Biomechanical stress unmasks a fibroblast-dependent hypercontractile-disarray phenotype in MYBPC3 truncation HCM
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Why the study?
Clinical severity and adverse outcomes in HCM correlate poorly with sarcomeric genotype alone and are strongly influenced by fibrosis.
Key Points
- To determine how primary cardiac fibroblast density and mechanical afterload interact to modulate contractile mechanics, structural remodeling, and calcium handling in engineered human micro-heart tissues harboring an HCM-linked MYBPC3 frameshift variant.
- Engineered human micro-heart tissues by combining purified iPSC-derived cardiomyocytes harboring a patient-specific MYBPC3 frameshift variant (G1206fs) or isogenic controls with 0%, 5%, or 25% added primary cardiac fibroblasts.
- Cultured tissues on microfabricated PDMS posts with bending stiffness tuned to soft (0.42 N/m) or stiff (1.96 N/m) states across ≥3 independent batches to evaluate mechanical afterload sensitivity and responses to TGF-β.
- Under stiff-post loading, MYBPC3fs tissues generated significantly greater peak active force than controls at 5% cFB (∼1.6-fold) and 25% cFB (∼2.5-fold), whereas differences at 0% cFB were not statistically significant.
- Under soft-post loading, genotype-driven differences in active force were modest at 0% and 5% cFB but became pronounced at 25% cFB, where mutant tissues generated ∼2-fold higher peak active force than controls.
- Mutant tissues demonstrated blunted Z-disc alignment in response to increasing fibroblast content compared to progressive structural ordering in controls, alongside exaggerated increases in resting tension and α-smooth muscle actin expression after TGF-β exposure.
Structured PICO
P
Population
Preclinical study using engineered human micro-heart tissues combining iPSC-derived cardiomyocytes with a MYBPC3 frameshift variant and primary cardiac fibroblasts.
E
Exposure
MYBPC3 frameshift variant (G1206fs) combined with varying mechanical afterload (soft vs stiff posts) and cardiac fibroblast fractions (0%, 5%, 25%), with or without TGF-β exposure (10 ng/ml for 8 days).
C
Comparator
Isogenic control iPSC-derived cardiomyocytes under the same mechanical and stromal conditions.
O
Outcome
Contractile mechanics (peak active force, twitch kinetics) and calcium handling dynamics.surrogate
This engineered tissue model demonstrates that mechanical stress and fibrotic signaling synergistically unmask hypercontractility and structural disarray in MYBPC3-mutant hypertrophic cardiomyopathy.
Limitations
- Only three unequally spaced added-cFB fractions were examined, unable to distinguish continuous graded response from nonlinear threshold
- Side-view thickness measurements were available only for stiff-post tissues
- Only three unequally spaced added-cFB fractions were examined, limiting the ability to distinguish a continuously graded response from a nonlinear or threshold-dependent response.
- Side-view thickness measurements were available only for stiff-post tissues, restricting active-stress analyses to μHTs working against stiff-posts.
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Key expert perspectives
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“We knew from our prior studies that mechanical resistance and mechanical stress could bring out the HCM phenotype. By [using] something that's structurally more like a real heart, we could push [the tissue] to be mature enough to see a disease phenotype.”
Implication
High afterload and fibroblast density may synergistically unmask MYBPC3 hypercontractility in engineered tissues; leaves open relevance to clinical HCM progression.
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 (μHT) 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 MYBPC3 (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 MYBPC3fs μHT hypercontractility, with tissues generating greater total active force at both 5% and 25% added cFB. We also observed afterload- and cFB-dependent remodeling of Ca2+ handling, 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 MYBPC3fs μHT exhibited blunted improvements in Z-disc alignment with increasing cFB content, whereas cardiomyocytes within the isogenic control μHT showed progressive structural ordering as cFB density increased. Finally, the MYBPC3fs μHT 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.
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Cite This Study
Jiang et al. (2026) studied Hypertrophic cardiomyopathy. MYBPC3 frameshift variant (G1206fs) with mechanical stress and fibroblast enrichment vs. Isogenic control iPSC-derived cardiomyocytes was evaluated on Total active force.