1
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Bloom ET, Lin LM, Locke RC, Giordani A, Krassan E, Peloquin JM, Silbernagel KG, Parreno J, Santare MH, Killian ML, Elliott DM. Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional Degeneration. J Biomech Eng 2023; 145:081003. [PMID: 37184932 PMCID: PMC10782872 DOI: 10.1115/1.4062523] [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: 11/21/2022] [Revised: 05/02/2023] [Accepted: 05/04/2023] [Indexed: 05/16/2023]
Abstract
Tendon degeneration is typically described as an overuse injury with little distinction made between magnitude of load (overload) and number of cycles (overuse). Further, in vivo, animal models of tendon degeneration are mostly overuse models, where tendon damage is caused by a high number of load cycles. As a result, there is a lack of knowledge of how isolated overload leads to degeneration in tendons. A surgical model of synergist ablation (SynAb) overloads the target tendon, plantaris, by ablating its synergist tendon, Achilles. The objective of this study was to evaluate the structural and functional changes that occur following overload of plantaris tendon in a rat SynAb model. Tendon cross-sectional area (CSA) and shape changes were evaluated by longitudinal MR imaging up to 8 weeks postsurgery. Tissue-scale structural changes were evaluated by semiquantified histology and second harmonic generation microscopy. Fibril level changes were evaluated with serial block face scanning electron microscopy (SBF-SEM). Functional changes were evaluated using tension tests at the tissue and microscale using a custom testing system allowing both video and microscopy imaging. At 8 weeks, overloaded plantaris tendons exhibited degenerative changes including increases in CSA, cell density, collagen damage area fraction (DAF), and fibril diameter, and decreases in collagen alignment, modulus, and yield stress. To interpret the differences between overload and overuse in tendon, we introduce a new framework for tendon remodeling and degeneration that differentiates between the inputs of overload and overuse. In summary, isolated overload induces multiscale degenerative structural and functional changes in plantaris tendon.
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Affiliation(s)
- Ellen T Bloom
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Lily M Lin
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Ryan C Locke
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104; Translational Musculoskeletal Research Center, CMCVAMC, Philadelphia, PA 19104
| | - Alyssa Giordani
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - Erin Krassan
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | - John M Peloquin
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
| | | | - Justin Parreno
- Department of Biological Sciences, University of Delaware, Newark, DE 19716
| | - Michael H Santare
- Department of Mechanical Engineering, University of Delaware, Newark, DE 19716
| | - Megan L Killian
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI 48104
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, Newark, DE 19716
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2
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Lin AH, Slater CA, Martinez CJ, Eppell SJ, Yu SM, Weiss JA. Collagen fibrils from both positional and energy-storing tendons exhibit increased amounts of denatured collagen when stretched beyond the yield point. Acta Biomater 2023; 155:461-470. [PMID: 36400348 PMCID: PMC9805521 DOI: 10.1016/j.actbio.2022.11.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 11/04/2022] [Accepted: 11/09/2022] [Indexed: 11/17/2022]
Abstract
Collagen molecules are the base structural unit of tendons, which become denatured during mechanical overload. We recently demonstrated that during tendon stretch, collagen denaturation occurs at the yield point of the stress-strain curve in both positional and energy-storing tendons. We were interested in investigating how this load is transferred throughout the collagen hierarchy, and sought to determine the onset of collagen denaturation when collagen fibrils are stretched. Fibrils are one level above the collagen molecule in the collagen hierarchy, allowing more direct probing of the effect of strain on collagen molecules. We isolated collagen fibrils from both positional and energy-storing tendon types and stretched them using a microelectromechanical system device to various levels of strain. We stained the fibrils with fluorescently labeled collagen hybridizing peptides that specifically bind to denatured collagen, and examined whether samples stretched beyond the yield point of the stress-strain curve exhibited increased amounts of denatured collagen. We found that collagen denaturation in collagen fibrils from both tendon types occurs at the yield point. Greater amounts of denatured collagen were found in post-yield positional fibrils than in energy-storing fibrils. This is despite a greater yield strain and yield stress in fibrils from energy-storing tendons compared to positional tendons. Interestingly, the peak modulus of collagen fibrils from both tendon types was the same. These results are likely explained by the greater crosslink density found in energy-storing tendons compared to positional tendons. The insights gained from this study could help management of tendon and other musculoskeletal injuries by targeting collagen molecular damage at the fibril level. STATEMENT OF SIGNIFICANCE: When tendons are stretched or torn, this can lead to collagen denaturation (damage). Depending on their biomechanical function, tendons are considered positional or energy-storing with different crosslink profiles. By stretching collagen fibrils instead of fascicles from both tendon types, we can more directly examine the effect of tensile stretch on the collagen molecule in tendons. We found that regardless of tendon type, collagen denaturation in fibrils occurs when they are stretched beyond the yield point of the stress-strain curve. This provides insight into how load affects different tendon sub-structures during tendon injuries and failure, which will help clinicians and researchers understand mechanisms of injuries and potentially target collagen molecular damage as a treatment strategy, leading to improved clinical outcomes following injury.
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Affiliation(s)
- Allen H Lin
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States
| | - Christopher A Slater
- Department of Biomedical Engineering, Case Western Reserve University, United States
| | - Callie-Jo Martinez
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States
| | - Steven J Eppell
- Department of Biomedical Engineering, Case Western Reserve University, United States
| | - S Michael Yu
- Department of Biomedical Engineering, University of Utah, United States; Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, United States
| | - Jeffrey A Weiss
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States; Department of Orthopaedics, University of Utah, United States.
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3
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Allan AN, Zitnay JL, Maas SA, Weiss JA. Development of a continuum damage model to Predict accumulation of sub-failure damage in tendons. J Mech Behav Biomed Mater 2022; 135:105342. [DOI: 10.1016/j.jmbbm.2022.105342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 05/18/2022] [Accepted: 06/26/2022] [Indexed: 11/17/2022]
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4
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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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5
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Wu SY, Kim W, Kremen TJ. In Vitro Cellular Strain Models of Tendon Biology and Tenogenic Differentiation. Front Bioeng Biotechnol 2022; 10:826748. [PMID: 35242750 PMCID: PMC8886160 DOI: 10.3389/fbioe.2022.826748] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 01/17/2022] [Indexed: 11/19/2022] Open
Abstract
Research has shown that the surrounding biomechanical environment plays a significant role in the development, differentiation, repair, and degradation of tendon, but the interactions between tendon cells and the forces they experience are complex. In vitro mechanical stimulation models attempt to understand the effects of mechanical load on tendon and connective tissue progenitor cells. This article reviews multiple mechanical stimulation models used to study tendon mechanobiology and provides an overview of the current progress in modelling the complex native biomechanical environment of tendon. Though great strides have been made in advancing the understanding of the role of mechanical stimulation in tendon development, damage, and repair, there exists no ideal in vitro model. Further comparative studies and careful consideration of loading parameters, cell populations, and biochemical additives may further offer new insight into an ideal model for the support of tendon regeneration studies.
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Affiliation(s)
- Shannon Y. Wu
- David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Won Kim
- Department of Rehabilitation Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Thomas J. Kremen
- Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
- *Correspondence: Thomas J. Kremen Jr,
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Sensini A, Santare MH, Eichenlaub E, Bloom E, Gotti C, Zucchelli A, Cristofolini L. Tuning the Structure of Nylon 6,6 Electrospun Bundles to Mimic the Mechanical Performance of Tendon Fascicles. Front Bioeng Biotechnol 2021; 9:626433. [PMID: 33889568 PMCID: PMC8056020 DOI: 10.3389/fbioe.2021.626433] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 03/08/2021] [Indexed: 12/12/2022] Open
Abstract
Tendon and ligament injuries are triggered by mechanical loading, but the specific mechanisms are not yet clearly identified. It is well established however, that the inflection and transition points in tendon stress-strain curves represent thresholds that may signal the onset of irreversible fibrillar sliding. This phenomenon often results in a progressive macroscopic failure of these tissues. With the aim to simulate and replace tendons, electrospinning has been demonstrated to be a suitable technology to produce nanofibers similar to the collagen fibrils in a mat form. These nanofibrous mats can be easily assembled in higher hierarchical levels to reproduce the whole tissue structure. Despite the fact that several groups have developed electrospun tendon-inspired structures, an investigation of the inflection and transition point mechanics is missing. Comparing their behavior with that of the natural counterpart is important to adequately replicate their behavior at physiological strain levels. To fill this gap, in this work fascicle-inspired electrospun nylon 6,6 bundles were produced with different collector peripheral speeds (i.e., 19.7 m s–1; 13.7 m s–1; 7.9 m s–1), obtaining different patterns of nanofibers alignment. The scanning electron microcopy revealed a fibril-inspired structure of the nanofibers with an orientation at the higher speed similar to those in tendons and ligaments (T/L). A tensile mechanical characterization was carried out showing an elastic-brittle biomimetic behavior for the higher speed bundles with a progressively more ductile behavior at slower speeds. Moreover, for each sample category the transition and the inflection points were defined to study how these points can shift with the nanofiber arrangement and to compare their values with those of tendons. The results of this study will be of extreme interest for the material scientists working in the field, to model and improve the design of their electrospun structures and scaffolds and enable building a new generation of artificial tendons and ligaments.
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Affiliation(s)
- Alberto Sensini
- Advanced Applications in Mechanical Engineering and Materials Technology - Interdepartmental Center for Industrial Research (CIRI-MAM), Alma Mater Studiorum-Università di Bologna, Bologna, Italy
| | - Michael H Santare
- Department of Mechanical Engineering, University of Delaware, Newark, DE, United States.,Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Emily Eichenlaub
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Ellen Bloom
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Carlo Gotti
- Department of Industrial Engineering, Alma Mater Studiorum-Università di Bologna, Bologna, Italy
| | - Andrea Zucchelli
- Advanced Applications in Mechanical Engineering and Materials Technology - Interdepartmental Center for Industrial Research (CIRI-MAM), Alma Mater Studiorum-Università di Bologna, Bologna, Italy.,Department of Industrial Engineering, Alma Mater Studiorum-Università di Bologna, Bologna, Italy
| | - Luca Cristofolini
- Department of Industrial Engineering, Alma Mater Studiorum-Università di Bologna, Bologna, Italy.,Health Sciences and Technologies - Interdepartmental Center for Industrial Research (CIRI-HST), Alma Mater Studiorum-Università di Bologna, Bologna, Italy
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7
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Blache U, Wunderli SL, Hussien AA, Stauber T, Flückiger G, Bollhalder M, Niederöst B, Fucentese SF, Snedeker JG. Inhibition of ERK 1/2 kinases prevents tendon matrix breakdown. Sci Rep 2021; 11:6838. [PMID: 33767224 PMCID: PMC7994809 DOI: 10.1038/s41598-021-85331-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 02/26/2021] [Indexed: 12/14/2022] Open
Abstract
Tendon extracellular matrix (ECM) mechanical unloading results in tissue degradation and breakdown, with niche-dependent cellular stress directing proteolytic degradation of tendon. Here, we show that the extracellular-signal regulated kinase (ERK) pathway is central in tendon degradation of load-deprived tissue explants. We show that ERK 1/2 are highly phosphorylated in mechanically unloaded tendon fascicles in a vascular niche-dependent manner. Pharmacological inhibition of ERK 1/2 abolishes the induction of ECM catabolic gene expression (MMPs) and fully prevents loss of mechanical properties. Moreover, ERK 1/2 inhibition in unloaded tendon fascicles suppresses features of pathological tissue remodeling such as collagen type 3 matrix switch and the induction of the pro-fibrotic cytokine interleukin 11. This work demonstrates ERK signaling as a central checkpoint to trigger tendon matrix degradation and remodeling using load-deprived tissue explants.
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Affiliation(s)
- Ulrich Blache
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Stefania L Wunderli
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Amro A Hussien
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Tino Stauber
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Gabriel Flückiger
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Maja Bollhalder
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Barbara Niederöst
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Sandro F Fucentese
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Jess G Snedeker
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland.
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8
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Firminger CR, Edwards WB. Effects of cyclic loading on the mechanical properties and failure of human patellar tendon. J Biomech 2021; 120:110345. [PMID: 33735631 DOI: 10.1016/j.jbiomech.2021.110345] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/18/2021] [Accepted: 02/22/2021] [Indexed: 12/31/2022]
Abstract
Patellar tendinopathy is a common overuse injury in sports such as volleyball, basketball, and long-distance running. Microdamage accumulation, in response to repetitive loading of the tendon, plays an important role in the pathophysiology of patellar tendinopathy. This damage presents mechanically as a reduction in Young's modulus and an increase in residual strain. In this study, 19 human patellar tendon samples underwent cyclic testing in load control until failure, segmented by four ramped tests where digital image correlation (DIC) was used to assess anterior surface strain distributions. Ramped tests were performed prior to cyclic testing and at timepoints corresponding to 10%, 20%, and 30% of cyclic stiffness reduction. Young's modulus significantly decreased and cyclic energy dissipation significantly increased over the course of cyclic testing. The DIC analysis illustrated a heterogeneous strain distribution, with strain concentrations increasing in magnitude and size over the course of cyclic testing. Peak stress and initial peak strain magnitudes significantly correlated with the number of cycles to failure (r2 = 0.65 and r2 = 0.57, respectively, p < 0.001); however, the rates of peak cyclic strain and modulus loss displayed the highest correlations with the number of cycles to failure (r2 = 96% and r2 = 86%, respectively, p < 0.001). The high correlation between the rates of peak cyclic strain and modulus loss suggest that non-invasive methods to continuously monitor tendon strain may provide meaningful predictions of overuse injury in the patellar tendon.
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Affiliation(s)
- Colin R Firminger
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada; Biomedical Engineering Graduate Program, University of Calgary, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Canada.
| | - W Brent Edwards
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada; Biomedical Engineering Graduate Program, University of Calgary, Canada; McCaig Institute for Bone and Joint Health, University of Calgary, Canada
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9
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Bloom ET, Lee AH, Elliott DM. Tendon Multiscale Structure, Mechanics, and Damage Are Affected by Osmolarity of Bath Solution. Ann Biomed Eng 2021; 49:1058-1068. [PMID: 33128181 PMCID: PMC7954897 DOI: 10.1007/s10439-020-02649-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 10/03/2020] [Indexed: 11/29/2022]
Abstract
One of the most common bath solutions used in musculoskeletal mechanical testing is phosphate buffered saline (PBS). In tendon, swelling induced by physiological PBS results in decreased tendon modulus and induces microstructural changes. It is critical to evaluate the multiscale mechanical behavior of tendon under swelling to interpret prior work and provide information to design future studies. We compared the effects of physiological PBS and 8% polyethylene glycol and saline bathing solutions on tendon multiscale tendon mechanics and damage as well as microstructure with TEM in order to understand the effect of swelling on tendon. At the tissue level, tendons in PBS had a lower modulus than SPEG samples. PBS samples also showed an increased amount of non-recoverable sliding, which is an analog for microscale damage. SPEG had a higher microscale to tissue-scale strain ratio, showing the fibrils experienced less strain attenuation. From the TEM data, we showed the fibril spacing of SPEG samples was more similar to fresh control than PBS. We concluded that swelling alters multiscale mechanics and damage in addition to tendon microstructure. Future mechanical testing should consider using SPEG as a bath solution with an osmotic pressure which preserves fresh tissue water content.
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Affiliation(s)
- Ellen T Bloom
- Department of Biomedical Engineering, University of Delaware, 161 Colburn Lab, 150 Academy Street, Newark, DE, 19716, USA
| | - Andrea H Lee
- Department of Biomedical Engineering, University of Delaware, 161 Colburn Lab, 150 Academy Street, Newark, DE, 19716, USA
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, 161 Colburn Lab, 150 Academy Street, Newark, DE, 19716, USA.
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10
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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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11
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Lin AH, Allan AN, Zitnay JL, Kessler JL, Yu SM, Weiss JA. Collagen denaturation is initiated upon tissue yield in both positional and energy-storing tendons. Acta Biomater 2020; 118:153-160. [PMID: 33035697 DOI: 10.1016/j.actbio.2020.09.056] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/04/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022]
Abstract
Tendons are collagenous soft tissues that transmit loads between muscles and bones. Depending on their anatomical function, tendons are classified as positional or energy-storing with differing biomechanical and biochemical properties. We recently demonstrated that during monotonic stretch of positional tendons, permanent denatured collagen begins accumulating upon departing the linear region of the stress-strain curve. However, it is unknown if this observation is true during mechanical overload of other types of tendons. Therefore, the purpose of this study was to investigate the onset of collagen denaturation relative to applied strain, and whether it differs between the two tendon types. Rat tail tendon (RTT) fascicles and rat flexor digitorum longus (FDL) tendons represented positional and energy-storing tendons, respectively. The samples were stretched to incremental levels of strain, then stained with fluorescently labeled collagen hybridizing peptides (CHPs); the CHP fluorescence was measured to quantify denatured collagen. Denatured collagen in both positional and energy-storing tendons began to increase at the yield strain, upon leaving the linear region of the stress-strain curve as the sample started to permanently deform. Despite significant differences between the two tendon types, it appears that collagen denaturation is initiated at tissue yield during monotonic stretch, and the fundamental mechanism of failure is the same for the two types of tendons. At tissue failure, positional tendons had double the percentage of denatured collagen compared to energy-storing tendons, with no difference between 0% control groups. These results help to elucidate the etiology of subfailure injury and rupture in functionally distinct tendons.
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Affiliation(s)
- Allen H Lin
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States
| | - Alexandra N Allan
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States
| | - Jared L Zitnay
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States
| | - Julian L Kessler
- Department of Biomedical Engineering, University of Utah, United States
| | - S Michael Yu
- Department of Biomedical Engineering, University of Utah, United States; Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, United States
| | - Jeffrey A Weiss
- Department of Biomedical Engineering, University of Utah, United States; Scientific Computing and Imaging Institute, University of Utah, United States; Department of Orthopaedics, University of Utah, United States.
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Muench JR, Thelen DG, Henak CR. Interfibrillar shear behavior is altered in aging tendon fascicles. Biomech Model Mechanobiol 2019; 19:841-849. [PMID: 31707625 DOI: 10.1007/s10237-019-01251-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/04/2019] [Indexed: 12/11/2022]
Abstract
Tendon elongation involves both stretching and sliding between adjacent fascicles and fibers. Hence, age-related changes in tendon matrix properties may alter sliding behavior and thereby affect injury thresholds. The objective of this study was to investigate the effects of age on interfibrillar shear behavior in partial cut tendon fascicles. Cine microscopic imaging was used to track deformation patterns of intact and partial cut fascicles from mature (9 months, n = 10) and aged (32 months, n = 10) rat tail tendons. Finite element (FE) models coupled with experimental data provided insight into age-related changes in tissue constitutive properties that could give rise to age-dependent behavior. Intact fascicles from aged tendons exhibited a 28% lower linear region modulus and reduced toe region when compared to fascicles from mature tendons. Partial cut tendon fascicles consistently exhibited a shearing plane that extended longitudinally from the tip of the cut. Both mature and aged fascicles exhibited distinct failure that was observable in differential displacement across the shearing plane. However, aged fascicles exhibited 11-20% higher grip-to-grip strain at failure and tended to exhibit more variable and greater differential displacement at failure, when compared to mature fascicles. FE models suggest that this age-related change in shear behavior arises from a reduction in interfibrillar shear modulus with age. These data suggest that aging alters interfibrillar failure mechanisms and hence may contribute to the increased propensity for injury that is commonly seen in older tendons.
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Affiliation(s)
- Jared R Muench
- Department of Mechanical Engineering, University of Wisconsin-Madison, 3031 Mechanical Engineering Building, 1513 University Avenue, Madison, WI, 53706, USA
| | - Darryl G Thelen
- Department of Mechanical Engineering, University of Wisconsin-Madison, 3031 Mechanical Engineering Building, 1513 University Avenue, Madison, WI, 53706, USA.,Department of Biomedical Engineering, University of Wisconsin-Madison, 1550 Engineering Drive, Madison, WI, USA.,Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, USA
| | - Corinne R Henak
- Department of Mechanical Engineering, University of Wisconsin-Madison, 3031 Mechanical Engineering Building, 1513 University Avenue, Madison, WI, 53706, USA. .,Department of Biomedical Engineering, University of Wisconsin-Madison, 1550 Engineering Drive, Madison, WI, USA. .,Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, USA.
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