In vitro,
membrane-type matrix metalloproteinases (MT-
MMP) are known to activate the
zymogen of MMP-2 (proMMP-2,
progelatinase A), which is one of the key
MMP in joint destruction in
rheumatoid arthritis. In the present study, we examined the production and activation of
proMMP-2, and the expression of
MT1-MMP,
MT2-MMP, and
MT3-MMP, their correlation with
proMMP-2 activation, and their localization in rheumatoid synovial tissue. Using sandwich
enzyme immunoassay and
gelatin zymography techniques,
proMMP-2 production levels and activation ratios were found to be significantly higher in rheumatoid synovium compared with normal synovium (p < 0.01). Quantitative RT-PCR analyses demonstrated that
MT1-MMP and
MT3-MMP were expressed in all rheumatoid synovial tissue (30 of 30 cases), but that the mean expression level of
MT1-MMP was approximately 11-fold higher than
MT3-MMP. Significant correlation was found between the
mRNA expression level of
MT1-MMP and the activation ratio of
proMMP-2 (p < 0.01). In situ hybridization indicated that the hyperplastic lining cells of rheumatoid synovium expressed
MT1-MMP. Immunohistochemistry demonstrated that
MT1-MMP was co-localized with MMP-2 and with a
tissue inhibitor of metalloproteinase-2, and was mainly located in the rheumatoid synovial lining cells. In situ zymography of rheumatoid synovium showed gelatinolytic activity, predominantly in the lining cell layer. This activity was blocked when incubated with BB94, a specific
MMP inhibitor. These results demonstrate that
MT1-MMP plays an important role in the activation of
proMMP-2 in the rheumatoid synovial lining cell layer, and suggest that its activity may be involved in the cartilage destruction of
rheumatoid arthritis.