Analysis of trophectoderm markers in domestic cat blastocysts cultured without zona pellucida

Domestic cat embryos generated by in vitro fertilization (IVF) and cultured without the zona pellucida have a reduced implantation capacity after embryo transfer at the blastocyst stage. The objective of this study was to evaluate the expression of trophectoderm markers in domestic cat blastocysts cultured without the zona pellucida. Two experimental groups were selected: (1) domestic cat embryos generated by IVF and cultured in vitro normally (zona intact group, ZI); and (2) domestic cat embryos generated by IVF and cultured in vitro without a zona pellucida (zona-free group, ZF). In the ZF group, the zona pellucida of the presumptive zygote was removed and these were cultured using the well of the well (WOW) system. In vitro culture was carried out for 7 days. The cleavage, morula and blastocyst rates were estimated. Finally, the relative expression levels of the trophectoderm markers TEAD4, YAP1, CDX2 and EOMES, the cell adhesion marker E-cadherin and the apoptosis marker CASP3 were evaluated by RT-qPCR in the blastocysts. The Wilcoxon test was used to evaluate differences (P < 0.05). No differences were observed in the cleavage, morula and blastocyst rates between the ZF and ZI groups. No differences were found in the expression of TEAD4, CDX2, E-cadherin and CASP3 between groups. The expression of YAP1 and EOMES was higher in ZF blastocysts than in ZI blastocysts. In conclusion, the in vitro culture without the zona pellucida generates an overexpression of YAP1 and EOMES in the domestic cat blastocysts. More studies are needed to confirm if this overexpression might affect in vivo development.