[Effects of human umbilical cord blood mesenchymal stem cells on the expansion of CD34+ cells from umbilical cord blood].

OBJECTIVE

The previous studies indicated that mesenchymal stem cells (MSCs) either from umbilical cord blood (UCB) or from bone marrow (BM) had the same biological characteristics and the function of secreting hematopoietic growth factors (HGFs). The present study aimed to understand the effects of human UCB MSCs on the expansion of CD(34)(+) cells from UCB.

METHODS

1. Human UCB CD(34)(+) cells were incubated in the system containing UCB MSCs, HGFs and serum free medium. 2. The surface markers (CD(34)(+), CD(34)(+)CD(38)(-), CD(34)(+)CD(3)(+), CD(34)(+)CD(19)(+), CD(34)(+)CD(33)(+), CD(34)(+)CD(41a)(+)) on expanded UCB cells were examined by flow cytometry on the 6th and 12th days. 3. The expanded and unexpanded cells were cultured in semi-solid culturing system and checked for colony forming units of granulocyte and macrophage (CFU-GM), erythroid burst-forming unit (BFU-E), colony forming units of granulocyte- erythrocyte-megakaryocyte-macrophage (CFU-Mix) and colony forming units of high-proliferative potential (CFU-HPP).

RESULTS

1. The expansion folds of CD(34)(+)CD(38)(-) cells from UCB MSCs + HGFs groups on the 6th and 12th days were 159.43 and 436.68, respectively. Interestingly, the percentage of CD(34)(+)CD(38)(-) cells declined in HGFs group after expanding for 12 days, but it rose to 9.98% in the UCB MSCs + HGFs group. 2. Colony forming capacity of expanded UCB cells showed that the folds of CFU-Mix and CFU-HPP of UCB MSCs + HGFs group increased from day 6 to day 12, but the folds decreased in the HGFs group. 3. From day 0 to day 12, CD(34)(+)CD(33)(+) cells and CD(34)(+)CD(41a)(+) cells were amplified gradually, but CD(34)(+)CD(19)(+) and CD(34)(+)CD(3)(+) cells decreased gradually, and in UCB MSCs + HGFs group this phenomenon was more significant than that in HGFs group.

CONCLUSION

1. UCB MSCs containing system not only has the ability to expand the primitive HSCs but also has the ability to sustain the proliferation of HSCs. 2. UCB MSCs containing system amplified mainly myeloid and megakaryocytoid progenitor subsets. These may have clinical significance in reducing infection and hemorrhage.