Regulators of Extracellular Matrix Degradation by Mouse Embryos1

Embryo implantation in humans and rodents is a highly in-vasive yet tightly controlled process involving extracellular ma-trix (ECM) degradation. Matrix metalloproteinase 9 (MMP-9) has been implicated as the major facilitator of this ECM degradation. MMP-9 is expressed by the embryo’s trophoblast cells, whereas tissue inhibitor of metalloproteinases 3 (TIMP-3) is expressed by the maternal uterine cells immediately adjacent to the tropho-blast. We examined the functional roles of MMP-9 and TIMP-3 during in vitro ECM degradation by mouse embryos. Blastocysts were treated with either MMP-9 antisense or sense oligonucle-otides and incubated on an ECM gel. The extent of ECM deg-radation exhibited by the blastocysts due to proteinase secretion was quantified. Embryos exposed to MMP-9 antisense oligonu-cleotides exhibited reduced ECM-degrading activity as com-pared with controls, and this reduced activity was correlated with the level of MMP-9 secreted by the embryos. The functional role of TIMP-3 was then examined by incubating blastocysts on an ECM gel that had been impregnated with various amounts of TIMP-3. In a dose-dependent manner, increases in TIMP-3 re-sulted in a reduction in ECM degradation and were correlated with diminished MMP-9 activity. These results provide important functional evidence that in vitro ECM degradation is regulated by embryo-derived MMP-9 and ECM-derived TIMP-3. implantation/early development, trophoblas