Asxl1 clonal hematopoiesis exacerbates abdominal aortic aneurysm through the IRAK2–IRF5 macrophage inflammasome axis

Background Clonal hematopoiesis of indeterminate potential (CHIP) is an age-associated condition caused by somatic mutations in hematopoietic stem cells and is linked to adverse cardiovascular outcomes. Abdominal aortic aneurysm (AAA) is a fatal disease with no established pharmacotherapy to limit its progression, and current management relies on surgical or endovascular repair. Although previous UK Biobank analyses suggest an association between ASXL1-mutated CHIP and AAA, the underlying mechanisms remain unclear. Purpose We aimed to define how ASXL1-CHIP accelerates AAA and identify a therapeutic strategy to limit progression and rupture. Methods Lethally irradiated CD45.2+Apoe−/− mice were transplanted with bone marrow from CD45.1+Asxl1WT/WT or CD45.1+Asxl1G643Wfs*12/WT donors to generate Asxl1-WT (control) and Asxl1-CHIP mice, followed by angiotensin II infusion for 4 weeks (Fig1A). Abdominal aortic diameter was assessed by ultrasound at baseline and 4 weeks. Aortic pathology and inflammation were evaluated by EVG staining, immunofluorescence, flow cytometry, and qPCR. Bone marrow–derived macrophages (BMDMs) were cultured and stimulated with LPS and nigericin to assess NLRP3 inflammasome activation by immunoblotting and ELISA (Fig1G). Colchicine was administered in vivo and in vitro to evaluate therapeutic effects. Single-nucleus RNA sequencing (snRNA-seq) of aortic tissue was performed to identify disease-associated cellular programs (Fig2A). Results Asxl1-CHIP mice showed increased AAA formation and rupture, with greater elastin degradation, vasa vasorum expansion, and adventitial accumulation of donor-derived macrophages. CCR2high MHC-IIhigh inflammatory macrophages expanded, with increased aortic expression of inflammatory cytokine genes, including Il1b (Fig1B-F). Colchicine attenuated AAA formation and rupture, and reduced macrophage accumulation and aortic Il1b expression (Fig1B-F). Asxl1-mutant BMDMs exhibited enhanced NLRP3 inflammasome activation with increased IL-1β secretion, which was suppressed by colchicine (Fig1H,I). snRNA-seq identified expansion of an inflammasome-associated macrophage subcluster (Irak2highIrf5high) and an angiogenic endothelial subcluster consistent with vasa vasorum remodeling; both were suppressed by colchicine (Fig2B,D,E). These findings were supported by macrophage signaling analyses demonstrating enhanced IRAK2–IRF5 signaling and GO enrichment of angiogenesis-related pathways in the angiogenic endothelial subcluster (Fig2C,F). Conclusion Asxl1-CHIP exacerbates AAA through macrophage NLRP3 inflammasome hyperactivation and is associated with vasa vasorum expansion. An Irak2highIrf5high macrophage subcluster and an angiogenic endothelial subcluster represent a cellular mechanism linking hematopoietic Asxl1 mutation to vascular inflammation and remodeling. Colchicine mitigates these processes, supporting a clinically actionable therapeutic strategy for CHIP-associated AAA.