Dysregulation of promyelocytic leukemia (PML) protein expression in preeclamptic placentae.

Promyelocytic leukemia (PML) protein is a nucleoprotein that can regulate a variety of cellular stress responses. The aim of this study was to determine qualitative and quantitative changes in PML expression in preeclamptic placentae. Immunoblot, qRT-PCR and immunohistochemistry techniques were used to determine PML gene expression and localization in normal (n=6) and preeclamptic (n=6) placentae and primary cells. PML protein was immunolocalized within nuclei of villus mesenchyme, but largely absent in trophoblast nuclei, with a trend for increased PML reactivity in preeclamptic placenta. Immunoblot analyses of nuclear extracts confirmed relative increases (~3 fold) of PML expression in preeclamptic placentae (p<0.05). Conversely, less PML mRNA (~2 fold) was detected in preeclamptic versus normal placental samples. In vitro, PML expression could be increased by hypoxia in cultured endothelial cells but not trophoblast. Increased PML protein expression in preeclamptic villi suggests it could contribute to decreased vascularity and placental growth and/or function.