Basic FGF promotes proliferation of ovarian granulosa cells in the laying chickens via FGFR1 and PKC pathway

The proliferating effect of basic fibroblast growth factor (bFGF) on granulosa cells from ovarian pre-hierarchical follicles was evaluated in the laying chickens. Expression of bFGF receptor 1 (FGFR1) from small yellow follicles was determined by immunohistochemistry and RT-PCR. The FGFR1 protein and mRNA were intensively expressed in the granulosa layer. After 8- to 24-h treatment with bFGF (0.1-100 ng/ml), the proliferation of cultured granulosa cells was remarkably enhanced in a dose- and time-dependent manner. The FGFR1 antagonist SU5402 inhibited bFGF-induced cell proliferation. This stimulating effect was further confirmed by 5-bromo-2-deoxyuridine incorporation and terminal transferase dUTP nick end-labelling assay. Immunocytochemistry of protein kinases A (PKA) and C (PKC) showed that the pro-proliferation action of bFGF predominantly activated PKC expression. Meanwhile, the bFGF-induced cell proliferation was significantly promoted by PKC activator PMA and inhibited by PKC inhibitor H(7) (p < 0.05). In addition, the bFGF-elicited cell proliferation was accompanied with increased mRNA expression of the cell cycle-regulating genes including cyclins D1 and E1, cyclin-dependent kinases 2 and 6. In conclusion, bFGF promoted the proliferation of ovarian granulosa cells through binding with FGFR1 and involving PKC pathway in the pre-hierarchical follicles of the laying chickens.