Proliferative activity and expression of estrogen receptors in mesenchymal stromal cells of the endometrium in patients with recurrent implantation failure

In cases of recurrent implantation failure (RIF), the main focus is on endometrial receptivity disorders, but the cellular and receptor characteristics of endometrial mesenchymal stromal cells (eMSCs) in this group have not been sufficiently studied. The present study aims to describe the characteristics of eMSCs in order to identify a new link in the pathogenesis of RIF and to further develop potential therapeutic targets. Research objective. To study the proliferative activity and expression of ERα in eMSCs in patients with RIF of euploid embryos. The pilot study included 5 patients aged 25–40 years: 4 patients with RIF and one patient with a history of 6 births (control). MSCs were isolated from endometrial biopsies in the first phase of the cycle. ESR1 gene expression was determined by PCR, and ERα protein was determined by fluorescent immunocytochemistry. Proliferation was assessed in the IncuCyte system in a control medium and with the addition of 0.1 nM 17β-estradiol. The ESR1 mRNA content in endometrial MSCs was 10 times higher than in adipose tissue MSCs. In patients with infertility, the amount of ERα was reduced relative to the control group, with the lowest levels found in patients with tubal-peritoneal infertility. MSCs from the endometrium of patients with RIF showed a significantly lower proliferation rate compared to the control group. The lowest proliferative capacity was found in patients with infertility of unknown origin. The addition of 17β-estradiol caused a statistically significant increase in proliferation in patients with good fertility and patients with infertility of unknown origin, but did not stimulate proliferation in tubal-peritoneal infertility. For the first time, a decrease in proliferative activity and ERα expression in endometrial MSCs in patients with PNI has been demonstrated. MSCs from patients with unexplained infertility remain sensitive to estrogen despite a decrease in the number of receptors. The results expand our understanding of the functional characteristics of endometrial MSCs in cases of RIF.