The interaction of Wnt signaling members with growth factors in cultured granulosa cells

Wnt family members have recently been distinguished in the adult ovary with potential roles in ovarian function. Though particular growth factors interact with Wnt signaling members in extraovarian cell types, it is unclear whether this interaction is applicable in the granulosa cells. Therefore, the current study aimed to determine the effect of insulin-like growth factor-1 (IGF-I), epidermal growth factor (EGF) and basic fibroblast growth factor (FGF-β) on Wnt ligands WNT2 and WNT4 and Wnt receptor Frizzled-4 (FZD4) protein levels in cultured mouse granulosa cells. Granulosa cells were isolated from antral follicles of adult Balb/C mice and cultured for 24 hours in the presence of 100 ng/mL of IGF-I, or EGF or FGF-β. WNT2, WNT4 and FZD4 protein levels were evaluated through western blotting after the culture process. IGF-I treated granulosa cells had significantly the highest level of WNT2 and WNT4 as well as FZD4 when compared to FGF-β and EGF groups. FGF-β group had a significantly higher level of WNT2, WNT4 and FZD4 expression when compared to EGF group. FZD4 expression was at the highest level in the IGF-I group and this difference was statistically significant for all groups including uncultured cells and vehicle group. In addition, FGF-β was shown to positively affect the adhesion of granulosa cells. This study demonstrates that IGF-I, FGF-β and EGF have differential effects on the expressions of WNT2, WNT4, and FZD4 in cultured mouse granulosa cells, suggesting that particular growth factors related to ovarian function might conduct their roles in the ovary through Wnt signaling.