The aging of lympho-hematopoietic stem cells.

The extensive self-renewal capacity of hematopoietic stem cells (HSCs) implies that this cell population may not age and thus may provide undiminished replenishment of blood cells throughout the lifespan of an organism. In contrast, accumulating experimental evidence supports the premise that HSCs show signs of aging and may have a limited functional lifespan. We summarize here the evidence for HSC aging, discuss the possible molecular mechanisms that may be involved and show evidence of a genetic connection between the effects of age on blood-forming cells and the longevity of mice. We speculate that age-related functional decline in adult tissue HSCs limits longevity in mammals.