Aging drives Tet2+/- clonal hematopoiesis via IL-1 signaling.

Clonal hematopoiesis of indeterminate potential (CHIP), also referred to as aging-related clonal hematopoiesis (ARCH), is defined as an asymptomatic clonal expansion of mutant mature hematopoietic cells over 4% of blood leukocytes. CHIP associates with advanced age and increased risk for hematological malignancy, cardiovascular disease and all-cause mortality. Loss-of-function somatic mutations in TET2 are frequent drivers of CHIP. However, the contribution of aging-associated cooperating cell-extrinsic drivers, like inflammation, remains under-explored. Using bone marrow (BM) transplantation and newly developed genetic mosaicism (HSC-SCL-Cre-ERT; Tet2+/flox; R26+/tm6(CAG-ZsGreen1)Hze) mouse models of Tet2+/--driven CHIP, we observed an association between increased Tet2+/- clonal expansion and higher BM levels of the inflammatory cytokine IL-1 upon aging. Administration of IL-1 to mice carrying CHIP led to an IL-1R1-dependent expansion of Tet2+/- hematopoietic stem and progenitor cells (HSPCs) and mature blood cells. This expansion was caused by increased Tet2+/- HSPC cell-cycle progression, increased multilineage differentiation and higher repopulation capacity compared to their WT counterparts. In agreement, IL-1α-treated Tet2+/- HSCs showed increased DNA replication and repair transcriptomic signatures and reduced susceptibility to IL-1α-mediated downregulation of self-renewal genes. Importantly, genetic deletion of IL-1R1 in Tet2+/- HPSC or pharmacological inhibition of IL-1 signaling impaired Tet2+/- clonal expansion, establishing the IL-1 pathway as a relevant and therapeutically targetable driver of Tet2+/- CHIP progression during aging.