Background
Recurrent implantation failure (RIF) remains a critical and challenging problem in assisted reproductive technology mainly due to impaired decidualization. The endocytic and transcytotic activity in the endometrium are crucial for decidualization. The most representative endocytic gene is the C-terminal Eps15 homology domain-containing 1 (EHD1), but whether EHD1-mediated endocytic function is responsible for embryo implantation during decidualization remains unclear.
Methods
A transcriptomic analysis was performed to evaluate the differentially expressed genes between the fertile control and RIF group. The expression and location of EHD1 in endometrial tissues were further examined by IHC, qRT-PCR and Western blotting. The transduction of an EHD1 recombinant adenovirus into human endometrial stromal cells was performed to investigate relevant decidualization marker genes. Additionally, a microarray analysis following the adenovirus-mediated overexpression of EHD1 was conducted to identify EHD1-related changes in HESCs, and the potential molecular mechanisms were further confirmed through immunofluorescence and coimmunoprecipitation analyses. Findings: An RNA-seq analysis demonstrated that EHD1 expression was significantly higher in the mid-secretory endometrium of the RIF group than in that of the fertile control group. The analysis of the menstrual cycle showed that expression of EHD1 increased in the mid-proliferative phase and showed a gradual decrease in the mid-secretory and decidual phases. Furthermore, EHD1 overexpression impaired decidualization by suppressing the expression of prolactin and insulin-like growth factor binding protein-1 and the formation of the cytoskeleton. The mechanistic analysis revealed the EHD1 regulated LRP5/6 protein function through the endocytic pathway, and subsequently suppressed the Wnt4/β-catenin pathway during decidualization. In addition, a Wnt4 agonist improved an impaired decidualization process. Interpretation: Regulation of the EHD1-Wnt4 pathway might serve as a promising therapeutic strategy for improving endometrial receptivity in RIF women.