The presence of blastocyst within the uteri facilitates lumenal epithelium transformation for implantation via upregulating lysosome proteostasis activity

Abstract

ABSTRACT The mammalian endometrium is covered by the lumenal 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 differentiation during the window of receptivity is far from well understood. Through transcriptomic profiling of the uterine Le isolated by laser capture microdissection (LCM), 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 (amphiregulin), Ihh (Indian hedgehog), Lifr (leukemia inhibitory factor receptor) and downregulated Msx1 (msh homeobox 1), Pgr (progesterone receptor), and Gata2 (GATA binding protein 2) in pregnant mice, 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 both uterine receptive maker gene expressions and embryo implantation. Finally, based on the proteomic data of both epithelia and the separated lysosome, it was revealed that CLDN1 (claudin 1) and MUC1 (mucin 1, transmembrane), 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 uterine epithelial differentiation for embryo implantation. Abbreviations ACTB: actin beta; AREG: amphiregulin; ATP6V0A4: ATPase, H+ transporting, lysosomal V0 subunit A4; Baf A1: bafilomycin A1; BSA: bovine serum albumin; CLDN1: claudin 1; CTSB: cathepsin B; DEGs: differentially expressed genes; E2: 17β-estradiol; ESR: estrogen receptor; GATA2: GATA binding protein 2; GLA: galactosidase, alpha; GO: gene ontology; HBEGF: heparin-binding EGF-like growth factor; IGF1R: insulin-like growth factor 1 receptor; Ihh: Indian hedgehog; ISH: in situ hybridization; LAMP1: lysosomal-associated membrane protein 1; LCM: laser capture microdissection; Le: lumenal epithelium; LGMN: legumain; LIF: leukemia inhibitory factor; LIFR: LIF receptor alpha; MSX1: msh homeobox 1; MUC1: mucin 1, transmembrane; P4: progesterone; PBS: phosphate-buffered saline; PCA: principal component analysis; PPT1: palmitoyl-protein thioesterase 1; PGR: progesterone receptor; PSP: pseudopregnancy; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; qPCR: quantitative real-time polymerase chain reaction; SP: pregnancy; TFEB: transcription factor EB.