ABSTRACT
Objective: To investigate the mechanisms on the regulation of telomere and telomerase in the process of senescence induction of human-derived CD34+CD38- leukemia stem cells (LSC) subpopulation by Angelica sinensis polysaccharide (ASP). Methods: The human-derived CD34+CD38- LSC subpopulation was isolated from acute myelogenous leukemia bone marrow mononuclear cells by magnetic activated cell sorting. The inhibition of ASP on CD34+CD38- LSC subpopulation proliferation was detected by CCK-8 assay. The percentage of senescent cells was detected by SA-β-Gal staining. The colony-formed ability was detected by Colony-forming Assay. The levels of telomerase activities and telomerase reverse transcriptase (TERT) gene expression were performed by TRAP-PCR and quantitative RT-PCR, respectively. The changes of telomere length were tested by Southern blotting assay. Results: The CD34+CD38- LSC subpopulation could be effectively isolated by MACS. The purity of CD34+CD38- LSC population is up to (91.15 ± 2.41)%; The cells showed the features of well-stacked morphology, high transparency, well refraction under inverted phase contrast microscope. ASP had a remarkable dose-dependent inhibition on CD34+CD38- LSC proliferation in vitro culture (P < 0.05). The number of SA-β-Gal staining positive cells had been increased compared to the cells in control group (P < 0.01), a decrease in colony-forming abilities (P < 0.01), a decrease level on TERT gene and telomerase activities (P < 0.05), and a shorter length on telomere of CD34+CD38- LSC after 40 μg/mL ASP co-culture for 48 h (P < 0.05). Conclusion: ASP could induce the senescence of human derived leukemia bone marrow CD34+CD38- LSC via regulating the cell telomere system in vitro co-culture.
ABSTRACT
PURPOSE: The umbilical cord blood has been considered as an alternative source of hematopoietic stem cells for transplantation. The CD34+ is known as a common stem cell antigen and the CD34+ CD38- immunophenotype reportedly defines a primitive subpopulation of progenitor cells. In this study the frequency of CD34+ and CD34+ CD38- hematopoietic stem/progenitor cells in placental/cord blood (UCB), and adult peripheral blood (PB) were determined. METHODS: Between July and September 1998, 27 collections of UCB were performed at the obstetric units of Hanyang University Hospital. Fifteen adult PB samples were also obtained for control. RESULTS: The frequency of total CD34+ cells in UCB was higher (1.13+/-0.58% vs 0.46+/-0.30%, P=0.0002) than PB and the frequency of CD34+ CD38- cells in UCB was also greater (0.02+/-0.02 vs 0.01+/-0.01, P=0.035) than PB. The majority of UCB- and PB-derived CD34+ cells expressed CD38- antigen (98.22+/-2.11% in UCB and 97.85+/-2.56% in PB). The frequency of CD38- expression by UCB derived CD34+ cells was slightly higher (not statistically significant) than that by PB derived CD34+ cells. The frequency of CD34+ cells was increased linearly with birth weight (r=0.413). CONCLUSION: These results suggest that UCB could be a useful source of highly primitive hematopoietic stem cells for marrow reconstitution after bone marrow ablation.