Expression of telomerase during induction of committed differentiation of human cord blood hematopoietic stem/progenitor cells in vitro / 中国实验血液学杂志

ABSTRACT

To investigate the expression of telomerase in cord blood hematopoietic stem/progenitor cells during their committed differentiation in vitro and provide an index of monitoring the proliferating potential of the hematopoietic stem/progenitor cells and security for clinical application. Human CD34 positive cells were isolated from umbilical cord blood by using magnetic cell sorting system (MACS), and were induced to differentiation with hematopoietic growth factors (SCF + IL3 + IL6 + GCSF and SCF + IL3 + IL6 + EPO) in a liquid culture system. The telomerase activity and the cytalytic subunit of telomerase (hTERT) of the cells were analysed during different periods of culture by using TRAP-PCR, TRAP-ELISA, Western blot and RT-PCR techniques, respectively. The results showed that a peak of cell growth was achieved on day 14 - 21 during induction of differentiation in vitro. Total cell number could increase 1006.4 +/- 103.2 times and could not increase there after. Telomerase activity and hTERT expression were low in freshly isolated cord blood CD34(+) cells and increased after about 7 days of culture in addition of cytokine combinations of SCF + IL3 + IL6 + GCSF and SCF + IL3 + IL6 + EPO, respectively. The telomerase activity and hTERT decreased after 14 days of culture and were not detected after 28 days of culture. It was concluded that the hematopoietic stem/progenitor cells can be expanded in large number in vitro and do not have the character of immortality and the telomerase activity could be a useful index in hematopoiesis regulation.