title: Human short-term repopulating cells have enhanced telomerase reverse transcriptase expression.
abstract: Telomerase activity has been suggested to be critically involved in hematopoietic stem cell (HSC) self-renewal. However, it has been unclear whether human HSCs have telomerase activity and how telomerase activity is regulated within the HSC and progenitor pool. Here, we isolated living cord-blood (CB) CD34(+) cells with up-regulated human telomerase reverse transcriptase (hTERT) expression by using an hTERT-reporting adenoviral vector encoding destabilized green fluorescent protein (dGFP) driven by the hTERT promoter, and functionally characterized them in comparison with control vector-transduced CD34(+) cells expressing GFP. Following a 2-day serum-free transduction protocol, cells were sorted into a dGFP(+) and a GFP(+) fraction. Cell-cycle analysis revealed that the dGFP(+) cells had a greater proportion of cells in S/G(2)/M phase compared with the GFP(+) cells, (56% +/- 1.8% vs 35% +/- 4.3%; P < .001) and fewer cells in G(0) phase (8.1% +/- 3.0% vs 20% +/- 4.7%; P < .01) However, the colony-forming and short-term nonobese diabetic/severe combined immunodeficient (NOD/SCID) B2m(-/-) mice bone marrow-repopulating capacities were similar between the dGFP(+) and the GFP(+) cells. Interestingly, the dGFP(+) cells had a 6-fold lower repopulating capacity in NOD/SCID mice compared with the GFP(+) cells and lacked secondary NOD/SCID B2m(-/-) mice bone marrow-repopulating capacity. Thus, up-regulation of hTERT expression within the CB HSC pool is accompanied by decreased self-renewal capacity.
authors.affiliation: Section of Molecular Medicine and Gene Therapy, Lund University, BMC-A12, 221 84 Lund, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Järås
authors.forename: Anna
authors.initials: A
authors.lastname: Edqvist
authors.forename: Johan
authors.initials: J
authors.lastname: Rebetz
authors.forename: Leif G
authors.initials: LG
authors.lastname: Salford
authors.forename: Bengt
authors.initials: B
authors.lastname: Widegren
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Fan
mesh_terms: D000818:Animals; D018952:Antigens, CD34; D002453:Cell Cycle; D004268:DNA-Binding Proteins / Q000235:genetics*; D005312:Fetal Blood / Q000166:cytology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000201:enzymology; D006801:Humans; D007399:Interphase; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D019098:Telomerase / Q000235:genetics*; D014161:Transduction, Genetic; D015854:Up-Regulation / Q000235:genetics*
chemical_list: D018952:Antigens, CD34; D004268:DNA-Binding Proteins; D049452:Green Fluorescent Proteins; D019098:Telomerase