Basic fibroblast growth factor suppresses meiosis and promotes mitosis of ovarian germ cells in embryonic chickens.

Basic fibroblast growth factor (bFGF or FGF2) plays diverse roles in regulating cell proliferation, migration and differentiation during embryo development. In this study, the effect of bFGF on ovarian germ cell development was investigated in the embryonic chicken by in vitro and in vivo experiments. Results showed that a remarkable decrease in bFGF expression in the ovarian cortex was manifested during meiosis progression. With ovary organ culture, we revealed that meiosis was initiated after retinoic acid (RA) treatment alone but was decreased after combined bFGF treatment that was detected by real time RT-PCR, fluorescence immunohistochemistry and Giemsa staining. Further, no significant difference in mRNA expression of either RA metabolism-related enzymes (Raldh2 and Cyp26b1) or RA receptors was displayed after bFGF challenge. This result suggests that the suppression of bFGF on meiosis was unlikely through inhibition of RA signaling. In addition, as a mitogen, bFGF administration increased germ cell proliferation (via BrdU incorporation) in cultured organ or cells in vitro and also in developing embryos in vivo. In contrast, blockade of bFGF action by SU5402 (an FGFR1 antagonist) or inhibition of protein kinase C signaling showed inhibited effect of bFGF on mitosis. In conclusion, bFGF suppresses RA-induced entry of germ cells into meiosis to ensure embryonic ovarian germ cells to maintain at undifferentiated status and accelerate germ cell proliferation by binding with FGFR1 involving PKC activation in the chicken.