Amphiregulin supplementation during bovine in vitro maturation enhances oocyte quality and embryo developmental...

Despite the extensive use of in vitro embryo production (IVP) in cattle, its efficiency remains variable, mainly due to suboptimal conditions during oocyte in vitro maturation (IVM). Oocyte developmental competence is influenced by the local signaling environment, particularly by interactions between the oocyte and cumulus cells. Among the mediators involved in this process, amphiregulin (AREG) was identified as an important regulator of oocyte maturation. This study evaluated the effect of supplementing maturation media with AREG during bovine IVM on oocyte maturation, meiotic spindle organization, and subsequent embryo development. Oocytes were matured under three conditions: control (0 ng/mL AREG), A50 (50 ng/mL AREG), and A100 (100 ng/mL AREG). Supplementation with A100 significantly increased cumulus expansion compared with the control and A50 groups (P < 0.05). The A100 group also showed higher rates of progression to metaphase II (>89%) and a lower proportion of oocytes arrested at the germinal vesicle breakdown stage (P < 0.05). In addition, A100 supplementation reduced severe chromosome misalignment and spindle multipolarity and α-tubulin volume (P < 0.05). Embryo development was improved in the A100 group, as evidenced by higher cleavage rates on D3 (>80%), increased proportions of embryos reaching the ≥ 8-cell stage, and greater blastocyst and hatching rates on D7 compared with the control and A50 groups (P < 0.05). No differences among treatments were detected in blastocyst global 5 methylcytosine levels (P > 0.05). In summary, 100 ng/mL AREG supplementation during bovine IVM improves oocyte quality and embryo developmental competence without altering global DNA methylation.