Production of matrix metalloproteinase 3 (stromelysin) by cultured ovine endometrial cells.

Ovine endometrial cells (stromal plus epithelial) in primary culture release matrix metalloproteinase 3 (stromelysin, MMP-3), the enzyme that degrades various extracellular components including the basement membrane components collagen IV and laminin. The enzyme was detected in tissue culture medium by specific enzyme assay. A low level of MMP-3 activity was released from the cells (0.12 +/- 0.02 unit per 10(6) cells per 48 h; 1 unit degrades 1 microgram of reduced, carboxymethylated transferrin min-1 at 37 degrees C), but following stimulation by phorbol myristate acetate (PMA) a mean 4.4-fold increase in MMP-3 production was observed (to 0.53 +/- 0.13 unit per 10(6) cells per 48 h). The enzyme was released primarily in the form of its proenzyme, which could be activated in vitro by (4-aminophenyl)mercuric acetate (APMA). Stimulation of enzyme release from cells by PMA was not seen before 24 h and required PMA at a dose of 10 nM or higher. This finding was substantiated by Western blot analysis. Immunocytochemistry of cells that had been treated with PMA for 48 h, and with the ionophore, monensin, for 4 h, confirmed the potential of the endometrial cells to produce stromelysin. The release of MMP-3 from ovine endometrial cells suggests that this enzyme may have a role in assisting the passage of syncytial processes through the basement membrane during the process of implantation.