Primordial follicle pool provides all available oocytes throughout the whole reproductive life span. Abnormal regulation in primordial follicle assembly leads to abnormal size of primordial follicle pool, even causes infertility. Here, miR-378-3p was proved to regulate mouse primordial follicle assembly both in vivo and in vitro. The expression of miR-378-3p significantly increased in mice ovaries from 17.5 dpc (days post coitum) up to 3 dpp (day post partum) compared with the expression of 16.5 dpc ovaries, which suggested that miR-378-3p was involved in primordial follicle assembly. To uncover the underlying mechanism, newborn mice ovaries were cultured in vitro in the presence of rapamycin and 3-methyladenine, which showed that the expression of miR-378-3p changed together with the percentage of primordial follicle. Moreover, during the normal process of primordial follicle assembly between 17.6 dpc and 3 dpp, autophagy is activated, while, apoptosis is inhibited. The in vivo results showed that newborn mice starved for 1.5 days showing the increased miR-378-3p, activated autophagy and inhibited apoptosis in the ovaries, had more percentage of primordial follicles. Over-expression of miR-378-3p using miR-378-3p agomir caused increased percentage of primordial follicle, increased level of autophagy, and decreased level of apoptosis. Knockdown of miR-378-3p by miR-378-3p antiagomir had the opposite results. Using pmirGLO Dual-Luciferase miRNA Target Expression system, we confirmed both PDK1 and Caspase9 were targets of miR-378-3p, which suggested that miR-378-3p activated autophagy by targeting PDK1 and inhibited apoptosis by targeting Caspase9. MiR-378-3p could be used as a biomarker of diseases caused by abnormal size of primordial follicle pool for diagnosis, prevention, or therapy.

原始卵泡池在整个生殖生命周期中提供所有可用的卵母细胞。原始卵泡组装的异常调节导致原始卵泡池大小异常，甚至导致不孕。在这里，证明 miR-378-3p 在体内和体外调节小鼠原始卵泡组装。与 16.5 dpc 卵巢的表达相比，miR-378-3p 在 17.5 dpc（交配后天数）至 3 dpp（产后天数）的小鼠卵巢中的表达显着增加，这表明 miR-378-3p 参与了原始卵泡组装。为了揭示其潜在机制，在雷帕霉素和 3-甲基腺嘌呤存在下体外培养新生小鼠卵巢，结果表明 miR-378-3p 的表达随原始卵泡百分比的变化而变化。而且，在17.6 dpc和3 dpp之间原始卵泡组装的正常过程中，自噬被激活，而细胞凋亡被抑制。体内结果表明，新生小鼠饥饿 1.5 天后，miR-378-3p 增加，卵巢中的自噬激活并抑制细胞凋亡，原始卵泡的百分比更高。使用 miR-378-3p agomir 过表达 miR-378-3p 导致原始卵泡百分比增加、自噬水平增加和细胞凋亡水平降低。miR-378-3p antiagomir 对 miR-378-3p 的敲低产生了相反的结果。使用 pmirGLO Dual-Luciferase miRNA 靶标表达系统，我们确认 PDK1 和 Caspase9 都是 miR-378-3p 的靶标，这表明 miR-378-3p 通过靶向 PDK1 激活自噬并通过靶向 Caspase9 抑制细胞凋亡。