Mechanical regulation of vascular network formation in engineered matrices

Generation of vessel networks within engineered tissues is critical for integration and perfusion of the implanted tissue in vivo. The effect of mechanical cues in guiding and stabilizing the vessels has begun to attract marked interest. This review surveys the impact of mechanical cues on formation of vascular networks in 2D and 3D gel matrices. We give less emphasis to regulation of endothelial monolayers and single endothelial cells. Several vascularization models have consistently found that the stress generated in the gel, and encountered by embedded cells, control various aspects of vascular network formation, including sprouting, branching, alignment, and vessel maturation. This internal stress is generated by cell contractile forces, and is balanced by gel stiffness and boundary constrains imposed on the gel. Actin and myosin II are key molecular players in controlling initiation of vessel sprouting and branching morphogenesis. Additionally, the impact of external mechanical cues on tissue vascularization, and studies supporting the notion that mechanical forces regulate vascularization in the live animal are reviewed. (C) 2015 Elsevier B.V. All rights reserved.