1
|
Safa BN, Fraticelli Guzmán NS, Li G, Stamer WD, Feola AJ, Ethier CR. A Histomorphometric and Computational Investigation of the Stabilizing Role of Pectinate Ligaments in the Aqueous Outflow Pathway. J Biomech Eng 2024; 146:081011. [PMID: 38529724 DOI: 10.1115/1.4065164] [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: 12/01/2023] [Accepted: 03/22/2024] [Indexed: 03/27/2024]
Abstract
Murine models are commonly used to study glaucoma, the leading cause of irreversible blindness. Glaucoma is associated with elevated intra-ocular pressure (IOP), which is regulated by the tissues of the aqueous outflow pathway. In particular, pectinate ligaments (PLs) connect the iris and trabecular meshwork (TM) at the anterior chamber angle, with an unknown role in maintenance of the biomechanical stability of the aqueous outflow pathway, thus motivating this study. We conducted histomorphometric analysis and optical coherence tomography-based finite element (FE) modeling on three cohorts of C57BL/6 mice: "young" (2-6 months), "middle-aged" (11-16 months), and "elderly" (25-32 months). We evaluated the age-specific morphology of the outflow pathway tissues. Further, because of the known pressure-dependent Schlemm's canal (SC) narrowing, we assessed the dependence of the SC lumen area on varying IOPs in age-specific FE models over a physiological range of TM/PL stiffness values. We found age-dependent changes in morphology of outflow tissues; notably, the PLs were more developed in older mice compared to younger ones. In addition, FE modeling demonstrated that murine SC patency is highly dependent on the presence of PLs and that increased IOP caused SC collapse only with sufficiently low TM/PL stiffness values. Moreover, the elderly model showed more susceptibility to SC collapse compared to the younger models. In conclusion, our study elucidated the previously unexplored role of PLs in the aqueous outflow pathway, indicating their function in supporting TM and SC under elevated IOP.
Collapse
Affiliation(s)
- Babak N Safa
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332
| | - Nina Sara Fraticelli Guzmán
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30318; Department of Ophthalmology, Emory University, Atlanta, GA 30332
- Georgia Institute of Technology
| | - Guorong Li
- Department of Ophthalmology, Duke University, Durham, NC 27705
- Duke University
| | - W Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, NC 27705
- Duke University
| | - Andrew J Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332; Department of Ophthalmology, Emory University, Atlanta, GA 30322; Atlanta VA Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affair Healthcare System, Decatur, GA 30033
- Emory University
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA 30332; George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30318; Department of Ophthalmology, Emory University, Atlanta, GA 30332
| |
Collapse
|
2
|
Yaghoobi H, Tremblais C, Gareau A, Cointe M, Tikhomirov AB, Kreplak L, Labrie D. An interferometric-based tensile tester to resolve damage events within reconstituted multi-filaments collagen bundles. J Mech Behav Biomed Mater 2024; 152:106467. [PMID: 38387119 DOI: 10.1016/j.jmbbm.2024.106467] [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: 12/13/2023] [Revised: 02/09/2024] [Accepted: 02/15/2024] [Indexed: 02/24/2024]
Abstract
Understanding how mechanical damage propagates in load-bearing tissues such as skin, tendons and ligaments, is key to developing regenerative medicine solutions for when these tissues fail. For collagenous tissues in particular, damage is typically assessed after mechanical testing using a broad range of microscopy techniques because standard tensile testing systems do not have the time and force sensitivity to resolve mechanical damage events. Here we introduce an interferometric detection scheme to measure the displacement of a cantilever with a resolution of 0.03% of full scale at a sampling rate of 5000 samples/s. The system is validated using collagen fibers engineered to mimic mammalian tendons. The system can detect sudden decrease in force due to slippage between collagen filaments, one to five microns in diameter, within a fiber in air. It can also detect yield events associated with local collagen unfolding or sliding within collagen fibrils within a fiber in liquid. This is opening the road to the sub-failure study of damage propagation within a broad range of hierarchical biomaterials.
Collapse
Affiliation(s)
- Hessameddin Yaghoobi
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Chloe Tremblais
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Alex Gareau
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Matthieu Cointe
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Alexey B Tikhomirov
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Laurent Kreplak
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Daniel Labrie
- Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
| |
Collapse
|
3
|
Suhail A, Banerjee A, Rajesh R. Dissipation and recovery in collagen fibrils under cyclic loading: A molecular dynamics study. Phys Rev E 2024; 109:024411. [PMID: 38491641 DOI: 10.1103/physreve.109.024411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 01/22/2024] [Indexed: 03/18/2024]
Abstract
The hysteretic behavior exhibited by collagen fibrils, when subjected to cyclic loading, is known to result in both dissipation as well as accumulation of residual strain. On subsequent relaxation, partial recovery has also been reported. Cross-links have been considered to play a key role in overall mechanical properties. Here, we modify an existing coarse-grained molecular dynamics model for collagen fibril with initially cross-linked collagen molecules, which is known to reproduce the response to uniaxial strain, by incorporating reformation of cross-links to allow for possible recovery of the fibril. Using molecular dynamics simulations, we show that our model successfully replicates the key features observed in experimental data, including the movement of hysteresis loops, the time evolution of residual strains and energy dissipation, as well as the recovery observed during relaxation. We also show that the characteristic cycle number, describing the approach toward steady state, has a value similar to that in experiments. We also emphasize the vital role of the degree of cross-linking on the key features of the macroscopic response to cyclic loading.
Collapse
Affiliation(s)
- Amir Suhail
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | | | - R Rajesh
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| |
Collapse
|
4
|
Loflin BE, Ahn T, Colglazier KA, Banaszak Holl MM, Ashton-Miller JA, Wojtys EM, Schlecht SH. An Adolescent Murine In Vivo Anterior Cruciate Ligament Overuse Injury Model. Am J Sports Med 2023; 51:1721-1732. [PMID: 37092727 PMCID: PMC10348391 DOI: 10.1177/03635465231165753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
BACKGROUND Overuse ligament and tendon injuries are prevalent among recreational and competitive adolescent athletes. In vitro studies of the ligament and tendon suggest that mechanical overuse musculoskeletal injuries begin with collagen triple-helix unraveling, leading to collagen laxity and matrix damage. However, there are little in vivo data concerning this mechanism or the physiomechanical response to collagen disruption, particularly regarding the anterior cruciate ligament (ACL). PURPOSE To develop and validate a novel in vivo animal model for investigating the physiomechanical response to ACL collagen matrix damage accumulation and propagation in the ACL midsubstance, fibrocartilaginous entheses, and subchondral bone. STUDY DESIGN Controlled laboratory study. METHODS C57BL/6J adolescent inbred mice underwent 3 moderate to strenuous ACL fatigue loading sessions with a 72-hour recovery between sessions. Before each session, randomly selected subsets of mice (n = 12) were euthanized for quantifying collagen matrix damage (percent collagen unraveling) and ACL mechanics (strength and stiffness). This enabled the quasi-longitudinal assessment of collagen matrix damage accrual and whole tissue mechanical property changes across fatigue sessions. Additionally, all cyclic loading data were quantified to evaluate changes in knee mechanics (stiffness and hysteresis) across fatigue sessions. RESULTS Moderate to strenuous fatigue loading across 3 sessions led to a 24% weaker (P = .07) and 35% less stiff (P < .01) ACL compared with nonloaded controls. The unraveled collagen densities within the fatigued ACL and entheseal matrices after the second and third sessions were 38% (P < .01) and 15% (P = .02) higher compared with the nonloaded controls. CONCLUSION This study confirmed the hypothesis that in vivo ACL collagen matrix damage increases with tissue fatigue sessions, adversely impacting ACL mechanical properties. Moreover, the in vivo ACL findings were consistent with in vitro overloading research in humans. CLINICAL RELEVANCE The outcomes from this study support the use of this model for investigating ACL overuse injuries.
Collapse
Affiliation(s)
- Benjamin E. Loflin
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Taeyong Ahn
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Kaitlyn A. Colglazier
- Purdue School of Engineering and Technology, Purdue University–Indianapolis, Indianapolis, Indiana, USA
| | - Mark M. Banaszak Holl
- Department of Orthopaedic Surgery, Heersink School of Medicine, University of Alabama–Birmingham, Birmingham, Alabama, USA
| | | | - Edward M. Wojtys
- Department of Orthopaedic Surgery, University of Michigan School of Medicine, Ann Arbor, Michigan, USA
| | - Stephen H. Schlecht
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Purdue School of Engineering and Technology, Purdue University–Indianapolis, Indianapolis, Indiana, USA
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| |
Collapse
|
5
|
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.
Collapse
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.
| |
Collapse
|
6
|
Perry NPJ, Farina EM, Wang C, Price MD, Mazzocca AD. Editorial Commentary: Fascia Lata Allograft for Shoulder Superior Capsular Reconstruction: In the Fight Over Optimal Graft Choice for Irreparable Rotator Cuff Tears, Superior Capsular Reconstruction Proponents May Be Changing Their Gloves. Arthroscopy 2023; 39:29-31. [PMID: 36543419 DOI: 10.1016/j.arthro.2022.09.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 09/28/2022] [Indexed: 12/23/2022]
Abstract
Optimal treatment of irreparable rotator cuff tears is still debated. Proponents of the superior capsule reconstruction (SCR) have previously used fascia lata autograft and acellular dermal allograft. Interest is growing in using fascia lata allograft as a new graft material. Well-designed biomechanical studies are important to understand the mechanical properties of the superior capsular tissue and fascia lata allograft. Recent biomechanical research shows that fascia lata allograft has similar initial stiffness (over the first 2 mm) and ultimate load compared to the native superior capsule. That said, ultimate load is the load at which a construct fails, whereas the yield point is the load on the stress-strain curve at which a material transitions from elastic to plastic deformation. In the shoulder where the SCR, for example, is going to be repetitively loaded, it is potentially more meaningful to talk about the yield point in order to stay within the elastic range. Using this framework, the yield point for fascia lata allograft is approximately one third the yield point of native capsular tissue. Additionally, "initial" stiffness is not the entire story. At greater loads, fascia lata allograft has higher displacement compared to native tissue. Of importance, fascia lata allograft failed by sutures slowly cutting through the allograft tissue; this may represent a limitation of the construct that could be addressed using stitch configurations resistant to cut through. Fascia lata allograft is a promising solution for SCR. Biomechanical studies require nuanced interpretation, and most of all, do not evaluate clinical healing.
Collapse
|
7
|
Andriotis OG, Nalbach M, Thurner PJ. Mechanics of isolated individual collagen fibrils. Acta Biomater 2022; 163:35-49. [PMID: 36509398 DOI: 10.1016/j.actbio.2022.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 11/15/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022]
Abstract
Collagen fibrils are the fundamental structural elements in vertebrate animals and compose a framework that provides mechanical support to load-bearing tissues. Understanding how these fibrils initially form and mechanically function has been the focus of a myriad of detailed investigations over the last few decades. From these studies a great amount of knowledge has been acquired as well as a number of new questions to consider. In this review, we examine the current state of our knowledge of the mechanical properties of extant fibrils. We emphasize on the mechanical response and related deformation of collagen fibrils upon tension, which is the predominant load imposed in most collagen-rich tissues. We also illuminate the gaps in knowledge originating from the intriguing results that the field is still trying to interpret. STATEMENT OF SIGNIFICANCE: : Collagen is the result of millions of years of biological evolution and is a unique family of proteins, the majority of which provide mechanical support to biological tissues. Cells produce collagen molecules that self-assemble into larger structures, known as collagen fibrils. As simple as they appear under an optical microscope, collagen fibrils display a complex ultrastructural architecture tuned to the external forces that are imposed upon them. Even more complex is the way collagen fibrils deform under loading, and the nature of the mechanisms that drive their formation in the first place. Here, we present a cogent synthesis of the state-of-knowledge of collagen fibril mechanics. We focus on the information we have from in vitro experiments on individual, isolated from tissues, collagen fibrils and the knowledge available from in silico tests.
Collapse
Affiliation(s)
- Orestis G Andriotis
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria
| | - Mathis Nalbach
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria
| | - Philipp J Thurner
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Vienna, A-1060, Austria.
| |
Collapse
|
8
|
Suhail A, Banerjee A, Rajesh R. Kinetic model description of dissipation and recovery in collagen fibrils under cyclic loading. Phys Rev E 2022; 106:044407. [PMID: 36397482 DOI: 10.1103/physreve.106.044407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
Collagen fibrils, when subjected to cyclic loading, are known to exhibit hysteretic behavior with energy dissipation that is partially recovered on relaxation. In this paper, we develop a kinetic model for a collagen fibril incorporating presence of hidden loops and stochastic fragmentation as well as reformation of sacrificial bonds. We show that the model reproduces well the characteristic features of reported experimental data on cyclic response of collagen fibrils, such as moving hysteresis loops, time evolution of residual strains and energy dissipation, recovery on relaxation, etc. We show that the approach to the steady state is controlled by a characteristic cycle number for both residual strain as well as energy dissipation and is in good agreement with reported existing experimental data.
Collapse
Affiliation(s)
- Amir Suhail
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| | | | - R Rajesh
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India
- Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
| |
Collapse
|
9
|
Fontenele FF, Bouklas N. Understanding the inelastic response of collagen fibrils: A viscoelastic-plastic constitutive model. Acta Biomater 2022; 163:78-90. [PMID: 35835288 DOI: 10.1016/j.actbio.2022.07.011] [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: 03/30/2022] [Revised: 07/01/2022] [Accepted: 07/05/2022] [Indexed: 11/01/2022]
Abstract
Collagen fibrils, which are the lowest level fibrillar unit of organization of collagen, are thus of primary interest towards understanding the mechanical behavior of load-bearing soft tissues. The deformation of collagen fibrils shows unique mechanical features; namely, their high energy dissipation is even superior compared to most engineering materials. Additionally, there are indications that cyclic loading can further improve the toughness of collagen fibrils. Recent experiments from Liu at al. (2018) focused on the response of type I collagen fibrils to uniaxial cyclic loading, revealing some interesting results regarding their rate-dependent and inelastic response. In this work, we aim to develop a model that allows interpreting the complex nonlinear and inelastic response of collagen fibrils under cyclic loading. We propose a constitutive model that accounts for viscoelastic deformations through a decoupled strain-energy density function (into an elastic and a viscous parts), and for plastic deformations through plastic evolution laws. The stress-stretch response results obtained using this constitutive law showed good agreement with experimental data over complex loading paths. Ultimately we use the model to gain more insights on how cyclic loading and rate effects control the interplay between viscoelastic and plastic deformation in collagen fibrils, and to extrapolate the results from experimental data, analyzing how complex cyclic load influences energy dissipation and deformation mechanisms. STATEMENT OF SIGNIFICANCE: In this work, we develop a viscoelastic-plastic constitutive model for collagen fibrils with the aim of analyzing the effects of inelasticity and energy dissipation in this material, and more specifically the competition between viscoelasticity and plasticity in the context of cyclic loading and overload. Experimental and theoretical approaches so far have not fully clarified the interplay between viscous and plastic deformations during cyclic loading of collagen fibrils. Here, we aim to interpret the complex nonlinear response of collagen fibrils and, ultimately, suggest predictive capabilities that can inform tissue-level response and injury. To validate our model, we compare our results against the stress-stretch data obtained from experiments of cyclic loaded single fibrils performed by Liu et al. (2018).
Collapse
Affiliation(s)
- Fernanda F Fontenele
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, NY 14853, USA
| | - Nikolaos Bouklas
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, NY 14853, USA.
| |
Collapse
|
10
|
Chatterjee M, Muljadi PM, Andarawis-Puri N. The role of the tendon ECM in mechanotransduction: disruption and repair following overuse. Connect Tissue Res 2022; 63:28-42. [PMID: 34030531 DOI: 10.1080/03008207.2021.1925663] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Purpose: Tendon overuse injuries are prevalent conditions with limited therapeutic options to halt disease progression. The specialized extracellular matrix (ECM) both enables joint function and mediates mechanical signals to tendon cells, driving biological responses to exercise or injury. With overuse, tendon ECM composition and structure changes at multiple scales, disrupting mechanotransduction and resulting in inadequate repair and disease progression. This review highlights the multiscale ECM changes that occur with tendon overuse and corresponding effects on cell-matrix interactions and cellular response to load.Results: Different functional joint requirements and tendon types experience a wide range of loading profiles, creating varied downstream mechanical stimuli. Distinct ECM structure and mechanical properties within the fascicle matrix, interfascicle matrix, and enthesis and their varied disruption with overuse are considered. The pericellular matrix (PCM) comprising the microscale tendon cell environment has a unique composition that changes with overuse injury and exercise, suggesting an important role in mechanotransduction and promoting repair. Cell-matrix interactions are mediated by structures including cilia, integrins, connexins and cytoskeleton that signal downstream homeostasis, adaptation, or repair. ECM disruption with tendon overuse may cause altered mechanical loading and cell-matrix interactions, resulting in mechanobiological understimulation, apoptosis, and ineffective repair. Current interventions to promote repair of tendon overuse injuries including exercise, targeting cell signaling, and modulating inflammation are considered.Conclusion: Future therapeutics should be assessed with regard of their effects on multiscale mechanotransduction in addition to joint function, with consideration of the central role of ECM.
Collapse
Affiliation(s)
- Monideepa Chatterjee
- Nancy E. And Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | - Patrick M Muljadi
- Nancy E. And Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA
| | - Nelly Andarawis-Puri
- Nancy E. And Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA.,Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA.,Hospital for Special Surgery, New York, New York, USA
| |
Collapse
|
11
|
Al Makhzoomi AK, Kirk TB, Allison GT. A multiscale study of morphological changes in tendons following repeated cyclic loading. J Biomech 2021; 128:110790. [PMID: 34634539 DOI: 10.1016/j.jbiomech.2021.110790] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 11/30/2022]
Abstract
The response of white New Zealand rabbit Achilles tendons to load was assessed using mechanical measures and confocal arthroscopy (CA). The progression of fatigue-loading-induced damage of the macro- (tenocyte morphology, fiber anisotropy and waviness), as well as the mechanical profile, were assessed within the same non-viable intact tendon in response to prolonged cyclic and static loading (up to four hours) at different strain levels (3%, 6% and 9%). Strain-mediated repeated loading induced a significant decline in mechanical function (p < 0.05) with increased strain and cycles. Mechanical and structural resilience was lost with repeated loading (p < 0.05) at macroscales. The lengthening of D-periodicity correlated strongly with the overall tendon mechanical changes and loss of spindle shape in tenocytes. This is the first study to provide a clear concurrent assessment of form (morphology) and function (mechanics) of tendons undergoing different strain-mediated repeated loading at multiple-scale assessments. This study identifies a variety of multiscale properties that may contribute to the understanding of mechanisms of tendon pathology.
Collapse
Affiliation(s)
- Anas K Al Makhzoomi
- School of Allied Health, Faculty of Health Science, Curtin University, Perth, Western Australia, Australia.
| | - Thomas B Kirk
- School of Science, Engineering and Technology, RMIT University Vietnam, Ho Chi Minh City, Vietnam
| | - Garry T Allison
- Research Office, Curtin University, Perth, Western Australia, Australia
| |
Collapse
|
12
|
Al Makhzoomi AK, Kirk TB, Dye DE, Allison GT. The influence of glycosaminoglycan proteoglycan side chains on tensile force transmission and the nanostructural properties of Achilles tendons. Microsc Res Tech 2021; 85:233-243. [PMID: 34390286 DOI: 10.1002/jemt.23899] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 07/16/2021] [Accepted: 07/25/2021] [Indexed: 01/13/2023]
Abstract
This study investigates the nanostructural mechanisms that lie behind load transmission in tendons and the role of glycosaminoglycans (GAGs) in the transmission of force in the tendon extracellular matrix. The GAGs in white New Zealand rabbit Achilles tendons were enzymatically depleted, and the tendons subjected to cyclic loading at 6% strain for up to 2 hr. A nanoscale morphometric assessment of fibril deformation under strain was linked with the decline in the tendon macroscale mechanical properties. An atomic force microscope (AFM) was employed to characterize the D-periodicity within and between fibril bundles (WFB and BFB, respectively). By the end of the second hour of the applied strain, the WFB and BFB D-periodicities had significantly increased in the GAG-depleted group (29% increase compared with 15% for the control, p < .0001). No statistically significant differences were found between WFB and BFB D-periodicities in either the control or GAG-depleted groups, suggesting that mechanical load in Achilles tendons is uniformly distributed and fairly homogenous among the WFB and BFB networks. The results of this study have provided evidence of a cycle-dependent mechanism of damage accumulation. The accurate quantification of fibril elongation (measured as the WFB and BFB D-periodicity lengths) in response to macroscopic applied strain has assisted in assessing the complex structure-function relationship in Achilles tendon.
Collapse
Affiliation(s)
- Anas K Al Makhzoomi
- School of Allied Health, Faculty of Health Science, Curtin University, Perth, Western Australia, Australia
| | - Thomas B Kirk
- Dean, School of Science, Engineering and Technology, RMIT University Vietnam, Ho Chi Minh City, Vietnam
| | - Danielle E Dye
- Curtin Medical School, Faculty of Health Sciences, Curtin University, Perth, Western Australia, Australia
| | - Garry T Allison
- Associate Deputy Vice-Chancellor -Research Excellence - Curtin University, Perth, Western Australia, Australia, Member Board of Directors; Sports Medicine Australia, Perth
| |
Collapse
|
13
|
McElroy A, Klinge PM, Sledge D, Donahue JE, Glabman RA, Rashmir A. Evaluation of the Filum Terminale in Hereditary Equine Regional Dermal Asthenia. Vet Pathol 2021; 58:1100-1106. [PMID: 34056982 DOI: 10.1177/03009858211018660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The objectives of this study were to describe the anatomy, histology, and ultrastructure of the equine filum terminale (FT) and to describe the FT in hereditary equine regional dermal asthenia (HERDA), a model of human Ehlers-Danlos syndromes (EDS). Those humans suffer from tethered cord syndrome (TCS) caused by an abnormally structured FT wherein its attachment at the base of the vertebral column leads to long-term stretch-induced injury to the spinal cord. The pathophysiology of TCS in EDS is poorly understood, and there is a need for an animal model of the condition. Histopathologic and ultrastructural examinations were performed on FT from HERDA (n = 4) and control horses (n = 5) and were compared to FT from human TCS patients with and without EDS. Adipose, fibrous tissue, and neuronal elements were assessed. CD3 and CD20 immunohistochemistry was performed to clarify cell types (HERDA n = 2; control n = 5). Collagen fibrils were assessed in cross-section for fibril diameter and shape, and in longitudinal section for fibril disorganization, swelling, and fragmentation. The equine and human FT were similar, with both containing fibrous tissue, ependyma, neuropil, and nerve twigs. Hypervascularity was observed in both HERDA horses and human EDS-TCS patients and was not observed in equine or human controls. Moderate to severe abnormalities in collagen fibril orientation and architecture were observed in all HERDA horses and were similar to those observed in human EDS-TCS patients.
Collapse
Affiliation(s)
- Abigail McElroy
- 23325Rhode Island Hospital, Providence, RI, USA.,Brown University, Providence, RI, USA
| | - Petra M Klinge
- 23325Rhode Island Hospital, Providence, RI, USA.,Brown University, Providence, RI, USA
| | - Dodd Sledge
- 116098Michigan State University, East Lansing, MI, USA
| | - John E Donahue
- 23325Rhode Island Hospital, Providence, RI, USA.,Brown University, Providence, RI, USA
| | - Raisa A Glabman
- 116098Michigan State University, East Lansing, MI, USA.,Dr Glabman is now with the National Institutes of Health, Bethesda, MD, USA
| | - Ann Rashmir
- 116098Michigan State University, East Lansing, MI, USA.,Dr Rashmir is now with the Veterinary Surgical Services, Washington, DC, USA
| |
Collapse
|
14
|
Peacock C, Lee E, Beral T, Cisek R, Tokarz D, Kreplak L. Buckling and Torsional Instabilities of a Nanoscale Biological Rope Bound to an Elastic Substrate. ACS NANO 2020; 14:12877-12884. [PMID: 32966048 DOI: 10.1021/acsnano.0c03695] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Rope-like structures are ubiquitous in Nature. They are supermolecular assemblies of macromolecules responsible for the structural and mechanical integrity of plant and animal tissues. Collagen fibrils with diameters between 50 and 500 nm and their helical supermolecular structure are good examples of such nanoscale biological ropes. Like man-made laid ropes, fibrils are typically loaded in tension, and due to their large aspect ratio, they are, in principle, prone to buckling and torsional instabilities. One way to study buckling of a rigid rod is to attach it to a stretched elastic substrate that is then returned to its original length. In the case of single collagen fibrils, the observed behavior depends on the degree of hydration. By going from buckling in ambient conditions to immersed in a buffer, fibrils go from the well-known sine wave response to a localized behavior reminiscent of the bird-caging of laid ropes. In addition, in ambient conditions, the sine wave response coexists with the formation of loops along the length of the fibrils, as observed for the torsional instability of a twisted filament when tension is decreased. This work provides direct evidence that single collagen fibrils are highly susceptible to axial compression because of their helical supermolecular structure. As a result, mammals that use collagen fibrils as their main load-bearing element in many tissues have evolved mitigating strategies that protect single fibrils from axial compression damage.
Collapse
Affiliation(s)
- Chris Peacock
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4J5, Canada
| | - Eva Lee
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4J5, Canada
| | - Theo Beral
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4J5, Canada
| | - Richard Cisek
- Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Danielle Tokarz
- Department of Chemistry, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4J5, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, NS B3H 4R2, Canada
| |
Collapse
|
15
|
Bakir G, Girouard BE, Wiens R, Mastel S, Dillon E, Kansiz M, Gough KM. Orientation Matters: Polarization Dependent IR Spectroscopy of Collagen from Intact Tendon Down to the Single Fibril Level. Molecules 2020; 25:molecules25184295. [PMID: 32961663 PMCID: PMC7571167 DOI: 10.3390/molecules25184295] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/04/2020] [Accepted: 09/17/2020] [Indexed: 01/30/2023] Open
Abstract
Infrared (IR) spectroscopy has been used for decades to study collagen in mammalian tissues. While many changes in the spectral profiles appear under polarized IR light, the absorption bands are naturally broad because of tissue heterogeneity. A better understanding of the spectra of ordered collagen will aid in the evaluation of disorder in damaged collagen and in scar tissue. To that end, collagen spectra have been acquired with polarized far-field (FF) Fourier Transform Infrared (FTIR) imaging with a Focal Plane Array detector, with the relatively new method of FF optical photothermal IR (O-PTIR), and with nano-FTIR spectroscopy based on scattering-type scanning near-field optical microscopy (s-SNOM). The FF methods were applied to sections of intact tendon with fibers aligned parallel and perpendicular to the polarized light. The O-PTIR and nano-FTIR methods were applied to individual fibrils of 100–500 nm diameter, yielding the first confirmatory and complementary results on a biopolymer. We observed that the Amide I and II bands from the fibrils were narrower than those from the intact tendon, and that both relative intensities and band shapes were altered. These spectra represent reliable profiles for normal collagen type I fibrils of this dimension, under polarized IR light, and can serve as a benchmark for the study of collagenous tissues.
Collapse
Affiliation(s)
- Gorkem Bakir
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (G.B.); (B.E.G.); (R.W.)
| | - Benoit E. Girouard
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (G.B.); (B.E.G.); (R.W.)
| | - Richard Wiens
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (G.B.); (B.E.G.); (R.W.)
| | - Stefan Mastel
- neaspec GmbH, Eglfinger Weg 2, 85540 Munich-Haar, Germany;
| | - Eoghan Dillon
- Photothermal Spectroscopy Corp., 325 Chapala St, Santa Barbara, CA 93101, USA; (E.D.); (M.K.)
| | - Mustafa Kansiz
- Photothermal Spectroscopy Corp., 325 Chapala St, Santa Barbara, CA 93101, USA; (E.D.); (M.K.)
| | - Kathleen M. Gough
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; (G.B.); (B.E.G.); (R.W.)
- Correspondence:
| |
Collapse
|
16
|
Investigating the birth-related caudal maternal pelvic floor muscle injury: The consequences of low cycle fatigue damage. J Mech Behav Biomed Mater 2020; 110:103956. [PMID: 32957249 DOI: 10.1016/j.jmbbm.2020.103956] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/22/2020] [Accepted: 06/24/2020] [Indexed: 11/23/2022]
Abstract
BACKGROUND One of the major causes of pelvic organ prolapse is pelvic muscle injury sustained during a vaginal delivery. The most common site of this injury is where the pubovisceral muscle takes origin from the pubic bone. We hypothesized that it is possible for low-cycle material fatigue to occur at the origin of the pubovisceral muscle under the large repetitive loads associated with pushing during the second stage of a difficult labor. PURPOSE The main goal was to test if the origin of the pubovisceral muscle accumulates material damage under sub-maximal cyclic tensile loading and identify any microscopic evidence of such damage. METHODS Twenty origins of the ishiococcygeous muscle (homologous to the pubovisceral muscle in women) were dissected from female sheep pelvises. Four specimens were stretched to failure to characterize the failure properties of the specimens. Thirteen specimens were then subjected to relaxation and subsequent fatigue tests, while three specimens remained as untested controls. Histology was performed to check for microscopic damage accumulation. RESULTS The fatigue stress-time curves showed continuous stress softening, a sign of material damage accumulation. Histology confirmed the presence of accumulated microdamage in the form of kinked muscle fibers and muscle fiber disruption in the areas with higher deformation, namely in the muscle near the musculotendinous junction. CONCLUSIONS The origin of ovine ishiococcygeous muscle can accumulate damage under sub-maximal repetitive loading. The damage appears in the muscle near the musculotendinous junction and was sufficient to negatively affect the macroscopic mechanical properties of the specimens.
Collapse
|
17
|
Hakim H, Puel F, Bertucci W. Injury assessment in circus student-artists population; preliminary study. Sci Sports 2020. [DOI: 10.1016/j.scispo.2019.07.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
18
|
Baldwin SJ, Sampson J, Peacock CJ, Martin ML, Veres SP, Lee JM, Kreplak L. A new longitudinal variation in the structure of collagen fibrils and its relationship to locations of mechanical damage susceptibility. J Mech Behav Biomed Mater 2020; 110:103849. [PMID: 32501220 DOI: 10.1016/j.jmbbm.2020.103849] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 03/17/2020] [Accepted: 05/04/2020] [Indexed: 11/26/2022]
Abstract
The hierarchical architecture of the collagen fibril is well understood, involving non-integer staggering of collagen molecules which results in a 67 nm periodic molecular density variation termed D-banding. Other than this variation, collagen fibrils are considered to be homogeneous at the micro-scale and beyond. Interestingly, serial kink structures have been shown to form at discrete locations along the length of collagen fibrils from some mechanically overloaded tendons. The formation of these kinks at discrete locations along the length of fibrils (discrete plasticity) may indicate pre-existing structural variations at a length scale greater than that of the D-banding. Using a high velocity nanomechanical mapping technique, 25 tendon collagen fibrils, were mechanically and structurally mapped along 10 μm of their length in dehydrated and hydrated states with resolutions of 20 nm and 8 nm respectively. Analysis of the variation in hydrated indentation modulus along individual collagen fibrils revealed a micro-scale structural variation not observed in the hydrated or dehydrated structural maps. The spacing distribution of this variation was similar to that observed for inter-kink distances seen in SEM images of discrete plasticity type damage. We propose that longitudinal variation in collagen fibril structure leads to localized mechanical susceptibility to damage under overload. Furthermore, we suggest that this variation has its origins in heterogeneous crosslink density along the length of collagen fibrils. The presence of pre-existing sites of mechanical vulnerability along the length of collagen fibrils may be important to biological remodeling of tendon, with mechanically-activated sites having distinct protein binding capabilities and enzyme susceptibility.
Collapse
Affiliation(s)
- Samuel J Baldwin
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, B3H 4R2, Canada
| | - Josh Sampson
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, B3H 4R2, Canada
| | - Christopher J Peacock
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, B3H 4R2, Canada
| | - Meghan L Martin
- School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada; Division of Engineering, Saint Mary's University, 923 Robie Street, Halifax, NS, B3H 3C3, Canada
| | - J Michael Lee
- School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada; Department of Applied Oral Sciences, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, B3H 4R2, Canada; School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, PO Box 15000, Halifax, NS, B3H 4R2, Canada.
| |
Collapse
|
19
|
KarisAllen JJ, Veres SP. Effect of testing temperature on the nanostructural response of tendon to tensile mechanical overload. J Biomech 2020; 104:109720. [PMID: 32156441 DOI: 10.1016/j.jbiomech.2020.109720] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 02/04/2020] [Accepted: 02/18/2020] [Indexed: 01/04/2023]
Abstract
Despite many in vitro mechanical experiments of tendon being conducted at room temperature, few assessments have been made to determine how the structural response of tendon to mechanical overload may vary with ambient temperature. We explored whether damage to the collagen nanostructure of tendon resulting from tensile rupture varies with temperature. Use of bovine tail tendons in combination with NaBH4 crosslink stabilization treatment allowed us to probe the mechanisms underlying the observed changes. Untreated tendons and NaBH4-stabilized tendons were pulled to rupture at temperatures of 24, 37, and 55 °C. Of nine mechanical parameters measured from the resulting stress-strain curves, only yield stress differed between the tendons tested at 37 and 24 °C. When tested at 55 °C, untreated tendons showed large reductions in ultimate strength and toughness, while NaBH4-stabilized tendons showed smaller reductions. Differential scanning calorimetry was used to assess damage to the collagen fibril nanostructure of tendons resulting from rupture, with samples from the ruptured tendons compared to samples from the same tendons removed prior to loading. While there was indication that overload-induced molecular packing disruption to collagen fibrils may be heightened at 37 °C, statistical increases in damage compared to that occurring at 24 °C were only seen when testing was conducted at 55 °C. The results show that the temperature sensitivity of tendon to ramp loading depends on crosslinking within the tissue. In poorly crosslinked tissues, collagen may be more susceptible to mechanical damage when tested at physiologic temperature compared to room temperature. For tendons with a high density of thermally stable crosslinks, such as the human Achilles or patellar tendons, testing at room temperature should produce comparable results to testing at physiologic temperature.
Collapse
Affiliation(s)
| | - Samuel P Veres
- Division of Engineering, Saint Mary's University, Halifax, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, Canada.
| |
Collapse
|
20
|
Burla F, Dussi S, Martinez-Torres C, Tauber J, van der Gucht J, Koenderink GH. Connectivity and plasticity determine collagen network fracture. Proc Natl Acad Sci U S A 2020; 117:8326-8334. [PMID: 32238564 PMCID: PMC7165426 DOI: 10.1073/pnas.1920062117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Collagen forms the structural scaffold of connective tissues in all mammals. Tissues are remarkably resistant against mechanical deformations because collagen molecules hierarchically self-assemble in fibrous networks that stiffen with increasing strain. Nevertheless, collagen networks do fracture when tissues are overloaded or subject to pathological conditions such as aneurysms. Prior studies of the role of collagen in tissue fracture have mainly focused on tendons, which contain highly aligned bundles of collagen. By contrast, little is known about fracture of the orientationally more disordered collagen networks present in many other tissues such as skin and cartilage. Here, we combine shear rheology of reconstituted collagen networks with computer simulations to investigate the primary determinants of fracture in disordered collagen networks. We show that the fracture strain is controlled by the coordination number of the network junctions, with less connected networks fracturing at larger strains. The hierarchical structure of collagen fine-tunes the fracture strain by providing structural plasticity at the network and fiber level. Our findings imply that low connectivity and plasticity provide protective mechanisms against network fracture that can optimize the strength of biological tissues.
Collapse
Affiliation(s)
- Federica Burla
- Biological Soft Matter Group, Department of Living Matter, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Simone Dussi
- Physical Chemistry and Soft Matter, Wageningen University and Research, 6708 WE Wageningen, The Netherlands
| | - Cristina Martinez-Torres
- Biological Soft Matter Group, Department of Living Matter, AMOLF, 1098 XG Amsterdam, The Netherlands
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Justin Tauber
- Physical Chemistry and Soft Matter, Wageningen University and Research, 6708 WE Wageningen, The Netherlands
| | - Jasper van der Gucht
- Physical Chemistry and Soft Matter, Wageningen University and Research, 6708 WE Wageningen, The Netherlands;
| | - Gijsje H Koenderink
- Biological Soft Matter Group, Department of Living Matter, AMOLF, 1098 XG Amsterdam, The Netherlands;
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
| |
Collapse
|
21
|
Ghezelbash F, Shirazi-Adl A, Baghani M, Eskandari AH. On the modeling of human intervertebral disc annulus fibrosus: Elastic, permanent deformation and failure responses. J Biomech 2020; 102:109463. [DOI: 10.1016/j.jbiomech.2019.109463] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 10/20/2019] [Accepted: 10/22/2019] [Indexed: 11/26/2022]
|
22
|
Sohutskay DO, Puls TJ, Voytik-Harbin SL. Collagen Self-assembly: Biophysics and Biosignaling for Advanced Tissue Generation. MULTI-SCALE EXTRACELLULAR MATRIX MECHANICS AND MECHANOBIOLOGY 2020. [DOI: 10.1007/978-3-030-20182-1_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
23
|
Hijazi KM, Singfield KL, Veres SP. Ultrastructural response of tendon to excessive level or duration of tensile load supports that collagen fibrils are mechanically continuous. J Mech Behav Biomed Mater 2019; 97:30-40. [DOI: 10.1016/j.jmbbm.2019.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 04/24/2019] [Accepted: 05/02/2019] [Indexed: 01/12/2023]
|
24
|
A constitutive relation for the tissue composed of type-I collagen fibers under uniaxial tension. J Mech Behav Biomed Mater 2019; 97:222-228. [DOI: 10.1016/j.jmbbm.2019.05.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 04/10/2019] [Accepted: 05/17/2019] [Indexed: 02/04/2023]
|
25
|
Iqbal SMA, Deska-Gauthier D, Kreplak L. Assessing collagen fibrils molecular damage after a single stretch-release cycle. SOFT MATTER 2019; 15:6237-6246. [PMID: 31334527 DOI: 10.1039/c9sm00832b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mechanical testing of connective tissues such as tendons and ligaments can lead to collagen denaturation even in the absence of macroscale damage. The following tensile loading protocols, ramp loading to failure, overloading and release, cyclic overloading and cyclic fatigue loading, all yield molecular damage in rat or bovine tendons. Single collagen fibrils extracted from the positional common digital extensor tendon of the forelimb also show molecular damage after tensile loading to failure. Using fibrils from the same source we assess changes to the molecular and supramolecular structure after tensile stress relaxation at strains between 4 and 22% followed by release. We observe no broken fibril and no significant change in D-band spacing. However, we observe significant binding of a fluorescent collagen hybridizing peptide to the fibrils indicating that collagen denaturation occurs in a strain dependent way for relaxation times between 1 s and 1500 s. We also show that peptide binding is associated with a decrease of the cross-sectional area of the fibrils providing an estimate of the dry volume loss due to molecular denaturation as well as an estimate of the mechanical energy density required, 25-110 MJ m-3. In summary we show that collagen molecular damage can occur in the absence of fibril failure and without visible changes to the supramolecular structure.
Collapse
Affiliation(s)
- S M Asif Iqbal
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada.
| | | | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada. and School of Biomedical Engineering, Dalhousie University, Halifax, Canada
| |
Collapse
|
26
|
Lee AH, Elliott DM. Multi-Scale Loading and Damage Mechanisms of Plantaris and Rat Tail Tendons. J Orthop Res 2019; 37:1827-1837. [PMID: 30977538 PMCID: PMC6790141 DOI: 10.1002/jor.24309] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 02/21/2019] [Accepted: 03/13/2019] [Indexed: 02/04/2023]
Abstract
Tendinopathy, degeneration of the tendon that leads to pain and dysfunction, is common in both sports and occupational settings, but multi-scale mechanisms for tendinopathy are still unknown. We recently showed that micro-scale sliding (shear) is responsible for both load transfer and damage mechanisms in the rat tail tendon; however, the rat tail tendon is a specialized non-load-bearing tendon, and thus the load transfer and damage mechanisms are still unknown for load-bearing tendons. The objective of this study was to investigate the load transfer and damage mechanisms of load-bearing tendons using the rat plantaris tendon. We demonstrated that micro-scale sliding is a key component for both mechanisms in the plantaris tendon, similar to the tail tendon. Namely, the micro-scale sliding was correlated with applied strain, demonstrating that load was transferred via micro-scale sliding in the plantaris and tail tendons. In addition, while the micro-scale strain fully recovered, the micro-scale sliding was non-recoverable and strain-dependent, and correlated with tissue-scale mechanical parameters. When the applied strain was normalized, the % magnitudes of non-recoverable sliding was similar between the plantaris and tail tendons. Statement of clinical significance: Understanding the mechanisms responsible for the pathogenesis and progression of tendinopathy can improve prevention and rehabilitation strategies and guide therapies and the design of engineered constructs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1827-1837, 2019.
Collapse
Affiliation(s)
- Andrea H. Lee
- Department of Biomedical Engineering, University of Delaware
| | - Dawn M. Elliott
- Department of Biomedical Engineering, University of Delaware
| |
Collapse
|
27
|
Tendon tissue microdamage and the limits of intrinsic repair. Matrix Biol 2019; 85-86:68-79. [PMID: 31325483 DOI: 10.1016/j.matbio.2019.07.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/19/2019] [Accepted: 07/17/2019] [Indexed: 02/08/2023]
Abstract
The transmission of mechanical muscle force to bone for musculoskeletal stability and movement is one of the most important functions of tendon. The load-bearing tendon core is composed of highly aligned collagen-rich fascicles interspersed with stromal cells (tenocytes). Despite being built to bear very high mechanical stresses, supra-physiological/repetitive mechanical overloading leads to tendon microdamage in fascicles, and potentially to tendon disease and rupture. To date, it is unclear to what extent intrinsic healing mechanisms of the tendon core compartment can repair microdamage. In the present study, we investigated the healing capacity of the tendon core compartment in an ex vivo tissue explant model. To do so, we isolated rat tail tendon fascicles, damaged them by applying a single stretch to various degrees of sub-rupture damage and longitudinally assessed downstream functional and structural changes over a period of several days. Functional damage was assessed by changes in the elastic modulus of the material stress-strain curves, and biological viability of the resident tenocytes. Structural damage was quantified using a fluorescent collagen hybridizing peptide (CHP) to label mechanically disrupted collagen structures. While we observed functional mechanical damage for strains above 2% of the initial fascicle length, structural collagen damage was only detectable for 6% strain and beyond. Minimally loaded/damaged fascicles (2-4% strain) progressively lost elastic modulus over the course of tissue culture, despite their collagen structures remaining intact with high degree of maintained cell viability. In contrast, more severely overloaded fascicles (6-8% strain) with damage at the molecular/collagen level showed no further loss of the elastic modulus but markedly decreased cell viability. Surprisingly, in these heavily damaged fascicles the elastic modulus partially recovered, an effect also seen in further experiments on devitalized fascicles, implying the possibility of a non-cellular but matrix-driven mechanism of molecular repair. Overall, our findings indicate that the tendon core has very little capacity for self-repair of microdamage. We conclude that stromal tenocytes likely do not play a major role in anabolic repair of tendon matrix microdamage, but rather mediate catabolic matrix breakdown and communication with extrinsic cells that are able to effect tissue repair.
Collapse
|
28
|
Marino M, Converse MI, Monson KL, Wriggers P. Molecular-level collagen damage explains softening and failure of arterial tissues: A quantitative interpretation of CHP data with a novel elasto-damage model. J Mech Behav Biomed Mater 2019; 97:254-271. [PMID: 31132662 DOI: 10.1016/j.jmbbm.2019.04.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/12/2019] [Accepted: 04/11/2019] [Indexed: 01/26/2023]
Abstract
The present experimental-modelling study provides a quantitative interpretation of mechanical data and damage measurements obtained from collagen hybridizing peptide (CHP) techniques on overstretched sheep cerebral arterial tissues. To this aim, a structurally-motivated constitutive model is developed in the framework of continuum damage mechanics. The model includes two internal variables for describing the effects of collagen triple-helical unfolding via interstrand delamination: one governs plastic mechanisms in collagen fibers, leading to a stress softening response of the tissue at the macroscale; the other one describes the loss of fiber structural integrity, leading to tissue final failure. The proposed model is calibrated using the obtained mechanical experimental data, showing excellent fitting capabilities. The predicted evolution of internal variables agree well with independent measurements of molecular-level CHP-based damage data, obtaining an independent a posteriori validation of damage predictions. Moreover, available data on inelastic tissue elongation following supraphysiological loads are successfully reproduced. These outcomes further the hypothesis that the accumulation of interstrand delamination is a primary cause for the evolution of inelastic mechanisms in tissues, and in particular of stress softening up to failure.
Collapse
Affiliation(s)
- Michele Marino
- Institute of Continuum Mechanics, Leibniz Universität, 30167, Hannover, Germany.
| | - Matthew I Converse
- Department of Mechanical Engineering, University of Utah, UT, 84112, Salt Lake City, United States
| | - Kenneth L Monson
- Department of Mechanical Engineering, University of Utah, UT, 84112, Salt Lake City, United States; Department of Biomedical Engineering, University of Utah, UT, 84112, Salt Lake City, United States
| | - Peter Wriggers
- Institute of Continuum Mechanics, Leibniz Universität, 30167, Hannover, Germany
| |
Collapse
|
29
|
Baldwin SJ, Kreplak L, Lee JM. MMP-9 selectively cleaves non-D-banded material on collagen fibrils with discrete plasticity damage in mechanically-overloaded tendon. J Mech Behav Biomed Mater 2019; 95:67-75. [PMID: 30954916 DOI: 10.1016/j.jmbbm.2019.03.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 02/15/2019] [Accepted: 03/19/2019] [Indexed: 01/06/2023]
Abstract
The mechanical properties of tendon are due to the properties and arrangement of its collagen fibril content. Collagen fibrils are highly-organized supermolecular structures with a periodic banding pattern (D-band) indicative of the geometry of molecular organization. Following mechanical overload of whole tendon, collagen fibrils may plastically deform at discrete sites along their length, forming kinks, and acquiring a fuzzy, non-D-banded, outer layer (shell). Termed discrete plasticity, such non-uniform damage to collagen fibrils suggests localized cellular response at the fibril level during subsequent repair/replacement. Matrix metallo-proteinases (MMPs) are enzymes which act upon the extracellular matrix, facilitating cell mobility and playing important roles in wound healing. A sub-group within this family are the gelatinases, MMP-2 and MMP-9, which selectively cleave denatured collagen molecules. Of these two, MMP-9 is specifically upregulated during the initial stages of tendon repair. This suggests a singular function in damage debridement. Using atomic force microscopy (AFM), a novel fibril-level enzymatic assay was employed to assess enzymatic removal of material by trypsin and MMP-9 from individual fibrils which were: (i) untreated, (ii) partially heat denatured, (iii) or displaying discrete plasticity damaged after repeated mechanical overload. Both enzymes removed material from heat denatured and discrete plasticity-damaged fibrils; however, only MMP-9 demonstrated the selective removal of non-D-banded material, with greater removal from more damaged fibrils. The selectivity of MMP-9, coupled with documented upregulation, suggests a likely mechanism for the in vivo debridement of individual collagen fibrils, following tendon overload injury, and prior to deposition of new collagen.
Collapse
Affiliation(s)
- Samuel J Baldwin
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, Canada B3H 4R2.
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Sir James Dunn Building, 6310 Coburg Road, Main Office Rm 218, Halifax, NS, Canada B3H 4R2; School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, Halifax, NS, Canada B3H 4R2
| | - J Michael Lee
- School of Biomedical Engineering, Dalhousie University, 5981 University Avenue, Halifax, NS, Canada B3H 4R2; Department of Applied Oral Sciences, Dalhousie University, 5981 University Avenue, Halifax, NS, Canada B3H 4R2.
| |
Collapse
|
30
|
Lee JM, Veres SP. Advanced glycation end-product cross-linking inhibits biomechanical plasticity and characteristic failure morphology of native tendon. J Appl Physiol (1985) 2019; 126:832-841. [PMID: 30653412 DOI: 10.1152/japplphysiol.00430.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Advanced glycation end-products (AGEs) are formed in vivo from the nonenzymatic reaction between sugars and proteins. AGEs accumulate in long-lived tissues like tendons, cross-linking neighboring collagen molecules, and are in part complicit in connective tissue pathologies experienced in aging and with diabetes. We have previously described discrete plasticity: a characteristic form of nanoscale collagen fibril damage consisting of serial fibril kinking and collagen denaturation that occurs in some mechanically overloaded tendons. We suspect that this failure mechanism may be an adaptive trait of collagen fibrils and have published evidence that inflammatory cells may be able to recognize and digest the denatured collagen produced by overload. In this study, we treated bovine tail tendons with ribose to simulate long-term AGE cross-linking in vitro. We hypothesized that a high degree of cross-linking would inhibit the intermolecular sliding thought to be necessary for discrete plasticity to occur. Tendons were mechanically overloaded, and properties were investigated by differential scanning calorimetry and scanning election microscopy. Ribose cross-linking treatment altered the mechanical response of tendons after the yield point, significantly decreasing postyield extensibility and strain energy capacity before rupture. Coincident with altered mechanics, ribose cross-linking completely inhibited the discrete plasticity failure mechanism of tendon. Our results suggest that discrete plasticity, which may be an important physiological mechanism, becomes pathologically disabled by the formation of AGE cross-links in aging and diabetes. NEW & NOTEWORTHY We have previously shown that mechanically overloaded collagen fibrils in mammalian tendons accrue nanoscaled damage. This includes development of a characteristic kinking morphology within a shell of denatured collagen: discrete plasticity. Here, using a ribose-incubation model, we show that advanced glycation end-product cross-linking associated with aging and diabetes completely inhibits this mechanism. Since discrete plasticity appears to cue cellular remodeling, this result has important implications for diabetic tendinopathy.
Collapse
Affiliation(s)
- J Michael Lee
- School of Biomedical Engineering, Dalhousie University , Halifax , Canada.,Department of Applied Oral Sciences, Dalhousie University , Halifax , Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University , Halifax , Canada.,Division of Engineering, Saint Mary's University , Halifax , Canada
| |
Collapse
|
31
|
Zitnay JL, Weiss JA. Load transfer, damage, and failure in ligaments and tendons. J Orthop Res 2018; 36:3093-3104. [PMID: 30175857 PMCID: PMC6454883 DOI: 10.1002/jor.24134] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 08/14/2018] [Indexed: 02/04/2023]
Abstract
The function of ligaments and tendons is to support and transmit loads applied to the musculoskeletal system. These tissues are often able to perform their function for many decades; however, connective tissue disease and injury can compromise ligament and tendon integrity. A range of protein and non-protein constituents, combined in a complex structural hierarchy from the collagen molecule to the tissue and covering nanometer to centimeter length scales, govern tissue function, and impart characteristic non-linear material behavior. This review summarizes the structure of ligaments and tendons, the roles of their constituent components for load transfer across the hierarchy of structure, and the current understanding of how damage occurs in these tissues. Disease and injury can alter the constituent make-up and structural organization of ligaments and tendons, affecting tissue function, while also providing insight to the role and interactions of individual constituents. The studies and techniques presented here have helped to understand the relationship between tissue constituents and the physical mechanisms (e.g., stretching, sliding) that govern material behavior at and between length scales. In recent years, new techniques have been developed to probe ever smaller length scales and may help to elucidate mechanisms of load transfer and damage and the molecular constituents involved in the in the earliest stages of ligament and tendon damage. A detailed understanding of load transfer and damage from the molecular to the tissue level may elucidate targets for the treatment of connective tissue diseases and inform practice to prevent and rehabilitate ligament and tendon injuries. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3093-3104, 2018.
Collapse
Affiliation(s)
- Jared L. Zitnay
- Department of Bioengineering, and Scientific Computing and Imaging Institute University of Utah
| | - Jeffrey A. Weiss
- Department of Bioengineering, and Scientific Computing and Imaging Institute University of Utah,Department of Orthopaedics, University of Utah
| |
Collapse
|
32
|
Chambers NC, Herod TW, Veres SP. Ultrastructure of tendon rupture depends on strain rate and tendon type. J Orthop Res 2018; 36:2842-2850. [PMID: 29901228 DOI: 10.1002/jor.24067] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 06/03/2018] [Indexed: 02/04/2023]
Abstract
Previous research has shown that both the mechanics and elongation mechanisms of tendon and ligament vary with strain rate during tensile loading. In this study, we sought to determine if the ultrastructural damage created during tendon rupture also varies with strain rate. A bovine forelimb model was used, allowing two anatomically proximate but physiologically distinct tendons to be studies: the positional common digital extensor tendon, and the energy storing superficial digital flexor tendon. Samples from the two tendon types were ruptured at rates of either 1%/s or 10%/s. Relative to unruptured control samples, changes to collagen fibril structure were assessed using scanning electron microscopy (SEM), and changes to collagen molecule packing were studied using differential scanning calorimetry (DSC). Rupture at 1%/s caused discrete plasticity damage that extended along the length of collagen fibrils in both the extensor and flexor tendons. Consistent with this, DSC showed molecular packing disruption relative to control samples. Both SEM and DSC showed that extensor tendon fibrils sustained more severe damage than the more highly crosslinked flexor tendon fibrils. Increasing strain rate during rupture decreased the level of longitudinal disruption experienced by the collagen fibrils of both tendon types. Disruption to D-banding was no longer seen in the extensor tendon fibrils, and discrete plasticity damage was completely eliminated in the flexor tendon fibrils, indicating a transition to localized point failure. Ultrastructural damage resulting from tendon rupture depends on both strain rate and tendon type. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2842-2850, 2018.
Collapse
Affiliation(s)
- Neil C Chambers
- Division of Engineering, Saint Mary's University, Halifax, Nova Scotia, Canada
| | - Tyler W Herod
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Samuel P Veres
- Division of Engineering, Saint Mary's University, Halifax, Nova Scotia, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| |
Collapse
|
33
|
Freedman BR, Rodriguez AB, Leiphart RJ, Newton JB, Ban E, Sarver JJ, Mauck RL, Shenoy VB, Soslowsky LJ. Dynamic Loading and Tendon Healing Affect Multiscale Tendon Properties and ECM Stress Transmission. Sci Rep 2018; 8:10854. [PMID: 30022076 PMCID: PMC6052000 DOI: 10.1038/s41598-018-29060-y] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 06/26/2018] [Indexed: 12/15/2022] Open
Abstract
The extracellular matrix (ECM) is the primary biomechanical environment that interacts with tendon cells (tenocytes). Stresses applied via muscle contraction during skeletal movement transfer across structural hierarchies to the tenocyte nucleus in native uninjured tendons. Alterations to ECM structural and mechanical properties due to mechanical loading and tissue healing may affect this multiscale strain transfer and stress transmission through the ECM. This study explores the interface between dynamic loading and tendon healing across multiple length scales using living tendon explants. Results show that macroscale mechanical and structural properties are inferior following high magnitude dynamic loading (fatigue) in uninjured living tendon and that these effects propagate to the microscale. Although similar macroscale mechanical effects of dynamic loading are present in healing tendon compared to uninjured tendon, the microscale properties differed greatly during early healing. Regression analysis identified several variables (collagen and nuclear disorganization, cellularity, and F-actin) that directly predict nuclear deformation under loading. Finite element modeling predicted deficits in ECM stress transmission following fatigue loading and during healing. Together, this work identifies the multiscale response of tendon to dynamic loading and healing, and provides new insight into microenvironmental features that tenocytes may experience following injury and after cell delivery therapies.
Collapse
Affiliation(s)
- Benjamin R Freedman
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA.,John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
| | - Ashley B Rodriguez
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
| | - Ryan J Leiphart
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA
| | - Joseph B Newton
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA
| | - Ehsan Ban
- Department of Materials Science and Engineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA.,Center for Engineering Mechanobiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Joseph J Sarver
- Department of Biomedical Engineering, Drexel University, Philadelphia, PA, USA
| | - Robert L Mauck
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA
| | - Vivek B Shenoy
- Department of Materials Science and Engineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA.,Center for Engineering Mechanobiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Louis J Soslowsky
- McKay Orthopedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA. .,Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, USA.
| |
Collapse
|
34
|
Wiens R, Findlay CR, Baldwin SG, Kreplak L, Lee JM, Veres SP, Gough KM. High spatial resolution (1.1 μm and 20 nm) FTIR polarization contrast imaging reveals pre-rupture disorder in damaged tendon. Faraday Discuss 2018; 187:555-73. [PMID: 27048856 DOI: 10.1039/c5fd00168d] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Collagen is a major constituent in many life forms; in mammals, collagen appears as a component of skin, bone, tendon and cartilage, where it performs critical functions. Vibrational spectroscopy methods are excellent for studying the structure and function of collagen-containing tissues, as they provide molecular insight into composition and organization. The latter is particularly important for collagenous materials, given that a key feature is their hierarchical, oriented structure, organized from molecular to macroscopic length scales. Here, we present the first results of high-resolution FTIR polarization contrast imaging, at 1.1 μm and 20 nm scales, on control and mechanically damaged tendon. The spectroscopic data are supported with parallel SEM and correlated AFM imaging. Our goal is to explore the changes induced in tendon after the application of damaging mechanical stress, and the consequences for the healing processes. The results and possibilities for the application of these high-spatial-resolution FTIR techniques in spectral pathology, and eventually in clinical applications, are discussed.
Collapse
Affiliation(s)
- Richard Wiens
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
| | - Catherine R Findlay
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
| | - Samuel G Baldwin
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - J Michael Lee
- School of Biomedical Engineering, Dalhousie University, Halifax, NS B3H 3J5, Canada and Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, NS B3H 3J5, Canada and Division of Engineering, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | - Kathleen M Gough
- Department of Chemistry, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
| |
Collapse
|
35
|
Svensson RB, Smith ST, Moyer PJ, Magnusson SP. Effects of maturation and advanced glycation on tensile mechanics of collagen fibrils from rat tail and Achilles tendons. Acta Biomater 2018; 70:270-280. [PMID: 29447959 DOI: 10.1016/j.actbio.2018.02.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/24/2018] [Accepted: 02/06/2018] [Indexed: 02/06/2023]
Abstract
Connective tissues are ubiquitous throughout the body and consequently affect the function of many organs. In load bearing connective tissues like tendon, the mechanical functionality is provided almost exclusively by collagen fibrils that in turn are stabilized by covalent cross-links. Functionally distinct tendons display different cross-link patterns, which also change with maturation, but these differences have not been studied in detail at the fibril level. In the present study, a custom built nanomechanical test platform was designed and fabricated to measure tensile mechanics of individual fibrils from rat tendons. The influence of animal maturity (4 vs. 16 week old rats) and functionally different tendons (tail vs. Achilles tendons) were examined. Additionally the effect of methylglyoxal (MG) treatment in vitro to form advanced glycation end products (AGEs) was investigated. Age and tissue type had no significant effect on fibril mechanics, but MG treatment increased strength and stiffness without inducing brittleness and gave rise to a distinct three-phase mechanical response corroborating that previously reported in human patellar tendon fibrils. That age and tissue had little mechanical effect, tentatively suggest that variations in enzymatic cross-links may play a minor role after initial tissue formation. STATEMENT OF SIGNIFICANCE Tendons are connective tissues that connect muscle to bone and carry some of the greatest mechanical loads in the body, which makes them common sites of injury. A tendon is essentially a biological rope formed by thin strands called fibrils made of the protein collagen. Tendon function relies on the strength of these fibrils, which in turn depends on naturally occurring cross-links between collagen molecules, but the mechanical influence of these cross-links have not been measured before. It is believed that beneficial cross-linking occurs with maturation while additional cross-linking with aging may lead to brittleness, but this study provides evidence that maturation has little effect on mechanical function and that age-related cross-linking does not result in brittle collagen fibrils.
Collapse
Affiliation(s)
- Rene B Svensson
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Stuart T Smith
- Department of Mechanical Engineering and Engineering Science, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - Patrick J Moyer
- Department of Physics and Optical Science, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - S Peter Magnusson
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Musculoskeletal Rehabilitation Research Unit, Bispebjerg Hospital, University Hospital of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
36
|
Quigley AS, Bancelin S, Deska-Gauthier D, Légaré F, Kreplak L, Veres SP. In tendons, differing physiological requirements lead to functionally distinct nanostructures. Sci Rep 2018. [PMID: 29535366 PMCID: PMC5849720 DOI: 10.1038/s41598-018-22741-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The collagen-based tissues of animals are hierarchical structures: even tendon, the simplest collagenous tissue, has seven to eight levels of hierarchy. Tailoring tissue structure to match physiological function can occur at many different levels. We wanted to know if the control of tissue architecture to achieve function extends down to the nanoscale level of the individual, cable-like collagen fibrils. Using tendons from young adult bovine forelimbs, we performed stress-strain experiments on single collagen fibrils extracted from tendons with positional function, and tendons with energy storing function. Collagen fibrils from the two tendon types, which have known differences in intermolecular crosslinking, showed numerous differences in their responses to elongation. Unlike those from positional tendons, fibrils from energy storing tendons showed high strain stiffening and resistance to disruption in both molecular packing and conformation, helping to explain how these high stress tissues withstand millions of loading cycles with little reparative remodeling. Functional differences in load-bearing tissues are accompanied by important differences in nanoscale collagen fibril structure.
Collapse
Affiliation(s)
- Andrew S Quigley
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada
| | - Stéphane Bancelin
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux, Télécommunication, Varennes, Canada
| | | | - François Légaré
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux, Télécommunication, Varennes, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada. .,School of Biomedical Engineering, Dalhousie University, Halifax, Canada.
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, Canada. .,Division of Engineering, Saint Mary's University, Halifax, Canada.
| |
Collapse
|
37
|
Szczesny SE, Aeppli C, David A, Mauck RL. Fatigue loading of tendon results in collagen kinking and denaturation but does not change local tissue mechanics. J Biomech 2018. [PMID: 29519673 DOI: 10.1016/j.jbiomech.2018.02.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fatigue loading is a primary cause of tendon degeneration, which is characterized by the disruption of collagen fibers and the appearance of abnormal (e.g., cartilaginous, fatty, calcified) tissue deposits. The formation of such abnormal deposits, which further weakens the tissue, suggests that resident tendon cells acquire an aberrant phenotype in response to fatigue damage and the resulting altered mechanical microenvironment. While fatigue loading produces clear changes in collagen organization and molecular denaturation, no data exist regarding the effect of fatigue on the local tissue mechanical properties. Therefore, the objective of this study was to identify changes in the local tissue stiffness of tendons after fatigue loading. We hypothesized that fatigue damage would reduce local tissue stiffness, particularly in areas with significant structural damage (e.g., collagen denaturation). We tested this hypothesis by identifying regions of local fatigue damage (i.e., collagen fiber kinking and molecular denaturation) via histologic imaging and by measuring the local tissue modulus within these regions via atomic force microscopy (AFM). Counter to our initial hypothesis, we found no change in the local tissue modulus as a consequence of fatigue loading, despite widespread fiber kinking and collagen denaturation. These data suggest that immediate changes in topography and tissue structure - but not local tissue mechanics - initiate the early changes in tendon cell phenotype as a consequence of fatigue loading that ultimately culminate in tendon degeneration.
Collapse
Affiliation(s)
- Spencer E Szczesny
- Department of Orthopaedic Surgery, University of Pennsylvania, 110 Stemmler Hall, 36th Street & Hamilton Walk, Philadelphia, PA 19104, United States; Department of Biomedical Engineering, Department of Orthopaedics and Rehabilitation, Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, United States.
| | - Céline Aeppli
- Eidgenössische Technische Hochschule, Rämistrasse 101, 8092 Zürich, Switzerland
| | - Alexander David
- Department of Bioengineering, 240 Skirkanich Hall, 210 South 33rd Street, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Robert L Mauck
- Department of Orthopaedic Surgery, University of Pennsylvania, 110 Stemmler Hall, 36th Street & Hamilton Walk, Philadelphia, PA 19104, United States; Department of Bioengineering, 240 Skirkanich Hall, 210 South 33rd Street, University of Pennsylvania, Philadelphia, PA 19104, United States; Translational Musculoskeletal Research Center, Corporal Michael J. Crescenz Veterans Affairs Medical Center, 3900 Woodland Avenue, Philadelphia, PA 19104, United States
| |
Collapse
|
38
|
Herod TW, Veres SP. Development of overuse tendinopathy: A new descriptive model for the initiation of tendon damage during cyclic loading. J Orthop Res 2018; 36:467-476. [PMID: 28598009 DOI: 10.1002/jor.23629] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 06/05/2017] [Indexed: 02/04/2023]
Abstract
Tendinopathic tissue has long been characterized by changes to collagen microstructure. However, initial tendon damage from excessive mechanical loading-a hallmark of tendinopathy development-could occur at the nanoscale level of collagen fibrils. Indeed, it is on this scale that tenocytes interact directly with tendon matrix, and excessive collagen fibril damage not visible at the microscale could trigger a degenerative cascade. In this study, we explored whether initiation of tendon damage during cyclic loading occurs via a longitudinal compression-induced buckling mechanism of collagen fibrils leading to nanoscale kinkband development. Two groups of tendons were cyclically loaded to equivalent peak stresses. In each loading cycle, tendons in one group were unloaded to the zero displacement mark, while those in the other group were unloaded to a nominal level of tension, minimizing the potential for fibril buckling. Tendons that were unloaded to the zero displacement mark ruptured significantly sooner during cyclic loading (1,446 ± 737 vs. 4,069 ± 1,129 cycles), indicating that significant fatigue damage is accrued in the low stress, toe region of the load-deformation response. Ultrastructural analysis using scanning electron microscopy of tendons stopped after 1,000 cycles showed that maintaining a nominal tension slowed the accumulation of kinkbands, supporting a longitudinal compression-induced buckling mechanism as the basis for kinkband development. Based on our results, we present a new descriptive model for the initiation of tendon damage during cyclic loading. The so-called Compression of Unrecovered Elongation or CUE Model may provide useful insight into the development of tendinopathy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:467-476, 2018.
Collapse
Affiliation(s)
- Tyler W Herod
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada.,Division of Engineering, Saint Mary's University, 923 Robie Street, Halifax, Nova Scotia Canada B3H 3C3
| |
Collapse
|
39
|
Mersmann F, Bohm S, Arampatzis A. Imbalances in the Development of Muscle and Tendon as Risk Factor for Tendinopathies in Youth Athletes: A Review of Current Evidence and Concepts of Prevention. Front Physiol 2017; 8:987. [PMID: 29249987 PMCID: PMC5717808 DOI: 10.3389/fphys.2017.00987] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 11/17/2017] [Indexed: 01/09/2023] Open
Abstract
Tendons feature the crucial role to transmit the forces exerted by the muscles to the skeleton. Thus, an increase of the force generating capacity of a muscle needs to go in line with a corresponding modulation of the mechanical properties of the associated tendon to avoid potential harm to the integrity of the tendinous tissue. However, as summarized in the present narrative review, muscle and tendon differ with regard to both the time course of adaptation to mechanical loading as well as the responsiveness to certain types of mechanical stimulation. Plyometric loading, for example, seems to be a more potent stimulus for muscle compared to tendon adaptation. In growing athletes, the increased levels of circulating sex hormones might additionally augment an imbalanced development of muscle strength and tendon mechanical properties, which could potentially relate to the increasing incidence of tendon overload injuries that has been indicated for adolescence. In fact, increased tendon stress and strain due to a non-uniform musculotendinous development has been observed recently in adolescent volleyball athletes, a high-risk group for tendinopathy. These findings highlight the importance to deepen the current understanding of the interaction of loading and maturation and demonstrate the need for the development of preventive strategies. Therefore, this review concludes with an evidence-based concept for a specific loading program for increasing tendon stiffness, which could be implemented in the training regimen of young athletes at risk for tendinopathy. This program incorporates five sets of four contractions with an intensity of 85–90% of the isometric voluntary maximum and a movement/contraction duration that provides 3 s of high magnitude tendon strain.
Collapse
Affiliation(s)
- Falk Mersmann
- Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Berlin, Germany.,Berlin School of Movement Science, Berlin, Germany
| | - Sebastian Bohm
- Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Berlin, Germany.,Berlin School of Movement Science, Berlin, Germany
| | - Adamantios Arampatzis
- Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Berlin, Germany.,Berlin School of Movement Science, Berlin, Germany
| |
Collapse
|
40
|
Chen J, Ahn T, Colón-Bernal ID, Kim J, Banaszak Holl MM. The Relationship of Collagen Structural and Compositional Heterogeneity to Tissue Mechanical Properties: A Chemical Perspective. ACS NANO 2017; 11:10665-10671. [PMID: 29112404 DOI: 10.1021/acsnano.7b06826] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Collagen is the primary protein component in mammalian connective tissues. Over the last 20 years, evidence has mounted that collagen matrices exhibit substantial heterogeneity in their hierarchical structures and that this heterogeneity plays important roles in both structure and function. Herein, an overview of studies addressing the nanoscale compositional and structural heterogeneity is provided and connected to work exploring the mechanical implications for a number of tissues.
Collapse
Affiliation(s)
- Junjie Chen
- Department of Chemistry, ‡Macromolecular Science and Engineering, and §Department of Biomedical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Taeyong Ahn
- Department of Chemistry, ‡Macromolecular Science and Engineering, and §Department of Biomedical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Isabel D Colón-Bernal
- Department of Chemistry, ‡Macromolecular Science and Engineering, and §Department of Biomedical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Jinhee Kim
- Department of Chemistry, ‡Macromolecular Science and Engineering, and §Department of Biomedical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Mark M Banaszak Holl
- Department of Chemistry, ‡Macromolecular Science and Engineering, and §Department of Biomedical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| |
Collapse
|
41
|
Lee AH, Szczesny SE, Santare MH, Elliott DM. Investigating mechanisms of tendon damage by measuring multi-scale recovery following tensile loading. Acta Biomater 2017; 57:363-372. [PMID: 28435080 PMCID: PMC6688648 DOI: 10.1016/j.actbio.2017.04.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 04/07/2017] [Accepted: 04/11/2017] [Indexed: 01/28/2023]
Abstract
Tendon pathology is associated with damage. While tendon damage is likely initiated by mechanical loading, little is known about the specific etiology. Damage is defined as an irreversible change in the microstructure that alters the macroscopic mechanical parameters. In tendon, the link between mechanical loading and microstructural damage, resulting in macroscopic changes, is not fully elucidated. In addition, tendon damage at the macroscale has been proposed to initiate when tendon is loaded beyond a strain threshold, yet the metrics to define the damage threshold are not determined. We conducted multi-scale mechanical testing to investigate the mechanism of tendon damage by simultaneously quantifying macroscale mechanical and microstructural changes. At the microscale, we observe full recovery of the fibril strain and only partial recovery of the interfibrillar sliding, indicating that the damage initiates at the interfibrillar structures. We show that non-recoverable sliding is a mechanism for tendon damage and is responsible for the macroscale decreased linear modulus and elongated toe-region observed at the fascicle-level, and these macroscale properties are appropriate metrics that reflect tendon damage. We concluded that the inflection point of the stress-strain curve represents the damage threshold and, therefore, may be a useful parameter for future studies. Establishing the mechanism of damage at multiple length scales can improve prevention and rehabilitation strategies for tendon pathology. STATEMENT OF SIGNIFICANCE Tendon pathology is associated with mechanically induced damage. Damage, as defined in engineering, is an irreversible change in microstructure that alters the macroscopic mechanical properties. Although microstructural damage and changes to macroscale mechanics are likely, this link to microstructural change was not yet established. We conducted multiscale mechanical testing to investigate the mechanism of tendon damage by simultaneously quantifying macroscale mechanical and microstructural changes. We showed that non-recoverable sliding between collagen fibrils is a mechanism for tendon damage. Establishing the mechanism of damage at multiple length scales can improve prevention and rehabilitation strategies for tendon pathology.
Collapse
Affiliation(s)
- Andrea H Lee
- Department of Biomedical Engineering, University of Delaware, United States
| | - Spencer E Szczesny
- Department of Orthopaedic Surgery, University of Pennsylvania, United States
| | - Michael H Santare
- Department of Mechanical Engineering, University of Delaware, United States
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, United States.
| |
Collapse
|
42
|
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.
Collapse
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
| |
Collapse
|
43
|
Mersmann F, Charcharis G, Bohm S, Arampatzis A. Muscle and Tendon Adaptation in Adolescence: Elite Volleyball Athletes Compared to Untrained Boys and Girls. Front Physiol 2017; 8:417. [PMID: 28670285 PMCID: PMC5472702 DOI: 10.3389/fphys.2017.00417] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 05/30/2017] [Indexed: 11/17/2022] Open
Abstract
Though the plasticity of human tendons is well explored in adults, it is still unknown how superimposed mechanical loading by means of athletic training affects the properties of tendons during maturation. Due to the increased responsiveness of muscle to mechanical loading, adolescence is an important phase to investigate the effects of training on the mechanical properties of tendons. Hence, in the present study we compared vastus lateralis (VL) architecture, muscle strength of the knee extensor muscles and patellar tendon mechanical properties of male and female adolescent elite athletes to untrained boys and girls. Twenty-one adolescent volleyball athletes (A; 16.7 ± 1 years; 12 boys, 9 girls) and 24 similar-aged controls (C; 16.7 ± 1 years; 12 boys and girls, respectively) performed maximum isometric contractions on a dynamometer for the assessment of muscle strength and, by integrating ultrasound imaging, patellar tendon mechanical properties. Respective joint moments were calculated using an inverse dynamics approach and an electromyography-based estimation of antagonistic contribution. Additionally, the VL pennation angle, fascicle length and muscle-thickness were determined in the inactive state by means of ultrasound. Adolescent athletes produced significantly greater knee extension moments (normalized to body mass) compared to controls (A: 4.23 ± 0.80 Nm/kg, C: 3.57 ± 0.67 Nm/kg; p = 0.004), and showed greater VL thickness and pennation angle (+38% and +27%; p < 0.001). Tendon stiffness (normalized to rest length) was also significantly higher in athletes (A: 86.0 ± 27.1 kN/strain, C: 70.2 ± 18.8 kN/strain; p = 0.04), yet less pronounced compared to tendon force (A: 5785 ± 1146 N, C: 4335 ± 1015 N; p < 0.001), which resulted in higher levels of tendon strain during maximum contractions in athletes (A: 8.0 ± 1.9%, C: 6.4 ± 1.8%; p = 0.008). We conclude that athletic volleyball training provides a more efficient stimulus for muscle compared to tendon adaptation, which results in an increased demand placed upon the tendon by the working muscle in adolescent volleyball athletes. Besides implications for sport performance, these findings might have important consequences for the risk of tendon overuse injury.
Collapse
Affiliation(s)
- Falk Mersmann
- Department of Training and Movement Sciences, Humboldt-Universität zu BerlinBerlin, Germany.,Berlin School of Movement ScienceBerlin, Germany
| | - Georgios Charcharis
- Department of Training and Movement Sciences, Humboldt-Universität zu BerlinBerlin, Germany.,Berlin School of Movement ScienceBerlin, Germany
| | - Sebastian Bohm
- Department of Training and Movement Sciences, Humboldt-Universität zu BerlinBerlin, Germany.,Berlin School of Movement ScienceBerlin, Germany
| | - Adamantios Arampatzis
- Department of Training and Movement Sciences, Humboldt-Universität zu BerlinBerlin, Germany.,Berlin School of Movement ScienceBerlin, Germany
| |
Collapse
|
44
|
Zitnay JL, Li Y, Qin Z, San BH, Depalle B, Reese SP, Buehler MJ, Yu SM, Weiss JA. Molecular level detection and localization of mechanical damage in collagen enabled by collagen hybridizing peptides. Nat Commun 2017; 8:14913. [PMID: 28327610 PMCID: PMC5364439 DOI: 10.1038/ncomms14913] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/14/2017] [Indexed: 02/06/2023] Open
Abstract
Mechanical injury to connective tissue causes changes in collagen structure and material behaviour, but the role and mechanisms of molecular damage have not been established. In the case of mechanical subfailure damage, no apparent macroscale damage can be detected, yet this damage initiates and potentiates in pathological processes. Here, we utilize collagen hybridizing peptide (CHP), which binds unfolded collagen by triple helix formation, to detect molecular level subfailure damage to collagen in mechanically stretched rat tail tendon fascicle. Our results directly reveal that collagen triple helix unfolding occurs during tensile loading of collagenous tissues and thus is an important damage mechanism. Steered molecular dynamics simulations suggest that a likely mechanism for triple helix unfolding is intermolecular shearing of collagen α-chains. Our results elucidate a probable molecular failure mechanism associated with subfailure injuries, and demonstrate the potential of CHP targeting for diagnosis, treatment and monitoring of tissue disease and injury. Collagen denaturation is thought to occur during tissue mechanical damage, but its role in damage initiation is still unclear. Here, the authors use a collagen hybridizing peptide to provide insights into the molecular mechanisms leading to collagen unfolding during tendon mechanical stretch.
Collapse
Affiliation(s)
- Jared L Zitnay
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA.,Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah 84112, USA
| | - Yang Li
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA
| | - Zhao Qin
- Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Boi Hoa San
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA
| | - Baptiste Depalle
- Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Shawn P Reese
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA.,Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah 84112, USA
| | - Markus J Buehler
- Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - S Michael Yu
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA.,Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah 84112, USA
| | - Jeffrey A Weiss
- Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112, USA.,Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah 84112, USA.,Department of Orthopedics, University of Utah, Salt Lake City, Utah 84108, USA
| |
Collapse
|
45
|
Svensson RB, Herchenhan A, Starborg T, Larsen M, Kadler KE, Qvortrup K, Magnusson SP. Evidence of structurally continuous collagen fibrils in tendons. Acta Biomater 2017; 50:293-301. [PMID: 28063986 DOI: 10.1016/j.actbio.2017.01.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 12/05/2016] [Accepted: 01/03/2017] [Indexed: 11/18/2022]
Abstract
Tendons transmit muscle-generated force through an extracellular matrix of aligned collagen fibrils. The force applied by the muscle at one end of a microscopic fibril has to be transmitted through the macroscopic length of the tendon by mechanisms that are poorly understood. A key element in this structure-function relationship is the collagen fibril length. During embryogenesis short fibrils are produced but they grow rapidly with maturation. There is some controversy regarding fibril length in adult tendon, with mechanical data generally supporting discontinuity while structural investigations favor continuity. This study initially set out to trace the full length of individual fibrils in adult human tendons, using serial block face-scanning electron microscopy. But even with this advanced technique the required length could not be covered. Instead a statistical approach was used on a large volume of fibrils in shorter image stacks. Only a single end was observed after tracking 67.5mm of combined fibril lengths, in support of fibril continuity. To shed more light on this observation, the full length of a short tendon (mouse stapedius, 125μm) was investigated and continuity of individual fibrils was confirmed. In light of these results, possible mechanisms that could reconcile the opposing findings on fibril continuity are discussed. STATEMENT OF SIGNIFICANCE Connective tissues hold all parts of the body together and are mostly constructed from thin threads of the protein collagen (called fibrils). Connective tissues provide mechanical strength and one of the most demanding tissues in this regard are tendons, which transmit the forces generated by muscles. The length of the collagen fibrils is essential to the mechanical strength and to the type of damage the tissue may experience (slippage of short fibrils or breakage of longer ones). This in turn is important for understanding the repair processes after such damage occurs. Currently the issue of fibril length is contentious, but this study provides evidence that the fibrils are extremely long and likely continuous.
Collapse
Affiliation(s)
- Rene B Svensson
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Andreas Herchenhan
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tobias Starborg
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Michael Larsen
- Core Facility for Integrated Microscopy, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Karl E Kadler
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Klaus Qvortrup
- Core Facility for Integrated Microscopy, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - S Peter Magnusson
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
46
|
Maciel D, Veres SP, Kreuzer HJ, Kreplak L. Quantitative phase measurements of tendon collagen fibres. JOURNAL OF BIOPHOTONICS 2017; 10:111-117. [PMID: 26824333 DOI: 10.1002/jbio.201500263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/18/2015] [Accepted: 12/22/2015] [Indexed: 06/05/2023]
Abstract
Collagen is the main component of structural mammalian tissues. In tendons, collagen is arranged into fibrils with diameters ranging from 30 nm to 500 nm. These fibrils are further assembled into fibres several micrometers in diameter. Upon excessive thermal or mechanical stress, damage may occur in tendons at all levels of the structural hierarchy. At the fibril level, reported damage includes swelling and the appearance of discrete sites of plastic deformation that are best observed at the nanometer-scale using, for example, scanning electron microscopy. In this paper, digital in-line holographic microscopy is used for quantitative phase imaging to measure both the refractive index and diameter of collagen fibres in a water suspension in the native state, after thermal treatments, and after mechanical overload. Fibres extracted from tendons and subsequently exposed to 70 °C for 5, 15, or 30 minutes show a significant decrease in refractive index and an increase in diameter. A significant increase in refractive index is also observed for fibres extracted from tendons that were subjected to five tensile overload cycles.
Collapse
Affiliation(s)
- Dylan Maciel
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Samuel P Veres
- Division of Engineering, Saint Mary's University, Halifax, NS, B3H 3C3, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Hans Juergen Kreuzer
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, B3H 4R2, Canada
| |
Collapse
|
47
|
Herod TW, Chambers NC, Veres SP. Collagen fibrils in functionally distinct tendons have differing structural responses to tendon rupture and fatigue loading. Acta Biomater 2016; 42:296-307. [PMID: 27321189 DOI: 10.1016/j.actbio.2016.06.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 06/03/2016] [Accepted: 06/10/2016] [Indexed: 12/24/2022]
Abstract
UNLABELLED In this study we investigate relationships between the nanoscale structure of collagen fibrils and the macroscale functional response of collagenous tissues. To do so, we study two functionally distinct classes of tendons, positional tendons and energy storing tendons, using a bovine forelimb model. Molecular-level assessment using differential scanning calorimetry (DSC), functional crosslink assessment using hydrothermal isometric tension (HIT) analysis, and ultrastructural assessment using scanning electron microscopy (SEM) were used to study undamaged, ruptured, and cyclically loaded samples from the two tendon types. HIT indicated differences in both crosslink type and crosslink density, with flexor tendons having more thermally stable crosslinks than the extensor tendons (higher TFmax of >90 vs. 75.1±2.7°C), and greater total crosslink density than the extensor tendons (higher t1/2 of 11.5±1.9 vs. 3.5±1.0h after NaBH4 treatment). Despite having a lower crosslink density than flexor tendons, extensor tendons were significantly stronger (37.6±8.1 vs. 23.1±7.7MPa) and tougher (14.3±3.6 vs. 6.8±3.4MJ/m(3)). SEM showed that collagen fibrils in the tougher, stronger extensor tendons were able to undergo remarkable levels of plastic deformation in the form of discrete plasticity, while those in the flexor tendons were not able to plastically deform. When cyclically loaded, collagen fibrils in extensor tendons accumulated fatigue damage rapidly in the form of kink bands, while those in flexor tendons did not accumulate significant fatigue damage. The results demonstrate that collagen fibrils in functionally distinct tendons respond differently to mechanical loading, and suggests that fibrillar collagens may be subject to a strength vs. fatigue resistance tradeoff. STATEMENT OF SIGNIFICANCE Collagen fibrils-nanoscale biological cables-are the fundamental load-bearing elements of all structural human tissues. While all collagen fibrils share common features, such as being composed of a precise quarter-staggered polymeric arrangement of triple-helical collagen molecules, their structure can vary significantly between tissue types, and even between different anatomical structures of the same tissue type. To understand normal function, homeostasis, and disease of collagenous tissues requires detailed knowledge of collagen fibril structure-function. Using anatomically proximate but structurally distinct tendons, we show that collagen fibrils in functionally distinct tendons have differing susceptibilities to damage under both tensile overload and cyclic fatigue loading. Our results suggest that the structure of collagen fibrils may lead to a strength versus fatigue resistance tradeoff, where high strength is gained at the expense of fatigue resistance, and vice versa.
Collapse
Affiliation(s)
- Tyler W Herod
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Neil C Chambers
- Division of Engineering, Saint Mary's University, Halifax, Nova Scotia, Canada
| | - Samuel P Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; Division of Engineering, Saint Mary's University, Halifax, Nova Scotia, Canada.
| |
Collapse
|
48
|
Quigley AS, Veres SP, Kreplak L. Bowstring Stretching and Quantitative Imaging of Single Collagen Fibrils via Atomic Force Microscopy. PLoS One 2016; 11:e0161951. [PMID: 27598334 PMCID: PMC5012574 DOI: 10.1371/journal.pone.0161951] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 08/15/2016] [Indexed: 12/31/2022] Open
Abstract
Collagen is the primary structural protein in animals. Serving as nanoscale biological ropes, collagen fibrils are responsible for providing strength to a variety of connective tissues such as tendon, skin, and bone. Understanding structure-function relationships in collagenous tissues requires the ability to conduct a variety of mechanical experiments on single collagen fibrils. Though significant advances have been made, certain tests are not possible using the techniques currently available. In this report we present a new atomic force microscopy (AFM) based method for tensile manipulation and subsequent nanoscale structural assessment of single collagen fibrils. While the method documented here cannot currently capture force data during loading, it offers the great advantage of allowing structural assessment after subrupture loading. To demonstrate the utility of this technique, we describe the results of 23 tensile experiments in which collagen fibrils were loaded to varying levels of strain and subsequently imaged in both the hydrated and dehydrated states. We show that following a dehydration-rehydration cycle (necessary for sample preparation), fibrils experience an increase in height and decrease in radial modulus in response to one loading-unloading cycle to strain <5%. This change is not altered by a second cycle to strain >5%. In fibril segments that ruptured during their second loading cycle, we show that the fibril structure is affected away from the rupture site in the form of discrete permanent deformations. By comparing the severity of select damage sites in both hydrated and dehydrated conditions, we demonstrate that dehydration masks damage features, leading to an underestimate of the degree of structural disruption. Overall, the method shows promise as a powerful tool for the investigation of structure-function relationships in nanoscale fibrous materials.
Collapse
Affiliation(s)
- Andrew S. Quigley
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada
| | - Samuel P. Veres
- School of Biomedical Engineering, Dalhousie University, Halifax, Canada
- Division of Engineering, Saint Mary’s University, Halifax, Canada
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, Canada
- * E-mail:
| |
Collapse
|
49
|
Baldwin SJ, Kreplak L, Lee JM. Characterization via atomic force microscopy of discrete plasticity in collagen fibrils from mechanically overloaded tendons: Nano-scale structural changes mimic rope failure. J Mech Behav Biomed Mater 2016; 60:356-366. [DOI: 10.1016/j.jmbbm.2016.02.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/22/2016] [Accepted: 02/03/2016] [Indexed: 10/22/2022]
|
50
|
Nanomechanical mapping of hydrated rat tail tendon collagen I fibrils. Biophys J 2015; 107:1794-1801. [PMID: 25418160 DOI: 10.1016/j.bpj.2014.09.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 08/01/2014] [Accepted: 09/03/2014] [Indexed: 12/11/2022] Open
Abstract
Collagen fibrils play an important role in the human body, providing tensile strength to connective tissues. These fibrils are characterized by a banding pattern with a D-period of 67 nm. The proposed origin of the D-period is the internal staggering of tropocollagen molecules within the fibril, leading to gap and overlap regions and a corresponding periodic density fluctuation. Using an atomic force microscope high-resolution modulus maps of collagen fibril segments, up to 80 μm in length, were acquired at indentation speeds around 10(5) nm/s. The maps revealed a periodic modulation corresponding to the D-period as well as previously undocumented micrometer scale fluctuations. Further analysis revealed a 4/5, gap/overlap, ratio in the measured modulus providing further support for the quarter-staggered model of collagen fibril axial structure. The modulus values obtained at indentation speeds around 10(5) nm/s are significantly larger than those previously reported. Probing the effect of indentation speed over four decades reveals two distinct logarithmic regimes of the measured modulus and point to the existence of a characteristic molecular relaxation time around 0.1 ms. Furthermore, collagen fibrils exposed to temperatures between 50 and 62°C and cooled back to room temperature show a sharp decrease in modulus and a sharp increase in fibril diameter. This is also associated with a disappearance of the D-period and the appearance of twisted subfibrils with a pitch in the micrometer range. Based on all these data and a similar behavior observed for cross-linked polymer networks below the glass transition temperature, we propose that collagen I fibrils may be in a glassy state while hydrated.
Collapse
|