3. 3D native villous tree organisation: altered surface-volume relations in pre-eclampsia
Villous 3D shapes were highly varying (Figures 3A-D). Depending on achievable imaging depth, linkages of terminal villi, intermediate villi, and stem villi, could be visualised. The investigated EO-PE placenta had large knob-like villous endings (Figure 3A) characteristic of PE placenta. These knob-terminals were not uncommon and frequently present on villous tips (Figure S7). Term control placenta had shorter but highly condensed villi (Figure 3B), while branching appeared excessive in an IUGR case (Figure 3C). Notable is that the LO-PE placenta had highly varying regions with limited branching (Figure 3D) and highly branched villi (Video S1). Segmentation procedures of intermediate and terminal villi are illustrated in Figures S8-S11.
Quantitative results indicated that villous surface area increases disproportionally to volume in investigated PE placentas (Figure 3E). Diffusion surface area and villous volume had a positive linear relation in term control placenta, whereas in PE a linear relation between surface area and volume was absent (Figures 3E, 3F).
The SA/vol ratio provides a measure for easiness of diffusive transport and branching is a biological mechanism to increase the SA/vol ratio. No significant difference was found between the SA/vol ratio of chorionic villi of control- and PE or IUGR placenta (Figure 3G). However, the villous SA/vol ratio tended to be highest in LO-PE placenta, which suggests increased villous branching compared to term placenta (Figure 3G). Notably, the villous SA/vol ratio was lowest in the term IUGR placenta (Figure 3G), while villi appeared highly branched (Figure 3C).