Sex-specific effects of in vitro culture and embryo transfer on cardiac growth in sheep offspring

Embryo culture with and without human serum supplementation, previously common practice in assisted reproductive technologies (ARTs), have been associated with increased heart weight in early and late gestation in the sheep fetus. The present study aimed to determine whether the effects of embryo culture and transfer on cardiac growth and associated signalling pathways persist after birth. Embryos were either transferred to an intermediate ewe (ET) or cultured in vitro in the absence (IVC) or presence of human serum (IVCHS) and with methionine supplementation (IVCHS+M) for 6 days after mating. Naturally mated (NM) ewes were used as controls. There was an increase in the number of cardiomyocytes in the left ventricle of IVC and IVCHS+M compared to IVCHS lambs, but only in males. There were no differences in birth weight, body weight, relative heart weight, left ventricular weight, signalling molecules involved in hypertrophy, apoptosis or fibrosis at 6 months of age between the treatment groups. However, there was increased protein abundance of signalling molecules involved in ribosomal biogenesis, in male offspring from the IVC and IVCHS+M groups compared to the IVCHS group. In conclusion, the composition of the culture media used for in vitro embryo culture altered the abundance of proteins involved in ribosomal biogenesis as well as cardiomyocyte endowment in a sex specific manner. Our data suggest that male embryos cultured in the presence of human serum leads to molecular and structural changes that may detrimentally impact cardiovascular health across the life-course.