Embryonic development and implantation related gene expression of oocyte reconstructed with bovine trophoblast cells

The temporal progressive increase of interferon tau (IFNτ) secretion from the bovine trophoblast is a major embryonic signal of establishing pregnancy. Here, we cultured and isolated bovine trophoblast cells (BTs) from IVM/IVF oocytes and in vitro produced blastocysts, used them, for the first time, as donor cells for nuclear transfer and compared them with adult fibroblasts (AFs) as donor cells. BTs were reprogrammed in enucleated oocytes to blastocysts with similar efficiency to AFs (14.5% and 15.6% respectively, P≤0.05). The levels of IFNτ, CDX2 and OCT4 expression in IVF-, BT- and AF-derived blastocysts were analyzed using reverse transcription polymerase chain reaction and reverse transcription quantitative polymerase chain reaction (RT-PCR and RT-qPCR). IVF-produced embryos were used as reference to analyze the linear progressive expression of IFNτ through mid, expanded and hatching blastocysts. RT-PCR and RT-qPCR studies showed that IFNτ expression was higher in BT-derived blastocysts than IVF- and AF-derived blastocysts. Both IVF- and BT-derived blastocysts showed a progressive increase in IFNτ expression as blastocyst development advanced when it compared with AF-derived blastocysts. OCT4 was inversely related with IFNτ expression, while CDX2 was found to be directly related with IFNτ temporal expression. Persistence of high expression of IFNτ and CDX2 was found to be higher in BT-derived embryos than in IVF- or AF-derived embryos. In conclusion, using BTs expressing IFNτ as donor cells for bovine NT could be a useful tool for understanding the IFNτ genetics and epigenetics.