Light and electron microscopic study of placental tissue in women suffering from severe preeclampsia

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Abstract

Introduction

Preeclampsia is a serious disease and a major contributor to maternal and fetal morbidity and mortality worldwide. It is characterized by hypertension and proteinuria after 20 weeks of gestation.

Aim of the work

This study was designed to investigate placental tissue in women suffering from severe preeclampsia compared with normal controls using light and electron microscopes.

Patients and methods

A total of 25 pregnant women were enrolled in this study. Twenty of them were diagnosed as having severe preeclampsia, and five were clinically normal and considered as the control group. Placental specimens were obtained immediately after either vaginal delivery or cesarean section and processed for H&E and Masson's trichrome stains, as well as for immunohistochemical stains for Bcl-2 for detection of apoptosis, vascular endothelial growth factor (VEGF), and for transmission electron microscopy.

Results

Light microscopic examination of the preeclamptic group showed hyaline degeneration in the core of some chorionic villi, numerous syncytial knots, and apparent decrease in the thickness of the trophoblastic lining of the villi. Villous stroma revealed significant increase in the amount of collagen fibers around dilated and congested fetal capillaries, with apparent increase in fibroblast-like cells. Immunohistochemical study revealed significant increase in the expression of Bcl-2 by syncytiotrophoblastic cells. Moreover, significant decrease in the expression of VEGF was noticed by syncytiotrophoblasts, stromal cells, and endothelial cells. By transmission electron microscopy, syncytiotrophoblastic cells were seen to reveal short, distorted, or even absent microvilli, degenerated mitochondria, many cytoplasmic vacuoles, and condensed, fragmented, apoptotic nuclei. There was a gap between the capillary endothelium and the overlying trophoblastic layer. The trophoblastic basement membrane was thick and irregular. Dilated fetal capillaries were lined by swollen endothelial cells that had an irregular hyperchromatic nuclei.

Conclusion

Apoptotic changes in syncytiotrophoblastic cells and significant decrease in VEGF expression might be responsible for symptoms of severe preeclampsia.

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