Synchrony of telomere length among hematopoietic cells

Objective: Little is known about the relationship of telomere length among leukocyte subsets and cells up the hematopoietic hierarchy. This information is relevant because telomere dynamics in granulocytes were postulated to mirror those of hematopoietic stem cells (HSCs). Materials and Methods: In newborn umbilical cord blood (UCB), we examined the relationships of telomere length in hematopoietic progenitor cells (HPCs) (CD34⁺CD45^-) with those in T lymphocytes and granulocytes. In addition, we correlated telomere length in granulocytes with those in whole leukocyte samples of individuals ranging in age from birth to 100 years. Results: In the UCB, we found strong correlations of telomere length in HPCs with telomere length in T lymphocytes (r ranging from 0.882 to 0.935; p ranging from 0.0038 to 0.0007) and in granulocytes (r = 0.930; p = 0.0072). At birth, strong correlations were also observed between telomere length in granulocytes and those in all leukocytes (r = 0.979; p = 0.0003). Throughout the human lifespan, the relationship between telomere length in granulocytes and that in all leukocytes was r > 0.980 and p < 0.0001. Conclusions: Robust synchrony exists among leukocyte subsets throughout the human lifespan; individuals with relatively long (or short) telomeres in one leukocyte subset have long (or short) telomeres in other leukocyte subsets. Moreover, telomere length in leukocytes reflects its length in cells up the hematopoietic hierarchy, i.e., HPCs and, by inference, HSCs. Strong links have been found by many studies between leukocyte telomere length and a host of aging-related diseases. Our findings suggest, therefore, that these links might be traced to telomere dynamics in HSCs.