Changes in Vascular Smooth Muscle and Collagen Content in Placental Vessels in Preeclampsia [04L]

Abstract

INTRODUCTION: Preeclampsia results in part from abnormal myometrial invasion by placental spiral arteries. It is unknown if and how fetal vessels remodel to compensate for these changes. We sought to characterize preeclampsia-associated vascular remodeling by comparing vessels within villi of placentas collected from preeclamptic and normotensive patients. METHODS: Carilion Clinic IRB approval was obtained prior to patient enrollment. Singleton pregnancies complicated by preeclampsia and normotensive controls were identified on Labor and Delivery. Placental biopsies were collected following delivery. Smooth muscle (alpha-SMA) and Type III collagen (COLIII) were identified by immunostaining of cryostat sections. Confocal microscopy was used to measure areas of alpha-SMA and COLIII positivity surrounding vessels. Ratios of alpha-SMA or COLIII positivity to vessel area were calculated. These ratios, which represent relative smooth muscle and collagen content, were compared between vessels from preeclamptic and normotensive placentas. RESULTS: Measurements from 342 vessels from 10 placentas (from five preeclamptic patients and five controls) were included in this analysis. Compared to vessels within placentas of normotensive patients, placental vessels of preeclamptic patients demonstrated a significantly reduced area of alpha-SMA positivity (2.48 vs 3.97; P=.008). A trend was seen towards decreased collagen surrounding vessels in preeclamptic placentas, though this was not statistically significant (4.33 vs 5.66; P=.054). CONCLUSION: Preeclampsia is associated with a decrease in vascular smooth muscle within placental villi and may be associated with decreased collagen content. This may represent a mechanism to increase transplacental flow of oxygen in the setting of impaired spiral artery remodeling, but further studies are needed to clarify this relationship.