Expression patterns of Notch receptors and their ligands Jagged and Delta in human placenta.

The establishment of an appropriate fetomaternal vessel system is a prerequisite for prevention of pregnancy associated pathologies. Notch receptors and ligands are manifoldly involved in vascular development and angiogenesis. To further characterize the process of human placental vasculo- and angiogenesis we investigated the expression pattern of Notch receptors and their ligands during pregnancy. Real time RT-PCR, immunohistochemistry and flow cytometry analysis were performed in early (6-12) weeks of gestation (w.o.g.) and late placenta (37-41 w.o.g.). To specify the exact cellular localization immunofluorescent labelling of epithelial and endothelial cells (EC), respectively, with cytokeratin-7 and vonWillebrand factor (vWF) was done. One placenta from a patient with Alagille syndrome (AGS) was examined with real time RT-PCR and immunohistochemistry. The receptors Notch2, -3, -4 and their ligands Jagged1, -2 and Delta1, -4 were detected at both the mRNA and protein level in early and late placenta. Notch1 was only detected at protein level. The expression was found mainly in the stromal compartment: placental EC expressed Notch1, Delta4, Jagged1 and Delta1. A strong Jagged1 expression was found in the endothelium of arteries and veins supporting a role in differentiation of capillaries. Hofbauer cells (HC) primarily displayed the receptors Notch2, -3 and -4. Placental stromal cells (SC) were positive for Jagged2. The syncytiotrophoblast (ST) and cytotrophoblast (CT) cells revealed a weak but detectable co-localization with cytokeratin-7 and Notch1, -3 and Delta1. These results were verified by flow cytometry of freshly isolated placental cells of placental tissue. Interestingly Jagged1 expression was absent in endothelial cells from an AGS placenta. The Notch receptors and their ligands are expressed in human placental ST, CT, EC, SC and HC. The distribution pattern of Notch receptors and their ligands suggests their involvement in the process of placental vasculo- and angiogenesis via cell-cell communication between trophoblast, -stroma and endothelial cells.