Abstract: Objective To investigate the regulatory mechanism of PTEN on the activation and growth of primitive follicles in rat. Methods Ovaries from 2-day-old rats were cultured in Waymouth culturing system in vitro for 0, 4 and 8 days. PCR, Western blotting and primordial follicle development were assessed for the silencing efficiency of the lentivirus PTEN siRNA and its effect on primordial follicle onset. PTEN mRNA and protein expression in primary follicular proliferation was detected by PCR and immunohistochemical staining. Furthermore, the PI3K inhibitor LY294002 was used to explore the possible signaling pathways of PTEN in primordial folliculogenesis. Results Our results showed that PTEN mRNA and protein were detected in the primordial follicles, and the expression levels were reduced with the development of primordial follicles（P<0.01）. After PTEN-shRNA lentiviral transfection, there can be seen that lentivirus was successfully delivered to the ovarian tissue in vitro by fluorescence imaging. And the number of primordial follicles was reduced（P<0.01）, indicating that PTEN participates in the initiation of primordial follicles. Conclusion PTEN can promote primordial follicle development through the PI3K signaling pathway and by regulating estrogen and progesterone secretion. PTEN plays an important role in the initiation and development of primordial follicles.

Key words: PTEN, primordial follicle, lentivirus, RNA interference