To study the localization and cell type-specific expression of collagenase 3 messenger RNA (mRNA) in the synovial membrane, its regulation in primary synovial fibroblasts, and the correlation with systemic markers of inflammation and radiographic damage in rheumatoid arthritis (RA).
The expression of collagenase 3 mRNA was characterized by Northern blot analysis, reverse transcriptase-polymerase chain reaction, and in situ hybridization. Immunohistochemical detection of cell type-specific antigens was used in combination with in situ hybridization of collagenase 3 mRNA to characterize the cellular origin of collagenase 3 mRNA expression.
Collagenase 3 mRNA was detected in synovial membrane specimens of 21 of 36 RA patients (58%) and correlated with an increase in erythrocyte sedimentation rate (P<0.05) and C-reactive protein levels (P<0.005). Collagenase 3 mRNA was localized in fibroblast-like cells of the lining and sublining layers, and at the synovial membrane-cartilage interface. Four of 10 primary synovial fibroblast cell cultures showed basal expression of collagenase 3 mRNA, which was stimulated 2-4-fold upon interleukin-1beta or tumor necrosis factor alpha treatment and, in contrast to interstitial collagenase mRNA, 5-10-fold by increasing the intracellular level of cAMP. The stimulation by cAMP analogs was completely abolished by protein kinase A inhibitors.
Some RA patients show collagenase 3 mRNA expression in the synovial membrane, which correlates with elevated levels of systemic markers of inflammation in these patients. In synovial fibroblasts, the expression of collagenase 3 and interstitial collagenase mRNA is differentially regulated by distinct protein kinase signal transduction pathways.