The significance of membrane type 1 metalloproteinase in structural involution of human corpora lutea.

The expression of membrane type 1 (MT1) matrix metalloproteinase (MMP), MMP-2, and tissue inhibitors of MMP-1 and -2 during structural involution of the human corpus luteum was examined using immunohistochemistry, Northern blotting, Western blotting, gelatin zymography and in-situ hybridization techniques. The corpora lutea of 20 patients were investigated at the time of total hysterectomy and were obtained from five patients each in the early, mid- and late luteal phases and during gestation. Immunohistochemistry for MT1-MMP in corpus luteum showed that the protein appeared in granulosa lutein cells in the late luteal phase. Both the expression of MT1-MMP mRNA and the amount of the protein increased in the late luteal phase. In-situ hybridization showed that MT1-MMP mRNA was localized mainly in the cytoplasm of granulosa lutein cells. These results suggest that increased expression of MT1-MMP may be a major factor in remodelling of the human corpus luteum during structural luteolysis.