#208 : The Adverse Effects of Vitrification on Embryo Development and Metabolic Health in Mice Offspring

Abstract

Background and Aims: Embryo vitrification is widely applied as a routine procedure of assisted reproductive technology. Cohort studies showed frozen embryo transfer (FET) was associated with an elevated risk of adverse maternal and neonatal outcomes compared with fresh embryo transfer. This study aimed to explore the effects of blastocyst vitrification on embryo development and long-term metabolic health in mice. Method: Mitochondrial function, apoptotic levels and cell numbers were examined in blastocysts with/without vitrification. Implantation rates, fetal growth and placentation were analysed after fresh and frozen blastocyst transfer. Energy consumptions were measured by indirect calorimetry. Metabolic tests were performed in adult mice offspring, including glucose tolerance, insulin tolerance and pyruvate tolerance. Serum lipid profiles were examined, and fetal and adult hepatic transcriptome status were detected by RNA-sequencing and qRT-PCR. Results: Mitochondrial dysfunction increased apoptotic levels and decreased cell numbers were observed in vitrified blastocysts. The implantation and live pup rates on embryonic day18.5 were not significantly different between the fresh and frozen groups. However, fetal weights and placental efficiencies such as the ratio of labyrinth layer/ junctional zone and microvascular density were significantly reduced after FET. Offspring aged 36 weeks in the FET group had decreased whole energy consumption, impaired glucose and pyruvate tolerance, insulin resistance, higher serum triglyceride, low-density lipoprotein and total cholesterol levels compared with the fresh group. However, these metabolic effects were not observed in mice offspring aged 14 weeks. The FET group also had altered hepatic gene expression and signaling pathways related to metabolic regulation, apoptotic cell clearance, and regulation of response to reactive oxygen species etc. Conclusion: The data indicated that blastocyst vitrification has short-term and long-term adverse effects in the mouse model. Further studies are needed to optimize vitrification procedure.