Mast Cell St8sia1 Is a Glyco-Epigenetic Checkpoint Driving Cardiac Remodeling

BACKGROUND: Pathogenic immune-cardiac crosstalk underlies maladaptive remodeling in chronic heart failure, yet therapies directly targeting this axis are lacking. Glycoconjugates, which are crucial for signal transduction and extracellular matrix integrity, represent an underexploited therapeutic avenue. This study sought to define the role of glycoconjugate-metabolizing enzymes at the immune-cardiac interface and evaluate their translational potential. METHODS: We performed integrative analyses of bulk and single-cell RNA sequencing data from failing human and mouse hearts. Employing mouse models of pressure overload (transverse aortic constriction) and ischemia-reperfusion, we used global and mast cell (MC)-specific gene deletion, bone-marrow chimeras, and pharmacological neutralization. Mechanistic insights were gained through multiomics profiling, including RNA-seq, ATAC-seq, CUT&Tag, and proteomics. RESULTS: monocyte recruitment after transverse aortic constriction and ischemia-reperfusion. Therapeutic neutralization of GD3 with the clinical-grade monoclonal antibody R24 improved cardiac function and diminished scar formation after ischemia-reperfusion. Mechanistically, GD3 bound specific histone variants, such as H2A.Z and H3.3C, thereby reprogramming chromatin accessibility to activate proinflammatory and profibrotic transcriptional programs in MCs. Consequently, GD3 inhibition suppressed MC degranulation, disrupted pathogenic MC-cardiomyocyte/fibroblast crosstalk, and preserved reparative macrophage populations. CONCLUSIONS: The MC-restricted St8sia1-GD3 axis functions as a glyco-epigenetic checkpoint driving maladaptive cardiac remodeling. Targeting this axis represents a translatable immunomodulatory strategy to prevent the progression to chronic heart failure.