Insulin-like growth factor 1 promotes cumulus cell expansion and nuclear maturation of oocytes via Pi3K/Akt pathway

Oocyte maturation is critical for successful fertilization and pregnancy. The mechanism underlying the control of this complex process remain relatively unknown, and even more so the specific mechanism through which oocytes acquire competentce to restrain apoptosis and resume meiosis. Insulin-like Growth Factor 1 (IGF-1) is a growth factor that had been frequently used in inducing oocyte maturation. However, the studies in downstream signaling are relatively inadequate. In this study, we initially established a linear model which illustrates the correlation between ratio of serum IGF-1 over oocyte number and follicular fluid (FF) IGF-1. Moreover, supplementation of IGF-1 to mouse COCs promotes cumulus expansion, oocyte nuclear, and expression of extracellular matrix (ECMs) involved in cumulus expansion, which was blocked by treatment of LY294002, indicating the implication of PI3K/ Akt pathway. In conclusion, this study not only provide relatively comprehensive evidence showing the importance of IGF-1, but also elucidates the downstream signaling behind the enhance of IGF-1 to oocyte maturation.