Serum miR-181d-5p levels in response to controlled ovarian stimulation: predictive value and biological function

The response to controlled ovarian stimulation (COS) for in vitro fertilization (IVF) varies dramatically from one patient to another, affecting success rates. A previous large-scale study identified increased serum miR-181d-5p levels in patients with high response to COS prior to stimulation. We aim to evaluate whether the expression of miR-181d-5p differs according to the ovarian response to COS in women undergoing intracytoplasmic sperm injection (ICSI) cycles. Samples collected prior to COS for ICSI were split into three groups depending on the ovarian response to COS: poor response (PR), <4 oocytes retrieved (n=25); normal response (NR), ≥8 and ≤12 oocytes retrieved (n=21); and high response (HR), >25 oocytes retrieved (n=20). miR-181d-5p serum levels were compared among experimental groups. miR-181d-5p levels were increased in the HR group when compared to the PR (p=0.0001) and NR groups (p=0.0079). miR-181d-5p levels correlated with the number of aspirated follicles (p<0.0001), retrieved oocytes (p<0.0001), and mature oocytes (p=0.0002). Increased miR-181d-5p levels independently predict a high response (p=0.006), with Positive and Negative Predictive Values of 66.7% and 69.4%, respectively. miR-181d-5p was also detected in the ovarian tissue in a mouse model. Moreover, computational analysis of miR-181d-5p predicted targets and promoter region suggested that this miRNA might be involved in the regulation of key signaling pathways and biological processes for female reproductive biology. In conclusion, miR-181d-5p is a promising circulating predictor of high stimulation and potential mediator of the hypothalamus-pituitary-gonad axis, providing opportunities for the individualization of COS protocols.