Recombinant bovine somatotropin alters embryonic gene expression in superovulated ewes

The aim of this study was to determine if recombinant bovine somatotropin (rbST) administration before a superovulatory protocol increases the ovulation rate and embryo quality, including gene expression, in sheep. Forty multiparous Santa Inês ewes were superovulated using 133 IU of FSH in six decreasing doses. Ewes from the treatment group (GST; n = 20), received a subcutaneous injection of 50 mg rbST 3 days before beginning the superovulatory treatment, while the control group (GCON; n = 20) remained as controls receiving saline solution. The ovaries were scanned with ultrasound to evaluate the follicular population, ovulation rate, and corpora lutea. Blood samples were collected to determine insulin-like growth factor 1 (IGF-1) concentrations. Embryos were recovered and analyzed for gene expression. The administration of rbST significantly increased serum IGF-1 levels while downregulating the expression of BCL2 and PRDX1 in embryos. Additionally, the expression of SIRT2 and CDH1 was upregulated in embryos collected from GST ewes, suggesting enhanced metabolic regulation and cell adhesion processes within embryonic cells. However, no significant differences were observed between GST and GCON in corpora lutea count, viable embryos. The treatment did not modify the follicular populations, the incidence of estrus, or the ovulation rate. In summary, administering a single dose of rbST before beginning the superovulation (SOV) treatment modulated the expression of genes related to embryo development. These findings provide novel insights into the non-ovarian effects of rbST in sheep and suggest a potential strategy to improve embryo developmental competence in assisted reproduction protocols.