Blastocyst derived signal facilitate the embryo implantation via protein degradation via activating lysosome in the uterine epithelia [RNA-Seq: Epithelium_Igf1r_WT_KO]
The mammalian endometrium is covered by the luminal epithelium (Le), which directly interacts with the blastocyst and plays an important role in the establishment of reciprocal crosstalk between the embryo and receptive uterus during implantation. However, the effect of the blastocyst on uterine receptivity is far from well understood. Through transcriptomic profiling of the uterine Le isolated by laser capture microdissection, it was demonstrated that global gene expression changes occurred in Le between pseudopregnant mice without embryos and pregnant mice with embryos. Some differentially expressed genes, including upregulated Areg, Ihh, Lifr and downregulated Msx1, Pgr, Gata2, have been reported to regulate the establishment of uterine receptivity. Besides, we found that blastocysts induced an increase in both the number and acidification of lysosome, consistent with enhanced lysosomal hydrolase activity in uterine Le. Further exploration uncovered that blastocyst-derived IGF2 was involved into the activation of epithelial STAT3 to induce lysosomal hydrolase expression, and inhibition of lysosomal function derails normal uterine receptivity and embryo implantation. Finally, based on the proteomic data of both epithelia and the separated lysosome, it was revealed that CLDN1 and MUC1, two well-known downregulated molecules for successful implantation, are degraded by epithelial lysosome. In brief, our data demonstrated that blastocysts induced normal epithelium differentiation with lysosome activation to promote the establishment of uterine receptivity for embryo implantation. Overall design: Gene expression of epithelium in WT and Igf1rKO pregnant day 4 uteri