Tubulogenesis of co-cultured human iPS-derived endothelial cells and human mesenchymal stem cells in fibrin and gelatin methacrylate gels.

Here, we investigate the tubulogenic potential of commercially-sourced iPS-ECs with and without supporting commercially-sourced hMSCs within 3D natural fibrin or semi-synthetic gelatin methacrylate (GelMA) hydrogels. We developed a selectable dual color third generation lentiviral reporter (hEF1α-H2B-mOrange2-IRES-EGFP PGK-Puro) to differentially label the nucleus and cytoplasm of iPS-ECs which allowed real-time tracking of key steps of vascular morphogenesis such as vacuole formation and coalescence to form shared multicellular lumens. We implement 3D quantification of the network character and validate that transduced and untransduced iPS-ECs can form tubules in fibrin with or without supporting hMSCs. In addition to natural fibrin gels, we also investigated tubulogenesis in GelMA, a semi-synthetic material that has received increased interest due to its ability to be photopatterned and 3D printed, and which may thus boost development of complex 3D models for regenerative medicine studies. We find that iPS-ECs alone have a muted tubulogenic response within GelMA, but that their tubulogenic response is enhanced when they are co-cultured with a small fraction of hMSCs (2% of total cells). Our work bolsters previous findings by validating established tubulogenic mechanisms with commercially available iPS-ECs, and we expect our findings will benefit biologic studies of vasculogenesis and will have applications in tissue engineering to pre-vascularize tissue constructs which are fabricated with advanced photopatterning and three-dimensional printing.