Background: Recently we have shown that the matricellular CCN3 protein expressed in invasive extravillous trophoblast cells (EVTs) is decreased in early-onset pre-eclampsia and is regulated by oxygen tension. Pathogenesis of pre-eclampsia relies on a shallow invasion of EVTs into the spiral arteries, which leads to hypoxia accompanied by uteroplacental insufficiency. Here we investigated the function of glycosylated and non-glycosylated CCN3 protein on cell growth as well as migration and invasion properties of the malignant trophoblast cell line Jeg3 which is a widely used model for the invasive trophoblast.
Methods and results: Stable transfection of Jeg3 choriocarcinoma cells with full length CCN3 resulted in high expression of secreted glycosylated and cellular non-glycosylated CCN3. These cells revealed significantly reduced growth in cell numbers combined with a significantly increased migratory and invasive capacity. Matrix metalloprotease (MMP)-2 and MMP-9 activities were enhanced dependent on CCN3 expression, which could be confirmed by CCN3 knockdown studies. Using recombinant glycosylated and non-glycosylated CCN3, we revealed that CCN3 decreased growth in Jeg3 cell numbers independent of its glycosylation status, whereas only non-glycosylated CCN3 was able to enhance migration and invasion properties.
Conclusions: The present results suggest that CCN3 protein regulates the decrease in Jeg3 cell numbers independent of its glycosylation status, whereas migratory and invasive properties are influenced only by non-glycosylated CCN3. An impaired balance in the expression of glycosylated and non-glycosylated CCN3 could contribute to the shallow invasion of EVTs observed in pre-eclampsia.