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Ashinsky B, Smith HE, Mauck RL, Gullbrand SE. Intervertebral disc degeneration and regeneration: a motion segment perspective. Eur Cell Mater 2021; 41:370-380. [PMID: 33763848 PMCID: PMC8607668 DOI: 10.22203/ecm.v041a24] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Back and neck pain have become primary reasons for disability and healthcare spending globally. While the causes of back pain are multifactorial, intervertebral disc degeneration is frequently cited as a primary source of pain. The annulus fibrosus (AF) and nucleus pulposus (NP) subcomponents of the disc are common targets for regenerative therapeutics. However, disc degeneration is also associated with degenerative changes to adjacent spinal tissues, and successful regenerative therapies will likely need to consider and address the pathology of adjacent spinal structures beyond solely the disc subcomponents. This review summarises the current state of knowledge in the field regarding associations between back pain, disc degeneration, and degeneration of the cartilaginous and bony endplates, the AF-vertebral body interface, the facet joints and spinal muscles, in addition to a discussion of regenerative strategies for treating pain and degeneration from a whole motion segment perspective.
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Affiliation(s)
| | | | | | - S E Gullbrand
- Corporal Michael J. Crescenz VA Medical Centre, Research, Building 21, Rm A214, 3900 Woodland Ave, Philadelphia, PA 19104,
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2
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Gaul RT, Nolan DR, Ristori T, Bouten CV, Loerakker S, Lally C. Pressure-induced collagen degradation in arterial tissue as a potential mechanism for degenerative arterial disease progression. J Mech Behav Biomed Mater 2020; 109:103771. [DOI: 10.1016/j.jmbbm.2020.103771] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/26/2020] [Accepted: 04/01/2020] [Indexed: 12/12/2022]
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Swanson BT, Creighton D. The degenerative lumbar disc: not a disease, but still an important consideration for OMPT practice: a review of the history and science of discogenic instability. J Man Manip Ther 2020; 28:191-200. [PMID: 32364465 PMCID: PMC8550621 DOI: 10.1080/10669817.2020.1758520] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND A recent AAOMPT position paper was published that opposed the use of the term 'degenerative disc disease' (DDD), in large part because it appears to be a common age-related finding. While common, there are significant physiologic and biomechanical changes that occur as a result of discogenic degeneration, which are relevant to consider during the practice of manual therapy. METHODS A narrative review provides an overview of these considerations, including a historical perspective of discogenic instability, the role of the disc as a pain generator, the basic science of a combined biomechanical and physiologic cycle of degeneration and subsequent discogenic instability, the influence of rotation on the degenerative segment, the implications of these factors for manual therapy practice, and a perspective on an evidence-based treatment approach to patients with concurrent low back pain and discogenic degeneration. CONCLUSIONS As we consider the role of imaging findings such as DDD, we pose the following question: Do our manual interventions reflect the scientifically proven biomechanical aspects of DDD, or have we chosen to ignore the helpful science as we discard the harmful diagnostic label?
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Affiliation(s)
- Brian T. Swanson
- Department of Rehabilitation Sciences, University of Hartford, West Hartford, CT, USA
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4
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Tension in fibrils suppresses their enzymatic degradation - A molecular mechanism for 'use it or lose it'. Matrix Biol 2019; 85-86:34-46. [PMID: 31201857 DOI: 10.1016/j.matbio.2019.06.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 05/31/2019] [Accepted: 06/07/2019] [Indexed: 12/27/2022]
Abstract
Tissue homeostasis depends on a balance of synthesis and degradation of constituent proteins, with turnover of a given protein potentially regulated by its use. Extracellular matrix (ECM) is predominantly composed of fibrillar collagens that exhibit tension-sensitive degradation, which we review here at different levels of hierarchy. Past experiments and recent proteomics measurements together suggest that mechanical strain stabilizes collagen against enzymatic degradation at the scale of tissues and fibrils whereas isolated collagen molecules exhibit a biphasic behavior that depends on load magnitude. Within a Michaelis-Menten framework, collagenases at constant concentration effectively exhibit a low activity on substrate fibrils when the fibrils are strained by tension. Mechanisms of such mechanosensitive regulation are surveyed together with relevant interactions of collagen fibrils with cells.
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Fujii K, Yamazaki M, Kang JD, Risbud MV, Cho SK, Qureshi SA, Hecht AC, Iatridis JC. Discogenic Back Pain: Literature Review of Definition, Diagnosis, and Treatment. JBMR Plus 2019; 3:e10180. [PMID: 31131347 PMCID: PMC6524679 DOI: 10.1002/jbm4.10180] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 10/21/2018] [Accepted: 01/30/2019] [Indexed: 12/11/2022] Open
Abstract
Discogenic back pain is multifactorial; hence, physicians often struggle to identify the underlying source of the pain. As a result, discogenic back pain is often hard to treat—even more so when clinical treatment strategies are of questionable efficacy. Based on a broad literature review, our aim was to define discogenic back pain into a series of more specific and interacting pathologies, and to highlight the need to develop novel approaches and treatment strategies for this challenging and unmet clinical need. Discogenic pain involves degenerative changes of the intervertebral disc, including structural defects that result in biomechanical instability and inflammation. These degenerative changes in intervertebral discs closely intersect with the peripheral and central nervous systems to cause nerve sensitization and ingrowth; eventually central sensitization results in a chronic pain condition. Existing imaging modalities are nonspecific to pain symptoms, whereas discography methods that are more specific have known comorbidities based on intervertebral disc puncture and injection. As a result, alternative noninvasive and specific diagnostic methods are needed to better diagnose and identify specific conditions and sources of pain that can be more directly treated. Currently, there are many treatments/interventions for discogenic back pain. Nevertheless, many surgical approaches for discogenic pain have limited efficacy, thus accentuating the need for the development of novel treatments. Regenerative therapies, such as biologics, cell‐based therapy, intervertebral disc repair, and gene‐based therapy, offer the most promise and have many advantages over current therapies. © 2019 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research
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Affiliation(s)
- Kengo Fujii
- Leni & Peter W. May Department of Orthopaedics Icahn School of Medicine at Mount Sinai New York NY USA.,Department of Orthopaedic Surgery University of Tsukuba Tsukuba Japan
| | - Masashi Yamazaki
- Department of Orthopaedic Surgery University of Tsukuba Tsukuba Japan
| | - James D Kang
- Department of Orthopaedic Surgery Brigham and Women's Hospital Harvard Medical School Boston MA USA
| | - Makarand V Risbud
- Department of Orthopaedic Surgery Sidney Kimmel Medical College Thomas Jefferson University Philadelphia PA USA
| | - Samuel K Cho
- Leni & Peter W. May Department of Orthopaedics Icahn School of Medicine at Mount Sinai New York NY USA
| | - Sheeraz A Qureshi
- Department of Orthopaedic Surgery Hospital for Special Surgery New York NY USA
| | - Andrew C Hecht
- Leni & Peter W. May Department of Orthopaedics Icahn School of Medicine at Mount Sinai New York NY USA
| | - James C Iatridis
- Leni & Peter W. May Department of Orthopaedics Icahn School of Medicine at Mount Sinai New York NY USA
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6
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Chaitow L. New evidence of a dynamic fascial maintenance and self-repair process. J Bodyw Mov Ther 2016; 20:701-703. [DOI: 10.1016/j.jbmt.2016.08.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Internal strain drives spontaneous periodic buckling in collagen and regulates remodeling. Proc Natl Acad Sci U S A 2016; 113:8436-41. [PMID: 27402741 DOI: 10.1073/pnas.1523228113] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Fibrillar collagen, an essential structural component of the extracellular matrix, is remarkably resistant to proteolysis, requiring specialized matrix metalloproteinases (MMPs) to initiate its remodeling. In the context of native fibrils, remodeling is poorly understood; MMPs have limited access to cleavage sites and are inhibited by tension on the fibril. Here, single-molecule recordings of fluorescently labeled MMPs reveal cleavage-vulnerable binding regions arrayed periodically at ∼1-µm intervals along collagen fibrils. Binding regions remain periodic even as they migrate on the fibril, indicating a collective process of thermally activated and self-healing defect formation. An internal strain relief model involving reversible structural rearrangements quantitatively reproduces the observed spatial patterning and fluctuations of defects and provides a mechanism for tension-dependent stabilization of fibrillar collagen. This work identifies internal-strain-driven defects that may have general and widespread regulatory functions in self-assembled biological filaments.
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Susilo ME, Paten JA, Sander EA, Nguyen TD, Ruberti JW. Collagen network strengthening following cyclic tensile loading. Interface Focus 2016; 6:20150088. [DOI: 10.1098/rsfs.2015.0088] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The bulk mechanical properties of tissues are highly tuned to the physiological loads they experience and reflect the hierarchical structure and mechanical properties of their constituent parts. A thorough understanding of the processes involved in tissue adaptation is required to develop multi-scale computational models of tissue remodelling. While extracellular matrix (ECM) remodelling is partly due to the changing cellular metabolic activity, there may also be mechanically directed changes in ECM nano/microscale organization which lead to mechanical tuning. The thermal and enzymatic stability of collagen, which is the principal load-bearing biopolymer in vertebrates, have been shown to be enhanced by force suggesting that collagen has an active role in ECM mechanical properties. Here, we ask how changes in the mechanical properties of a collagen-based material are reflected by alterations in the micro/nanoscale collagen network following cyclic loading. Surprisingly, we observed significantly higher tensile stiffness and ultimate tensile strength, roughly analogous to the effect of work hardening, in the absence of network realignment and alterations to the fibril area fraction. The data suggest that mechanical loading induces stabilizing changes internal to the fibrils themselves or in the fibril–fibril interactions. If such a cell-independent strengthening effect is operational
in vivo
, then it would be an important consideration in any multiscale computational approach to ECM growth and remodelling.
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Affiliation(s)
| | | | - Edward A. Sander
- Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
| | - Thao D. Nguyen
- Mechanical Engineering, Johns Hopkins, Baltimore, MD 21218, USA
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9
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Pathomechanisms of discogenic low back pain in humans and animal models. Spine J 2015; 15:1347-55. [PMID: 24657737 DOI: 10.1016/j.spinee.2013.07.490] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 02/10/2013] [Accepted: 07/25/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Although explored in humans and animal models, the pathomechanisms of discogenic low back pain (LBP) remain unknown. PURPOSE The aim of this study was to review the literature about the pathomechanisms of discogenic LBP. METHODS Animal models of discogenic pain and specimens from degenerated human intervertebral discs (IVDs) have provided clues about the pathomechanisms of discogenic LBP. Painful discs are characterized by a confluence of innervation, inflammation, and mechanical hypermobility. These three possible mechanisms are discussed in this review. RESULTS Animal models and specimens from humans have revealed sensory innervation of lumbar IVDs and sensory nerve ingrowth into the inner layer of IVDs. Cytokines such as tumor necrosis factor-α and interleukins induce this ingrowth. Nerve growth factor has also been recently identified as an inducer of ingrowth. Finally, disc degeneration induces several collagenases; their action results in hypermobility and pain. CONCLUSIONS To treat discogenic LBP, it is important to prevent sensitization of sensory nerve fibers innervating the IVD, to suppress pathogenic increases of cytokines, and to decrease disc hypermobility.
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Abstract
STUDY DESIGN Systematic review of the literature. OBJECTIVE A systematic evaluation of the literature was performed to investigate current nonoperative management of the treatment of discogenic low back pain. SUMMARY OF BACKGROUND DATA Back pain is a major health care concern with up to 39% being discogenic in origin according to one study. Nonoperative therapy is likely to be the initial treatment strategy for discogenic low back pain. METHODS PubMed, EMBASE, and Cochrane Central Register of Controlled Trials were searched for clinical studies evaluating nonoperative methods of treating discogenic back pain that were published between 2000 and 2012. Only prospective randomized controlled studies that compared a nonsurgical intervention with sham or placebo therapy were included. After removal of duplicate citations, a total of 226 articles were initially identified from the search terms. From these, we identified 11 randomized controlled trials (RCTs) from which data analysis was performed. RESULTS The 11 RCTs investigated traction therapy, injections, and ablative techniques. Results from 5 RCTs investigating methylene blue injection, steroid injection, ramus communicans ablation, intradiscal electrothermal therapy, and biacuplasty favored intervention over sham therapy. However, results from the study on methylene blue injections have not been replicated in other RCTs. Evaluation of the selection criteria used in the studies on ramus communicans ablation and intradiscal biacuplasty and a stratified analysis of results from the RCTs on intradiscal electrothermal therapy casts doubt on whether the conclusions from these RCTs can be applied to the general patient population with discogenic pain. CONCLUSION There are few high-quality studies evaluating nonoperative treatments for reducing discogenic low back pain. Although conclusions from several studies favor intervention over sham, it is unclear whether these interventions confer stable long-term benefit. There is some promise in newer modalities such as biacuplasty; however, more inclusive studies need to be performed.
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11
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Abstract
Degradation of fibrillar collagen is critical for tissue maintenance. Yet, understanding collagen catabolism has been challenging partly due to a lack of atomistic picture for its load-dependent conformational dynamics, as both mechanical load and local unfolding of collagen affect its cleavage by matrix metalloproteinase (MMP). We use molecular dynamics simulation to find the most cleavage-prone arrangement of α chains in a collagen triple helix and find amino acids that modulate stability of the MMP cleavage domain depending on the chain registry within the molecule. The native-like state is mechanically inhomogeneous, where the cleavage site interfaces a stiff region and a locally unfolded and flexible region along the molecule. In contrast, a triple helix made of the stable glycine-proline-hydroxyproline motif is uniformly flexible and is dynamically stabilized by short-lived, low-occupancy hydrogen bonds. These results provide an atomistic basis for the mechanics, conformation, and stability of collagen that affect catabolism.
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Affiliation(s)
- Xiaojing Teng
- Department of Biomedical Engineering and ‡Department of Materials Science and Engineering, Texas A&M University , College Station, Texas 77843, United States
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12
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Turner KG, Ahmed N, Santerre JP, Kandel RA. Modulation of annulus fibrosus cell alignment and function on oriented nanofibrous polyurethane scaffolds under tension. Spine J 2014; 14:424-34. [PMID: 24291406 DOI: 10.1016/j.spinee.2013.08.047] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 06/27/2013] [Accepted: 08/23/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Annulus fibrosus (AF), a component of the intervertebral disc (IVD), is always under tension in vivo, a condition that must be taken into consideration when tissue engineering an IVD. Loss of the tensile forces has been implicated in the pathogenesis of disc degeneration characterized by mechanical and structural breakdown of the AF. PURPOSE In this study, we hypothesize that tensile forces modulate cellular and molecular behavior of AF cells grown on nanofibrous scaffolds in vitro. STUDY DESIGN/SETTING Bovine AF cells were seeded onto strained electrospun-aligned nanofibrous polycarbonate urethane (PU) scaffolds. Tension was either maintained throughout the culture duration (monotonic) or removed after 24 hours (relaxed). METHODS The effect of tension on AF cells cultured on PU scaffolds was evaluated over 7 days by scanning electron microscopy, biochemical assays, immunofluorescence microscopy, and quantitative polymerase chain reaction. RESULTS Cells grown on the relaxed scaffold were significantly more proliferative, synthesized more collagen and had increased collagen type I and TGFβ-1 gene expression; however these cells were not as aligned as were the cells and matrix on monotonic strained scaffolds. The alignment of AF cells grown on monotonic scaffolds correlated with significantly greater scaffold elastic modulus on day 7. Additionally, the cellular response to the change in strain was delayed by 3 to 5 days after tension release, which correlated with the time at which changes in scaffold length were detected. CONCLUSIONS This study demonstrated that AF cells respond at the molecular and cellular level to the changes in matrix/scaffold tension. This suggests that it may be necessary to determine the optimal elastic modulus and applied tensile forces to tissue engineer an AF that mimics the native tissue. Furthermore, this study provides insight into how changes in tensile forces may lead to changes in the AF cell function.
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Affiliation(s)
- Kathleen G Turner
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario, Canada M5S 3G9; CIHR-BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario, Canada M5G 1X5
| | - Nazish Ahmed
- CIHR-BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario, Canada M5G 1X5
| | - J Paul Santerre
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario, Canada M5S 3G9; Faculty of Dentistry, University of Toronto, 124 Edward St., Toronto, Ontario, Canada M5G 1G6
| | - Rita A Kandel
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario, Canada M5S 3G9; CIHR-BioEngineering of Skeletal Tissues Team, Mount Sinai Hospital, 600 University Ave., Toronto, Ontario, Canada M5G 1X5.
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13
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Key S, Adams MA, Stefanakis M. Healing of painful intervertebral discs: implications for physiotherapy Part 2 — pressure change therapy: a proposed clinical model to stimulate disc healing. PHYSICAL THERAPY REVIEWS 2013. [DOI: 10.1179/1743288x12y.0000000038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Ayturk UM, Gadomski B, Schuldt D, Patel V, Puttlitz CM. Modeling Degenerative Disk Disease in the Lumbar Spine: A Combined Experimental, Constitutive, and Computational Approach. J Biomech Eng 2012; 134:101003. [DOI: 10.1115/1.4007632] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Using a continuum approach for modeling the constitutive mechanical behavior of the intervertebral disk’s annulus fibrosus holds the potential for facilitating the correlation of morphology and biomechanics of this clinically important tissue. Implementation of a continuum representation of the disk’s tissues into computational models would yield a particularly valuable tool for investigating the effects of degenerative disease. However, to date, relevant efforts in the literature towards this goal have been limited due to the lack of a computationally tractable and implementable constitutive function. In order to address this, annular specimens harvested from a total of 15 healthy and degenerated intervertebral disks were tested under planar biaxial tension. Predictions of a strain energy function, which was previously shown to be unconditionally convex, were fit to the experimental data, and the optimized coefficients were used to modify a previously validated finite element model of the L4/L5 functional spinal unit. Optimization of material coefficients based on experimental results indicated increases in the micro-level orientation dispersion of the collagen fibers and the mechanical nonlinearity of these fibers due to degeneration. On the other hand, the finite element model predicted a progressive increase in the stress generation in annulus fibrosus due to stepwise degeneration of initially the nucleus and then the entire disk. Range of motion was predicted to initially increase with the degeneration of the nucleus and then decrease with the degeneration of the annulus in all rotational loading directions, except for axial rotation. Overall, degeneration was observed to specifically impact the functional effectiveness of the collagen fiber network of the annulus, leading to changes in the biomechanical behavior at both the tissue level and the motion-segment level.
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Affiliation(s)
- Ugur M. Ayturk
- Department of Orthopaedic Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, MA 02115
| | - Benjamin Gadomski
- Orthopaedic Bioengineering Research Laboratory, Department of Mechanical Engineering and School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523
| | - Dieter Schuldt
- Orthopaedic Bioengineering Research Laboratory, Department of Mechanical Engineering and School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523
| | - Vikas Patel
- The Spine Center, Department of Orthopaedics, University of Colorado Denver, Denver, CO 80045
| | - Christian M. Puttlitz
- Orthopaedic Bioengineering Research Laboratory, Department of Mechanical Engineering and School of Biomedical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523
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Adhikari AS, Glassey E, Dunn AR. Conformational dynamics accompanying the proteolytic degradation of trimeric collagen I by collagenases. J Am Chem Soc 2012; 134:13259-65. [PMID: 22720833 PMCID: PMC4800024 DOI: 10.1021/ja212170b] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Collagenases are the principal enzymes responsible for the degradation of collagens during embryonic development, wound healing, and cancer metastasis. However, the mechanism by which these enzymes disrupt the highly chemically and structurally stable collagen triple helix remains incompletely understood. We used a single-molecule magnetic tweezers assay to characterize the cleavage of heterotrimeric collagen I by both the human collagenase matrix metalloproteinase-1 (MMP-1) and collagenase from Clostridium histolyticum. We observe that the application of 16 pN of force causes an 8-fold increase in collagen proteolysis rates by MMP-1 but does not affect cleavage rates by Clostridium collagenase. Quantitative analysis of these data allows us to infer the structural changes in collagen associated with proteolytic cleavage by both enzymes. Our data support a model in which MMP-1 cuts a transient, stretched conformation of its recognition site. In contrast, our findings suggest that Clostridium collagenase is able to cleave the fully wound collagen triple helix, accounting for its lack of force sensitivity and low sequence specificity. We observe that the cleavage of heterotrimeric collagen is less force sensitive than the proteolysis of a homotrimeric collagen model peptide, consistent with studies suggesting that the MMP-1 recognition site in heterotrimeric collagen I is partially unwound at equilibrium.
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Affiliation(s)
| | | | - Alexander R. Dunn
- Department of Chemical Engineering, Stanford University, Stanford, CA - 94305
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Buttermann GR, Mendenhall HV. Feasibility of the Runt Cow forIn VivoTesting of a Spinal Interbody Prosthesis with Preliminary Results. J INVEST SURG 2012; 25:112-22. [DOI: 10.3109/08941939.2011.605204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Adhikari AS, Mekhdjian AH, Dunn AR. Strain tunes proteolytic degradation and diffusive transport in fibrin networks. Biomacromolecules 2012; 13:499-506. [PMID: 22185486 PMCID: PMC3737078 DOI: 10.1021/bm2015619] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proteolytic degradation of fibrin, the major structural component in blood clots, is critical both during normal wound healing and in the treatment of ischemic stroke and myocardial infarction. Fibrin-containing clots experience substantial strain due to platelet contraction, fluid shear, and mechanical stress at the wound site. However, little is understood about how mechanical forces may influence fibrin dissolution. We used video microscopy to image strained fibrin clots as they were degraded by plasmin, a major fibrinolytic enzyme. Applied strain causes up to 10-fold reduction in the rate of fibrin degradation. Analysis of our data supports a quantitative model in which the decrease in fibrin proteolysis rates with strain stems from slower transport of plasmin into the clot. We performed fluorescence recovery after photobleaching (FRAP) measurements to further probe the effect of strain on diffusive transport. We find that diffusivity perpendicular to the strain axis decreases with increasing strain, while diffusivity along the strain axis remains unchanged. Our results suggest that the properties of the fibrin network have evolved to protect mechanically loaded fibrin from degradation, consistent with its function in wound healing. The pronounced effect of strain upon diffusivity and proteolytic susceptibility within fibrin networks offers a potentially useful means of guiding cell growth and morphology in fibrin-based biomaterials.
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Affiliation(s)
- Arjun S. Adhikari
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305
| | - Armen H. Mekhdjian
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305
| | - Alexander R. Dunn
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305
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18
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Adhikari AS, Chai J, Dunn AR. Mechanical load induces a 100-fold increase in the rate of collagen proteolysis by MMP-1. J Am Chem Soc 2011; 133:1686-9. [PMID: 21247159 PMCID: PMC3320677 DOI: 10.1021/ja109972p] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Although mechanical stress is known to profoundly influence the composition and structure of the extracellular matrix (ECM), the mechanisms by which this regulation occurs remain poorly understood. We used a single-molecule magnetic tweezers assay to study the effect of force on collagen proteolysis by matrix metalloproteinase-1 (MMP-1). Here we show that the application of ∼10 pN in extensional force causes an ∼100-fold increase in proteolysis rates. Our results support a mechanistic model in which the collagen triple helix unwinds prior to proteolysis. The data and resulting model predict that biologically relevant forces may increase localized ECM proteolysis, suggesting a possible role for mechanical force in the regulation of ECM remodeling.
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Affiliation(s)
- Arjun S. Adhikari
- Department of Chemical Engineering, Stanford University, Stanford, CA
| | - Jack Chai
- Department of Chemical Engineering, Stanford University, Stanford, CA
| | - Alexander R. Dunn
- Department of Chemical Engineering, Stanford University, Stanford, CA
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Adams MA, Stefanakis M, Dolan P. Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain. Clin Biomech (Bristol, Avon) 2010; 25:961-71. [PMID: 20739107 DOI: 10.1016/j.clinbiomech.2010.07.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 07/23/2010] [Accepted: 07/27/2010] [Indexed: 02/07/2023]
Abstract
BACKGROUND Much is known about intervertebral disc degeneration, but little effort has been made to relate this information to the clinical problem of discogenic back pain, and how it might be treated. METHODS We re-interpret the scientific literature in order to provide a rationale for physical therapy treatments for discogenic back pain. INTERPRETATION Intervertebral discs deteriorate over many years, from the nucleus outwards, to an extent that is influenced by genetic inheritance and metabolite transport. Age-related deterioration can be accelerated by physical disruption, which leads to disc "degeneration" or prolapse. Degeneration most often affects the lower lumbar discs, which are loaded most severely, and it is often painful because nerves in the peripheral anulus or vertebral endplate can be sensitised by inflammatory-like changes arising from contact with blood or displaced nucleus pulposus. Surgically-removed human discs show an active inflammatory process proceeding from the outside-in, and animal studies confirm that effective healing occurs only in the outer anulus and endplate, where cell density and metabolite transport are greatest. Healing of the disc periphery has the potential to relieve discogenic pain, by re-establishing a physical barrier between nucleus pulposus and nerves, and reducing inflammation. CONCLUSION Physical therapies should aim to promote healing in the disc periphery, by stimulating cells, boosting metabolite transport, and preventing adhesions and re-injury. Such an approach has the potential to accelerate pain relief in the disc periphery, even if it fails to reverse age-related degenerative changes in the nucleus.
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Affiliation(s)
- Michael A Adams
- Centre for Comparative and Clinical Anatomy, University of Bristol, Bristol, UK.
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Hsieh AH, Yoon ST. Update on the pathophysiology of degenerative disc disease and new developments in treatment strategies. Open Access J Sports Med 2010; 1:191-9. [PMID: 24198557 PMCID: PMC3781869 DOI: 10.2147/oajsm.s9057] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Degenerative disc disease (DDD) continues to be a prevalent condition that afflicts populations on a global scale. The economic impact and decreased quality of life primarily stem from back pain and neurological deficits associated with intervertebral disc degeneration. Although much effort has been invested into understanding the etiology of DDD and its relationship to the onset of back pain, this endeavor is a work in progress. The purpose of this review is to provide focused discussion on several areas in which recent advances have been made. Specifically, we have categorized these advances into early, middle, and late phases of age-related or degenerative changes in the disc and into promising minimally invasive treatments, which aim to restore mechanical and biological functions to the disc.
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Affiliation(s)
- Adam H Hsieh
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
- Department of Orthopedics, University of Maryland, Baltimore, MD, USA
| | - S Tim Yoon
- Department of Orthopedic Surgery, Emory University, Chief of Orthopedic Surgery, Veterans Affairs Medical Center, Atlanta, GA, USA
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Flynn BP, Bhole AP, Saeidi N, Liles M, DiMarzio CA, Ruberti JW. Mechanical strain stabilizes reconstituted collagen fibrils against enzymatic degradation by mammalian collagenase matrix metalloproteinase 8 (MMP-8). PLoS One 2010; 5:e12337. [PMID: 20808784 PMCID: PMC2925882 DOI: 10.1371/journal.pone.0012337] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2010] [Accepted: 07/27/2010] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Collagen, a triple-helical, self-organizing protein, is the predominant structural protein in mammals. It is found in bone, ligament, tendon, cartilage, intervertebral disc, skin, blood vessel, and cornea. We have recently postulated that fibrillar collagens (and their complementary enzymes) comprise the basis of a smart structural system which appears to support the retention of molecules in fibrils which are under tensile mechanical strain. The theory suggests that the mechanisms which drive the preferential accumulation of collagen in loaded tissue operate at the molecular level and are not solely cell-driven. The concept reduces control of matrix morphology to an interaction between molecules and the most relevant, physical, and persistent signal: mechanical strain. METHODOLOGY/PRINCIPAL FINDINGS The investigation was carried out in an environmentally-controlled microbioreactor in which reconstituted type I collagen micronetworks were gently strained between micropipettes. The strained micronetworks were exposed to active matrix metalloproteinase 8 (MMP-8) and relative degradation rates for loaded and unloaded fibrils were tracked simultaneously using label-free differential interference contrast (DIC) imaging. It was found that applied tensile mechanical strain significantly increased degradation time of loaded fibrils compared to unloaded, paired controls. In many cases, strained fibrils were detectable long after unstrained fibrils were degraded. CONCLUSIONS/SIGNIFICANCE In this investigation we demonstrate for the first time that applied mechanical strain preferentially preserves collagen fibrils in the presence of a physiologically-important mammalian enzyme: MMP-8. These results have the potential to contribute to our understanding of many collagen matrix phenomena including development, adaptation, remodeling and disease. Additionally, tissue engineering could benefit from the ability to sculpt desired structures from physiologically compatible and mutable collagen.
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Affiliation(s)
- Brendan P. Flynn
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
| | - Amit P. Bhole
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
| | - Nima Saeidi
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
- Center for Engineering and Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Melody Liles
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Charles A. DiMarzio
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
- Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States of America
| | - Jeffrey W. Ruberti
- Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America
- * E-mail:
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22
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Zareian R, Church KP, Saeidi N, Flynn BP, Beale JW, Ruberti JW. Probing collagen/enzyme mechanochemistry in native tissue with dynamic, enzyme-induced creep. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:9917-9926. [PMID: 20429513 PMCID: PMC3712121 DOI: 10.1021/la100384e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Mechanical strain or stretch of collagen has been shown to be protective of fibrils against both thermal and enzymatic degradation. The details of this mechanochemical relationship could change our understanding of load-bearing tissue formation, growth, maintenance, and disease in vertebrate animals. However, extracting a quantitative relationship between strain and the rate of enzymatic degradation is extremely difficult in bulk tissue due to confounding diffusion effects. In this investigation, we develop a dynamic, enzyme-induced creep assay and diffusion/reaction rate scaling arguments to extract a lower bound on the relationship between strain and the cutting rate of bacterial collagenase (BC) at low strains. The assay method permits continuous, forced probing of enzyme-induced strain which is very sensitive to degradation rate differences between specimens at low initial strain. The results, obtained on uniaxially loaded strips of bovine corneal tissue (0.1, 0.25, or 0.5 N), demonstrate that small differences in strain alter the enzymatic cutting rate of the BC substantially. It was estimated that a change in tissue elongation of only 1.5% (at approximately 5% strain) reduces the maximum cutting rate of the enzyme by more than half. Estimation of the average load per monomer in the tissue strips indicates that this protective "cutoff" occurs when the collagen monomers are transitioning from an entropic to an energetic mechanical regime. The continuous tracking of the enzymatic cleavage rate as a function of strain during the initial creep response indicates that the decrease in the cleavage rate of the BC is nonlinear (initially steep between 4.5 and 6.5% and then flattens out from 6.5 to 9.5%). The high sensitivity to strain at low strain implies that even lightly loaded collagenous tissue may exhibit significant strain protection. The dynamic, enzyme-induced creep assay described herein has the potential to permit the rapid characterization of collagen/enzyme mechanochemistry in many different tissue types.
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Affiliation(s)
- Ramin Zareian
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA
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23
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Cellular mechanobiology of the intervertebral disc: new directions and approaches. J Biomech 2009; 43:137-45. [PMID: 19828150 DOI: 10.1016/j.jbiomech.2009.09.019] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/21/2009] [Indexed: 01/08/2023]
Abstract
The more we learn about the intervertebral disc (IVD), the more we come to appreciate the intricacies involved in transmission of forces through the ECM to the cell, and in the biological determinants of its response to mechanical stress. This review highlights recent developments in our knowledge of IVD physiology and examines their impact on cellular mechanobiology. Discussion centers around the continually evolving cellular and microstructural anatomy of the nucleus pulposus (NP) and the annulus fibrosus (AF) in response to complex stresses generated in support of axial load and spinal motion. Particular attention has been given to cells from the immature NP and the interlamellar AF, and assessment of their potential mechanobiologic contributions to the health and function of the IVD. In addition, several innovative approaches that have been brought to bear on studying the interplay between disc cells and their micromechanical environment are discussed. Techniques for "engineering" cellular function and technologies for fabricating more structurally defined biomaterial scaffolds have recently been employed in disc research. Such tools can be used to elucidate the biological and physical mechanisms by which different IVD cell populations are regulated by mechanical stress, and contribute to advancement of preventative and therapeutic measures.
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Bhole AP, Flynn BP, Liles M, Saeidi N, Dimarzio CA, Ruberti JW. Mechanical strain enhances survivability of collagen micronetworks in the presence of collagenase: implications for load-bearing matrix growth and stability. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:3339-62. [PMID: 19657003 PMCID: PMC2865878 DOI: 10.1098/rsta.2009.0093] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
There has been great interest in understanding the methods by which collagen-based load-bearing tissue is constructed, grown and maintained in vertebrate animals. To date, the responsibility for this process has largely been placed with mesenchymal fibroblastic cells that are thought to fully control the morphology of load-bearing extracellular matrix (ECM). However, given clear limitations in the ability of fibroblastic cells to precisely place or remove single collagen molecules to sculpt tissue, we have hypothesized that the material itself must play a critical role in the determination of the form of structural ECM. We here demonstrate directly, using live, dynamic, differential interference contrast imaging, that mechanically strained networks of collagen fibrils, exposed to collagenase (Clostridium histolyticum), degrade preferentially. Specifically, unstrained fibrils are removed 'quickly', while strained fibrils persist significantly longer. The demonstration supports the idea that collagen networks are mechanosensitive in that they are stabilized by mechanical strain. Thus, collagen molecules (together with their complement enzymes) may comprise the basis of a smart, load-adaptive, structural material system. This concept has the potential to drastically simplify the assumed role of the fibroblast, which would need only to provide ECM molecules and mechanical force to sculpt collagenous tissue.
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Affiliation(s)
- Amit P. Bhole
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
| | - Brendan P. Flynn
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
| | - Melody Liles
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
| | - Nima Saeidi
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
| | - Charles A. Dimarzio
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
| | - Jeffrey W. Ruberti
- Department of Mechanical and Industrial Engineering, Northeastern, University, 360 Huntington Avenue, Boston, MA 02139, USA
- Author for correspondence ()
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Nakamura T, Iribe T, Asou Y, Miyairi H, Ikegami K, Takakuda K. Effects of compressive loading on biomechanical properties of disc and peripheral tissue in a rat tail model. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2009; 18:1595-603. [PMID: 19557442 DOI: 10.1007/s00586-009-1078-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 04/02/2009] [Accepted: 06/10/2009] [Indexed: 11/30/2022]
Abstract
Intervertebral disc degeneration induced by mechanical compression is an important issue in spinal disorder research. In this study, the biomechanical aspect of the rat tail model was investigated. An external loading device equipped with super-elastic TiNi springs was developed to apply a precise load to the rat tail. By using this device, rat tail discs were subjected to compressive stress of 0.5 or 1.0 MPa for 2 weeks. Discs in the sham group received an attachment of the device but no loading. After the experimental period, first the intact tail with peripheral tissues (PT) such as tendon and skin and then the retrieved disc without PT were subjected to a uniaxial tension-compression test; biomechanical characteristics such as range of motion (ROM), neutral zone (NZ), and hysteresis loss (HL) were evaluated. Furthermore, the load-bearing contribution of PT in the intact tail was estimated by comparing the load-displacement curves obtained by the mechanical tests performed with and without PT. The experimental findings revealed that the continuous compressive stress induced reduction in disc thickness. The intact tail demonstrated decreases in ROM and NZ as well as increases in HL. On the other hand, the retrieved disc demonstrated increases in ROM, NZ, and HL. Further, a significant increase in the load-bearing contribution of PT was indicated. These findings suggest that the load-bearing capacity of the disc was seriously deteriorated by the application of compressive stress of 0.5 or 1.0 MPa for 2 weeks.
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Affiliation(s)
- Tomokazu Nakamura
- Department of Mechanical System Engineering, Graduate School of Advanced Science and Technology, Tokyo Denki University, 2-2 Kanda-Nishikicho, Chiyoda-ku, Tokyo 101-8457, Japan
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Boxberger JI, Orlansky AS, Sen S, Elliott DM. Reduced nucleus pulposus glycosaminoglycan content alters intervertebral disc dynamic viscoelastic mechanics. J Biomech 2009; 42:1941-6. [PMID: 19539936 DOI: 10.1016/j.jbiomech.2009.05.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 05/01/2009] [Accepted: 05/08/2009] [Indexed: 01/11/2023]
Abstract
The intervertebral disc functions over a range of dynamic loading regimes including axial loads applied across a spectrum of frequencies at varying compressive loads. Biochemical changes occurring in early degeneration, including reduced nucleus pulposus glycosaminoglycan content, may alter disc mechanical behavior and thus may contribute to the progression of degeneration. The objective of this study was to determine disc dynamic viscoelastic properties under several equilibrium loads and loading frequencies, and further, to determine how reduced nucleus glycosaminoglycan content alters dynamic mechanics. We hypothesized that (1) dynamic stiffness would be elevated with increasing equilibrium load and increasing frequency, (2) the disc would behave more elastically at higher frequencies, and finally, (3) dynamic stiffness would be reduced at low equilibrium loads under all frequencies due to nucleus glycosaminoglycan loss. We mechanically tested control and chondroitinase ABC injected rat lumbar motion segments at several equilibrium loads using oscillatory loading at frequencies ranging from 0.05 to 5Hz. The rat lumbar disc behaved non-linearly with higher dynamic stiffness at elevated compressive loads irrespective of frequency. Phase angle was not affected by equilibrium load, although it decreased as frequency was increased. Reduced glycosaminoglycan decreased dynamic stiffness at low loads but not at high equilibrium loads and led to increased phase angle at all loads and frequencies. The findings of this study demonstrate the effect of equilibrium load and loading frequencies on dynamic disc mechanics and indicate possible mechanical mechanisms through which disc degeneration can progress.
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Affiliation(s)
- John I Boxberger
- Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104-6081, USA
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An adherent nerve root--classification and exercise therapy in a patient diagnosed with lumbar disc prolapse. ACTA ACUST UNITED AC 2009; 15:126-9. [PMID: 19515601 DOI: 10.1016/j.math.2009.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 04/17/2009] [Accepted: 04/28/2009] [Indexed: 11/28/2022]
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