In Vitro and in Vivo Evaluation of Vascular Networks Generated from iPSC-Derived Endothelial Cells

Vascularization is critical for the survival of engineered tissues post implantation. It has been previously shown that biomaterials containing preformed networks can anastomose to host vasculature following implantation. However, the optimal source of cells for vascularization for clinical use remains elusive. In this study, vascular networks were generated from endothelial cells derived from human induced pluripotent stem cells (iPSCs). Network formation by iPSC-ECs within fibrin gels was investigated in a mesenchymal stem cell (MSC) co-culture spheroid model. Statistical design of experiments (DOE) techniques were applied to identify optimal conditions for vessel-like network formation. The prevascularized units were then combined with hydroxyapatite nanoparticles to develop a vascularized composite hydrogel that was implanted in a rodent critical sized cranial defect model. Immunohistological staining for human-specific CD31 at week 1 indicated the presence and maintenance of the implanted vessels. Erythrocytes in the vessel lumen further suggests anastomosis of vessels with host vasculature. At week 8, isolectin staining indicated functionality of the human implanted vessels. There was a slight increase in bone volume in prevascularized scaffolds compared to MSC-only scaffolds. However, a pronounced increased in bone regeneration with prevascularization was not observed. These results show that prevascularized scaffolds can be generated from ECs derived from iPSC and that the networks survive and inosculate with the host post implantation in a bone model.