Epigenetics of hematopoietic stem cell aging and disease.

The decline in the regenerative potential of tissues is one of the most evident characteristics of aging. Stem cell aging determines the aging phenotypes of tissues, and has thus been recognized as one of the hallmarks of mammalian aging. An emerging body of evidence supports an essential role for epigenetic controls in regulating cellular functions. Many epigenetic modifications become stabilized at a particular stage of development. However, epigenetic marks can also readily change over time. This "epigenetic drift" contributes to changes in cellular phenotypes and when it takes place in adult stem cells, may play an important role in stem cell aging. Epigenetic alterations are now recognized as another hallmark of mammalian aging. This process depends on cell intrinsic and extrinsic factors, although the underlying molecular mechanisms remain largely unknown. Here, we review the current progress in the study of epigenetic changes regulating aging hematopoietic stem cells (HSCs). We particularly focus on the epigenome and its regulators in aging HSCs.