Endothelial mechanotransduction in cardiovascular development and regeneration: emerging approaches and animal models

Abstract

Living cells are exposed to multiple mechanical stimuli from the extracellular matrix or from surrounding cells. Mechanoreceptors are molecules that display status changes in response to mechanical stimulation, transforming physical cues into biological responses to help the cells adapt to dynamic changes of the microenvironment. Mechanical stimuli are responsible for shaping the tridimensional development and patterning of the organs in early embryonic stages. The development of the heart is one of the first morphogenetic events that occur in embryos. As the circulation is established, the vascular system is exposed to constant shear stress, which is the force created by the movement of blood. Both spatial and temporal variations in shear stress differentially modulate critical steps in heart development, such as trabeculation and compaction of the ventricular wall and the formation of the heart valves. Zebrafish embryos are small, transparent, have a short developmental period and allow for real-time visualization of a variety of fluorescently labeled proteins to recapitulate developmental dynamics. In this review, we will highlight the application of zebrafish models as a genetically tractable model for investigating cardiovascular development and regeneration. We will introduce our approaches to manipulate mechanical forces during critical stages of zebrafish heart development and in a model of vascular regeneration, as well as advances in imaging technologies to capture these processes at high resolution. Finally, we will discuss the role of molecules of the Plexin family and Piezo cation channels as major mechanosensors recently implicated in cardiac morphogenesis.

Keywords: Light sheet microscopy; Mechanotransduction; Notch; Shear stress; Trabeculation; Zebrafish.

Fig. 1

Adult zebrafish anatomy. (A) The heart is visible at ~1 mm below the skin. (B) Adult zebrafish heart has one atrium (A) and one ventricle (V). This image also shows the morphology of the trabecular zone (Tr). (C) The adult zebrafish ECG reveals resembling features in terms of atrial activation and ventricular depolarization with the human ECG. P wave, atrial contraction; QRS, ventricular contraction; T wave, ventricular repolarization.

Fig. 2

Summary of major events in zebrafish heart development.

Fig. 3

Spatiotemporal variations in wall shear stress modulate Notch during ventricular wall formation. A small area of the zebrafish ventricle is enlarged to visualize the architecture of the ventricular wall, which in early stages is mostly exposed to pulsatile shear stress (PSS). The development of ridges in the trabecular zone (TZ) promotes flow recirculation, generating oscillatory shear stress (OSS) in the trabecular grooves, which, in turn, induces Notch activity at the bottom of the grooves. PSS-induced endocardial Notch and OSS-mediated Notch in the grooves coordinate ventricular trabeculation. While endocardial Notch activates myocardial Erbb2 expression to initiate trabecular ridge formation, Notch activity in the grooves may cause lateral inhibition of Erbb2 expression and resultant trabeculation. Trabeculae may serve to dissipate kinetic energy, thus preventing ventricular remodeling and dysfunction. CZ: compact zone.

Fig. 4

(A) Plexin D1, through its interaction with Semaphorin 3E, inhibits the Dll4-Notch pathway, that it is induced by VEGF. VEGFR2 is able to induce the expression of Plexin D1. (B) Binding of Plexin D1 to Semaphorin 4A increases VEGFR2 expression.