Co-culture of primary neural progenitor and endothelial cells in a macroporous gel promotes stable vascular networks in vivo.

Most tissues cannot survive without microvascular networks. In many cases, the host cannot vascularize implanted tissues, motivating the need for implantable vascular networks for tissue engineered grafts. However, engineering microvascular networks that are stable and functional for long times has proven challenging. The co-culture of neural progenitor cells with endothelial cells may lead to long term, functional microvascular networks. Ideally, these networks should be made from primary cells to avoid the potential safety concerns associated with immortalized or genetically-engineered cells. Thus, we have investigated and developed a paradigm for isolating and co-culturing primary rat endothelial cells and neural progenitor cells in biodegradable poly(ethylene glycol)/poly(L-lysine) macroporous hydrogels. The co-culture of these primary cells in the gels led to stabilization of vessels with no evidence of vessel regression even as far out as 6 weeks, the longest time point studied. Further more, the vessels contained host red blood cells, demonstrating they anastomosed with the host and were functional. Functional vessels were found throughout the implants, and no adverse effects such as clotting or thrombosis were observed. This work suggests that a co-culture of primary cells seeded in a macroporous hydrogel is a novel method to promote stable functional vascular networks which are critical for engineering complex tissues.