Hormonal protocol used for cervical dilation in ewes does not affect morphological embryo quality but reduces recovery rate and temporarily alters gene expression.

Abstract

Information on the impact of hormonal protocols for cervical dilation on the quality of ovine embryos is scarce. To compare the quality of embryos after cervical dilation protocol, ewes (n=64) were allocated into either a treated group (100μg estradiol benzoate intravenous and 0.12mg cloprostenol intramuscularly, 12hours before embryo collection plus 100 iu oxytocin intravenous 15 minutes before the collection procedure) or a control group (saline). Luteal function was analysed using ultrasonography and P4 measurement. Some collected embryos were frozen/thawed for gene expression, others were cultured in vitro, frozen/thawed for gene expression, and the remaining embryos were fixed for the apoptosis test (TUNEL test). The treatment reduced fluid (p=0.04) and structure (p=0.03) recovery rates, but the morphological quality, development stage, and apoptosis incidence of the embryos were not affected by treatment. The corpora lutea of the control group had greater blood perfusion (p=0.002) and greater P4 concentrations at 6, 9, and 12h after the treatment (p<0.0001). The expression of BAX, BCL2, PRDX1, and HSP90 genes were not affected by the treatment. However, the embryos in the treated group had fewer NANOG and OCT4 transcripts than control embryos (p=0.008; p=0.006, respectively). After culture, there was no difference between the groups in any gene. The hormonal protocol for cervical dilation reduced the efficiency of embryo collection. In addition, the treatment induced luteolysis and a transient alteration of embryo gene expression, however there were no detectable changes in embryo morphological quality, development stage, or incidence of apoptosis.