Submitted September 9, 2005
Accepted March 19, 2006
Human short-term repopulating cells have enhanced
telomerase reverse transcriptase expression
Marcus Jaras, Anna Edqvist, Johan Rebetz, Leif G Salford, Bengt Widegren, and Xiaolong Fan*
Section of Molecular Medicine & Gene Therapy, Lund Strategic Research Center for Stem Cell Biology
Section of Immunology, Lund University Hospital, Lund University, Sweden
The Rausing Laboratory, Division of Neurosurgery, Lund University Hospital, Lund University, Sweden
* Corresponding author; email: xiaolong.fan{at}med.lu.se.
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
upregulated human telomerase reverse transcriptase
(hTERT) expression by using a hTERT reporting adenoviral
vector encoding destabilized GFP (dGFP) driven by the
hTERT promoter and functionally characterized them in
comparison to control vector transduced CD34+ cells
expressing GFP. Following a two-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/G2/M phase compared to the GFP+ cells (56 ± 1.8% versus
35 ± 4.3%, p<0.001), and fewer cells in G0 phase (8.1 ± 3.0%
versus 20 ± 4.7%, p<0.01). However, the colony-forming and
short-term NOD/SCIDBeta2m-/- 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 to the GFP+ cells and lacked secondary
NOD/SCIDBeta2m-/- mice bone marrow repopulating
capacity. Thus, upregulation of hTERT expression within
the CB HSC pool is accompanied by decreased self-renewal
capacity.
