In female mammals, the majority of primordial follicles (PFs) are physiologically quiescent, and only a few of them are activated and enter the growing follicle pool. Specific molecules, such as mammalian target of rapamycin (mTOR) and the serine/threonine kinase Akt (AKT), have been proven to be important for PF activation. However, how the transcription of these genes is regulated is not clear. Although activators of mTOR or AKT have been successfully used to rescue the fertility of patients with premature ovarian insufficiency, the low efficacy and unclear safety profile of these drugs hinder their clinical use in the in vitro activation (IVA) of PFs. Here, sirtuin 1 (SIRT1), an NAD-dependent deacetylase, was demonstrated to activate mouse PFs independent of its deacetylase activity. SIRT1 was prominently expressed in pregranulosa cells (pGCs) and oocytes, and its expression was increased during PF activation. PF activation was achieved by either up-regulating SIRT1 with a specific activator or overexpressing SIRT1. Moreover, SIRT1 knockdown in oocytes or pGCs could significantly suppress PF activation. Further studies demonstrated that SIRT1 enhanced both Akt1 and mTOR expression by acting more as a transcription cofactor, directly binding to the respective gene promoters, than as a deacetylase. Importantly, we explored the potential clinical applications of targeting SIRT1 in IVA via short-term treatment of cultured ovaries from mice and human ovarian tissues to activate PFs by applying the SIRT1 activator resveratrol. RSV-induced IVA could be a candidate strategy to develop more efficient procedures for future clinical treatment of infertility.-Zhang, T., Du, X., Zhao, L., He, M., Lin, L., Guo, C., Zhang, X., Han, J., Yan, H., Huang, K., Sun, G., Yan, L., Zhou, B., Xia, G., Qin, Y., Wang, C. SIRT1 facilitates primordial follicle recruitment independent of deacetylase activity through directly modulating Akt1 and mTOR transcription.
Keywords: in vitro activation; ovary; primordial follicle activation; resveratrol.