Abstract 143: Il-1β Antagonism Promotes SMC Differentiation And Accumulation In Fibrous Caps In Jak2 V617f Clonal Hematopoiesis

Abstract

Patients with JAK2 V617F (JAK2 VF ) clonal hematopoiesis (CH) have increased JAK/STATsignaling that imparts an increased risk of premature coronary heart disease. We have shown that mice with Jak2 VF mutations modeling CH have increased AIM2 inflammasome activation that promotes atherosclerosis. Genetic inhibition of the inflammasome through deletion of Caspase1/11 or Gasdermin D in hematopoietic stem and progenitor cells (HSPC) harboring Jak2 VF mutations increased fibrous caps thickness. Therefore, we hypothesized that inhibition of IL-1β derived from Jak2 VF macrophages promotes smooth muscle cell (SMC) reprograming and accumulation in fibrous caps. To test this hypothesis, we transplanted bone marrow (BM) with Jak2 VF expression in all HSPCs into Ldlr -/- mice and then administered the IL-1 receptor antagonist Anakinra. After 12 weeks of Western type diet (WTD) feeding, mice treated with Anakinra had thicker fibrous caps and increased ACTA2 + SMCs within the cap region. In atheromas scRNA-Seq has identified SMC-derived populations including modified SMCs and fibroblasts which are enriched for Prg4 . Consistently, Anakinra treatment increased Prg4 -expressing cells within plaques as shown by RNA scope in situ hybridization. We then modeled Jak2 VF CH by transplanting mixtures of 20% Jak2 VF BM (or 20% littermate control BM) with 80% WT BM into Ldlr -/- mice followed by administration of antibodies to IL-1β. After WTD feeding, IL-1β antibody treatment led to increased cap thickness specifically in mice modeling Jak2 VF CH. To identify how IL-1β may alter cap thickness we isolated CD11b Negative cells from aortas and conducted bulk-cell RNA-Seq. Gene ontology analysis revealed that IL-1β antagonism specifically in Jak2 VF CH mice led to the significant enrichment of 6 biological processes all of which were related to biosynthetic processes including translation, peptide biosynthetic processes, peptide metabolism and amide biosynthesis. These changes were not seen in control mice indicating that inhibition of IL-1β derived from Jak2 VF hematopoietic cells leads to increased translation and biosynthetic processes in non-myeloid cells potentially supporting SMC differentiation and migration and resulting in increased fibrous cap formation.