IN-SITU HYBRIDIZATION OF STROMELYSIN MESSENGER-RNA IN THE SYNOVIAL BIOPSIES FROM RHEUMATOID-ARTHRITIS

We examined the expression of stromelysin mRNA (SL mRNA) in synovial b iopsy specimens from 12 cases of rheumatoid arthritis (RA) and 2 cases of osteoarthritis (OA) using in situ hybridization. The study demonst rated that positive cells with high levels of SL mRNA mere mostly (85% ) found in the synovial lining layer. The positive cells mere abundant in the synovium of RE which presented well developed lymphoid follicl es with massive inflammatory cells. On the other hand, the synovium of OA contained no positive cells for SL mRNA. In addition, low yet posi tive levels of SL mRNA were detected in the endothelial cells and vasc ular myocytes, and interstitial cells in the deeper layer of the synov ium. Karyometric studies showed that cells positive for SL mRNA had si gnificantly larger and more spherical nuclei than weakly positive or n egative cells. The SL mRNA positive cells did not demonstrate any immu noreactivity to markers of bone marrow origin, such as Leu M1, Leukocy te Common Antigen (LCA) and lysozyme antigen. Electron microscopy of a case with many SL mRNA positive cells showed that most had well devel oped rough endoplasmic reticulum and numerous processes on the cell su rface, and some had also well developed rough endoplasmic reticulum bu t without processes indicating that they may be AB and/or B synoviocyt es.