Biomechanical stress unmasks a fibroblast-dependent hypercontractile-disarray phenotype in MYBPC3 truncation HCM
Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine
Hypertrophic cardiomyopathy (HCM) is commonly caused by pathogenic variants in the sarcomere, such as truncations in myosin-binding protein C (MYBPC3), yet clinical severity and adverse outcomes correlate poorly with genotype alone and are strongly influenced by fibrosis. We developed an engineered human micro-heart tissue (HT) combining iPSC-derived cardiomyocytes (CM) with defined primary cardiac fibroblast (cFB) fractions and mechanically modulated afterload. This design allowed us to test how stromal context and pro-fibrotic signaling shape HCM pathogenesis in micro-engineered heart tissues made from iPSCs harboring an HCM-linked frameshift variant in(MYBPC3fs). Under low afterload, genotype-associated differences in total active force were limited at 0% and 5% added cFB but became apparent at 25% added cFB. However, high afterload markedly amplified MYBPC3fsHT hypercontractility, with tissues generating greater total active force at both 5% and 25% added cFB. We also observed afterload- and cFB-dependent remodeling of Cahandling, indicating that excitation–contraction coupling in MYBPC3fs tissues is modulated by combinatorial actions of mechanical stress and the stromal environment. Despite heightened contractile output, the MYBPC3fsHT exhibited blunted improvements in Z-disc alignment with increasing cFB content, whereas cardiomyocytes within the isogenic controlHT showed progressive structural ordering as cFB density increased. Finally, the MYBPC3fsHT exhibited a great
Abstract
Hypertrophic cardiomyopathy (HCM) is commonly caused by pathogenic variants in the sarcomere, such as truncations in myosin-binding protein C (MYBPC3), yet clinical severity and adverse outcomes correlate poorly with genotype alone and are strongly influenced by fibrosis. We developed an engineered human micro-heart tissue (HT) combining iPSC-derived cardiomyocytes (CM) with defined primary cardiac fibroblast (cFB) fractions and mechanically modulated afterload. This design allowed us to test how stromal context and pro-fibrotic signaling shape HCM pathogenesis in micro-engineered heart tissues made from iPSCs harboring an HCM-linked frameshift variant in(MYBPC3fs). Under low afterload, genotype-associated differences in total active force were limited at 0% and 5% added cFB but became apparent at 25% added cFB. However, high afterload markedly amplified MYBPC3fsHT hypercontractility, with tissues generating greater total active force at both 5% and 25% added cFB. We also observed afterload- and cFB-dependent remodeling of Cahandling, indicating that excitation–contraction coupling in MYBPC3fs tissues is modulated by combinatorial actions of mechanical stress and the stromal environment. Despite heightened contractile output, the MYBPC3fsHT exhibited blunted improvements in Z-disc alignment with increasing cFB content, whereas cardiomyocytes within the isogenic controlHT showed progressive structural ordering as cFB density increased. Finally, the MYBPC3fsHT exhibited a greater response to TGF-β, leading to exaggerated increases in tissue-level resting tension and α-smooth muscle actin expression. Our findings provide important insights into the pathophysiologic pathways leading to adverse outcomes in clinical HCM and a foundation for future studies of cardiomyocyte–fibroblast interactions in HCM.