1
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Sacks MS. A Mathematical Model for Postimplant Collagen Remodeling in an Autologous Engineered Pulmonary Arterial Conduit. J Biomech Eng 2024; 146:111006. [PMID: 38980683 PMCID: PMC11369691 DOI: 10.1115/1.4065903] [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: 02/03/2024] [Revised: 07/03/2024] [Accepted: 07/05/2024] [Indexed: 07/10/2024]
Abstract
This study was undertaken to develop a mathematical model of the long-term in vivo remodeling processes in postimplanted pulmonary artery (PA) conduits. Experimental results from two extant ovine in vivo studies, wherein polyglycolic-acid (PGA)/poly-L-lactic acid tubular conduits were constructed, cell seeded, incubated for 4 weeks, and then implanted in mature sheep to obtain the remodeling data for up to two years. Explanted conduit analysis included detailed novel structural and mechanical studies. Results in both studies indicated that the in vivo conduits remained dimensionally stable up to 80 weeks, so that the conduits maintained a constant in vivo stress and deformation state. In contrast, continued remodeling of the constituent collagen fiber network as evidenced by an increase in effective tissue uniaxial tangent modulus, which then stabilized by one year postimplant. A mesostructural constitute model was then applied to extant planar biaxial mechanical data and revealed several interesting features, including an initial pronounced increase in effective collagen fiber modulus, paralleled by a simultaneous shift toward longer, more uniformly length-distributed collagen fibers. Thus, while the conduit remained dimensionally stable, its internal collagen fibrous structure and resultant mechanical behaviors underwent continued remodeling that stabilized by one year. A time-evolving structural mixture-based mathematical model specialized for this unique form of tissue remodeling was developed, with a focus on time-evolving collagen fiber stiffness as the driver for tissue-level remodeling. The remodeling model was able to fully reproduce (1) the observed tissue-level increases in stiffness by time-evolving simultaneous increases in collagen fiber modulus and lengths, (2) maintenance of the constant collagen fiber angular dispersion, and (3) stabilization of the remodeling processes at one year. Collagen fiber remodeling geometry was directly verified experimentally by histological analysis of the time-evolving collagen fiber crimp, which matches model predictions very closely. Interestingly, the remodeling model indicated that the basis for tissue homeostasis was maintenance of the collagen fiber ensemble stress for all orientations, and not individual collagen fiber stresses. Unlike other growth and remodeling models that traditionally treat changes in the external boundary conditions (e.g., changes in blood pressure) as the primary input stimuli, the driver herein is changes to the internal constituent collagen fiber themselves due to cellular mediated cross-linking.
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Affiliation(s)
- Michael S Sacks
- James T. Willerson Center for Cardiovascular Modeling and Simulation, The Oden Institute for Computational Engineering and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
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2
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Nguyen-Truong M, Li YV, Wang Z. Mechanical Considerations of Electrospun Scaffolds for Myocardial Tissue and Regenerative Engineering. Bioengineering (Basel) 2020; 7:E122. [PMID: 33022929 PMCID: PMC7711753 DOI: 10.3390/bioengineering7040122] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/25/2020] [Accepted: 10/01/2020] [Indexed: 12/13/2022] Open
Abstract
Biomaterials to facilitate the restoration of cardiac tissue is of emerging importance. While there are many aspects to consider in the design of biomaterials, mechanical properties can be of particular importance in this dynamically remodeling tissue. This review focuses on one specific processing method, electrospinning, that is employed to generate materials with a fibrous microstructure that can be combined with material properties to achieve the desired mechanical behavior. Current methods used to fabricate mechanically relevant micro-/nanofibrous scaffolds, in vivo studies using these scaffolds as therapeutics, and common techniques to characterize the mechanical properties of the scaffolds are covered. We also discuss the discrepancies in the reported elastic modulus for physiological and pathological myocardium in the literature, as well as the emerging area of in vitro mechanobiology studies to investigate the mechanical regulation in cardiac tissue engineering. Lastly, future perspectives and recommendations are offered in order to enhance the understanding of cardiac mechanobiology and foster therapeutic development in myocardial regenerative medicine.
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Affiliation(s)
- Michael Nguyen-Truong
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA; (M.N.-T.); (Y.V.L.)
| | - Yan Vivian Li
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA; (M.N.-T.); (Y.V.L.)
- Department of Design and Merchandising, Colorado State University, Fort Collins, CO 80523, USA
- School of Advanced Materials Discovery, Colorado State University, Fort Collins, CO 80523, USA
| | - Zhijie Wang
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA; (M.N.-T.); (Y.V.L.)
- Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USA
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3
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Ippel B, Van Haaften EE, Bouten CVC, Dankers PYW. Impact of Additives on Mechanical Properties of Supramolecular Electrospun Scaffolds. ACS APPLIED POLYMER MATERIALS 2020; 2:3742-3748. [PMID: 32954355 PMCID: PMC7497720 DOI: 10.1021/acsapm.0c00658] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 08/18/2020] [Indexed: 06/11/2023]
Abstract
The mechanical properties of scaffolds used for mechanically challenging applications such as cardiovascular implants are unequivocally important. Here, the effect of supramolecular additive functionalization on mechanical behavior of electrospun scaffolds was investigated for one bisurea-based model additive and two previously developed antifouling additives. The model additive has no effect on the mechanical properties of the bulk material, whereas the stiffness of electrospun scaffolds was slightly decreased compared to pristine PCL-BU following the addition of the three different additives. These results show the robustness of supramolecular additives used in biomedical applications, in which mechanical properties are important, such as vascular grafts and heart valve constructs.
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Affiliation(s)
- Bastiaan
D. Ippel
- Institute
for Complex Molecular Systems, Eindhoven
University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory
for Cell and Tissue Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
| | - Eline E. Van Haaften
- Institute
for Complex Molecular Systems, Eindhoven
University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory
for Cell and Tissue Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
| | - Carlijn V. C. Bouten
- Institute
for Complex Molecular Systems, Eindhoven
University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory
for Cell and Tissue Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
| | - Patricia Y. W. Dankers
- Institute
for Complex Molecular Systems, Eindhoven
University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory
for Cell and Tissue Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Laboratory
of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
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4
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Carleton JB, Rodin GJ, Sacks MS. Layered Elastomeric Fibrous Scaffolds: An In-Silico Study of the Achievable Range of Mechanical Behaviors. ACS Biomater Sci Eng 2017; 3:2907-2921. [DOI: 10.1021/acsbiomaterials.7b00308] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- James B. Carleton
- Center
for Cardiovascular Simulation, Institute for Computational Engineering
and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Austin, Texas 78712, United States
| | - Gregory J. Rodin
- Center
for Cardiovascular Simulation, Institute for Computational Engineering
and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Austin, Texas 78712, United States
- Department
of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, 210 East 24th Street, Austin, Texas 78712, United States
| | - Michael S. Sacks
- Center
for Cardiovascular Simulation, Institute for Computational Engineering
and Sciences and the Department of Biomedical Engineering, The University of Texas at Austin, 201 East 24th Street, Austin, Texas 78712, United States
- Department
of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, 210 East 24th Street, Austin, Texas 78712, United States
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5
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Stearns-Reider KM, D'Amore A, Beezhold K, Rothrauff B, Cavalli L, Wagner WR, Vorp DA, Tsamis A, Shinde S, Zhang C, Barchowsky A, Rando TA, Tuan RS, Ambrosio F. Aging of the skeletal muscle extracellular matrix drives a stem cell fibrogenic conversion. Aging Cell 2017; 16:518-528. [PMID: 28371268 PMCID: PMC5418187 DOI: 10.1111/acel.12578] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2017] [Indexed: 12/13/2022] Open
Abstract
Age‐related declines in skeletal muscle regeneration have been attributed to muscle stem cell (MuSC) dysfunction. Aged MuSCs display a fibrogenic conversion, leading to fibrosis and impaired recovery after injury. Although studies have demonstrated the influence of in vitro substrate characteristics on stem cell fate, whether and how aging of the extracellular matrix (ECM) affects stem cell behavior has not been investigated. Here, we investigated the direct effect of the aged muscle ECM on MuSC lineage specification. Quantification of ECM topology and muscle mechanical properties reveals decreased collagen tortuosity and muscle stiffening with increasing age. Age‐related ECM alterations directly disrupt MuSC responses, and MuSCs seeded ex vivo onto decellularized ECM constructs derived from aged muscle display increased expression of fibrogenic markers and decreased myogenicity, compared to MuSCs seeded onto young ECM. This fibrogenic conversion is recapitulated in vitro when MuSCs are seeded directly onto matrices elaborated by aged fibroblasts. When compared to young fibroblasts, fibroblasts isolated from aged muscle display increased nuclear levels of the mechanosensors, Yes‐associated protein (YAP)/transcriptional coactivator with PDZ‐binding motif (TAZ), consistent with exposure to a stiff microenvironment in vivo. Accordingly, preconditioning of young fibroblasts by seeding them onto a substrate engineered to mimic the stiffness of aged muscle increases YAP/TAZ nuclear translocation and promotes secretion of a matrix that favors MuSC fibrogenesis. The findings here suggest that an age‐related increase in muscle stiffness drives YAP/TAZ‐mediated pathogenic expression of matricellular proteins by fibroblasts, ultimately disrupting MuSC fate.
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Affiliation(s)
- Kristen M. Stearns-Reider
- Department of Physical Medicine and Rehabilitation; University of Pittsburgh; Kaufmann Medical Building, Suite 201, 3471 Fifth Avenue Pittsburgh PA 15213 USA
- McGowan Institute for Regenerative Medicine; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
| | - Antonio D'Amore
- Department of Surgery; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
| | - Kevin Beezhold
- Department of Environmental and Occupational Health; University of Pittsburgh; 100 Technology Drive, Suite 328 Pittsburgh PA 15219 USA
| | - Benjamin Rothrauff
- Center for Cellular and Molecular Engineering; Department of Orthopaedic Surgery; University of Pittsburgh; 450 Technology Drive, Bridgeside Point II, Suite 221 Pittsburgh PA 15219 USA
| | - Loredana Cavalli
- Department of Physical Medicine and Rehabilitation; University of Pittsburgh; Kaufmann Medical Building, Suite 201, 3471 Fifth Avenue Pittsburgh PA 15213 USA
| | - William R. Wagner
- McGowan Institute for Regenerative Medicine; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Department of Surgery; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Center for Vascular Remodeling and Regeneration; Center for Bioengineering (CNBIO); University of Pittsburgh; 300 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
| | - David A. Vorp
- McGowan Institute for Regenerative Medicine; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Department of Surgery; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Center for Vascular Remodeling and Regeneration; Center for Bioengineering (CNBIO); University of Pittsburgh; 300 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Department of Bioengineering; University of Pittsburgh; 213 Center for Bioengineering, 300 Technology Drive Pittsburgh PA 15219 USA
| | - Alkiviadis Tsamis
- Department of Engineering; University of Leicester; 127 Michael Atiyah Building, University Road Leicester LE1 7RH UK
| | - Sunita Shinde
- Department of Physical Medicine and Rehabilitation; University of Pittsburgh; Kaufmann Medical Building, Suite 201, 3471 Fifth Avenue Pittsburgh PA 15213 USA
| | - Changqing Zhang
- Department of Physical Medicine and Rehabilitation; University of Pittsburgh; Kaufmann Medical Building, Suite 201, 3471 Fifth Avenue Pittsburgh PA 15213 USA
| | - Aaron Barchowsky
- Department of Environmental and Occupational Health; University of Pittsburgh; 100 Technology Drive, Suite 328 Pittsburgh PA 15219 USA
| | - Thomas A. Rando
- Glenn Center for the Biology of Aging and Department of Neurology and Neurological Sciences; Stanford University School of Medicine; Stanford CA 94305 USA
- RR&D Center; VA Palo Alto Health Care System; Palo Alto CA 94304 USA
| | - Rocky S. Tuan
- McGowan Institute for Regenerative Medicine; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Center for Cellular and Molecular Engineering; Department of Orthopaedic Surgery; University of Pittsburgh; 450 Technology Drive, Bridgeside Point II, Suite 221 Pittsburgh PA 15219 USA
| | - Fabrisia Ambrosio
- Department of Physical Medicine and Rehabilitation; University of Pittsburgh; Kaufmann Medical Building, Suite 201, 3471 Fifth Avenue Pittsburgh PA 15213 USA
- McGowan Institute for Regenerative Medicine; University of Pittsburgh; 450 Technology Drive, Suite 300 Pittsburgh PA 15219 USA
- Department of Bioengineering; University of Pittsburgh; 213 Center for Bioengineering, 300 Technology Drive Pittsburgh PA 15219 USA
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6
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D'Amore A, Soares JS, Stella JA, Zhang W, Amoroso NJ, Mayer JE, Wagner WR, Sacks MS. Large strain stimulation promotes extracellular matrix production and stiffness in an elastomeric scaffold model. J Mech Behav Biomed Mater 2016; 62:619-635. [PMID: 27344402 PMCID: PMC4955736 DOI: 10.1016/j.jmbbm.2016.05.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 04/30/2016] [Accepted: 05/03/2016] [Indexed: 01/07/2023]
Abstract
Mechanical conditioning of engineered tissue constructs is widely recognized as one of the most relevant methods to enhance tissue accretion and microstructure, leading to improved mechanical behaviors. The understanding of the underlying mechanisms remains rather limited, restricting the development of in silico models of these phenomena, and the translation of engineered tissues into clinical application. In the present study, we examined the role of large strip-biaxial strains (up to 50%) on ECM synthesis by vascular smooth muscle cells (VSMCs) micro-integrated into electrospun polyester urethane urea (PEUU) constructs over the course of 3 weeks. Experimental results indicated that VSMC biosynthetic behavior was quite sensitive to tissue strain maximum level, and that collagen was the primary ECM component synthesized. Moreover, we found that while a 30% peak strain level achieved maximum ECM synthesis rate, further increases in strain level lead to a reduction in ECM biosynthesis. Subsequent mechanical analysis of the formed collagen fiber network was performed by removing the scaffold mechanical responses using a strain-energy based approach, showing that the denovo collagen also demonstrated mechanical behaviors substantially better than previously obtained with small strain training and comparable to mature collagenous tissues. We conclude that the application of large deformations can play a critical role not only in the quantity of ECM synthesis (i.e. the rate of mass production), but also on the modulation of the stiffness of the newly formed ECM constituents. The improved understanding of the process of growth and development of ECM in these mechano-sensitive cell-scaffold systems will lead to more rational design and manufacturing of engineered tissues operating under highly demanding mechanical environments.
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Affiliation(s)
- Antonio D'Amore
- Department of Bioengineering McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Fondazione RiMED, Italy; DICGIM, Università di Palermo, Italy
| | - Joao S Soares
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - John A Stella
- Department of Bioengineering McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Will Zhang
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Nicholas J Amoroso
- Department of Bioengineering McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - John E Mayer
- Department of Cardiac Surgery Boston Children׳s Hospital and Harvard Medical School, Boston, MA, USA
| | - William R Wagner
- Department of Bioengineering McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA.
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7
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Carleton JB, D'Amore A, Feaver KR, Rodin GJ, Sacks MS. Geometric characterization and simulation of planar layered elastomeric fibrous biomaterials. Acta Biomater 2015; 12:93-101. [PMID: 25311685 DOI: 10.1016/j.actbio.2014.09.049] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 08/28/2014] [Accepted: 09/28/2014] [Indexed: 11/17/2022]
Abstract
Many important biomaterials are composed of multiple layers of networked fibers. While there is a growing interest in modeling and simulation of the mechanical response of these biomaterials, a theoretical foundation for such simulations has yet to be firmly established. Moreover, correctly identifying and matching key geometric features is a critically important first step for performing reliable mechanical simulations. The present work addresses these issues in two ways. First, using methods of geometric probability, we develop theoretical estimates for the mean linear and areal fiber intersection densities for 2-D fibrous networks. These densities are expressed in terms of the fiber density and the orientation distribution function, both of which are relatively easy-to-measure properties. Secondly, we develop a random walk algorithm for geometric simulation of 2-D fibrous networks which can accurately reproduce the prescribed fiber density and orientation distribution function. Furthermore, the linear and areal fiber intersection densities obtained with the algorithm are in agreement with the theoretical estimates. Both theoretical and computational results are compared with those obtained by post-processing of scanning electron microscope images of actual scaffolds. These comparisons reveal difficulties inherent to resolving fine details of multilayered fibrous networks. The methods provided herein can provide a rational means to define and generate key geometric features from experimentally measured or prescribed scaffold structural data.
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Affiliation(s)
- James B Carleton
- Center for Cardiovascular Simulation, Institute for Computational and Engineering Sciences, Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
| | - Antonio D'Amore
- McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Kristen R Feaver
- Center for Cardiovascular Simulation, Institute for Computational and Engineering Sciences, Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
| | - Gregory J Rodin
- Center for Cardiovascular Simulation, Institute for Computational and Engineering Sciences, Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA; Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, TX 78712, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational and Engineering Sciences, Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA.
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8
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D'Amore A, Amoroso N, Gottardi R, Hobson C, Carruthers C, Watkins S, Wagner WR, Sacks MS. From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials. J Mech Behav Biomed Mater 2014; 39:146-61. [PMID: 25128869 PMCID: PMC4165725 DOI: 10.1016/j.jmbbm.2014.07.016] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/07/2014] [Accepted: 07/15/2014] [Indexed: 11/20/2022]
Abstract
In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters adjusted to match the macro-level mechanical test data. Fiber model validation was performed at the microscopic level by individual fiber mechanical tests using AFM. Results demonstrated very good agreement to the experimental data, and revealed the formation of extended preferential fiber orientations spanning the entire model space. We speculate that these emergent structures may be responsible for the tissue-like macroscale behaviors observed in electrospun scaffolds. To conclude, the modeling approach has implications for (1) gaining insight on the intricate relationship between fabrication variables, structure, and mechanics to manufacture more functional devices/materials, (2) elucidating the effects of cell or particulate inclusions on global construct mechanics, and (3) fabricating better performing tissue surrogates that could recapitulate native tissue mechanics.
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Affiliation(s)
- Antonio D'Amore
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA; Fondazione RiMED, Italy; DICGIM, University of Palermo, Italy
| | - Nicholas Amoroso
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA
| | - Riccardo Gottardi
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA; Fondazione RiMED, Italy
| | - Christopher Hobson
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA
| | - Christopher Carruthers
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA
| | - Simon Watkins
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA
| | - William R Wagner
- McGowan Institute for Regenerative Medicine, Department of Bioengineering and Surgery, University of Pittsburgh, USA
| | - Michael S Sacks
- Center for Cardiovascular Simulation, Institute for Computational and Engineering Sciences, Department of Biomedical Engineering, University of Texas at Austin, TX 78712, USA.
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9
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Nezarati RM, Eifert MB, Dempsey DK, Cosgriff-Hernandez E. Electrospun vascular grafts with improved compliance matching to native vessels. J Biomed Mater Res B Appl Biomater 2014; 103:313-23. [PMID: 24846218 DOI: 10.1002/jbm.b.33201] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 03/25/2014] [Accepted: 04/21/2014] [Indexed: 01/24/2023]
Abstract
Coronary artery bypass grafting is one of the most commonly performed major surgeries in the United States. Autologous vessels such as the saphenous vein are the current gold standard for treatment; however, synthetic vascular prostheses made of expanded poly(tetrafluoroethylene) or poly(ethylene terephthalate) are used when autologous vessels are unavailable. These synthetic grafts have a high failure rate in small diameter (<4 mm) applications due to rapid reocclusion via intimal hyperplasia. Current strategies to improve clinical performance are focused on preventing intimal hyperplasia by fabricating grafts with compliance and burst pressure similar to native vessels. To this end, we have developed an electrospun vascular graft from segmented polyurethanes with tunable properties by altering material chemistry and graft microarchitecture. Relationships between polyurethane tensile properties and biomechanical properties were elucidated to select polymers with desirable properties. Graft thickness, fiber tortuosity, and fiber fusions were modulated to provide additional tools for controlling graft properties. Using a combination of these strategies, a vascular graft with compliance and burst pressure exceeding the saphenous vein autograft was fabricated (compliance = 6.0 ± 0.6%/mmHg × 10(-4) , burst pressure = 2260 ± 160 mmHg). This graft is hypothesized to reduce intimal hyperplasia associated with low compliance in synthetic grafts and improve long-term clinical success. Additionally, the fundamental relationships between electrospun mesh microarchitecture and mechanical properties identified in this work can be utilized in various biomedical applications.
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Affiliation(s)
- Roya M Nezarati
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, 77843-3120
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10
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Fiber stretch and reorientation modulates mesenchymal stem cell morphology and fibrous gene expression on oriented nanofibrous microenvironments. Ann Biomed Eng 2011; 39:2780-90. [PMID: 21800203 DOI: 10.1007/s10439-011-0365-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 07/18/2011] [Indexed: 10/17/2022]
Abstract
Because differentiation of mesenchymal stem cells (MSCs) is enacted through the integration of soluble signaling factors and physical cues, including substrate architecture and exogenous mechanical stimulation, it is important to understand how micropatterned biomaterials may be optimized to enhance differentiation for the formation of functional soft tissues. In this work, macroscopic strain applied to MSCs in an aligned nanofibrous microenvironment elicited cellular and nuclear deformations that varied depending on scaffold orientation. Reorientation of aligned, oriented MSCs corresponded at the microscopic scale with the affine approximation of their deformation based on macroscopic strains. Moreover, deformations at the subcellular scale corresponded with scaffold orientation, with changes in nuclear shape depending on the direction of substrate alignment. Notably, these deformations induced changes in gene expression that were also dependent on scaffold and cell orientations. These findings demonstrate that directional biases in substrate microstructure convey direction-dependent mechanosensitivity to MSCs and provide an experimental framework in which to explore the mechanistic underpinnings of this response.
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11
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Nerurkar NL, Han W, Mauck RL, Elliott DM. Homologous structure-function relationships between native fibrocartilage and tissue engineered from MSC-seeded nanofibrous scaffolds. Biomaterials 2010; 32:461-8. [PMID: 20880577 DOI: 10.1016/j.biomaterials.2010.09.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 09/06/2010] [Indexed: 01/21/2023]
Abstract
Understanding the interplay of composition, organization and mechanical function in load-bearing tissues is a prerequisite in the successful engineering of tissues to replace diseased ones. Mesenchymal stem cells (MSCs) seeded on electrospun scaffolds have been successfully used to generate organized tissues that mimic fibrocartilages such as the knee meniscus and the annulus fibrosus of the intervertebral disc. While matrix deposition has been observed in parallel with improved mechanical properties, how composition, organization, and mechanical function are related is not known. Moreover, how this relationship compares to that of native fibrocartilage is unclear. Therefore, in the present work, functional fibrocartilage constructs were formed from MSC-seeded nanofibrous scaffolds, and the roles of collagen and glycosaminoglycan (GAG) in compressive and tensile properties were determined. MSCs deposited abundant collagen and GAG over 120 days of culture, and these extracellular molecules were organized in such a way that they performed similar mechanical functions to their native roles: collagen dominated the tensile response while GAG was important for compressive properties. GAG removal resulted in significant stiffening in tension. A similar stiffening response was observed when GAG was removed from native inner annulus fibrosus, suggesting an interaction between collagen fibers and their surrounding extrafibrillar matrix that is shared by both engineered and native fibrocartilages. These findings strongly support the use of electrospun scaffolds and MSCs for fibrocartilage tissue engineering, and provide insight on the structure-function relations of both engineered and native biomaterials.
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Affiliation(s)
- Nandan L Nerurkar
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104-6081, USA
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12
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Stella JA, D'Amore A, Wagner WR, Sacks MS. On the biomechanical function of scaffolds for engineering load-bearing soft tissues. Acta Biomater 2010; 6:2365-81. [PMID: 20060509 DOI: 10.1016/j.actbio.2010.01.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 12/18/2009] [Accepted: 01/04/2010] [Indexed: 11/16/2022]
Abstract
Replacement or regeneration of load-bearing soft tissues has long been the impetus for the development of bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity, all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors.
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Affiliation(s)
- John A Stella
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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