Fusion of the trophoblast-derived choriocarcinoma cell line BeWo can be triggered by forskolin. BeWo cells are regularly used as a cell culture model to mimic in vivo syncytialisation of placental villous trophoblast. The β subunit of human chorionic gonadotropin (CGB), placental alkaline phosphatase as well as placental protein 13 (PP13, LGALS13) are exclusively expressed in the syncytiotrophoblast of the human placenta, and CGB is commonly used as a marker of syncytial differentiation. Here we tested the hypothesis that syncytial fusion precedes CGB and LGALS13 expression in trophoblast-derived BeWo cells. BeWo cells were cultured for 48 h in the presence or absence of forskolin and varying concentrations of H-89, a protein kinase A inhibitor that interferes with the forskolin-mediated pathway of syncytial fusion. LGALS13 and CGB expression were quantified by DELFIA and real-time PCR. Cell fusion was determined by morphological analysis and cell counting after immunofluorescence staining. In forskolin-stimulated BeWo cells that were hindered to fuse by treatment with H-89, levels of CGB protein expression were not altered, while LGALS13 protein and mRNA expression decreased significantly to control levels without forskolin. The LGALS13 protein expression data coincided with a significant decrease in syncytial fusion, while CGB protein expression was unaffected by rates of cell fusion and proliferation. We postulate that CGB protein expression is not necessarily linked to syncytial fusion, and thus CGB should be used with great caution as a marker of BeWo cell fusion.

Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.

Carbamylation of proteins through reactive cyanate has been demonstrated to predict an increased cardiovascular risk. Cyanate is formed in vivo by breakdown of urea and at sites of inflammation by the phagocyte protein myeloperoxidase. Because myeloperoxidase (MPO) associates with high-density lipoprotein (HDL) in human atherosclerotic intima, we examined in the present study whether cyanate specifically targets HDL. Mass spectrometry analysis revealed that protein carbamylation is a major posttranslational modification of HDL. The carbamyllysine content of lesion-derived HDL was more than 20-fold higher in comparison with 3-chlorotyrosine levels, a specific oxidation product of MPO. Notably, the carbamyllysine content of lesion-derived HDL was five- to eightfold higher when compared with lesion-derived low-density lipoprotein (LDL) or total lesion protein and increased with lesion severity. The carbamyllysine content of HDL, but not of LDL, correlated with levels of 3-chlorotyrosine, suggesting that MPO mediated carbamylation in the vessel wall. Remarkably, one carbamyllysine residue per HDL-associated apolipoprotein A-I was sufficient to induce cholesterol accumulation and lipid-droplet formation in macrophages through a pathway requiring the HDL-receptor scavenger receptor class B, type I. The present results raise the possibility that HDL carbamylation contributes to foam cell formation in atherosclerotic lesions. Antioxid. Redox Signal. 14, 2337–2346.

The placenta is an endocrine fetal organ, which secretes a plethora of steroid- and proteo-hormones, metabolic proteins, growth factors, and cytokines in order to adapt maternal physiology to pregnancy. Central to the growth of the fetus is the supply with nutrients, foremost with glucose. Therefore, during pregnancy, maternal insulin resistance arises, which elevates maternal blood glucose levels, and consequently ensures an adequate glucose supply for the developing fetus. At the same time, maternal β-cell mass and function increase to compensate for the higher insulin demand. These adaptations are also regulated by the endocrine function of the placenta. Excessive insulin resistance or the inability to increase insulin production accordingly disrupts physiological modulation of pregnancy mediated glucose metabolism and may cause maternal gestational diabetes (GDM). A growing body of evidence suggests that this adaptation of maternal glucose metabolism differs between pregnancies carrying a girl vs. pregnancies carrying a boy. Moreover, the risk of developing GDM differs depending on the sex of the fetus. Sex differences in placenta derived hormones and bioactive proteins, which adapt and modulate maternal glucose metabolism, are likely to contribute to this sexual dimorphism. This review provides an overview on the adaptation and maladaptation of maternal glucose metabolism by placenta-derived factors, and highlights sex differences in this regulatory network.