Effect of Cryopreservation on Human Cytotrophoblast Cells in Culture: hCG and PALP Production

Placental alkaline phosphatase de-phosphorylates insulin-like growth factor (IGF)-binding protein-1

BACKGROUND

Insulin-like growth factors (IGF) regulate fetal growth through their effects on placenta. Their actions are influenced by IGF binding protein-1. Phosphorylated IGFBP-1 (pIGFBP-1) has high affinity for IGF-I and usually inhibits IGF-I activity but during pregnancy, it is de-phosphorylated to generate lower affinity isoforms and consequently, increased IGF bioavailability. Here we investigate the role of placenta in this process.

RESULTS

Our data show that term human placental explants, but not their conditioned medium, can de-phosphorylate IGFBP-1 through the action of placental alkaline phosphatase (PLAP).

DISCUSSION

PLAP-mediated de-phosphorylation of IGFBP-1 may provide a mechanism for controlling IGF-I bioavailability and action at the maternal/fetal interface.

Reduced syncytin-1 expression levels in placental syndromes correlates with epigenetic hypermethylation of the ERVW-1 promoter region

Terminal differentiation of villous cytotrophoblasts (CT) ends in formation of the multinucleated syncytiotrophoblast representing the fetal-maternal interface. Aberrations during this cell-fusion process are associated with Intrauterine Growth Restriction (IUGR), Preeclampsia (PE) and High Elevated Liver and Low Platelets (HELLP) Syndrome. Syncytin-1, the envelope gene of the human Endogenous Retrovirus ERVW-1, is one of the most important genes involved in cell-fusion and showed decreased gene expression during these pathological pregnancies. The aim of this study was to determine the methylation pattern of the entire promoter of ERVW-1 and to correlate these findings with the expression profile of Syncytin-1 in the placental syndromes. 14 isolated villous cytotrophoblasts from control (n = 3), IUGR (n = 3), PE (n = 3), PE/IUGR (n = 3) and HELLP/IUGR (n = 2) placentae were used to determine the mean methylation level (ML) for the ERVW-1 promoter region. ML rose significantly from 29% in control CTs to 49% in IUGR, 53% in PE, 47% in PE/IUGR and 64% in HELLP/IUGR indicating an epigenetic down-regulation of Syncytin-1 by promoter hypermethylation. DNA demethylation of the trophoblast like cell lines BeWo, JEG-3 and JAR with 5-AZA-2′desoxycytidine (AZA) showed an increased Syncytin-1 expression and fusion ability in all cell lines. Promoter activity of the 5′LTR could be inhibited by hypermethylation 42-fold using a luciferase based reporter-gene assay. Finally overexpression of the methyltransferases DNMT3a and LSH could be responsible for a decreased Syncytin-1 expression by promoter hypermethylation of ERVW-1. Our study linked decreased Syncytin-1 expression to an epigenetic hypermethylation of the entire promoter of ERVW-1. Based on our findings we are predicting a broad aberrant epigenetic DNA-methylation pattern in pathological placentae affecting placentogenesis, but also the development of the fetus and the mother during pregnancy.

Impaired cell fusion and differentiation in placentae from patients with intrauterine growth restriction correlate with reduced levels of HERV envelope genes

One leading cause of perinatal morbidity and mortality is intrauterine growth restriction (IUGR). Several causes for IUGR have been proposed involving cytotrophoblast dysfunction. Envelope genes of the human endogenous retrovirus (HERV)-W (Syncytin-1), -FRD (Syncytin-2), and -P(b) have fusogenic properties, whereas envelope genes of HERV-R, -V1, and -V2 have putative placental functions. All six HERV envelope genes and three known cellular receptors were analyzed for expression in human control and IUGR placentae (n = 38) and in cultured cytotrophoblasts from control and IUGR (n = 8) placentae. All envelope genes demonstrated downregulation in IUGR compared to control placentae tissues, which were confirmed with cultured cytotrophoblasts. Examination of the Syncytin-1 and Syncytin-2 receptors ASCT-1/-2 and MFSD2 showed that MFSD2 was significantly expressed lower in IUGR than in control placentae and cytotrophoblasts. A reduction of Syncytin-1 protein expression was confirmed for IUGR placentae with immunoblotting and paraffin tissue sections. Embedded placental IUGR tissues showed an overall disorganized syncytiotrophoblast layer with fewer nuclei. Cytotrophoblasts from IUGR placentae demonstrated a lower cell fusion index and nuclei per syncytiotrophoblast in vitro. Fusogenic and non-fusogenic envelope genes are dysregulated in IUGR placentae and may contribute to the etiology of growth restriction in utero.