To determine whether apoptosis occurs in the proliferative synovial tissue and cells from patients with rheumatoid arthritis (RA).
In situ hybridization was carried out by using labeled RNA probes of fas, fasL, and bcl-2 synthesized by in vitro transcription. Apoptosis was examined by DNA electrophoresis and flow cytometry.
fas mRNAs were expressed in 6 of 7 patients with RA. bcl-2 mRNAs were positive in 5 of 7 patients with RA. fasL mRNAs were not detectable in all the patients. bcl-2 mRNAs were always coexpressed with fas in RA synovial lining cells. The positive rates of fas and bcl-2 expression in RA synovial tissues were significantly higher than those of patients with osteoarthritis (OA) and normal synovial tissues (P < 0.05). Immunochemistry staining showed that Fas and Bcl-2 proteins were expressed in the synovial lining cells. Nucleic DNA extracted from the synovial tissues of 6 patients with RA, 4 patients with OA and 2 normal controls. Agarose gel electrophoresis demonstrated that DNA ladders occurred in only one OA synovial tissue. The spontaneous apoptosis in cultured synoviocytes from patients with RA and OA was lower as analyzed by immunofluorescence staining and flow cytometry.
The phenomena of apoptosis in RA synoviocytes was not significant and overexpression of bcl-2 perhaps inhibited apoptosis in these cells, leading to hyperplasia of RA synoviocytes.