Hematopoietic Stem Cells and Aging

Age-related changes have been noted in the hematopoietic stem cell (HSC) compartment as well as in the individual stem cell and its descendants. This distinction is crucial for a comprehensive understanding of the dynamics and the developmental potential of the stem cell pool in the aged. In addition, the issue of stem cell aging, particularly replicative senescence, deserves special attention in relation to transplantation and the in vitro approaches for expansion of the cells for clinical purposes, including gene therapy. Expansion of long-term functioning stem cells is therefore one arm of stem cell aging biology, in addition to the status of hematopoiesis in the aged. Finally, the findings on the plasticity of adult stem cells are of interest in view of the potential applications of autologous HSCs in the aged, promoting tissue repair in situ and transplanting in vitro-generated tissues. The establishment of tools to identify and isolate stem cells by distinct membrane markers has enabled critical experimental approaches and led to major progress in this area. Furthermore, procedures that enable the mobilization of the cells from the bone marrow to the peripheral blood have made the isolated stem cells accessible for research and clinical applications.