Development of bovine embryos in vitro in coculture with murine mesenchymal stem cells and embryonic fibroblasts.

Despite the progress on development of new culture media, in vitro-produced embryos still display lower quality when compared to the in vivo-produced counterparts. Coculture has been reconsidered as an alternative to improve embryo quality. Mesenchymal stem cells (MSC) and murine embryonic fibroblasts (MEF) have been extensively used as feeder layers due to their capacity to release growth factors. In the present study we investigated the effect of these feeder layers in oocyte maturation and/or embryo development under in vitro conditions. Oocytes were matured in control (CTRL) conditions or in coculture with MSC or MEF. In vitro fertilization and embryo culture until fourth day were performed in CTRL condition for all groups. Embryos from fourth day on were then cultured until the eighth day in CTRL or in coculture system. No significant differences for metaphase II stage and apoptosis in oocytes were found among the groups. There was also no difference among the groups when we evaluated blastocyst formation on the seventh and eighth day, with exception of a higher hatched blastocyst rate in the group maturated and cultivated in CTRL condition when compared to the group matured and cocultured with MSC. Also no difference was observed in the number of cells in the whole embryos, in the inner cell mass, in the trophoblast and at apoptotic stage on the eighth day. We conclude that coculture with MSC or MEF during maturation and/or embryo development do not enhance the in vitro production of bovine embryos.