Growth hormone and in vitro maturation of rhesus macaque oocytes and subsequent embryo development

In vitro oocyte maturation (IVM) has been relatively unsuccessful in primates and non-human primates compared with other species and maturation in vivo. In order to improve oocyte quality and ultimately developmental competence, in vitro conditions need to be improved. The role of growth hormone (GH) in female reproduction and oocyte maturation has been investigated in a number of species, but data for the primate and non-human primate are limited. Studies were designed to determine the role of GH in IVM of rhesus macaque oocytes by confirming the presence of GH receptors (GHR) on cumulus oocyte complexes, investigating the effects of recombinant human GH (r-hGH) during IVM and embryo development and determining gene expression after IVM with r-hGH supplementation. The presence of GHR was confirmed on cumulus oocyte complexes and embryos of the rhesus macaque, suggesting involvement of GH in oocyte maturation and development. The addition of low concentrations of r-hGH (1 and 10 ng/ml) to IVM medium stimulated cumulus expansion, while a higher doseage (100 ng/ml) increased the percentage of embryos that developed to the 9-16 cell stage. The addition of r-hGH to embryo culture media did not improve embryo development or differential cell counts of blastocysts. The addition of 100 ng/ml r-hGH to IVM medium increased mRNA expression levels of insulin-like growth factor 2 (IGF2) and steroidogenic acute regulator (STAR) in macaque oocytes, possibly indicating GH mediation by the insulin-like growth factor pathway and involvement of steroidogenesis in improving oocyte developmental competence. The presence of GHR, increased cumulus expansion, increased percentage of embryos at the 9-16 cell stage and increased expression of IGF2 and STAR after r-hGH supplementation demonstrate the involvement of GH in macaque oocyte maturation.