Hematopoietic stem cell aging promotes TET2 clonal hematopoiesis

Area of Science:

• Hematology
• Aging research
• Cancer biology

Background:

• Aging is linked to clonal hematopoiesis (CH) and myeloid malignancies.
• The influence of aging on CH mutation clonal selection remains unclear.

Purpose of the Study:

• To investigate the role of aging in the clonal expansion of hematopoietic stem cells (HSC) with CH mutations.
• To elucidate the mechanisms by which aging promotes CH.

Main Methods:

• Utilized a mouse model of CH involving Tet2 knockout (KO) hematopoietic stem cells (HSC).
• Compared the expansion rates of HSC from old versus young donor mice in recipients of varying ages.
• Analyzed gene expression patterns and cellular responses in aged and young HSC from both mice and humans.

Main Results:

• Transplanted Tet2 KO HSC from old donors expanded faster than young HSC, regardless of recipient age.
• This accelerated expansion was evident by middle age and attributed to reduced fitness of aged competitor non-mutant HSC.
• Aged HSC showed increased RUNX1 activity and ribosomal protein gene expression, triggering a p53-mediated stress response, which Tet2/TET2 inactivation reversed.

Conclusions:

• Aging creates an environment conducive to the clonal expansion of Tet2, Runx1, and Trp53 mutant HSC.
• This process promotes the development of clonal hematopoiesis and potentially myeloid malignancies.