Hypoxia inducible factor 1 alpha regulates matrigel-induced endovascular differentiation under normoxia in a human extravillous trophoblast cell line.

Extravillous trophoblast (EVT) cells mimic endothelial cells during angiogenesis, inducing remodeling of the spiral arteries that increases blood flow toward the intravillous space. We have previously shown that signals involving the vascular endothelial growth factor (VEGF) axis are essential for endovascular differentiation through integrin signaling from the extracellular matrix: This was accomplished with use of the human EVT cell line TCL1, which shows tube formation that specifically recalls morphological changes in endothelial cells. To investigate endovascular differentiation in EVT further, we investigated the role of hypoxia inducible factor (HIF)1A, a subunit of HIF1 transcription factor that regulates not only adaptive responses to hypoxia, but also many cellular functions under normoxia, which was up-regulated in DNA microarray analysis during matrigel-induced endovascular differentiation under normoxia. HIF1A induces VEGF and ITGAV/ITGB3 aggregation, actions known to be important for cellular survival and endovascular differentiation in EVT. Inhibition of HIF1A up-regulation using siRNA introduction or chemical inhibition suppressed hypoxia-responsive element transcriptional activity, VEGF induction, ITGAV/ITGB3 aggregation accompanied by the inhibition of tube formation in TCL1 cells. These results suggest that HIF1A has a crucial role in regulating EVT behavior including matrigel-induced endovascular differentiation under normoxia.