Metformin Regulates Key MicroRNAs to Improve Endometrial Receptivity Through Increasing Implantation Marker Gene Expression in Patients with PCOS Undergoing IVF/ICSI

To some extent, the use of metformin may improve endometrial receptivity and pregnancy outcomes of women with polycystic ovarian syndrome (PCOS) undergoing in vitro fertilization/intracytoplasmic sperm injection. However, the mechanism is not well-known. The endometrium of metformin-treated group (metformin-treated patients with PCOS) and the control group (non-metformin-treated patients with PCOS) were analyzed for the expression of homeobox A10 (HOXA10) and integrin beta-3 (ITGB3) and differential micro RNA (miRNA) expression profiles. On this basis, miRDB and Target Scan databases were used to predict and screen out that miR-491-3p and miR-1910-3p may target HOXA10 and ITGB3. Furthermore, we verified the effects of metformin on the expression of HOXA10 and ITGB3, and regulatory effects of miR-1910-3p and miR-491-3p on HOXA10 and ITGB3 using Ishikawa cell line. Metformin induced a significant dose-dependent upregulation of HOXA10 and ITGB3. The results from the microarray analyses showed there were 40 differentially expressed miRNAs between the 2 groups. Among them, miR-1910-3p and miR-491-3p were the 2 significantly downregulated miRNAs. Bioinformatics prediction indicated that HOXA10 and ITGB3 are potential target genes for miR-1910-3p and miR-491-3p. In Ishikawa cells transfected with miR-491-3p mimics, the expression of HOXA10 and ITGB3 on both messenger RNA (mRNA) and protein level were lower than those in control group (P .05). Metformin likely improves endometrial receptivity through downregulating the expression of miR-491-3p and miR-1910-3p, thereby increasing the expression of HOXA10 and ITGB3 in the endometrium of PCOS women.