Concise review: hematopoietic stem cell aging and the prospects for rejuvenation.

Because of the continuous increases in lifetime expectancy, the incidence of age-related diseases will, unless counteracted, represent an increasing problem at both the individual and socioeconomic levels. Studies on the processes of blood cell formation have revealed several shortcomings as a consequence of chronological age. They include a reduced ability to mount adaptive immune responses and a blood cell composition skewed toward myeloid cells, with the latter coinciding with a dramatically increased incidence of myelogenous diseases, including cancer. Conversely, the dominant forms of acute leukemia affecting children associate with the lymphoid lineages. A growing body of evidence has suggested that aging of various organs and cellular systems, including the hematopoietic system, associates with a functional demise of tissue-resident stem cell populations. Mechanistically, DNA damage and/or altered transcriptional landscapes appear to be major drivers of the hematopoietic stem cell aging state, with recent data proposing that stem cell aging phenotypes are characterized by at least some degree of reversibility. These findings suggest the possibility of rejuvenating, or at least dampening, stem cell aging phenotypes in the elderly for therapeutic benefit.