Objective: 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).
Methods: 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.
Results: 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.
Conclusion: 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.