Imaging and quantification of placental terminal villi microvasculature and nuclear characteristics in preeclampsia

Juul Bierens, C. Severens‐Rijvers, Sven Hildebrand, Marc van Zandvoort, Salwan Al‐Nasiry, Dimitrios Kapsokalyvas

Globally, at least 10 % of maternal deaths, caused by obstetric complications during pregnancy, are linked to preeclampsia or eclampsia. Preeclampsia-induced placental hypoxia leads to vascular injury and syncytial knot formation in terminal villi. Early delivery of preeclampsia placentas complicates comparisons with normotensive term placentas, while the placenta's non-planar structure limits the effectiveness of 2D histology for vascular analysis. This study used multiphoton microscopy to quantify 3D morphological differences in terminal villi between late-onset preeclampsia and control pregnancies. 7 late-onset preeclampsia (Gestational age: 37.3 weeks) and 10 control (Gestational age: 38.3 weeks) placentas were stained for nuclei and vasculature, optically cleared using ethyl-cinnamate, imaged with multiphoton microscopy, and analysed semi-automatically. Image quantification revealed a 42 % decrease in vascular fraction and a 97 % increase in syncytial knot density in late-onset preeclampsia samples, both statistically significant. No differences were observed in surface area-to-volume ratios, individual syncytial knot volume, or microvascular characteristics, including branchpoint density, vessel length, branching angle, straightness, and diameter. By analysing placentas at comparable gestational ages, we demonstrated that late-onset preeclampsia is characterized by decreased vascular content and increased syncytial knot density, while individual syncytial knot size and microvascular architecture remain unchanged. These findings enhance our understanding of late-onset preeclampsia pathophysiology and could provide a basis to distinguish late-onset preeclampsia from other phenotypes, such as early-onset preeclampsia, highlighting potential differences in disease mechanisms.