Abstract / Summary
Abstract 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.