Effects of culture system and protein supplementation on mRNA expression in pre-implantation bovine embryos

Assisted reproduction technologies have made great progress during the last 15 years in most mammalian species, including humans. Growing evidence ind icates that bovine pre-implantation development is a superior model for inv estigating early human development than the mouse, The purpose of this stud y was to investigate the effects of two basic culture systems [tissue cultu re medium (TCM) with 5% CO2 in air or synthetic oviduct fluid (SOF) with 7% O-2, 88% N-2, 5% CO2] and various protein supplements (serum, bovine serum albumin or polyvinyl alcohol) on the relative abundance of a set of develo pmentally important gene transcripts in bovine morulae and blastocysts and to compare the results with those for their in-vivo-derived counterparts, T he basic culture system including the basic medium composition and oxygen t ension had profound effects on the amounts of specific transcripts in bovin e embryos, whereas the 'protein source' had only weak effects. Significant differences (P less than or equal to 0.05) in the relative abundance of spe cific gene transcripts were detected between in-vivo and in-vitro-derived e mbryos, especially at the morula stage. More differences were found between embryos produced in the TCM system and in-vivo-derived embryos than betwee n SOF-generated embryos and their in-vivo counterparts. No differences were found in the relative abundance of gene transcripts in embryos generated u nder chemically defined conditions in the two different laboratories, It is concluded that the SOF system provides an environment in which pre-implant ation development of bovine embryos is more similar to that occurring in vi vo than in the TCM system.