Expression profile of FGF receptors in preimplantation ovine embryos and the effect of FGF2 and PD173074

Abstract

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are increasingly recognized as important regulators of embryo development in mammals. This study investigated the importance of FGF signaling during in vitro development of ovine embryo. The mRNAs of four FGFR subtypes were detected throughout preimplantation development of in vitro fertilized (IVF) embryos, peaked in abundance at the morula stage, and decreased significantly at the blastocyst stage. To gain insight into the role of these mRNAs in embryo development, IVF embryos were cultured in the presence of FGF2 (100 or 500 ng/ml: beginning from days 1 or 4 to 7) or PD173074 (1 µM: beginning from days 1 to 7) as usual treatments for activation or inhibition of FGFRs, respectively. FGF2-supplementation did not affect the percentage of embryos that developed to the blastocyst, blastocyst cell count and the proportion of cells allocated in inner cell mass (ICM) and trophectoderm (TE) compared to control (p > 0.05). Also, increasing the dosage or duration of FGF2 treatment did not significantly alter blastocyst yield or differential cell count (p > 0.05). PD173074-mediated inhibition of FGFRs did not significantly affect blastocyst yield (p > 0.05). Assessment of expression profiles of lineage-associated markers revealed that FGF2 (500 ng/ml) supplementation: (i) significantly increased expression of putative hypoblast marker (GATA4), (ii) significantly decreased expression of putative epiblast (EPI) marker (NANOG) and (iii) did not change TE markers (CDX2 and IFNT) and pluripotency makers (OCT4, SOX2 and REX1). In summary, FGF2-mediated activation of FGFRs may promote a switch in transcriptional profile of ovine ICM from EPI- to hypoblast-associated gene expression.