Regulation of the Matricellular Proteins CYR61 (CCN1) and NOV (CCN3) by Hypoxia-Inducible Factor-1α and Transforming-Growth Factor-β3 in the Human Trophoblast

Abstract

It is known that a hypoxic environment is critical for trophoblast migration and invasion and is fundamental for appropriate placental perfusion. Because cysteine-rich 61 (CYR61, CCN1) and nephroblastoma overexpressed (NOV, CCN3) are expressed in the extravillous trophoblast and expression levels are deregulated in preeclampsia, we investigated their regulation properties in first-trimester placental explants and in JEG3 choriocarcinoma cells upon a physiological low oxygen tension of 1–3%. In placental explants, both proteins were expressed in the extravillous trophoblast cells and were increased upon hypoxia. JEG3 cells revealed a significant up-regulation of CYR61 and NOV intracellular as well as secreted protein upon hypoxic treatment accompanied by the stabilization of the hypoxia-inducible factor-1α (HIF-1α). Treatment with dimethyloxalylglycine to mimic hypoxia and silencing of HIF-1α using small interfering RNA revealed that only the increase in intracellular protein expression seems to be dependent on HIF-1α but obviously not the secretion process. Moreover, recombinant TGF-β3 was able to further enhance the amount of intracellular CCN proteins as well as secreted CYR61 levels under hypoxia. These results indicate that low oxygen levels trigger elevation of intracellular as well as secreted CYR61 and NOV protein probably in two independent pathways. Addition of recombinant CYR61 and NOV proteins increases migration as well as invasion properties of JEG3 trophoblast cells, which strengthen their role in supporting trophoblast migration invasion properties. In summary, CYR61 and NOV are regulated by HIF-1α and TGF-β3 in the trophoblast cell line JEG3, and their enhanced secretion could be implicated in appropriate placental invasion.