ABSTRACT
We examined localization and mRNA expression of HGF, HGFA and c-Met in synovial tissues [ST] in rheumatoid arthritis [RA] in relation to disease activity to characterize its biologic function in RA. Immunohistochemical staining and RT-PCR for HGF, HGFA and c-Met were performed on ST specimens from 34 RA-patients and 20 osteoartheritis [OA] controls. Synovial fluid [SF] samples were taken from all RA and all OA for measuring HGF by ELISA technique. Immunohistochemical staining of RAST revealed that HGFA and c-Met were strongly expressed in fibroblasts, macrophages, endothelial cells and less on synovial lining cells, but HGF was expressed faintly in macrophages and fibroblasts. While, in OAST, HGFA and c-Met were detected in the same cells as RAST but in different distribution, but HGF was localized in vascular endothelial cells. RT-PCR showed HGF, HGFA and c-Met mRNA in all RAST and all OAST. HGF levels in SF samples were higher in RA patients [range 5.6-39.2 ng/ml and mean 26.3 +/- 1.2 ng/ml] than OA controls [range 4.2-37.5 ng/ml and mean 11.2 +/- 2.4 ng/ml], and the differences were statistically significant [P < 0.001]. Non significant correlation between HGF-SF levels and disease activity score [DAS] [P > 0.5]. HGFA, HGF and c-Met mRNA are expressed in ST in RA and OA. Lack of correlation between HGF-SF levels and DAS indicated that HGF played regulatory role in immunopathogenesis of RA