Spatiotemporal transcriptomics elucidates the pathogenesis of fulminant viral myocarditis

Abstract Fulminant myocarditis (FM) is a severe inflammatory condition of the myocardium that often results in cardiogenic shock and sudden death, particularly in young individuals. Previously, we demonstrate that infiltration and selfrecruitions of early neutrophils and subsequent monocytes/macrophages and by which cytokine storm form and myocardial injury constitute core pathophysiology of FM. However, it is still not clear on interaction of different types of cells or sub-cell clusters. In this study, we employed single-nucleus and spatial transcriptomics to perform a comprehensive analysis of coxsackievirus B3 (CVB3) -induced FM in A/J mice, spanning seven distinct time points pre- and post-treatment. Our findings reveal that mesothelial cells play a critical role in the early stage of myocarditis by acting as primary targets for CVB3 infection. This triggers the activation of macrophages, initiating a cascade of inflammation. Subsequently, pro-inflammatory InflammatoryMac and T cells infiltrate the myocardium, driving tissue damage. We also identified Cd8+ effector T cells as key mediators of cardiomyocyte injury. These cells release cytotoxic molecules, particularly IFN-γ, which modulates the expression of Spi1, a factor implicated in exacerbating cardiomyocyte death and amplifying disease progression. Therapeutic interventions targeting the IFN-γ/Spi1 axis demonstrated significant efficacy in FM models. Notably, intravenous immunoglobulin (IVIG) treatment reduced mortality, suppressed viral proliferation, and mitigated the hyperinflammatory state of FM. IVIG therapy also downregulated IFN-γ and Spi1 expression, underscoring its immunomodulatory and therapeutic potential. This comprehensive spatiotemporal transcriptomic analysis provides profound insights into the pathogenesis of FM and highlights actionable therapeutic targets, paving the way for more effective management strategies for this life-threatening condition.