Transcriptional and functional consequences of Oncostatin M signaling on young Dnmt3a-mutant hematopoietic stem cells.

Age-associated clonal hematopoiesis (CH) occurs due to somatic mutations accrued in hematopoietic stem cells (HSCs) that confer a selective growth advantage in the context of aging. The mechanisms by which CH-mutant HSCs gain this advantage with aging are not comprehensively understood. Using unbiased transcriptomic approaches, we identified Oncostatin M (OSM) signaling as a candidate contributor to age-related Dnmt3a-mutant CH. We found that Dnmt3a-mutant HSCs from young adult mice (3-6 months old) subjected to acute OSM stimulation do not demonstrate altered proliferation, apoptosis, hematopoietic engraftment, or myeloid differentiation. Dnmt3a-mutant HSCs from young mice do transcriptionally upregulate an inflammatory cytokine network in response to acute in vitro OSM stimulation as evidenced by significant upregulation of the genes encoding IL-6, IL-1β, and TNFα. OSM-stimulated Dnmt3a-mutant HSCs also demonstrate upregulation of the anti-inflammatory genes Socs3, Atf3, and Nr4a1. In the context of an aged bone marrow (BM) microenvironment, Dnmt3a-mutant HSCs upregulate proinflammatory genes but not the anti-inflammatory genes Socs3, Atf3, and Nr4a1. The results from our studies suggest that aging may exhaust the regulatory mechanisms that HSCs employ to resolve inflammatory states in response to factors such as OSM.