Umbilical cord blood mononuclear cells co-cultured with osteoblasts contribute to in vivo neo-vascularization

Introduction Endothelial progenitors obtained from umbilical cord blood (UCB) have been suggested to improve the vascularization of bone tissue engineered constructs. Combining the UCB mononuclear cell (MNC) fraction with endothelial-supportive osteoblasts could bring strong improvements to in vivo neo-vascularization of constructs. Experimental Osteoblasts (Ob) obtained from adipose-derived stem cells were cultured on membranes of Chondrus crispus kappa/iota carrageenan until confluence. UCB-MNC were isolated by differential centrifugation, seeded on top of the Ob monolayer, co-cultured for 7 and 21 days and implanted in nude mice. Results The presence of cells positive for CD31 and vWF was confirmed along the co-culture. Gene expression analysis showed over expression of CD31 and VE-cadherin in the co-cultures at day 21. Independently of the time of implantation, H&E analysis revealed the presence of an intense inflammatory infiltrate. Human CD31 positive cells integrated the blood vessels surrounding the co-cultured implants suggesting the migration of UCB-MNC to the nascent vessels. Moreover, increased blood vessel formation was found around the co-culture implants in comparison to the controls corresponding to transplants only with Ob.Conclusion These results indicate the potential use of the UCB-MNC without further selection and supported by co-culture with osteoblasts, as a source of endothelial progenitors capable of contributing to new blood vessel formation in vivo.