The activation of dormant primordial follicles and ovarian angiogenesis has been attempted as a new treatment strategy for age-related ovarian aging. This study examined whether visfatin rescues age-related fertility decline in female mice aged 18 months, and whether this effect relates to the mTOR/PI3K signaling pathways for activation of primordial follicles and ovarian angiogenesis. Female mice were intraperitoneally injected with 0.1 ml of 500 ng/ml or 1000 ng/ml of visfatin three times at intervals of 2 days, and both ovaries were provided for H&E staining. In another experiment, the mice were superovulated with pregnant mare's serum gonadotropin and human chorionic gonadotropin, and were mated with males. After 18 h, zygotes were collected and cultured for 4 days, and numbers and embryo developmental competency of zygotes retrieved were evaluated. The expression of mTOR/PI3K signaling pathway regulated genes (4EBP1, S6K1, and RPS6) and angiogenic factors (VEGF, visfatin, and SDF-1α) in the ovary were examined. As well, visfatin-treated mice were mated with male mice for 2 weeks, and the pregnancy outcome was monitored up to 3 weeks. Visfatin significantly increased the total numbers of follicles compared with control. Numbers of zygotes retrieved, blastocyst formation rate, and pregnancy rate were significantly increased at 500 ng/ml of visfatin (2.83%, 40.0%, and 80%, respectively) compared with control (0, 0, and no pregnancy). Ovarian expressions of S6K1, RPS6, VEGF, visfatin, and SDF-1α were significantly stimulated at 500 ng/ml of visfatin. These results show that visfatin treatment of an optimal dose rescues age-related decline in fertility, possibly by stimulating mTOR/PI3K signaling.
Keywords: Fertility; Ovarian aging; Primordial follicle activation; Visfatin; mTOR/PI3K.