Novel 3D Microscopic Analysis of Human Placental Villous Trees Reveals Unexpected Significance of Branching Angles

Abstract

The villous trees of human placentas delineate the fetomaternal border and are complex three-dimensional (3D) structures. Thus far, they have primarily been analyzed as thin, two-dimensional (2D) histological sections. However, 2D sections cannot provide access to key aspects such as branching nodes and branch order. Using samples taken from 50 normal human placentas at birth, in the present study we show that analysis procedures for 3D reconstruction of neuronal dendritic trees can also be used for analyzing trees of human placentas. Nodes and their branches (e.g., branching hierarchy, branching angles, diameters, and lengths of branches) can be efficiently measured in whole-mount preparations of isolated villous trees using high-end light microscopy. Such data differ qualitatively from the data obtainable from histological sections and go substantially beyond the morphological horizon of such histological data. Unexpectedly, branching angles of terminal branches of villous trees varied inversely with the fetoplacental weight ratio, a widely used clinical parameter. Since branching angles have never before been determined in the human placenta, this result requires further detailed studies in order to fully understand its impact.

Novel 3D light microscopic analysis of IUGR placentas points to a morphological correlate of compensated ischemic placental disease in humans

“…The individual mean planar branching angle of villous branches in terminal position of the villous tree (i.e., at position bT0 according to our new classification 13 ; one value per investigated placenta) of the IUGR placentas was significantly larger statistically than in clinically normal placentas (p = 0.007; Fig. 3A ).…”

“…The 3D topology of the villous tree cannot reliably be analyzed on thin (2D) histological sections because the identification of villi as respectively terminal, intermediate or small peripheral stem villi is not unequivocally possible 12 . Furthermore, branching hierarchy, nodes and parameters like branching angles, tortuosity and branch length cannot be determined on thin (2D) histological sections at all 12 13 .…”

“…Recently, we introduced a novel light microscopic method for accurate 3D tracing, reconstruction, visualization and quantitative analysis of the topological position of branches and nodes of human placental villous trees 12 13 . This method allows instant determination of topological parameters such as hierarchy of branches, branching angles and length of branches of isolated peripheral villous trees.…”

“…1 . When applied to the analysis of a population of clinically normal placentas this novel method revealed a correlation between the feto-placental weight ratio at birth and villous branching angles of branches in terminal positions 13 .…”

“…Under careful dissection we prepared and isolated peripheral parts of villous trees and analyzed these tissue samples with the software, Neurolucida (MBF Bioscience, Williston, VT, USA). We used settings adapted to the requirements of villous branching 13 .…”