Inflammatory crosstalk impairs phagocytic receptors and aggravates atherosclerosis in clonal hematopoiesis in mice

Clonal hematopoiesis (CH) increases inflammasome-linked atherosclerosis but the mechanisms by which CH mutant cells transmit inflammatory signals to non-mutant cells are largely unknown. To address this question we transplanted 1.5% Jak2VF bone marrow (BM) cells with 98.5% WT BM cells into hyperlipidemic Ldlr-/- mice. Low allele burden (LAB) mice showed accelerated atherosclerosis with increased features of plaque instability, decreased levels of macrophage phagocytic receptors MERTK and TREM2, and increased neutrophil extracellular traps (NETs). These changes were reversed when Jak2VF BM was transplanted with Il1r1-/- BM. LAB mice with non-cleavable MERTK in WT BM showed improvements in necrotic core and fibrous cap formation and reduced NETs. An agonistic TREM2 antibody (4D9) markedly increased fibrous caps in both control and LAB mice eliminating the difference between groups. Mechanistically, 4D9 increased TREM2+PDGFB+ macrophages and PDGF receptor-α positive fibroblast-like cells in the cap region. TREM2 and PDGFB mRNA levels were positively correlated in human carotid plaques and co-expressed in macrophages. In summary, low frequency Jak2VF mutations promote atherosclerosis via IL-1 signaling from Jak2VF to WT macrophages and neutrophils promoting cleavage of phagocytic receptors and features of plaque instability. Therapeutic approaches that stabilize MERTK or TREM2 could promote plaque stabilization especially in CH- and inflammasome-driven atherosclerosis.