1
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Mora KE, Mlawer SJ, Loiselle AE, Buckley MR. The Micromechanical Environment of the Impinged Achilles Tendon. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2401015. [PMID: 38966889 DOI: 10.1002/smll.202401015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 06/13/2024] [Indexed: 07/06/2024]
Abstract
Although tendon predominantly experiences longitudinal tensile forces, transverse forces due to impingement from bone are implicated in both physiological and pathophysiological processes. However, prior studies have not characterized the micromechanical strain environment in the context of tendon impingement. To address this knowledge gap, mouse hindlimb explants are imaged on a multiphoton microscope, and image stacks of the same population of tendon cells are obtained in the Achilles tendon before and after dorsiflexion-induced impingement by the heel bone. Based on the acquired images, multiaxial strains are measured at the extracellular matrix (ECM), pericellular matrix (PCM), and cell scales. Impingement generated substantial transverse compression at the matrix-scale, which led to longitudinal stretching of cells, increased cell aspect ratio, and enormous volumetric compression of the PCM. These experimental results are corroborated by a finite element model, which further demonstrated that impingement produces high cell surface stresses and strains that greatly exceed those brought about by longitudinal tension. Moreover, in both experiments and simulations, impingement-generated microscale stresses and strains are highly dependent on initial cell-cell gap spacing. Identifying factors that influence the microscale strain environment generated by impingement could contribute to a more mechanistic understanding of impingement-induced tendinopathies.
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Affiliation(s)
- Keshia E Mora
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Center for Musculoskeletal Research, Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, NY, 14642, USA
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Samuel J Mlawer
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Alayna E Loiselle
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Center for Musculoskeletal Research, Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Mark R Buckley
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Center for Musculoskeletal Research, Department of Orthopaedics and Rehabilitation, University of Rochester Medical Center, Rochester, NY, 14642, USA
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2
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Pancheri NM, Ellingson AJ, Marchus CR, Durgesh V, Verhage T, Yensen N, Schiele NR. Lysyl Oxidase Production by Murine C3H10T1/2 Mesenchymal Stem Cells Is Increased by TGFβs and Differentially Modulated by Mechanical Stimuli. Stem Cells Dev 2024; 33:355-364. [PMID: 38770821 DOI: 10.1089/scd.2023.0295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024] Open
Abstract
Tendons are frequently injured and have limited regenerative capacity. This motivates tissue engineering efforts aimed at restoring tendon function through strategies to direct functional tendon formation. Generation of a crosslinked collagen matrix is paramount to forming mechanically functional tendon. However, it is unknown how lysyl oxidase (LOX), the primary mediator of enzymatic collagen crosslinking, is regulated by stem cells. This study investigates how multiple factors previously identified to promote tendon formation and healing (transforming growth factor [TGF]β1 and TGFβ2, mechanical stimuli, and hypoxia-inducible factor [HIF]-1α) regulate LOX production in the murine C3H10T1/2 mesenchymal stem cell (MSC) line. We hypothesized that TGFβ signaling promotes LOX activity in C3H10T1/2 MSCs, which is regulated by both mechanical stimuli and HIF-1α activation. TGFβ1 and TGFβ2 increased LOX levels as a function of concentration and time. Inhibiting the TGFβ type I receptor (TGFβRI) decreased TGFβ2-induced LOX production by C3H10T1/2 MSCs. Low (5 mPa) and high (150 mPa) magnitudes of fluid shear stress were applied to test impacts of mechanical stimuli, but without TGFβ2, loading alone did not alter LOX levels. Low loading (5 mPa) with TGFβ2 increased LOX at 7 days greater than TGFβ2 treatment alone. Neither HIF-1α knockdown (siRNA) nor activation (CoCl2) affected LOX levels. Ultimately, results suggest that TGFβ2 and appropriate loading magnitudes contribute to LOX production by C3H10T1/2 MSCs. Potential application of these findings includes treatment with TGFβ2 and appropriate mechanical stimuli to modulate LOX production by stem cells to ultimately control collagen matrix stiffening and support functional tendon formation.
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Affiliation(s)
- Nicholas M Pancheri
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Allison J Ellingson
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Colin R Marchus
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Vibhav Durgesh
- Department of Mechanical Engineering, University of Idaho, Moscow, Idaho, USA
| | - Tabitha Verhage
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Nicholas Yensen
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
| | - Nathan R Schiele
- Department of Chemical & Biological Engineering, University of Idaho, Moscow, Idaho, USA
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3
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Lake SP, Snedeker JG, Wang VM, Awad H, Screen HRC, Thomopoulos S. Guidelines for ex vivo mechanical testing of tendon. J Orthop Res 2023; 41:2105-2113. [PMID: 37312619 PMCID: PMC10528429 DOI: 10.1002/jor.25647] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 05/27/2023] [Accepted: 05/30/2023] [Indexed: 06/15/2023]
Abstract
Tendons are critical for the biomechanical function of joints. Tendons connect muscles to bones and allow for the transmission of muscle forces to facilitate joint motion. Therefore, characterizing the tensile mechanical properties of tendons is important for the assessment of functional tendon health and efficacy of treatments for acute and chronic injuries. In this guidelines paper, we review methodological considerations, testing protocols, and key outcome measures for mechanical testing of tendons. The goal of the paper is to present a simple set of guidelines to the nonexpert seeking to perform tendon mechanical tests. The suggested approaches provide rigorous and consistent methodologies for standardized biomechanical characterization of tendon and reporting requirements across laboratories.
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Affiliation(s)
- Spencer P. Lake
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | - Vincent M. Wang
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia, USA
| | - Hani Awad
- Department of Orthopaedics, Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA
| | - Hazel R. C. Screen
- School of Engineering & Materials Science, Queen Mary University of London, London, UK
| | - Stavros Thomopoulos
- Department of Orthopaedic Surgery, Department of Biomedical Engineering, Columbia University, New York, New York, USA
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4
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Ostadi Moghaddam A, Arshee MR, Lin Z, Sivaguru M, Phillips H, McFarlin BL, Toussaint KC, Wagoner Johnson AJ. An indentation-based framework for probing the glycosaminoglycan-mediated interactions of collagen fibrils. J Mech Behav Biomed Mater 2023; 140:105726. [PMID: 36827935 PMCID: PMC10061372 DOI: 10.1016/j.jmbbm.2023.105726] [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: 11/15/2022] [Revised: 02/01/2023] [Accepted: 02/11/2023] [Indexed: 02/17/2023]
Abstract
Microscale deformation processes, such as reorientation, buckling, and sliding of collagen fibrils, determine the mechanical behavior and function of collagenous tissue. While changes in the structure and composition of tendon have been extensively studied, the deformation mechanisms that modulate the interaction of extracellular matrix (ECM) constituents are not well understood, partly due to the lack of appropriate techniques to probe the behavior. In particular, the role of glycosaminoglycans (GAGs) in modulating collagen fibril interactions has remained controversial. Some studies suggest that GAGs act as crosslinkers between the collagen fibrils, while others have not found such evidence and postulate that GAGs have other functions. Here, we introduce a new framework, relying on orientation-dependent indentation behavior of tissue and computational modeling, to evaluate the shear-mediated function of GAGs in modulating the collagen fibril interactions at a length scale more relevant to fibrils compared to bulk tests. Specifically, we use chondroitinase ABC to enzymatically deplete the GAGs in tendon; measure the orientation-dependent indentation response in transverse and longitudinal orientations; and infer the microscale deformation mechanisms and function of GAGs from a microstructural computational model and a modified shear-lag model. We validate the modeling approach experimentally and show that GAGs facilitate collagen fibril sliding with minimal crosslinking function. We suggest that the molecular reconfiguration of GAGs is a potential mechanism for their microscale, strain-dependent viscoelastic behavior. This study reveals the mechanisms that control the orientation-dependent indentation response by affecting the shear deformation and provides new insights into the mechanical function of GAGs and collagen crosslinkers in collagenous tissue.
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Affiliation(s)
- A Ostadi Moghaddam
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - M R Arshee
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Z Lin
- School of Engineering, Brown University, Providence, RI, 02912, USA
| | - M Sivaguru
- Flow Cytometry and Microscopy to Omics, Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Champaign, IL, 61820, USA
| | - H Phillips
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - B L McFarlin
- Department of Women, Children and Family Health Science, University of Illinois College of Nursing, Chicago, IL, 60612, USA
| | - K C Toussaint
- School of Engineering, Brown University, Providence, RI, 02912, USA
| | - A J Wagoner Johnson
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA; Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Champaign, IL, 61820, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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5
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Solis-Cordova J, Edwards JH, Fermor HL, Riches P, Brockett CL, Herbert A. Characterisation of native and decellularised porcine tendon under tension and compression: A closer look at glycosaminoglycan contribution to tendon mechanics. J Mech Behav Biomed Mater 2023; 139:105671. [PMID: 36682172 DOI: 10.1016/j.jmbbm.2023.105671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/17/2022] [Accepted: 01/07/2023] [Indexed: 01/13/2023]
Abstract
Decellularised porcine superflexor tendon (pSFT) has been characterised as a suitable scaffold for anterior cruciate ligament replacement, with dimensions similar to hamstring tendon autograft. However, decellularisation of tissues may reduce or damage extracellular matrix components, leading to undesirable biomechanical changes at a whole tissue scale. Although the role of collagen in tendons is well established, the mechanical contribution of glycosaminoglycans (GAGs) is less evident and could be altered by the decellularisation process. In this study, the contribution of GAGs to the tensile and compressive mechanical properties of pSFT was determined and whether decellularisation affected these properties by reducing GAG content or functionality. PSFTs were either enzymatically treated using chondroitinase ABC to remove GAGs or decellularised using previously established methods. Native, GAG-depleted and decellularised pSFT groups were then subjected to quantitative assays and biomechanical characterisation. In tension, specimens underwent stress relaxation and strength testing. In compression, specimens underwent confined compression testing. The GAG-depleted group was found to have circa 86% reduction of GAG content compared to native and decellularised groups. There was no significant difference in GAG content between native (3.75 ± 0.58 μg/mg) and decellularised (3.40 ± 0.37 μg/mg) groups. Stress relaxation testing discovered the time-independent and time-dependent relaxation moduli of the decellularised group were reduced ≥50% compared to native and GAG-depleted groups. However, viscoelastic behaviour of native and GAG-depleted groups resulted similar. Strength testing discovered no differences between native and GAG-depleted group's properties, albeit a reduction ∼20% for decellularised specimens' linear modulus and tensile strength compared to native tissue. In compression testing, the aggregate modulus was found to be circa 74% lower in the GAG-depleted group than the native and decellularised groups, while the zero-strain permeability was significantly higher in the GAG-depleted group (0.86 ± 0.65 mm4/N) than the decellularised group (0.03 ± 0.04 mm4/N). The results indicate that GAGs may significantly contribute to the mechanical properties of pSFT in compression, but not in tension. Furthermore, the content and function of GAGs in pSFTs are unaffected by decellularisation and the mechanical properties of the tissue remain comparable to native tissue.
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Affiliation(s)
- Jacqueline Solis-Cordova
- Institute of Medical and Biological Engineering, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom; Institute of Medical and Biological Engineering, School of Mechanical Engineering, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom.
| | - Jennifer H Edwards
- Institute of Medical and Biological Engineering, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Hazel L Fermor
- Institute of Medical and Biological Engineering, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Philip Riches
- Department of Biomedical Engineering, Faculty of Engineering, University of Strathclyde, Wolfson Centre, Glasgow, United Kingdom
| | - Claire L Brockett
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom
| | - Anthony Herbert
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom
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6
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Ostadi Moghaddam A, Arshee MR, Lin Z, Sivaguru M, Phillips H, McFarlin BL, Toussaint KC, Wagoner Johnson AJ. Orientation-dependent indentation reveals the crosslink-mediated deformation mechanisms of collagen fibrils. Acta Biomater 2023; 158:347-357. [PMID: 36638936 PMCID: PMC10039649 DOI: 10.1016/j.actbio.2023.01.005] [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: 09/20/2022] [Revised: 12/18/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
The spatial arrangement and interactions of the extracellular matrix (ECM) components control the mechanical behavior of tissue at multiple length scales. Changes in microscale deformation mechanisms affect tissue function and are often hallmarks of remodeling and disease. Despite their importance, the deformation mechanisms that modulate the mechanical behavior of collagenous tissue, particularly in indentation and compression modes of deformation, remain poorly understood. Here, we develop an integrated computational and experimental approach to investigate the deformation mechanisms of collagenous tissue at the microscale. While the complex deformation arising from indentation with a spherical probe is often considered a pitfall rather than an opportunity, we leverage this orientation-dependent deformation to examine the shear-regulated interactions of collagen fibrils and the role of crosslinks in modulating these interactions. We specifically examine tendon and cervix, two tissues rich in collagen with quite different microstructures and mechanical functions. We find that interacting, crosslinked collagen fibrils resist microscale longitudinal compressive forces, while widely used constitutive models fail to capture this behavior. The reorientation of collagen fibrils tunes the compressive stiffness of complex tissues like cervix. This study offers new insights into the mechanical behavior of collagen fibrils during indentation, and more generally, under longitudinal compressive forces, and illustrates the mechanisms that contribute to the experimentally observed orientation-dependent mechanical behavior. STATEMENT OF SIGNIFICANCE: Remodeling and disease can affect the deformation and interaction of tissue constituents, and thus mechanical function of tissue. Yet, the microscale deformation mechanisms are not well characterized in many tissues. Here, we develop a combined experimental-computational approach to infer the microscale deformation mechanisms of collagenous tissues with very different functions: tendon and cervix. Results show that collagen fibrils resist microscale forces along their length, though widely-used constitutive models do not account for this mechanism. This deformation process partially modulates the compressive stiffness of complex tissues such as cervix. Computational modeling shows that crosslink-mediated shear deformations are central to this unexpected behavior. This study offers new insights into the deformation mechanisms of collagenous tissue and the function of collagen crosslinkers.
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Affiliation(s)
- A Ostadi Moghaddam
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - M R Arshee
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Z Lin
- School of Engineering, Brown University, Providence, RI 02912, USA
| | - M Sivaguru
- Flow Cytometry and Microscopy to Omics, Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA
| | - H Phillips
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - B L McFarlin
- Department of Women, Children and Family Health Science, University of Illinois College of Nursing, Chicago, IL 60612, USA
| | - K C Toussaint
- School of Engineering, Brown University, Providence, RI 02912, USA
| | - A J Wagoner Johnson
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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7
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Voce GT, Michalek AJ. Fluorescent labeling with 5-DTAF reduces collagen fiber uncrimping in loaded tendons. J Mech Behav Biomed Mater 2023; 138:105646. [PMID: 36580857 DOI: 10.1016/j.jmbbm.2022.105646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/14/2022] [Accepted: 12/26/2022] [Indexed: 12/28/2022]
Abstract
A fluorescent dye commonly used to image tissues under load (5-DTAF) has previously been shown to stiffen tendons. This study hypothesized that 5-DTAF staining stiffens tendons through reduced fiber sliding, altering the rate at which crimped collagen fibers straighten under load. This was tested by using reflected cross-polarized light microscopy to measure fiber crimp period of cervine extensor digitorum longus tendon specimens under axial load. Specimens were treated with either phosphate buffered saline (negative control), genipin (positive control), or 5-DTAF. In saline treated specimens, crimp period (relative to unstretched) increased at approximately 2.5 times the applied axial strain, indicating substantial fiber sliding. In both 5-DTAF and genipin treated specimens, this ratio was reduced to 1:1, indicating no fiber sliding. These results add further evidence that care should be taken when using 5-DTAF to stain tissue for studying microscale deformations in tissues.
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Affiliation(s)
- Gianna T Voce
- Department of Computer Science, Clarkson University, Potsdam, NY, USA
| | - Arthur J Michalek
- Department of Mechanical & Aerospace Engineering, Clarkson University, Potsdam, NY, USA.
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8
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Vaidya R, Lake SP, Zellers JA. Effect of Diabetes on Tendon Structure and Function: Not Limited to Collagen Crosslinking. J Diabetes Sci Technol 2023; 17:89-98. [PMID: 35652696 PMCID: PMC9846394 DOI: 10.1177/19322968221100842] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Diabetes mellitus (DM) is associated with musculoskeletal complications-including tendon dysfunction and injury. Patients with DM show altered foot and ankle mechanics that have been attributed to tendon dysfunction as well as impaired recovery post-tendon injury. Despite the problem of DM-related tendon complications, treatment guidelines specific to this population of individuals are lacking. DM impairs tendon structure, function, and healing capacity in tendons throughout the body, but the Achilles tendon is of particular concern and most studied in the diabetic foot. At macroscopic levels, asymptomatic, diabetic Achilles tendons may show morphological abnormalities such as thickening, collagen disorganization, and/or calcific changes at the tendon enthesis. At smaller length scales, DM affects collagen sliding and discrete plasticity due to glycation of collagen. However, how these alterations translate to mechanical deficits observed at larger length scales is an area of continued investigation. In addition to dysfunction of the extracellular matrix, tendon cells such as tenocytes and tendon stem/progenitor cells show significant abnormalities in proliferation, apoptosis, and remodeling capacity in the presence of hyperglycemia and advanced glycation end-products, thus contributing to the disruption of tendon homeostasis and healing. Improving our understanding of the effects of DM on tendons-from molecular pathways to patients-will progress toward targeted therapies in this group at high risk of foot and ankle morbidity.
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Affiliation(s)
- Rachana Vaidya
- Washington University School of
Medicine, St. Louis, MO, USA
| | | | - Jennifer A. Zellers
- Washington University School of
Medicine, St. Louis, MO, USA
- Jennifer A. Zellers, PT, DPT, PhD,
Washington University School of Medicine, 4444 Forest Park Ave., Suite
1101, St. Louis, MO 63108, USA.
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9
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Fang F, Xiao Y, Zelzer E, Leong KW, Thomopoulos S. A mineralizing pool of Gli1-expressing progenitors builds the tendon enthesis and demonstrates therapeutic potential. Cell Stem Cell 2022; 29:1669-1684.e6. [PMID: 36459968 PMCID: PMC10422080 DOI: 10.1016/j.stem.2022.11.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/27/2022] [Accepted: 11/08/2022] [Indexed: 12/03/2022]
Abstract
The enthesis, a fibrocartilaginous transition between tendon and bone, is necessary for force transfer from muscle to bone to produce joint motion. The enthesis is prone to injury due to mechanical demands, and it cannot regenerate. A better understanding of how the enthesis develops will lead to more effective therapies to prevent pathology and promote regeneration. Here, we used single-cell RNA sequencing to define the developmental transcriptome of the mouse entheses over postnatal stages. Six resident cell types, including enthesis progenitors and mineralizing chondrocytes, were identified along with their transcription factor regulons and temporal regulation. Following the prior discovery of the necessity of Gli1-lineage cells for mouse enthesis development and healing, we then examined their transcriptomes at single-cell resolution and demonstrated clonogenicity and multipotency of the Gli1-expressing progenitors. Transplantation of Gli1-lineage cells to mouse enthesis injuries improved healing, demonstrating their therapeutic potential for enthesis regeneration.
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Affiliation(s)
- Fei Fang
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA; Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Yang Xiao
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Elazar Zelzer
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Kam W Leong
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
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10
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Eisner LE, Rosario R, Andarawis-Puri N, Arruda EM. The Role of the Non-Collagenous Extracellular Matrix in Tendon and Ligament Mechanical Behavior: A Review. J Biomech Eng 2022; 144:1128818. [PMID: 34802057 PMCID: PMC8719050 DOI: 10.1115/1.4053086] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Indexed: 12/26/2022]
Abstract
Tendon is a connective tissue that transmits loads from muscle to bone, while ligament is a similar tissue that stabilizes joint articulation by connecting bone to bone. The 70-90% of tendon and ligament's extracellular matrix (ECM) is composed of a hierarchical collagen structure that provides resistance to deformation primarily in the fiber direction, and the remaining fraction consists of a variety of non-collagenous proteins, proteoglycans, and glycosaminoglycans (GAGs) whose mechanical roles are not well characterized. ECM constituents such as elastin, the proteoglycans decorin, biglycan, lumican, fibromodulin, lubricin, and aggrecan and their associated GAGs, and cartilage oligomeric matrix protein (COMP) have been suggested to contribute to tendon and ligament's characteristic quasi-static and viscoelastic mechanical behavior in tension, shear, and compression. The purpose of this review is to summarize existing literature regarding the contribution of the non-collagenous ECM to tendon and ligament mechanics, and to highlight key gaps in knowledge that future studies may address. Using insights from theoretical mechanics and biology, we discuss the role of the non-collagenous ECM in quasi-static and viscoelastic tensile, compressive, and shear behavior in the fiber direction and orthogonal to the fiber direction. We also address the efficacy of tools that are commonly used to assess these relationships, including enzymatic degradation, mouse knockout models, and computational models. Further work in this field will foster a better understanding of tendon and ligament damage and healing as well as inform strategies for tissue repair and regeneration.
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Affiliation(s)
- Lainie E Eisner
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109; Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853
| | - Ryan Rosario
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Nelly Andarawis-Puri
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853
| | - Ellen M Arruda
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109; Professor Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109; Professor Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109
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11
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Eekhoff JD, Abraham JA, Schott HR, Solon LF, Ulloa GE, Zellers JA, Cannon PC, Lake SP. Fascicular elastin within tendon contributes to the magnitude and modulus gradient of the elastic stress response across tendon type and species. Acta Biomater 2022; 163:91-105. [PMID: 35306182 DOI: 10.1016/j.actbio.2022.03.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/07/2022] [Accepted: 03/10/2022] [Indexed: 11/19/2022]
Abstract
Elastin, the main component of elastic fibers, has been demonstrated to significantly influence tendon mechanics using both elastin degradation studies and elastinopathic mouse models. However, it remains unclear how prior results differ between species and functionally distinct tendons and, in particular, how results translate to human tendon. Differences in function between fascicular and interfascicular elastin are also yet to be fully elucidated. Therefore, this study evaluated the quantity, structure, and mechanical contribution of elastin in functionally distinct tendons across species. Tendons with an energy-storing function had slightly more elastin content than tendons with a positional function, and human tendon had at least twice the elastin content of other species. While distinctions in the organization of elastic fibers between fascicles and the interfascicular matrix were observed, differences in structural arrangement of the elastin network between species and tendon type were limited. Mechanical testing paired with enzyme-induced elastin degradation was used to evaluate the contribution of elastin to tendon mechanics. Across all tendons, elastin degradation affected the elastic stress response by decreasing stress values while increasing the modulus gradient of the stress-strain curve. Only the contributions of elastin to viscoelastic properties varied between tendon type and species, with human tendon and energy-storing tendon being more affected. These data suggest that fascicular elastic fibers contribute to the tensile mechanical response of tendon, likely by regulating collagen engagement under load. Results add to prior findings and provide evidence for a more mechanistic understanding of the role of elastic fibers in tendon. STATEMENT OF SIGNIFICANCE: Elastin has previously been shown to influence the mechanical properties of tendon, and degraded or abnormal elastin networks caused by aging or disease may contribute to pain and an increased risk of injury. However, prior work has not fully determined how elastin contributes differently to tendons with varying functional demands, as well as within distinct regions of tendon. This study determined the effects of elastin degradation on the tensile elastic and viscoelastic responses of tendons with varying functional demands, hierarchical structures, and elastin content. Moreover, volumetric imaging and protein quantification were used to thoroughly characterize the elastin network in each distinct tendon. The results presented herein can inform tendon-specific strategies to maintain or restore native properties in elastin-degraded tissue.
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Affiliation(s)
- Jeremy D Eekhoff
- Department of Biomedical Engineering, Washington University in St. Louis, 1 Brookings Drive, MSC: 1185-208-125, St. Louis, MO 63130, United States
| | - James A Abraham
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, United States
| | - Hayden R Schott
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, United States
| | - Lorenzo F Solon
- Department of Biology, Washington University in St. Louis, United States
| | - Gabriella E Ulloa
- Department of Mechanical Engineering, Massachusetts Institute of Technology, United States
| | - Jennifer A Zellers
- Department of Physical Therapy, Washington University in St. Louis School of Medicine, United States
| | - Paul C Cannon
- Department of Mathematics, Brigham Young University - Idaho, United States
| | - Spencer P Lake
- Department of Biomedical Engineering, Washington University in St. Louis, 1 Brookings Drive, MSC: 1185-208-125, St. Louis, MO 63130, United States; Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, United States; Department of Orthopaedic Surgery, Washington University in St. Louis School of Medicine, , United States.
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12
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Disney C, Mo J, Eckersley A, Bodey A, Hoyland J, Sherratt M, Pitsillides A, Lee P, Bay B. Regional variations in discrete collagen fibre mechanics within intact intervertebral disc resolved using synchrotron computed tomography and digital volume correlation. Acta Biomater 2022; 138:361-374. [PMID: 34644611 PMCID: PMC8904373 DOI: 10.1016/j.actbio.2021.10.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 10/01/2021] [Accepted: 10/06/2021] [Indexed: 01/14/2023]
Abstract
Many soft tissues, such as the intervertebral disc (IVD), have a hierarchical fibrous composite structure which suffers from regional damage. We hypothesise that these tissue regions have distinct, inherent fibre structure and structural response upon loading. Here we used synchrotron computed tomography (sCT) to resolve collagen fibre bundles (∼5μm width) in 3D throughout an intact native rat lumbar IVD under increasing compressive load. Using intact samples meant that tissue boundaries (such as endplate-disc or nucleus-annulus) and residual strain were preserved; this is vital for characterising both the inherent structure and structural changes upon loading in tissue regions functioning in a near-native environment. Nano-scale displacement measurements along >10,000 individual fibres were tracked, and fibre orientation, curvature and strain changes were compared between the posterior-lateral region and the anterior region. These methods can be widely applied to other soft tissues, to identify fibre structures which cause tissue regions to be more susceptible to injury and degeneration. Our results demonstrate for the first time that highly-localised changes in fibre orientation, curvature and strain indicate differences in regional strain transfer and mechanical function (e.g. tissue compliance). This included decreased fibre reorientation at higher loads, specific tissue morphology which reduced capacity for flexibility and high strain at the disc-endplate boundary. Statement of significance The analyses presented here are applicable to many collagenous soft tissues which suffer from regional damage. We aimed to investigate regional intervertebral disc (IVD) structural and functional differences by characterising collagen fibre architecture and linking specific fibre- and tissue-level deformation behaviours. Synchrotron CT provided the first demonstration of tracking discrete fibres in 3D within an intact IVD. Detailed analysis of regions was performed using over 200k points, spaced every 8 μm along 10k individual fibres. Such comprehensive structural characterisation is significant in informing future computational models. Morphological indicators of tissue compliance (change in fibre curvature and orientation) and fibre strain measurements revealed localised and regional differences in tissue behaviour.
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13
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Bramson MTK, Van Houten SK, Corr DT. Mechanobiology in Tendon, Ligament, and Skeletal Muscle Tissue Engineering. J Biomech Eng 2021; 143:070801. [PMID: 33537704 DOI: 10.1115/1.4050035] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Indexed: 12/28/2022]
Abstract
Tendon, ligament, and skeletal muscle are highly organized tissues that largely rely on a hierarchical collagenous matrix to withstand high tensile loads experienced in activities of daily life. This critical biomechanical role predisposes these tissues to injury, and current treatments fail to recapitulate the biomechanical function of native tissue. This has prompted researchers to pursue engineering functional tissue replacements, or dysfunction/disease/development models, by emulating in vivo stimuli within in vitro tissue engineering platforms-specifically mechanical stimulation, as well as active contraction in skeletal muscle. Mechanical loading is critical for matrix production and organization in the development, maturation, and maintenance of native tendon, ligament, and skeletal muscle, as well as their interfaces. Tissue engineers seek to harness these mechanobiological benefits using bioreactors to apply both static and dynamic mechanical stimulation to tissue constructs, and induce active contraction in engineered skeletal muscle. The vast majority of engineering approaches in these tissues are scaffold-based, providing interim structure and support to engineered constructs, and sufficient integrity to withstand mechanical loading. Alternatively, some recent studies have employed developmentally inspired scaffold-free techniques, relying on cellular self-assembly and matrix production to form tissue constructs. Whether utilizing a scaffold or not, incorporation of mechanobiological stimuli has been shown to improve the composition, structure, and biomechanical function of engineered tendon, ligament, and skeletal muscle. Together, these findings highlight the importance of mechanobiology and suggest how it can be leveraged to engineer these tissues and their interfaces, and to create functional multitissue constructs.
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Affiliation(s)
- Michael T K Bramson
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180
| | - Sarah K Van Houten
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180
| | - David T Corr
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180
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14
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Safa BN, Santare MH, Ethier CR, Elliott DM. Identifiability of tissue material parameters from uniaxial tests using multi-start optimization. Acta Biomater 2021; 123:197-207. [PMID: 33444797 PMCID: PMC8518191 DOI: 10.1016/j.actbio.2021.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 01/06/2021] [Accepted: 01/07/2021] [Indexed: 02/05/2023]
Abstract
Determining tissue biomechanical material properties from mechanical test data is frequently required in a variety of applications. However, the validity of the resulting constitutive model parameters is the subject of debate in the field. Parameter optimization in tissue mechanics often comes down to the "identifiability" or "uniqueness" of constitutive model parameters; however, despite advances in formulating complex constitutive relations and many classic and creative curve-fitting approaches, there is currently no accessible framework to study the identifiability of tissue material parameters. Our objective was to assess the identifiability of material parameters for established constitutive models of fiber-reinforced soft tissues, biomaterials, and tissue-engineered constructs and establish a generalizable procedure for other applications. To do so, we generated synthetic experimental data by simulating uniaxial tension and compression tests, commonly used in biomechanics. We then fit this data using a multi-start optimization technique based on the nonlinear least-squares method with multiple initial parameter guesses. We considered tendon and sclera as example tissues, using constitutive models that describe these fiber-reinforced tissues. We demonstrated that not all the model parameters of these constitutive models were identifiable from uniaxial mechanical tests, despite achieving virtually identical fits to the stress-stretch response. We further show that when the lateral strain was considered as an additional fitting criterion, more parameters are identifiable, but some remain unidentified. This work provides a practical approach for addressing parameter identifiability in tissue mechanics.
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Affiliation(s)
- Babak N Safa
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA, USA; Department of Biomedical Engineering, University of Delaware, Newark, DE, USA; Department of Mechanical Engineering, University of Delaware, Newark, DE, USA.
| | - Michael H Santare
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA; Department of Mechanical Engineering, University of Delaware, Newark, DE, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA, USA
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA
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15
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Eekhoff JD, Steenbock H, Berke IM, Brinckmann J, Yanagisawa H, Wagenseil JE, Lake SP. Dysregulated assembly of elastic fibers in fibulin-5 knockout mice results in a tendon-specific increase in elastic modulus. J Mech Behav Biomed Mater 2021; 113:104134. [PMID: 33045519 PMCID: PMC8146012 DOI: 10.1016/j.jmbbm.2020.104134] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/29/2020] [Accepted: 10/04/2020] [Indexed: 12/15/2022]
Abstract
Elastic fiber assembly is coordinated in part by fibulin-5, a matricellular protein. When fibulin-5 is not available to guide elastogenesis, elastin forms into disconnected globules instead of the dense elastic fiber core found in healthy tissues. Despite the growing evidence for a significant role of elastic fibers in tendon mechanics and the clinical relevance to cutis laxa, a human disease which can be caused by a mutation in the gene encoding fibulin-5, it is unknown how malformed elastic fibers affect tendon function. Therefore, this study investigated the effects of dysregulated elastic fiber assembly in tendons from fibulin-5 knockout mice in comparison to wild-type controls. Due to evidence for a more prominent role of elastic fibers in tendons with higher functional demands, both the energy-storing Achilles tendon and the more positional tibialis anterior tendon were evaluated. The linear modulus of knockout Achilles tendons was increased compared to controls, yet there was no discernible change in mechanical properties of the tibialis anterior tendon across genotypes. Transmission electron microscopy confirmed the presence of malformed elastic fibers in knockout tendons while no other changes to tendon composition or structure were found. The mechanism behind the increase in linear modulus in fibulin-5 knockout Achilles tendons may be greater collagen engagement due to decreased regulation of strain-induced structural reorganization. These findings support the theory of a significant, functionally distinct role of elastic fibers in tendon mechanics.
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Affiliation(s)
- Jeremy D Eekhoff
- Department of Biomedical Engineering, Washington University in St. Louis, USA
| | - Heiko Steenbock
- Institute of Virology and Cell Biology, University of Lübeck, Germany
| | - Ian M Berke
- Department of Biomedical Engineering, Washington University in St. Louis, USA
| | - Jürgen Brinckmann
- Institute of Virology and Cell Biology, University of Lübeck, Germany; Department of Dermatology, University of Lübeck, Germany
| | - Hiromi Yanagisawa
- Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance, University of Tsukuba, Japan
| | - Jessica E Wagenseil
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, USA
| | - Spencer P Lake
- Department of Biomedical Engineering, Washington University in St. Louis, USA; Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, USA; Department of Orthopaedic Surgery, Washington University in St. Louis, USA.
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16
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Fang F, Schwartz AG, Moore ER, Sup ME, Thomopoulos S. Primary cilia as the nexus of biophysical and hedgehog signaling at the tendon enthesis. SCIENCE ADVANCES 2020; 6:6/44/eabc1799. [PMID: 33127677 PMCID: PMC7608799 DOI: 10.1126/sciadv.abc1799] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 09/17/2020] [Indexed: 05/10/2023]
Abstract
The tendon enthesis is a fibrocartilaginous tissue critical for transfer of muscle forces to bone. Enthesis pathologies are common, and surgical repair of tendon to bone is plagued by high failure rates. At the root of these failures is a gap in knowledge of how the tendon enthesis is formed and maintained. We tested the hypothesis that the primary cilium is a hub for transducing biophysical and hedgehog (Hh) signals to regulate tendon enthesis formation and adaptation to loading. Primary cilia were necessary for enthesis development, and cilia assembly was coincident with Hh signaling and enthesis mineralization. Cilia responded inversely to loading; increased loading led to decreased cilia and decreased loading led to increased cilia. Enthesis responses to loading were dependent on Hh signaling through cilia. Results imply a role for tendon enthesis primary cilia as mechanical responders and Hh signal transducers, providing a therapeutic target for tendon enthesis pathologies.
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Affiliation(s)
- Fei Fang
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA
| | - Andrea G Schwartz
- Department of Orthopedic Surgery, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Emily R Moore
- School of Dental Medicine, Harvard University, Cambridge, MA, 02138, USA
| | - McKenzie E Sup
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY, 10032, USA.
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
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17
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Terzi A, Gallo N, Bettini S, Sibillano T, Altamura D, Madaghiele M, De Caro L, Valli L, Salvatore L, Sannino A, Giannini C. Sub‐ and Supramolecular X‐Ray Characterization of Engineered Tissues from Equine Tendon, Bovine Dermis, and Fish Skin Type‐I Collagen. Macromol Biosci 2020; 20:e2000017. [DOI: 10.1002/mabi.202000017] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 01/23/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Alberta Terzi
- Institute of Crystallography (IC)National Research Council Bari 70126 Italy
| | - Nunzia Gallo
- Department of Engineering for InnovationUniversity of Salento Lecce 73100 Italy
| | - Simona Bettini
- Department of Engineering for InnovationUniversity of Salento Lecce 73100 Italy
| | - Teresa Sibillano
- Institute of Crystallography (IC)National Research Council Bari 70126 Italy
| | - Davide Altamura
- Institute of Crystallography (IC)National Research Council Bari 70126 Italy
| | - Marta Madaghiele
- Department of Engineering for InnovationUniversity of Salento Lecce 73100 Italy
| | - Liberato De Caro
- Institute of Crystallography (IC)National Research Council Bari 70126 Italy
| | - Ludovico Valli
- Department of Biological and Environmental Sciences and TechnologiesUniversity of Salento Lecce 73100 Italy
| | - Luca Salvatore
- Department of Engineering for InnovationUniversity of Salento Lecce 73100 Italy
| | - Alessandro Sannino
- Department of Engineering for InnovationUniversity of Salento Lecce 73100 Italy
| | - Cinzia Giannini
- Institute of Crystallography (IC)National Research Council Bari 70126 Italy
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18
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Synchrotron tomography of intervertebral disc deformation quantified by digital volume correlation reveals microstructural influence on strain patterns. Acta Biomater 2019; 92:290-304. [PMID: 31082569 DOI: 10.1016/j.actbio.2019.05.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 05/01/2019] [Accepted: 05/07/2019] [Indexed: 11/22/2022]
Abstract
The intervertebral disc (IVD) has a complex and multiscale extracellular matrix structure which provides unique mechanical properties to withstand physiological loading. Low back pain has been linked to degeneration of the disc but reparative treatments are not currently available. Characterising the disc's 3D microstructure and its response in a physiologically relevant loading environment is required to improve understanding of degeneration and to develop new reparative treatments. In this study, techniques for imaging the native IVD, measuring internal deformation and mapping volumetric strain were applied to an in situ compressed ex vivo rat lumbar spine segment. Synchrotron X-ray micro-tomography (synchrotron CT) was used to resolve IVD structures at microscale resolution. These image data enabled 3D quantification of collagen bundle orientation and measurement of local displacement in the annulus fibrosus between sequential scans using digital volume correlation (DVC). The volumetric strain mapped from synchrotron CT provided a detailed insight into the micromechanics of native IVD tissue. The DVC findings showed that there was no slipping at lamella boundaries, and local strain patterns were of a similar distribution to the previously reported elastic network with some heterogeneous areas and maximum strain direction aligned with bundle orientation, suggesting bundle stretching and sliding. This method has the potential to bridge the gap between measures of macro-mechanical properties and the local 3D micro-mechanical environment experienced by cells. This is the first evaluation of strain at the micro scale level in the intact IVD and provides a quantitative framework for future IVD degeneration mechanics studies and testing of tissue engineered IVD replacements. STATEMENT OF SIGNIFICANCE: Synchrotron in-line phase contrast X-ray tomography provided the first visualisation of native intact intervertebral disc microstructural deformation in 3D. For two annulus fibrosus volumes of interest, collagen bundle orientation was quantified and local displacement mapped as strain. Direct evidence of microstructural influence on strain patterns could be seen such as no slipping at lamellae boundaries and maximum strain direction aligned with collagen bundle orientation. Although disc elastic structures were not directly observed, the strain patterns had a similar distribution to the previously reported elastic network. This study presents technical advances and is a basis for future X-ray microscopy, structural quantification and digital volume correlation strain analysis of soft tissue.
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19
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Abstract
The hierarchical structure of tendon allows for attenuation of mechanical strain down decreasing length scales. While reorganization of collagen fibers accounts for microscale strain attenuation, cross-linking between collagen molecules contributes to deformation mechanisms at the fibrillar and molecular scales. Divalent and trivalent enzymatic cross-links form during the development of collagen fibrils through the enzymatic activity of lysyl oxidase (LOX). By establishing connections between telopeptidyl and triple-helical domains of adjacent molecules within collagen fibrils, these cross-links stiffen the fibrils by resisting intermolecular sliding. Ultimately, greater enzymatic cross-linking leads to less compliant and stronger tendon as a result of stiffer fibrils. In contrast, nonenzymatic cross-links such as glucosepane and pentosidine are not produced during development but slowly accumulate through glycation of collagen. Therefore, these cross-links are only expected to be present in significant quantities in advanced age, where there has been sufficient time for glycation to occur, and in diabetes, where the presence of more free sugar in the extracellular matrix increases the rate of glycation. Unlike enzymatic cross-links, current evidence suggests that nonenzymatic cross-links are at least partially isolated to the surface of collagen fibers. As a result, glycation has been proposed to primarily impact tendon mechanics by altering molecular interactions at the fiber interface, thereby diminishing sliding between fibers. Thus, increased nonenzymatic cross-linking decreases microscale strain attenuation and the viscous response of tendon. In conclusion, enzymatic and nonenzymatic collagen cross-links have demonstrable and distinct effects on the mechanical properties of tendon across different length scales.
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Affiliation(s)
- Jeremy D Eekhoff
- a Department of Biomedical Engineering , Washington University in St. Louis , St. Louis , USA
| | - Fei Fang
- b Department of Orthopedic Surgery , Columbia University , New York , USA
| | - Spencer P Lake
- a Department of Biomedical Engineering , Washington University in St. Louis , St. Louis , USA.,c Department of Mechanical Engineering and Materials Science , Washington University in St. Louis , St. Louis , USA.,d Department of Orthopaedic Surgery , Washington University in St. Louis , St. Louis , USA
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20
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Eekhoff JD, Fang F, Kahan LG, Espinosa G, Cocciolone AJ, Wagenseil JE, Mecham RP, Lake SP. Functionally Distinct Tendons From Elastin Haploinsufficient Mice Exhibit Mild Stiffening and Tendon-Specific Structural Alteration. J Biomech Eng 2018; 139:2654667. [PMID: 28916838 DOI: 10.1115/1.4037932] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Indexed: 12/23/2022]
Abstract
Elastic fibers are present in low quantities in tendon, where they are located both within fascicles near tenocytes and more broadly in the interfascicular matrix (IFM). While elastic fibers have long been known to be significant in the mechanics of elastin-rich tissue (i.e., vasculature, skin, lungs), recent studies have suggested a mechanical role for elastic fibers in tendons that is dependent on specific tendon function. However, the exact contribution of elastin to properties of different types of tendons (e.g., positional, energy-storing) remains unknown. Therefore, this study purposed to evaluate the role of elastin in the mechanical properties and collagen alignment of functionally distinct supraspinatus tendons (SSTs) and Achilles tendons (ATs) from elastin haploinsufficient (HET) and wild type (WT) mice. Despite the significant decrease in elastin in HET tendons, a slight increase in linear stiffness of both tendons was the only significant mechanical effect of elastin haploinsufficiency. Additionally, there were significant changes in collagen nanostructure and subtle alteration to collagen alignment in the AT but not the SST. Hence, elastin may play only a minor role in tendon mechanical properties. Alternatively, larger changes to tendon mechanics may have been mitigated by developmental compensation of HET tendons and/or the role of elastic fibers may be less prominent in smaller mouse tendons compared to the larger bovine and human tendons evaluated in previous studies. Further research will be necessary to fully elucidate the influence of various elastic fiber components on structure-function relationships in functionally distinct tendons.
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Affiliation(s)
- Jeremy D Eekhoff
- Department of Biomedical Engineering, Washington University in St. Louis One Brookings Drive, St. Louis, MO 63130
| | - Fei Fang
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130
| | - Lindsey G Kahan
- Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130
| | - Gabriela Espinosa
- Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130
| | - Austin J Cocciolone
- Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130
| | - Jessica E Wagenseil
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130
| | - Robert P Mecham
- Department of Cell Biology and Physiology, Washington University in St. Louis, 660 South Euclid Avenue, St. Louis, MO 63110
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130.,Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130.,Department of Orthopaedic Surgery, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 e-mail:
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21
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Connizzo BK, Grodzinsky AJ. Multiscale Poroviscoelastic Compressive Properties of Mouse Supraspinatus Tendons Are Altered in Young and Aged Mice. J Biomech Eng 2018; 140:2666618. [PMID: 29238818 PMCID: PMC5816244 DOI: 10.1115/1.4038745] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 12/04/2017] [Indexed: 02/02/2023]
Abstract
Rotator cuff disorders are one of the most common causes of shoulder pain and disability in the aging population but, unfortunately, the etiology is still unknown. One factor thought to contribute to the progression of disease is the external compression of the rotator cuff tendons, which can be significantly increased by age-related changes such as muscle weakness and poor posture. The objective of this study was to investigate the baseline compressive response of tendon and determine how this response is altered during maturation and aging. We did this by characterizing the compressive mechanical, viscoelastic, and poroelastic properties of young, mature, and aged mouse supraspinatus tendons using macroscale indentation testing and nanoscale high-frequency AFM-based rheology testing. Using these multiscale techniques, we found that aged tendons were stiffer than their mature counterparts and that both young and aged tendons exhibited increased hydraulic permeability and energy dissipation. We hypothesize that regional and age-related variations in collagen morphology and organization are likely responsible for changes in the multiscale compressive response as these structural parameters may affect fluid flow. Importantly, these results suggest a role for age-related changes in the progression of tendon degeneration, and we hypothesize that decreased ability to resist compressive loading via fluid pressurization may result in damage to the extracellular matrix (ECM) and ultimately tendon degeneration. These studies provide insight into the regional multiscale compressive response of tendons and indicate that altered compressive properties in aging tendons may be a major contributor to overall tendon degeneration.
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Affiliation(s)
- Brianne K. Connizzo
- Department of Biological Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
| | - Alan J. Grodzinsky
- Department of Biological Engineering,Massachusetts Institute of Technology,
Cambridge, MA 02139;
Center for Biomedical Engineering,Massachusetts Institute of Technology,
Cambridge, MA 02139;
Department of Electrical Engineeringand Computer Science,
Massachusetts Institute of Technology,
Cambridge, MA 02139;
Department of Mechanical Engineering,Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail:
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22
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Disney CM, Lee PD, Hoyland JA, Sherratt MJ, Bay BK. A review of techniques for visualising soft tissue microstructure deformation and quantifying strain Ex Vivo. J Microsc 2018; 272:165-179. [PMID: 29655273 DOI: 10.1111/jmi.12701] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/08/2018] [Accepted: 03/16/2018] [Indexed: 12/16/2022]
Abstract
Many biological tissues have a complex hierarchical structure allowing them to function under demanding physiological loading conditions. Structural changes caused by ageing or disease can lead to loss of mechanical function. Therefore, it is necessary to characterise tissue structure to understand normal tissue function and the progression of disease. Ideally intact native tissues should be imaged in 3D and under physiological loading conditions. The current published in situ imaging methodologies demonstrate a compromise between imaging limitations and maintaining the samples native mechanical function. This review gives an overview of in situ imaging techniques used to visualise microstructural deformation of soft tissue, including three case studies of different tissues (tendon, intervertebral disc and artery). Some of the imaging techniques restricted analysis to observational mechanics or discrete strain measurement from invasive markers. Full-field local surface strain measurement has been achieved using digital image correlation. Volumetric strain fields have successfully been quantified from in situ X-ray microtomography (micro-CT) studies of bone using digital volume correlation but not in soft tissue due to low X-ray transmission contrast. With the latest developments in micro-CT showing in-line phase contrast capability to resolve native soft tissue microstructure, there is potential for future soft tissue mechanics research where 3D local strain can be quantified. These methods will provide information on the local 3D micromechanical environment experienced by cells in healthy, aged and diseased tissues. It is hoped that future applications of in situ imaging techniques will impact positively on the design and testing of potential tissue replacements or regenerative therapies. LAY DESCRIPTION: The soft tissues in our bodies, such as tendons, intervertebral discs and arteries, have evolved to have complicated structures which deform and bear load during normal function. Small changes in these structures can occur with age and disease which then leads to loss of function. Therefore, it is important to image tissue microstructure in 3D and under functional conditions. This paper gives an overview of imaging techniques used to record the deformation of soft tissue microstructures. Commonly there are compromises between obtaining the best imaging result and retaining the samples native structure and function. For example, invasive markers and dissecting samples damages the tissues natural structure, and staining or clearing (making the tissue more transparent) can distort tissue structure. Structural deformation has been quantified from 2D imaging techniques (digital image correlation) to create surface strain maps which help identify local tissue mechanics. When extended to 3D (digital volume correlation), deformation measurement has been limited to bone samples using X-ray micro-CT. Recently it has been possible to image the 3D structure of soft tissue using X-ray micro-CT meaning that there is potential for internal soft tissue mechanics to be mapped in 3D. Future application of micro-CT and digital volume correlation will be important for soft tissue mechanics studies particularly to understand normal function, progression of disease and in the design of tissue replacements.
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Affiliation(s)
- C M Disney
- Centre for Doctoral Training in Regenerative Medicine, University of Manchester, Manchester, U.K.,Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, Manchester, U.K
| | - P D Lee
- School of Materials, University of Manchester, Manchester, U.K
| | - J A Hoyland
- Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, Manchester, U.K.,NIHR Manchester Biomedical Research Centre, Manchester Academic Health Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, U.K
| | - M J Sherratt
- Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, Manchester, U.K
| | - B K Bay
- School of Mechanical, Industrial and Manufacturing Engineering, Oregon State University, Corvallis, Oregon, U.S.A
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Parreno J, Cheng C, Nowak RB, Fowler VM. The effects of mechanical strain on mouse eye lens capsule and cellular microstructure. Mol Biol Cell 2018; 29:1963-1974. [PMID: 30088796 PMCID: PMC6232967 DOI: 10.1091/mbc.e18-01-0035] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mouse eye lens was used as a model for multiscale transfer of loads. In the lens, compressive strain is distributed across specific lens tissue microstructures, including the extracellular capsule, as well as the epithelial and fiber cells. The removal of high loads resulted in complete recovery of most, but not all, microstructures. The understanding of multiscale load transfer within complex soft tissues is incomplete. The eye lens is ideal for multiscale mechanical studies because its principal function is to fine-focus light at different distances onto the retina via shape changes. The biomechanical function, resiliency, and intricate microstructure of the lens makes it an excellent nonconnective soft tissue model. We hypothesized that strain applied onto whole-lens tissue leads to deformation of specific microstructures and that this deformation is reversible following load removal. For this examination, mouse lenses were compressed by sequential application of increasing load. Using confocal microscopy and quantitative image analysis, we determined that axial strain ≥10% reduces capsule thickness, expands epithelial cell area, and separates fiber cell tips at the anterior region. At the equatorial region, strain ≥6% increases fiber cell widths. The effects of strain on lens epithelial cell area, capsule thickness, and fiber cell widths are reversible following the release from strain. However, the separation of fiber cell tips is irreversible at high loads. This irreversible separation between fiber cell tips leads to incomplete whole-lens resiliency. The lens is an accessible biomechanical model system that provides new insights on multiscale transfer of loads in soft tissues.
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Affiliation(s)
- Justin Parreno
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Catherine Cheng
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Roberta B Nowak
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Velia M Fowler
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
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Biological connective tissues exhibit viscoelastic and poroelastic behavior at different frequency regimes: Application to tendon and skin biophysics. Acta Biomater 2018; 70:249-259. [PMID: 29425716 DOI: 10.1016/j.actbio.2018.01.041] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 01/28/2018] [Accepted: 01/29/2018] [Indexed: 10/18/2022]
Abstract
In this study, a poroviscoelastic finite element model (FEM) was developed and used in conjunction with an AFM-based wide-bandwidth nanorheology system to predict the frequency-dependent mechanical behavior of tendon and dermis subjected to compression via nanoindentation. The aim was to distinguish between loading rates that are dominated by either poroelasticity, viscoelasticity, or the superposition of these processes. Using spherical probe tips having different radii, the force and tip displacement were measured and the magnitude, E∗, and phase angle, ϕ, of the dynamic complex modulus were evaluated for mouse supraspinatus tendon and mouse dermis. The peak frequencies of the phase angle were associated with the characteristic time constants of poroelastic and viscoelastic material behavior. The developed FE model could predict the separate poroelastic and viscoelastic responses of these soft tissues over a 4 decade frequency range, showing good agreement with experimental results. We observed that poroelasticity was the dominant energy dissipation mechanism for mouse dermis and supraspinatus tendon at higher indentation frequencies (102 to 104 Hz) whereas viscoelasticity was typically dominant at lower frequencies (<102 Hz). These findings show the underlying mechanical behavior of biological connective tissues and give insight into the role played by these different energy dissipation mechanisms in governing the function of these tissues at nanoscale. STATEMENT OF SIGNIFICANCE Soft biological tissues exhibit complex, load- and time-dependent mechanical behavior. Evaluating their mechanical behavior requires sophisticated experimental tools and numerical models that can capture the fundamental mechanisms governing tissue function. Using an Atomic-force-microscopy-based rheology system and finite element models, the roles of the two most dominant time-dependent mechanisms (poroelasticity and viscoelasticity) that govern the dynamic loading behavior of mouse skin and tendon have been investigated. FE models were able to predict and quantify the contribution of each mechanism to the overall dynamic response and confirming the presence of these two distinct mechanisms in the mechanical response. Overall, these results provide novel insight into the viscoelastic and poroelastic properties of mouse skin and tendon and promote better understanding of the underlying origins of each mechanism.
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Fang F, Lake SP. Multiscale Mechanical Evaluation of Human Supraspinatus Tendon Under Shear Loading After Glycosaminoglycan Reduction. J Biomech Eng 2018; 139:2625661. [PMID: 28462418 DOI: 10.1115/1.4036602] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Indexed: 12/15/2022]
Abstract
Proteoglycans (PGs) are broadly distributed within many soft tissues and, among other roles, often contribute to mechanical properties. Although PGs, consisting of a core protein and glycosaminoglycan (GAG) sidechains, were once hypothesized to regulate stress/strain transfer between collagen fibrils and help support load in tendon, several studies have reported no changes to tensile mechanics after GAG depletion. Since GAGs are known to help sustain nontensile loading in other tissues, we hypothesized that GAGs might help support shear loading in human supraspinatus tendon (SST), a commonly injured tendon which functions in a complex multiaxial loading environment. Therefore, the objective of this study was to determine whether GAGs contribute to the response of SST to shear, specifically in terms of multiscale mechanical properties and mechanisms of microscale matrix deformation. Results showed that chondroitinase ABC (ChABC) treatment digested GAGs in SST while not disrupting collagen fibers. Peak and equilibrium shear stresses decreased only slightly after ChABC treatment and were not significantly different from pretreatment values. Reduced stress ratios were computed and shown to be slightly greater after ChABC treatment compared to phosphate-buffered saline (PBS) incubation without enzyme, suggesting that these relatively small changes in stress values were not due strictly to tissue swelling. Microscale deformations were also not different after ChABC treatment. This study demonstrates that GAGs possibly play a minor role in contributing to the mechanical behavior of SST in shear, but are not a key tissue constituent to regulate shear mechanics.
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Affiliation(s)
- Fei Fang
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, MO 63130 e-mail:
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, MO 63130;Department of Biomedical Engineering, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, MO 63130;Department of Orthopaedic Surgery, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, MO 63130 e-mail:
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26
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Evaluation of microstructurally motivated constitutive models to describe age-dependent tendon healing. Biomech Model Mechanobiol 2017; 17:793-814. [PMID: 29234987 PMCID: PMC5948310 DOI: 10.1007/s10237-017-0993-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 11/30/2017] [Indexed: 12/27/2022]
Abstract
Tendon injuries are common to all ages. Injured tendons typically do not recover full functionality. The amount and organization of tendon constituents dictate their mechanical properties. The impact of changes in these constituents during (patho)physiologic processes (e.g., aging and healing) are not fully understood. Toward this end, microstructurally motivated strain energy functions (SEFs) offer insight into underlying mechanisms of age-dependent healing. Several SEFs have been adapted for tendon; however, most are phenomenological. Therefore, the aims of this study are: (1) evaluate the descriptive capability of SEFs in age-dependent murine patellar tendon healing and (2) identify a SEF for implementation in a growth and remodeling (G&R) model. To accomplish these aims, models were fitted to patellar tendon tensile data from multiple age groups and post-injury timepoints. Model sensitivity to parameters and the determinability of the parameters were assessed. A two-way analysis of variance was used to identify changes in parameters and the feasibility of implementing each model into a G&R model is discussed. The evaluated SEFs exhibited adequate descriptive capability. Parameter determinability and sensitivity analysis, however, highlighted the need for additional data to inform and validate the models to increase physiologic relevance and enable G&R model formulation to determine underlying mechanisms of age-dependent healing. This work, as a first, evaluated changes in tendon mechanical properties both as functions of age and injury in an age-dependent manner using microstructurally motivated models, highlights inherent dependencies between parameters of widely used hyperelastic models, and identified unique post-injury behavior by the aging group compared to the mature and aged groups.
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27
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Fang F, Lake SP. Experimental evaluation of multiscale tendon mechanics. J Orthop Res 2017; 35:1353-1365. [PMID: 27878999 DOI: 10.1002/jor.23488] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 11/16/2016] [Indexed: 02/04/2023]
Abstract
Tendon's primary function is a mechanical link between muscle and bone. The hierarchical structure of tendon and specific compositional constituents are believed to be critical for proper mechanical function. With increased appreciation for tendon importance and the development of various technological advances, this review paper summarizes recent experimental approaches that have been used to study multiscale tendon mechanics, includes an overview of studies that have evaluated the role of specific tissue constituents, and also proposes challenges/opportunities facing tendon study. Tendon has been demonstrated to have specific structural characteristics (e.g., multi-level hierarchy, crimp pattern, helix) and complex mechanical properties (e.g., non-linearity, anisotropy, viscoelasticity). Physical mechanisms including uncrimping, fiber sliding, and collagen reorganization have been shown to govern tendon mechanical responses under both static and dynamic loading. Several tendon constituents with relatively small quantities have been suggested to play a role in its mechanics, although some results are conflicting. Further research should be performed to understand the interplay and communication of tendon mechanical properties across levels of the hierarchical structure, and further show how each of these components contribute to tendon mechanics. The studies summarized and discussed in this review have helped elucidate important aspects of multiscale tendon mechanics, which is a prerequisite for analyzing stress/strain transfer between multiple scales and identifying key principles of mechanotransduction. This information could further facilitate interpreting the functional diversity of tendons from different species, different locations, and even different developmental stages, and then better understand and identify fundamental concepts related to tendon degeneration, disease, and healing. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1353-1365, 2017.
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Affiliation(s)
- Fei Fang
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, Missouri, 63130
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, Missouri, 63130.,Department of Biomedical Engineering, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, Missouri, 63130.,Department of Orthopaedic Surgery, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1185, St. Louis, Missouri, 63130
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28
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Goh KL, Holmes DF. Collagenous Extracellular Matrix Biomaterials for Tissue Engineering: Lessons from the Common Sea Urchin Tissue. Int J Mol Sci 2017; 18:ijms18050901. [PMID: 28441344 PMCID: PMC5454814 DOI: 10.3390/ijms18050901] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 04/05/2017] [Accepted: 04/11/2017] [Indexed: 12/21/2022] Open
Abstract
Scaffolds for tissue engineering application may be made from a collagenous extracellular matrix (ECM) of connective tissues because the ECM can mimic the functions of the target tissue. The primary sources of collagenous ECM material are calf skin and bone. However, these sources are associated with the risk of having bovine spongiform encephalopathy or transmissible spongiform encephalopathy. Alternative sources for collagenous ECM materials may be derived from livestock, e.g., pigs, and from marine animals, e.g., sea urchins. Collagenous ECM of the sea urchin possesses structural features and mechanical properties that are similar to those of mammalian ones. However, even more intriguing is that some tissues such as the ligamentous catch apparatus can exhibit mutability, namely rapid reversible changes in the tissue mechanical properties. These tissues are known as mutable collagenous tissues (MCTs). The mutability of these tissues has been the subject of on-going investigations, covering the biochemistry, structural biology and mechanical properties of the collagenous components. Recent studies point to a nerve-control system for regulating the ECM macromolecules that are involved in the sliding action of collagen fibrils in the MCT. This review discusses the key attributes of the structure and function of the ECM of the sea urchin ligaments that are related to the fibril-fibril sliding action-the focus is on the respective components within the hierarchical architecture of the tissue. In this context, structure refers to size, shape and separation distance of the ECM components while function is associated with mechanical properties e.g., strength and stiffness. For simplicity, the components that address the different length scale from the largest to the smallest are as follows: collagen fibres, collagen fibrils, interfibrillar matrix and collagen molecules. Application of recent theories of stress transfer and fracture mechanisms in fibre reinforced composites to a wide variety of collagen reinforcing (non-mutable) connective tissue, has allowed us to draw general conclusions concerning the mechanical response of the MCT at specific mechanical states, namely the stiff and complaint states. The intent of this review is to provide the latest insights, as well as identify technical challenges and opportunities, that may be useful for developing methods for effective mechanical support when adapting decellularised connective tissues from the sea urchin for tissue engineering or for the design of a synthetic analogue.
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Affiliation(s)
- Kheng Lim Goh
- Newcastle University Singapore, SIT Building at Nanyang Polytechnic, 172A Ang Mo Kio Avenue 8 #05-01, Singapore 567739, Singapore.
- Newcastle University, School of Mechanical & Systems Engineering, Stephenson Building, Claremont Road, Newcastle upon Tyne NE1 7RU, UK.
| | - David F Holmes
- Manchester University, Wellcome Trust Centre for Cell Matrix Research, B.3016 Michael Smith Building, Faculty of Life Sciences, Oxford Road, Manchester M13 9PT, UK.
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29
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Mehdizadeh A, Gardiner BS, Lavagnino M, Smith DW. Predicting tenocyte expression profiles and average molecular concentrations in Achilles tendon ECM from tissue strain and fiber damage. Biomech Model Mechanobiol 2017; 16:1329-1348. [DOI: 10.1007/s10237-017-0890-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 02/18/2017] [Indexed: 11/28/2022]
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30
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Kennedy KM, Bhaw-Luximon A, Jhurry D. Cell-matrix mechanical interaction in electrospun polymeric scaffolds for tissue engineering: Implications for scaffold design and performance. Acta Biomater 2017; 50:41-55. [PMID: 28011142 DOI: 10.1016/j.actbio.2016.12.034] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 11/10/2016] [Accepted: 12/15/2016] [Indexed: 12/24/2022]
Abstract
Engineered scaffolds produced by electrospinning of biodegradable polymers offer a 3D, nanofibrous environment with controllable structural, chemical, and mechanical properties that mimic the extracellular matrix of native tissues and have shown promise for a number of tissue engineering applications. The microscale mechanical interactions between cells and electrospun matrices drive cell behaviors including migration and differentiation that are critical to promote tissue regeneration. Recent developments in understanding these mechanical interactions in electrospun environments are reviewed, with emphasis on how fiber geometry and polymer structure impact on the local mechanical properties of scaffolds, how altering the micromechanics cues cell behaviors, and how, in turn, cellular and extrinsic forces exerted on the matrix mechanically remodel an electrospun scaffold throughout tissue development. Techniques used to measure and visualize these mechanical interactions are described. We provide a critical outlook on technological gaps that must be overcome to advance the ability to design, assess, and manipulate the mechanical environment in electrospun scaffolds toward constructs that may be successfully applied in tissue engineering and regenerative medicine. STATEMENT OF SIGNIFICANCE Tissue engineering requires design of scaffolds that interact with cells to promote tissue development. Electrospinning is a promising technique for fabricating fibrous, biomimetic scaffolds. Effects of electrospun matrix microstructure and biochemical properties on cell behavior have been extensively reviewed previously; here, we consider cell-matrix interaction from a mechanical perspective. Micromechanical properties as a driver of cell behavior has been well established in planar substrates, but more recently, many studies have provided new insights into mechanical interaction in fibrillar, electrospun environments. This review provides readers with an overview of how electrospun scaffold mechanics and cell behavior work in a dynamic feedback loop to drive tissue development, and discusses opportunities for improved design of mechanical environments that are conducive to tissue development.
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31
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Fang F, Lake SP. Multiscale mechanical integrity of human supraspinatus tendon in shear after elastin depletion. J Mech Behav Biomed Mater 2016; 63:443-455. [PMID: 27472764 DOI: 10.1016/j.jmbbm.2016.06.032] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 01/28/2023]
Abstract
Human supraspinatus tendon (SST) exhibits region-specific nonlinear mechanical properties under tension, which have been attributed to its complex multiaxial physiological loading environment. However, the mechanical response and underlying multiscale mechanism regulating SST behavior under other loading scenarios are poorly understood. Furthermore, little is known about the contribution of elastin to tendon mechanics. We hypothesized that (1) SST exhibits region-specific shear mechanical properties, (2) fiber sliding is the predominant mode of local matrix deformation in SST in shear, and (3) elastin helps maintain SST mechanical integrity by facilitating force transfer among collagen fibers. Through the use of biomechanical testing and multiphoton microscopy, we measured the multiscale mechanical behavior of human SST in shear before and after elastase treatment. Three distinct SST regions showed similar stresses and microscale deformation. Collagen fiber reorganization and sliding were physical mechanisms observed as the SST response to shear loading. Measures of microscale deformation were highly variable, likely due to a high degree of extracellular matrix heterogeneity. After elastase treatment, tendon exhibited significantly decreased stresses under shear loading, particularly at low strains. These results show that elastin contributes to tendon mechanics in shear, further complementing our understanding of multiscale tendon structure-function relationships.
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Affiliation(s)
- Fei Fang
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, United States
| | - Spencer P Lake
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, United States; Department of Biomedical Engineering, Washington University in St. Louis, United States; Department of Orthopaedic Surgery, Washington University in St. Louis, United States.
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32
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Han WM, Heo SJ, Driscoll TP, Delucca JF, McLeod CM, Smith LJ, Duncan RL, Mauck RL, Elliott DM. Microstructural heterogeneity directs micromechanics and mechanobiology in native and engineered fibrocartilage. NATURE MATERIALS 2016; 15:477-84. [PMID: 26726994 PMCID: PMC4805445 DOI: 10.1038/nmat4520] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 11/24/2015] [Indexed: 05/05/2023]
Abstract
Treatment strategies to address pathologies of fibrocartilaginous tissue are in part limited by an incomplete understanding of structure-function relationships in these load-bearing tissues. There is therefore a pressing need to develop micro-engineered tissue platforms that can recreate the highly inhomogeneous tissue microstructures that are known to influence mechanotransductive processes in normal and diseased tissue. Here, we report the quantification of proteoglycan-rich microdomains in developing, ageing and diseased fibrocartilaginous tissues, and the impact of these microdomains on endogenous cell responses to physiologic deformation within a native-tissue context. We also developed a method to generate heterogeneous tissue-engineered constructs (hetTECs) with non-fibrous proteoglycan-rich microdomains engineered into the fibrous structure, and show that these hetTECs match the microstructural, micromechanical and mechanobiological benchmarks of native tissue. Our tissue-engineered platform should facilitate the study of the mechanobiology of developing, homeostatic, degenerating and regenerating fibrous tissues.
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Affiliation(s)
- Woojin M Han
- Department of Bioengineering, University of Pennsylvania
| | - Su-Jin Heo
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - Tristan P Driscoll
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - John F Delucca
- Department of Biomedical Engineering, University of Delaware
| | - Claire M McLeod
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - Lachlan J Smith
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
- Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania
| | - Randall L Duncan
- Department of Biomedical Engineering, University of Delaware
- Department of Biological Sciences, University of Delaware
| | - Robert L Mauck
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
- Addresses for Correspondence: Dawn M. Elliott, Ph.D., Professor and Director of Biomedical Engineering, Department of Biomedical Engineering, University of Delaware, 161 Colburn Laboratory, Newark, DE 19716, Phone: (302) 831-4578, . Robert L. Mauck, Ph.D., Associate Professor of Orthopaedic Surgery and Bioengineering, Director, McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 36 Street and Hamilton Walk, Philadelphia, PA 19104, Phone: (215) 898-3294,
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware
- Addresses for Correspondence: Dawn M. Elliott, Ph.D., Professor and Director of Biomedical Engineering, Department of Biomedical Engineering, University of Delaware, 161 Colburn Laboratory, Newark, DE 19716, Phone: (302) 831-4578, . Robert L. Mauck, Ph.D., Associate Professor of Orthopaedic Surgery and Bioengineering, Director, McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 36 Street and Hamilton Walk, Philadelphia, PA 19104, Phone: (215) 898-3294,
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Frizziero A, Salamanna F, Della Bella E, Vittadini F, Gasparre G, Nicoli Aldini N, Masiero S, Fini M. The Role of Detraining in Tendon Mechanobiology. Front Aging Neurosci 2016; 8:43. [PMID: 26973517 PMCID: PMC4770795 DOI: 10.3389/fnagi.2016.00043] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 02/15/2016] [Indexed: 12/18/2022] Open
Abstract
Introduction: Several conditions such as training, aging, estrogen deficiency and drugs could affect the biological and anatomo-physiological characteristics of the tendon. Additionally, recent preclinical and clinical studies examined the effect of detraining on tendon, showing alterations in its structure and morphology and in tenocyte mechanobiology. However, few data evaluated the importance that cessation of training might have on tendon. Basically, we do not fully understand how tendons react to a phase of training followed by sudden detraining. Therefore, within this review, we summarize the studies where tendon detraining was examined. Materials and Methods: A descriptive systematic literature review was carried out by searching three databases (PubMed, Scopus and Web of Knowledge) on tendon detraining. Original articles in English from 2000 to 2015 were included. In addition, the search was extended to the reference lists of the selected articles. A public reference manager (www.mendeley.com) was adopted to remove duplicate articles. Results: An initial literature search yielded 134 references (www.pubmed.org: 53; www.scopus.com: 11; www.webofknowledge.com: 70). Fifteen publications were extracted based on the title for further analysis by two independent reviewers. Abstracts and complete articles were after that reviewed to evaluate if they met inclusion criteria. Conclusions: The revised literature comprised four clinical studies and an in vitro and three in vivo reports. Overall, the results showed that tendon structure and properties after detraining are compromised, with an alteration in the tissue structural organization and mechanical properties. Clinical studies usually showed a lesser extent of tendon alterations, probably because preclinical studies permit an in-depth evaluation of tendon modifications, which is hard to perform in human subjects. In conclusion, after a period of sudden detraining (e.g., after an injury), physical activity should be taken with caution, following a targeted rehabilitation program. However, further research should be performed to fully understand the effect of sudden detraining on tendons.
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Affiliation(s)
- Antonio Frizziero
- Department of Physical and Rehabilitation Medicine, University of Padua Padua, Italy
| | - Francesca Salamanna
- Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies, RIT Department, Rizzoli Orthopedic Institute Bologna, Italy
| | - Elena Della Bella
- Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic InstituteBologna, Italy; Department of Experimental, Diagnostic and Specialty Medicine, University of BolognaBologna, Italy
| | - Filippo Vittadini
- Department of Physical and Rehabilitation Medicine, University of Padua Padua, Italy
| | - Giuseppe Gasparre
- Department of Physical and Rehabilitation Medicine, University of Padua Padua, Italy
| | - Nicolò Nicoli Aldini
- Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies, RIT Department, Rizzoli Orthopedic InstituteBologna, Italy; Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic InstituteBologna, Italy
| | - Stefano Masiero
- Department of Physical and Rehabilitation Medicine, University of Padua Padua, Italy
| | - Milena Fini
- Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies, RIT Department, Rizzoli Orthopedic InstituteBologna, Italy; Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopedic InstituteBologna, Italy
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Abstract
Tendon exhibits anisotropic, inhomogeneous and viscoelastic mechanical properties that are determined by its complicated hierarchical structure and varying amounts/organization of different tissue constituents. Although extensive research has been conducted to use modelling approaches to interpret tendon structure-function relationships in combination with experimental data, many issues remain unclear (i.e. the role of minor components such as decorin, aggrecan and elastin), and the integration of mechanical analysis across different length scales has not been well applied to explore stress or strain transfer from macro- to microscale. This review outlines mathematical and computational models that have been used to understand tendon mechanics at different scales of the hierarchical organization. Model representations at the molecular, fibril and tissue levels are discussed, including formulations that follow phenomenological and microstructural approaches (which include evaluations of crimp, helical structure and the interaction between collagen fibrils and proteoglycans). Multiscale modelling approaches incorporating tendon features are suggested to be an advantageous methodology to understand further the physiological mechanical response of tendon and corresponding adaptation of properties owing to unique in vivo loading environments.
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Affiliation(s)
- Fei Fang
- Department of Mechanical Engineering and Materials Science , Washington University in St Louis , St Louis, MO 63130 , USA
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University in St Louis, St Louis, MO 63130, USA; Department of Biomedical Engineering, Washington University in St Louis, St Louis, MO 63130, USA; Department of Orthopaedic Surgery, Washington University in St Louis, St Louis, MO 63130, USA
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