Ultrastructural changes of the placenta in cases of preeclampsia

The placenta plays vital roles during fetal development and growth. The ultrastructure of the placenta together with remodeling of the uterine spiral arteries are very important to maintain the utero-placental blood flow. Preeclampsia (PE) is a multifactorial disorder with abnormal placentation affecting the mother and fetus. The aim of this study was to study the ultrastructural abnormalities of the placenta in cases of PE. The placentas of 10 PE women and 10 controls were studied. Women of PE group were delivered by caesarian section while seven control women were delivered vaginally, and three by caesarian section. Placental samples were studied both morphologically and histologically by light and transmission electron microscopy. Light microscopic study of control placentas showed numerous microvilli, few syncytial knots, thin-walled blood vessels. PE placentas showed reduced number of microvilli with numerous syncytial knots, thick-walled vessels, edematous spaces, fibrotic areas and fibrinoid degeneration. Electron microscopic study of the control placentas showed a thick layer of syncytiotrophoblast (Sy), numerous microvilli and a thin layer of cytotrophoblast (Cy). PE placenta showed hypertrophy of Cy with atrophy of Sy and scarce microvilli. The trophoblast showed edematous vacuoles and glycogen storage areas. The villous core had congested capillaries, edematous spaces, glycogen storage areas and widespread areas of fibrosis.

All the changes in PE placentas were attributed to hypoxia and oxidative stress and reduced utero-placental flow due to abnormal remodeling of the uterine spiral arteries that was aggravated by the thick placental barrier and the presence of edema, fibrosis and glycogen storage areas.