Enhancement of bovine oocyte quality by growth factors with gonadotropins during in vitro maturation (IVM)

The objective of this study was to evaluate the influence of specific growth factors upon bovine cumulus oocyte complexes during in vitro maturation. The possibility of a significant interaction between the growth factors and gonadotropins as evaluated by subsequent embryonic development was examined. In addition, substitution of growth factors or growth factor combinations for serum during in vitro embryo culture was evaluated.; Bovine immature cumulus-oocyte complexes were matured in vitro with appropriate experimental treatments then fertilized in vitro and cultured for up to ten days post-insemination. Evaluation consisted of the percent of oocytes achieving nuclear maturation/number of oocytes matured, the proportion of oocytes exhibiting cumulus cell expansion, the proportion of matured oocytes initially cleaving, and the percent of oocytes matured and inseminated which reached the blastocyst stage. Growth factors examined included epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and platelet-derived growth factor (PDGF).; Combination of EGF with low concentrations (500 ng/ml) of gonadotropins (follicle-stimulating hormone, FSH, or luteinizing hormone, LH) during IVM enabled subsequent blastocyst development in proportions comparable to those afforded by very high concentrations of gonadotropins. Addition of IGF-I (10 or 100 ng/ml) to low concentrations of LH or FSH yielded a higher rate of blastocyst development than low gonadotropins alone. Values were equivalent to that seen with high levels of gonadotropins. Growth hormone (3 ng/ml) had an additive effect with low FSH, resulting in enhanced morulae and blastocyst formation. Supplementation of PDGF with low FSH during IVM significantly increased the proportions of inseminated oocytes that reached the morula and blastocyst stages over PDGF treatment alone. The combination of EGF, IGF-I, and PDGF plus FSH yielded greater proportions of blastocysts than FSH alone but not different from FSH plus EGF. Supplementation of defined medium with growth factors for in vitro culture of IVM/IVF derived bovine embryos in contrast to serum, did not enhance in vitro embryonic development. A physiological role of growth factors during oocyte maturation is postulated.