iPSC-derived endothelial networks accelerate vascularization but not bone regeneration.

Vascularization is critical for engineering mineralized tissues. It has been previously shown that biomaterials containing preformed endothelial networks anastomose to host vasculature following implantation. However, the networks alone may not increase regeneration. In addition, the a clinically applicable source of cells for vascularization are needed. 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 evaluated for its predicting capability during optimization of experimental parameters. The prevascularized units were 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. At 8 weeks the prevascularized systems resulted in higher vessel density over MSC-only scaffolds. The implanted vessels appeared to establish flow with host vasculature. While there was a slight increase in bone volume in prevascularized bone construct compared to MSC-only bone constructs, there was not a profound increase in bone regeneration. These results show that scaffolds with network structures can be generated from ECs derived from iPSC and that the networks survive and inosculate with the host post implantation in a bone model.