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Sherlock B, Chen J, Mansfield J, Green E, Winlove C. Biophotonic tools for probing extracellular matrix mechanics. Matrix Biol Plus 2021; 12:100093. [PMID: 34934939 PMCID: PMC8661043 DOI: 10.1016/j.mbplus.2021.100093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 11/07/2021] [Accepted: 11/11/2021] [Indexed: 12/11/2022] Open
Abstract
The complex, hierarchical and heterogeneous biomechanics of the extracellular matrix (ECM) are central to the health of multicellular organisms. Characterising the distribution, dynamics and above all else origins of ECM biomechanics are challenges that have captivated researchers for decades. Recently, a suite of biophotonics techniques have emerged as powerful new tools to investigate ECM biomechanics. In this mini-review, we discuss how the non-destructive, sub-micron resolution imaging capabilities of Raman spectroscopy and nonlinear microscopy are being used to interrogate the biomechanics of thick, living tissues. These high speed, label-free techniques are implemented during mechanical testing, providing unprecedented insight into the compositional and structural response of the ECM to changes in the mechanical environment.
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Affiliation(s)
- B.E. Sherlock
- College of Medicine and Health, University of Exeter, Exeter EX1 2LU, United Kingdom
| | - J. Chen
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom
| | - J.C. Mansfield
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom
| | - E. Green
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom
| | - C.P. Winlove
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom
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Li X, Lu Y, Wang Y, Zhou S, Li L, Zhao F. Thermo-responsive injectable naringin-loaded hydrogel polymerised sodium alginate/bioglass delivery for articular cartilage. Drug Deliv 2021; 28:1290-1300. [PMID: 34176372 PMCID: PMC8238061 DOI: 10.1080/10717544.2021.1938752] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In the human body, joint cartilage is of great importance. It has long been a big therapeutic problem to fix joint cartilage lesions as it appears due to different conditions. Recent stories have shown that the cartilage replacement process must delay the extracellular (ECM) cartilage deterioration and modulate the host's inflammation response. For the reconstruction of the articular cartilage, drug-loaded injectable hydrogels were developed. This hydrogel could retain the chondrocyte phenotype, but the host's inflammatory reaction could also be controlled. The bioglass (BG)/sodium alginate (SA) injectable hydrogels was combined with agarose (AG)/Naringin hydrogel in injectable thermal response for articular cartilage regeneration with a non-chargeable hydrogel that contains both Naringin and BG (Naringin–BG hydrogels). The Naringin–BG hydrogel has an adequate swelling ratio that encourages the fusion of tissue formed with host tissue and enables the gradual release of Naringin bioavailabilities enhanced in situ. The Naringin–BG hydrogel can upgrade the typical chondrocyte phenotype by upregulating aggrecan, SRY-box 9, and collagen type II alpha one chain. It may also stimulate the polarization of M2 macrophage, lower inflammations, and prevent ECM degradations through the decrease of the expressions of the indictable metalloproteinase-13 matrix, nitric oxide synthase, and metalloproteinase-1 matrix. The formed tissues were identical to normal tissues and firmly incorporated with the surrounding tissue after administering the Naringin–BG hydrogels into the rat model articular cartilage defects. Then the injectable Naringin–BG hydrogel increases the bioavailable content of Naringin and retains the chondrocyte phenotype.
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Affiliation(s)
- Xiang Li
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Yang Lu
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Yuxin Wang
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Shengji Zhou
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
| | - Liangping Li
- Department of Surgery, The Second Affiliated Hospital of Zhejiang University, School of Medicine, Hangzhou, China
| | - Fengchao Zhao
- Department of Orthopaedic Surgery, The First Affiliated Hospital, Zhejiang University, School of Medicine, Hangzhou, China
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Statham P, Jones E, Jennings LM, Fermor HL. Reproducing the Biomechanical Environment of the Chondrocyte for Cartilage Tissue Engineering. TISSUE ENGINEERING PART B-REVIEWS 2021; 28:405-420. [PMID: 33726527 DOI: 10.1089/ten.teb.2020.0373] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
It is well known that the biomechanical and tribological performance of articular cartilage is inextricably linked to its extracellular matrix (ECM) structure and zonal heterogeneity. Furthermore, it is understood that the presence of native ECM components, such as collagen II and aggrecan, promote healthy homeostasis in the resident chondrocytes. What is less frequently discussed is how chondrocyte metabolism is related to the extracellular mechanical environment, at both the macro and microscale. The chondrocyte is in immediate contact with the pericellular matrix of the chondron, which acts as a mechanocoupler, transmitting external applied loads from the ECM to the chondrocyte. Therefore, components of the pericellular matrix also play essential roles in chondrocyte mechanotransduction and metabolism. Recreating the biomechanical environment through tuning material properties of a scaffold and/or the use of external cyclic loading can induce biosynthetic responses in chondrocytes. Decellularized scaffolds, which retain the native tissue macro- and microstructure also represent an effective means of recapitulating such an environment. The use of such techniques in tissue engineering applications can ensure the regeneration of skeletally mature articular cartilage with appropriate biomechanical and tribological properties to restore joint function. Despite the pivotal role in graft maturation and performance, biomechanical and tribological properties of such interventions is often underrepresented. This review outlines the role of biomechanics in relation to native cartilage performance and chondrocyte metabolism, and how application of this theory can enhance the future development and successful translation of biomechanically relevant tissue engineering interventions. Impact statement Physiological cartilage function is a key criterion in the success of a cartilage tissue engineering solution. The in situ performance is dependent on the initial scaffold design as well as extracellular matrix deposition by endogenous or exogenous cells. Both biological and biomechanical stimuli serve as key regulators of cartilage homeostasis and maturation of the resulting tissue-engineered graft. An improved understanding of the influence of biomechanics on cellular function and consideration of the final biomechanical and tribological performance will help in the successful development and translation of tissue-engineered grafts to restore natural joint function postcartilage trauma or osteoarthritic degeneration, delaying the requirement for prosthetic intervention.
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Affiliation(s)
- Patrick Statham
- Institute of Medical and Biological Engineering, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Elena Jones
- Leeds Institute of Rheumatic and Musculoskeletal Disease, University of Leeds, Leeds, United Kingdom
| | - Louise M Jennings
- Institute of Medical and Biological Engineering, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom
| | - Hazel L Fermor
- Institute of Medical and Biological Engineering, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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Cao Y, Cheng P, Sang S, Xiang C, An Y, Wei X, Shen Z, Zhang Y, Li P. Mesenchymal stem cells loaded on 3D-printed gradient poly(ε-caprolactone)/methacrylated alginate composite scaffolds for cartilage tissue engineering. Regen Biomater 2021; 8:rbab019. [PMID: 34211731 PMCID: PMC8240606 DOI: 10.1093/rb/rbab019] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/08/2021] [Accepted: 04/12/2021] [Indexed: 01/06/2023] Open
Abstract
Cartilage has limited self-repair ability due to its avascular, alymphatic and aneural features. The combination of three-dimensional (3D) printing and tissue engineering provides an up-and-coming approach to address this issue. Here, we designed and fabricated a tri-layered (superficial layer (SL), middle layer (ML) and deep layer (DL)) stratified scaffold, inspired by the architecture of collagen fibers in native cartilage tissue. The scaffold was composed of 3D printed depth-dependent gradient poly(ε-caprolactone) (PCL) impregnated with methacrylated alginate (ALMA), and its morphological analysis and mechanical properties were tested. To prove the feasibility of the composite scaffolds for cartilage regeneration, the viability, proliferation, collagen deposition and chondrogenic differentiation of embedded rat bone marrow mesenchymal stem cells (BMSCs) in the scaffolds were assessed by Live/dead assay, CCK-8, DNA content, cell morphology, immunofluorescence and real-time reverse transcription polymerase chain reaction. BMSCs-loaded gradient PCL/ALMA scaffolds showed excellent cell survival, cell proliferation, cell morphology, collagen II deposition and hopeful chondrogenic differentiation compared with three individual-layer scaffolds. Hence, our study demonstrates the potential use of the gradient PCL/ALMA construct for enhanced cartilage tissue engineering.
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Affiliation(s)
- Yanyan Cao
- Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, MicroNano System Research Center, College of Information and Computer, Taiyuan University of Technology, Taiyuan 030024, China.,College of Information Science and Engineering, Hebei North University, Zhangjiakou 075000, China
| | - Peng Cheng
- Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Department of Orthopedics, The Second Hospital of Shanxi Medical University, Taiyuan 030001, China
| | - Shengbo Sang
- Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, MicroNano System Research Center, College of Information and Computer, Taiyuan University of Technology, Taiyuan 030024, China
| | - Chuan Xiang
- Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Department of Orthopedics, The Second Hospital of Shanxi Medical University, Taiyuan 030001, China
| | - Yang An
- Department of Plastic Surgery, Peking University Third Hospital, Beijing 100191, China
| | - Xiaochun Wei
- Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Department of Orthopedics, The Second Hospital of Shanxi Medical University, Taiyuan 030001, China
| | - Zhizhong Shen
- Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, MicroNano System Research Center, College of Information and Computer, Taiyuan University of Technology, Taiyuan 030024, China
| | - Yixia Zhang
- Department of Biomedical Engineering, College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Pengcui Li
- Shanxi Key Laboratory of Bone and Soft Tissue Injury Repair, Department of Orthopedics, The Second Hospital of Shanxi Medical University, Taiyuan 030001, China
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Ravanfar M, Yao G. Simultaneous tractography and elastography imaging of the zone-specific structural and mechanical responses in articular cartilage under compressive loading. BIOMEDICAL OPTICS EXPRESS 2019; 10:3241-3256. [PMID: 31467777 PMCID: PMC6706024 DOI: 10.1364/boe.10.003241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 05/09/2023]
Abstract
We quantified the precise zonal cartilage structural and mechanical responses to unconfined compressive loading by using simultaneous PSOCT based optical tractography and elastography imaging. Twelve bovine knee articular cartilage samples from six animals were imaged under bulk compression from 4% to 20%. The results revealed strong evidence that the conventional radial zone could be divided into two sub-zones with distinct mechanical properties. The "upper" part of the radial zone played a critical role in "absorbing" the mechanical compression. The study also showed that the zonal fiber organization greatly affected the cartilage structural and mechanical responses. A strong correlation was observed between the optical birefringence and logarithm of the Young's modulus. These new results provide useful information for improving mechanical modeling of articular cartilage and developing better cartilage-mimetic biomaterials.
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Mansfield JC, Mandalia V, Toms A, Winlove CP, Brasselet S. Collagen reorganization in cartilage under strain probed by polarization sensitive second harmonic generation microscopy. J R Soc Interface 2019; 16:20180611. [PMID: 30958161 PMCID: PMC6364654 DOI: 10.1098/rsif.2018.0611] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 12/20/2018] [Indexed: 11/12/2022] Open
Abstract
Type II collagen fibril diameters in cartilage are beneath the diffraction limit of optical microscopy, which makes the assessment of collagen organization very challenging. In this work we use polarization sensitive second harmonic generation (P-SHG) imaging to map collagen organization in articular cartilage, addressing in particular its behaviour under strain and changes which occur in osteoarthritis. P-SHG yields two parameters, molecular order and orientation, which provide measures of the degree of organization both at the molecular scale (below the diffraction limit) and above a few hundred nanometres (at the image pixel size). P-SHG clearly demonstrates the zonal collagen architecture and reveals differences in the structure of the fibrils around chondrocytes. P-SHG also reveals sub-micron scale fibril re-organization in cartilage strips exposed to tensile loading, with an increase in local organization in the superficial zone which weakly correlates with tensile modulus. Finally, P-SHG is used to investigate osteoarthritic cartilage from total knee replacement surgery, and reveals widespread heterogeneity across samples both microscale fibril orientations and their sub-micron organization. By addressing collagen fibril structure on scales intermediate between conventional light and electron microscopy, this study provides new insights into collagen micromechanics and mechanisms of degradation.
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Affiliation(s)
- Jessica C. Mansfield
- Physics, College of Engineering Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Vipul Mandalia
- Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital, Barrack Road, Exeter EX2 5DW, UK
| | - Andrew Toms
- Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital, Barrack Road, Exeter EX2 5DW, UK
| | - C. Peter Winlove
- Physics, College of Engineering Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Sophie Brasselet
- Institut Fresnel, CNRS, Aix Marseille Univ, Centrale Marseille, 13013 Marseille, France
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Composition, structure and tensile biomechanical properties of equine articular cartilage during growth and maturation. Sci Rep 2018; 8:11357. [PMID: 30054498 PMCID: PMC6063957 DOI: 10.1038/s41598-018-29655-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 07/13/2018] [Indexed: 02/07/2023] Open
Abstract
Articular cartilage undergoes structural and biochemical changes during maturation, but the knowledge on how these changes relate to articular cartilage function at different stages of maturation is lacking. Equine articular cartilage samples of four different maturation levels (newborn, 5-month-old, 11-month-old and adult) were collected (N = 25). Biomechanical tensile testing, Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy were used to study the tensile, biochemical and structural properties of articular cartilage, respectively. The tensile modulus was highest and the breaking energy lowest in the newborn group. The collagen and the proteoglycan contents increased with age. The collagen orientation developed with age into an arcade-like orientation. The collagen content, proteoglycan content, and collagen orientation were important predictors of the tensile modulus (p < 0.05 in multivariable regression) and correlated significantly also with the breaking energy (p < 0.05 in multivariable regression). Partial least squares regression analysis of FTIR-MS data provided accurate predictions for the tensile modulus (r = 0.79) and the breaking energy (r = 0.65). To conclude, the composition and structure of equine articular cartilage undergoes changes with depth that alter functional properties during maturation, with the typical properties of mature tissue reached at the age of 5-11 months.
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Huynh RN, Nehmetallah G, Raub CB. Noninvasive assessment of articular cartilage surface damage using reflected polarized light microscopy. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:65001. [PMID: 28586854 DOI: 10.1117/1.jbo.22.6.065001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 05/15/2017] [Indexed: 05/02/2023]
Abstract
Articular surface damage occurs to cartilage during normal aging, osteoarthritis, and in trauma. A noninvasive assessment of cartilage microstructural alterations is useful for studies involving cartilage explants. This study evaluates polarized reflectance microscopy as a tool to assess surface damage to cartilage explants caused by mechanical scraping and enzymatic degradation. Adult bovine articular cartilage explants were scraped, incubated in collagenase, or underwent scrape and collagenase treatments. In an additional experiment, cartilage explants were subject to scrapes at graduated levels of severity. Polarized reflectance parameters were compared with India ink surface staining, features of histological sections, changes in explant wet weight and thickness, and chondrocyte viability. The polarized reflectance signal was sensitive to surface scrape damage and revealed individual scrape features consistent with India ink marks. Following surface treatments, the reflectance contrast parameter was elevated and correlated with image area fraction of India ink. After extensive scraping, polarized reflectance contrast and chondrocyte viability were lower than that from untreated explants. As part of this work, a mathematical model was developed and confirmed the trend in the reflectance signal due to changes in surface scattering and subsurface birefringence. These results demonstrate the effectiveness of polarized reflectance microscopy to sensitively assess surface microstructural alterations in articular cartilage explants.
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Affiliation(s)
- Ruby N Huynh
- The Catholic University of America, Department of Biomedical Engineering, Washington, United States
| | - George Nehmetallah
- The Catholic University of America, Department of Electrical Engineering, Washington, United States
| | - Christopher B Raub
- The Catholic University of America, Department of Biomedical Engineering, Washington, United States
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Bell JS, Adio AO, Pitt A, Hayman L, Thorn CE, Shore AC, Whatmore JL, Winlove CP. Microstructure and mechanics of human resistance arteries. Am J Physiol Heart Circ Physiol 2016; 311:H1560-H1568. [PMID: 27663767 PMCID: PMC5206342 DOI: 10.1152/ajpheart.00002.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 09/17/2016] [Indexed: 12/26/2022]
Abstract
Vascular diseases such as diabetes and hypertension cause changes to the vasculature that can lead to vessel stiffening and the loss of vasoactivity. The microstructural bases of these changes are not presently fully understood. We present a new methodology for stain-free visualization, at a microscopic scale, of the morphology of the main passive components of the walls of unfixed resistance arteries and their response to changes in transmural pressure. Human resistance arteries were dissected from subcutaneous fat biopsies, mounted on a perfusion myograph, and imaged at varying transmural pressures using a multimodal nonlinear microscope. High-resolution three-dimensional images of elastic fibers, collagen, and cell nuclei were constructed. The honeycomb structure of the elastic fibers comprising the internal elastic layer became visible at a transmural pressure of 30 mmHg. The adventitia, comprising wavy collagen fibers punctuated by straight elastic fibers, thinned under pressure as the collagen network straightened and pulled taut. Quantitative measurements of fiber orientation were made as a function of pressure. A multilayer analytical model was used to calculate the stiffness and stress in each layer. The adventitia was calculated to be up to 10 times as stiff as the media and experienced up to 8 times the stress, depending on lumen diameter. This work reveals that pressure-induced reorganization of fibrous proteins gives rise to very high local strain fields and highlights the unique mechanical roles of both fibrous networks. It thereby provides a basis for understanding the micromechanical significance of structural changes that occur with age and disease.
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Affiliation(s)
- J S Bell
- Department of Physics, University of Exeter, Exeter, United Kingdom;
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, University of Exeter, Exeter, United Kingdom
| | - A O Adio
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Sciences, University of Exeter Medical School and NIHR Exeter Clinical Research Facility, Exeter, United Kingdom; and
| | - A Pitt
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Sciences, University of Exeter Medical School and NIHR Exeter Clinical Research Facility, Exeter, United Kingdom; and
| | - L Hayman
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Sciences, University of Exeter Medical School and NIHR Exeter Clinical Research Facility, Exeter, United Kingdom; and
| | - C E Thorn
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Sciences, University of Exeter Medical School and NIHR Exeter Clinical Research Facility, Exeter, United Kingdom; and
| | - A C Shore
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Sciences, University of Exeter Medical School and NIHR Exeter Clinical Research Facility, Exeter, United Kingdom; and
| | - J L Whatmore
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, University of Exeter, Exeter, United Kingdom
| | - C P Winlove
- Department of Physics, University of Exeter, Exeter, United Kingdom
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10
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Osteoarthritis year in review 2015: mechanics. Osteoarthritis Cartilage 2016; 24:27-35. [PMID: 26707990 PMCID: PMC4693146 DOI: 10.1016/j.joca.2015.08.018] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 08/13/2015] [Accepted: 08/29/2015] [Indexed: 02/02/2023]
Abstract
Motivated by the conceptual framework of multi-scale biomechanics, this narrative review highlights recent major advances with a focus on gait and joint kinematics, then tissue-level mechanics, cell mechanics and mechanotransduction, matrix mechanics, and finally the nanoscale mechanics of matrix macromolecules. A literature review was conducted from January 2014 to April 2015 using PubMed to identify major developments in mechanics related to osteoarthritis (OA). Studies of knee adduction, flexion, rotation, and contact mechanics have extended our understanding of medial compartment loading. In turn, advances in measurement methodologies have shown how injuries to both the meniscus and ligaments, together, can alter joint kinematics. At the tissue scale, novel findings have emerged regarding the mechanics of the meniscus as well as cartilage superficial zone. Moving to the cell level, poroelastic and poro-viscoelastic mechanisms underlying chondrocyte deformation have been reported, along with the response to osmotic stress. Further developments have emerged on the role of calcium signaling in chondrocyte mechanobiology, including exciting findings on the function of mechanically activated cation channels newly found to be expressed in chondrocytes. Finally, AFM-based nano-rheology systems have enabled studies of thin murine tissues and brush layers of matrix molecules over a wide range of loading rates including high rates corresponding to impact injury. With OA acknowledged to be a disease of the joint as an organ, understanding mechanical behavior at each length scale helps to elucidate the connections between cell biology, matrix biochemistry and tissue structure/function that may play a role in the pathomechanics of OA.
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Lewis PN, White TL, Young RD, Bell JS, Winlove CP, Meek KM. Three-dimensional arrangement of elastic fibers in the human corneal stroma. Exp Eye Res 2015; 146:43-53. [PMID: 26704458 PMCID: PMC4889784 DOI: 10.1016/j.exer.2015.12.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/09/2015] [Accepted: 12/10/2015] [Indexed: 01/26/2023]
Abstract
The cornea is the main refracting lens in the eye. As part of the outer tunic it has to be resilient, a property conferred by the organisation of the constituent collagen. It also has to be sufficiently elastic to regain its exact shape when deformed, in order not to distort the retinal image. The basis of this elasticity is not fully understood. The purpose of this study was to characterise in three dimensions the arrangement and distribution of elastic fibers in the human corneal stroma, using serial block face scanning electron microscopy. We have demonstrated that there exists a complex network of elastic fibers that appear to originate in the sclera or limbus. These appear as elastic sheets in the limbus and peripheral cornea immediately above the trabecular meshwork which itself appears to extend above Descemet's membrane in the peripheral stroma. From these sheets, elastic fibers extend into the cornea; moving centrally they bifurcate and trifurcate into narrower fibers and are concentrated in the posterior stroma immediately above Descemet's membrane. We contend that elastic sheets will play an important role in the biomechanical deformation and recovery of the peripheral cornea. The network may also have practical implications for understanding the structural basis behind a number of corneal surgeries. We have characterised a complex system of elastic fibers in the posterior cornea. These exist as sheets in the limbus that fenestrate and become fibers in the cornea. We believe these fibers provide the elastic restoring force in the peripheral tissue. This system should help explain some surgical properties of the cornea.
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Affiliation(s)
- Philip N Lewis
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - Tomas L White
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - Robert D Young
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - James S Bell
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| | - C Peter Winlove
- Department of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Keith M Meek
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK.
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12
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Mansfield JC, Bell JS, Winlove CP. The micromechanics of the superficial zone of articular cartilage. Osteoarthritis Cartilage 2015; 23:1806-16. [PMID: 26050867 DOI: 10.1016/j.joca.2015.05.030] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 05/18/2015] [Accepted: 05/26/2015] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To investigate the relationships between the unique mechanical and structural properties of the superficial zone of articular cartilage on the microscopic scale. DESIGN Fresh unstained equine metacarpophalangeal cartilage samples were mounted on tensile and compressive loading rigs on the stage of a multiphoton microscope. Sequential image stacks were acquired under incremental loads together with simultaneous measurements of the applied stress and strain. Second harmonic generation was used to visualise the collagen fibre network, while two photon fluorescence was used to visualise elastin fibres and cells. The changes visualised by each modality were tracked between successive loads. RESULTS The deformation of the cartilage matrix was heterogeneous on the microscopic length scale. This was evident from local strain maps, which showed shearing between different regions of collagen under tensile strain, corrugations in the articular surface at higher tensile strains and a non-uniform distribution of compressive strain in the axial direction. Chondrocytes elongated and rotated under tensile strain and were compressed in the axial direction under compressive load. The magnitude of deformation varied between cells, indicating differences in either load transmission through the matrix or the mechanical properties of individual cells. Under tensile loading the reorganisation of the elastin network differed from a homogeneous elastic response, indicating that it forms a functional structure. CONCLUSIONS This study highlights the complexity of superficial zone mechanics and demonstrates that the response of the collagen matrix, elastin fibres and chondrocytes are all heterogeneous on the microscopic scale.
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Affiliation(s)
- J C Mansfield
- College of Engineering Mathematics and Physical Sciences, University of Exeter, UK.
| | - J S Bell
- College of Engineering Mathematics and Physical Sciences, University of Exeter, UK
| | - C P Winlove
- College of Engineering Mathematics and Physical Sciences, University of Exeter, UK
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13
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Matcher SJ. What can biophotonics tell us about the 3D microstructure of articular cartilage? Quant Imaging Med Surg 2015; 5:143-58. [PMID: 25694964 DOI: 10.3978/j.issn.2223-4292.2014.12.03] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 12/02/2014] [Indexed: 12/30/2022]
Abstract
Connective tissues such as articular cartilage have been the subject of study using novel optical techniques almost since the invention of polarized light microscopy (PLM). Early studies of polarized light micrographs were the main evidential basis for the establishment of quantitative models of articular cartilage collagen structure by Benninghoff and others. Even now, state of the art optical techniques including quantitative polarized light microscopy (qPLM), optical coherence tomography (OCT), polarization-sensitive optical coherence tomography (PS-OCT), second harmonic generation (SHG) microscopy, Fourier-transform infrared (FTIR) microscopy, Raman and optical hyperspectral reflectance and fluorescence imaging are providing new insights into articular cartilage structure from the nanoscale through to the mesoscale. New insights are promised by emerging modalities such as optical elastography. This short review highlights some key recent results from modern optical techniques.
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Affiliation(s)
- Stephen J Matcher
- 1 Department of Materials Science and Engineering, 2 INSIGNEO Institute for in-silico medicine, University of Sheffield, North Campus, Broad Lane, Sheffield, S3 7HQ, UK
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Green EM, Mansfield JC, Bell JS, Winlove CP. The structure and micromechanics of elastic tissue. Interface Focus 2014; 4:20130058. [PMID: 24748954 PMCID: PMC3982448 DOI: 10.1098/rsfs.2013.0058] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Elastin is a major component of tissues such as lung and blood vessels, and endows them with the long-range elasticity necessary for their physiological functions. Recent research has revealed the complexity of these elastin structures and drawn attention to the existence of extensive networks of fine elastin fibres in tissues such as articular cartilage and the intervertebral disc. Nonlinear microscopy, allowing the visualization of these structures in living tissues, is informing analysis of their mechanical properties. Elastic fibres are complex in composition and structure containing, in addition to elastin, an array of microfibrillar proteins, principally fibrillin. Raman microspectrometry and X-ray scattering have provided new insights into the mechanisms of elasticity of the individual component proteins at the molecular and fibrillar levels, but more remains to be done in understanding their mechanical interactions in composite matrices. Elastic tissue is one of the most stable components of the extracellular matrix, but impaired mechanical function is associated with ageing and diseases such as atherosclerosis and diabetes. Efforts to understand these associations through studying the effects of processes such as calcium and lipid binding and glycation on the mechanical properties of elastin preparations in vitro have produced a confusing picture, and further efforts are required to determine the molecular basis of such effects.
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Affiliation(s)
| | | | | | - C. Peter Winlove
- Department of Physics, College of Engineering Mathematics and Physical Science, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
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