Systematic Analysis of the Smooth Muscle Wall Phenotype of the Pharyngeal Arch Arteries During Their Reorganization into the Great Vessels and Its Association with Hemodynamics.

Early outflow morphogenesis is a critical event in cardiac development. Understanding mechanical and molecular based morphogenetic relationships at early stages of cardiogenesis is essential for the advancement of cardiovascular technology related to congenital heart defects. In this study, we pair molecular changes in pharyngeal arch artery (PAA) vascular smooth muscle cells (VSMCs) with hemodynamic changes over the course of the same period. We focus on Hamburger Hamilton stage 24-36 chick embryos, using both Doppler ultrasound and histological sections to phenotype PAA VSMCs, and establish a relationship between hemodynamics and PAA composition. Our findings show that PAA VSMCs transition through a synthetic, intermediate, and contractile phenotype over time. Wall shear stress magnitude per arch varies throughout development. Despite distinct hemodynamic and fractional expression trends, no strong correlation was found between the two, indicating that WSS magnitude is not the main driver of PAA wall remodeling and maturation. While WSS magnitude was not found to be a major driver, this work provides a basic framework for investigating relationships between hemodynamic forces and tunica media during a critical period of development. Anat Rec, 302:153-162, 2019.