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Blunt KM, Bentkowski BN, Milliron E, Cavendish P, Qin C, Magnussen RA, Stoodley P, Flanigan DC. Influence of Staphylococcus epidermidis on Collagen Crimp Patterns of Soft Tissue Allograft. Am J Sports Med 2023; 51:2701-2710. [PMID: 37449681 DOI: 10.1177/03635465231181649] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
BACKGROUND Postoperative infections, commonly from Staphylococcus epidermidis, may result in anterior cruciate ligament graft failure and necessitate revision surgery. In biomechanical studies, S. epidermidis has been shown to establish biofilms on tendons and reduce graft strength. PURPOSE/HYPOTHESIS The goal of this study was to determine the effect of bacterial bioburden on the collagen structure of tendon. It was hypothesized that an increase in S. epidermidis biofilm would compromise tendon crimp, a pattern necessary for mechanical integrity, of soft tissue allografts. STUDY DESIGN Controlled laboratory study. METHODS Cultures of S. epidermidis were used to inoculate tibialis anterior cadaveric tendons. Conditions assessed included 5 × 105 colony-forming units or concentrated spent media from culture (no living bacteria). Incubation times of 30 minutes, 3 hours, 6 hours, and 24 hours were utilized. Second-harmonic generation imaging allowed for visualization of collagen autofluorescence. Crimp lengths were determined using ImageJ and compared based on incubation time. RESULTS Incubation time positively correlated with increasing S. epidermidis bioburden. Both fine and coarse crimp patterns lengthened with increasing incubation time. Significant coarse crimp changes were observed after only 30-minute incubations (P < .029), whereas significant fine crimp lengthening occurred after 6 hours (P < .0001). No changes in crimp length were identified after incubation in media lacking living bacteria. CONCLUSION The results of this study demonstrate that exposure to S. epidermidis negatively affects collagen crimp structure. Structural alterations at the collagen fiber level occur within 30 minutes of exposure to media containing S. epidermidis. CLINICAL RELEVANCE Our study highlights the need for antimicrobial precautions to prevent graft colonization and maximize graft mechanical strength.
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Affiliation(s)
- Koral M Blunt
- The Ohio State University College of Medicine, Columbus, Ohio, USA
| | | | - Eric Milliron
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Parker Cavendish
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Charles Qin
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Robert A Magnussen
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
- The Ohio State University Sports Medicine Research Institute, Columbus, Ohio, USA
| | - Paul Stoodley
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
| | - David C Flanigan
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
- The Ohio State University Sports Medicine Research Institute, Columbus, Ohio, USA
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Mienaltowski MJ, Gonzales NL, Beall JM, Pechanec MY. Basic Structure, Physiology, and Biochemistry of Connective Tissues and Extracellular Matrix Collagens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1348:5-43. [PMID: 34807414 DOI: 10.1007/978-3-030-80614-9_2] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The physiology of connective tissues like tendons and ligaments is highly dependent upon the collagens and other such extracellular matrix molecules hierarchically organized within the tissues. By dry weight, connective tissues are mostly composed of fibrillar collagens. However, several other forms of collagens play essential roles in the regulation of fibrillar collagen organization and assembly, in the establishment of basement membrane networks that provide support for vasculature for connective tissues, and in the formation of extensive filamentous networks that allow for cell-extracellular matrix interactions as well as maintain connective tissue integrity. The structures and functions of these collagens are discussed in this chapter. Furthermore, collagen synthesis is a multi-step process that includes gene transcription, translation, post-translational modifications within the cell, triple helix formation, extracellular secretion, extracellular modifications, and then fibril assembly, fibril modifications, and fiber formation. Each step of collagen synthesis and fibril assembly is highly dependent upon the biochemical structure of the collagen molecules created and how they are modified in the cases of development and maturation. Likewise, when the biochemical structures of collagens or are compromised or these molecules are deficient in the tissues - in developmental diseases, degenerative conditions, or injuries - then the ultimate form and function of the connective tissues are impaired. In this chapter, we also review how biochemistry plays a role in each of the processes involved in collagen synthesis and assembly, and we describe differences seen by anatomical location and region within tendons. Moreover, we discuss how the structures of the molecules, fibrils, and fibers contribute to connective tissue physiology in health, and in pathology with injury and repair.
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Affiliation(s)
| | - Nicole L Gonzales
- Department of Animal Science, University of California Davis, Davis, CA, USA
| | - Jessica M Beall
- Department of Animal Science, University of California Davis, Davis, CA, USA
| | - Monica Y Pechanec
- Department of Animal Science, University of California Davis, Davis, CA, USA
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Liu J, Xu MY, Wu J, Zhang H, Yang L, Lun DX, Hu YC, Liu B. Picrosirius-Polarization Method for Collagen Fiber Detection in Tendons: A Mini-Review. Orthop Surg 2021; 13:701-707. [PMID: 33689233 PMCID: PMC8126917 DOI: 10.1111/os.12627] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 01/14/2020] [Accepted: 01/14/2020] [Indexed: 12/31/2022] Open
Abstract
Although the structure and composition of collagen have been studied by polarized light microscopy since the early 19th century, many studies and reviews have paid little or no attention to the morphological problems of histopathological diagnosis. The morphology of collagen fibers is critical in guiding mechanical and biological properties in both normal and pathological tendons. Highlighting the organization and spatial distribution of tendon‐containing collagen fibers can be very useful for visualizing a tendon's ultrastructure, biochemical and indirect mechanical properties, which benefits other researchers and clinicians. Picrosirius red (PSR) staining, relying on the birefringence of collagen fibers, is one of the best understood histochemical methods that can highly and specifically underline fibers better than other common staining techniques when combined with polarized light microscopy (PLM). Polarized light microscopy provides complementary information about collagen fibers, such as orientation, type and spatial distribution, which is important for a comprehensive assessment of collagen alteration in a tendon. Here, this brief review serves as a simplistic and important primer to research developments in which differential staining of collagen types by the Picrosirius‐polarization method is increasing in diverse studies of the medical field, mainly in the assessment of the morphology, spatial distribution, and content of collagen in tendons.
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Affiliation(s)
- Jie Liu
- Tianjin Medical University, Tianjin, China
| | | | - Jing Wu
- Center for Medical Device Evaluation NMPA, Beijing, China
| | | | - Li Yang
- Tianjin Hospital, Tianjin, China
| | | | | | - Bin Liu
- Center for Medical Device Evaluation NMPA, Beijing, China
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Redler A, Miglietta S, Monaco E, Matassa R, Relucenti M, Daggett M, Ferretti A, Familiari G. Ultrastructural Assessment of the Anterolateral Ligament. Orthop J Sports Med 2019; 7:2325967119887920. [PMID: 31897411 PMCID: PMC6920591 DOI: 10.1177/2325967119887920] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Background: The anterolateral ligament (ALL) has been identified as a structure on the
lateral side of the knee, but debate exists regarding whether it is a
capsular thickening or a ligament. Hypothesis: A detailed ultrastructural characterization of the ALL and its ultrastructure
collagen arrangement will reveal it more closely resembles ligamentous
tissue than joint capsule. Study Design: Descriptive laboratory study. Methods: Eight paired knee samples from 4 fresh-frozen male cadavers were used for
this study. Samples were harvested from the ALL, the joint capsule, and the
medial collateral ligament (MCL). All samples were evaluated with light
microscopy (LM), transmission electron microscopy (TEM), and variable
pressure scanning electron microscopy (VP-SEM). With LM, the 3 tissues were
analyzed and their morphology described. With TEM, the ultrastructure and
collagen characteristics were quantified and compared among specimens. Then,
the 3-dimensional characteristics were compared with VP-SEM. Results: Ultrastructure analysis demonstrated similar morphology between the ALL and
MCL, with significant differences in these 2 structures as compared with the
joint capsule. On LM, the ALL and MCL were characterized by the presence of
a dense collagen fiber oriented in the longitudinal and transversal
directions of the fiber bundles, while the joint capsule was found to have a
more disorganized architecture. On TEM, the collagen fibers of the ALL and
MCL demonstrated similar ultrastructural morphology, with both having
collagen fibers in parallel, longitudinal alignment. A quantitative analysis
was also performed, with the mean (± SD) diameter of fibrils in the ALL and
MCL being 80 ± 2.66 nm and 150 ± 3.35 nm, respectively (all
P < .001). The VP-SEM highlighted that ALL and MCL
morphology demonstrated arrangements of fiber bundles that are densely
packed and organized, in contrast to the disorganized fibers of the joint
capsule. Conclusion: The ALL and MCL have comparable ultrastructures that are distinctly different
from the joint capsule, as visualized on LM, TEM, and VP-SEM. Clinical Relevance: The ALL should be considered a distinctive structure of the knee, although
strictly connected to the surrounding capsule.
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Affiliation(s)
- Andrea Redler
- Orthopaedic Unit and Kirk Kilgour Sports Injury Centre, S. Andrea Hospital, University of Rome Sapienza, Rome, Italy.,Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University of Rome Sapienza, Rome, Italy
| | - Selenia Miglietta
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University of Rome Sapienza, Rome, Italy
| | - Edoardo Monaco
- Orthopaedic Unit and Kirk Kilgour Sports Injury Centre, S. Andrea Hospital, University of Rome Sapienza, Rome, Italy
| | - Roberto Matassa
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University of Rome Sapienza, Rome, Italy
| | - Michela Relucenti
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University of Rome Sapienza, Rome, Italy
| | - Matthew Daggett
- Kansas City University of Medicine and Biosciences, Kansas City, Missouri, USA
| | - Andrea Ferretti
- Orthopaedic Unit and Kirk Kilgour Sports Injury Centre, S. Andrea Hospital, University of Rome Sapienza, Rome, Italy
| | - Giuseppe Familiari
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University of Rome Sapienza, Rome, Italy
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Lee W, Rahman H, Kersh ME, Toussaint KC. Application of quantitative second-harmonic generation microscopy to posterior cruciate ligament for crimp analysis studies. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:46009. [PMID: 28451692 DOI: 10.1117/1.jbo.22.4.046009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 04/11/2017] [Indexed: 05/03/2023]
Abstract
We use second-harmonic generation (SHG) microscopy to quantitatively characterize collagen fiber crimping in the posterior cruciate ligament (PCL). The obtained SHG images are utilized to define three distinct categories of crimp organization in the PCL. Using our previously published spatial-frequency analysis, we develop a simple algorithm to quantitatively distinguish the various crimp patterns. In addition, SHG microscopy reveals both the three-dimensional structural variation in some PCL crimp patterns as well as an underlying helicity in these patterns that have mainly been observed using electron microscopy. Our work highlights how SHG microscopy could potentially be used to link the fibrous structural information in the PCL to its mechanical properties.
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Affiliation(s)
- Woowon Lee
- University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Urbana, Illinois, United StatesbUniversity of Illinois at Urbana-Champaign, PROBE Lab, Urbana, Illinois, United States
| | - Hafizur Rahman
- University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Urbana, Illinois, United States
| | - Mariana E Kersh
- University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Urbana, Illinois, United States
| | - Kimani C Toussaint
- University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering, Urbana, Illinois, United StatesbUniversity of Illinois at Urbana-Champaign, PROBE Lab, Urbana, Illinois, United StatescUniversity of Illinois at Urbana-Champaign, Department of Electrical and Computer Engineering, Urbana, Illinois, United StatesdUniversity of Illinois at Urbana-Champaign, Department of Bioengineering, Urbana, Illinois, United States
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Zhang S, Cao X, Stablow AM, Shenoy VB, Winkelstein BA. Tissue Strain Reorganizes Collagen With a Switchlike Response That Regulates Neuronal Extracellular Signal-Regulated Kinase Phosphorylation In Vitro: Implications for Ligamentous Injury and Mechanotransduction. J Biomech Eng 2016; 138:021013. [PMID: 26549105 DOI: 10.1115/1.4031975] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Indexed: 12/26/2022]
Abstract
Excessive loading of ligaments can activate the neural afferents that innervate the collagenous tissue, leading to a host of pathologies including pain. An integrated experimental and modeling approach was used to define the responses of neurons and the surrounding collagen fibers to the ligamentous matrix loading and to begin to understand how macroscopic deformation is translated to neuronal loading and signaling. A neuron-collagen construct (NCC) developed to mimic innervation of collagenous tissue underwent tension to strains simulating nonpainful (8%) or painful ligament loading (16%). Both neuronal phosphorylation of extracellular signal-regulated kinase (ERK), which is related to neuroplasticity (R2 ≥ 0.041; p ≤ 0.0171) and neuronal aspect ratio (AR) (R2 ≥ 0.250; p < 0.0001), were significantly correlated with tissue-level strains. As NCC strains increased during a slowly applied loading (1%/s), a "switchlike" fiber realignment response was detected with collagen reorganization occurring only above a transition point of 11.3% strain. A finite-element based discrete fiber network (DFN) model predicted that at bulk strains above the transition point, heterogeneous fiber strains were both tensile and compressive and increased, with strains in some fibers along the loading direction exceeding the applied bulk strain. The transition point identified for changes in collagen fiber realignment was consistent with the measured strain threshold (11.7% with a 95% confidence interval of 10.2-13.4%) for elevating ERK phosphorylation after loading. As with collagen fiber realignment, the greatest degree of neuronal reorientation toward the loading direction was observed at the NCC distraction corresponding to painful loading. Because activation of neuronal ERK occurred only at strains that produced evident collagen fiber realignment, findings suggest that tissue strain-induced changes in the micromechanical environment, especially altered local collagen fiber kinematics, may be associated with mechanotransduction signaling in neurons.
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Zaffagnini S, Marcheggiani Muccioli GM, Franchi M, Bacchelli B, Grassi A, Agati P, Quaranta M, Marcacci M, De Pasquale V. Collagen fibre and fibril ultrastructural arrangement of the superficial medial collateral ligament in the human knee. Knee Surg Sports Traumatol Arthrosc 2015; 23:3674-82. [PMID: 25261220 DOI: 10.1007/s00167-014-3276-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 08/26/2014] [Indexed: 11/26/2022]
Abstract
PURPOSE The aim of the study was to investigate the collagen fibre ultrastructural arrangement and collagen fibril diameters in the superficial medial collateral ligament (sMCL) in the human knee. Considering sMCL's distinctive functions at different angles of knee flexion, it was hypothesized a significant difference between the collagen fibril diameters of each portion of the sMCL. METHODS Fourteen sMCL from seven fresh males (by chance because of the availability) cadavers (median age 40 years, range 34-59 years) were harvested within 12 h of death. sMCLs were separated into two orders of regions for analysis. The first order (divisions) was anterior, central and posterior. Thereafter, each division was split into three regions (femoral, intermediate and tibial), generating nine portions. One sMCL from each cadaver was used for transmission electron microscopy (TEM) and morphometric analyses, whereas the contralateral sMCL was processed for light microscopy (LM) or scanning electron microscopy (SEM). RESULTS LM and SEM analyses showed a complex tridimensional architecture, with the presence of wavy collagen fibres or crimps. TEM analysis showed significant differences in median collagen fibril diameter among portions inside the anterior, central and posterior division of the sMCL (p < 0.0001 within each division). Significant differences were also present among the median [interquartile range] collagen fibril diameters of anterior (39.4 [47.8-32.9]), central (38.5 [44.4-34.0]) and posterior (41.7 [52.2-35.4]) division (p = 0.0001); femoral (38.2 [45.0-32.7]), intermediate (40.3 [47.3-36.1]) and tibial (40.7 [55.0-32.2]) region (p = 0.0001). CONCLUSIONS Human sMCL showed a complex architecture that allows restraining different knee motions at different angles of knee flexion. The posterior division of sMCL accounted for the largest median collagen fibril diameter. The femoral region of sMCL accounted for the smallest median collagen fibril diameter. The presence of crimps in the medial collateral ligament, previously identified in the rat, was confirmed in humans (taking into consideration differences between these two species).
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Affiliation(s)
| | | | - Marco Franchi
- Faculty of Sport Sciences, University of Bologna, Bologna, Italy.
| | | | | | - Patrizia Agati
- Statistical Science Department, University of Bologna, Bologna, Italy.
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Mienaltowski MJ, Birk DE. Structure, physiology, and biochemistry of collagens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 802:5-29. [PMID: 24443018 DOI: 10.1007/978-94-007-7893-1_2] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Tendons and ligaments are connective tissues that guide motion, share loads, and transmit forces in a manner that is unique to each as well as the anatomical site and biomechanical stresses to which they are subjected. Collagens are the major molecular components of both tendons and ligaments. The hierarchical structure of tendon and its functional properties are determined by the collagens present, as well as their supramolecular organization. There are 28 different types of collagen that assemble into a variety of supramolecular structures. The assembly of specific supramolecular structures is dependent on the interaction with other matrix molecules as well as the cellular elements. Multiple suprastructural assemblies are integrated to form the functional tendon/ligament. This chapter begins with a discussion of collagen molecules. This is followed by a definition of the supramolecular structures assembled by different collagen types. The general principles involved in the assembly of collagen-containing suprastructures are presented focusing on the regulation of tendon collagen fibrillogenesis. Finally, site-specific differences are discussed. While generalizations can be made, differences exist between different tendons as well as between tendons and ligaments. Compositional differences will impact structure that in turn will determine functional differences. Elucidation of the unique physiology and pathophysiology of different tendons and ligaments will require an appreciation of the role compositional differences have on collagen suprastructural assembly, tissue organization, and function.
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Affiliation(s)
- Michael J Mienaltowski
- Departments of Molecular Pharmacology & Physiology and Orthopaedics & Sports Medicine, University of South Florida, Morsani College of Medicine, 12901 Bruce B. Downs Blvd., MDC8, Tampa, FL, 33612, USA
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Miller KS, Connizzo BK, Feeney E, Tucker JJ, Soslowsky LJ. Examining differences in local collagen fiber crimp frequency throughout mechanical testing in a developmental mouse supraspinatus tendon model. J Biomech Eng 2012; 134:041004. [PMID: 22667679 PMCID: PMC3632287 DOI: 10.1115/1.4006538] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 03/15/2012] [Accepted: 04/05/2012] [Indexed: 01/06/2023]
Abstract
Crimp morphology is believed to be related to tendon mechanical behavior. While crimp has been extensively studied at slack or nondescript load conditions in tendon, few studies have examined crimp at specific, quantifiable loading conditions. Additionally, the effect of the number of cycles of preconditioning on collagen fiber crimp behavior has not been examined. Further, the dependence of collagen fiber crimp behavior on location and developmental age has not been examined in the supraspinatus tendon. Local collagen fiber crimp frequency is quantified throughout tensile mechanical testing using a flash freezing method immediately following the designated loading protocol. Samples are analyzed quantitatively using custom software and semi-quantitatively using a previously established method to validate the quantitative software. Local collagen fiber crimp frequency values are compared throughout the mechanical test to determine where collagen fiber frequency changed. Additionally, the effect of the number of preconditioning cycles is examined compared to the preload and toe-region frequencies to determine if increasing the number of preconditioning cycles affects crimp behavior. Changes in crimp frequency with age and location are also examined. Decreases in collagen fiber crimp frequency were found at the toe-region at all ages. Significant differences in collagen fiber crimp frequency were found between the preload and after preconditioning points at 28 days. No changes in collagen fiber crimp frequency were found between locations or between 10 and 28 days old. Local collagen fiber crimp frequency throughout mechanical testing in a postnatal developmental mouse SST model was measured. Results confirmed that the uncrimping of collagen fibers occurs primarily in the toe-region and may contribute to the tendon's nonlinear behavior. Additionally, results identified changes in collagen fiber crimp frequency with an increasing number of preconditioning cycles at 28 days, which may have implications on the measurement of mechanical properties and identifying a proper reference configuration.
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Affiliation(s)
- Kristin S Miller
- McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA 19104-6081, USA
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Herchenhan A, Kalson NS, Holmes DF, Hill P, Kadler KE, Margetts L. Tenocyte contraction induces crimp formation in tendon-like tissue. Biomech Model Mechanobiol 2012; 11:449-59. [PMID: 21735243 PMCID: PMC3822867 DOI: 10.1007/s10237-011-0324-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 06/17/2011] [Indexed: 10/18/2022]
Abstract
Tendons are composed of longitudinally aligned collagen fibrils arranged in bundles with an undulating pattern, called crimp. The crimp structure is established during embryonic development and plays a vital role in the mechanical behaviour of tendon, acting as a shock-absorber during loading. However, the mechanism of crimp formation is unknown, partly because of the difficulties of studying tendon development in vivo. Here, we used a 3D cell culture system in which embryonic tendon fibroblasts synthesise a tendon-like construct comprised of collagen fibrils arranged in parallel bundles. Investigations using polarised light microscopy, scanning electron microscopy and fluorescence microscopy showed that tendon constructs contained a regular pattern of wavy collagen fibrils. Tensile testing indicated that this superstructure was a form of embryonic crimp producing a characteristic toe region in the stress-strain curves. Furthermore, contraction of tendon fibroblasts was the critical factor in the buckling of collagen fibrils during the formation of the crimp structure. Using these biological data, a finite element model was built that mimics the contraction of the tendon fibroblasts and monitors the response of the Extracellular matrix. The results show that the contraction of the fibroblasts is a sufficient mechanical impulse to build a planar wavy pattern. Furthermore, the value of crimp wavelength was determined by the mechanical properties of the collagen fibrils and inter-fibrillar matrix. Increasing fibril stiffness combined with constant matrix stiffness led to an increase in crimp wavelength. The data suggest a novel mechanism of crimp formation, and the finite element model indicates the minimum requirements to generate a crimp structure in embryonic tendon.
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Affiliation(s)
- Andreas Herchenhan
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK
| | - Nicholas S. Kalson
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK
| | - David F. Holmes
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK
| | - Patrick Hill
- School of Chemical Engineering and Analytical Science, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Karl E. Kadler
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT UK
| | - Lee Margetts
- High Performance Computing, Research Computing Services, University of Manchester, Devonshire House, Oxford Road, Manchester M13 9PL UK
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