Vascular biomechanics in full flow

Pulsatile blood flow is driven by the heart and is a universal feature of vertebrate blood systems. However, the mechanisms controlling blood flow propagation in the embryo, while heart maturation is ongoing, are poorly understood. Here, Julien Vermot and co-workers examine vascular hydrodynamics and biomechanics in zebrafish embryos (p. 4426). Using high temporal resolution imaging together with an optical tweezer-based approach, the authors characterise the flow within the embryonic vascular network. They show that strong flow rectification occurs between branches of the network, suggesting that an additional force is generated within the network. Based on the observed movement of blood cells within the embryonic artery, the authors postulate that elasticity of the network is essential for mediating this effect. Following this, they develop a mathematical model of flow within the network and propose that the dorsal aorta acts as a capacitor that inflates and deflates in response to heartbeats. They propose that this capacitive mechanism has a major role in setting early flow propagation and reducing embryonic heart effort.