Immunolqcaljzation of fbroblast growth factor receptor (FGFR)-1 and 2 in joint tissue from rats with adjuvant arthritis

Our previous studies have demonstrated an altered distribution of basic fibroblast growth factor (bFGF) in synovium from patients with rheumatoid arthritis and rats with adjuvant arthritis. To further elucidate the roles of bFGF in articular inflammation, we examined the distribution patterns of two high affinity receptors for bFGF, FGFR-1 and -2, in the arthritic joints of rats using immunohistochemistry. In normal joints, selective staining for both FGFRs was found to be mainly associated with lining synoviocytes and chondrocytes. In arthritic joint tissues, increased staining for both FGFRs was observed in lining and sublining synoviocytes. While staining for FGFR-2 was found only in the cytoplasm of fibroblast-like synoviocytes that exhibited hypertrophy and hyperplasia. staining for FGFR-1 was mainly seen in their nucleus. Paradoxically, increased staining for these FGFRs was also observed in areas with active osteogenesis. The overall staining patterns of these FGFRs is comparable to that of bFGF reported. These findings further implicate bFGF in the destructive arthropathy and suggest that the invasive growth of inflamed synovium may result from an exaggerated response to bFGF due to increased levels of FGFR-1 and -2.