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Batool S, Roth BJ, Xia Y. Depth-Dependent Strain Model (1D) for Anisotropic Fibrils in Articular Cartilage. MATERIALS (BASEL, SWITZERLAND) 2024; 17:238. [PMID: 38204091 PMCID: PMC10779946 DOI: 10.3390/ma17010238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 12/21/2023] [Accepted: 12/29/2023] [Indexed: 01/12/2024]
Abstract
The mechanical response of articular cartilage (AC) under compression is anisotropic and depth-dependent. AC is osmotically active, and its intrinsic osmotic swelling pressure is balanced by its collagen fibril network. This mechanism requires the collagen fibers to be under a state of tensile pre-strain. A simple mathematical model is used to explain the depth-dependent strain calculations observed in articular cartilage under 1D axial compression (perpendicular to the articular surface). The collagen fibers are under pre-strain, influenced by proteoglycan concentration (fixed charged density, FCD) and collagen stiffness against swelling stress. The stiffness is introduced in our model as an anisotropic modulus that varies with fibril orientation through tissue depth. The collagen fibers are stiffer to stretching parallel to their length than perpendicular to it; when combined with depth-varying FCD, the model successfully predicts how tissue strains decrease with depth during compression. In summary, this model highlights that the mechanical properties of cartilage depend not only on proteoglycan concentration but also on the intrinsic properties of the pre-strained collagen network. These properties are essential for the proper functioning of articular cartilage.
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Affiliation(s)
| | - Bradley J. Roth
- Department of Physics, Oakland University, Rochester, MI 48309, USA; (S.B.); (Y.X.)
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2
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Oftadeh R, Azadi M, Donovan M, Langer J, Liao IC, Ortiz C, Grodzinsky AJ, Luengo GS. Poroelastic behavior and water permeability of human skin at the nanoscale. PNAS NEXUS 2023; 2:pgad240. [PMID: 37614672 PMCID: PMC10443659 DOI: 10.1093/pnasnexus/pgad240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 07/11/2023] [Accepted: 07/17/2023] [Indexed: 08/25/2023]
Abstract
Topical skin care products and hydrating compositions (moisturizers or injectable fillers) have been used for years to improve the appearance of, for example facial wrinkles, or to increase "plumpness". Most of the studies have addressed these changes based on the overall mechanical changes associated with an increase in hydration state. However, little is known about the water mobility contribution to these changes as well as the consequences to the specific skin layers. This is important as the biophysical properties and the biochemical composition of normal stratum corneum, epithelium, and dermis vary tremendously from one another. Our current studies and results reported here have focused on a novel approach (dynamic atomic force microscopy-based nanoindentation) to quantify biophysical characteristics of individual layers of ex vivo human skin. We have discovered that our new methods are highly sensitive to the mechanical properties of individual skin layers, as well as their hydration properties. Furthermore, our methods can assess the ability of these individual layers to respond to both compressive and shear deformations. In addition, since human skin is mechanically loaded over a wide range of deformation rates (frequencies), we studied the biophysical properties of skin over a wide frequency range. The poroelasticity model used helps to quantify the hydraulic permeability of the skin layers, providing an innovative method to evaluate and interpret the impact of hydrating compositions on water mobility of these different skin layers.
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Affiliation(s)
- Ramin Oftadeh
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Mojtaba Azadi
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- School of Engineering, San Francisco State University, San Francisco, CA 94132, USA
| | - Mark Donovan
- L’OREAL Research and Innovation, Aulnay sous Bois, 93106, France
| | | | - I-Chien Liao
- L'OREAL Research and Innovation, Clark, NJ 07066, USA
| | - Christine Ortiz
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Alan J Grodzinsky
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Gustavo S Luengo
- L’OREAL Research and Innovation, Aulnay sous Bois, 93106, France
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Raju V, Koorata PK. Computational assessment on the impact of collagen fiber orientation in cartilages on healthy and arthritic knee kinetics/kinematics. Med Eng Phys 2023; 117:103997. [PMID: 37331751 DOI: 10.1016/j.medengphy.2023.103997] [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: 09/14/2022] [Revised: 05/15/2023] [Accepted: 05/17/2023] [Indexed: 06/20/2023]
Abstract
BACKGROUND The inhomogeneous distribution of collagen fiber in cartilage can substantially influence the knee kinematics. This becomes vital for understanding the mechanical response of soft tissues, and cartilage deterioration including osteoarthritis (OA). Though the conventional computational models consider geometrical heterogeneity along with fiber reinforcements in the cartilage model as material heterogeneity, the influence of fiber orientation on knee kinetics and kinematics is not fully explored. This work examines how the collagen fiber orientation in the cartilage affects the healthy (intact knee) and arthritic knee response over multiple gait activities like running and walking. METHODS A 3D finite element knee joint model is used to compute the articular cartilage response during the gait cycle. A fiber-reinforced porous hyper elastic (FRPHE) material is used to model the soft tissue. A split-line pattern is used to implement the fiber orientation in femoral and tibial cartilage. Four distinct intact cartilage models and three OA models are simulated to assess the impact of the orientation of collagen fibers in a depth wise direction. The cartilage models with fibers oriented in parallel, perpendicular, and inclined to the articular surface are investigated for multiple knee kinematics and kinetics. FINDINGS The comparison of models with fiber orientation parallel to articulating surface for walking and running gait has the highest elastic stress and fluid pressure compared with inclined and perpendicular fiber-oriented models. Also, the maximum contact pressure is observed to be higher in the case of intact models during the walking cycle than for OA models. In contrast, the maximum contact pressure is higher during running in OA models than in intact models. Additionally, parallel-oriented models produce higher maximum stresses and fluid pressure for walking and running gait than proximal-distal-oriented models. Interestingly, during the walking cycle, the maximum contact pressure with intact models is approximately three times higher than on OA models. In contrast, the OA models exhibit higher contact pressure during the running cycle. INTERPRETATION Overall, the study indicates that collagen orientation is crucial for tissue responsiveness. This investigation provides insights into the development of tailored implants.
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Affiliation(s)
- Vaishakh Raju
- Applied Solid Mechanics Laboratory, Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, 575025, India
| | - Poornesh Kumar Koorata
- Applied Solid Mechanics Laboratory, Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, 575025, India.
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Moo EK, Ebrahimi M, Hrynevich A, de Ruijter M, Castilho M, Malda J, Korhonen RK. Load-induced fluid pressurisation in hydrogel systems before and after reinforcement by melt-electrowritten fibrous meshes. J Mech Behav Biomed Mater 2023; 143:105941. [PMID: 37285774 DOI: 10.1016/j.jmbbm.2023.105941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/25/2023] [Accepted: 05/28/2023] [Indexed: 06/09/2023]
Abstract
Fluid pressure develops transiently within mechanically-loaded, cell-embedding hydrogels, but its magnitude depends on the intrinsic material properties of the hydrogel and cannot be easily altered. The recently developed melt-electrowriting (MEW) technique enables three-dimensional printing of structured fibrous mesh with small fibre diameter (20 μm). The MEW mesh with 20 μm fibre diameter can synergistically increase the instantaneous mechanical stiffness of soft hydrogels. However, the reinforcing mechanism of the MEW meshes is not well understood, and may involve load-induced fluid pressurisation. Here, we examined the reinforcing effect of MEW meshes in three hydrogels: gelatin methacryloyl (GelMA), agarose and alginate, and the role of load-induced fluid pressurisation in the MEW reinforcement. We tested the hydrogels with and without MEW mesh (i.e., hydrogel alone, and MEW-hydrogel composite) using micro-indentation and unconfined compression, and analysed the mechanical data using biphasic Hertz and mixture models. We found that the MEW mesh altered the tension-to-compression modulus ratio differently for hydrogels that are cross-linked differently, which led to a variable change to their load-induced fluid pressurisation. MEW meshes only enhanced the fluid pressurisation for GelMA, but not for agarose or alginate. We speculate that only covalently cross-linked hydrogels (GelMA) can effectively tense the MEW meshes, thereby enhancing the fluid pressure developed during compressive loading. In conclusion, load-induced fluid pressurisation in selected hydrogels was enhanced by MEW fibrous mesh, and may be controlled by MEW mesh of different designs in the future, thereby making fluid pressure a tunable cell growth stimulus for tissue engineering involving mechanical stimulation.
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Affiliation(s)
- Eng Kuan Moo
- Department of Technical Physics, University of Eastern Finland, Finland; Department of Mechanical and Aerospace Engineering, Carleton University, Canada; Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada.
| | | | - Andrei Hrynevich
- Department of Orthopaedics, University Medical Center Utrecht, the Netherlands.
| | - Mylène de Ruijter
- Department of Orthopaedics, University Medical Center Utrecht, the Netherlands.
| | - Miguel Castilho
- Department of Orthopaedics, University Medical Center Utrecht, the Netherlands; Department of Biomedical Engineering, Eindhoven University of Technology, the Netherlands.
| | - Jos Malda
- Department of Orthopaedics, University Medical Center Utrecht, the Netherlands; Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands.
| | - Rami K Korhonen
- Department of Technical Physics, University of Eastern Finland, Finland.
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5
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Kourouklis AP, Wahlsten A, Stracuzzi A, Martyts A, Paganella LG, Labouesse C, Al-Nuaimi D, Giampietro C, Ehret AE, Tibbitt MW, Mazza E. Control of hydrostatic pressure and osmotic stress in 3D cell culture for mechanobiological studies. BIOMATERIALS ADVANCES 2023; 145:213241. [PMID: 36529095 DOI: 10.1016/j.bioadv.2022.213241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 10/25/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022]
Abstract
Hydrostatic pressure (HP) and osmotic stress (OS) play an important role in various biological processes, such as cell proliferation and differentiation. In contrast to canonical mechanical signals transmitted through the anchoring points of the cells with the extracellular matrix, the physical and molecular mechanisms that transduce HP and OS into cellular functions remain elusive. Three-dimensional cell cultures show great promise to replicate physiologically relevant signals in well-defined host bioreactors with the goal of shedding light on hidden aspects of the mechanobiology of HP and OS. This review starts by introducing prevalent mechanisms for the generation of HP and OS signals in biological tissues that are subject to pathophysiological mechanical loading. We then revisit various mechanisms in the mechanotransduction of HP and OS, and describe the current state of the art in bioreactors and biomaterials for the control of the corresponding physical signals.
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Affiliation(s)
- Andreas P Kourouklis
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland.
| | - Adam Wahlsten
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland
| | - Alberto Stracuzzi
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland; Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Anastasiya Martyts
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland
| | - Lorenza Garau Paganella
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland; Macromolecular Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland
| | - Celine Labouesse
- Macromolecular Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland
| | - Dunja Al-Nuaimi
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland
| | - Costanza Giampietro
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland; Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Alexander E Ehret
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland; Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Mark W Tibbitt
- Macromolecular Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland
| | - Edoardo Mazza
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Leonhardstrasse 21, 8092 Zurich, Switzerland; Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
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Ateshian GA, Petersen CA, Maas SA, Weiss JA. A Numerical Scheme for Anisotropic Reactive Nonlinear Viscoelasticity. J Biomech Eng 2023; 145:011004. [PMID: 35838330 PMCID: PMC9445319 DOI: 10.1115/1.4054983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 07/07/2022] [Indexed: 11/08/2022]
Abstract
Reactive viscoelasticity is a theoretical framework based on the theory of reactive constrained mixtures that encompasses nonlinear viscoelastic responses. It models a viscoelastic solid as a mixture of strong and weak bonds that maintain the cohesiveness of the molecular constituents of the solid matter. Strong bonds impart the elastic response while weak bonds break and reform into a stress-free state in response to loading. The process of bonds breaking and reforming is modeled as a reaction where loaded bonds are the reactants and bonds reformed into a stress-free state are the products of a reaction. The reaction is triggered by the evolving state of loading. The state of stress in strong bonds is a function of the total strain in the material, whereas the state of stress in weak bonds is based on the state of strain relative to the time that these bonds were reformed. This study introduces two important practical contributions to the reactive nonlinear viscoelasticity framework: (1) normally, the evaluation of the stress tensor involves taking a summation over a continually increasing number of weak bond generations, which is poorly suited for a computational scheme. Therefore, this study presents an effective numerical scheme for evaluating the strain energy density, the Cauchy stress, and spatial elasticity tensors of reactive viscoelastic materials. (2) We provide the conditions for satisfying frame indifference for anisotropic nonlinear viscoelasticity, including for tension-bearing fiber models. Code verifications and model validations against experimental data provide evidence in support of this updated formulation.
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Affiliation(s)
- Gerard A Ateshian
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Courtney A Petersen
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Steve A Maas
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112
| | - Jeffrey A Weiss
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112
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Tan WS, Moore AC, Stevens MM. Minimum design requirements for a poroelastic mimic of articular cartilage. J Mech Behav Biomed Mater 2023; 137:105528. [PMID: 36343521 PMCID: PMC7615484 DOI: 10.1016/j.jmbbm.2022.105528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 10/04/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022]
Abstract
The exceptional functional performance of articular cartilage (load-bearing and lubrication) is attributed to its poroelastic structure and resulting interstitial fluid pressure. Despite this, there remains no engineered cartilage repair material capable of achieving physiologically relevant poroelasticity. In this work we develop in silico models to guide the design approach for poroelastic mimics of articular cartilage. We implement the constitutive models in FEBio, a PDE solver for multiphasic mechanics problems in biological and soft materials. We investigate the influence of strain rate, boundary conditions at the contact interface, and fiber modulus on the reaction force and load sharing between the solid and fluid phases. The results agree with the existing literature that when fibers are incorporated the fraction of load supported by fluid pressure is greatly amplified and increases with the fiber modulus. This result demonstrates that a stiff fibrous phase is a primary design requirement for poroelastic mimics of articular cartilage. The poroelastic model is fit to experimental stress-relaxation data from bovine and porcine cartilage to determine if sufficient design constraints have been identified. In addition, we fit experimental data from FiHy™, an engineered material which is claimed to be poroelastic. The fiber-reinforced poroelastic model was able to capture the primary physics of these materials and demonstrates that FiHy™ is beginning to approach a cartilage-like poroelastic response. We also develop a fiber-reinforced poroelastic model with a bonded interface (rigid contact) to fit stress relaxation data from an osteochondral explant and FiHy™ + bone substitute. The model fit quality is similar for both the chondral and osteochondral configurations and clearly captures the first order physics. Based on this, we propose that physiological poroelastic mimics of articular cartilage should be developed under a fiber-reinforced poroelastic framework.
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Affiliation(s)
- Wei S Tan
- Department of Materials, Department of Bioengineering and Institute of Biomedical Engineering, Imperial College London, London, UK
| | - Axel C Moore
- Department of Materials, Department of Bioengineering and Institute of Biomedical Engineering, Imperial College London, London, UK; Department of Biomedical Engineering, University of Delaware, Newark, DE, USA.
| | - Molly M Stevens
- Department of Materials, Department of Bioengineering and Institute of Biomedical Engineering, Imperial College London, London, UK.
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8
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Moo EK, Ebrahimi M, Sibole SC, Tanska P, Korhonen RK. The intrinsic quality of proteoglycans, but not collagen fibres, degrades in osteoarthritic cartilage. Acta Biomater 2022; 153:178-189. [PMID: 36113721 DOI: 10.1016/j.actbio.2022.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 11/01/2022]
Abstract
The function of articular cartilage as a load-bearing connective tissue is derived primarily from a balanced interaction between the swelling proteoglycan (PG) matrix and tension-resistant collagen fibrous network. Such balance is compromised during joint disease such as osteoarthritis (OA) due to degradation to PGs and/or collagens. While the PG degradation is generally thought to be related to a loss of protein abundance, the collagenous degradation is more complex as it can be caused independently by a decrease of collagen content, disorganisation of fibrous structure and softening of individual collagen fibrils. A comprehensive understanding of the initial trajectories of degradation of PGs and collagen network can improve our chance of finding potential therapeutic solutions for OA. Here, we developed geometrically, structurally, and compositionally realistic and sample-specific Finite Element (FE) models under the framework of multiphasic mixture theory, from which the elastic moduli of collagen fibres and the PG load-bearing quality in healthy and diseased cartilages were estimated by numerical optimisation of the multi-step indentation stress relaxation force-time curves. We found the intrinsic quality of collagen fibres, measured by their elastic moduli, to stay constant for healthy and diseased cartilages. Combining with previous findings which show unaltered collagen content during early stages of OA, our results suggest the disorganisation of collagen fibrous network as the first form of collagenous degradation in osteoarthritic cartilage. We also found that PG degradation involves not only a loss of protein abundance, but also the quality of the remaining PGs in generating sufficient osmotic pressure for load bearing. This study sheds light on the mechanism of OA pathogenesis and highlights the restoration of collageneous organisation in cartilage as key medical intervention for OA. STATEMENT OF SIGNIFICANCE: Collagen network in articular cartilage consists of individual fibres that are organised into depth-dependent structure specialised for joint load-bearing and lubrication. During osteoarthritis, the collagen network undergoes mechanical degradation, but it is unclear if a loss of content, disorganisation of fibrous structure, or softening of individual fibres causes this degeneration. Using mechanical indentation, Finite Element modelling, and numerical optimisation methods, we determined that individual fibres did not soften in early disease stage. Together with previous findings showing unaltered collagen content, our results pinpoint the disorganisation of collagen structure as the main culprit for early collagenous degradation in osteoarthritic cartilage. Thus, early restoration in cartilage of collagen organisation, instead of individual fibre quality, may be key to slow osteoarthritis development.
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Affiliation(s)
- Eng Kuan Moo
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland; Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta 2N1N4, Canada.
| | | | - Scott C Sibole
- Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta 2N1N4, Canada
| | - Petri Tanska
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland.
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Moo EK, Al-Saffar Y, Le T, A Seerattan R, Pingguan-Murphy B, K Korhonen R, Herzog W. Deformation behaviors and mechanical impairments of tissue cracks in immature and mature cartilages. J Orthop Res 2022; 40:2103-2112. [PMID: 34914129 DOI: 10.1002/jor.25243] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 11/12/2021] [Accepted: 12/11/2021] [Indexed: 02/04/2023]
Abstract
Degeneration of articular cartilage is often triggered by a small tissue crack. As cartilage structure and composition change with age, the mechanics of cracked cartilage may depend on the tissue age, but this relationship is poorly understood. Here, we investigated cartilage mechanics and crack deformation in immature and mature cartilage exposed to a full-thickness tissue crack using indentation testing and histology, respectively. When a cut was introduced, tissue cracks opened wider in the mature cartilage compared to the immature cartilage. However, the opposite occurred upon mechanical indentation over the cracked region. Functionally, the immature-cracked cartilages stress-relaxed faster, experienced increased tissue strain, and had reduced instantaneous stiffness, compared to the mature-cracked cartilages. Taken together, mature cartilage appears to withstand surface cracks and maintains its mechanical properties better than immature cartilage and these superior properties can be explained by the structure of their collagen fibrous network.
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Affiliation(s)
- Eng Kuan Moo
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Yasir Al-Saffar
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Tina Le
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Ruth A Seerattan
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | | | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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Krull CM, Rife J, Klamer B, Purmessur D, Walter BA. Pericellular heparan sulfate proteoglycans: Role in regulating the biosynthetic response of nucleus pulposus cells to osmotic loading. JOR Spine 2022; 5:e1209. [PMID: 35783912 PMCID: PMC9238280 DOI: 10.1002/jsp2.1209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 04/26/2022] [Accepted: 05/12/2022] [Indexed: 12/04/2022] Open
Abstract
Background Daily physiologic loading causes fluctuations in hydration of the intervertebral disc (IVD); thus, the embedded cells experience cyclic alterations to their osmotic environment. These osmotic fluctuations have been described as a mechanism linking mechanics and biology, and have previously been shown to promote biosynthesis in chondrocytes. However, this phenomenon has yet to be fully interrogated in the IVD. Additionally, the specialized extracellular matrix surrounding the cells, the pericellular matrix (PCM), transduces the biophysical signals that cells ultimately experience. While it is known that the PCM is altered in disc degeneration, whether it disrupts normal osmotic mechanotransduction has yet to be determined. Thus, our objectives were to assess: (1) whether dynamic osmotic conditions stimulate biosynthesis in nucleus pulposus cells, and (2) whether pericellular heparan sulfate proteoglycans (HSPGs) modulate the biosynthetic response to osmotic loading. Methods Bovine nucleus pulposus cells isolated with retained PCM were encapsulated in 1.5% alginate beads and treated with or without heparinase III, an enzyme that degrades the pericellular HSPGs. Beads were subjected to 1 h of daily iso-osmotic, hyper-osmotic, or hypo-osmotic loading for 1, 2, or 4 weeks. At each timepoint the total amount of extracellular and pericellular sGAG/DNA were quantified. Additionally, whether osmotic loading triggered alterations to HSPG sulfation was assessed via immunohistochemistry for the heparan sulfate 6-O-sulfertransferase 1 (HS6ST1) enzyme. Results Osmotic loading significantly influenced sGAG/DNA accumulation with a hyper-osmotic change promoting the greatest sGAG/DNA accumulation in the pericellular region compared with iso-osmotic conditions. Heparanase-III treatment significantly reduced extracellular sGAG/DNA but pericellular sGAG was not affected. HS6ST1 expression was not affected by osmotic loading. Conclusion Results suggest that hyper-osmotic loading promotes matrix synthesis and that modifications to HSPGs directly influence the metabolic responses of cells to osmotic fluctuations. Collectively, results suggest degeneration-associated modifications to pericellular HSPGs may contribute to the altered mechanobiology observed in disease.
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Affiliation(s)
- Carly M. Krull
- Department of Biomedical EngineeringThe Ohio State UniversityColumbusOhioUSA
| | - Jordan Rife
- Department of Biomedical EngineeringThe Ohio State UniversityColumbusOhioUSA
| | - Brett Klamer
- Department of Biomedical Informatics, Center for BiostatisticsThe Ohio State UniversityColumbusOhioUSA
| | - Devina Purmessur
- Department of Biomedical EngineeringThe Ohio State UniversityColumbusOhioUSA
- Department of OrthopedicsThe Ohio State University Wexner Medical CenterColumbusOhioUSA
- Spine Research InstituteThe Ohio State UniversityColumbusOhioUSA
| | - Benjamin A. Walter
- Department of Biomedical EngineeringThe Ohio State UniversityColumbusOhioUSA
- Department of OrthopedicsThe Ohio State University Wexner Medical CenterColumbusOhioUSA
- Spine Research InstituteThe Ohio State UniversityColumbusOhioUSA
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11
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Orozco GA, Tanska P, Gustafsson A, Korhonen RK, Isaksson H. Crack propagation in articular cartilage under cyclic loading using cohesive finite element modeling. J Mech Behav Biomed Mater 2022; 131:105227. [DOI: 10.1016/j.jmbbm.2022.105227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 03/01/2022] [Accepted: 04/02/2022] [Indexed: 11/28/2022]
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Zimmerman BK, Maas SA, Weiss JA, Ateshian GA. A Finite Element Algorithm for Large Deformation Biphasic Frictional Contact Between Porous-Permeable Hydrated Soft Tissues. J Biomech Eng 2022; 144:1115780. [PMID: 34382640 PMCID: PMC8547016 DOI: 10.1115/1.4052114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Indexed: 02/03/2023]
Abstract
The frictional response of porous and permeable hydrated biological tissues such as articular cartilage is significantly dependent on interstitial fluid pressurization. To model this response, it is common to represent such tissues as biphasic materials, consisting of a binary mixture of a porous solid matrix and an interstitial fluid. However, no computational algorithms currently exist in either commercial or open-source software that can model frictional contact between such materials. Therefore, this study formulates and implements a finite element algorithm for large deformation biphasic frictional contact in the open-source finite element software FEBio. This algorithm relies on a local form of a biphasic friction model that has been previously validated against experiments, and implements the model into our recently-developed surface-to-surface (STS) contact algorithm. Contact constraints, including those specific to pressurized porous media, are enforced with the penalty method regularized with an active-passive augmented Lagrangian scheme. Numerical difficulties specific to challenging finite deformation biphasic contact problems are overcome with novel smoothing schemes for fluid pressures and Lagrange multipliers. Implementation accuracy is verified against semi-analytical solutions for biphasic frictional contact, with extensive validation performed using canonical cartilage friction experiments from prior literature. Essential details of the formulation are provided in this paper, and the source code of this biphasic frictional contact algorithm is made available to the general public.
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Affiliation(s)
| | - Steve A. Maas
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112
| | - Jeffrey A. Weiss
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84112
| | - Gerard A. Ateshian
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
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13
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Hwang JW, Chawla D, Han G, Eriten M, Henak CR. Effects of solvent osmolarity and viscosity on cartilage energy dissipation under high-frequency loading. J Mech Behav Biomed Mater 2021; 126:105014. [PMID: 34871958 DOI: 10.1016/j.jmbbm.2021.105014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/29/2021] [Accepted: 11/27/2021] [Indexed: 01/16/2023]
Abstract
Articular cartilage is a spatially heterogeneous, dissipative biological hydrogel with a high fluid volume fraction. Although energy dissipation is important in the context of delaying cartilage damage, the dynamic behavior of articular cartilage equilibrated in media of varied osmolarity and viscosity is not widely understood. This study investigated the mechanical behaviors of cartilage when equilibrated to media of varying osmolarity and viscosity. Dynamic moduli and phase shift were measured at both low (1 Hz) and high (75-300 Hz) frequency, with cartilage samples compressed to varied offset strain levels. Increasing solution osmolarity and viscosity both independently resulted in larger energy dissipation and decreased dynamic modulus of cartilage at both low and high frequency. Mechanical property alterations induced by varying osmolarity are likely due to the change in permeability and fluid volume fraction within the tissue. The effects of solution viscosity are likely due to frictional interactions at the solid-fluid interface, affecting energy dissipation. These findings highlight the significance of interstitial fluid on the energy dissipation capabilities of the tissue, which can influence the onset of cartilage damage.
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Affiliation(s)
- Jin Wook Hwang
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Dipul Chawla
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Guebum Han
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Melih Eriten
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Corinne R Henak
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, WI, USA.
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14
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Gacek E, Bermel EA, Ellingson AM, Barocas VH. Through-thickness regional variation in the mechanical characteristics of the lumbar facet capsular ligament. Biomech Model Mechanobiol 2021; 20:1445-1457. [PMID: 33788068 PMCID: PMC9289988 DOI: 10.1007/s10237-021-01455-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 03/25/2021] [Indexed: 10/21/2022]
Abstract
The human lumbar facet capsule, with the facet capsular ligament (FCL) that forms its primary constituent, is a common source of lower back pain. Prior studies on the FCL were limited to in-plane tissue behavior, but due to the presence of two distinct yet mechanically different regions, a novel out-of-plane study was conducted to further characterize the roles of the collagen and elastin regions. An experimental technique, called stretch-and-bend, was developed to study the tension-compression asymmetry of the FCL due to varying collagen fiber density throughout the thickness of the tissue. Each healthy excised cadaveric FCL sample was tested in four conditions depending on primary collagen fiber alignment and regional loading. Our results indicate that the FCL is stiffest when the collagen fibers (1) are aligned in the direction of loading, (2) are in tension, and (3) are stretched - 16% from its off-the-bone, undeformed state. An optimization routine was used to fit a four-parameter anisotropic, hyperplastic model to the experimental data. The average elastin modulus, E, and the average collagen fiber modulus, ξ, were 13.15 ± 3.59 kPa and 18.68 ± 13.71 MPa (95% CI), respectively.
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Affiliation(s)
- Elizabeth Gacek
- Biomedical Engineering, University of Minnesota, 312 Church St. SE, 7-105 Nils Hasselmo Hall, Minneapolis, MN, 55455, USA
| | - Emily A Bermel
- Biomedical Engineering, University of Minnesota, 312 Church St. SE, 7-105 Nils Hasselmo Hall, Minneapolis, MN, 55455, USA
| | - Arin M Ellingson
- Divisions of Physical Therapy and Rehabilitation Science, Departments of Rehabilitation Medicine and Orthopedic Surgery, University of Minnesota, 426 Church St. SE, 366A Children's Rehab Ctr, Minneapolis, MN, 55455, USA
| | - Victor H Barocas
- Biomedical Engineering, University of Minnesota, 312 Church St. SE, 7-105 Nils Hasselmo Hall, Minneapolis, MN, 55455, USA.
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15
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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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16
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Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study. Bioengineering (Basel) 2021; 8:bioengineering8050070. [PMID: 34065530 PMCID: PMC8160968 DOI: 10.3390/bioengineering8050070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/03/2021] [Accepted: 05/17/2021] [Indexed: 11/17/2022] Open
Abstract
The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress-relaxation tests comprised of increasing strains followed by stress-relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.
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17
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Moo EK, Tanska P, Federico S, Al-Saffar Y, Herzog W, Korhonen RK. Collagen fibres determine the crack morphology in articular cartilage. Acta Biomater 2021; 126:301-314. [PMID: 33757903 DOI: 10.1016/j.actbio.2021.03.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 12/27/2022]
Abstract
Cracks in articular cartilage compromise tissue integrity and mechanical properties and lead to chondral lesions if untreated. An understanding of the mechanics of cracked cartilage may help in the prevention of cartilage deterioration and the development of tissue-engineered substitutes. The degeneration of cartilage in the presence of cracks may depend on the ultrastructure and composition of the tissue, which changes with aging, disease and habitual loading. It is unknown if the structural and compositional differences between immature and mature cartilage affect the mechanics of cartilage cracks, possibly predisposing one to a greater risk of degeneration than the other. We used a fibre-reinforced poro-viscoelastic swelling material model that accounts for large deformations and tension-compression non-linearity, and the finite element method to investigate the role of cartilage structure and composition on crack morphology and tissue mechanics. We demonstrate that the crack morphology predicted by our theoretical model agrees well with the histo-morphometric images of young and mature cracked cartilages under indentation loading. We also determined that the crack morphology was primarily dependent on collagen fibre orientation which differs as a function of cartilage depth and tissue maturity. The arcade-like collagen fibre orientation, first discussed by Benninghoff in his classical 1925 paper, appears to be beneficial for slowing the progression of tissue cracks by 'sealing' the crack and partially preserving fluid pressure during loading. Preservation of the natural load distribution between solid and fluid constituents of cartilage may be a key factor in slowing or preventing the propagation of tissue cracks and associated tissue matrix damage. STATEMENT OF SIGNIFICANCE: Cracks in articular cartilage can be detrimental to joint health if not treated, but it is not clear how they propagate and lead to tissue degradation. We used an advanced numerical model to determine the role of cartilage structure and composition on crack morphology under loading. Based on the structure and composition found in immature and mature cartilages, our model successfully predicts the crack morphology in these cartilages and determines that collagen fibre as the major determinant of crack morphology. The arcade-like Benninghoff collagen fibre orientation appears to be crucial in 'sealing' the tissue crack and preserves normal fluid-solid load distribution in cartilage. Inclusion of the arcade-like fibre orientation in tissue-engineered construct may help improve its integration within the host tissue.
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Affiliation(s)
- Eng Kuan Moo
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland; Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4, Canada.
| | - Petri Tanska
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland.
| | - Salvatore Federico
- Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4 Canada; Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4, Canada.
| | - Yasir Al-Saffar
- Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4, Canada
| | - Walter Herzog
- Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4, Canada; Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4 Canada; Biomechanics Laboratory, School of Sports, Federal University of Santa Catarina, Florianopolis, SC, Brazil.
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland.
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18
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Zimmerman BK, Nims RJ, Chen A, Hung CT, Ateshian GA. Direct Osmotic Pressure Measurements in Articular Cartilage Demonstrate Nonideal and Concentration-Dependent Phenomena. J Biomech Eng 2021; 143:041007. [PMID: 33210125 PMCID: PMC7872001 DOI: 10.1115/1.4049158] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 11/01/2020] [Indexed: 11/08/2022]
Abstract
The osmotic pressure in articular cartilage serves an important mechanical function in healthy tissue. Its magnitude is thought to play a role in advancing osteoarthritis. The aims of this study were to: (1) isolate and quantify the magnitude of cartilage swelling pressure in situ; and (2) identify the effect of salt concentration on material parameters. Confined compression stress-relaxation testing was performed on 18 immature bovine and six mature human cartilage samples in solutions of varying osmolarities. Direct measurements of osmotic pressure revealed nonideal and concentration-dependent osmotic behavior, with magnitudes approximately 1/3 those predicted by ideal Donnan law. A modified Donnan constitutive behavior was able to capture the aggregate behavior of all samples with a single adjustable parameter. Results of curve-fitting transient stress-relaxation data with triphasic theory in febio demonstrated concentration-dependent material properties. The aggregate modulus HA increased threefold as the external concentration decreased from hypertonic 2 M to hypotonic 0.001 M NaCl (bovine: HA=0.420±0.109 MPa to 1.266±0.438 MPa; human: HA=0.499±0.208 MPa to 1.597±0.455 MPa), within a triphasic theory inclusive of osmotic effects. This study provides a novel and simple analytical model for cartilage osmotic pressure which may be used in computational simulations, validated with direct in situ measurements. A key finding is the simultaneous existence of Donnan osmotic and Poisson-Boltzmann electrostatic interactions within cartilage.
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Affiliation(s)
- Brandon K Zimmerman
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Robert J Nims
- Department of Biomedical Engineering, Columbia University, New York, NY 10027
| | - Alex Chen
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Clark T Hung
- Department of Biomedical Engineering, Columbia University, New York, NY 10027
| | - Gerard A Ateshian
- Department of Mechanical Engineering, Columbia University, New York, NY 10027; Department of Biomedical Engineering, Columbia University, New York, NY 10027
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19
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Human articular cartilage is orthotropic where microstructure, micromechanics, and chemistry vary with depth and split-line orientation. Osteoarthritis Cartilage 2020; 28:1362-1372. [PMID: 32645403 PMCID: PMC7697147 DOI: 10.1016/j.joca.2020.06.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/25/2020] [Accepted: 06/27/2020] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Quantitative, micrometer length scale assessment of human articular cartilage is essential to enable progress toward new functional tissue engineering approaches, including utilization of emerging 3D bioprinting technologies, and for improved computational modeling of the osteochondral unit. Thus the objective of this study was to characterize the structural organization, material properties, and chemical composition of human skeletally mature articular cartilage with respect to depth and defined morphological features: normal to the articulating surface, parallel to the split-line, and transverse to the split-line. METHOD Three samples from the lateral femoral condyles of 4 healthy adult donors (55-61 years old) were evaluated via histology, second harmonic generation, microindentation, and Raman spectroscopy. All metrics were evaluated as a function of depth and direction relative to the split-line. RESULTS All donors presented with intact and healthy tissue. Collagen fiber orientation varied significantly between testing directions and with increasing depth from the articular surface. Both compressive and tensile modulus increased significantly with depth and differed across the middle and deep zones and depended on orthogonal direction relative to the split-line. Similarly, matrix components varied with both depth and direction, where chondroitin sulfate steadily increased with depth while collagen prevalence was highest in the surface layer. CONCLUSIONS Microscale measurements of human articular cartilage demonstrate that properties are both depth-dependent and orthotropic and depend on the underlying tissue structure and composition. These findings improve upon existing knowledge establishing more accurate measurements, with greater degree of depth and spatial specificity, as inputs for tissue engineering and computational modeling.
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20
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Transient stiffening of cartilage during joint articulation: A microindentation study. J Mech Behav Biomed Mater 2020; 113:104113. [PMID: 33032010 DOI: 10.1016/j.jmbbm.2020.104113] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 08/23/2020] [Accepted: 09/24/2020] [Indexed: 11/21/2022]
Abstract
As a mechanoactive tissue, articular cartilage undergoes compression and shear on a daily basis. With the advent of high resolution and sensitive mechanical testing methods, such as micro- and nanoindentation, it has become possible to assess changes in small-scale mechanical properties due to compression and shear of the tissue. However, investigations on the changes of these properties before and after joint articulation have been limited. To simulate articular loading of cartilage in the context of human gait, a previously developed bioreactor system was used. Immediately after bioreactor testing, the stiffness was measured using microindentation. Specifically, we investigated whether the mechanical response of the tissue was transient or permanent, dependent on counterface material, and an effect limited to the superficial zone of cartilage. We found that cartilage surface stiffness increases immediately after articular loading and returns to baseline values within 3 hr. Cartilage-on-cartilage stiffening was found to be higher compared to both alumina- and cobalt chromium-on-cartilage stiffening, which were not significantly different from each other. This stiffening response was found to be unique to the superficial zone, as articular loading on cartilage with the superficial zone removed showed no changes in stiffness. The findings of this study suggest that the cartilage superficial zone may adapt its stiffness as a response to articular loading. As the superficial zone is often compromised during the course of osteoarthritic disease, this finding is of clinical relevance, suggesting that the load-bearing function deteriorates over time.
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21
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Motavalli M, Jones C, Berilla JA, Li M, Schluchter MD, Mansour JM, Welter JF. Apparatus and Method for Rapid Detection of Acoustic Anisotropy in Cartilage. J Med Biol Eng 2020; 40:419-427. [PMID: 32494235 DOI: 10.1007/s40846-020-00518-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Purpose Articular cartilage is known to be mechanically anisotropic. In this paper, the acoustic anisotropy of bovine articular cartilage and the effects of freeze-thaw cycling on acoustic anisotropy were investigated. Methods We developed apparatus and methods that use a magnetic L-shaped sample holder, which allowed minimal handling of a tissue, reduced the number of measurements compared to previous studies, and produced highly reproducible results. Results SOS was greater in the direction perpendicular to the articular surface compared to the direction parallel to the articular surface (N=17, P = 0.00001). Average SOS was 1,758 ± 107 m/s perpendicular to the surface, and 1,617 ± 55 m/s parallel to it. The average percentage difference in SOS between the perpendicular and parallel directions was 8.2% (95% CI: 5.4% to 11%). Freeze-thaw cycling did not have a significant effect on SOS (P>0.4). Conclusion Acoustic measurement of tissue properties is particularly attractive for work in our laboratory since it has the potential for nondestructive characterization of the properties of developing engineered cartilage. Our approach allowed us to observe acoustic anisotropy of articular cartilage rapidly and reproducibly. This property was not significantly affected by freeze-thawing of the tissue samples, making cryopreservation practical for these assays.
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Affiliation(s)
- Mostafa Motavalli
- Department of Biology, Case Western Reserve University, all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
| | | | - Jim A Berilla
- Department of Civil Engineering, Case Western Reserve University, all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
| | - Ming Li
- Department of Population and Quantitative Health Sciences, Case Western Reserve University, all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
| | - Mark D Schluchter
- Department of Population and Quantitative Health Sciences, Case Western Reserve University, all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
| | - Joseph M Mansour
- Department of Mechanical and Aerospace Engineering, Case Western Reserve University all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
| | - Jean F Welter
- Department of Biology, Case Western Reserve University, all Cleveland, OH, USA.,Case Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, all Cleveland, OH, USA
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22
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Kotelsky A, Carrier JS, Aggouras A, Richards MS, Buckley MR. Evidence that reduction in volume protects in situ articular chondrocytes from mechanical impact. Connect Tissue Res 2020; 61:360-374. [PMID: 31937149 DOI: 10.1080/03008207.2020.1711746] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chondrocytes, the resident cells in articular cartilage, carry the burden of producing and maintaining the extracellular matrix (ECM). However, as these cells have a low proliferative capacity and are not readily replaced, chondrocyte death due to extreme forces may contribute to the pathogenesis of osteoarthritis (OA) after injury or may inhibit healing after osteochondral transplantation, a restorative procedure for damaged cartilage that requires a series of mechanical impacts to insert the graft. Consequently, there is a need to understand what factors influence the vulnerability of in situ chondrocytes to mechanical trauma. To this end, the objective of this study was to investigate how altering cell volume by different means (hydrostatic pressure, uniaxial load, and osmotic challenge with and without inhibition of regulatory volume decrease) affects the vulnerability of in situ chondrocytes to extreme mechanical forces. Using a custom experimental platform enabling testing of viable and intact murine cartilage-on-bone explants, we established a strong correlation between chondrocyte volume and vulnerability to impact injury wherein reduced volume was protective. Moreover, we found that the volume-perturbing interventions did not affect cartilage ECM mechanical properties, suggesting that their effects on chondrocyte vulnerability occurred at the cellular level. The findings of this study offer new avenues for novel strategies aimed at preventing chondrocyte loss during osteochondral grafting or to halting the progression of cell death after a joint destabilizing injury.
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Affiliation(s)
- Alexander Kotelsky
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA
| | - Joseph S Carrier
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA
| | - Anthony Aggouras
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY, USA
| | - Michael S Richards
- Department of Biomedical Engineering, Rochester Institute of Technology, Rochester, NY, USA
| | - Mark R Buckley
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA
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23
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Experimental Study on Creep Characteristics of Microdefect Articular Cartilages in the Damaged Early Stage. JOURNAL OF HEALTHCARE ENGINEERING 2019; 2019:8526436. [PMID: 31827742 PMCID: PMC6885224 DOI: 10.1155/2019/8526436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 09/26/2019] [Accepted: 10/17/2019] [Indexed: 11/17/2022]
Abstract
Traumatic joint injury is known to cause cartilage deterioration and osteoarthritis. In order to study the mechanical mechanism of damage evolution on articular cartilage, taking the fresh porcine articular cartilage as the experimental samples, the creep experiments of the intact cartilages and the cartilages with different depth defect were carried out by using the noncontact digital image correlation technology. And then, the creep constitutive equations of cartilages were established. The results showed that the creep curves of different layers changed exponentially and were not coincident for the cartilage sample. The defect affected the strain values of the creep curves. The creep behavior of cartilage was dependent on defect depth. The deeper the defect was, the larger the strain value was. The built three-parameter viscoelastic constitutive equation had a good correlation with the experimental results and could predict the creep performance of the articular cartilage. The creep values of the microdefective cartilage in the damaged early stage were different from the diseased articular cartilage. These findings pointed out that defect could accelerate the damage of cartilage. It was helpful to study the mechanical mechanism of damage evolution.
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24
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Bergholt MS, Serio A, Albro MB. Raman Spectroscopy: Guiding Light for the Extracellular Matrix. Front Bioeng Biotechnol 2019; 7:303. [PMID: 31737621 PMCID: PMC6839578 DOI: 10.3389/fbioe.2019.00303] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 10/16/2019] [Indexed: 12/12/2022] Open
Abstract
The extracellular matrix (ECM) consists of a complex mesh of proteins, glycoproteins, and glycosaminoglycans, and is essential for maintaining the integrity and function of biological tissues. Imaging and biomolecular characterization of the ECM is critical for understanding disease onset and for the development of novel, disease-modifying therapeutics. Recently, there has been a growing interest in the use of Raman spectroscopy to characterize the ECM. Raman spectroscopy is a label-free vibrational technique that offers unique insights into the structure and composition of tissues and cells at the molecular level. This technique can be applied across a broad range of ECM imaging applications, which encompass in vitro, ex vivo, and in vivo analysis. State-of-the-art confocal Raman microscopy imaging now enables label-free assessments of the ECM structure and composition in tissue sections with a remarkably high degree of biomolecular specificity. Further, novel fiber-optic instrumentation has opened up for clinical in vivo ECM diagnostic measurements across a range of tissue systems. A palette of advanced computational methods based on multivariate statistics, spectral unmixing, and machine learning can be applied to Raman data, allowing for the extraction of specific biochemical information of the ECM. Here, we review Raman spectroscopy techniques for ECM characterizations over a variety of exciting applications and tissue systems, including native tissue assessments (bone, cartilage, cardiovascular), regenerative medicine quality assessments, and diagnostics of disease states. We further discuss the challenges in the widespread adoption of Raman spectroscopy in biomedicine. The results of the latest discovery-driven Raman studies are summarized, illustrating the current and potential future applications of Raman spectroscopy in biomedicine.
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Affiliation(s)
- Mads S. Bergholt
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
| | - Andrea Serio
- Centre for Craniofacial and Regenerative Biology, King's College London, London, United Kingdom
| | - Michael B. Albro
- Department of Mechanical Engineering, Boston University, Boston, MA, United States
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25
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Patel JM, Wise BC, Bonnevie ED, Mauck RL. A Systematic Review and Guide to Mechanical Testing for Articular Cartilage Tissue Engineering. Tissue Eng Part C Methods 2019; 25:593-608. [PMID: 31288616 DOI: 10.1089/ten.tec.2019.0116] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Articular cartilage is integral to the mechanical function of many joints in the body. When injured, cartilage lacks the capacity to self-heal, and thus, therapies and replacements have been developed in recent decades to treat damaged cartilage. Given that the primary function of articular cartilage is mechanical in nature, rigorous physical evaluation of cartilage tissues undergoing treatment and cartilage constructs intended for replacement is an absolute necessity. With the large number of groups developing cartilage tissue engineering strategies, however, a variety of mechanical testing protocols have been reported in the literature. This lack of consensus in testing methods makes comparison between studies difficult at times, and can lead to misinterpretation of data relative to native tissue. Therefore, the purpose of this study was to systematically review mechanical testing of articular cartilage and cartilage repair constructs over the past 10 years (January 2009-December 2018), to highlight the most common testing configurations, and to identify key testing parameters. For the most common tests, key parameters identified in this systematic review were validated by characterizing both cartilage tissue and hydrogels commonly used in cartilage tissue engineering. Our findings show that compression testing was the most common test performed (80.2%; 158/197), followed by evaluation of frictional properties (18.8%; 37/197). Upon further review of those studies performing compression testing, the various modes (ramp, stress relaxation, creep, dynamic) and testing configurations (unconfined, confined, in situ) are described and systematically reviewed for parameters, including strain rate, equilibrium time, and maximum strain. This systematic analysis revealed considerable variability in testing methods. Our validation testing studies showed that such variations in testing criteria could have large implications on reported outcome parameters (e.g., modulus) and the interpretation of findings from these studies. This analysis is carried out for all common testing methods, followed by a discussion of less common trends and directions in the mechanical evaluation of cartilage tissues and constructs. Overall, this work may serve as a guide for cartilage tissue engineers seeking to rigorously evaluate the physical properties of their novel treatment strategies. Impact Statement Articular cartilage tissue engineering has made significant strides with regard to treatments and replacements for injured tissue. The evaluation of these approaches typically involves mechanical testing, yet the plethora of testing techniques makes comparisons between studies difficult, and often leads to misinterpretation of data compared with native tissue. This study serves as a guide for the mechanical testing of cartilage tissues and constructs, highlighting recent trends in test conditions and validating these common procedures. Cartilage tissue engineers, especially those unfamiliar with mechanical testing protocols, will benefit from this study in their quest to physically evaluate novel treatment and regeneration approaches.
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Affiliation(s)
- Jay M Patel
- McKay Orthopedic Research Laboratory, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Translational Musculoskeletal Research Center, Corporal Michael J Crescenz VA Medical Center, Philadelphia, Pennsylvania
| | - Brian C Wise
- McKay Orthopedic Research Laboratory, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Edward D Bonnevie
- McKay Orthopedic Research Laboratory, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Translational Musculoskeletal Research Center, Corporal Michael J Crescenz VA Medical Center, Philadelphia, Pennsylvania
| | - Robert L Mauck
- McKay Orthopedic Research Laboratory, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.,Translational Musculoskeletal Research Center, Corporal Michael J Crescenz VA Medical Center, Philadelphia, Pennsylvania.,Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania
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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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Pan W, Roccabianca S, Basson MD, Bush TR. Influences of sodium and glycosaminoglycans on skin oedema and the potential for ulceration: a finite-element approach. ROYAL SOCIETY OPEN SCIENCE 2019; 6:182076. [PMID: 31417698 PMCID: PMC6689624 DOI: 10.1098/rsos.182076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 06/03/2019] [Indexed: 06/10/2023]
Abstract
Venous ulcers are chronic transcutaneous wounds common in the lower legs. They are resistant to healing and have a 78% chance of recurrence within 2 years. It is commonly accepted that venous ulcers are caused by the insufficiency of the calf muscle pump, leading to blood pooling in the lower legs, resulting in inflammation, skin oedema, tissue necrosis and eventually skin ulceration. However, the detailed physiological events by which inflammation contributes to wound formation are poorly understood. We therefore sought to develop a model that simulated the inflammation, using it to determine the internal stresses and pressure on the skin that contribute to venous ulcer formation. A three-layer finite-element skin model (epidermis, dermis and hypodermis) was developed to explore the roles in wound formation of two inflammation identifiers: glycosaminoglycans (GAG) and sodium. A series of parametric studies showed that increased GAG and sodium content led to oedema and increased tissue stresses of 1.5 MPa, which was within the reported range of skin tissue ultimate tensile stress (0.1-40 MPa). These results suggested that both the oedema and increased fluid pressure could reach a threshold for tissue damage and eventual ulcer formation. The models presented here provide insights to the pathological events associated with venous insufficiency, including inflammation, oedema and skin ulceration.
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Affiliation(s)
- Wu Pan
- Department of Mechanical Engineering, Michigan State University, 428 South Shaw Lane, Room 2555, East Lansing, MI 48824, USA
| | - Sara Roccabianca
- Department of Mechanical Engineering, Michigan State University, 428 South Shaw Lane, Room 2555, East Lansing, MI 48824, USA
| | - Marc D. Basson
- Department of Surgery at the University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Tamara Reid Bush
- Department of Mechanical Engineering, Michigan State University, 428 South Shaw Lane, Room 2555, East Lansing, MI 48824, USA
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Biological connective tissues exhibit viscoelastic and poroelastic behavior at different frequency regimes: Application to tendon and skin biophysics. Acta Biomater 2018; 70:249-259. [PMID: 29425716 DOI: 10.1016/j.actbio.2018.01.041] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 01/28/2018] [Accepted: 01/29/2018] [Indexed: 10/18/2022]
Abstract
In this study, a poroviscoelastic finite element model (FEM) was developed and used in conjunction with an AFM-based wide-bandwidth nanorheology system to predict the frequency-dependent mechanical behavior of tendon and dermis subjected to compression via nanoindentation. The aim was to distinguish between loading rates that are dominated by either poroelasticity, viscoelasticity, or the superposition of these processes. Using spherical probe tips having different radii, the force and tip displacement were measured and the magnitude, E∗, and phase angle, ϕ, of the dynamic complex modulus were evaluated for mouse supraspinatus tendon and mouse dermis. The peak frequencies of the phase angle were associated with the characteristic time constants of poroelastic and viscoelastic material behavior. The developed FE model could predict the separate poroelastic and viscoelastic responses of these soft tissues over a 4 decade frequency range, showing good agreement with experimental results. We observed that poroelasticity was the dominant energy dissipation mechanism for mouse dermis and supraspinatus tendon at higher indentation frequencies (102 to 104 Hz) whereas viscoelasticity was typically dominant at lower frequencies (<102 Hz). These findings show the underlying mechanical behavior of biological connective tissues and give insight into the role played by these different energy dissipation mechanisms in governing the function of these tissues at nanoscale. STATEMENT OF SIGNIFICANCE Soft biological tissues exhibit complex, load- and time-dependent mechanical behavior. Evaluating their mechanical behavior requires sophisticated experimental tools and numerical models that can capture the fundamental mechanisms governing tissue function. Using an Atomic-force-microscopy-based rheology system and finite element models, the roles of the two most dominant time-dependent mechanisms (poroelasticity and viscoelasticity) that govern the dynamic loading behavior of mouse skin and tendon have been investigated. FE models were able to predict and quantify the contribution of each mechanism to the overall dynamic response and confirming the presence of these two distinct mechanisms in the mechanical response. Overall, these results provide novel insight into the viscoelastic and poroelastic properties of mouse skin and tendon and promote better understanding of the underlying origins of each mechanism.
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Wahlquist JA, DelRio FW, Randolph MA, Aziz AH, Heveran CM, Bryant SJ, Neu CP, Ferguson VL. Indentation mapping revealed poroelastic, but not viscoelastic, properties spanning native zonal articular cartilage. Acta Biomater 2017; 64:41-49. [PMID: 29037894 DOI: 10.1016/j.actbio.2017.10.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/07/2017] [Accepted: 10/03/2017] [Indexed: 02/07/2023]
Abstract
Osteoarthrosis is a debilitating disease affecting millions, yet engineering materials for cartilage regeneration has proven difficult because of the complex microstructure of this tissue. Articular cartilage, like many biological tissues, produces a time-dependent response to mechanical load that is critical to cell's physiological function in part due to solid and fluid phase interactions and property variations across multiple length scales. Recreating the time-dependent strain and fluid flow may be critical for successfully engineering replacement tissues but thus far has largely been neglected. Here, microindentation is used to accomplish three objectives: (1) quantify a material's time-dependent mechanical response, (2) map material properties at a cellular relevant length scale throughout zonal articular cartilage and (3) elucidate the underlying viscoelastic, poroelastic, and nonlinear poroelastic causes of deformation in articular cartilage. Untreated and trypsin-treated cartilage was sectioned perpendicular to the articular surface and indentation was used to evaluate properties throughout zonal cartilage on the cut surface. The experimental results demonstrated that within all cartilage zones, the mechanical response was well represented by a model assuming nonlinear biphasic behavior and did not follow conventional viscoelastic or linear poroelastic models. Additionally, 10% (w/w) agarose was tested and, as anticipated, behaved as a linear poroelastic material. The approach outlined here provides a method, applicable to many tissues and biomaterials, which reveals and quantifies the underlying causes of time-dependent deformation, elucidates key aspects of material structure and function, and that can be used to provide important inputs for computational models and targets for tissue engineering. STATEMENT OF SIGNIFICANCE Elucidating the time-dependent mechanical behavior of cartilage, and other biological materials, is critical to adequately recapitulate native mechanosensory cues for cells. We used microindentation to map the time-dependent properties of untreated and trypsin treated cartilage throughout each cartilage zone. Unlike conventional approaches that combine viscoelastic and poroelastic behaviors into a single framework, we deconvoluted the mechanical response into separate contributions to time-dependent behavior. Poroelastic effects in all cartilage zones dominated the time-dependent behavior of articular cartilage, and a model that incorporates tension-compression nonlinearity best represented cartilage mechanical behavior. These results can be used to assess the success of regeneration and repair approaches, as design targets for tissue engineering, and for development of accurate computational models.
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Affiliation(s)
- Joseph A Wahlquist
- Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States
| | - Frank W DelRio
- Applied Chemicals and Materials Division, Material Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States
| | - Mark A Randolph
- Department of Orthopaedic Surgery, Laboratory for Musculoskeletal Tissue Engineering, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Division of Plastic Surgery, Plastic Surgery Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Aaron H Aziz
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, United States; BioFrontiers Institute, University of Colorado, Boulder, CO, United States
| | - Chelsea M Heveran
- Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States
| | - Stephanie J Bryant
- Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, United States; BioFrontiers Institute, University of Colorado, Boulder, CO, United States; Material Science and Engineering Program, University of Colorado, Boulder, CO, United States
| | - Corey P Neu
- Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States; BioFrontiers Institute, University of Colorado, Boulder, CO, United States
| | - Virginia L Ferguson
- Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States; BioFrontiers Institute, University of Colorado, Boulder, CO, United States; Material Science and Engineering Program, University of Colorado, Boulder, CO, United States.
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Nims RJ, Ateshian GA. Reactive Constrained Mixtures for Modeling the Solid Matrix of Biological Tissues. JOURNAL OF ELASTICITY 2017; 129:69-105. [PMID: 38523894 PMCID: PMC10959290 DOI: 10.1007/s10659-017-9630-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 03/26/2024]
Abstract
This article illustrates our approach for modeling the solid matrix of biological tissues using reactive constrained mixtures. Several examples are presented to highlight the potential benefits of this approach, showing that seemingly disparate fields of mechanics and chemical kinetics are actually closely interrelated and may be elegantly expressed in a unified framework. Thus, constrained mixture models recover classical theories for fibrous materials with bundles oriented in different directions or having different reference configurations, that produce characteristic fiber recruitment patterns under loading. Reactions that exchange mass among various constituents of a mixture may be used to describe tissue growth and remodeling, which may also alter the material's anisotropy. Similarly, reactions that describe the breaking and reforming of bonds may be used to model free energy dissipation in a viscoelastic material. Therefore, this framework is particularly well suited for modeling biological tissues.
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Affiliation(s)
- Robert J Nims
- Columbia University, 500 West 120th St, MC4703, New York, NY 10027, USA
| | - Gerard A Ateshian
- Columbia University, 500 West 120th St, MC4703, New York, NY 10027, USA
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How a decreased fibrillar interconnectivity influences stiffness and swelling properties during early cartilage degeneration. J Mech Behav Biomed Mater 2017; 75:390-398. [PMID: 28803113 DOI: 10.1016/j.jmbbm.2017.07.042] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 07/10/2017] [Accepted: 07/26/2017] [Indexed: 01/02/2023]
Abstract
OBJECTIVE The functional coupling between the fibrillar network and the high-swelling proteoglycans largely determines the mechanical properties of the articular cartilage matrix. The objective of this new study was to show specifically how changes in fibrillar interconnectivity arising from early cartilage degeneration influence transverse stiffness and swelling properties at the tissue level. DESIGN Radial zone transverse layers of cartilage matrix were obtained from intact and mildly degenerate bovine patellae. Each layer was then subdivided to assess tensile stiffness, free-swelling response, glycosaminoglycan (GAG) content, and micro- and ultra-structural features. RESULTS The tensile modulus was significantly lower and the degree of swelling significantly higher for the degenerate matrix compared to the intact. Scanning electron microscopy revealed a homogeneous response to transverse strain in the intact cartilage, whereas large non-fibrillar spaces between fibril aggregates were visible in the degenerate matrix. Although there were no significant differences in GAG content it did correlate significantly with stiffness and swelling in the intact samples but not in the degenerate. CONCLUSIONS The lower degree of fibril network interconnectivity in the degenerate matrix led to both a decreased transverse stiffness and reduced resistance to osmotic swelling. This network 'de-structuring' also resulted in a reduced functional interaction between the fibrillar network and the proteoglycans. The study provides new insights into the role of the fibrillar network and how changes in the network arising from the degenerative cascade will influence tissue level behaviour.
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32
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Iranmanesh F, Nazari MA. Finite Element Modeling of Avascular Tumor Growth Using a Stress-Driven Model. J Biomech Eng 2017; 139:2633189. [PMID: 28614573 DOI: 10.1115/1.4037038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Indexed: 11/08/2022]
Abstract
Tumor growth being a multistage process has been investigated from different aspects. In the present study, an attempt is made to represent a constitutive-structure-based model of avascular tumor growth in which the effects of tensile stresses caused by collagen fibers are considered. Collagen fibers as a source of anisotropy in the structure of tissue are taken into account using a continuous fiber distribution formulation. To this end, a finite element modeling is implemented in which a neo-Hookean hyperelastic material is assigned to the tumor and its surrounding host. The tumor is supplied with a growth term. The growth term includes the effect of parameters such as nutrient concentration on the tumor growth and the tumor's solid phase content in the formulation. Results of the study revealed that decrease of solid phase is indicative of decrease in growth rate and the final steady-state value of tumor's radius. Moreover, fiber distribution affects the final shape of the tumor, and it could be used to control the shape and geometry of the tumor in complex morphologies. Finally, the findings demonstrated that the exerted stresses on the tumor increase as time passes. Compression of tumor cells leads to the reduction of tumor growth rate until it gradually reaches an equilibrium radius. This finding is in accordance with experimental data. Hence, this formulation can be deployed to evaluate both the residual stresses induced by growth and the mechanical interactions with the host tissue.
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Affiliation(s)
- Faezeh Iranmanesh
- Department of Mechanical Engineering, College of Engineering, University of Tehran, Tehran 1439955961, Iran e-mail:
| | - Mohammad Ali Nazari
- Department of Mechanical Engineering, College of Engineering, University of Tehran, Tehran 1439955961, Iran e-mail:
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33
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Cooper BG, Lawson TB, Snyder BD, Grinstaff MW. Reinforcement of articular cartilage with a tissue-interpenetrating polymer network reduces friction and modulates interstitial fluid load support. Osteoarthritis Cartilage 2017; 25:1143-1149. [PMID: 28285000 PMCID: PMC5726233 DOI: 10.1016/j.joca.2017.03.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 02/12/2017] [Accepted: 03/01/2017] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Osteoarthritis (OA) is associated with increased articular cartilage hydraulic permeability and decreased maintenance of high interstitial fluid load support (IFLS) during articulation, resulting in increased friction on the cartilage solid matrix. This study assesses frictional response following in situ synthesis of an interpenetrating polymer network (IPN) designed to mimic glycosaminoglycans (GAGs) depleted during OA. METHODS Cylindrical osteochondral explants containing various interpenetrating polymer concentrations were subjected to a torsional friction test under unconfined creep compression. Time-varying coefficient of friction, compressive engineering strain, and normalized strain values (ε/εeq) were calculated and analyzed. RESULTS The polymer network reduced friction coefficient over the duration of the friction test, with statistically significantly reduced friction coefficients (95% confidence interval 14-34% reduced) at equilibrium compressive strain upon completion of the test (P = 0.015). A positive trend was observed relating polymer network concentration with magnitude of friction reduction compared to non-treated tissue. CONCLUSION The cartilage-interpenetrating polymer treatment improves lubrication by augmenting the biphasic tissue's interstitial fluid phase, and additionally improves the friction dissipation of the tissue's solid matrix. This technique demonstrates potential as a therapy to augment tribological function of articular cartilage.
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Affiliation(s)
- B G Cooper
- Department of Chemistry, Boston University, Boston, MA, USA; Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
| | - T B Lawson
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Mechanical Engineering, Boston University, Boston, MA, USA.
| | - B D Snyder
- Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA; Department of Medicine, Boston University, Boston, MA, USA; Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA, USA.
| | - M W Grinstaff
- Department of Chemistry, Boston University, Boston, MA, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA; Department of Medicine, Boston University, Boston, MA, USA.
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Ultrasound palpation for fast in-situ quantification of articular cartilage stiffness, thickness and relaxation capacity. Biomech Model Mechanobiol 2017; 16:1171-1185. [PMID: 28210824 DOI: 10.1007/s10237-017-0880-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 01/24/2017] [Indexed: 12/13/2022]
Abstract
Most current cartilage testing devices require the preparation of excised samples and therefore do not allow intra-operative application for diagnostic purposes. The gold standard during open or arthroscopic surgery is still the subjective perception of manual palpation. This work presents a new diagnostic method of ultrasound palpation (USP) to acquire applied stress and strain data during manual palpation of articular cartilage. With the proposed method, we obtain cartilage thickness and stiffness. Moreover, repeated palpations allow the quantification of relaxation effects. USP measurements on elastomer phantoms demonstrated very good repeatability for both, stage-guided (97.2%) and handheld (96.0%) applications. The USP measurements were compared with conventional indentation experiments and revealed very good agreement on elastomer phantoms ([Formula: see text]) and good agreement on porcine cartilage samples ([Formula: see text]). Artificially degenerated cartilage samples showed reduced stiffness, weak capacity to relax after palpation and an increase of stiffness of approximately 50% with each single palpation. Intact cartilage was measured by USP directly at the patella (in situ) and after excision and removal of the subchondral bone (ex situ), leading to stiffness values of [Formula: see text] and [Formula: see text] ([Formula: see text]), respectively. The results demonstrate the potential of the USP system for cartilage testing, its sensitivity to degenerative changes and as a method for quantifying relaxation processes by means of repeated palpations. Furthermore, the differences in the results of in-situ and ex-situ measurements are of general interest, since such comparison has not been reported previously. We point out the limited comparability of ex-situ cartilage with its in-situ biomechanical behavior.
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O’Connell G, Garcia J, Amir J. 3D Bioprinting: New Directions in Articular Cartilage Tissue Engineering. ACS Biomater Sci Eng 2017; 3:2657-2668. [DOI: 10.1021/acsbiomaterials.6b00587] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Grace O’Connell
- Department
of Mechanical Engineering University of California, Berkeley, 5122 Etcheverry Hall, Berkeley, California 94720, United States
| | - Jeanette Garcia
- IBM Research-Almaden, 650
Harry Road K17/D2, San Jose, California 95120, United States
| | - Jamali Amir
- Joint Preservation Institute, 2825 J Street #440, Sacramento, California 95816, United States
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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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Han WM, Heo SJ, Driscoll TP, Delucca JF, McLeod CM, Smith LJ, Duncan RL, Mauck RL, Elliott DM. Microstructural heterogeneity directs micromechanics and mechanobiology in native and engineered fibrocartilage. NATURE MATERIALS 2016; 15:477-84. [PMID: 26726994 PMCID: PMC4805445 DOI: 10.1038/nmat4520] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 11/24/2015] [Indexed: 05/05/2023]
Abstract
Treatment strategies to address pathologies of fibrocartilaginous tissue are in part limited by an incomplete understanding of structure-function relationships in these load-bearing tissues. There is therefore a pressing need to develop micro-engineered tissue platforms that can recreate the highly inhomogeneous tissue microstructures that are known to influence mechanotransductive processes in normal and diseased tissue. Here, we report the quantification of proteoglycan-rich microdomains in developing, ageing and diseased fibrocartilaginous tissues, and the impact of these microdomains on endogenous cell responses to physiologic deformation within a native-tissue context. We also developed a method to generate heterogeneous tissue-engineered constructs (hetTECs) with non-fibrous proteoglycan-rich microdomains engineered into the fibrous structure, and show that these hetTECs match the microstructural, micromechanical and mechanobiological benchmarks of native tissue. Our tissue-engineered platform should facilitate the study of the mechanobiology of developing, homeostatic, degenerating and regenerating fibrous tissues.
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Affiliation(s)
- Woojin M Han
- Department of Bioengineering, University of Pennsylvania
| | - Su-Jin Heo
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - Tristan P Driscoll
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - John F Delucca
- Department of Biomedical Engineering, University of Delaware
| | - Claire M McLeod
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
| | - Lachlan J Smith
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
- Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania
| | - Randall L Duncan
- Department of Biomedical Engineering, University of Delaware
- Department of Biological Sciences, University of Delaware
| | - Robert L Mauck
- Department of Bioengineering, University of Pennsylvania
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania
- Addresses for Correspondence: Dawn M. Elliott, Ph.D., Professor and Director of Biomedical Engineering, Department of Biomedical Engineering, University of Delaware, 161 Colburn Laboratory, Newark, DE 19716, Phone: (302) 831-4578, . Robert L. Mauck, Ph.D., Associate Professor of Orthopaedic Surgery and Bioengineering, Director, McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 36 Street and Hamilton Walk, Philadelphia, PA 19104, Phone: (215) 898-3294,
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware
- Addresses for Correspondence: Dawn M. Elliott, Ph.D., Professor and Director of Biomedical Engineering, Department of Biomedical Engineering, University of Delaware, 161 Colburn Laboratory, Newark, DE 19716, Phone: (302) 831-4578, . Robert L. Mauck, Ph.D., Associate Professor of Orthopaedic Surgery and Bioengineering, Director, McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, 36 Street and Hamilton Walk, Philadelphia, PA 19104, Phone: (215) 898-3294,
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Roach BL, Kelmendi-Doko A, Balutis EC, Marra KG, Ateshian GA, Hung CT. Dexamethasone Release from Within Engineered Cartilage as a Chondroprotective Strategy Against Interleukin-1α. Tissue Eng Part A 2016; 22:621-32. [PMID: 26956216 DOI: 10.1089/ten.tea.2016.0018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
While significant progress has been made toward engineering functional cartilage constructs with mechanical properties suitable for in vivo loading, the impact on these grafts of inflammatory cytokines, chemical factors that are elevated with trauma or osteoarthritis, is poorly understood. Previous work has shown dexamethasone to be a critical compound for cultivating cartilage with functional properties, while also providing chondroprotection from proinflammatory cytokines. This study tested the hypothesis that the incorporation of poly(lactic-co-glycolic acid) (PLGA) (75:25) microspheres that release dexamethasone from within chondrocyte-seeded agarose hydrogel constructs would promote development of constructs with functional properties and protect constructs from the deleterious effects of interleukin-1α (IL-1α). After 28 days of growth culture, experimental groups were treated with IL-1α (10 ng/mL) for 7 days. Reaching native equilibrium moduli and proteoglycan levels, dexamethasone-loaded microsphere constructs exhibited tissue properties similar to microsphere-free control constructs cultured in dexamethasone-supplemented culture media and were insensitive to IL-1α exposure. These findings are in stark contrast to constructs containing dexamethasone-free microspheres or no microspheres, cultured without dexamethasone, where IL-1α exposure led to significant tissue degradation. These results support the use of dexamethasone delivery from within engineered cartilage, through biodegradable microspheres, as a strategy to produce mechanically functional tissues that can also combat the deleterious effects of local proinflammatory cytokine exposure.
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Affiliation(s)
- Brendan L Roach
- 1 Department of Biomedical Engineering, Columbia University , New York, New York
| | - Arta Kelmendi-Doko
- 2 Department of Bioengineering, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Elaine C Balutis
- 3 Department of Orthopedics and Sports Medicine, Mount Sinai Health System , New York, New York
| | - Kacey G Marra
- 2 Department of Bioengineering, University of Pittsburgh , Pittsburgh, Pennsylvania.,4 McGowan Institute for Regenerative Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania.,5 Department of Plastic Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Gerard A Ateshian
- 1 Department of Biomedical Engineering, Columbia University , New York, New York.,6 Department of Mechanical Engineering, Columbia University , New York, New York
| | - Clark T Hung
- 1 Department of Biomedical Engineering, Columbia University , New York, New York
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Sakai N, Hashimoto C, Yarimitsu S, Sawae Y, Komori M, Murakami T. A functional effect of the superficial mechanical properties of articular cartilage as a load bearing system in a sliding condition. BIOSURFACE AND BIOTRIBOLOGY 2016. [DOI: 10.1016/j.bsbt.2016.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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Nims RJ, Durney KM, Cigan AD, Dusséaux A, Hung CT, Ateshian GA. Continuum theory of fibrous tissue damage mechanics using bond kinetics: application to cartilage tissue engineering. Interface Focus 2016; 6:20150063. [PMID: 26855751 DOI: 10.1098/rsfs.2015.0063] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This study presents a damage mechanics framework that employs observable state variables to describe damage in isotropic or anisotropic fibrous tissues. In this mixture theory framework, damage is tracked by the mass fraction of bonds that have broken. Anisotropic damage is subsumed in the assumption that multiple bond species may coexist in a material, each having its own damage behaviour. This approach recovers the classical damage mechanics formulation for isotropic materials, but does not appeal to a tensorial damage measure for anisotropic materials. In contrast with the classical approach, the use of observable state variables for damage allows direct comparison of model predictions to experimental damage measures, such as biochemical assays or Raman spectroscopy. Investigations of damage in discrete fibre distributions demonstrate that the resilience to damage increases with the number of fibre bundles; idealizing fibrous tissues using continuous fibre distribution models precludes the modelling of damage. This damage framework was used to test and validate the hypothesis that growth of cartilage constructs can lead to damage of the synthesized collagen matrix due to excessive swelling caused by synthesized glycosaminoglycans. Therefore, alternative strategies must be implemented in tissue engineering studies to prevent collagen damage during the growth process.
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Affiliation(s)
- Robert J Nims
- Department of Biomedical Engineering , Columbia University , 500 West 120th Street, MC4703, New York, NY 10027 , USA
| | - Krista M Durney
- Department of Biomedical Engineering , Columbia University , 500 West 120th Street, MC4703, New York, NY 10027 , USA
| | - Alexander D Cigan
- Department of Biomedical Engineering , Columbia University , 500 West 120th Street, MC4703, New York, NY 10027 , USA
| | - Antoine Dusséaux
- Department of Mechanical Engineering , Columbia University , 500 West 120th Street, MC4703, New York, NY 10027 , USA
| | - Clark T Hung
- Department of Biomedical Engineering , Columbia University , 500 West 120th Street, MC4703, New York, NY 10027 , USA
| | - Gerard A Ateshian
- Department of Biomedical Engineering, Columbia University, 500 West 120th Street, MC4703, New York, NY 10027, USA; Department of Mechanical Engineering, Columbia University, 500 West 120th Street, MC4703, New York, NY 10027, USA
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DeLucca JF, Cortes DH, Jacobs NT, Vresilovic EJ, Duncan RL, Elliott DM. Human cartilage endplate permeability varies with degeneration and intervertebral disc site. J Biomech 2016; 49:550-7. [PMID: 26874969 DOI: 10.1016/j.jbiomech.2016.01.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 01/07/2016] [Accepted: 01/08/2016] [Indexed: 01/08/2023]
Abstract
Despite the critical functions the human cartilage endplate (CEP) plays in the intervertebral disc, little is known about its structural and mechanical properties and their changes with degeneration. Quantifying these changes with degeneration is important for understanding how the CEP contributes to the function and pathology of the disc. Therefore the objectives of this study were to quantify the effect of disc degeneration on human CEP mechanical properties, determine the influence of superior and inferior disc site on mechanics and composition, and simulate the role of collagen fibers in CEP and disc mechanics using a validated finite element model. Confined compression data and biochemical composition data were used in a biphasic-swelling model to calculate compressive extrafibrillar elastic and permeability properties. Tensile properties were obtained by applying published tensile test data to an ellipsoidal fiber distribution. Results showed that with degeneration CEP permeability decreased 50-60% suggesting that transport is inhibited in the degenerate disc. CEP fibers are organized parallel to the vertebrae and nucleus pulposus and may contribute to large shear strains (0.1-0.2) and delamination failure of the CEP commonly seen in herniated disc tissue. Fiber-reinforcement also reduces CEP axial strains thereby enhancing fluid flux by a factor of 1.8. Collectively, these results suggest that the structure and mechanics of the CEP may play critical roles in the solute transport and disc mechanics.
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Affiliation(s)
- John F DeLucca
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Daniel H Cortes
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States
| | - Nathan T Jacobs
- Department of Mechanical Engineering, University of Pennsylvania, Philadelphia, PA, United States
| | - Edward J Vresilovic
- Penn State Hershey Bone and Joint Institute Pennsylvania State University, Hershey, PA, United States
| | - Randall L Duncan
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States; Department of Biological Sciences, University of Delaware, Newark, DE, United States
| | - Dawn M Elliott
- Department of Biomedical Engineering, University of Delaware, Newark, DE, United States.
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42
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On the stiffness of demineralized dentin matrices. Dent Mater 2015; 32:161-70. [PMID: 26747822 DOI: 10.1016/j.dental.2015.11.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 11/17/2015] [Accepted: 11/30/2015] [Indexed: 01/29/2023]
Abstract
UNLABELLED Resin bonding to dentin requires the use of self-etching primers or acid etching to decalcify the surface and expose a layer of collagen fibrils of the dentin matrix. Acid-etching reduces the stiffness of demineralized dentin from approximately 19 GPa-1 MPa, requiring that it floats in water to prevent it from collapsing during bonding procedures. Several publications show that crosslinking agents like gluteraladehyde, carbodiimide or grape seed extract can stiffen collagen and improve resin-dentin bond strength. OBJECTIVE The objective was to assess a new approach for evaluating the changes in stiffness of decalcified dentin by polar solvents and a collagen cross-linker. METHODS Fully demineralized dentin beams and sections of etched coronal dentin were subjected to indentation loading using a cylindrical flat indenter in water, and after treatment with ethanol or ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). The stiffness was measured as a function of strain and as a function of loading rate from 1 to 50 μm/s. RESULTS At a strain of 0.25% the elastic modulus of the fully demineralized dentin was approximately 0.20 MPa. It increased to over 0.90 MPa at strains of 1%. Exposure to ethanol caused an increase in elastic modulus of up to four times. Increasing the loading rate from 1 to 50 μm/s caused an increase in the apparent modulus of up to three times in both water and ethanol. EDC treatment caused increases in the stiffness in fully demineralized samples and in acid-etched demineralized dentin surfaces in situ. SIGNIFICANCE Changes in the mechanical behavior of demineralized collagen matrices can be measured effectively under hydration via indentation with cylindrical flat indenters. This approach can be used for quantifying the effects of bonding treatments on the properties of decalcified dentin after acid etching, as well as to follow the loss of stiffness over time due to enzymatic degradation.
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Chen X, Zhou Y, Wang L, Santare MH, Wan LQ, Lu XL. Determining Tension-Compression Nonlinear Mechanical Properties of Articular Cartilage from Indentation Testing. Ann Biomed Eng 2015; 44:1148-58. [PMID: 26240062 DOI: 10.1007/s10439-015-1402-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 07/18/2015] [Indexed: 11/30/2022]
Abstract
The indentation test is widely used to determine the in situ biomechanical properties of articular cartilage. The mechanical parameters estimated from the test depend on the constitutive model adopted to analyze the data. Similar to most connective tissues, the solid matrix of cartilage displays different mechanical properties under tension and compression, termed tension-compression nonlinearity (TCN). In this study, cartilage was modeled as a porous elastic material with either a conewise linear elastic matrix with cubic symmetry or a solid matrix reinforced by a continuous fiber distribution. Both models are commonly used to describe the TCN of cartilage. The roles of each mechanical property in determining the indentation response of cartilage were identified by finite element simulation. Under constant loading, the equilibrium deformation of cartilage is mainly dependent on the compressive modulus, while the initial transient creep behavior is largely regulated by the tensile stiffness. More importantly, altering the permeability does not change the shape of the indentation creep curves, but introduces a parallel shift along the horizontal direction on a logarithmic time scale. Based on these findings, a highly efficient curve-fitting algorithm was designed, which can uniquely determine the three major mechanical properties of cartilage (compressive modulus, tensile modulus, and permeability) from a single indentation test. The new technique was tested on adult bovine knee cartilage and compared with results from the classic biphasic linear elastic curve-fitting program.
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Affiliation(s)
- Xingyu Chen
- Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL 126, Newark, DE, 19716, USA
| | - Yilu Zhou
- Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL 126, Newark, DE, 19716, USA
| | - Liyun Wang
- Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL 126, Newark, DE, 19716, USA
| | - Michael H Santare
- Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL 126, Newark, DE, 19716, USA
| | - Leo Q Wan
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - X Lucas Lu
- Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL 126, Newark, DE, 19716, USA.
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Bartell LR, Fortier LA, Bonassar LJ, Cohen I. Measuring microscale strain fields in articular cartilage during rapid impact reveals thresholds for chondrocyte death and a protective role for the superficial layer. J Biomech 2015; 48:3440-6. [PMID: 26150096 DOI: 10.1016/j.jbiomech.2015.05.035] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/11/2015] [Accepted: 05/26/2015] [Indexed: 10/23/2022]
Abstract
Articular cartilage is a heterogeneous soft tissue that dissipates and distributes loads in mammalian joints. Though robust, cartilage is susceptible to damage from loading at high rates or magnitudes. Such injurious loads have been implicated in degenerative changes, including chronic osteoarthritis (OA), which remains a leading cause of disability in developed nations. Despite decades of research, mechanisms of OA initiation after trauma remain poorly understood. Indeed, although bulk cartilage mechanics are measurable during impact, current techniques cannot access microscale mechanics at those rapid time scales. We aimed to address this knowledge gap by imaging the microscale mechanics and corresponding acute biological changes of cartilage in response to rapid loading. In this study, we utilized fast-camera and confocal microscopy to achieve roughly 85 µm spatial resolution of both the cartilage deformation during a rapid (~3 ms), localized impact and the chondrocyte death following impact. Our results showed that, at these high rates, strain and chondrocyte death were highly correlated (p<0.001) with a threshold of 8% microscale strain norm before any cell death occurred. Additionally, chondrocyte death had developed by two hours after impact, suggesting a time frame for clinical therapeutics. Moreover, when the superficial layer was removed, strain - and subsequently chondrocyte death - penetrated deeper into the samples (p<0.001), suggesting a protective role for the superficial layer of articular cartilage. Combined, these results provide insight regarding the detailed biomechanics that drive early chondrocyte damage after trauma and emphasize the importance of understanding cartilage and its mechanics on the microscale.
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Affiliation(s)
- Lena R Bartell
- School of Applied and Engineering Physics, C7 Clark Hall, Cornell University, Ithaca, NY 14853, USA.
| | - Lisa A Fortier
- Department of Clinical Sciences, Cornell University, Ithaca, NY, USA
| | - Lawrence J Bonassar
- Department of Biomedical Engineering, Cornell University, Ithaca, NY, USA; Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA
| | - Itai Cohen
- Department of Physics, Cornell University, Ithaca, NY, USA
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Pierce DM, Unterberger MJ, Trobin W, Ricken T, Holzapfel GA. A microstructurally based continuum model of cartilage viscoelasticity and permeability incorporating measured statistical fiber orientations. Biomech Model Mechanobiol 2015; 15:229-44. [DOI: 10.1007/s10237-015-0685-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 05/15/2015] [Indexed: 12/21/2022]
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Oungoulian SR, Durney KM, Jones BK, Ahmad CS, Hung CT, Ateshian GA. Wear and damage of articular cartilage with friction against orthopedic implant materials. J Biomech 2015; 48:1957-64. [PMID: 25912663 DOI: 10.1016/j.jbiomech.2015.04.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 03/31/2015] [Accepted: 04/03/2015] [Indexed: 10/23/2022]
Abstract
The objective of this study was to measure the wear response of immature bovine articular cartilage tested against glass or alloys used in hemiarthroplasties. Two cobalt chromium alloys and a stainless steel alloy were selected for these investigations. The surface roughness of one of the cobalt chromium alloys was also varied within the range considered acceptable by regulatory agencies. Cartilage disks were tested in a configuration that promoted loss of interstitial fluid pressurization to accelerate conditions believed to occur in hemiarthroplasties. Results showed that considerably more damage occurred in cartilage samples tested against stainless steel (10 nm roughness) and low carbon cobalt chromium alloy (27 nm roughness) compared to glass (10 nm) and smoother low or high carbon cobalt chromium (10 nm). The two materials producing the greatest damage also exhibited higher equilibrium friction coefficients. Cartilage damage occurred primarily in the form of delamination at the interface between the superficial tangential zone and the transitional middle zone, with much less evidence of abrasive wear at the articular surface. These results suggest that cartilage damage from frictional loading occurs as a result of subsurface fatigue failure leading to the delamination. Surface chemistry and surface roughness of implant materials can have a significant influence on tissue damage, even when using materials and roughness values that satisfy regulatory requirements.
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Affiliation(s)
- Sevan R Oungoulian
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA
| | - Krista M Durney
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA
| | - Brian K Jones
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA
| | - Christopher S Ahmad
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA
| | - Clark T Hung
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA
| | - Gerard A Ateshian
- Departments of Mechanical Engineering, Biomedical Engineering, and Orthopaedic Surgery, Columbia University, New York, NY, USA.
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Misra A, Parthasarathy R, Singh V, Spencer P. Micro-poromechanics model of fluid-saturated chemically active fibrous media. ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2015; 95:215-234. [PMID: 25755301 PMCID: PMC4351821 DOI: 10.1002/zamm.201300071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete.
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Affiliation(s)
- Anil Misra
- University of Kansas, Civil, Environmental and Architectural Engineering Department, Lawrence, KS 66045, USA
- University of Kansas, Bioengineering Research Center (BERC), Lawrence, KS 66045, USA
| | - Ranganathan Parthasarathy
- University of Kansas, Bioengineering Research Center (BERC), Lawrence, KS 66045, USA
- University of Kansas, Bioengineering Graduate Program, Lawrence, KS 66045, USA
| | - Viraj Singh
- University of Kansas, Mechanical Engineering Department, Lawrence, KS 66045, USA
| | - Paulette Spencer
- University of Kansas, Bioengineering Research Center (BERC), Lawrence, KS 66045, USA
- University of Kansas, Mechanical Engineering Department, Lawrence, KS 66045, USA
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SAKAI N, HAGIHARA Y, HASHIMOTO C, KOMORI M, SAWAE Y, MURAKAMI T. An estimation of mechanical propertes of articular cartilage for biphasic finite element analyses. ACTA ACUST UNITED AC 2015. [DOI: 10.1299/jbse.15-00228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Nobuo SAKAI
- Graduate School of Engineering, Kyushu Institute of Technology
| | | | - Chie HASHIMOTO
- Graduate School of Engineering, Kyushu Institute of Technology
| | | | | | - Teruo MURAKAMI
- Research Center for Advanced Biomechanics, Kyushu University
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Henak CR, Ateshian GA, Weiss JA. Finite element prediction of transchondral stress and strain in the human hip. J Biomech Eng 2014; 136:021021. [PMID: 24292495 DOI: 10.1115/1.4026101] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 11/27/2013] [Indexed: 11/08/2022]
Abstract
Cartilage fissures, surface fibrillation, and delamination represent early signs of hip osteoarthritis (OA). This damage may be caused by elevated first principal (most tensile) strain and maximum shear stress. The objectives of this study were to use a population of validated finite element (FE) models of normal human hips to evaluate the required mesh for converged predictions of cartilage tensile strain and shear stress, to assess the sensitivity to cartilage constitutive assumptions, and to determine the patterns of transchondral stress and strain that occur during activities of daily living. Five specimen-specific FE models were evaluated using three constitutive models for articular cartilage: quasilinear neo-Hookean, nonlinear Veronda Westmann, and tension-compression nonlinear ellipsoidal fiber distribution (EFD). Transchondral predictions of maximum shear stress and first principal strain were determined. Mesh convergence analysis demonstrated that five trilinear elements were adequate through the depth of the cartilage for precise predictions. The EFD model had the stiffest response with increasing strains, predicting the largest peak stresses and smallest peak strains. Conversely, the neo-Hookean model predicted the smallest peak stresses and largest peak strains. Models with neo-Hookean cartilage predicted smaller transchondral gradients of maximum shear stress than those with Veronda Westmann and EFD models. For FE models with EFD cartilage, the anterolateral region of the acetabulum had larger peak maximum shear stress and first principal strain than all other anatomical regions, consistent with observations of cartilage damage in disease. Results demonstrate that tension-compression nonlinearity of a continuous fiber distribution exhibiting strain induced anisotropy incorporates important features that have large effects on predictions of transchondral stress and strain. This population of normal hips provides baseline data for future comparisons to pathomorphologic hips. This approach can be used to evaluate these and other mechanical variables in the human hip and their potential role in the pathogenesis of osteoarthritis (OA).
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Taffetani M, Gottardi R, Gastaldi D, Raiteri R, Vena P. Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths. Med Eng Phys 2014; 36:850-8. [DOI: 10.1016/j.medengphy.2014.03.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 02/14/2014] [Accepted: 03/23/2014] [Indexed: 10/25/2022]
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