Expansion of human umbilical cord blood CD34~+ cells using a co-cultured system with human umbilical cord blood stromal cell adherent layers

Objective:To elucidate the effects of human umbilical cord blood stromal cells(hUCBSCs) on expansion of umbilical cord blood CD34~(+) cells in vitro. Methods:Cord blood CD34~(+ )cells were separated by MACS system from 9 fresh samples. Cord blood stromal cells were cultured by using DEXTER culture system of stromal cells and their morphologic appearance and expression of surface antigen were examined. Human umbilical cord blood CD34~(+ )cells were expanded by coculture with hUCBSCs,or cytokines or both. The expanded CD34~(+ )cells were assessed for the degree of expansion and the number of colony-forming units in semisolid culture. Results:hUCBSCs were composed of several kinds of cells,and were positive for CD68,Fn and CD31,and negative for CD34. Adherent layer of hUCBSCs,alone or combined with cytokines,increased CD34~(+ )cells expansion. Ex vivo formation of CFU of expanded CD34~(+ )cells was significantly higher than that of primary CD34~(+ )cells. SCF+IL-3 +EPO+TPO+GM-CSF+hUCBSCs manifested the most potent combination. hUCBSCs had a significant superiority on the expansion of CFU-Mg. Conclusion:Human umbilical cord blood stromal cells could be used for the expansion of CD34~(+ )cells. Combining cytokines with hUCBSCs could further increase the degree of expansion. hUCBSCs could be of special value in enhancing expansion of CFU-Mg.