Novel genes associated with a placental phenotype in knockout mice also respond to cellular stressors in primary human trophoblasts.

INTRODUCTION: Placental insufficiency is a leading cause of intrauterine growth restriction, contributing to perinatal morbidity and mortality. The molecular regulation of placental development and what causes placental insufficiency is poorly understood. Recently, a panel of genes were found to cause significant placental dysmorphologies in mice with severely growth restricted off-spring. We aimed to assess whether these genes were also implicated in human intrauterine growth restriction. METHODS: We explored the expression of nine genes in primary cytotrophoblast cells in hypoxic (n = 6) and glucose starvation (n = 5) conditions in vitro. We also explored whether the genes were dysregulated in intrauterine growth restricted human placental samples (n = 11), with (n = 20) or without preeclampsia compared to gestationally matched controls (<34 weeks gestation) (n = 17). RESULTS: Hypoxic stress significantly upregulated the expressions of BRD2 (p = 0.0313), SMG9 (p = 0.0313) genes. In contrast, glucose starvation significantly suppressed Kif1bp (p = 0.0089) in primary cytotrophoblasts. The FRYL, NEK9, CHTOP, PSPH, ATP11A, HM13 genes did not change under hypoxia or glucose starvation conditions. The expression of these genes was not altered in placenta from patients with intrauterine growth restriction, compared to gestationally matched controls. DISCUSSION: We demonstrate that some of the genes that cause a placental phenotype in mice, respond to hypoxic and glucose mediated stress in human cytotrophoblast isolations. Despite this, they are unchanged in placenta from patients with intrauterine growth restriction. Therefore, dysregulation of these genes is less likely to contribute to preterm intrauterine growth restriction in humans.

SLC38A4 Amino Acid Transporter Expression Is Significantly Lower in Early Preterm Intrauterine Growth Restriction Complicated Placentas.

Intrauterine growth restriction (IUGR), predominantly caused by placental insufficiency, affects partitioning of nutrients to the fetus. The system A sodium-coupled transporters (SNAT or SLC38), of types A1, A2, and A4, control non-essential amino acid uptake and supply. Here, we aimed to investigate the expression of these transporters across different placental disease cohorts and cells. To determine disease impact, transporter expressions at the gene (qPCR) and protein (western blots) level were assessed in gestationally matched placental tissues. Early (<34 weeks), and late (34−36 weeks) onset IUGR cases with/out preeclampsia were compared to preterm controls. We also investigated level of transporter expression in primary trophoblasts under glucose deprivation (n = 6) and hypoxia conditions (n = 7). SLC38A4 protein was significantly downregulated in early preterm pregnancies complicated with IUGR with/out preeclampsia. There were no differences in late preterm IUGR cohorts. Furthermore, we demonstrate for the first time in primary trophoblast cells, that gene expression of the transporters was sensitive to and induced by glucose starvation. SLC38A4 mRNA expression was also significantly upregulated in response to hypoxia. Thus, SLC38A4 expression was persistently low in early preterm IUGR pregnancies, regardless of disease aetiology. This suggests that gestational age at delivery, and consequently IUGR severity, may influence loss of its expression.