214. Altered placental gene expression following disruption of mitochondrial metabolism in mouse embryos

Abstract

Metabolic changes in the preimplantation embryo are known to alter blastocyst viability. We used a mouse embryo model, inhibiting the malate-aspartate shuttle (MAS) which is required for energy metabolism in the early embryo, to examine the consequences on subsequent fetal and placental development, and placental gene expression. Mouse zygotes were obtained from C57BL6xCBA females after gonadotrophin stimulation. Following culture in G1.2 for 48h, 8-cell embryos were cultured to the blastocyst stage in either G2.2 control media (C), G2.2 media without pyruvate (-P), or -P with 0.5 mM aminooxyacetate, an inhibitor of MAS (-P+AOA). Blastocysts were transferred to day 4 pseudopregnant Swiss mice, and fetuses and placentas were harvested on day 18 of pregnancy. RNA was extracted from placentas for real time PCR expression analysis by ddCt relative to 18S. Expression of mitochondrial transcription factors (mTERF, mTFAM, Nrf-1, Nrf-2), glucose transporters (Glut1 and Glut3) and amino acid transporters (Slc38a2 and Slc38a4) were analysed. Following transfer, fetal development per implantation was significantly reduced when embryos were cultured in –P+AOA conditions (25.9%) relative to both C and –P conditions (57.5% and 68.8% respectively). Although placental weight did not differ between treatment groups, fetal weight was significantly reduced for –P and –P+AOA groups (P < 0.05), suggestive of altered placental function thus gene expression was examined. There were no differences in gene expression between placentas from C and –P conditions for any of the genes analysed. When compared with C placentas, -P+AOA conditions reduced the expression of Glut 1 (P = 0.055) and Glut 3 (P = 0.043). The –P+AOA placentas also tended to have significantly reduced expression of Glut 3 (P = 0.06) compared with placentas from –P conditions, but all other genes were expressed similarly. This data suggests that decreased glucose transport may be the cause of reduced fetal growth as a consequence of metabolic perturbations in the embryo.