Abstract P3075: Hippo Pathway In Cardiac Fibroblast Regulates Macrophage Recruitment Following Injury

Abstract

Background: The evolutionary conserved Hippo signaling pathway (HSP) is an inhibitor of tissue regeneration, including the Lats1/2 kinases that phosphorylate and inactivate YAP and TAZ. Emerging data indicate that HSP regulates innate immunity, inflammation, and autoimmune diseases. However, the role of HSP in post-MI inflammation is poorly understood. Methods: Single-cell RNA-sequencing (scRNA-Seq) and spatial transcriptomics were utilized in cardiac fibroblast (CF)-specific-Lats1/2 knockout (Lats CKO) mouse heart. Flow cytometry, immunofluorescence (IF), and echocardiogram (Echo) were used to describe the phenotype in ventricle of Lats CKO mouse heart with/out Ccr2 knockout. Results: We integrated our scRNA-Seq data in Lats CKO mouse heart with three published data sets of MI mouse heart. A CF subcluster with elevated YAP activity and expressing chemokines Ccl2 and Ccl7 (Ccl2/Ccl7+ CFs) and macrophages (Macs) expressing Ccr2, the receptor for Ccl2/Ccl7 (Ccr2+ Macs), were identified, which suggests a signaling transduction from Ccl2/Ccl7+ CFs to Ccr2+ Macs in post-MI hearts. To figure out the function and mechanism of this specific cell communication, we employed a Lats CKO mice model which mimics the post-MI heart and exhibits high YAP activity and conformed the cell communication between Ccl2/Ccl7+ CFs and Ccr2+ Macs by spatial transcriptomics. Furthermore, Ccr2 loss of function in Lats CKO mice suppressed Mac expansion and CF proliferation. Consistently, Ccr2 knockout reversed the phenotype presenting smaller left ventricle chamber in Lats CKO mouse heart because of CF proliferation. Conclusion: YAP target genes Ccl2 and Ccl7 in CFs are responsible for Ccr2+ Macs recruitment and the recruited Ccr2+ Macs in turn promote CF proliferation post-MI.