Alternative splicing remodeling and splicing factor regulatory networks define immune-associated molecular heterogeneity in dilated cardiomyopathy.

Dilated cardiomyopathy (DCM), a progressive cardiac disorder marked by ventricular dilatation and systolic dysfunction, involves a complex interplay between genetic and immune dysregulation. However, how alternative splicing remodeling contributes to its molecular heterogeneity remains poorly understood. Here, we performed an integrated transcriptomic analysis to characterize DCM-associated alternative splicing landscapes and their regulation by splicing factor networks. We identified widespread differential alternative splicing (DAS) events in DCM, with affected genes significantly enriched in cardiac contraction, sarcomere organization, calcium handling, extracellular matrix remodeling, and protein metabolism. Representative splicing events in key cardiac genes, including TTN, RYR2, LDB3, and FLNA, exhibited distinct junction usage and percent spliced in (PSI) alterations between DCM and control samples, suggesting functionally relevant transcript isoform remodeling. By integrating splicing factor expression profiles with DAS event PSI values, we constructed a characteristic SF-AS regulatory network and identified five key splicing factors-MBNL1, NOVA1, RBM25, RBM5, and SF1-as candidate tissue-level biomarkers of DCM-associated splicing remodeling. Molecular subtype analysis further revealed distinct DCM subgroups characterized by divergent immune infiltration patterns, pathway activities, and hub gene signatures. Machine learning-based identification and external validation supported the diagnostic potential of this five-splicing-factor signature. Collectively, this study deciphers coordinated splicing factor-associated alternative splicing remodeling in DCM, providing deeper insights into the immune-associated molecular heterogeneity and potential regulatory mechanisms underlying disease progression.