SB623 cell and MSC-conditioned medium enhances HUVEC tube formation. HUVECs were cultured with OptiMEM conditioned by either MSCs or SB623 cells or unconditioned OptiMEM (“Control”). Compared to unconditioned medium, there were more complete vascular tubes formed within 16 hours in the presence of conditioned medium (CM). The average number of completely-enclosed rings formed by the HUVECs (labeled “complete tubes”) in the entire well (96-well plate; 3–4 wells/group) is plotted. Mean ± SEM.