SB623 cell- and MSC-conditioned medium supports HUVEC survival and proliferation. Following “starvation”, HUVECs were cultured for 7 days with OptiMEM conditioned by either MSCs or SB623 cells or unconditioned OptiMEM (“Control”). A) Compared to unconditioned medium, conditioned medium (CM) led to a significant decrease in dead/dying propidium iodide-positive HUVECs. B) There was a significant increase in expression of Bcl-2, indicating that factors secreted by MSCs or SB623 cells are anti-apoptotic for HUVECs. C) Compared to unconditioned medium, CM led to a significant increase in Ki67-positive proliferating HUVECs. Mean ± SD; *p < 0.05 compared to OptiMEM only Control group.