Equine carpal articular cartilage fibronectin distribution associated with training, joint location and cartilage deterioration.

Processes involved in equine carpal osteochondral injury have not been established. In other species, fibronectin appears important in chondrocyte-matrix interactions, and levels are increased in osteoarthritis. This investigation aimed to (a) describe fibronectin immunoreactivity in the middle carpal joint of 2-year-old Thoroughbreds, (b) determine topographical variations, (c) compare strenuously trained (Group 1) or gently exercised horses (Group 2) and (d) describe sites with early osteoarthritis. Group 1 (n = 6) underwent a 19 week high intensity treadmill training programme. Group 2 (n = 6) underwent 40 min walking until euthanasia. Dorsal and palmar sites on radial, intermediate and third carpal articular surfaces were prepared. Immunohistochemistry was performed using a biotin-streptavidin/peroxidase method. Cross-reactivity of rabbit antihuman fibronectin antiserum with equine fibronectin was confirmed using Western blotting. Results showed: (a) fibronectin was present primarily in pericellular and interterritorial matrix locations, (b) dorsal sites had zonal immunoreactivity compared to palmar sites, (c) Group 1 dorsal radial carpal cartilage had increased superficial staining compared to Group 2 and (d) fibrillated cartilage showed increased intracellular and local matrical immunoreactivity (superficial zone). These findings suggest topographical and exercise-related variations in fibronectin distribution, and indicate equine fibronectin is localised at sites of cartilage degeneration and released into the matrix by chondrocytes in the local area.

Expression of cytokine mRNA in lentivirus-induced arthritis.

Infection of goats with the lentivirus caprine arthritis encephalitis virus (CAEV) leads to persistent infection and development of chronic arthritis. We analyzed the expression of cytokines and viral RNA in the joints of goats at early time points after experimental infection with CAEV and in those of animals suffering from chronic arthritis as a result of natural infection. In situ hybridization experiments showed that the pattern of cytokine expression in caprine arthritis was similar to that found in rheumatoid arthritis (RA), with a few cells expressing the lymphocyte-derived cytokines interferon (IFN)-gamma and interleukin (IL)-2 and rather more cells expressing monocyte chemoattractant protein (MCP)-1, IL-6, and tumor necrosis factor (TNF)-alpha. IFN-gamma mRNA expression in experimentally infected joints peaked at day 12 and was mostly detected in areas containing viral RNA. At later time points, no IFN-gamma- or virus-expressing cells were found in inflamed joints but both were again detected in goats with severe arthritis. Interestingly, at the clinical stage of arthritis reflecting the chronic stage of infection, the inflammatory lesion was found to be immunologically compartmentalized. Humoral immune responses and cell-mediated immune responses appeared to concurrently occur in distinct areas of the synovial membrane.

Immunogenic potential of carpal implants.

This study investigated whether a cellular or a humoral-mediated immunologic response to silicone carpal prostheses could be detected in animals previously sensitized to silicone. Silicone carpal prostheses were emulsified in Freund's complete adjuvant (FCA). This emulsion was injected into guinea pigs weekly for 6 weeks. Controls received only FCA. Four weeks later a carpal prosthesis was implanted. Histology showed the implanted prosthesis encapsulated by fibrous tissue in sensitized animals, with a mononuclear infiltrate within the fibrous periprosthetic capsule consistent with a cellular immune response. Skin testing of the sensitized animals showed a true correlate response to the silicone antigen challenge, whereas no response was observed in the control group. The passive cutaneous anaphylaxis reaction in sensitized animals was positive, emphasizing that the antigen-antibody response was passively transferred. Tissue adjacent to the silicone implant in sensitized animals revealed an IgG deposition around the silicone particles by the fluorescent antibody technique. Control animals showed none of these reactions. These results indicate that microparticulate matter from carpal implants can possibly initiate both a cellular immunologic response and the production of a circulating antibody.