To clarify the histological and biological features of tenosynovitis accompanying rheumatoid arthritis (RA).
Synovial tissue was obtained from the wrist joint and extensor tendon of the digits of six RA patients and the sections were examined by haematoxylin and eosin staining and immunohistochemical analysis. RA tenosynovitis exhibited the typical histological features of RA joint synovitis, including hyperplasia of the synovial lining and infiltration of leucocytes, largely CD4+ T cells and CD68+ macrophages. Notably, there was a significant correlation in the number of CD4+ T cells and CD68+ macrophages between the tenosynovium and joint synovium in each individual. Real-time reverse transcriptase-polymerase chain reaction analysis revealed similar mRNA expression patterns of various inflammatory mediators in tenosynovitis and joint synovitis. It was also observed that synovial fibroblasts isolated from the tenosynovium behaved in a manner similar to those isolated from the joint synovium with regard to proliferation and the production of inflammatory mediators.
The histopathological features of RA tenosynovitis were indistinguishable from those of joint synovitis. Therefore, it is suggested that the ongoing inflammation is driven by similar mechanisms in the tenosynovium and joint synovium and that RA is probably a tissue-specific disease which targets systemic synovial tissues.