Effects of aging on hematopoietic stem and progenitor cells.

Although relationships between cellular and organismal aging are not well understood, several studies describe age-related changes in hematopoietic stem cells (HSCs) with functional consequences for the hematopoietic system. Importantly, aged hematopoietic stem and progenitor cells (HSPCs) differ from their younger counterparts in functional capacity, the complement of proteins on the cell surface, transcriptional activity, and genome integrity. These changes, however, are likely the result of a combination of cell-intrinsic and microenvironment-derived influences. Evolving views of the composition of the HSC compartment suggest that changes in HSCs may reflect the effects of the aging process on individual HSCs or a shift in the clonal composition of the HSC pool with age.