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Szafron JM, Heng EE, Boyd J, Humphrey JD, Marsden AL. Hemodynamics and Wall Mechanics of Vascular Graft Failure. Arterioscler Thromb Vasc Biol 2024; 44:1065-1085. [PMID: 38572650 PMCID: PMC11043008 DOI: 10.1161/atvbaha.123.318239] [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: 09/04/2023] [Accepted: 03/12/2024] [Indexed: 04/05/2024]
Abstract
Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.
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Affiliation(s)
- Jason M Szafron
- Departments of Pediatrics (J.M.S., A.L.M.), Stanford University, CA
| | - Elbert E Heng
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jack Boyd
- Cardiothoracic Surgery (E.E.H., J.B.), Stanford University, CA
| | - Jay D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT (J.D.H.)
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2
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Gou K, Hu JJ, Baek S. Mechanical characterization of human umbilical arteries by thick-walled models: Enhanced vascular compliance by removing an abluminal lining. J Mech Behav Biomed Mater 2023; 142:105811. [PMID: 37028123 DOI: 10.1016/j.jmbbm.2023.105811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 03/19/2023] [Accepted: 03/25/2023] [Indexed: 04/03/2023]
Abstract
The decellularized human umbilical artery (HUA) is considered as a promising option for small-diameter, tissue-engineered vascular grafts (TEVGs). Our previous study showed that the HUA bears a thin, watertight lining on its outermost abluminal surface. Removal of this abluminal lining layer improves efficacy of the perfusion-assisted decellularization of the HUA and increases its compliance. As stress across the wall is believed to affect growth and remodeling of the TEVG, it is imperative to mechanically characterize the HUA using thick-walled models. Combining inflation experiments and computational methods, we investigate the mechanical properties of the HUA before and after the abluminal lining removal to examine the HUA's wall mechanics. The inflation tests of five HUAs were performed to obtain the mechanical and geometrical response of the vessel wall before and after the lining layer removal. Using nonlinear hyperelastic models, the same responses are obtained computationally using the thick-walled models. The experimental data are incorporated into the computational models to estimate the mechanical and orientation parameters of the fibers and isotropic matrix of different layers in the HUAs. The parameter fitting of both thick-walled models (before and after the abluminal lining removal) results in most of the R-squared values for measuring the goodness of fitting to be over 0.90 for all samples. The compliance of the HUA increases from a mean value of 2.60% per 100 mmHg before the removal of the lining to a mean value of 4.21% per 100 mmHg after the removal. The results reveal that, although the abluminal lining is thin, it is stiff and capable of supporting majority of the high luminal pressure, and that the inner layer is far less stressed than the abluminal lining. Computational simulations also show that removal of the abluminal lining increases the circumferential wall stress by up to 280 kPa under the in vivo luminal pressure. The integrated computational and experimental approaches provide more accurate estimates of the material behaviors of HUAs employed in grafts and, in turn, the study enhances our understanding of interactions between the graft and the native vessel on vascular growth and remodeling.
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Affiliation(s)
- Kun Gou
- Department of Mathematical, Physical, and Engineering Sciences, Texas A&M University-San Antonio, San Antonio, TX, USA.
| | - Jin-Jia Hu
- Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
| | - Seungik Baek
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, USA.
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3
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Loerakker S, Humphrey JD. Computer Model-Driven Design in Cardiovascular Regenerative Medicine. Ann Biomed Eng 2023; 51:45-57. [PMID: 35974236 PMCID: PMC9832109 DOI: 10.1007/s10439-022-03037-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 07/20/2022] [Indexed: 01/28/2023]
Abstract
Continuing advances in genomics, molecular and cellular mechanobiology and immunobiology, including transcriptomics and proteomics, and biomechanics increasingly reveal the complexity underlying native tissue and organ structure and function. Identifying methods to repair, regenerate, or replace vital tissues and organs remains one of the greatest challenges of modern biomedical engineering, one that deserves our very best effort. Notwithstanding the continuing need for improving standard methods of investigation, including cell, organoid, and tissue culture, biomaterials development and fabrication, animal models, and clinical research, it is increasingly evident that modern computational methods should play increasingly greater roles in advancing the basic science, bioengineering, and clinical application of regenerative medicine. This brief review focuses on the development and application of computational models of tissue and organ mechanobiology and mechanics for purposes of designing tissue engineered constructs and understanding their development in vitro and in situ. Although the basic approaches are general, for illustrative purposes we describe two recent examples from cardiovascular medicine-tissue engineered heart valves (TEHVs) and tissue engineered vascular grafts (TEVGs)-to highlight current methods of approach as well as continuing needs.
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Affiliation(s)
- Sandra Loerakker
- Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Jay D Humphrey
- Department of Biomedical Engineering and Vascular Biology & Therapeutics Program, Yale University and Yale School of Medicine, New Haven, CT, USA.
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4
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Latorre M, Szafron JM, Ramachandra AB, Humphrey JD. In vivo development of tissue engineered vascular grafts: a fluid-solid-growth model. Biomech Model Mechanobiol 2022; 21:827-848. [PMID: 35179675 PMCID: PMC9133046 DOI: 10.1007/s10237-022-01562-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 01/24/2022] [Indexed: 11/02/2022]
Abstract
Methods of tissue engineering continue to advance, and multiple clinical trials are underway evaluating tissue engineered vascular grafts (TEVGs). Whereas initial concerns focused on suture retention and burst pressure, there is now a pressing need to design grafts to have optimal performance, including an ability to grow and remodel in response to changing hemodynamic loads. Toward this end, there is similarly a need for computational methods that can describe and predict the evolution of TEVG geometry, composition, and material properties while accounting for changes in hemodynamics. Although the ultimate goal is a fluid-solid-growth (FSG) model incorporating fully 3D growth and remodeling and 3D hemodynamics, lower fidelity models having high computational efficiency promise to play important roles, especially in the design of candidate grafts. We introduce here an efficient FSG model of in vivo development of a TEVG based on two simplifying concepts: mechanobiologically equilibrated growth and remodeling of the graft and an embedded control volume analysis of the hemodynamics. Illustrative simulations for a model Fontan conduit reveal the utility of this approach, which promises to be particularly useful in initial design considerations involving formal methods of optimization which otherwise add considerably to the computational expense.
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Affiliation(s)
- Marcos Latorre
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520, USA.
- Center for Research and Innovation in Bioengineering, Universitat Politècnica de València, València, 46022, Spain.
| | - Jason M Szafron
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520, USA
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, CA, 94305, USA
| | - Abhay B Ramachandra
- Department of Biomedical Engineering, Yale University, New Haven, CT, 06520, USA
| | - Jay D Humphrey
- Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT, 06520, USA
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5
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Furdella KJ, Higuchi S, Kim K, Doetschman T, Wagner WR, Vande Geest JP. ACUTE ELUTION OF TGFβ2 AFFECTS THE SMOOTH MUSCLE CELLS IN A COMPLIANCE-MATCHED VASCULAR GRAFT. Tissue Eng Part A 2022; 28:640-650. [PMID: 35521649 DOI: 10.1089/ten.tea.2021.0161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Transforming growth factor beta 2 (TGFβ2) is a pleiotropic growth factor that plays a vital role in smooth muscle cell (SMC) function. Our prior in vitro work has shown that SMC response can be modulated with TGFβ2 stimulation in a dose dependent manner. In particular, we have shown that increasing concentrations of TGFβ2 shift SMCs from a migratory to a synthetic behavior. In this work, electrospun compliance-matched and hypocompliant TGFβ2-eluting TEVGs were implanted into Sprague Dawley rats for 5 days to observe SMC population and collagen production. TEVGs were fabricated using a combined computational and experimental approach that varied the ratio of gelatin:polycaprolactone to be either compliance-matched or twice as stiff as rat aorta (hypocompliant). TGFβ2 concentrations of 0, 10, 100 ng/mg were added to both graft types (n=3 in each group) and imaged in vivo using ultrasound. Histological markers (SMC, macrophage, collagen, and elastin) were evaluated following explantation at 5 days. In vivo ultrasound showed that compliance-matched TEVGs became stiffer as TGFβ2 increased (100 ng/mg TEVGS compared to rat aorta, p<0.01) while all hypocompliant grafts remained stiffer than control rat aorta. In vivo velocity and diameter were also not significantly different than control vessels. The compliance-matched 10 ng/mg group had an elevated SMC signal (myosin heavy chain) compared to the 0 and 100 ng/mg grafts (p=0.0009 & 0.0006 ). Compliance-matched TEVGs containing 100 ng/mg TGFβ2 had an increase in collagen production (p<0.01), general immune response (p<0.05), and a decrease in SMC population to the 0 and 10 ng/mg groups. All hypocompliant groups were found to be similar, suggesting a lower rate of TGFβ2 release in these TEVGs. Our results suggest that TGFβ2 can modulate in vivo SMC phenotype over an acute implantation period, which is consistent with our prior in vitro work. To the author's knowledge, this is first in vivo rat study that evaluates a TGFβ2-eluting TEVG.
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Affiliation(s)
- Kenneth John Furdella
- University of Pittsburgh Swanson School of Engineering, 110071, Bioengineering, Pittsburgh, Pennsylvania, United States;
| | - Shinichi Higuchi
- University of Pittsburgh Swanson School of Engineering, 110071, McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States;
| | - Kang Kim
- University of Pittsburgh Swanson School of Engineering, 110071, Department of Bioengineering, Pittsburgh, Pennsylvania, United States;
| | - Tom Doetschman
- University of Arizona Biochemistry and Molecular and Cellular Biology program, 242717, Tucson, Arizona, United States;
| | - William R Wagner
- University of Pittsburgh, 6614, McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania, United States;
| | - Jonathan P Vande Geest
- University of Pittsburgh Swanson School of Engineering, 110071, Bioengineering, Pittsburgh, Pennsylvania, United States;
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6
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Drews JD, Pepper VK, Best CA, Szafron JM, Cheatham JP, Yates AR, Hor KN, Zbinden JC, Chang YC, Mirhaidari GJM, Ramachandra AB, Miyamoto S, Blum KM, Onwuka EA, Zakko J, Kelly J, Cheatham SL, King N, Reinhardt JW, Sugiura T, Miyachi H, Matsuzaki Y, Breuer J, Heuer ED, West TA, Shoji T, Berman D, Boe BA, Asnes J, Galantowicz M, Matsumura G, Hibino N, Marsden AL, Pober JS, Humphrey JD, Shinoka T, Breuer CK. Spontaneous reversal of stenosis in tissue-engineered vascular grafts. Sci Transl Med 2021; 12:12/537/eaax6919. [PMID: 32238576 DOI: 10.1126/scitranslmed.aax6919] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 10/27/2019] [Accepted: 02/21/2020] [Indexed: 12/12/2022]
Abstract
We developed a tissue-engineered vascular graft (TEVG) for use in children and present results of a U.S. Food and Drug Administration (FDA)-approved clinical trial evaluating this graft in patients with single-ventricle cardiac anomalies. The TEVG was used as a Fontan conduit to connect the inferior vena cava and pulmonary artery, but a high incidence of graft narrowing manifested within the first 6 months, which was treated successfully with angioplasty. To elucidate mechanisms underlying this early stenosis, we used a data-informed, computational model to perform in silico parametric studies of TEVG development. The simulations predicted early stenosis as observed in our clinical trial but suggested further that such narrowing could reverse spontaneously through an inflammation-driven, mechano-mediated mechanism. We tested this unexpected, model-generated hypothesis by implanting TEVGs in an ovine inferior vena cava interposition graft model, which confirmed the prediction that TEVG stenosis resolved spontaneously and was typically well tolerated. These findings have important implications for our translational research because they suggest that angioplasty may be safely avoided in patients with asymptomatic early stenosis, although there will remain a need for appropriate medical monitoring. The simulations further predicted that the degree of reversible narrowing can be mitigated by altering the scaffold design to attenuate early inflammation and increase mechano-sensing by the synthetic cells, thus suggesting a new paradigm for optimizing next-generation TEVGs. We submit that there is considerable translational advantage to combined computational-experimental studies when designing cutting-edge technologies and their clinical management.
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Affiliation(s)
- Joseph D Drews
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Victoria K Pepper
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Cameron A Best
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Biomedical Sciences Graduate Program, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Jason M Szafron
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - John P Cheatham
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Andrew R Yates
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Kan N Hor
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Jacob C Zbinden
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Yu-Chun Chang
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Biomedical Sciences Graduate Program, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Gabriel J M Mirhaidari
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Biomedical Sciences Graduate Program, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Abhay B Ramachandra
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - Shinka Miyamoto
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Kevin M Blum
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Ekene A Onwuka
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - Jason Zakko
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - John Kelly
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Sharon L Cheatham
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Nakesha King
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
| | - James W Reinhardt
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Tadahisa Sugiura
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Hideki Miyachi
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Yuichi Matsuzaki
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Julie Breuer
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Eric D Heuer
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - T Aaron West
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Toshihiro Shoji
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Darren Berman
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Brian A Boe
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Jeremy Asnes
- Department of Pediatrics, Yale School of Medicine, New Haven, CT 06520, USA
| | - Mark Galantowicz
- The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Cardiothoracic Surgery, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Goki Matsumura
- Department of Cardiovascular Surgery, Tokyo Women's Medical University, Tokyo, Japan
| | - Narutoshi Hibino
- Department of Surgery, University of Chicago/Advocate Children's Hospital, Chicago, IL 60453, USA
| | - Alison L Marsden
- Departments of Pediatrics and Bioengineering, Stanford University, Stanford, CA 94304, USA
| | - Jordan S Pober
- Department of Immunobiology, Yale University, New Haven, CT 06520, USA
| | - Jay D Humphrey
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - Toshiharu Shinoka
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.,The Heart Center, Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Cardiothoracic Surgery, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Christopher K Breuer
- Center for Regenerative Medicine, Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA. .,Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA.,Department of Surgery, Nationwide Children's Hospital, Columbus, OH 43205, USA
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7
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Furdella KJ, Higuchi S, Behrangzade A, Kim K, Wagner WR, Vande Geest JP. In-vivo assessment of a tissue engineered vascular graft computationally optimized for target vessel compliance. Acta Biomater 2021; 123:298-311. [PMID: 33482362 DOI: 10.1016/j.actbio.2020.12.058] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 12/22/2020] [Accepted: 12/29/2020] [Indexed: 11/24/2022]
Abstract
Tissue engineered vascular grafts (TEVGs) have the ability to be tuned to match a target vessel's compliance, diameter, wall thickness, and thereby prevent compliance mismatch. In this work, TEVG compliance was manipulated by computationally tuning its layered composition or by manipulating a crosslinking agent (genipin). In particular, these three acelluluar TEVGs were compared: a compliance matched graft (CMgel - high gelatin content); a hypocompliant PCL graft (HYPOpcl - high polycaprolactone content); and a hypocompliant genipin graft (HYPOgen - equivalent composition as CMgel but hypocompliant via increased genipin crosslinking). All constructs were implanted interpositionally into the abdominal aorta of 21 Sprague Dawley rats (n=7, males=11, females=10) for 28 days, imaged in-vivo using ultrasound, explanted, and assessed for remodeling using immunofluorescence and two photon excitation fluorescence imaging. Compliance matched grafts remained compliance-matched in-vivo compared to the hypocompliant grafts through 4 weeks (p<0.05). Construct degradation and cellular infiltration was increased in the CMgel and HYPOgen TEVGs. Contractile smooth muscle cell markers in the proximal anastomosis of the graft were increased in the CMgel group compared to the HYPOpcl (p=0.007) and HYPOgen grafts (p=0.04). Both hypocompliant grafts also had an increased pro-inflammatory response (increased ratio of CD163 to CD86 in the mid-axial location) compared to the CMgel group. Our results suggest that compliance matching using a computational optimization approach leads to the improved acute (28 day) remodeling of TEVGs. To the authors' knowledge, this is the first in-vivo rat study investigating TEVGs that have been computationally optimized for target vessel compliance.
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8
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Rodriguez M, Kluge JA, Smoot D, Kluge MA, Schmidt DF, Paetsch CR, Kim PS, Kaplan DL. Fabricating mechanically improved silk-based vascular grafts by solution control of the gel-spinning process. Biomaterials 2020; 230:119567. [PMID: 31761485 PMCID: PMC6942127 DOI: 10.1016/j.biomaterials.2019.119567] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 10/16/2019] [Accepted: 10/17/2019] [Indexed: 11/30/2022]
Abstract
There is a large unmet need for off-the-shelf biomaterial options to supplant venous autografts in bypass and reconstructive surgical procedures. Existing graft alternatives formed from non-degradable synthetic polymers are not capable of maintaining long-term patency and are thus not indicated for <6 mm inner diameter bypass procedures. To fill this void, degradable silk-based biomaterials have been proposed that can maintain their mechanical properties (i.e. compliance) while facilitating slow but progressive biomaterial remodeling and host integration mediated by cellular colonization. The goal of the present study was to enhance the porosity of gel-spun silk tubes, to facilitate faster degradation rates and improve cellularity, and thus improve host integration over time in vivo, while maintaining requisite mechanical functions. Silk solutions with a range of molecular weight distributions and, in turn, viscosities were used to generate tubes of varying porosities. A decrease in solution concentration correlated with an increase in mean pore size and overall porosity through a density-dependent mechanism. Tubes were mechanically analyzed, and these properties were the basis of an analytical model used to correlate tube formulations to structural compliance, which were shown to be similar to the saphenous vein. Tubes were also tested for suture retention to ensure surgical utility despite increased porosity. Tubes were implanted in the abdominal aorta of Sprague-Dawley rats via an end-to-end anastomosis model. Tubes with higher porosities showed early improvements in cell colonization that progressively increased over time; conversely, the dense architecture of less porous grafts (20MB) inhibited cell ingrowth and resulted in minimal biomaterial degradation at the 6-month time point. None of the highly porous tubes (5 MB and 10MB) remained patent at 6 months, likely due remodeling inducing bulk mechanical failure or a compromised blood-material interface.
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Affiliation(s)
- Maria Rodriguez
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA, 02155, USA
| | - Jonathan A Kluge
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA, 02155, USA
| | - Daniel Smoot
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA, 02155, USA
| | - Matthew A Kluge
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA, 02155, USA
| | - Daniel F Schmidt
- Department of Plastics Engineering, University of Massachusetts Lowell, Lowell, MA, 01854, USA; Department of Materials Research & Technology, Luxembourg Institute of Science & Technology, L-4940, Hautcharage, Luxembourg
| | - Christopher R Paetsch
- Tufts University, Department of Civil Engineering, 200 College Avenue, Medford, MA, 02155, USA
| | - Peter S Kim
- Divisions of Plastic Surgery and Otolaryngology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA.
| | - David L Kaplan
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, MA, 02155, USA.
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9
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Emuna N, Durban D, Osovski S. Sensitivity of Arterial Hyperelastic Models to Uncertainties in Stress-Free Measurements. J Biomech Eng 2019; 140:2683233. [PMID: 30029245 DOI: 10.1115/1.4040400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Indexed: 12/14/2022]
Abstract
Despite major advances made in modeling vascular tissue biomechanics, the predictive power of constitutive models is still limited by uncertainty of the input data. Specifically, key measurements, like the geometry of the stress-free (SF) state, involve a definite, sometimes non-negligible, degree of uncertainty. Here, we introduce a new approach for sensitivity analysis of vascular hyperelastic constitutive models to uncertainty in SF measurements. We have considered two vascular hyperelastic models: the phenomenological Fung model and the structure-motivated Holzapfel-Gasser-Ogden (HGO) model. Our results indicate up to 160% errors in the identified constitutive parameters for a 5% measurement uncertainty in the SF data. Relative margins of errors of up to 30% in the luminal pressure, 36% in the axial force, and over 200% in the stress predictions were recorded for 10% uncertainties. These findings are relevant to the large body of studies involving experimentally based modeling and analysis of vascular tissues. The impact of uncertainties on calibrated constitutive parameters is significant in context of studies that use constitutive parameters to draw conclusions about the underlying microstructure of vascular tissues, their growth and remodeling processes, and aging and disease states. The propagation of uncertainties into the predictions of biophysical parameters, e.g., force, luminal pressure, and wall stresses, is of practical importance in the design and execution of clinical devices and interventions. Furthermore, insights provided by the present findings may lead to more robust parameters identification techniques, and serve as selection criteria in the trade-off between model complexity and sensitivity.
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Affiliation(s)
- Nir Emuna
- Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel e-mail:
| | - David Durban
- Faculty of Aerospace Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel e-mail:
| | - Shmuel Osovski
- Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel e-mail:
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10
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Ardila DC, Tamimi E, Doetschman T, Wagner WR, Vande Geest JP. Modulating smooth muscle cell response by the release of TGFβ2 from tubular scaffolds for vascular tissue engineering. J Control Release 2019. [PMID: 30797003 DOI: 10.1016/j.jconrel.2019.02.0241016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Tissue engineering has gained considerable attention in the development of small diameter tissue engineered vascular grafts (TEVGs) for treating coronary heart disease. A properly designed acellular and biodegradable TEVG must encourage the infiltration and growth of vascular smooth muscle cells (SMCs). Our group has previously shown that increasing levels of TGFβ2 can differentially modulate SMC migration and proliferation. In this study, tubular electrospun scaffolds loaded with TGFβ2 were fabricated using various ratios of gelatin/polycaprolactone (PCL), resulting in scaffolds with porous nano-woven architecture suitable for tissue ingrowth. Scaffold morphology, degradation rate, TGβ2 release kinetics, and bioactivity were assessed. TGFβ2 was successfully integrated into the electrospun biomaterial that resulted in a differential release profile depending on the gelatin/PCL ratio over the course of 42 days. Higher TGFβ2 elution was obtained in scaffolds with higher gelatin content, which may be related to the biodegradation of gelatin in culture media. The biological activity of the released TGFβ2 was evaluated by its ability to affect SMC proliferation as a function of its concentration. SMCs seeded on TGFβ2-loaded scaffolds also showed higher densities and infiltration after 5 days in culture as compared to scaffolds without TGFβ2. Our results demonstrate that the ratio of synthetic and natural polymers in electrospun blends can be used to tune the release of TGFβ2. This method can be used to intelligently modulate the SMC response in gelatin/PCL scaffolds making the TGFβ2-loaded conduits attractive for cardiovascular tissue engineering applications.
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Affiliation(s)
- D C Ardila
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - E Tamimi
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - T Doetschman
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, AZ 85721, USA; BIO5 Institute, The University of Arizona, Tucson, AZ 85724, USA
| | - W R Wagner
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - J P Vande Geest
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA 15219, USA.
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Ardila DC, Tamimi E, Doetschman T, Wagner WR, Vande Geest JP. Modulating smooth muscle cell response by the release of TGFβ2 from tubular scaffolds for vascular tissue engineering. J Control Release 2019; 299:44-52. [PMID: 30797003 PMCID: PMC6430660 DOI: 10.1016/j.jconrel.2019.02.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 01/25/2019] [Accepted: 02/19/2019] [Indexed: 01/01/2023]
Abstract
Tissue engineering has gained considerable attention in the development of small diameter tissue engineered vascular grafts (TEVGs) for treating coronary heart disease. A properly designed acellular and biodegradable TEVG must encourage the infiltration and growth of vascular smooth muscle cells (SMCs). Our group has previously shown that increasing levels of TGFβ2 can differentially modulate SMC migration and proliferation. In this study, tubular electrospun scaffolds loaded with TGFβ2 were fabricated using various ratios of gelatin/polycaprolactone (PCL), resulting in scaffolds with porous nano-woven architecture suitable for tissue ingrowth. Scaffold morphology, degradation rate, TGβ2 release kinetics, and bioactivity were assessed. TGFβ2 was successfully integrated into the electrospun biomaterial that resulted in a differential release profile depending on the gelatin/PCL ratio over the course of 42 days. Higher TGFβ2 elution was obtained in scaffolds with higher gelatin content, which may be related to the biodegradation of gelatin in culture media. The biological activity of the released TGFβ2 was evaluated by its ability to affect SMC proliferation as a function of its concentration. SMCs seeded on TGFβ2-loaded scaffolds also showed higher densities and infiltration after 5 days in culture as compared to scaffolds without TGFβ2. Our results demonstrate that the ratio of synthetic and natural polymers in electrospun blends can be used to tune the release of TGFβ2. This method can be used to intelligently modulate the SMC response in gelatin/PCL scaffolds making the TGFβ2-loaded conduits attractive for cardiovascular tissue engineering applications.
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Affiliation(s)
- D C Ardila
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - E Tamimi
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - T Doetschman
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, AZ 85721, USA; BIO5 Institute, The University of Arizona, Tucson, AZ 85724, USA
| | - W R Wagner
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - J P Vande Geest
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA 15219, USA.
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Tamimi EA, Ardila DC, Ensley BD, Kellar RS, Vande Geest J. Computationally optimizing the compliance of multilayered biomimetic tissue engineered vascular grafts. J Biomech Eng 2019; 141:2725826. [PMID: 30778568 DOI: 10.1115/1.4042902] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Indexed: 12/19/2022]
Abstract
Coronary artery bypass grafts used to treat coronary artery disease often fail due to compliance mismatch. In this study, we have developed an experimental/computational approach to fabricate an acellular biomimetic hybrid tissue engineered vascular graft composed of alternating layers of electrospun porcine gelatin/polycaprolactone (PCL) and human tropoelastin/PCL blends with the goal of compliance-matching to rat abdominal aorta, while maintaining specific geometrical constraints. Polymeric blends at three different gelatin:PCL (G:PCL) and tropoelastin:PCL (T:PCL) ratios (80:20, 50:50 and 20:80) were mechanically characterized. The stress-strain data was used to develop predictive models, which were used as part of an optimization scheme that was implemented to determine the ratios of G:PCL and T:PCL and the thickness of the individual layers within a tissue engineered vascular graft that would compliance match a target compliance value. The hypocompliant, isocompliant, and hypercompliant grafts had target compliance values of 0.000256, 0.000568 and 0.000880 mmHg-1, respectively. Experimental validation of the optimization demonstrated that the hypercompliant and isocompliant grafts were not statistically significant from their respective target compliance values (p-value=0.37 and 0.89, respectively). The experimental compliance value of the hypocompliant graft was statistically significant than their target compliance value (p-value=0.047). We have successfully demonstrated a design optimization scheme that can be used to fabricate multilayered and biomimetic vascular grafts with targeted geometry and compliance.
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Affiliation(s)
- Ehab Akram Tamimi
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Diana Catalina Ardila
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | | | - Robert S Kellar
- Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, AZ, 86011; Department of Mechanical Engineering, Northern Arizona University, Flagstaff, AZ, 86011; Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011
| | - Jonathan Vande Geest
- ASME Member, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States, McGowan Institute for Regenerative Medicine, 300 Technology Drive, Pittsburgh, PA, United State 15219
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Colunga T, Dalton S. Building Blood Vessels with Vascular Progenitor Cells. Trends Mol Med 2018; 24:630-641. [PMID: 29802036 PMCID: PMC6050017 DOI: 10.1016/j.molmed.2018.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/02/2018] [Accepted: 05/03/2018] [Indexed: 12/20/2022]
Abstract
Vascular progenitor cells have been identified from perivascular cell fractions and peripheral blood and bone marrow mononuclear fractions. These vascular progenitors share the ability to generate some of the vascular lineages, including endothelial cells, smooth muscle cells, and pericytes. The potential therapeutic uses for vascular progenitor cells are broad and relate to stroke, ischemic disease, and to the engineering of whole organs and tissues that require a vascular component. This review summarizes the best-characterized sources of vascular progenitor cells and discusses advances in 3D printing and electrospinning using blended polymers for the creation of biomimetic vascular grafts. These advances are pushing the field of regenerative medicine closer to the creation of small-diameter vascular grafts with long-term clinical utility.
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Affiliation(s)
- Thomas Colunga
- Center for Molecular Medicine, University of Georgia, 325 Riverbend Road, Athens, GA 30605, USA; Department of Biochemistry and Molecular Biology, University of Georgia, 325 Riverbend Road, Athens, GA 30605, USA
| | - Stephen Dalton
- Center for Molecular Medicine, University of Georgia, 325 Riverbend Road, Athens, GA 30605, USA; Department of Biochemistry and Molecular Biology, University of Georgia, 325 Riverbend Road, Athens, GA 30605, USA.
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Szafron JM, Breuer CK, Wang Y, Humphrey JD. Stress Analysis-Driven Design of Bilayered Scaffolds for Tissue-Engineered Vascular Grafts. J Biomech Eng 2018; 139:2653976. [PMID: 28886204 DOI: 10.1115/1.4037856] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Indexed: 12/28/2022]
Abstract
Continuing advances in the fabrication of scaffolds for tissue-engineered vascular grafts (TEVGs) are greatly expanding the scope of potential designs. Increasing recognition of the importance of local biomechanical cues for cell-mediated neotissue formation, neovessel growth, and subsequent remodeling is similarly influencing the design process. This study examines directly the potential effects of different combinations of key geometric and material properties of polymeric scaffolds on the initial mechanical state of an implanted graft into which cells are seeded or migrate. Toward this end, we developed a bilayered computational model that accounts for layer-specific thickness and stiffness as well as the potential to be residually stressed during fabrication or to swell during implantation. We found that, for realistic ranges of parameter values, the circumferential stress that would be presented to seeded or infiltrating cells is typically much lower than ideal, often by an order of magnitude. Indeed, accounting for layer-specific intrinsic swelling resulting from hydrophilicity or residual stresses not relieved via annealing revealed potentially large compressive stresses, which could lead to unintended cell phenotypes and associated maladaptive growth or, in extreme cases, graft failure. Metrics of global hemodynamics were also found to be inversely related to markers of a favorable local mechanobiological environment, suggesting a tradeoff in designs that seek mechanical homeostasis at a single scale. These findings highlight the importance of the initial mechanical state in tissue engineering scaffold design and the utility of computational modeling in reducing the experimental search space for future graft development and testing.
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Affiliation(s)
- Jason M Szafron
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520 e-mail:
| | - Christopher K Breuer
- Tissue Engineering Program, Nationwide Children's Hospital, Columbus, OH 43215 e-mail:
| | - Yadong Wang
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853 e-mail:
| | - Jay D Humphrey
- Fellow ASME Department of Biomedical Engineering, Yale University, New Haven, CT 06520 e-mail:
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