92-KDA TYPE-IV COLLAGENASE AND TIMP-3, BUT NOT 72-KDA TYPE-IV COLLAGENASE OR TIMP-1 OR TIMP-2, ARE HIGHLY EXPRESSED DURING MOUSE EMBRYO IMPLANTATION

Expression of 72 kDa and 92 kDa type IV collagenases and the metallopr oteinase inhibitors TIMPs 1, 2, and 3 was studied by in situ hybridiza tion in implanting mouse embryos of days 5.5 to 7.5. The 92 kDa type I V collagenase was strongly expressed in invading trophoblasts, signals above background not being observed in the embryonic proper or placen tal tissue. In contrast, signals above background were not seen for th e 72 kDa enzyme in any cells of the implantation region, including tro phoblasts and stromal cells of the decidual tissue. Only cells in the mucosal stroma outside the decidual region displayed some expression. TIMP-3 was intensily expressed in maternal cells in the area surroundi ng the invading embryonic tissue. No expression was observed for TIMP- 1 or TIMP-2 in the embryo proper, trophoblasts, or the area of the ute rine decidual reaction. Weak signals appeared for TIMP-1 only in the c ircular layer of myometrial smooth muscle and in some uterine stroma c ells distant from the site of embryo implantation. The results suggest a central role for 92 kDa type IV collagenase and TIMP-3 in the extra cellular proteolysis associated with implantation of the early embryo. (C) 1995 Wiley-Liss, Inc.