Fibroblast-restricted inflammasome activation promotes atrial fibrillation and heart failure with diastolic dysfunction

Background: Atrial fibrillation (AF) is commonly associated with diastolic dysfunction. Both conditions involve overactivation of inflammatory signaling and cardiac fibroblasts (FBs). While the activation of the NLRP3-inflammasome in cardiomyocytes is known to cause atrial electrical remodeling and arrhythmogenicity, the role of FB NLRP3-inflammasome in heart disease is unknown. Objectives: We aimed to elucidate the contribution of FB-specific NLRP3-inflammasome activation to cardiac function and arrhythmogenesis. Methods: Human atrial FBs were isolated from atrial biopsies of AF and sinus rhythm patients. We established an FB-specific knockin (FB-KI) mouse model with FB-restricted expression of constitutively active NLRP3. Cardiac function and AF susceptibility were assessed through echocardiography, tissue Doppler, programmed electrical stimulation, and optical mapping. Results: NLRP3 and IL1B were upregulated in atrial FBs of patients with persistent AF. FB-KI mice exhibited enlarged left atria, enhanced AF-susceptibility, and heart failure with diastolic dysfunction. FBs from FB-KI mice were more transdifferentiated, migratory, and proliferative than those from control. FB-KI mice showed increased fibrous content in both atria and ventricles, atrial gap junction remodeling, and reduced atrial conduction velocity. Single-nuclei RNA-seq analysis revealed prominent transcript remodeling of metabolic pathways across multiple cell types, enhanced extracellular matrix signaling, and altered intercellular communications. Knockdown of Nlrp3 in FBs via adeno-associated virus type-dj/8 mediated transfer of shRNA reduced AF-susceptibility and prevented cardiomyopathy in FB-KI mice. Conclusions: FB-restricted activation of the NLRP3-inflammasome promotes cardiac fibrosis and AF-susceptibility. This study identifies the FB NLRP3-inflammasome activation as a key mechanism governing the concomitant AF and heart failure with diastolic dysfunction. Single replicates from either control or CF-KI (constitutive activation of NLRP3 in fibroblasts ) heart nuclei were used for single-nuclei RNA-Seq. Note: The Nlrp3 allele was silenced in non-Cre-expressing cells in this model.