue Mechanics with Load-Dependent Collagen Microstructures in Porcine Tricuspid Valve Leaflets. Bioengineering (Basel) 2020; 7:bioengineering7020060. [PMID: 32570939 PMCID: PMC7356733 DOI: 10.3390/bioengineering7020060] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/05/2020] [Accepted: 06/15/2020] [Indexed: 11/25/2022] Open
Abstract
The tricuspid valve (TV) is composed of three leaflets that coapt during systole to prevent deoxygenated blood from re-entering the right atrium. The connection between the TV leaflets’ microstructure and the tissue-level mechanical responses has yet to be fully understood in the TV biomechanics society. This pilot study sought to examine the load-dependent collagen fiber architecture of the three TV leaflets, by employing a multiscale, combined experimental approach that utilizes tissue-level biaxial mechanical characterizations, micro-level collagen fiber quantification, and histological analysis. Our results showed that the three TV leaflets displayed greater extensibility in the tissues’ radial direction than in the circumferential direction, consistently under different applied biaxial tensions. Additionally, collagen fibers reoriented towards the direction of the larger applied load, with the largest changes in the alignment of the collagen fibers under radially-dominant loading. Moreover, collagen fibers in the belly region of the TV leaflets were found to experience greater reorientations compared to the tissue region closer to the TV annulus. Furthermore, histological examinations of the TV leaflets displayed significant regional variation in constituent mass fraction, highlighting the heterogeneous collagen microstructure. The combined experimental approach presented in this work enables the connection of tissue mechanics, collagen fiber microstructure, and morphology for the TV leaflets. This experimental methodology also provides a new research platform for future developments, such as multiscale models for the TVs, and the design of bioprosthetic heart valves that could better mimic the mechanical, microstructural, and morphological characteristics of the native tricuspid valve leaflets.
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13
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Biomechanical Cues Direct Valvulogenesis. J Cardiovasc Dev Dis 2020; 7:jcdd7020018. [PMID: 32438610 PMCID: PMC7345189 DOI: 10.3390/jcdd7020018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/27/2020] [Accepted: 05/12/2020] [Indexed: 12/30/2022] Open
Abstract
The vertebrate embryonic heart initially forms with two chambers, a ventricle and an atrium, separated by the atrioventricular junction. Localized genetic and biomechanical information guides the development of valves, which function to ensure unidirectional blood flow. If the valve development process goes awry, pathology associated with congenital valve defects can ensue. Congenital valve defects (CVD) are estimated to affect 1–2% of the population and can often require a lifetime of treatment. Despite significant clinical interest, molecular genetic mechanisms that direct valve development remain incompletely elucidated. Cells in the developing valve must contend with a dynamic hemodynamic environment. A growing body of research supports the idea that cells in the valve are highly sensitive to biomechanical forces, which cue changes in gene expression required for normal development or for maintenance of the adult valve. This review will focus on mechanotransductive pathways involved in valve development across model species. We highlight current knowledge regarding how cells sense physical forces associated with blood flow and pressure in the forming heart, and summarize how these changes are transduced into genetic and developmental responses. Lastly, we provide perspectives on how altered biomechanical cues may lead to CVD pathogenesis.
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14
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Mathur M, Meador WD, Jazwiec T, Malinowski M, Timek TA, Rausch MK. The Effect of Downsizing on the Normal Tricuspid Annulus. Ann Biomed Eng 2020; 48:655-668. [PMID: 31659604 PMCID: PMC8353055 DOI: 10.1007/s10439-019-02387-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/11/2019] [Indexed: 12/17/2022]
Abstract
Tricuspid annuloplasty is a surgical procedure that cinches the valve's annulus in order to reduce regurgitant blood flow. One of its critical parameters is the degree of downsizing. To provide insight into the effect of downsizing, we studied the annulus of healthy sheep during suture annuloplasty. To this end, we implanted fiduciary markers along the annulus of sheep and subsequently performed a DeVega suture annuloplasty. We performed five downsizing steps in each animal while recording hemodynamic and sonomicrometry data in beating hearts. Subsequently, we used splines to approximate the annulus at baseline and at each downsizing step. Based on these approximations we computed clinical metrics of annular shape and dynamics, and the continuous field metrics height, strain, and curvature. With these data, we demonstrated that annular area reduction during downsizing was primarily driven by compression of the anterior annulus. Similarly, reduction in annular dynamics was driven by reduced contractility in the anterior annulus. Finally, changes in global height and eccentricity of the annulus could be explained by focal changes in the continuous height profile and changes in annular curvature. Our findings are important as they provide insight into a regularly performed surgical procedure and may inform the design of transcatheter devices that mimic suture annuloplasty.
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Affiliation(s)
- Mrudang Mathur
- Department of Mechanical Engineering, University of Texas at Austin, 204 E Dean Keeton Street, Austin, TX, 78712, USA
| | - William D Meador
- Department of Biomedical Engineering, University of Texas at Austin, 107 W Dean Keeton Street, Austin, TX, 78712, USA
| | - Tomasz Jazwiec
- Silesian Centre for Heart Diseases, Department of Cardiac, Vascular and Endovascular Surgery and Transplantology, Medical University of Silesia in Katowice, Zabrze, Poland
| | - Marcin Malinowski
- Department of Cardiac Surgery, School of Medicine in Katowice, Medical University of Silesia, Katowice, Poland
| | - Tomasz A Timek
- Division of Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI, 49503, USA
| | - Manuel K Rausch
- Departments of Aerospace Engineering & Engineering Mechanics, Biomedical Engineering, University of Texas at Austin, 2617, Wichita Street, Austin, TX, 78712, USA.
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15
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Meador WD, Mathur M, Sugerman GP, Jazwiec T, Malinowski M, Bersi MR, Timek TA, Rausch MK. A detailed mechanical and microstructural analysis of ovine tricuspid valve leaflets. Acta Biomater 2020; 102:100-113. [PMID: 31760220 PMCID: PMC7325866 DOI: 10.1016/j.actbio.2019.11.039] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/14/2019] [Accepted: 11/19/2019] [Indexed: 12/26/2022]
Abstract
The tricuspid valve ensures unidirectional blood flow from the right atrium to the right ventricle. The three tricuspid leaflets operate within a dynamic stress environment of shear, bending, tensile, and compressive forces, which is cyclically repeated nearly three billion times in a lifetime. Ostensibly, the microstructural and mechanical properties of the tricuspid leaflets have mechanobiologically evolved to optimally support their function under those forces. Yet, how the tricuspid leaflet microstructure determines its mechanical properties and whether this relationship differs between the three leaflets is unknown. Here we perform a microstructural and mechanical analysis in matched ovine tricuspid leaflet samples. We found that the microstructure and mechanical properties vary among the three tricuspid leaflets in sheep. Specifically, we found that tricuspid leaflet composition, collagen orientation, and valve cell nuclear morphology are spatially heterogeneous and vary across leaflet type. Furthermore, under biaxial tension, the leaflets' mechanical behaviors exhibited unequal degrees of mechanical anisotropy. Most importantly, we found that the septal leaflet was stiffer in the radial direction and not the circumferential direction as with the other two leaflets. The differences we observed in leaflet microstructure coincide with the varying biaxial mechanics among leaflets. Our results demonstrate the structure-function relationship for each leaflet in the tricuspid valve. We anticipate our results to be vital toward developing more accurate, leaflet-specific tricuspid valve computational models. Furthermore, our results may be clinically important, informing differential surgical treatments of the tricuspid valve leaflets. Finally, the identified structure-function relationships may provide insight into the homeostatic and remodeling potential of valvular cells in altered mechanical environments, such as in diseased or repaired tricuspid valves. STATEMENT OF SIGNIFICANCE: Our work is significant as we investigated the structure-function relationship of ovine tricuspid valve leaflets. This is important as tricuspid valves fail frequently and our current approach to repairing them is suboptimal. Specifically, we related the distribution of structural and cellular elements, such as collagen, glycosaminoglycans, and cell nuclei, to each leaflet's mechanical properties. We found that leaflets have different structures and that their mechanics differ. This may, in the future, inform leaflet-specific treatment strategies and help optimize surgical outcomes.
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Affiliation(s)
- William D Meador
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78705, USA
| | - Mrudang Mathur
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78705, USA
| | - Gabriella P Sugerman
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78705, USA
| | - Tomasz Jazwiec
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI 49503, USA; Department of Cardiac, Vascular, and Endovascular Surgery and Transplantology, Medical University of Silesia School of Medicine in Katowice, Silesian Centre for Heart Diseases, Zabrze, Poland
| | - Marcin Malinowski
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI 49503, USA; Department of Cardiac Surgery, Medical University of Silesia School of Medicine in Katowice, Katowice, Poland
| | - Matthew R Bersi
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37235, USA
| | - Tomasz A Timek
- Cardiothoracic Surgery, Spectrum Health, Grand Rapids, MI 49503, USA
| | - Manuel K Rausch
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78705, USA; Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78705, USA; Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, TX 78705, USA.
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16
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Salinas SD, Clark MM, Amini R. The effects of -80 °C short-term storage on the mechanical response of tricuspid valve leaflets. J Biomech 2020; 98:109462. [PMID: 31718820 DOI: 10.1016/j.jbiomech.2019.109462] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/23/2019] [Accepted: 10/24/2019] [Indexed: 11/19/2022]
Abstract
Mechanical testing of soft tissues would ideally rely on using fresh specimens. In the event that fresh tissues are not readily available, alternative measures, such as storing fresh specimens at -80 °C, could be considered. Previous studies have shown that changes in the mechanical properties of the tissues due to freezing could be tissue-dependent. Prior to our study, however, such information was not available for the tricuspid valve leaflets. As such, for the first time, we examined whether fresh porcine specimens tested in a biaxial tensile machine would offer comparable results after being frozen at -80 °C. The stress-strain response of the tricuspid valve leaflets displayed no major deviation of the post-frozen leaflets as compared to fresh leaflets. We further compared the radial and circumferential strains as an indicator of deformation at similar stress states in fresh and thawed tissues, and we did not find any significant differences. Ice formation within the extra cellular matrix may modify the collagen fiber configuration, resulting in a slight change in the mechanical response. Nevertheless, our results indicated such a small deviation was negligible, thus enabling the possibility of using frozen porcine tricuspid valve specimens for future research.
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Affiliation(s)
- Samuel D Salinas
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio, United States.
| | - Margaret M Clark
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio, United States.
| | - Rouzbeh Amini
- Department of Biomedical Engineering, The University of Akron, Akron, Ohio, United States.
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17
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Khoiy KA, Pant AD, Amini R. Quantification of Material Constants for a Phenomenological Constitutive Model of Porcine Tricuspid Valve Leaflets for Simulation Applications. J Biomech Eng 2019; 140:2681002. [PMID: 29801174 DOI: 10.1115/1.4040126] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Indexed: 11/08/2022]
Abstract
The tricuspid valve is a one-way valve on the pulmonary side of the heart, which prevents backflow of blood during ventricular contractions. Development of computational models of the tricuspid valve is important both in understanding the normal valvular function and in the development/improvement of surgical procedures and medical devices. A key step in the development of such models is quantification of the mechanical properties of the tricuspid valve leaflets. In this study, after examining previously measured five-loading-protocol biaxial stress-strain response of porcine tricuspid valves, a phenomenological constitutive framework was chosen to represent this response. The material constants were quantified for all three leaflets, which were shown to be highly anisotropic with average anisotropy indices of less than 0.5 (an anisotropy index value of 1 indicates a perfectly isotropic response, whereas a smaller value of the anisotropy index indicates an anisotropic response). To obtain mean values of material constants, stress-strain responses of the leaflet samples were averaged and then fitted to the constitutive model (average R2 over 0.9). Since the sample thicknesses were not hugely different, averaging the data using the same tension levels and stress levels produced similar average material constants for each leaflet.
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Affiliation(s)
- Keyvan Amini Khoiy
- Department of Biomedical Engineering, The University of Akron Olson Research Center, Room 322/3 260 South Forge Street, Akron, OH 44325 e-mail:
| | - Anup D Pant
- Department of Biomedical Engineering, The University of Akron Olson Research Center, Room 322/3 260 South Forge Street, Akron, OH 44325 e-mail:
| | - Rouzbeh Amini
- Mem. ASME Department of Biomedical Engineering, The University of Akron Olson Research Center, , Akron, OH 44325 e-mail:
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18
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Duginski GA, Ross CJ, Laurence DW, Johns CH, Lee CH. An investigation of the effect of freezing storage on the biaxial mechanical properties of excised porcine tricuspid valve anterior leaflets. J Mech Behav Biomed Mater 2019; 101:103438. [PMID: 31542570 PMCID: PMC8008703 DOI: 10.1016/j.jmbbm.2019.103438] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/27/2019] [Accepted: 09/15/2019] [Indexed: 01/03/2023]
Abstract
The atrioventricular heart valve (AHV) leaflets are critical to the facilitation of proper unidirectional blood flow through the heart. Previously, studies have been conducted to understand the tissue mechanics of healthy AHV leaflets to inform the development of valve-specific computational models and replacement materials for use in diagnosing and treating valvular heart disease. Generally, these studies involved biaxial mechanical testing of the AHV leaflet tissue specimens to extract relevant mechanical properties. Most of those studies considered freezing-based storage systems based on previous findings for other connective tissues such as aortic tissue or skin. However, there remains no study that specifically examines the effects of freezing storage on the characterized mechanical properties of the AHV leaflets. In this study, we aimed to address this gap in knowledge by performing biaxial mechanical characterizations of the tricuspid valve anterior leaflet (TVAL) tissue both before and after a 48-h freezing period. Primary findings of this study include: (i) a statistically insignificant change in the tissue extensibilities, with the frozen tissues being slightly stiffer and more anisotropic than the fresh tissues; and (ii) minimal variations in the stress relaxation behaviors between the fresh and frozen tissues, with the frozen tissues demonstrating slightly lessened relaxation. The findings from this study suggested that freezing-based storage does not significantly impact the observed mechanical properties of one of the five AHV leaflets-the TVAL. The results from this study are useful for reaffirming the experimental methodologies in the previous studies, as well as informing the tissue preservation methods of future investigations of AHV leaflet mechanics.
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Affiliation(s)
- Grace A Duginski
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, 73019, USA.
| | - Colton J Ross
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, 73019, USA.
| | - Devin W Laurence
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, 73019, USA.
| | - Cortland H Johns
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, 73019, USA.
| | - Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory (BBDL), School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK, 73019, USA; Institute for Biomedical Engineering, Science and Technology, School of Aerospace and Mechanical Engineering (IBEST), The University of Oklahoma, Norman, OK, 73019, USA.
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19
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Vekilov DP, Singh M, Aglyamov SR, Larin KV, Grande-Allen KJ. Mapping the spatial variation of mitral valve elastic properties using air-pulse optical coherence elastography. J Biomech 2019; 93:52-59. [PMID: 31300156 PMCID: PMC10575695 DOI: 10.1016/j.jbiomech.2019.06.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/18/2019] [Accepted: 06/14/2019] [Indexed: 10/26/2022]
Abstract
The mitral valve is a highly heterogeneous tissue composed of two leaflets, anterior and posterior, whose unique composition and regional differences in material properties are essential to overall valve function. While mitral valve mechanics have been studied for many decades, traditional testing methods limit the spatial resolution of measurements and can be destructive. Optical coherence elastography (OCE) is an emerging method for measuring viscoelastic properties of tissues in a noninvasive, nondestructive manner. In this study, we employed air-pulse OCE to measure the spatial variation in mitral valve elastic properties with micro-scale resolution at 1 mm increments along the radial length of the leaflets. We analyzed differences between the leaflets, as well as between regions of the valve. We found that the anterior leaflet has a higher elastic wave velocity, which is reported as a surrogate for stiffness, than the posterior leaflet, most notably at the annular edge of the sample. In addition, we found a spatial elastic gradient in the anterior leaflet, where the annular edge was found to have a greater elastic wave velocity than the free edge. This gradient was less pronounced in the posterior leaflet. These patterns were confirmed using established uniaxial tensile testing methods. Overall, the anterior leaflet was stiffer and had greater heterogeneity in its mechanical properties than the posterior leaflet. This study measures differences between the two mitral leaflets with greater resolution than previously feasible and demonstrates a method that may be suitable for assessing valve mechanics following repair or during the engineering of synthetic valve replacements.
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Affiliation(s)
| | - Manmohan Singh
- University of Houston, Department of Biomedical Engineering, Houston, TX, United States
| | - Salavat R Aglyamov
- University of Houston, Department of Mechanical Engineering, Houston, TX, United States; University of Texas at Austin, Department of Biomedical Engineering, Austin, TX, United States
| | - Kirill V Larin
- University of Houston, Department of Biomedical Engineering, Houston, TX, United States
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20
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Salinas SD, Clark MM, Amini R. Mechanical Response Changes in Porcine Tricuspid Valve Anterior Leaflet Under Osmotic-Induced Swelling. Bioengineering (Basel) 2019; 6:E70. [PMID: 31443151 PMCID: PMC6784000 DOI: 10.3390/bioengineering6030070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/27/2019] [Accepted: 08/13/2019] [Indexed: 01/22/2023] Open
Abstract
Since many soft tissues function in an isotonic in-vivo environment, it is expected that physiological osmolarity will be maintained when conducting experiments on these tissues ex-vivo. In this study, we aimed to examine how not adhering to such a practice may alter the mechanical response of the tricuspid valve (TV) anterior leaflet. Tissue specimens were immersed in deionized (DI) water prior to quantification of the stress-strain responses using an in-plane biaxial mechanical testing device. Following a two-hour immersion in DI water, the tissue thickness increased an average of 107.3% in the DI water group compared to only 6.8% in the control group, in which the tissue samples were submerged in an isotonic phosphate buffered saline solution for the same period of time. Tissue strains evaluated at 85 kPa revealed a significant reduction in the radial direction, from 34.8% to 20%, following immersion in DI water. However, no significant change was observed in the control group. Our study demonstrated the impact of a hypo-osmotic environment on the mechanical response of TV anterior leaflet. The imbalance in ions leads to water absorption in the valvular tissue that can alter its mechanical response. As such, in ex-vivo experiments for which the native mechanical response of the valves is important, using an isotonic buffer solution is essential.
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Affiliation(s)
- Samuel D Salinas
- Department of Biomedical Engineering, The University of Akron, Akron, OH 44325, USA
| | - Margaret M Clark
- Department of Biomedical Engineering, The University of Akron, Akron, OH 44325, USA
| | - Rouzbeh Amini
- Department of Biomedical Engineering, The University of Akron, Akron, OH 44325, USA.
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21
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Thomas VS, Lai V, Amini R. A computational multi-scale approach to investigate mechanically-induced changes in tricuspid valve anterior leaflet microstructure. Acta Biomater 2019; 94:524-535. [PMID: 31229629 DOI: 10.1016/j.actbio.2019.05.074] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 05/10/2019] [Accepted: 05/16/2019] [Indexed: 12/12/2022]
Abstract
The tricuspid valve is an atrioventricular valve that prevents blood backflow from the right ventricle into the right atrium during ventricular contractions. It is important to study mechanically induced microstructural alterations in the tricuspid valve leaflets, as this aids both in understanding valvular diseases and in the development of new engineered tissue replacements. The structure and composition of the extracellular matrix (ECM) fiber networks are closely tied to an overall biomechanical function of the tricuspid valve. In this study, we conducted experiments and implemented a multiscale modeling approach to predict ECM microstructural changes to tissue-level mechanical responses in a controlled loading environment. In particular, we characterized a sample of a porcine anterior leaflet at a macroscale using a biaxial mechanical testing method. We then generated a three-dimensional finite element model, to which computational representations of corresponding fiber networks were incorporated based on properties of the microstructural architecture obtained from small angle light scattering. Using five different biaxial boundary conditions, we performed iterative simulations to obtain model parameters with an overall R2 value of 0.93. We observed that mechanical loading could markedly alter the underlying ECM architecture. For example, a relatively isotropic fiber network (with an anisotropy index value α of 28%) became noticeably more anisotropic (with an α of 40%) when it underwent mechanical loading. We also observed that the mechanical strain was distributed in a different manner at the ECM/fiber level as compared to the tissue level. The approach presented in this study has the potential to be implemented in pathophysiologically altered biomechanical and structural conditions and to bring insights into the mechanobiology of the tricuspid valve. STATEMENT OF SIGNIFICANCE: Quantifying abnormal cellar/ECM-level deformation of tricuspid valve leaflets subjected to a modified loading environment is of great importance, as it is believed to be linked to valvular remodeling responses. For example, developing surgical procedures or engineered tissue replacements that maintain/mimic ECM-level mechanical homeostasis could lead to more durable outcomes. To quantify leaflet deformation, we built a multiscale framework encompassing the contributions of disorganized ECM components and organized fibers, which can predict the behavior of the tricuspid valve leaflets under physiological loading conditions both at the tissue level and at the ECM level. In addition to future in-depth studies of tricuspid valve pathologies, our model can be used to characterize tissues in other valves of the heart.
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22
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Patil PS, Fathollahipour S, Inmann A, Pant A, Amini R, Shriver LP, Leipzig ND. Fluorinated Methacrylamide Chitosan Hydrogel Dressings Improve Regenerated Wound Tissue Quality in Diabetic Wound Healing. Adv Wound Care (New Rochelle) 2019; 8:374-385. [PMID: 31346492 DOI: 10.1089/wound.2018.0887] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 02/20/2019] [Indexed: 12/19/2022] Open
Abstract
Objective: Oxygen therapy has shown promising results for treating diabetic wounds. However, clinically used oxygen therapies are cumbersome and expensive. Thus, there is a need to develop a localized oxygenating treatment that is easy to use and inexpensive. Approach: In this study, we tested a previously developed hydrogel sheet wound dressing based on fluorinated methacrylamide chitosan (MACF) for enhanced oxygenation and compared it with a commercial sheet hydrogel dressing, AquaDerm™, and no treatment controls in a splinted transgenic diabetic mouse wound model. Results: AquaDerm exhibited poor wound closure response compared with the MACF oxygenating hydrogel sheet dressing (MACF+O2) and no treatment. Histological analysis revealed enhanced collagen synthesis and neovascularization upon MACF+O2 treatment as indicated by higher collagen content and number of blood vessels/capillaries compared with AquaDerm and no treatment. MACF+O2 also improved wound collagen fiber alignment, thus demonstrating improved skin tissue maturation. Nuclear magnetic resonance spectroscopy-based biodistribution analysis revealed that the degradation products of the MACF-based dressing did not accumulate in lung, liver, and kidney tissues of the treated animals after 14 days of treatment. Innovation: This study presents the first application of a unique oxygenating biomaterial (MACF) made into a moist hydrogel wound dressing for treating diabetic wounds. Conclusion: The results of this study confirm the benefits of this novel biomaterial approach for improving regenerated tissue structure in diabetic wound healing.
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Affiliation(s)
- Pritam S. Patil
- Department of Chemical and Biomolecular Engineering, University of Akron, Akron, Ohio
| | | | | | - Anup Pant
- Department of Biomedical Engineering, University of Akron, Akron, Ohio
| | - Rouzbeh Amini
- Department of Biomedical Engineering, University of Akron, Akron, Ohio
| | | | - Nic D. Leipzig
- Department of Chemical and Biomolecular Engineering, University of Akron, Akron, Ohio
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23
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Lee CH, Laurence DW, Ross CJ, Kramer KE, Babu AR, Johnson EL, Hsu MC, Aggarwal A, Mir A, Burkhart HM, Towner RA, Baumwart R, Wu Y. Mechanics of the Tricuspid Valve-From Clinical Diagnosis/Treatment, In-Vivo and In-Vitro Investigations, to Patient-Specific Biomechanical Modeling. Bioengineering (Basel) 2019; 6:E47. [PMID: 31121881 PMCID: PMC6630695 DOI: 10.3390/bioengineering6020047] [Citation(s) in RCA: 25] [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: 04/28/2019] [Revised: 05/16/2019] [Accepted: 05/17/2019] [Indexed: 12/29/2022] Open
Abstract
Proper tricuspid valve (TV) function is essential to unidirectional blood flow through the right side of the heart. Alterations to the tricuspid valvular components, such as the TV annulus, may lead to functional tricuspid regurgitation (FTR), where the valve is unable to prevent undesired backflow of blood from the right ventricle into the right atrium during systole. Various treatment options are currently available for FTR; however, research for the tricuspid heart valve, functional tricuspid regurgitation, and the relevant treatment methodologies are limited due to the pervasive expectation among cardiac surgeons and cardiologists that FTR will naturally regress after repair of left-sided heart valve lesions. Recent studies have focused on (i) understanding the function of the TV and the initiation or progression of FTR using both in-vivo and in-vitro methods, (ii) quantifying the biomechanical properties of the tricuspid valve apparatus as well as its surrounding heart tissue, and (iii) performing computational modeling of the TV to provide new insight into its biomechanical and physiological function. This review paper focuses on these advances and summarizes recent research relevant to the TV within the scope of FTR. Moreover, this review also provides future perspectives and extensions critical to enhancing the current understanding of the functioning and remodeling tricuspid valve in both the healthy and pathophysiological states.
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Affiliation(s)
- Chung-Hao Lee
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
- Institute for Biomedical Engineering, Science and Technology (IBEST), The University of Oklahoma, Norman, OK 73019, USA.
| | - Devin W Laurence
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
| | - Colton J Ross
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
| | - Katherine E Kramer
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
| | - Anju R Babu
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
- Department of Biotechnology and Medical Engineering, National Institute of Technology Rourkela, Rourkela, Odisha 769008, India.
| | - Emily L Johnson
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
| | - Ming-Chen Hsu
- Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
| | - Ankush Aggarwal
- Glasgow Computational Engineering Centre, School of Engineering, University of Glasgow, Scotland G12 8LT, UK.
| | - Arshid Mir
- Division of Pediatric Cardiology, Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
| | - Harold M Burkhart
- Division of Cardiothoracic Surgery, Department of Surgery, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
| | - Rheal A Towner
- Advance Magnetic Resonance Center, MS 60, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA.
| | - Ryan Baumwart
- Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
| | - Yi Wu
- Biomechanics and Biomaterials Design Laboratory, School of Aerospace and Mechanical Engineering, The University of Oklahoma, Norman, OK 73019, USA.
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Pierce EL, Sadri V, Ncho B, Kohli K, Shah S, Yoganathan AP. Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve Design, Part I: Paravalvular Leakage. Ann Biomed Eng 2019; 47:381-391. [PMID: 30341735 PMCID: PMC6344268 DOI: 10.1007/s10439-018-02154-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 10/10/2018] [Indexed: 11/26/2022]
Abstract
While transcatheter mitral valve (TMV) replacement technology has great clinical potential for surgically inoperable patients suffering from mitral regurgitation, no TMV has yet achieved regulatory approval. The diversity of devices currently under development reflects a lack of consensus regarding optimal design approaches. In Part I of this two-part study, a test system was developed for the quantification of paravalvular leakage (PVL) following deployment of a TMV or TMV-like device in pressurized, explanted porcine hearts (N = 7). Using this system, PVL rate was investigated as a function of steady trans-mitral pressure (ΔP), TMV shape, and TMV-annular oversizing, using a series of "mock TMV plug" devices. Across all devices, PVL was found to approximately trend with the square of ΔP. PVL rates were approximately 0-15 mL/s under hypotensive pressure, 10-40 mL/s under normotension, and 30-85 mL/s under severe hypertension. D-shaped devices significantly reduced PVL vs. circular devices; however, this effect was diminished upon oversizing to the annulus by 6 mm inter-trigonal distance. In conclusion, this steady pressure, in vitro test system was effective to compare PVL performance across TMV-like designs. PVL exhibited complex dynamics in terms of its response to transvalvular pressure and TMV profile.
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Affiliation(s)
- Eric L Pierce
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA
| | - Vahid Sadri
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA
| | - Beatrice Ncho
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA
| | - Keshav Kohli
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA
| | - Siddhi Shah
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA
| | - Ajit P Yoganathan
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA.
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Cheng ZY, Ge ZW, Wang BC, Hu JL, Li JC, Zhao ZN, Qiao G, Quan XQ, Zhang GB. Clinical efficacy of two different tricuspid annuloplasty techniques in left cardiac valve surgery. ASIAN PAC J TROP MED 2018. [DOI: 10.4103/1995-7645.225027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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