Pathophysiology of placentation abnormalities in pregnancy-induced hypertension

Abstract

During embryogenesis and development, the fetus obtains oxygen and nutrients from the mother through placental microcirculation. The placenta is a distinctive organ that develops and differentiates per se, and that organizes fetal growth and maternal condition in the entire course of gestation. Several life-threatening diseases during pregnancy, such as pregnancy-induced hypertension (PIH) and eclampsia, are closely associated with placental dysfunction. Genetic susceptibilities and poor placentation have been investigated intensively to understand the pathophysiology of PIH. It is currently thought that “poor placentation hypothesis”, in which extravillous trophoblasts fail to invade sufficiently the placental bed, explains in part maternal predisposition to this disease. Cumulative studies have suggested that hypoxic micromilieu of fetoplacental site, shear stress of uteroplacental blood flow, and aberrantly secreted proinflammatory substances into maternal circulation synergistically contribute to the progression of PIH. For example, soluble form of vascular endothelial growth factor receptor-1 (sVEGFR-1) and soluble form of CD105 are elevated in circulation of PIH mothers. However, it remains to be poorly understood the pathological events in the placenta during the last half of gestation as maternal systemic disorders get worse. For better understanding and effective therapeutic approaches to PIH, it is important to clarify pathological course of PIH-associated changes in the placenta. In this review, current understanding of placental development and the pathophysiology of PIH placenta are summarized. In addition, recent findings of vasoactive signalings in PIH and rodent PIH models are discussed.

Keywords:

• pregnancy-induced hypertension
• preeclampsia
• placenta
• neovascularization
• intrauterine growth restriction
• transgenic mice
• renin –angiotensin-system

Acknowledgements

The protocol to obtain tissue samples was approved by the review boards of Sapporo General Hospital and Chiba University Hospital. The authors thank to Drs T Takenouchi, H Hareyama, H Usui, M Shozu, and Y Nakatani for providing human samples, and the members of Fukamizu laboratory and Dr Y Yonemitsu for discussion. This work is supported by Grant-in-Aid for Scientific Research (S) (AF), Grant-in-Aid for Exploratory Research (AF), and Grant-in-Aid for Scientific Research (C) (MF) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.