Cardiac fibroblast-derived CCN1 aggravates diabetic cardiomyopathy through ITGAV-ITGB1/integrin αvβ1-mediated autophagy inhibition

Cardiac fibrosis is a defining pathological feature of diabetic cardiomyopathy (DCM), and excessive activation of cardiac fibroblasts plays a critical role in regulating cardiomyocyte function through paracrine signaling. CCN1 (cellular communication network factor 1), an extracellular matrix protein involved in intercellular communication, has been suggested to influence cardiac remodeling, although its specific impact on cardiomyocytes in DCM has remained unclear. In this study, we found that CCN1 expression was markedly elevated in cardiac tissues from DCM mouse models and in insulin-resistant cell models, with fibroblasts serving as the primary source. Proteomic analysis and co-culture experiments demonstrated that CCN1 suppressed cardiomyocyte macroautophagy/autophagy. To determine its role in vivo, we generated fibroblast-specific ccn1 knockout mice and established a DCM model, demonstrating that ccn1 deletion ameliorated cardiac dysfunction and restored autophagic activity. We further identified ITGAV-ITGB1/integrin αvβ1 as the receptor mediating CCN1 signaling in cardiomyocytes. Molecular dynamics simulations and co-immunoprecipitation experiments confirmed that CCN1 engaged ITGAV-ITGB1/integrin αvβ1 through its cysteine-knot-containing (CT) domain. Mechanistically, this interaction activated the downstream PTK2/FAK-MTOR signaling pathway, leading to inhibition of cardiomyocyte autophagy. Together, these findings reveal a previously unrecognized fibroblast-cardiomyocyte signaling axis in which fibroblast-derived CCN1 drives DCM progression by suppressing autophagy through ITGAV-ITGB1/integrin αvβ1-dependent signaling. This work provides mechanistic insight into the pathogenesis of DCM and identifies CCN1 as a potential therapeutic target for mitigating disease onset and progression.Abbreviations: AAV9: adeno-associated virus serotype 9; ADGRE1/EMR1/F4/80: adhesion G protein-coupled receptor E1; BafA1: bafilomycin A1; BSA: bovine serum albumin; C8: compound 8; CCN1: cellular communication network factor 1; CF: cardiac fibroblast; CSA: cross-sectional area; DCM: diabetic cardiomyopathy; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; ELISA: enzyme-linked immunosorbent assay; HE: hematoxylin and eosin; HFD: high-fat diet; HG: high glucose; IR: insulin resistance; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MD: molecular dynamics; MTOR: mechanistic target of rapamycin kinase; NRCM: neonatal rat cardiomyocyte; PDGFRA: platelet derived growth factor receptor alpha; PECAM1/CD31: platelet and endothelial cell adhesion molecule 1; PTK2/FAK: protein tyrosine kinase 2; PTPRC/CD45: protein tyrosine phosphatase receptor type C; RPS6KB1: ribosomal protein S6 kinase B1; S100A4/FSP1: S100 calcium binding protein A4; SQSTM1/p62: sequestosome 1; STZ: streptozotocin; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling; WGA: wheat germ agglutinin