Effects of telomerase activity and apoptosis on ex vivo expansion of cord blood CD34+ cells


Correspondence: Haibo Cai, Ph.D., The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China. Tel.: +86 21 64251962; Fax: +86 21 64252099; E-mail: caihaibo@ecust.edu.cn



Ex vivo expansion of CD34+ cells has become critically important in order to obtain sufficient haematopoietic stem cells for clinical application. Among major regulators involved in ex vivo expansion, telomerase activity and apoptosis have been revealed to be closely linked to cell cycle progression. However, all exact roles remain to be elucidated. Here, change in telomerase activity and level of apoptosis in cord blood (CB) CD34+ cells were evaluated together with specific cell population growth rate during ex vivo culture.

Materials and methods

CD34+ cells isolated from human CB were expanded ex vivo over a 28-day period. Besides monitoring cell proliferation kinetics of the CD34+ cells, changes in telomerase activity and apoptotic levels were investigated. Several relevant genes were quantified by qRT-PCR during the culture period.


Significant elevation of telomerase activity had close relationship to activation of CB CD34+ cell expansion. Peak apoptotic level was accompanied by a remarkable decline in cell-specific growth rate, and apoptotic level of differentiated CD34 population was significantly higher than that of the CD34+ population.


Although telomerase activity was activated during the culture, expansion of CB CD34+ cells seemed to be more susceptible to apoptotic suppression when cultured ex vivo, which implied that apoptosis may serve as a rate-limiting factor involved in controlling expansion efficiency.