Physical and geometric determinants of transport in feto-placental microvascular networks

TL;DR

This study develops a geometric and physical framework to understand how the structure of fetal capillary networks in the human placenta influences solute exchange, integrating image analysis, fluid dynamics, and algebraic modeling.

Contribution

It introduces a simple algebraic model linking placental microvascular geometry to transport capacity, accounting for flow, diffusion, and nonlinear blood rheology.

Findings

Geometric features predict transport efficiency across different solutes.

Transitions between flow- and diffusion-limited transport are characterized.

The framework can assess robustness and be applied to other microvascular systems.

Abstract

Across mammalian species, solute exchange takes place in complex microvascular networks. In the human placenta, the primary exchange units are terminal villi that contain disordered networks of fetal capillaries and are surrounded externally by maternal blood. Here we show how the irregular internal structure of a terminal villus determines its exchange capacity for a wide range of solutes. Distilling geometric features into three scalar parameters, obtained from image analysis and computational fluid dynamics, we capture archetypal features of the the structure-function relationship of terminal villi using a simple algebraic approximation, revealing transitions between flow- and diffusion-limited transport at vessel and network levels. Our theory accommodates countercurrent effects, incorporates nonlinear blood rheology and offers an efficient method for testing network robustness. Our results show how physical estimates of solute transport, based on carefully defined geometrical statistics, provide a viable method for linking placental structure and function, and offer a framework for assessing transport in other microvascular systems.