Regulatory role of Wnt signal in the oestradiol synthesis of different size categories of ovarian follicles in buffalo (Bubalus bubalis)

The aim of the present study was to understand the role of Wnt signal in ovarian oestradiol synthesis in various size categories of ovarian follicles. A six-day cell culture system was adopted to test the effect of a Wnt inhibitor i.e. Inhibitor of Wnt response (IWR) on the ovarian granulosa cell oestradiol synthesis and associated genes related to oestradiol synthesis and Wnt signalling (CYP19A1, CCND2, WNT2, FZD6, DVL1, APC, AXIN2, CTNNB1) in buffalo. It was conducted with four groups: Group 1: control, Group 2: control + FSH, Group 3: IWR, Group 4: IWR + FSH. No significant effect of IWR was observed on the ovarian granulosa cell proliferation. No significant difference in the oestradiol levels was found in the spent media harvested after six days of in vitro culture among different groups in small and large-sized ovarian follicles. However, the oestradiol level varied significantly (p < .05) among different treatment groups in medium-sized follicles. The oestradiol level was significantly lower (p < .05) in IWR group compared with the control group and was also significantly lower in IWR + FSH group compared with the FSH group. The Wnt inhibitor had significantly (p < .05) reduced the gene expression of CYP19A1 in large ovarian follicles. Varied effects of IWR-1 and FSH on the expression of other genes were observed. The results indicated that there is a positive role of Wnt signal in oestradiol synthesis in buffalo, but the positive role was more discernible in medium- and large-sized follicles.