Endoplasmic reticulum stress-regulated high temperature requirement A1 (HTRA1) modulates invasion and angiogenesis-related genes in human trophoblasts

The pathogenesis of hypertensive disorder of pregnancy (HDP), which affects about 10% of pregnant women, is still incompletely understood. Our previous study showed that endoplasmic reticulum (ER) stress influences high-temperature requirement A serine peptidase 1 (HTRA1) expression and trophoblast invasion. However, the involvement of ER stress in the regulation of HTRA subtype expression and pathophysiology of HDP has not been characterized in extravillous trophoblasts (EVTs). To investigate this, HTR8/SVneo EVTs cell line was treated with the ER stress inducers Thapsigargin (Thap) or Tunicamycin (Tuni). Treatment with either Thap or Tuni inhibited trophoblast invasion, reduced HTRA1 and HTRA3 expression, but did not alter HTRA2 or HTRA4 expression. Knockdown of HTRA1 or HTRA3 also inhibited trophoblast invasion. Furthermore, treatment with either ER stress inducer or HTRA1 silencing increased the ratio of soluble fms-like tyrosine kinase-1/placental growth factor (sFLT1/PlGF), which is a marker of HDP. Immunohistochemical analysis revealed that HTRA1 is localized to EVTs and the endometrial decidua in the placenta of patients with HDP. These results suggest that factors that cause ER stress could result in the inhibition of EVTs invasion via HTRA1.