Peripheral blood cell telomere length measurements indicate that hematopoietic stem cell turnover is not significantly increased in whole blood and apheresis PLT donors

BACKGROUND: The telomere length (TEL) of peripheral blood leukocytes (PBLs) can be used to estimate hematopoietic stem cell turnover. The current study investigated whether the repetitive stimulation of the hematopoietic system caused by regular whole blood (WB) and PLT donations would affect PBL TEL. STUDY DESIGN AND METHODS: PBLs were obtained from healthy donors (n=94) with a history of at least 3 years of WB donation (median, 7.7 years; range, 3.0-43.0 years) plus additional apheresis PLT donations. The median (range) numbers of WB and PLT donations were 22.0 (6.0-194.0) and 42.0 (7.0-336.0), respectively. Additionally, samples were obtained from healthy nondonors (n=47). PBL TEL was measured with fluorescence in situ hybridization and flow cytometry (flow-FISH). Flow-FISH results were expressed in molecular equivalents of soluble fluorochrome units (MESF; 1000 MESF=1 kMESF) either as absolute (TEL) or as age-adjusted TEL (DeltaTEL). RESULTS: Donor granulocyte and lymphocyte TELs were 12.6 +/- 0.3 (mean +/- SEM) and 13.2 +/- 0.3 kMESF, respectively. No differences were observed when compared with corresponding nondonor data (granulocytes, 12.5 +/- 0.4 kMESF; lymphocytes, 13.6 +/- 0.5 kMESF). Furthermore, DeltaTEL values did not differ between the two groups and were not different from previously established reference values. In addition, neither donor data for age-adjusted TEL for granulocytes nor DeltaTEL for lymphocytes were correlated with either total years or total numbers of WB and/or PLT donations. CONCLUSION: Long-term WB and PLT donation does not affect PBW TEL as measured by flow-FISH, arguing against a significantly increased stem cell turnover.