Effects of ghrelin on developmental competence and gene expression of in vitro fertilized ovine embryos

The objective was to determine the effects of various ghrelin concentrations (0, 10, 50, and 250 ng/mL) during in vitro oocyte maturation (IVM) and in vitro embryo culture (IVC) on ovine embryo development and expression patterns of genes involved in transcription regulation (OCT4), glucose transport (GLUT1), pregnancy recognition (IFNT), and ghrelin receptor (GHSR-1a). Rates of cleavage and blastocyst formation were decreased when oocytes were matured with 250 ng/mL ghrelin compared with 0, 10, or 50 ng/mL ghrelin (P < 0.05). Addition of 50 ng/mL ghrelin during IVC or during IVM and IVC significantly increased blastocyst rates (35.3% and 36.7% vs. 26.9% and 26.8%, respectively) and total cell numbers per blastocyst (110.4 and 108.3 vs. 81.2 and 77.4) compared with 0 and 10 ng/mL ghrelin. However, a high concentration (250 ng/mL) of ghrelin during IVM and IVC decreased cleavage, blastocyst rate, and total cell number of blastocyst compared with low concentrations (P < 0.05). Relative abundances of GLUT1 and IFNT transcripts were higher in blastocysts treated with 50 ng/mL ghrelin during IVC compared with other concentrations (P < 0.05). Expression of GHSR-1a was higher when 10 ng/mL ghrelin was added during IVM (0.079) or during IVM and IVC (0.053) compared with other treatments. However, addition of ghrelin at higher concentrations (50 or 250 ng/mL) reduced relative abundances of GHSR-1a transcripts (0.032 and 0.039, P < 0.05). In conclusion, appropriate concentrations of ghrelin promoted ovine blastocyst formation in vitro and increased expression of GLUT1, IFNT, and GHSR-1a genes in blastocysts, although a high concentration of ghrelin suppressed embryo development.