Integrating Engineered Macro Vessels with Self-assembled Capillaries in 3D Implantable Tissue for Promoting Vascular Integration In-vivo

Fabrication of a functional hierarchical vascular network remains an unmet need for cultivation and transplantation of 3D engineered tissues. In this work, an effective approach was developed to fabricate a functional, perfusable and biocompatible, multi-scale vascular network (MSVT) within thick, implantable engineered tissues. Using a templating technique, macro-vessels were patterned in a 3D biodegradable polymeric scaffold seeded with endothelial and support cells within a collagen gel. The lumen of the macro-vessel was lined with endothelial cells, which further sprouted and anastomosed with the surrounding self-assembled capillaries. Anastomoses between the two-scaled vascular systems displayed tightly bonded cell junctions, as indicated by vascular endothelial cadherin expression. Moreover, MSVT functionality and patency were demonstrated by dextran passage through the interconnected hierarchical vasculature. Additionally, physiological flow conditions were applied with home-designed flow bioreactors, to achieve a MSVT with a natural endothelium structure. Finally, implantation of a multi-scale-vascularized graft in a mouse model resulted in a clear beneficial effect, as reflected by extensive host vessel penetration into the graft and an increase in blood perfusion via the engineered vessels as compared to control microscale-vascularized graft. Designing and fabricating such multi-scale vascular architectures within 3D engineered tissues is essential, both for in-vitro models and for therapeutic translation research.