Zona pellucida removal modifies the expression and release of specific microRNAs in domestic cat blastocysts.

The in vitro culture of domestic cat embryos without the zona pellucida affects their implantation capacity. MicroRNAs (miRNAs) have an important role in embryo-maternal communication and implantation. The objective of this study was to evaluate the expression of specific miRNAs in domestic cat blastocysts cultured without the zona pellucida. Two experimental groups were done: (1) domestic cat embryos cultured with the zona pellucida (zona intact control group, ZI); and (2) cultured without the zona pellucida (zona free group, ZF). The cleavage, morula and blastocyst rates were evaluated. The blastocysts and their spent medium were used for miRNA expression analysis using RT-qPCR ( miR-21, miR-24, mi25, miR-29, miR-96, miR-98, miR-103, miR-191, miR-196, miR-199, miR-130, miR-155 and miR-302 ). The pre-mature microRNAs (pre-miRNAs) and miRNAs were evaluated in the blastocysts and only miRNAs were evaluated in the spent medium. No differences were observed in the cleavage, morula and blastocyst rates between the ZF and ZI groups ( P > 0.05). For miRNAs analysis, miR-103 and miR-191 had the most stable expression and were selected as internal controls. ZF blastocysts had a higher expression of miR-21 , miR-25 , miR-29 and miR-199 and a lower expression of miR-96 than their ZI counterparts ( P < 0.05). Furthermore, higher levels of miR-21 , miR-25 and miR-98 were detected in the spent medium of ZF blastocysts ( P < 0.05). In conclusion, in vitro culture of domestic cat embryos without the zona pellucida modifies the expression of miR-21 , miR-25 , miR-29 , miR-199 and miR-96 at the blastocyst stage and the release of miR-21 , miR-25 and miR-98 .