Insulin-like growth factor-I (IGF-I) has been shown to enhance the PHA-induced increase in telomerase activity for cord blood (CB) mononuclear cells. It is hypothesized that the IGF-I on telomerase activity may have an impact on the telomere length and replicative potential of cells. In this study, we have cultured isolate CB T cells (CD3+ purity = 98%) in a similar serum free liquid medium containing: (a) NoGF; (b) IGF-I, (c) PHA, and (d) IGF-I + PHA. The telomere length of cells harvested on Day 0, 3, 5, 8, 14 and 21 was measured by a quantitative flow cytometry based fluorescence in situ hybridisation technique (Q-Flow FISH). The corresponding telomerase activity was determined by the non-radioactive PCR-based Telomeric Repeat Amplification Protocol (TRAP). The telomere length of PHA stimulated T cells increased to a peak level on Day 8 and decreased back to the initial level by Day 21. The addition of IGF-1 increased the telomere length of PHA stimulated T cells throughout the course of the culture. Interestingly, this later increase in telomere length was not accompanied by a high level of telomerase in the cells at later time points in the culture. The heterogeneous relationship between telomerase and telomere length suggested that the effect of IGF-I on telomere length elongation may be due to the involvement of alternative pathways other than the initial enhancement in telomerase activity in the cells. Further experiments are needed to clarify the mechanisms involved and the impact on replicative potential of cells. This data may be useful for the ex vivo expansion of T cells for adoptive immunotherapy and transplantation.
