Immunolocalization of basic fibroblast growth factor and platelet-derived growth factor-A during adjuvant arthritis in the Lewis rat.

A prerequisite in defining the role of a growth factor in a disease is knowledge of its expression kinetics during the natural course of the disease. We, therefore, used immunohistochemical and immunoblot analyses to examine tissue distribution of basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF-A) during the development of destructive arthropathy in the rat adjuvant arthritis model. In normal joints, bFGF was primarily localized in endothelial cells. In inflamed joints, increased staining for bFGF was found in the invading panni, hyperplastic synovium, and thickened periosteum where bFGF was also co-localized with two cell proliferation markers. Staining for bFGF began to increase at the onset of arthritis (days 11 to 13), reached peak level on days 17 to 24, and gradually declined afterward. In contrast, PDGF-A staining did not change until day 17 and the increased staining was restricted to areas of newly formed bone. The district temporal and spatial distribution pattern of these two growth factors during the destructive arthropathy strongly suggests that they play different roles during arthritis. Although PDGF-A seems to be exclusively related to osteogenesis, bFGF may have a more extensive impact on synovial proliferation and bone destruction as well as bone formation.