Three-dimensional Rendering and Analysis of Immunolabeled, Clarified Human Placental Villous Vascular Networks.

Nutrient and gas exchange between mother and fetus occurs at the interface of the maternal intervillous blood and the vast villous capillary network that makes up much of the parenchyma of the human placenta. The distal villous capillary network is the terminus of the fetal blood supply after several generations of branching of vessels extending out from the umbilical cord. This network has a contiguous cellular sheath, the syncytial trophoblast barrier layer, which prevents mixing of fetal blood and the maternal blood in which it is continuously bathed. Insults to the integrity of the placental capillary network, occurring in disorders such as maternal diabetes, hypertension and obesity, have consequences that present serious health risks for the fetus, infant, and adult. To better define the structural effects of these insults, a protocol was developed for this study that captures capillary network structure on the order of 1 - 2 mm3 wherein one can investigate its topological features in its full complexity. To accomplish this, clusters of terminal villi from placenta are dissected, and the trophoblast layer and the capillary endothelia are immunolabeled. These samples are then clarified with a new tissue clearing process which makes it possible to acquire confocal image stacks to z- depths of ~1 mm. The three-dimensional renderings of these stacks are then processed and analyzed to generate basic capillary network measures such as volume, number of capillary branches, and capillary branch end points, as validation of the suitability of this approach for capillary network characterization.

Hemodynamic analysis of blood flow in umbilical artery using computational modeling.

The umbilical cord is the crucial pathway for blood flow between the fetus and the placenta. Umbilical coiling and length have been separately linked to adverse clinical outcomes; however, the effects of variations of these parameters on umbilical arterial blood flow are not well understood. Using 3D computational model, we studied the individual and combined effects of umbilical coiling index, cord length and arterial diameter on umbilical artery hemodynamics. We found that specific combinations of umbilical coiling index, cord length and arterial diameter yielded pressure and flow drops incompatible with fetal life. Such models are useful as hypothesis-developing tools.

Clarification and 3-D visualization of immunolabeled human placenta villi.

We report here the successful 3D visualization of human placenta villous structures on the order of ∼1 mm3 by a combination of immunolabeling, rapid tissue clarification and laser scanning confocal microscopy. The resultant image sets exhibit a complex arrangement of villi and their contained vasculature that mirrors their arrangement in situ.