Properties Of Human Articular Cartilage Research Articles

Biodegradable-Glass-Fiber Reinforced Hydrogel Composite with Enhanced Mechanical Performance and Cell Proliferation for Potential Cartilage Repair.

Polyvinyl alcohol (PVA) hydrogels are promising implants due to the similarity of their low-friction behavior to that of cartilage tissue, and also due to their non-cytotoxicity. However, their poor mechanical resistance and insufficient durability restricts their application in this area. With the development of biodegradable glass fibers (BGF), which show desirable mechanical performance and bioactivity for orthopedic engineering, we designed a novel PVA hydrogel composite reinforced with biodegradable glass fibers, intended for use in artificial cartilage repair with its excellent cytocompatibility and long-term mechanical stability. Using structure characterization and thermal properties analysis, we found hydrogen bonding occurred among PVA molecular networks as well as in the PVA–BGF interface, which explained the increase in crystallinity and glass transition temperature, and was the reason for the improved mechanical performance and better anti-fatigue behavior of the composites in comparison with PVA. The compressive strength and modulus for the PBGF-15 composite reached 3.05 and 3.97 MPa, respectively, equaling the mechanical properties of human articular cartilage. Moreover, the increase in BGF content was found to support the proliferation of chondrocytes in vitro, whilst the PVA hydrogel matrix was able to control the ion concentration by adjusting the ions released from the BGF. Therefore, this novel biodegradable-glass-fiber-reinforced hydrogel composite possesses excellent properties for cartilage repair with potential in medical application.

Structure\u2013Function Relationships of Healthy and Osteoarthritic Human Tibial Cartilage: Experimental and Numerical Investigation

Relationships between composition, structure and constituent-specific functional properties of human articular cartilage at different stages of osteoarthritis (OA) are poorly known. We established these relationships by comparison of elastic, viscoelastic and fibril-reinforced poroelastic mechanical properties with microscopic and spectroscopic analysis of structure and composition of healthy and osteoarthritic human tibial cartilage (n = 27). At a low frequency (0.005 Hz), proteoglycan content correlated negatively and collagen content correlated positively with the phase difference (i.e. tissue viscosity). At a high-frequency regime (> 0.05 Hz), proteoglycan content correlated negatively and collagen orientation angle correlated positively with the phase difference. Proteoglycans were lost in the early and advanced OA groups compared to the healthy group, while the superficial collagen orientation angle was greater only in the advanced OA group compared to the healthy group. Simultaneously, the initial fibril network modulus (fibril pretension) was smaller in the early and advanced OA groups compared to the healthy group. These findings suggest different mechanisms contribute to cartilage viscosity in low and high frequencies, and that the loss of superficial collagen pretension during early OA is due to lower tissue swelling (PG loss), while in advanced OA, both collagen disorganization and lower swelling modulate the collagen fibril pretension.

Zone-dependent mechanical properties of human articular cartilage obtained by indentation measurements.

Emerging 3D printing technology permits innovative approaches to manufacture cartilage scaffolds associated with layer-by-layer mechanical property adaptation. However, information about gradients of mechanical properties in human articular cartilage is limited. In this study, we quantified a zone-dependent change of local elastic modulus of human femoral condyle cartilage by using an instrumented indentation technique. From the cartilage superficial zone towards the calcified layer, a gradient of elastic modulus values between 0.020 ± 0.003 MPa and 6.44 ± 1.02 MPa was measured. To validate the tissue quality, the histological tissue composition was visualized by glycosaminoglycan and collagen staining. This work aims to introduce a new protocol to investigate the zone-dependent mechanical properties of graded structures, such as human articular cartilage. From this knowledge, better cartilage repair strategies could be tailored in the future.

Biofabricated soft network composites for cartilage tissue engineering

Articular cartilage from a material science point of view is a soft network composite that plays a critical role in load-bearing joints during dynamic loading. Its composite structure, consisting of a collagen fiber network and a hydrated proteoglycan matrix, gives rise to the complex mechanical properties of the tissue including viscoelasticity and stress relaxation. Melt electrospinning writing allows the design and fabrication of medical grade polycaprolactone (mPCL) fibrous networks for the reinforcement of soft hydrogel matrices for cartilage tissue engineering. However, these fiber-reinforced constructs underperformed under dynamic and prolonged loading conditions, suggesting that more targeted design approaches and material selection are required to fully exploit the potential of fibers as reinforcing agents for cartilage tissue engineering. In the present study, we emulated the proteoglycan matrix of articular cartilage by using highly negatively charged star-shaped poly(ethylene glycol)/heparin hydrogel (sPEG/Hep) as the soft matrix. These soft hydrogels combined with mPCL melt electrospun fibrous networks exhibited mechanical anisotropy, nonlinearity, viscoelasticity and morphology analogous to those of their native counterpart, and provided a suitable microenvironment for in vitro human chondrocyte culture and neocartilage formation. In addition, a numerical model using the p-version of the finite element method (p-FEM) was developed in order to gain further insights into the deformation mechanisms of the constructs in silico, as well as to predict compressive moduli. To our knowledge, this is the first study presenting cartilage tissue-engineered constructs that capture the overall transient, equilibrium and dynamic biomechanical properties of human articular cartilage.

Structure and nanomechanics of collagen fibrils in articular cartilage at different stages of osteoarthritis

This study aimed to investigate the variation of structure and nanomechanical properties of human articular cartilage (AC) at different stages of osteoarthritis (OA).

The mechanical and material properties of elderly human articular cartilage subject to impact and slow loading

The mechanical properties of articular cartilage vary enormously with loading rate, and how these properties derive from the composition and structure of the tissue is still unclear. This study investigates the mechanical properties of human articular cartilage at rapid rates of loading, compares these with measurements at slow rates of loading and explores how they relate to the gross composition of the tissue. Full-depth femoral head cartilage biopsies were subjected to a slow, unconfined compression test followed by an impact at an energy of 78.5mJ and velocity 1.25ms−1. The modulus was calculated from the slope of the loading curve and the coefficient of restitution from the areas under the loading and unloading curves.Tissue composition was measured as water, collagen and glycosaminoglycan contents. The maximum dynamic modulus ranged from 25 to 150MPa. These values compared with 1–3MPa measured during quasi-static loading. The coefficient of restitution was 0.502 (0.066) (mean (standard deviation)) and showed no site variation. Water loss was not detectable. Composition was not strongly associated with modulus; water and collagen contents together predicted about 25% of the variance in modulus.

A Portable Arthroscopic Diagnostic Probe to Measure the Viscoelasticity of Articular Cartilage

Tissue engineering has been increasingly applied to treat diseases of the joints that adversely affect components such as cartilage and ligaments. These components do not contain blood vessels and nerves; the risk of rejection during tissue transplantation is therefore less than that for other organs. Treatment of cartilage and ligaments requires highly skilled surgeons, however, and it is necessary to establish a quantitative evaluation method. It is difficult to measure the mechanical properties of cartilage because of its viscoelasticity. Sensing technology that enables uniform qualitative evaluation is therefore desired. In this study, a portable diagnostic probe was developed and the viscoelasticity of cartilage was measured quantitatively over a short period of time. The probe was designed based on the Voigt model and comprises a piezoelectric actuator, a force sensor, and a contact probe. Stiffness and viscosity coefficients of various samples such as silicone rubber and the bovine meniscus were measured, and the accuracy of the developed probe was evaluated. Finally, the mechanical properties of human articular cartilage were measured using the diagnostic probe.

5.3 Streaming potentials measured with an arthroscopic medical device are reliable indicators of biochemical and biomechanical properties of human articular cartilage

5.3 Streaming potentials measured with an arthroscopic medical device are reliable indicators of biochemical and biomechanical properties of human articular cartilage

The effects of storage temperature on the composition, metabolism and biomechanical properties of human articular cartilage

Osteochondral tibial specimens were stored for up to 84 days in DMEM +20% FCS at 4 or 37°C. Articular cartilage from specimens stored at 4°C showed significant proteoglycan depletion, with 78% loss in 84 days. Proteoglycan synthesis declined markedly during the first 3 days in storage. Mechanical analysis revealed cartilage stiffness to be reduced by 60% by the end of the storage period. By contrast, cartilage from specimens stored at 37°C showed no significant depletion of glycosaminoglycan and retained 66% of its initial mechanical stiffness. Proteoglycan synthesis was again reduced but the onset and magnitude of the decline was less than in samples stored at 4°C. Storage at 37°C promises to be useful in banking cartilage prior to clinical use.

In vivo sodium multiple quantum spectroscopy of human articular cartilage.

The authors report, for the first time, sodium properties of human articular cartilage in vivo using sodium multiple-quantum-filtered methods with a surface coil. A flip angle-independent, phase-cycled pulse sequence was used to obtain triple-quantum-filtered spectra as a function of preparation time. Biexponential relaxation rates were calculated by fitting the triple-quantum-filtered spectral amplitudes to a theoretical expression. Theoretical analysis of the flip angle dependence of even rank two-quantum coherence (T2[2]), odd rank two-quantum coherence (T2[3]), and triple-quantum coherence are presented and verified against experimental results on a cartilage specimen. Sodium multiple-quantum-filtered spectral lineshapes obtained in vivo correlate well with those observed on in vitro specimens. Relaxation rates obtained from asymptomatic volunteers were found to be: T(2rise) = 1.0 + 0.12 ms, T(2decay) = 12.0 +/- 0.75 ms (mean +/- SD). The diagnostic potential of this method in detecting early changes in articular cartilage is described.

Age-related changes in the tensile properties of human articular cartilage: a comparative study between the femoral head of the hip joint and the talus of the ankle joint

Specimens of articular cartilage from the superficial and mid-depth zones of the human femoral head and the talus of the ankle joint were tested in tension in planes parallel to the articular surface and parallel to the predominant orientation of the superficial collagen fibrils. The tensile fracture stress of cartilage from both the superficial and mid-depth zones of the femoral head decreases considerably with age. The superficial zone decreased from 33 MPa at 7 years to 10 MPa by the age of 90 years, while the mid-depth zone decreased from 32 MPa at 7 years to 2 MPa by the age of 85 years. In contrast the fracture stress of both levels of cartilage from the talus of the ankle did not decrease significantly with increasing age. The tensile stiffness at 10 MPa of both the superficial and mid-depth zones of the femoral head decreased with age. That of the superficial zone decreased from 150 MPa at 7 years to 80 MPa at 90 years, while the mid-depth zone decreased from 60 MPa at 7 years to 10 MPa at 60 years. The stiffness of talar cartilage from the superficial zone decreased by 20%, while that of the mid-depth zone showed a slight increase in stiffness at 10 MPa with increasing age. There was no significant decrease in the tensile stiffness at 1 MPa with age for either the femoral head or talar cartilage. Based on the results of previous studies it is possible to conclude that the decrease in tensile properties seen in the femoral head results from a deterioration in the tensile properties of the network of collagen fibrils. It is suggested that progressive fatigue failure, perhaps with associated changes in the structure of cartilage due to altered chondrocyte metabolism, causes the reduction in tensile properties with age. The results offer a potential explanation for the observation that osteoarthritis commonly occurs in the hip and knee joints at an increasing incidence as age increases, while the condition only rarely occurs in the ankle joint except as a secondary event to trauma.

Mechanical and biochemical properties of human articular cartilage in osteoarthritic femoral heads and in autopsy specimens : Roberts S, Weightman B, Urban J, Chappell D, J Bone Joint Surg 1986; 68B: 278–288

Mechanical and biochemical properties of human articular cartilage in osteoarthritic femoral heads and in autopsy specimens : Roberts S, Weightman B, Urban J, Chappell D, J Bone Joint Surg 1986; 68B: 278–288

Mechanical and biochemical properties of human articular cartilage from the femoral head after subcapital fracture.

Articular cartilage from the femoral heads of 27 patients having an arthroplasty for subcapital fracture was studied, and its mechanical and chemical properties compared to those of a group of 33 age-matched macroscopically normal autopsy specimens. Water and proteoglycan contents were measured, as were swelling ability, compressive and tensile strength of the cartilage, and the density of the underlying bone. Cartilage from the fracture specimens had a significantly reduced proteoglycan content, as measured by fixed charge density, and increased swelling ability. These results indicate that this group differs from the "normal" population and care should be taken before they are accepted as control material for studies on osteoarthritic cartilage. Another finding was that bone density was much the same in the fracture and the normal group. This casts some doubt upon the concept that patients who sustain subcapital fractures are more osteoporotic than the average for the same age range.

Mechanical and biochemical properties of human articular cartilage in osteoarthritic femoral heads and in autopsy specimens.

We studied the mechanical and biochemical properties of articular cartilage from 22 osteoarthritic femoral heads obtained at operation and 97 femoral heads obtained at autopsy. Cartilage from the zenith and from the antero-inferior aspect of each head was tested both in tension and in compression. Water content, swelling ability and proteoglycan content were measured, the cartilage was examined histologically and the density of the underlying bone was assessed. Fifty-five of the autopsy specimens were defined as macroscopically normal because they exhibited no progressive fibrillation patterns on staining with Indian ink; but significant changes in water content, bone density and tensile strength related to age were seen in this group. In 20 pairs of femoral heads which were both macroscopically normal, we found, surprisingly, that cartilage from the left and right sides of the same patient was sometimes very different. Compared with the normal autopsy specimens the osteoarthritic specimens had a significantly increased swelling ability, a lower proteoglycan content and impaired mechanical properties, being both weaker in tension and softer in compression. Abnormal autopsy specimens had values intermediate between those of osteoarthritic and normal groups. Results from this abnormal group suggest that there is no primary loss of proteoglycan in early osteoarthritis.

Variations in the intrinsic mechanical properties of human articular cartilage with age, degeneration, and water content.

In a series of 103 specimens from the lateral facet of the human patella, the intrinsic mechanical properties of articular cartilage were measured using a confined compression creep test. By considering the cartilage as a porous, permeable solid filed with fluid, this experimental procedure allowed the determination of the intrinsic equilibrium modulus of the cartilage matrix and its permeability to fluid flow. The intrinsic equilibrium modulus and the permeability both were highly correlated with the water content of the tissue; as water content increased, the matrix of the tissue became softer and more permeable. There was only a marginal decrease in the equilibrium modulus of the tissue with increasing age and surface degeneration. The permeability of the cartilage matrix was not significantly correlated with age or degeneration. We concluded that the visual or histological appearance of a cartilage specimen may be a poor indicator of its ability to function as the bearing material in the intact joint. A more reliable indicator of the functional properties of a specimen can be obtained either by direct mechanical testing or by biochemical analysis of its composition.

Tensile fatigue of human articular cartilage

The fatigue properties of human articular cartilage were studied by subjecting isolated specimens of cartilage, cut from the superficial layer of more than 30 post-mortem human femoral heads, to repeated applications of tensile stress. A wide variation in fatigue resistance was found between the cartilage from different femoral heads, although all the cartilage appeared to be normal on the basis of Indian ink examination and proteoglycan analysis. The variation in fatigue resistance correlated poorly with collagen and proteoglycan content but significantly with age. It was concluded that the fatigue properties of human articular cartilage decrease with age to such an extent that fatigue failure of the material could occur in life.