Integrative transcriptomic analysis reveals interferon-associated macrophage states and fibroblast activation in hypertrophic cardiomyopathy

Myocardial immune heterogeneity may contribute to remodeling in hypertrophic cardiomyopathy (HCM), but the macrophage states accompanying fibroblast activation remain incompletely defined. We examined cell-specific immune programs and stromal changes in HCM. An integrative transcriptomic analysis included 592,689 cardiac nuclei from 15 HCM, 11 dilated cardiomyopathy (DCM), and 16 non-failing (NF) heart samples. Sample-level pseudobulk and cell-composition analyses were complemented by 31,850 spatial transcriptomic spots from eight sections of six HCM patients and two bulk cohorts. Human cardiac fibroblast responses to conditioned medium from interferon-gamma-activated THP-1-derived macrophage-like cells were assessed by quantitative polymerase chain reaction, enzyme-linked immunosorbent assays, and Cell Counting Kit-8 (CCK-8). HCM macrophages showed enriched interferon-alpha and interferon-gamma response programs without a significant increase in total macrophage fraction. Activated fibroblasts accounted for mean proportions of 6.2%, 26.6%, and 25.5% of fibroblasts in NF, HCM, and DCM samples, respectively. Several pooled immune-stromal correlations weakened within HCM. Spatial profiles showed regional organization of myocardial stress and extracellular-matrix programs, while bulk signatures varied between cohorts. In vitro, activated-macrophage conditioned medium increased fibroblast CXCL10, IL6, ACTA2, COL1A1, and FN1 expression and IL-6 and collagen I secretion, without a significant change in CCK-8 signal in the specified comparisons. Cell-state profiling distinguishes interferon-associated macrophage changes from increased macrophage abundance in HCM and identifies fibroblast activation also present in DCM. These findings characterize myocardial immune-stromal heterogeneity and provide a cellular basis for investigating tissue immune signatures in HCM.