Perfusable branching microvessel bed for vascularization of engineered tissues

TLDR

Vascularization is essential for engineered tissue survival, and in vivo angiogenesis proceeds through endothelial proliferation, sprouting, interconnection, and lumen formation. The study aimed to engineer an organized capillary network anchored by an artery and a vein by mimicking natural angiogenesis. Directed capillary sprouting from vascular explants on micropatterned thymosin β4‑hydrogel substrates generated the network, which can be removed from the substrate and seeded with tissue‑specific cells. Capillary outgrowths linked parent explants by day 21, accelerated to 14 days with VEGF and HGF, and imaging confirmed lumenized endothelial tubules; tissues built around this vasculature exhibited improved functional properties, striations, and cell–cell junctions compared with non‑prevascularized controls.

Abstract

Vascularization is critical for the survival of engineered tissues in vitro and in vivo. In vivo, angiogenesis involves endothelial cell proliferation and sprouting followed by connection of extended cellular processes and subsequent lumen propagation through vacuole fusion. We mimicked this process in engineering an organized capillary network anchored by an artery and a vein. The network was generated by inducing directed capillary sprouting from vascular explants on micropatterned substrates containing thymosin β4-hydrogel. The capillary outgrowths connected between the parent explants by day 21, a process that was accelerated to 14 d by application of soluble VEGF and hepatocyte growth factor. Confocal microscopy and transmission electron microscopy indicated the presence of tubules with lumens formed by endothelial cells expressing CD31, VE-cadherin, and von Willebrand factor. Cardiac tissues engineered around the resulting vasculature exhibited improved functional properties, cell striations, and cell–cell junctions compared with tissues without prevascularization. This approach uniquely allows easy removal of the vasculature from the microfabricated substrate and easy seeding of the tissue specific cell types in the parenchymal space.