Distinct molecular processes in placentae involved in two major subtypes of preeclampsia

Patients with preeclampsia display a spectrum of onset time and severity of clinical presentation, yet the underlying molecular bases for the early-onset and late-onset clinical subtypes are not known. Since the root cause of PE is thought to be located in the placentae, we carried out RNA-seq on 65 high-quality placenta samples, including 33 from 30 patients and 32 from 30 control subjects, to search for molecular features. We identified two functionally distinct sets of dysregulated genes in two major subtypes: metabolism-related genes, notably transporter genes, in early-onset severe preeclampsia and immune-related genes in late-onset severe preeclampsia, while the late-onset mild preeclampsia could not be distinguished from normal controls. A small number of dysregulated transcription factors may drive the widespread gene dysregulation in both early-onset and late-onset patients. These results suggest that early-onset and late-onset severe preeclampsia have different molecular mechanisms, whereas the late-onset mild preeclampsia may have no placenta-specific causal factors.