Studying the Effect of Local Geometry Combined With External Forces on Blood Vessels Sprouting

Mimicking the complex structure of native vascular networks in vitro requires understanding the governing factors of early tubulogenesis. Current vascularization protocols allow spontaneous formation of vascular networks; however, there is still a need to provide control over the defined network structure. Moreover, there is little understanding on sprouting decision, especially within 3D environments.
To study how different geometries affect vessel sprouting, our lab has established a new scaffolds system combined with a novel two-step seeding protocol. This protocol combines endothelial cells and support cells (SCs) which self-assemble into a vascularized tissue under the constraints of the geometry in which they are seeded. The designed system had demonstrated how endothelial cells first followed the compartment geometry and subsequently, sent sprouts in specific directions responding to the initial geometry. Tracking vessel migration and SCs distribution confirmed that sprouts formation was favorable toward opposing corners, where the density of SCs is the highest, providing the highest levels of angiogenic factors. The main drawback of the presented system is the scaffold mechanical inflexibility, which prevents applying external forces without damaging the scaffolds. Here, we suggest a novel technology of cells embedded in mechanically flexible hydrogels in highly precise geometries to study the combined effect of specific geometry and mechanical cues on the development and orientation of sprouting blood vessels in 3D environments. This work will provide a new insight regarding vessel sprouting decisions and how can we manipulate it for creating tissue constructs with specifically designed hierarchical vascular networks.