Circulating microRNAs as candidate biomarkers for the ovarian response during in vitro fertilization

MicroRNAs (miRNAs) in the let-7 family have established regulatory roles in pregnancy; in this study, we evaluated whether miRNAs detectable in the circulation are associated with the ovarian response to stimulation.In total, 25 patients with infertility were divided into 3 groups: poor response (n = 9), moderate response (n = 8), and hyper-response (n = 8). Serum and endometrial tissue samples on the second day of the menstrual phase, serum samples during the mid-luteal phase, and follicular fluid samples were collected from women undergoing in vitro fertilization. The levels of let-7g-5p, let-7f-5p, and let-7i-5p in were evaluated.The levels of circulating let-7g-5p,7f-5p, and 7i-5p in the basal sera were significantly higher in the moderate ovarian response group than in the poor response group (P < .05). The expression levels of these genes tended to be down-regulated in the mid-luteal phase in the high response group (P < .05). There were no significant differences in expression levels in the endometria and follicular fluid among groups (P > .05).Circulating let-7g-5p, 7f-5p, and 7i-5p were differentially expressed between the moderate response group and the high and poor response groups. The combination of these serum miRNAs during the menstrual phase might serve as a non-invasive predictive marker for the ovarian response to in vitro fertilization.