Ex vivo expansion of CD34+ cells from human umbilical cord blood by FL gene transfected bone marrow stromal cells

The object of this study was to explore the effect of FL gene transfected marrow stromal cells on expansion of human cord blood CD34(+) cells ex vivo. A co-culture system was established with FL gene transfected human marrow stromal cells and cord blood CD34(+) cells. The CD34(+) cells were cultured in different culture systems with different combinations of stromal cells and SCF, IL-3 and FL. The numbers of total nucleated cells, CFCs and CD34(+) cells were repeatedly counted in culture systems for 3 weeks. The results showed that the FL transgenic marrow stromal cell feeder layer significantly enhanced the expansion of total nucleated cells, CFC and CD34(+) cells, compared with stromal cell feeder layer and stromal cell-free culture systems. The transgenic stromal cells and cytokines co-culture system manifested the most potent expansion of the cord blood cells with increase of the number of total nucleated cells by (122.5 +/- 4.3)-fold, CFCs by (39.6 +/- 2.7)-fold and CD34(+) cells by (11.8 +/- 0.52)-fold. It is concluded that human umbilical cord blood CD34(+) cells can be extensively expanded ex vivo by using FL gene transfected stromal cells combined with cytokines.