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The damaged endometrium and the formation of fibrosis are key barriers to pregnancy and further lead to infertility. However, how to promote endometrium repair is always a challenge. Here, a bioactive injectable and self‐healing hydrogel is developed by physically combination of thiolated polyethylene (PEG), Cu2+ and cell‐free fat extract (CEFFE, CF) for endometrial regeneration and fertility. By inheriting the advantages of various active proteins contained in CEFFE, it could induce the overall repair of endometrial microenvironment for intrauterine adhesion (IUA). In vitro, CF@Cu‐PEG reduces endometrial cell apoptosis by more than 50%, and increases angiogenesis by 92.8%. In the IUA mouse, injection of CF@Cu‐PEG significantly reduces the rate of uterine hydrometra and prevents the formation of endometrial fibrosis. Remarkably, CF@Cu‐PEG contributes to the repair of endometrial microstructure, especially increases the number of endometrial pinopodes, significantly improves endometrial receptivity, and increases the pregnancy rate of IUA mice from 7.14% to 66.67%. In summary, through the physically combination of CEFFE and Cu‐PEG, the construction of loaded bioactive injectable hydrogel not only inhibits the IUA, but also induces the self‐repair of endometrial cells in situ and improves fertility, providing a new strategy for IUA repair in clinical application.

BackgroundThe precise pathogenesis of poor endometrial receptivity in recurrent implantation failure (RIF) still remains unclear. This study aims to explore the effects of different CD44 isoforms in the mid-secretory phase endometrium on endometrial receptivity in women with RIF.MethodsMid-secretory phase endometrial tissue samples were obtained from two groups of women who had undergone IVF: a) 24 patients with RIF, b) 18 patients with infertility due to tubal obstruction, who had achieved a successful clinical pregnancy after the first embryo transfer in IVF (control group). Identification of differentially expressed CD44 isoforms in endometrial tissues was assessed with immunohistochemistry, qPCR and western blotting. Effects of CD44v3 overexpression and knockdown on proliferation and decidualization of Immortalized human endometrial stromal cells (T-HESCs) and primary HESCs were investigated by qPCR and Western blot. A heterologous co-culture system of embryo implantation was constructed to mimics the process of trophoblast invasion during implantation.ResultsCD44v3 was significantly higher expressed in mid-secretory phase of endometrial stromal cells than proliferation phase, but was notably lower in RIF patients. The expression of decidualization markers, prolactin (PRL) and insulin like growth factor binding protein-1 (IGFBP1), was notably decreased following CD44v3 knockdown, whereas the expression levels of both PRL and IGFBP1 increased after CD44v3 overexpression in HESCs. Furthermore, the CD44v3-knockdown HESCs displayed a significantly deficiency in supporting trophoblast outgrowth through a co-culture system of embryo implantation; however, CD44v3 overexpression in HESCs promoted trophoblast outgrowth.ConclusionThe reduced expression of CD44v3 suppresses HESCs proliferation and decidualization, which might play a pivotal role in poor endometrial receptivity in women with RIF.