Abstract 17331: Active Role of Supporting Cells and Heterotypic Interactions with Endothelial Cells in 3 Dimensional Clusters Guide in vitro Angiogenesis
Introduction: Current methods of creating microvasculature in engineered tissue rely on the angiogenic properties of endothelial cells (ECs) and supporting cells (SCs), but yield a sparse network. Native vascular tissue fragments exhibit robust sprouting in gels in vitro. We hypothesized that 3D clusters of ECs and SCs, or engineered microvascular subunits (EMS) that are designed to replicate vascular tissue, would yield improved in vitro angiogenesis.
Methods: Human EMS with 600 ECs (coronary artery and umbilical vein), 200 SCs bone marrow mesenchymal stromal cells (MSCs), thymus MSCs, adipose MSCs, coronary and aorta smooth muscle cells) and the combination of both cell types were generated by hanging drop method, placed in fibrin, observed for sprouting and compared to monolayers of ECs and SCs. Angiogenic growth factor production and signal transduction molecule phosphorylation were measured. ECs and SCs were tracked to identify their contributions to sprouting.
Results: EMS sprouted within 24 hours while monolayers did not. Cell composition affected EMS sprouting (Fig 1A). EMS with smooth muscle cells and thymus MSCs had 2x the number of sprouts/branches as compared to other SCs. EMS with smooth muscle cells yielded a unique fan-like branching pattern. EMS with both ECs+SCs had the most VEGF, PDGF, FGF and phospho-p38 MAPK (Fig 1B). Initially, SCs were bordered by ECs (Fig 1C, top), but after embedding in fibrin, the SCs extravasated to a more vessel-appropriate locale exterior to the ECs. The majority of sprouts were from the SCs while ECs colocalized to a few (Fig 1C bottom).
Conclusion: Combining ECs and SCs into 3D clusters yields a robust sprouting response that relies on physical contact between both cell types. The resulting angiogenic response and branching morphology is influenced by the SC type, and SCs may also initiate angiogenic sprouts. These results reveal the significant pleiotropic effects and specific active role of SCs in in vitro angiogenesis.
- © 2012 by American Heart Association, Inc.