Objective: To study the expression of collagenase 3 (matrix metalloproteinase 13 [MMP-13]) and collagenase 1 (MMP-1) in synovial fibroblasts from patients with rheumatoid arthritis (RA) when cultured within 3-dimensional collagen gels or coimplanted with normal cartilage in immunodeficient NOD/SCID mice.
Methods: Messenger RNA (mRNA) and protein expression of collagenase 3 and collagenase 1 were characterized in synovial and skin fibroblasts by Northern blot and Western blot analysis. The mRNA expression of both collagenases in cell-cartilage implants in NOD/SCID mice was investigated by in situ hybridization in combination with immunohistochemistry of human fibroblasts.
Results: Synovial fibroblasts coimplanted with normal cartilage in NOD/SCID mice deeply invaded adjacent cartilage tissue. In this in vivo system of cartilage destruction, collagenase 3 mRNA was induced in synovial fibroblasts at sites of cartilage erosion, while the expression of collagenase 1 mRNA could not be detected. Culture of synovial fibroblasts within 3-dimensional collagen gels was associated with a marked increase in collagenase 3 mRNA expression and proenzyme production. This stimulatory effect was 1 order of magnitude higher in comparison with a 2-4-fold increase upon treatment with interleukin-1beta or tumor necrosis factor a. In contrast, mRNA expression and proenzyme production of collagenase 1 were increased strongly, and to a similar extent, either by contact with 3-dimensional collagen or by proinflammatory cytokines.
Conclusion: The expression of collagenase 3, in contrast to that of collagenase 1, is preferentially stimulated in synovial fibroblasts by 3-dimensional collagen rather than by proinflammatory cytokines. The induction of collagenase 3 by cell-matrix interactions represents a potential mechanism contributing to the invasive phenotype of synovial fibroblasts at sites of synovial invasion into cartilage in RA.