No description available.

No description available.

No description available.

No description available.

Changes in the structural organization of cartilage and synovial tissue, or in the macromolecules produced by their cells, alter the properties of the tissues. Elucidation of the changes under controlled experimental conditions could make a significant contribution to the understanding of the pathogenesis of arthritis. To this end a model system has been developed to study proteoglycan and collagen regeneration in porcine articular cartilage and synovial tissue: partially depleted of matrix by exogenous enzyme(s), the tissues were maintained in organ culture, the medium consisting of Dulbecco's modification of Eagle's medium and 15% rabbit serum, and the responses of the chondrocytes and synoviocytes studied biochemically and histologically. Cleavage of proteoglycan core protein in cartilage explants by trypsin, equivalent to the disruption occurring in joint inflammation, induced glycosaminoglycan synthesis. The chondrocytes, particularly of the mid and hypertrophic zones, acquiring a basophilic territorial matrix and eventually an interterritorial matrix, which replaced the ex vivo material. Further damage to collagen by bacterial collagenase induced collagen synthesis, and enhanced glycosaminoglycan synthesis, but hyaluronic acid disruption proved partially inhibitory to recovery, the interterritorial matrix being less basophilic than comparable trypsinized explants. ³⁵SO₄ uptake by depleted explants showed a similar but sustained rate of glycosaminoglycan synthesis compared with untreated explants. The effects of corticosteroids, currently used for the temporary palliation of joint inflammation, on the regeneration processes were studied. The hydrolytic potential of the cultures and the frequency of medium changes had a profound effect on biologically active cortisol levels when cortisol succinate was present. Lower than physiological levels of cortisol (≤2.76 x 10^-7M) promoted glycosaminoglycan synthesis in all disrupted explants except those with cleaved hyaluronic acid chains. During the later stages of culture, in the presence of cortisol, (≤2.76 x 10-7M), the interterritorial glycosaminoglycan concentration increased. Whether collagen fibres were disrupted or not, collagen synthesis was evident, although with pharmacological concentrations of steroid (≤2.76 x 10^-6 M) all synthetic processes were increasingly inhibited. Exogenous trypsin induced extensive resorption of collagen fibres in minced synovial tissue, probably by activation of synovial collagenase. The destruction was partially reduced with trypsin inhibitor or cortisol. In areas of degradation macrophage-like cells accumulated but with early removal of trypsin, despite loss of collagen, fibroblast-like cells accumulated at the base of the explants with synthesized pericellular collagen evident. Collagen release into the medium was measured by an improved hydroxyproline assay designed to reduce interference from serum proteins. Although physiological doses of cortisol (≤2.76 x 10-7 M) enhanced collagen synthesis by, and the development of, the fibroblastic cells, extensive tissue repair was not observed, merely the formation of a cell population in the Millipore membrane. This model of tissue regeneration, remodelling and repair leads to the conclusion that within the arthritic joint the chondrocyte has the potential to rapidly attempt to repair damaged matrix, the extent of synthesis being proportional to the extent and type of matrix disruption. The chondrocyte responds by synthesizing glycosaminoglycans, that aggregate within the matrix, and collagen, with cortisol, at below physiological concentrations, enhancing this regeneration. Synovial tissue did not recover from disruption although the synoviocytes, on reversion to fibroblast-like cells, accumulated new collagen.

No description available.

No description available.

No description available.

In this study an <i>in vitro</i> model was used to simulate joint trauma by subjecting explants of articular cartilage to a single impact load using a specially designed drop-tower loading machine for which two different loading attachments were developed. The aim was to compare the biophysical effects of impact loading on bovine and human cartilage. The proteolytic lysomal enzyme, cathepsin B and the proinflammatory mediators, prostaglandin E₂ (PGE₂) and nitric oxide (NO) have been implicated in the degradation of cartilage following trauma. This study aimed to investigate the role of these degradatory mediators. Human cartilage was found to be less damaged than bovine after impact and the type of loading attachment affected the nature of the damage observed. Following an impact load on human cartilage explants, the levels of glycosaminoglycans (GAGs), a measure of cartilage breakdown, in the culture medium and the percentage of apoptotic chondrocytes were significantly increased. The levels of pro-cathepsin B were significantly increased in the culture medium compared to unloaded controls. Addition of human cystatin C and the synthetic cathepsin B inhibitor, CA-074Me, reduced this release. However these inhibitors had no effect on the release of GAGs or the levels of apoptosis following impact. A marked increase in PGE₂ and NO was measured in the medium following an impact load, which was reduced by the selective cyclooxygenase-2 (COX-2) inhibitor, celecoxib, and the non-selective inhibitor, indomethacin. These inhibitors reduced chondrocyte apoptosis but no change was observed in the release of GAGs from the explants. This <i>in vitro</i> study indicates that cell viability and matrix degeneration are separately regulated and that it is unlikely that cathepsin B or COX-2 inhibition alone would slow down or prevent the development of secondary osteoarthritis.

Articular cartilage is a tough and resilient tissue lining the ends of articulating bones. It provides a smooth surface for joint locomotion as well as transmitting the force between bones. The main components of articular cartilage are collagen (20% w/w), proteoglycans (10% w/w) and water (70% w/w). The interactions between these three give the tissue its special characteristics. Water as a molecule is often forgotten when considering the mechanical properties of articular cartilage. This thesis aims to increase our knowledge of the role of water molecules in the load bearing mechanisms of the tissue. It will also investigate the material properties of cartilage as hydrogel. Different rates of loading (impact and slow compression) were used on partially dehydrated articular cartilage (bovine and human). The impact was also recorded using high-speed video cameras. Values of modulus of elasticity, Poisson's ratio, energetic coefficient of restitution were measured together with viscoelastic spectra, by Fourier transformation, and Dynamic Mechanical Analysis. Differential scanning calorimetry (DSC) was also performed on bovine and human articular cartilage, as well as transmission electron microscopy where different freeze substitution solvents were used. The stiffness of the tissue increased and the energetic coefficient of restitution decreased with decreasing water content. Cartilage explants had a smaller volume at the point of full strain than at the start of the impact and this volume loss was associated with the level of hydration of the tissue. Poisson's ratio was not associated with the water content of the tissue. The DSC showed that the water existed in the tissue in different environments, as the exothermic traces showed melting patterns with multiple peaks. Transmission electron micrographs revealed an area surrounding the collagen molecules that could be associated water. These results indicate that water might exist in a structured way in the tissue, and that it is important for the mechanical capabilities of the tissue.