Induction of matrix metalloproteinase-9 and-2 activity in mouse blastocyst by fibronectin-integrin interaction

Fibronectin, a major extracellular matrix, plays an important role in embryo implantation by mediating embryo adhesion and outgrowth. In this work, mouse blastocysts produced pro-matrix metalloproteinase-9, pro-matrix metalloproteinase-2 and 64 ku matrix metalloproteinase-2 when they were co-cultured with fibronectin. In contrast, mouse blastocysts did not produce these proteinases without fibronectin. Focal adhesion kinase is a fundamental molecule of integrin signaling pathway and its antisense oligodeoxynucleiotide inhibited blastocyst matrix metalloproteinases expression induced by fibronectin. The results indicated that fibronectin triggered matrix metalloproteinase-9 and -2 expression in mouse blastocyst through its integrin receptors and subsequent signaling pathway, which enhanced the synchronization of blastocyst invasiveness and uterine receptivity and ensured the accuracy of events relative to implantation in timing and spatiality.

Regulation of mouse blastocyst adhesion,outgrowth and matrix metalloproteinase-2 by focal adhesion kinase

The interaction of extracellular matrix-integrin markedly influences the adhesion, outgrowth, differentiation and expression of serine proteinases by the blastocyst, so it is regarded as a vital factor in blastocyst implantation. Al- though the mechanism of extracellular interactions between extracellular matrix and integrins has been well elucidated, the roles of the signaling molecules in the extracellular ma- trix-integrin signal transduction pathway in blastocyst im- plantation are unknown. This limits the understanding of blastocyst implantation and ECM-integrin signal transduc- tion pathway. In the present study, in vitro blastocyst culture and indirect immunocytochemistry, matrix metallopro- teinases (MMPs) zymography and antisense oligodeoxynu- cleotide (ODN) were used to investigate the expression of a fundamental molecule of integrin-dependent signal trans- duction pathways, focal adhesion kinase (FAK), in mouse blastocysts and its influence on mouse blastocyst adhesion, outgrowth and MMP-2. The results showed that mouse blas- tocysts expressed FAK. FAK protein was clustered in the peripheral migrating trophoblast cells and dispersed in the central area of blastocyst outgrowth. Fibronectin triggered pro-MMP-2 and 64 kD MMP-2 activities. The antisense ODN to FAK attenuated pro-MMP-2 and 64 kD MMP-2 activities which decreased abruptly and tended to disappear with increasing concentrations of the antisense ODN. Both mouse blastocyst adhesion and outgrowth on fibronectin were also influenced by the antisense ODN. Up to 20 mg/mL of the antisense ODN concentration, the adhesion and out- growth rates were decreased in a dose-dependent manner. The results indicated that FAK influenced mouse blastocyst adhesion, outgrowth and MMP-2 activity by intracellular signal transduction. In other words, FAK regulates mouse implantation in terms of blastocyst adhesive and invasive abilities.