Expression and function of matrix metalloproteinases in development.

Extracellular matrix (ECM) remodeling accompanies cell migration, cell-cell interactions, embryo expansion, uterine implantation and tissue invasion during mammalian embryogenesis. We have found that mouse embryos express mRNA transcripts for collagenase, stromelysin and the tissue inhibitor of metalloproteinases (TIMP) and secrete functional ECM-degrading metalloproteinases, including collagenase and stromelysin. These metalloproteinases are inhibitable by TIMP and are regulated during peri-implantation development and endoderm differentiation. The involvement of a controlled proteolytic reaction, dependent on metalloproteinases, during the implantation of mouse embryos is suggested by the secretion of proteinases by trophoblast during its invasive phase and by the reciprocal expression of TIMP in the maternal deciduum. Exogenous TIMP affects the migration of parietal endoderm cells during blastocyst outgrowth in vitro. Taken together, these data suggest that metalloproteinases function in cell-ECM interactions during mammalian development.