Abstract
Purpose: Telomere
is a nucleoprotein complex at the end of eukaryotic chromosomes and its length
is regulated by telomerase. The number of DNA repeat sequence (TTAGGG)n
is reduced with each cell division in differentiated cells. The aim of this
study was to evaluate the effect of SCF (Stem Cell Factor), Flt3 (Fms- Like
tyrosine kinase-3), Interleukin-2, 7 and 15 on telomere
length and hTERT gene expression in mononuclear and umbilical cord blood stem
cells (CD34+ cells) during development to
lymphoid cells.
Methods:
The mononuclear cells were isolated from umbilical cord blood by Ficoll-Paque
density gradient. Then cells were cultured for 21 days in the presence of different
cytokines. Telomere length and hTERT gene expression were evaluated in freshly
isolated cells, 7, 14 and 21 days of culture by real-time PCR. The same
condition had been done for CD34+ cells but telomere length and
hTERT gene expression were measured at initial and day 21 of the experiment.
Results: Highest
hTERT gene expression and maximum telomere length were measured at day14 of
MNCs in the presence of IL-7 and IL-15. Also, there was a significant
correlation between telomere length and telomerase gene expression in MNCs at
14 days in a combination of IL-7 and IL-15 (r = 0.998, p =0.04).
In contrast, IL-2 showed no distinct effect on telomere length and hTERT gene
expression in cells.
Conclusion: Taken together, IL-7 and IL-15 increased telomere length and hTERT gene expression at
14 day of the experiment. In conclusion, it seems likely that cells maintain
naïve phenotype due to prolonged exposure of IL-7 and IL-15.