IN-SITU HYBRIDIZATION STUDY OF VASCULAR CELL-ADHESION MOLECULE-1 MESSENGER-RNA EXPRESSION IN RHEUMATOID SYNOVIUM

Upregulation of vascular cell adhesion molecule-1 (VCAM-1) has been im plicated in various pathological conditions. In this study, we used in situ hybridization to determine the cell types expressing VCAM-1 mRNA in rheumatoid synovium. Synovial tissues from seven rheumatoid arthri tis (RA) and four osteoarthritis (OA) patients were examined for VCAM- 1 mRNA expression. In situ hybridization as well as immunohistochemica l analysis showed that VCAM-1 expression was mainly localized to the h yperplastic synovial lining cells and to a lesser extent endothelial c ells and synovial fibroblasts in rheumatoid synovium. VCAM-1 expressio n in OA is less prominent. Hyperplastic synovial lining cells expressi ng VCAM-1 were mainly CD13(+), CD14(+), CD33(+) and HLA-DR(+). Togethe r with morphological features, this suggests that they are type A macr ophage-like synovial cells. Our findings indicate that overexpression of VCAM-1 may contribute to the formation of hyperplastic lining layer s in the synovium seen in this disorder. (C) 1995 Academic Press Limit ed