PHLDA2 expression and promoter methylation in placental trophoblasts: Associations with preeclampsia development

Preeclampsia (PE) is an idiopathic and life-threatening pregnancy-related disease. Alterations to DNA methylation in imprinted genes may play a crucial role in the dysfunction of trophoblast cells and PE.

Herein, we sought to elucidate the characteristics of PHLDA2 in placental trophoblasts and its underlying mechanisms in pregnant women with PE. Between January 2019 and December 2021, the clinical data and placental tissue samples from 15 PE cases and 15 control women who underwent obstetric examination were collected. Immunohistochemistry, qRT-PCR, WB and pyrosequencing were used to detect and compare the expression and methylation status of imprinted gene PHLDA2 in placental tissues of the two groups.

The expression levels of PHLDA2 mRNA and protein were significantly higher in the placental tissue of PE patients than those of healthy controls during the third trimester (P = 0.001). Additionally, PHLDA2 expression levels were evaluated in four trophoblast cell lines, with the JEG-3 line showing the lowest expression of PHLDA2. Notably, the JEG-3 line demonstrated a significantly faster rate of proliferation compared to the other three cell lines. When the PHLDA2 was overexpressed in JEG-3 cells, the proliferative proteins were significantly reduced, while the expression levels of apoptosis-related proteins p27 and cleaved-caspase3 were significantly increased. In addition, pyrosequencing showed that the methylation levels of the PHLDA2 promoter region were significantly lower in PE placentas than in controls.

The hypomethylation status of the PHLDA2 promoter is associated with its altered expression in PE placentas, suggesting a potential role in the condition's pathogenesis.