Introduction
Pre-eclampsia (PE) is a systemic vascular Fdisorder affecting 4-5% of
pregnant women globally1. PE is a leading cause of
maternal and foetal morbidity and mortality, and confers a life- long
risk to maternal and infant’s cardiovascular
health2-5. Classically, PE manifests as new-onset
hypertension and proteinuria after 20 weeks of gestation6. Nevertheless, symptoms, severity, time of onset,
and outcome can vary significantly and early diagnosis remains
challenging 6, 7.
The wide range of clinical phenotypes makes PE more fitting to be a
syndrome instead of a single disease. Especially the distinction early-
and late-onset PE (EO-PE and LO-PE) is frequently applied and both are
likely to have distinct aetiologies8, 9. Nonetheless,
the exact definition of EO-PE and LO-PE is controversial. The current
stratification only focusses on time of onset of clinical symptoms,
gestational age at time of birth, or a combination of these, without
referring to underlying causes6, 9, 10.
Quantifying altered placental morphology in different clinical
presentations of PE is key to distinguish the clinical syndrome into
distinct pathological phenotypes. Currently, 2D histological evaluation
is the gold standard for placental investigation11-13.
Yet, none of the histological findings are specific for PE, i.e., are
also observed in other placental syndromes like intra-uterine growth
restriction (IUGR)14-16.
More advanced imaging methods such as confocal microscopy have been used
for imaging terminal villous vasculature17-20.
However, the villous tree is built up of stem villi (of which the
diameter can be up to 3000 µm), intermediate villi, and terminal villi21.
Multiphoton microscopy (MPM) is a tomographic (3D imaging) technique
with subcellular resolution. It is based on multiphoton excited
fluorescence and features deep tissue penetration (up to 1
μm)22. Therefore, thick tissue slabs (containing
different components of the villous tree) can be visualized, closely to
their native form. Moreover, MPM is efficient in exciting
autofluorescence signal, suitable for label free imaging of imaging
cytoplasm and connective tissue even in vivo23.
MPM has been applied to investigate placental membrane
architecture24, 25. But, to our knowledge, phenotype
quantification of the villous tree and vasculature of healthy and PE
placentas with MPM has not been described yet. The aim of this study was
to develop a MPM placental imaging protocol and to demonstrate
quantifiable imaging targets. Quantification of these targets could aid
in a more unequivocal characterization of different PE subtypes and
improve disease stratification.