LAUSR

The in vitro embryo's competence is lower than in vivo counterparts and miRNAs found to affect the developmental competence, affecting pluripotency, stress level and apoptosis in embryos. We aimed to investigate the effect of miRNA-155 on parthenogenically activated early development porcine embryos at the preimplantation blastocyst stage. We designed miRNA-155 mimics and inhibitors and microinjected them into post-activated oocytes. The embryonic cleavage rate, blastocyst rate, and embryo development quality in terms of stress and apoptosis levels were investigated by confocal microscopy. Furthermore, we selected target genes, analyzed gene interaction and prediction networks, and compared the gene expression level in treatments and controls. miRNA-155 inhibition improved in vitro developmental competence by increasing cell numbers and reducing stress and apoptosis levels. The cleavage rate in the miRNA-155 inhibitor group was significantly higher (P < 0.05) than that in the miRNA-155 mimic group, but not in the control, whereas the blastocyst rate of the miRNA-155 inhibitor group was statistically significantly higher (P < 0.05) than in both control and miRNA-155 mimic groups. The relative gene expression level analysis showed downregulation of mRNAs related to stress and apoptosis, BAX, and the stress-induced autophagy gene ATF4, and TNF-ɑ in the miRNA-155 inhibitor group. Moreover, miRNA-155 inhibition showed upregulation of the relative expression of OCT4, ZEB2, BCL2, and IL-1 mRNA compared to control and mimic groups. However, the miRNA-155 mimic-injected group showed lower cleavage rates and blastocyst development rates than the other two groups. In conclusion, miRNA-155 inhibition in porcine in vitro embryos improved their preimplantation developmental competence and in vitro embryo production.