Abstract 897: Alliance of Blood Derived Endothelial Cells and Adipose Stromal Cells in Human Vasculogenesis
Introduction Both Endothelial progenitor cells (EPC) and adipose stromal cells (ASC) are under investigation as therapies for cardiovascular diseases. Both cell types are capable of modulating vascular assembly and are, thereby, capable of directly promoting revascularization of ischemic tissues. We have shown that EPC differentiate into endothelial cells to form small vessels, whereas ASC have pericytic properties and naturally stabilize vessels. In this study we tested the possibility that ASC would interact with EPC to assemble de novo vessels in collagen in an in vivo chimeric implant.
Methods and Results Collagen implants embedded with either umbilical cord blood EPC or adult ASC or a 4:1 mixture of both (2x106 cells/ml) were implanted subcutaneously into NOD/SCID mice. After 14 d implants were harvested and evaluated by immunohistochemistry. There was a pronounced difference among the groups in vascular network assembly. The majority of vessels formed in the EPC and ASC monocultures were small capillaries bounded by a single endothelial layer. Conversely, 100% of the plugs embedded with both cell types were highly invaded with multilayered arteriolar vessels. The density of the CD31+ vessels in the EPC and co-culture plugs was 26.6 ± 5.8 and 122.4 ± 9.8 per mm2, respectively. No CD31+ cells of human origin were detected in the ASC monocultures, indicating that ASC, which do not express this EC-specific marker, engage murine EC or form pseudovessels in this system. The density of α-SMA+ vessels with lumens per mm2 was 13.1 ± 3.6 (EPC), 10.2 ± 3.5 (ASC) and 124.7 ± 19.7 (co-culture). The total overlap of CD31+ and SMA+ vessels demonstrates that mature, multilayered conduits were formed with the co-culture. Moreover, the majority of these vessels were filled with erythrocytes (92.5 ± 16.2 per mm2), indicating inosculation with the native vasculature, which was confirmed by ultrasound with echogenic microbubbles and persisted to at least 4 months.
Conclusion This study is the first to demonstrate that non-transformed human EPC and ASC cooperatively form mature and stable vasculature with subsequent functional integration into a host vasculature system.