Altered Embryonic SIRT6 and SIRT7 Expression Is Associated with Impaired Developmental Competence and...

Paternal contributions to preimplantation embryo development are increasingly recognized as an important component of reproductive success, but the associations between male reproductive phenotype, early embryonic competence, and embryo molecular characteristics remain insufficiently defined. Using bovine in vitro embryo production as a translational large-mammalian model, this study evaluated whether paternal reproductive phenotype and oocyte origin were associated with embryo developmental performance and embryonic sirtuin expression. Oocytes obtained from mature cows or heifers were fertilized with semen from bulls differing in reproductive status, including bulls characterized by libido disturbances and irregular semen collection. Fertilization, cleavage, blastocyst formation, and hatching were assessed, while embryonic SIRT2, SIRT3, SIRT6, and SIRT7 expression was quantified by immunofluorescence. Early developmental endpoints were relatively preserved, whereas differences were more evident at later stages of preimplantation development. Cow-derived oocytes were associated with higher hatching rates than heifer-derived oocytes. Embryos generated using semen from bulls with an impaired reproductive phenotype showed lower developmental competence and lower SIRT6 and SIRT7 expression. SIRT6 expression showed the strongest positive correlation with hatching, and positive correlations were also observed among the analyzed sirtuins. These findings indicate that paternal reproductive phenotype and oocyte origin are associated with bovine embryo developmental competence and embryonic sirtuin profiles. Embryonic SIRT6 and SIRT7 expression may represent candidate molecular indicators of embryo competence; however, causal relationships cannot be inferred from the present study design.