• The effects of erythropoietin in an in vitro model of cartilage degradation

      Baig, Somara (University of Bedfordshire, 2003-06)
      Cartilage is an aneural and avascular tissue, which is composed of chondrocytes, embedded within an extracellular matrix. Cartilage degradation, joint inflammation and bone destruction are the prominent features of rheumatoid arthritis, which is a persistent autoimmune disorder. Cartilage matrix is made up of collagen to provide tensile strength with aggregated proteoglycans to facilitate hydration. The loss of cartilage proteoglycans is among one of the early events in cartilage degradation associated with arthritic joint pathology. The pro-inflammatory cytokines such as Tumour Necrosis Factor alpha (TNF-α) and Interleukin-1 beta (IL-lβ) have been shown to increase the loss of proteoglycans from cartilage and to modulate the production of nitric oxide (NO). NO has been associated with cartilage degradation. TNF-α and IL-lβ have also been reported to inhibit erythropoiesis thereby leading to the development of anaemia. Human recombinant erythropoietin (rHuEPO) is administered to treat anaemia of chronic disease, which is a well-known complication of chronic rheumatoid arthritis (RA). However, the effect of EPO on cartilage metabolism in RA is yet unknown. The aim of current study was to investigate the effects of EPO on in vitro models of RA, which were developed with increasing order of complexity, with respect to the production of NO and release of proteoglycans. The production of NO was determined indirectly by measuring nitrite production, via Greiss reaction. The loss of cartilage proteoglycans was quantified by measuring the release of glycosaminoglycans (GAGs), using GAGs assay. Each system was found to respond to IL-1β treatment. Thus, IL-1β was maintained as a positive control stimulus in these investigations. Swiss 3 T3 fibroblast monolayer was utilised to model the response of rheumatoid synovial fibroblasts in pannus tissue of RA joint. An in vitro model of cartilage resorption was established using porcine cartilage explants. This model was then modified by incorporating Swiss 3 T3 fibroblasts mono layers with explants. These studies reveal that that EPO (25JµU/ml) whether alone or in the presence of IL-1β is a pro-inflammatory stimulus of cartilage breakdown. There was no significant difference in the IL-l and EPO-mediated GAGs release and nitrite production by both explant and co-culture models, which suggests that EPO may be as potent stimulus as IL-l with regard to cartilage breakdown in these models of RA. The current investigation concludes that EPO can directly influence cartilage degradation and may potentiate joint inflammation in RA. Therefore, findings from this study suggest that clinical administration of EPO to treat anaemia and its illegal usage by athletes may lead to development of arthritis in later life.