A MONOARTHRITIS MODEL IN RABBITS INDUCED BY REPEATED INTRAARTICULAR INJECTIONS OF LIPOPOLYSACCHARIDE

We attempted to develop a monoarthritis model using repeated intra-art icular injections of high-dose Lipopolysaccharide (LPS). Furthermore, the effect of dexamethasone on this arthritis model by intra-articular administration was studied to examine whether the model can be used t o screen anti-rheumatic drugs in a short time. Arthritis was induced b y one, two or th ree intra-articular injections of LPS (5-50 mu g/join t) at 4-day intervals into the knee joint. The rabbits were sacrificed at 7 days following the last injection of LPS. Three intra-articular injections of LPS at 50 mu g/joint resulted in persistent joint swelli ng. Hyperplasia of synovium with Some discolouration was macroscopical ly observed. Infiltration of mononuclear cells and lymphoid follicles were histologically observed as the synovial lesions. Concerning the a rticular bone/cartilage, trabecular destruction of gastrocnemius sesam oid bone and severe loss of safranin-O staining of articular cartilage were observed. Immunohistochemical analysis revealed that inflammator y cells and lymphoid follicles in the synovial lesions consisted predo minantly of CD4(+) T cells, with few CD8(+) T cells. Treatment with de xamethasone markedly reduced the joint swelling and the articular dest ruction. The results suggest that this arthritis model in rabbits can be utilized to screen anti-rheumatic drugs as a model of rheumatoid ar thritis.