Recombinant human follicle-stimulating hormone and transforming growth factor-alpha enhance in vitro maturation of porcine oocytes

The biological functions of recombinant human follicle-stimulating hormone (FSH) and transforming growth factor-α (TGF-α) on in vitro maturation of porcine oocytes were investigated. Cumulus-oocyte complexes were matured in defined porcine oocyte medium containing 0-0.1 IU/ml FSH in the presence or absence of 10 ng/ml TGF-α. The percentage of oocytes reaching metaphase II was significantly higher with the addition of 0.01-0.1 IU/ml FSH compared with no addition, and was further enhanced in the presence of TGF-α. The rates of sperm penetration and blastocyst formation were significantly higher with the addition of 0.05-0.1 IU/ml FSH compared with no addition after in vitro fertilization and embryo culture. There was no beneficial effect of FSH and TGF-α on nuclear maturation of denuded oocytes. The specific EGF receptor inhibitor, AG1478, completely inhibited TGF-α-induced meiotic resumption, but did not completely prevent the stimulatory effect of FSH. Addition of both FSH and TGF-α significantly enhanced cumulus expansion compared with no addition. When cumulus expansion-related genes (HAS2, HAPLN1, and VCAN) mRNA expression in COCs was measured during in vitro maturaiton, addition of both of FSH and TGF-α upregulated the expression of HAS2 mRNA after 20 hr culture and HAPLN1 mRNA after 44 hr culture compared with no addition. Expression of VCAN mRNA was significantly higher in the presence of FSH compared with addition of TGF-α alone. These results suggest that FSH and TGF-α synergistically enhance porcine oocyte maturation via cumulus cells, and act through different signaling pathways.