Hematopoietic stem cells (HSCs)

Hematopoietic stem cells (HSCs) are the rare master cells in your bone marrow that make blood for your whole life. They do it by dividing in a way that both renews themselves and produces every type of blood cell, across the lymphoid and myeloid families. With age, the HSC pool gets bigger in number but worse in quality. Older HSCs lean toward making myeloid cells at the expense of immune lymphocytes, engraft less well, carry more DNA damage, drift epigenetically, and have weaker mitochondria. One age-related change stands out: clonal hematopoiesis, where HSC clones carrying mutations in genes like DNMT3A, TET2, and ASXL1 expand. It shows up in about 10% of people over 70 with standard testing (and a lot more with deep sequencing), and it raises the risk of blood cancers, heart disease, and earlier death. That makes HSC aging a direct contributor to whole-body decline.

Last reviewed: June 22, 2026

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