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Menon RG, de Moura HL, Kijowski R, Regatte RR. Age and gender differences in lumbar intervertebral disk strain using mechanical loading magnetic resonance imaging. NMR IN BIOMEDICINE 2023; 36:e4999. [PMID: 37409683 PMCID: PMC10876068 DOI: 10.1002/nbm.4999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/07/2023] [Accepted: 06/10/2023] [Indexed: 07/07/2023]
Abstract
The objective of the current study was to investigate age- and gender-related differences in lumbar intervertebral disk (IVD) strain with the use of static mechanical loading and continuous three-dimensional (3D) golden-angle radial sparse parallel (GRASP) MRI. A continuous 3D-GRASP stack-of-stars trajectory of the lumbar spine was performed on a 3-T scanner with static mechanical loading. Compressed sensing reconstruction, motion deformation maps, and Lagrangian strain maps during loading and recovery in the X-, Y-, and Z-directions were calculated for segmented IVD segments from L1/L2 to L5/S1. Mean IVD height was measured at rest. Spearman coefficients were used to evaluate the associations between age and global IVD height and global IVD strain. Mann-Whitney tests were used to compare global IVD height and global IVD strain in males and females. The prospective study enrolled 20 healthy human volunteers (10 males, 10 females; age 34.6 ± 11.4 [mean ± SD], range 22-56 years). Significant increases in compressive strain were observed with age, as evidenced by negative correlations between age and global IVD strain during loading (ρ = -0.76, p = 0.0046) and recovery (ρ = -0.68, p = 0.0251) in the loading X-direction. There was no significant correlation between age and global IVD height, global IVD strain during loading and recovery in the Y-direction, and global IVD strain during loading and recovery in the Z-direction. There were no significant differences between males and females in global IVD height and global IVD strain during loading and recovery in the X-, Y-, and Z-directions. It was concluded that our study demonstrated the significant role aging plays in internal dynamic strains in the lumbar IVD during loading and recovery. Older healthy individuals have reduced IVD stiffness and greater IVD compression during static mechanical loading of the lumbar spine. The GRASP-MRI technique demonstrates the feasibility to identify changes in IVD mechanical properties with early IVD degeneration due to aging.
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Affiliation(s)
- Rajiv G. Menon
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine
| | - Hector L. de Moura
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine
| | - Richard Kijowski
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine
| | - Ravinder R. Regatte
- Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine
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Zhang A, Cheng Z, Chen Y, Shi P, Gan W, Zhang Y. Emerging tissue engineering strategies for annulus fibrosus therapy. Acta Biomater 2023:S1742-7061(23)00337-9. [PMID: 37330029 DOI: 10.1016/j.actbio.2023.06.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 05/31/2023] [Accepted: 06/12/2023] [Indexed: 06/19/2023]
Abstract
Low back pain is a major public health concern experienced by 80% of the world's population during their lifetime, which is closely associated with intervertebral disc (IVD) herniation. IVD herniation manifests as the nucleus pulposus (NP) protruding beyond the boundaries of the intervertebral disc due to disruption of the annulus fibrosus (AF). With a deepening understanding of the importance of the AF structure in the pathogenesis of intervertebral disc degeneration, numerous advanced therapeutic strategies for AF based on tissue engineering, cellular regeneration, and gene therapy have emerged. However, there is still no consensus concerning the optimal approach for AF regeneration. In this review, we summarized strategies in the field of AF repair and highlighted ideal cell types and pro-differentiation targeting approaches for AF repair, and discussed the prospects and difficulties of implant systems combining cells and biomaterials to guide future research directions. STATEMENT OF SIGNIFICANCE: Low back pain is a major public health concern experienced by 80% of the world's population during their lifetime, which is closely associated with intervertebral disc (IVD) herniation. However, there is still no consensus concerning the optimal approach for annulus fibrosus (AF) regeneration. In this review, we summarized strategies in the field of AF repair and highlighted ideal cell types and pro-differentiation targeting approaches for AF repair, and discussed the prospects and difficulties of implant systems combining cells and biomaterials to guide future research directions.
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Affiliation(s)
- Anran Zhang
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Zhangrong Cheng
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Yuhang Chen
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Pengzhi Shi
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Weikang Gan
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Yukun Zhang
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
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Kandil K, Zaïri F, Zaïri F. A Microstructure-Based Mechanistic Approach to Detect Degeneration Effects on Potential Damage Zones and Morphology of Young and Old Human Intervertebral Discs. Ann Biomed Eng 2023:10.1007/s10439-023-03179-0. [PMID: 36976433 DOI: 10.1007/s10439-023-03179-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 02/23/2023] [Indexed: 03/29/2023]
Abstract
There is an increasing demand to develop predictive medicine through the creation of predictive models and digital twins of the different body organs. To obtain accurate predictions, real local microstructure, morphology changes and their accompanying physiological degenerative effects must be taken into account. In this article, we present a numerical model to estimate the long-term aging effect on the human intervertebral disc response by means of a microstructure-based mechanistic approach. It allows to monitor in-silico the variations in disc geometry and local mechanical fields induced by age-dependent long-term microstructure changes. Both lamellar and interlamellar zones of the disc annulus fibrosus are constitutively represented by considering the main underlying microstructure features in terms of proteoglycans network viscoelasticity, collagen network elasticity (along with content and orientation) and chemical-induced fluid transfer. With age, a noticeable increase in shear strain is especially observed in the posterior and lateral posterior regions of the annulus which is in correlation with the high vulnerability of elderly people to back problems and posterior disc hernia. Important insights about the relation between age-dependent microstructure features, disc mechanics and disc damage are revealed using the present approach. These numerical observations are hardly obtainable using current experimental technologies which makes our numerical tool useful for patient-specific long-term predictions.
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Affiliation(s)
- Karim Kandil
- Icam School of Engineering - Site of Lille, 6 rue Auber, 59016, Lille, France
- Laboratoire de Génie Civil et géo-Environnement, ULR 4515 - LGCgE, Univ. Lille, IMT Lille Douai, Univ. Artois, JUNIA, 59000, Lille, France
| | - Fahmi Zaïri
- Laboratoire de Génie Civil et géo-Environnement, ULR 4515 - LGCgE, Univ. Lille, IMT Lille Douai, Univ. Artois, JUNIA, 59000, Lille, France.
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital privé Le Bois, 59000, Lille, France
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Atthapreyangkul A, Hoffman M, Pearce G, Standard O. Effect of geometrical structure variations on strength and damage onset of cortical bone using multi-scale cohesive zone based finite element method. J Mech Behav Biomed Mater 2023; 138:105578. [PMID: 36427415 DOI: 10.1016/j.jmbbm.2022.105578] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/15/2022] [Indexed: 11/18/2022]
Abstract
Three-dimensional multi-scale finite element models were designed to examine the effects of geometrical structure variations on the damage onset in cortical bone at multiple structural scales. A cohesive zone finite element approach, together with anisotropic damage initiation criteria, is used to predict the onset of damage. The finite element models are developed to account for the onset of microdamage from the microscopic length scales consisting of collagen fibres, to the macroscopic level consisting of osteons and the Haversian canals. Numerical results indicated that the yield strain at the initiation of microcracks is independent of variations in the local mineral volume fraction at each structural scale. Further, the yield strain and strength properties of cortical bone are dependent on its structural anisotropy and hierarchical structure. A positive correlation is observed between bone strength and mineral content at each length scale.
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Affiliation(s)
| | - Mark Hoffman
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia; School of Engineering, The University of Newcastle, NSW, 2308, Australia.
| | - Garth Pearce
- School of Mechanical and Manufacturing Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Owen Standard
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia
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Meadows KD, Peloquin JM, Newman HR, Cauchy PJK, Vresilovic EJ, Elliott DM. MRI
‐based measurement of in vivo disc mechanics in a young population due to flexion, extension, and diurnal loading. JOR Spine 2023; 6:e1243. [PMID: 36994458 PMCID: PMC10041375 DOI: 10.1002/jsp2.1243] [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: 09/16/2022] [Revised: 12/14/2022] [Accepted: 12/21/2022] [Indexed: 01/12/2023] Open
Abstract
Background Intervertebral disc degeneration is often implicated in low back pain; however, discs with structural degeneration often do not cause pain. It may be that disc mechanics can provide better diagnosis and identification of the pain source. In cadaveric testing, the degenerated disc has altered mechanics, but in vivo, disc mechanics remain unknown. To measure in vivo disc mechanics, noninvasive methods must be developed to apply and measure physiological deformations. Aim Thus, this study aimed to develop methods to measure disc mechanical function via noninvasive MRI during flexion and extension and after diurnal loading in a young population. This data will serve as baseline disc mechanics to later compare across ages and in patients. Materials & Methods To accomplish this, subjects were imaged in the morning in a reference supine position, in flexion, in extension, and at the end of the day in a supine position. Disc deformations and vertebral motions were used to quantify disc axial strain, changes in wedge angle, and anterior-posterior (A-P) shear displacement. T2 weighted MRI was also used to evaluate disc degeneration via Pfirrmann grading and T2 time. All measures were then tested for effect of sex and disc level. Results We found that flexion and extension caused level-dependent strains in the anterior and posterior of the disc, changes in wedge angle, and A-P shear displacements. Flexion had higher magnitude changes overall. Diurnal loading did not cause level-dependent strains but did cause small level-dependent changes in wedge angle and A-P shear displacements. Discussion Correlations between disc degeneration and mechanics were largest in flexion, likely due to the smaller contribution of the facet joints in this condition. Conclusion In summary, this study established methods to measure in vivo disc mechanical function via noninvasive MRI and established a baseline in a young population that may be compared to older subjects and clinical disorders in the future.
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Affiliation(s)
- Kyle D. Meadows
- Department of Biomedical Engineering University of Delaware Newark Delaware USA
| | - John M. Peloquin
- Department of Biomedical Engineering University of Delaware Newark Delaware USA
| | - Harrah R. Newman
- Department of Biomedical Engineering University of Delaware Newark Delaware USA
| | - Peter J. K. Cauchy
- Department of Biomedical Engineering University of Delaware Newark Delaware USA
| | | | - Dawn M. Elliott
- Department of Biomedical Engineering University of Delaware Newark Delaware USA
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Eremina G, Smolin A, Xie J, Syrkashev V. Development of a Computational Model of the Mechanical Behavior of the L4-L5 Lumbar Spine: Application to Disc Degeneration. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6684. [PMID: 36234026 PMCID: PMC9572952 DOI: 10.3390/ma15196684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Degenerative changes in the lumbar spine significantly reduce the quality of life of people. In order to fully understand the biomechanics of the affected spine, it is crucial to consider the biomechanical alterations caused by degeneration of the intervertebral disc (IVD). Therefore, this study is aimed at the development of a discrete element model of the mechanical behavior of the L4-L5 spinal motion segment, which covers all the degeneration grades from healthy IVD to its severe degeneration, and numerical study of the influence of the IVD degeneration on stress state and biomechanics of the spine. In order to analyze the effects of IVD degeneration on spine biomechanics, we simulated physiological loading conditions using compressive forces. The results of modeling showed that at the initial stages of degenerative changes, an increase in the amplitude and area of maximum compressive stresses in the disc is observed. At the late stages of disc degradation, a decrease in the value of intradiscal pressure and a shift in the maximum compressive stresses in the dorsal direction is observed. Such an influence of the degradation of the geometric and mechanical parameters of the tissues of the disc leads to the effect of bulging, which in turn leads to the formation of an intervertebral hernia.
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Affiliation(s)
- Galina Eremina
- Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, Pr. Akademicheskii, 2/4, 634055 Tomsk, Russia
| | - Alexey Smolin
- Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, Pr. Akademicheskii, 2/4, 634055 Tomsk, Russia
| | - Jing Xie
- State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China
| | - Vladimir Syrkashev
- Department of General Medicine, Siberian State Medical University, Moskovsky Trakt, 2, 634050 Tomsk, Russia
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Bhattacharya S, Dubey DK. Impact of Variations in Water Concentration on the Nanomechanical Behavior of Type I Collagen Microfibrils in Annulus Fibrosus. J Biomech Eng 2022; 144:1120715. [PMID: 34820681 DOI: 10.1115/1.4052563] [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: 04/04/2021] [Indexed: 11/08/2022]
Abstract
Radial variation in water concentration from outer to inner lamellae is one of the characteristic features of annulus fibrosus (AF). In addition, water concentration changes are also associated with intervertebral disc (IVD) degeneration. Such changes alter the chemo-mechanical interactions among the biomolecular constituents at molecular level, affecting the load-bearing nature of IVD. This study investigates mechanistic impacts of water concentration on the collagen type I microfibrils in AF using molecular dynamics simulations. Results show, in axial tension, that increase in water concentration (WC) from 0% to 50% increases the elastic modulus from 2.7 GPa to 3.9 GPa. This is attributed to combination of shift in deformation from backbone straightening to combined backbone stretching- intermolecular sliding and subsequent strengthening of tropocollagen-water (TC-water-TC) interfaces through water bridges and intermolecular electrostatic attractions. Further increase in WC to 75% reduces the modulus to 1.8 GPa due to shift in deformation to polypeptide straightening and weakening of TC-water-TC interface due to reduced electrostatic attraction and increase in the number of water molecules in a water bridge. During axial compression, increase in WC to 50% results in increase in modulus from 0.8 GPa to 4.5 GPa. This is attributed to the combination of the development of hydrostatic pressure and strengthening of the TC-water-TC interface. Further increase in WC to 75% shifts load-bearing characteristic from collagen to water, resulting in a decrease in elastic modulus to 2.8 GPa. Such water-mediated alteration in load-bearing properties acts as foundations toward AF mechanics and provides insights toward understanding degeneration-mediated altered spinal stiffness.
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Affiliation(s)
- Shambo Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, New Delhi 110016, India
| | - Devendra K Dubey
- Department of Mechanical Engineering, Indian Institute of Technology, Delhi, New Delhi 110016, India
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Glennie RA, Bailey CS, Abraham E, Manson N, Casha S, Thomas K, Paquet J, McIntosh G, Hall H, Fisher CG, Rampersaud YR. Variation in surgical treatment of degenerative spondylolisthesis in Canada: surgeon assessment of stability and impact on treatment. 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 2021; 30:3709-3719. [PMID: 34327542 DOI: 10.1007/s00586-021-06928-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 07/12/2021] [Indexed: 11/30/2022]
Abstract
INTRODUCTION Controversy exists regarding the optimal surgical treatment of degenerative lumbar spondylolisthesis (DS). Not all DS patients are the same, and the degree to which inherent stability may dictate treatment is unknown. The purpose of this study was to determine the variability in surgical approach relative to surgeon classified stability. The secondary objective was to compare patient-reported outcomes (PROs) across different surgical techniques and grades of stability. METHODS Patients prospectively enrolled from eleven tertiary care institutions and followed from 2015 to 2019. The surgical technique was at the surgeon's discretion. Surgeons were asked to grade the degree of instability based on the degenerative spondylolisthesis instability classification system (DSIC). DSIC categorizes three different types (I-stable, II-potentially unstable, and III-unstable). One-year changes in PROs were compared between each group. Multivariable regression was used to identify any characteristics that explained variability in treatment. RESULTS There were 323 patients enrolled in this study. Surgeons' stability classification versus procedure [decompression alone (D)/decompression and posterolateral fusion (D-PL)/and decompression with posterior/transforaminal lumbar interbody fusion (D-PLIF/TLIF)] were as follows: type I (n = 91): D-41%/D-PL-13%/D-PLIF/TLIF-46%; type II (n = 175): D-23%/D-PL-17%/D-PLIF/TLIF-60%; and type III (n = 57):(D-0%/D-PL-14%/D-PLIF/TLIF-86%). Type I patients undergoing D-PL had some improvements in EQ-5D and NRS versus those undergoing D-PLIF/TLIF but otherwise there were no other significant differences between groups. Regression analysis demonstrated advanced age (OR = 1.06, CI 1.02-10.12) and type I (OR = 2.61, CI 1.17-5.81) were associated with receiving decompression surgery alone. CONCLUSIONS There exists considerable variation in surgical management of DS in Canada. Given similar PROs in two of the three groups, there is potential to tailor surgical intervention and improve resource utilization.
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Affiliation(s)
- R Andrew Glennie
- Department of Surgery, Dalhousie University, Halifax, NS, Canada.
| | | | | | - Neil Manson
- Canada East Spine Center, Saint John, NB, Canada
| | - Steve Casha
- University of Calgary Cumming School of Medicine, Calgary, AB, Canada
| | - Kenneth Thomas
- University of Calgary Cumming School of Medicine, Calgary, AB, Canada
| | - Jerome Paquet
- CHU Laval: Centre Hospitalier de l'Universite Laval, Quebec, Canada
| | - Greg McIntosh
- The University of British Columbia, Vancouver, BC, Canada
| | - Hamiton Hall
- University of Toronto Faculty of Medicine, Toronto, ON, Canada
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Kandil K, Zaïri F, Messager T, Zaïri F. A microstructure-based modeling approach to assess aging-sensitive mechanics of human intervertebral disc. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2021; 200:105890. [PMID: 33317872 DOI: 10.1016/j.cmpb.2020.105890] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND AND OBJECTIVE The human body soft tissues are hierarchic structures interacting in a complex manner with the surrounding biochemical environment. The loss of soft tissues functionality with age leads to more vulnerability regarding to the external mechanical loadings and increases the risk of injuries. As a main example of the human body soft tissues, the intervertebral disc mechanical response evolution with age is explored. Although the age-dependence of the intervertebral disc microstructure is a well-known feature, no noticeable age effect on the disc stiffness is evidenced in the in-vitro experimental studies of the literature. So, if the disc intrinsic mechanics remains constant, how to explain the correlation of disc degeneration and disc functionality loss with age. METHODS A microstructure-based modeling approach was developed to assess in-silico the aging-sensitive mechanics of human intervertebral disc. The model considers the relationship between stress/volumetric macro-response and microstructure along with effective age effects acting at the lamellar and multi-lamellar scales. The stress-stretch and transversal responses of the different disc regions were computed for various age groups (13-18, 36, 58, 69 and 82 years old) and their evolution with age was studied. RESULTS While matching with in-vitro experimental data, the predicted stiffness was found to increase while passing from adolescent young discs to mature older discs and then to remain almost constant for the rest of life. Important age-related changes in the disc transversal behavior were also predicted affecting the flexibility of the disc, changing its volumetric behavior, and modifying its dimensions. CONCLUSION The developed approach was found able to bring new conclusions about age-dependent mechanical properties including regional dependency. The disc mechanics in terms of rigidity, radial and axial transversal responses were found to alter going from adolescent to middle age where the disc reaches a certain maturity. After reaching maturity, the mechanical properties undergo very slight changes until becoming almost constant with age.
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Affiliation(s)
- Karim Kandil
- Lille University, Unité de Mécanique de Lille (EA 7572 UML), 59000 Lille, France; Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France
| | - Fahmi Zaïri
- Lille University, Civil Engineering and geo-Environmental Laboratory (ULR 4515 LGCgE), 59000 Lille, France.
| | - Tanguy Messager
- Lille University, Unité de Mécanique de Lille (EA 7572 UML), 59000 Lille, France
| | - Fahed Zaïri
- Ramsay Générale de Santé, Hôpital privé Le Bois, 59000 Lille, France
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Zhou P, Wei B, Guan J, Chen Y, Zhu Y, Ye Y, Meng Y, Guan J, Mao Y. Mechanical Stimulation and Diameter of Fiber Scaffolds Affect the Differentiation of Rabbit Annulus Fibrous Stem Cells. Tissue Eng Regen Med 2021; 18:49-60. [PMID: 33145743 PMCID: PMC7862471 DOI: 10.1007/s13770-020-00305-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/12/2020] [Accepted: 09/20/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Degeneration of the annulus fibrosus (AF), an important structure of the intervertebral disc, is one of the main causes of degenerative disc disease. Fabrication of scaffolds replicating the stratified microstructure of the AF is critical for the successful regeneration of AF. METHODS In this study, we cultured rabbit AF-derived stem cells (AFSCs) using fabricated electrospun fibrous poly-L-lactic acid scaffolds with different diameters. We applied cyclic tensile strain (CTS) on the scaffolds to regulate the differentiation of AFSCs into specific cell types that resided at the inner, middle, and outer zones of the AF. RESULTS We found that the morphologies of AFSCs on the smaller-fiber-diameter scaffolds were nearly round, whereas spindle-like cells morphologies were observed on large-diameter scaffolds. CTS enhanced these phenomena and made the cells slender. The expression levels of collagen-I in cells increased as a function of the fiber diameter, whereas collagen-II and aggrecan exhibited opposite trends. Moreover, the application of CTS upregulated the gene expressions of collagen-I, collagen-II, and aggrecan. CONCLUSION Overlaying the scaffolds with different CTS-stimulated cells could eventually lead to engineered AF tissues with hierarchical structures that approximated the native AF tissue. Thus, the proposed methodologies could be potentially applied for AF regeneration.
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Affiliation(s)
- Pinghui Zhou
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China
- Anhui Province Key Laboratory of Tissue Transplantation, Bengbu Medical College, Bengbu, 233030, China
| | - Bangguo Wei
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China
- Anhui Province Key Laboratory of Tissue Transplantation, Bengbu Medical College, Bengbu, 233030, China
| | - Jingjing Guan
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China
| | - Yu Chen
- Anhui Province Key Laboratory of Tissue Transplantation, Bengbu Medical College, Bengbu, 233030, China
- School of Life Sciences, Bengbu Medical College, Bengbu, 233030, China
- Department of Plastic Surgery, the First Affiliated Hospital of Bengbu Medical College, Bengbu, 233004, China
| | - Yansong Zhu
- School of Life Sciences, Bengbu Medical College, Bengbu, 233030, China
| | - Yuchen Ye
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China
| | - Yue Meng
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China
| | - Jianzhong Guan
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China.
- Anhui Province Key Laboratory of Tissue Transplantation, Bengbu Medical College, Bengbu, 233030, China.
| | - Yingji Mao
- Department of Orthopedics, First Affiliated Hospital, Bengbu Medical College, Bengbu, 233004, China.
- Anhui Province Key Laboratory of Tissue Transplantation, Bengbu Medical College, Bengbu, 233030, China.
- School of Life Sciences, Bengbu Medical College, Bengbu, 233030, China.
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11
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Atthapreyangkul A, Hoffman M, Pearce G. Effect of geometrical structure variations on the viscoelastic and anisotropic behaviour of cortical bone using multi-scale finite element modelling. J Mech Behav Biomed Mater 2020; 113:104153. [PMID: 33125948 DOI: 10.1016/j.jmbbm.2020.104153] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 10/10/2020] [Accepted: 10/21/2020] [Indexed: 11/25/2022]
Abstract
Multi-scale finite element analysis is performed to ascertain the effect of geometrical changes at multiple structural scales on the mechanical properties of cortical bone. Finite element models are developed, with reference to experimental data from existing literature, to account for bone's viscoelastic behaviour and anisotropic structure from the most fundamental level of bone consisting of mineralised collagen fibrils, up to the macroscopic level consisting of osteons and the Haversian canals. A statistical approach is incorporated to perform sensitivity analyses on the effects of different geometrical parameters on the effective material properties of cortical bone at each length scale. Numerical results indicate that there is an exponential correlation between the mineral volume fraction and the effective stiffness constants at each length scale. This contributes to the exponential behaviour of the instantaneous moduli describing cortical bone's two-phase stress relaxation process: a fast and slow response relaxation behaviour. Results indicate that the fast response relaxation time is independent of bone's structural anisotropy, whilst being dependent on variations in the global mineral volume fraction between length scales. However, the slow response relaxation time is independent of the changes in mineral volume fraction. It is also observed that the slow response relaxation time varies with bone's anisotropic structure, and therefore, contributes to the anisotropic properties of bone.
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Affiliation(s)
| | - Mark Hoffman
- School of Materials Science and Engineering, UNSW, Sydney, NSW, 2052, Australia; School of Mechanical and Manufacturing Engineering, UNSW, Sydney, NSW, 2052, Australia; School of Engineering, The University of Newcastle, NSW, 2308, Australia.
| | - Garth Pearce
- School of Mechanical and Manufacturing Engineering, UNSW, Sydney, NSW, 2052, Australia
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12
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Effect of aggrecan degradation on the nanomechanics of hyaluronan in extra-fibrillar matrix of annulus fibrosus: A molecular dynamics investigation. J Mech Behav Biomed Mater 2020; 107:103752. [PMID: 32278311 DOI: 10.1016/j.jmbbm.2020.103752] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 03/18/2020] [Accepted: 03/20/2020] [Indexed: 12/19/2022]
Abstract
Intervertebral Disc (IVD) Degeneration is one of the primary causes of low back pain among the adult population - the most significant cause being the degradation of aggrecan present in the extra-fibrillar matrix (EFM). Aggrecan degradation is closely associated with loss of water content leading to an alteration in the mechanical behaviour of the IVD. The loss in water content has a significant impact on the chemo-mechanical interplay of IVD biochemical constituents at the fundamental level. This work presents a mechanistic understanding of the effect of hydration, closely associated with aggrecan degradation, on the nanoscale mechanical behaviour of the hyaluronan present in the EFM of the Annulus Fibrosus. For this purpose, explicit three-dimensional molecular dynamics analyses of tensile and compressive tests are performed on a representative atomistic model of the hyaluronan present in the EFM. To account for the degradation of aggrecan, hydration levels are varied from 0 to 75% by weight of water. Analyses show that an increase in the hydration levels decreases the elastic modulus of hyaluronan in tension from ~4.6 GPa to ~2.1 GPa. On the other hand, the increase in hydration level increases the elastic moduli in axial compression from ~1.6 GPa in un-hydrated condition to ~6 GPa in 50% hydrated condition. But as the hydration levels increase to 75%, the elastic modulus reduces to ~3.5 GPa signifying a shift in load-bearing characteristic, from the solid hyaluronan component to the fluid component. Furthermore, analyses show a reduction in the intermolecular energy between hyaluronan and water, under axial tensile loading, indicating a nanoscale intermolecular debonding between hyaluronan and water molecules. This is attributed to the ability of hyaluronan to form stabilizing intra-molecular hydrogen bonds between adjacent residues. Compressive loading, on the other hand, causes intensive coiling of hyaluronan molecule, which traps more water through hydrogen bonding and aids in bearing compressive loads. Overall, study shows that hydration level has a strong influence on the atomistic level interactions between hyaluronan molecules and hyaluronan and water molecules in the EFM which influences the nanoscale mechanics of the Annulus Fibrosus.
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Bashkuev M, Reitmaier S, Schmidt H. Relationship between intervertebral disc and facet joint degeneration: A probabilistic finite element model study. J Biomech 2020; 102:109518. [DOI: 10.1016/j.jbiomech.2019.109518] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 11/11/2019] [Accepted: 11/12/2019] [Indexed: 12/25/2022]
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Peng Y, Huang D, Liu S, Li J, Qing X, Shao Z. Biomaterials-Induced Stem Cells Specific Differentiation Into Intervertebral Disc Lineage Cells. Front Bioeng Biotechnol 2020; 8:56. [PMID: 32117935 PMCID: PMC7019859 DOI: 10.3389/fbioe.2020.00056] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Accepted: 01/22/2020] [Indexed: 12/11/2022] Open
Abstract
Stem cell therapy, which promotes stem cells differentiation toward specialized cell types, increases the resident population and production of extracellular matrix, and can be used to achieve intervertebral disc (IVD) repair, has drawn great attention for the development of IVD-regenerating materials. Many materials that have been reported in IVD repair have the ability to promote stem cells differentiation. However, due to the limitations of mechanical properties, immunogenicity and uncontrollable deviations in the induction of stem cells differentiation, there are few materials that can currently be translated into clinical applications. In addition to the favorable mechanical properties and biocompatibility of IVD materials, maintaining stem cells activity in the local niche and increasing the ability of stem cells to differentiate into nucleus pulposus (NP) and annulus fibrosus (AF) cells are the basis for promoting the application of IVD-regenerating materials in clinical practice. The purpose of this review is to summarize IVD-regenerating materials that focus on stem cells strategies, analyze the properties of these materials that affect the differentiation of stem cells into IVD-like cells, and then present the limitations of currently used disc materials in the field of stem cell therapy and future research perspectives.
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Affiliation(s)
- Yizhong Peng
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Donghua Huang
- Musculoskeletal Tumor Center, Department of Orthopedics, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
| | - Sheng Liu
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jinye Li
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiangcheng Qing
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zengwu Shao
- Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Jin LY, Song XX, Li XF. The role of estrogen in intervertebral disc degeneration. Steroids 2020; 154:108549. [PMID: 31812622 DOI: 10.1016/j.steroids.2019.108549] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/22/2019] [Accepted: 11/27/2019] [Indexed: 02/08/2023]
Abstract
Intervertebral disc degeneration (IVDD) is a main contributor to low back and radicular pain, which imposes heavy economic burdens on society. However, the etiology and mechanism of IVDD are complex and still not completely clear. In particular, the role of estrogen in IVDD has not received much attention in recent research, although estrogen plays a crucial role in the metabolic dysfunction of others musculoskeletal structures, such as bone, muscle, and tendon. In this review, we attempt to describe the role of estrogen in IVDD and to summarize the proposed mechanisms in vivo and in vitro, as well as, to outline several interesting questions in this field.
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Affiliation(s)
- Lin-Yu Jin
- Department of Orthopaedic Surgery, Baoshan Branch of Renji Hospital, School of Medicine, Shanghai Jiaotong University, No. 1058, Huan Zheng Bei Rd, Shanghai 200444, China; Department of Spinal Surgery, Peking University People's Hospital, Peking University, Beijing 100044, China
| | - Xiao-Xing Song
- Department of Anesthesiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Lu, Shanghai 200025, China.
| | - Xin-Feng Li
- Department of Orthopaedic Surgery, Baoshan Branch of Renji Hospital, School of Medicine, Shanghai Jiaotong University, No. 1058, Huan Zheng Bei Rd, Shanghai 200444, China.
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Bashkuev M, Reitmaier S, Schmidt H. Effect of disc degeneration on the mechanical behavior of the human lumbar spine: a probabilistic finite element study. Spine J 2018; 18:1910-1920. [PMID: 29886164 DOI: 10.1016/j.spinee.2018.05.046] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 05/28/2018] [Accepted: 05/31/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Intervertebral disc degeneration has been subject to numerous in vivo and in vitro investigations and numerical studies during recent decades, reporting partially contradictory findings. However, most of the previous studies were limited in the number of specimens investigated and, therefore, could not consider the vast variety of the specimen geometries, which are likely to strongly influence the mechanical behavior of the spine. PURPOSE To complement the understanding of the mechanical consequences of disc degeneration, whereas considering natural variations in the major spinal geometrical parameters. DESIGN/SETTING A probabilistic finite element study. METHODS A parametric finite element model of a human L4-L5 motion segment considering 40 geometrical parameters was developed. One thousand individual geometries comprising four degeneration grades were generated in a probabilistic manner, and the influence of the severity of disc degeneration on the mechanical response of the motion segment to different loading conditions was statistically evaluated. RESULTS Variations in the individual structural parameters resulted in marked variations in all evaluated parameters within each degeneration grade. Nevertheless, the effect of degeneration in almost all evaluated response values was statistically significant. With degeneration, the intradiscal pressure progressively decreased. At the same time, the facet loads increased and the ligament tension was reduced. The initially nonlinear load-deformation relationships became linear whereas the segment stiffness increased. CONCLUSIONS Results indicate significant stiffening of the motion segment with progressing degeneration and gradually increasing loading of the facets from nondegenerated to moderately degenerated conditions along with a significant reduction of the ligament tension in flexion.
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Affiliation(s)
- Maxim Bashkuev
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Julius Wolff Institut, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Sandra Reitmaier
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Julius Wolff Institut, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Hendrik Schmidt
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Julius Wolff Institut, Augustenburger Platz 1, 13353 Berlin, Germany.
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Chu G, Shi C, Wang H, Zhang W, Yang H, Li B. Strategies for Annulus Fibrosus Regeneration: From Biological Therapies to Tissue Engineering. Front Bioeng Biotechnol 2018; 6:90. [PMID: 30042942 PMCID: PMC6048238 DOI: 10.3389/fbioe.2018.00090] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 06/18/2018] [Indexed: 12/17/2022] Open
Abstract
Intervertebral disc (IVD) is an avascular tissue which contributes to the weight bearing, motion, and flexibility of spine. However, IVD is susceptible to damage and even failure due to injury, pathology, and aging. Annulus fibrosus (AF), the structural and functional integrity of which is critically essential to confine nucleus pulpous (NP) and maintain physiological intradiscal pressure under mechanical loading, plays a critical role in the biomechanical properties of IVD. AF degeneration commonly results in substantial deterioration of IVD. During this process, the biomechanical properties of AF and the balance between anabolism and catabolism in IVD are progressively disrupted, leading to chronic back pain, and even disability of individuals. Therefore, repairing and regenerating AF are effective treatments to degeneration-associated pains. However, they remain highly challenging due to the complexity of natural AF tissue in the aspects of cell phenotype, biochemical composition, microstructure, and mechanical properties. Tissue engineering (TE), by combining biological science and materials engineering, shed lights on AF regeneration. In this article, we review recent advances in the pro-anabolic approaches in the form of cell delivery, bioactive factors delivery, gene therapy, and TE strategies for achieving AF regeneration.
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Affiliation(s)
- Genglei Chu
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
- Department of Orthopaedic Surgery, First Affiliated Hospital, Soochow University, Suzhou, China
| | - Chen Shi
- Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Huan Wang
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
- Department of Orthopaedic Surgery, First Affiliated Hospital, Soochow University, Suzhou, China
| | - Weidong Zhang
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
- Department of Orthopaedic Surgery, First Affiliated Hospital, Soochow University, Suzhou, China
| | - Huilin Yang
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
- Department of Orthopaedic Surgery, First Affiliated Hospital, Soochow University, Suzhou, China
| | - Bin Li
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
- Department of Orthopaedic Surgery, First Affiliated Hospital, Soochow University, Suzhou, China
- China Orthopaedic Regenerative Medicine Group, Hangzhou, China
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Chu G, Shi C, Lin J, Wang S, Wang H, Liu T, Yang H, Li B. Biomechanics in Annulus Fibrosus Degeneration and Regeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1078:409-420. [PMID: 30357635 DOI: 10.1007/978-981-13-0950-2_21] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Degenerative disc degeneration (DDD) is the major cause of low back pain, which seriously affects the life of patients. Current surgical and conservative treatments only relieve the pain temporarily, yet fail to restore the normal biomechanics and functions of healthy spine. Indeed, high recurrence of disc herniation commonly happens after discectomy. Degenerative changes in biomechanical and structural properties of the intervertebral disc (IVD), including fissures in annulus fibrosus (AF) and volume loss of nucleus pulposus (NP), mainly contribute to DDD development. AF plays a critical role in the biomechanical properties of IVD as it structural integrity is essential to confine NP and maintain physiological intradiscal pressure under loading. Maintaining the homeostasis of AF and NP, and thereby IVD, requires regulation of their biomechanics, which is also involved in the onset and subsequent development of AF degeneration. Therefore, it is essential to understand the biomechanical changes of AF during degeneration, which can also provide valuable insights into the repair and regeneration of AF. In this review, we focus on the biomechanical properties of AF tissue associated with its homeostasis and degeneration, and discuss the biomechanical stimulus required for regeneration of AF. We also provide an overview of recent strategies to target and modulate cell mechanics toward AF regeneration.
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Affiliation(s)
- Genglei Chu
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China.,Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Chen Shi
- Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Jun Lin
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Shenghao Wang
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Huan Wang
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China.,Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Tao Liu
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Huilin Yang
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China.,Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China
| | - Bin Li
- Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China. .,Department of Orthopaedic Surgery, The First Affiliated Hospital, Soochow University, Suzhou, Jiangsu, China. .,China Orthopaedic Regenerative Medicine Group (CORMed), Hangzhou, Zhejiang, China.
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19
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Pereira DR, Silva-Correia J, Oliveira JM, Reis RL, Pandit A, Biggs MJ. Nanocellulose reinforced gellan-gum hydrogels as potential biological substitutes for annulus fibrosus tissue regeneration. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2017; 14:897-908. [PMID: 29170112 DOI: 10.1016/j.nano.2017.11.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 11/01/2017] [Accepted: 11/09/2017] [Indexed: 11/30/2022]
Abstract
Intervertebral disc (IVD) degeneration is associated with both structural damage and aging related degeneration. Annulus fibrosus (AF) defects such as annular tears, herniation and discectomy require novel tissue engineering strategies to functionally repair AF tissue. An ideal construct will repair the AF by providing physical and biological support, facilitating regeneration. The presented strategy herein proposes a gellan gum-based construct reinforced with cellulose nanocrystals (nCell) as a biological self-gelling AF substitute. Nanocomposite hydrogels were fabricated and characterized with respect to hydrogel swelling capacity, degradation rate in vitro and mechanical properties. Rheological evaluation on the nanocomposites demonstrated the GGMA reinforcement with nCell promoted matrix entanglement with higher scaffold stiffness observed upon ionic crosslinking. Compressive mechanical tests demonstrated compressive modulus values close to those of the human AF tissue. Furthermore, cell culture studies with encapsulated bovine AF cells indicated that nanocomposite constructs promoted cell viability and a physiologically relevant cell morphology for up to fourteen days in vitro.
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Affiliation(s)
- Diana R Pereira
- 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, Univ. Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Taipas, Guimarães, Portugal; ICVS/3B's-PT Government Associate Laboratory, Braga, Guimarães, Portugal; CÚRAM, SFI Centre for Research in Medical Devices, National University of Ireland, Galway
| | - Joana Silva-Correia
- 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, Univ. Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Taipas, Guimarães, Portugal; ICVS/3B's-PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Joaquim M Oliveira
- 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, Univ. Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Taipas, Guimarães, Portugal; ICVS/3B's-PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Rui L Reis
- 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, Univ. Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Taipas, Guimarães, Portugal; ICVS/3B's-PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Abhay Pandit
- CÚRAM, SFI Centre for Research in Medical Devices, National University of Ireland, Galway
| | - Manus J Biggs
- CÚRAM, SFI Centre for Research in Medical Devices, National University of Ireland, Galway.
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20
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Mengoni M, Kayode O, Sikora SNF, Zapata-Cornelio FY, Gregory DE, Wilcox RK. Annulus fibrosus functional extrafibrillar and fibrous mechanical behaviour: experimental and computational characterisation. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170807. [PMID: 28879014 PMCID: PMC5579130 DOI: 10.1098/rsos.170807] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 07/20/2017] [Indexed: 06/07/2023]
Abstract
The development of current surgical treatments for intervertebral disc damage could benefit from virtual environment accounting for population variations. For such models to be reliable, a relevant description of the mechanical properties of the different tissues and their role in the functional mechanics of the disc is of major importance. The aims of this work were first to assess the physiological hoop strain in the annulus fibrosus in fresh conditions (n = 5) in order to extract a functional behaviour of the extrafibrillar matrix; then to reverse-engineer the annulus fibrosus fibrillar behaviour (n = 6). This was achieved by performing both direct and global controlled calibration of material parameters, accounting for the whole process of experimental design and in silico model methodology. Direct-controlled models are specimen-specific models representing controlled experimental conditions that can be replicated and directly comparing measurements. Validation was performed on another six specimens and a sensitivity study was performed. Hoop strains were measured as 17 ± 3% after 10 min relaxation and 21 ± 4% after 20-25 min relaxation, with no significant difference between the two measurements. The extrafibrillar matrix functional moduli were measured as 1.5 ± 0.7 MPa. Fibre-related material parameters showed large variability, with a variance above 0.28. Direct-controlled calibration and validation provides confidence that the model development methodology can capture the measurable variation within the population of tested specimens.
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Affiliation(s)
- Marlène Mengoni
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK
| | - Oluwasegun Kayode
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK
| | - Sebastien N. F. Sikora
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK
| | - Fernando Y. Zapata-Cornelio
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK
| | - Diane E. Gregory
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - Ruth K. Wilcox
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK
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Tavakoli J. Tissue Engineering of the Intervertebral Disc's Annulus Fibrosus: A Scaffold-Based Review Study. Tissue Eng Regen Med 2017; 14:81-91. [PMID: 30603465 PMCID: PMC6171584 DOI: 10.1007/s13770-017-0024-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/10/2016] [Accepted: 06/08/2016] [Indexed: 12/11/2022] Open
Abstract
Tissue engineering as a high technology solution for treating disc's problem has been the focus of some researches recently; however, the upcoming successful results in this area depends on understanding the complexities of biology and engineering interface. Whereas the major responsibility of the nucleus pulposus is to provide a sustainable hydrated environment within the disc, the function of the annulus fibrosus (AF) is more mechanical, facilitating joint mobility and preventing radial bulging by confining of the central part, which makes the AF reconstruction important. Although the body of knowledge regarding the AF tissue engineering has grown rapidly, the opportunities to improve current understanding of how artificial scaffolds are able to mimic the AF concentric structure-including inter-lamellar matrix and cross-bridges-addressed unresolved research questions. The aim of this literature review was to collect and discuss, from the international scientific literature, information about tissue engineering of the AF based on scaffold fabrication and material properties, useful for developing new strategies in disc tissue engineering. The key parameter of this research was understanding if role of cross-bridges and inter-lamellar matrix has been considered on tissue engineering of the AF.
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Affiliation(s)
- Javad Tavakoli
- Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, Adelaide, SA 5042 Australia
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22
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Connizzo BK, Adams SM, Adams TH, Birk DE, Soslowsky LJ. Collagen V expression is crucial in regional development of the supraspinatus tendon. J Orthop Res 2016; 34:2154-2161. [PMID: 28005290 PMCID: PMC5189919 DOI: 10.1002/jor.23246] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 03/23/2016] [Indexed: 02/04/2023]
Abstract
Manipulations in cell culture and mouse models have demonstrated that reduction of collagen V results in altered fibril structure and matrix assembly. A tissue-dependent role for collagen V in determining mechanical function was recently established, but its role in determining regional properties has not been addressed. The objective of this study was to define the role(s) of collagen V expression in establishing the site-specific properties of the supraspinatus tendon. The insertion and midsubstance of tendons from wild type, heterozygous and tendon/ligament-specific null mice were assessed for crimp morphology, fibril morphology, cell morphology, as well as total collagen and pyridinoline cross-link (PYD) content. Fibril morphology was altered at the midsubstance of both groups with larger, but fewer, fibrils and no change in cell morphology or collagen compared to the wild type controls. In contrast, a significant disruption of fibril assembly was observed at the insertion site of the null group with the presence of structurally aberrant fibrils. Alterations were also present in cell density and PYD content. Altogether, these results demonstrate that collagen V plays a crucial role in determining region-specific differences in mouse supraspinatus tendon structure. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2154-2161, 2016.
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Affiliation(s)
- Brianne K. Connizzo
- McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
| | - Sheila M. Adams
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612
| | - Thomas H. Adams
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612
| | - David E. Birk
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612
| | - Louis J. Soslowsky
- McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
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23
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Vo NV, Hartman RA, Patil PR, Risbud MV, Kletsas D, Iatridis JC, Hoyland JA, Le Maitre CL, Sowa GA, Kang JD. Molecular mechanisms of biological aging in intervertebral discs. J Orthop Res 2016; 34:1289-306. [PMID: 26890203 PMCID: PMC4988945 DOI: 10.1002/jor.23195] [Citation(s) in RCA: 240] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 02/03/2016] [Indexed: 02/04/2023]
Abstract
Advanced age is the greatest risk factor for the majority of human ailments, including spine-related chronic disability and back pain, which stem from age-associated intervertebral disc degeneration (IDD). Given the rapid global rise in the aging population, understanding the biology of intervertebral disc aging in order to develop effective therapeutic interventions to combat the adverse effects of aging on disc health is now imperative. Fortunately, recent advances in aging research have begun to shed light on the basic biological process of aging. Here we review some of these insights and organize the complex process of disc aging into three different phases to guide research efforts to understand the biology of disc aging. The objective of this review is to provide an overview of the current knowledge and the recent progress made to elucidate specific molecular mechanisms underlying disc aging. In particular, studies over the last few years have uncovered cellular senescence and genomic instability as important drivers of disc aging. Supporting evidence comes from DNA repair-deficient animal models that show increased disc cellular senescence and accelerated disc aging. Additionally, stress-induced senescent cells have now been well documented to secrete catabolic factors, which can negatively impact the physiology of neighboring cells and ECM. These along with other molecular drivers of aging are reviewed in depth to shed crucial insights into the underlying mechanisms of age-related disc degeneration. We also highlight molecular targets for novel therapies and emerging candidate therapeutics that may mitigate age-associated IDD. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1289-1306, 2016.
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Affiliation(s)
- Nam V. Vo
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Robert A. Hartman
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Prashanti R. Patil
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Makarand V. Risbud
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
| | - Dimitris Kletsas
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Centre for Scientific Research “Demokritos”, Athens, Greece
| | - James C. Iatridis
- Leni & Peter W May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Judith A. Hoyland
- Centre for Tissue Injury and Repair, Faculty of Medical and Human Sciences, University of Manchester M13 9PT and NIHR Manchester Musculoskeletal Biomedical Research Unit, Manchester Academic Health Science Centre, Manchester, UK
| | - Christine L. Le Maitre
- Musculoskeletal and Regenerative Medicine Research Group, Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, S1 1WB, UK
| | - Gwendolyn A. Sowa
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - James D. Kang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Bezci SE, Nandy A, O'Connell GD. Effect of Hydration on Healthy Intervertebral Disk Mechanical Stiffness. J Biomech Eng 2016; 137:101007. [PMID: 26300418 DOI: 10.1115/1.4031416] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Indexed: 11/08/2022]
Abstract
The intervertebral disk has an excellent swelling capacity to absorb water, which is thought to be largely due to the high proteoglycan composition. Injury, aging, degeneration, and diurnal loading are all noted by a significant decrease in water content and tissue hydration. The objective of this study was to evaluate the effect of hydration, through osmotic loading, on tissue swelling and compressive stiffness of healthy intervertebral disks. The wet weight of nucleus pulposus (NP) and annulus fibrosus (AF) explants following swelling was 50% or greater, demonstrating significant ability to absorb water under all osmotic loading conditions (0.015 M-3.0 M phosphate buffered saline (PBS)). Estimated NP residual strains, calculated from the swelling ratio, were approximately 1.5 × greater than AF residual strains. Compressive stiffness increased with hyperosmotic loading, which is thought to be due to material compaction from osmotic-loading and the nonlinear mechanical behavior. Importantly, this study demonstrated that residual strains and material properties are greatly dependent on osmotic loading. The findings of this study support the notion that swelling properties from osmotic loading will be important for accurately describing the effect of degeneration and injury on disk mechanics. Furthermore, the tissue swelling will be an important consideration for developing biological repair strategies aimed at restoring mechanical behavior toward a healthy disk.
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Kobielarz M, Szotek S, Głowacki M, Dawidowicz J, Pezowicz C. Qualitative and quantitative assessment of collagen and elastin in annulus fibrosus of the physiologic and scoliotic intervertebral discs. J Mech Behav Biomed Mater 2016; 62:45-56. [PMID: 27177214 DOI: 10.1016/j.jmbbm.2016.04.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/15/2016] [Accepted: 04/25/2016] [Indexed: 02/02/2023]
Abstract
The biophysical properties of the annulus fibrosus of the intervertebral disc are determined by collagen and elastin fibres. The progression of scoliosis is accompanied by a number of pathological changes concerning these structural proteins. This is a major cause of dysfunction of the intervertebral disc. The object of the study were annulus fibrosus samples excised from intervertebral discs of healthy subjects and patients treated surgically for scoliosis in the thoracolumbar or lumbar spine. The research material was subjected to structural analysis by light microscopy and quantitative analysis of the content of collagen types I, II, III and IV as well as elastin by immunoenzymatic test (ELISA). A statistical analysis was conducted to assess the impact of the sampling site (Mann-Whitney test, α=0.05) and scoliosis (Wilcoxon matched pairs test, α=0.05) on the obtained results. The microscopic studies conducted on scoliotic annulus fibrosus showed a significant architectural distortion of collagen and elastin fibres. Quantitative biochemical assays demonstrated region-dependent distribution of only collagen types I and II in the case of healthy intervertebral discs whereas in the case of scoliotic discs region-dependent distribution concerned all examined proteins of the extracellular matrix. Comparison of scoliotic and healthy annulus fibrosus revealed a significant decrease in the content of collagen type I and elastin as well as a slight increase in the proportion of collagen types III and IV. The content of collagen type II did not differ significantly between both groups. The observed anomalies are a manifestation of degenerative changes affecting annulus fibrosus of the intervertebral disc in patients suffering from scoliosis.
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Affiliation(s)
- Magdalena Kobielarz
- Department of Biomedical Engineering, Mechatronics and Theory of Mechanisms, Wroclaw University of Technology, Łukasiewicza 7/9, 50-371 Wroclaw, Poland
| | - Sylwia Szotek
- Department of Biomedical Engineering, Mechatronics and Theory of Mechanisms, Wroclaw University of Technology, Łukasiewicza 7/9, 50-371 Wroclaw, Poland.
| | - Maciej Głowacki
- Department of Paediatric Orthopaedics, Karol Marcinkowski University of Medical Sciences, 28 Czerwca 1956r., 61-545 Poznan, Poland
| | | | - Celina Pezowicz
- Department of Biomedical Engineering, Mechatronics and Theory of Mechanisms, Wroclaw University of Technology, Łukasiewicza 7/9, 50-371 Wroclaw, Poland
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Connizzo BK, Adams SM, Adams TH, Jawad AF, Birk DE, Soslowsky LJ. Multiscale regression modeling in mouse supraspinatus tendons reveals that dynamic processes act as mediators in structure-function relationships. J Biomech 2016; 49:1649-1657. [PMID: 27067362 DOI: 10.1016/j.jbiomech.2016.03.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/11/2016] [Accepted: 03/28/2016] [Indexed: 12/26/2022]
Abstract
Recent advances in technology have allowed for the measurement of dynamic processes (re-alignment, crimp, deformation, sliding), but only a limited number of studies have investigated their relationship with mechanical properties. The overall objective of this study was to investigate the role of composition, structure, and the dynamic response to load in predicting tendon mechanical properties in a multi-level fashion mimicking native hierarchical collagen structure. Multiple linear regression models were investigated to determine the relationships between composition/structure, dynamic processes, and mechanical properties. Mediation was then used to determine if dynamic processes mediated structure-function relationships. Dynamic processes were strong predictors of mechanical properties. These predictions were location-dependent, with the insertion site utilizing all four dynamic responses and the midsubstance responding primarily with fibril deformation and sliding. In addition, dynamic processes were moderately predicted by composition and structure in a regionally-dependent manner. Finally, dynamic processes were partial mediators of the relationship between composition/structure and mechanical function, and results suggested that mediation is likely shared between multiple dynamic processes. In conclusion, the mechanical properties at the midsubstance of the tendon are controlled primarily by fibril structure and this region responds to load via fibril deformation and sliding. Conversely, the mechanical function at the insertion site is controlled by many other important parameters and the region responds to load via all four dynamic mechanisms. Overall, this study presents a strong foundation on which to design future experimental and modeling efforts in order to fully understand the complex structure-function relationships present in tendon.
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Affiliation(s)
- Brianne K Connizzo
- McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA 19104-6081, United States
| | - Sheila M Adams
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, United States
| | - Thomas H Adams
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, United States
| | - Abbas F Jawad
- Division of Biostatistics, Department of Pediatrics, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - David E Birk
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, United States
| | - Louis J Soslowsky
- McKay Orthopaedic Research Laboratory, University of Pennsylvania, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA 19104-6081, United States.
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27
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Derivation of inter-lamellar behaviour of the intervertebral disc annulus. J Mech Behav Biomed Mater 2015; 48:164-172. [PMID: 25955558 PMCID: PMC4455908 DOI: 10.1016/j.jmbbm.2015.03.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/16/2015] [Accepted: 03/23/2015] [Indexed: 11/30/2022]
Abstract
The inter-lamellar connectivity of the annulus fibrosus in the intervertebral disc has been shown to affect the prediction of the overall disc behaviour in computational models. Using a combined experimental and computational approach, the inter-lamellar mechanical behaviour of the disc annulus was investigated under conditions of radial loading. Twenty-seven specimens of anterior annulus fibrosus were dissected from 12 discs taken from four frozen ovine thoracolumbar spines. Specimens were grouped depending on their radial provenance within the annulus fibrosus. Standard tensile tests were performed. In addition, micro-tensile tests under microscopy were used to observe the displacement of the lamellae and inter-lamellar connections. Finite elements models matching the experimental protocols were developed with specimen-specific geometries and boundary conditions assuming a known lamellar behaviour. An optimisation process was used to derive the interface stiffness values for each group. The assumption of a linear cohesive interface was used to model the behaviour of the inter-lamellar connectivity. The interface stiffness values derived from the optimisation process were consistently higher than the corresponding lamellar values. The interface stiffness values of the outer annulus were from 43% to 75% higher than those of the inner annulus. Tangential stiffness values for the interface were from 6% to 39% higher than normal stiffness values within each group and similar to values reported by other investigators. These results reflect the intricate fibrous nature of the inter-lamellar connectivity and provide values for the representation of the inter-lamellar behaviour at a continuum level.
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28
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Li J, Liu C, Guo Q, Yang H, Li B. Regional variations in the cellular, biochemical, and biomechanical characteristics of rabbit annulus fibrosus. PLoS One 2014; 9:e91799. [PMID: 24622282 PMCID: PMC3951500 DOI: 10.1371/journal.pone.0091799] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 02/14/2014] [Indexed: 01/05/2023] Open
Abstract
Tissue engineering of annulus fibrosus (AF), the essential load-bearing disc component, remains challenging due to the intrinsic heterogeneity of AF tissue. In order to provide a set of characterization data of AF tissue, which serve as the benchmark for constructing tissue engineered AF, we analyzed tissues and cells from various radial zones of AF, i.e., inner AF (iAF), middle AF (mAF), and outer AF (oAF), using a rabbit model. We found that a radial gradient in the cellular, biochemical, and biomechanical characteristics of rabbit AF existed. Specifically, the iAF cells (iAFCs) had the highest expression of collagen-II and aggrecan genes, while oAF cells (oAFCs) had the highest collagen-I gene expression. The contents of DNA, total collagen and collagen-I sequentially increased from iAF, mAF to oAF, while glycosaminoglycan (GAG) and collagen-II levels decreased. The cell traction forces of primary AFCs gradually decreased from iAFCs, mAFCs to oAFCs, being 336.6±155.3, 199.0±158.8, and 123.8±76.1 Pa, respectively. The storage moduli of iAF, mAF, and oAF were 0.032±0.002, 2.121±0.656, and 4.130±0.159 MPa, respectively. These measurements have established a set of reference data for functional evaluation of the efficacy of AF tissue engineering strategies using a convenient and cost-effective rabbit model, the findings of which may be further translated to human research.
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Affiliation(s)
- Jun Li
- Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
| | - Chen Liu
- Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
| | - Qianping Guo
- Orthopedic Institute, Soochow University, Suzhou, Jiangsu, China
| | - Huilin Yang
- Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
- Orthopedic Institute, Soochow University, Suzhou, Jiangsu, China
| | - Bin Li
- Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
- Orthopedic Institute, Soochow University, Suzhou, Jiangsu, China
- * E-mail:
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Elastic, permeability and swelling properties of human intervertebral disc tissues: A benchmark for tissue engineering. J Biomech 2013; 47:2088-94. [PMID: 24438768 DOI: 10.1016/j.jbiomech.2013.12.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 12/10/2013] [Accepted: 12/16/2013] [Indexed: 01/06/2023]
Abstract
The aim of functional tissue engineering is to repair and replace tissues that have a biomechanical function, i.e., connective orthopaedic tissues. To do this, it is necessary to have accurate benchmarks for the elastic, permeability, and swelling (i.e., biphasic-swelling) properties of native tissues. However, in the case of the intervertebral disc, the biphasic-swelling properties of individual tissues reported in the literature exhibit great variation and even span several orders of magnitude. This variation is probably caused by differences in the testing protocols and the constitutive models used to analyze the data. Therefore, the objective of this study was to measure the human lumbar disc annulus fibrosus (AF), nucleus pulposus (NP), and cartilaginous endplates (CEP) biphasic-swelling properties using a consistent experimental protocol and analyses. The testing protocol was composed of a swelling period followed by multiple confined compression ramps. To analyze the confined compression data, the tissues were modeled using a biphasic-swelling model, which augments the standard biphasic model through the addition of a deformation-dependent osmotic pressure term. This model allows considering the swelling deformations and the contribution of osmotic pressure in the analysis of the experimental data. The swelling stretch was not different between the disc regions (AF: 1.28±0.16; NP: 1.73±0.74; CEP: 1.29±0.26), with a total average of 1.42. The aggregate modulus (Ha) of the extra-fibrillar matrix was higher in the CEP (390kPa) compared to the NP (100kPa) or AF (30kPa). The permeability was very different across tissue regions, with the AF permeability (64 E(-16)m(4)/Ns) higher than the NP and CEP (~5.5 E(-16)m(4)/Ns). Additionally, a normalized time-constant (3000s) for the stress relaxation was similar for all the disc tissues. The properties measured in this study are important as benchmarks for tissue engineering and for modeling the disc's mechanical behavior and transport.
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