Adult stem cells provide the basis for regeneration of aging tissue. Their dual ability for self-
renewal and multilineage differentiation is controlled by direct interaction with a specific
microenvironment–the so called “stem cell niche”. Hematopoietic stem cells (HSC) reside in
the bone marrow. It is still under debate if HSC can rejuvenate infinitively or if they do not
possess “true” self-renewal and undergo replicative senescence such as any other somatic
cell. Furthermore, the question arises to what extent age-related changes in HSC are due to …