Increased Nuclear Susceptibility to Mechanical Stress in Phospholamban R14del Cardiomyopathy: A New Perspective on Disease Heterogeneity

Q: What is the clinical evidence from this study?

Population: Phospholamban (PLN) R14del cardiomyopathy. Intervention: Mechanical stress (cyclic uniaxial stretch at 4%, 1 Hz; pathological substrate stiffness 65-85 kPa; quasistatic overloading at 29% stretch; or in vivo hemodynamic loading pre-LVAD) vs. Isogenic control and wildtype hiPSC-CMs, physiological substrate stiffness (10-20 kPa), physiological loading in living myocardial slices, or mechanical unloading at heart transplantation / dilated cardiomyopathy and healthy control tissues. Primary outcome: Nuclear calcium handling, nuclear morphology (area, circularity, eccentricity, height, invaginations), nuclear injury (PML-NBs), mechanotransduction (LINC complex, YAP localization, traction forces), and cellular apoptosis (TUNEL, cleaved Caspase-3).

Q: What does this research mean for the field?

The phospholamban (PLN) R14del variant disrupts nuclear calcium handling and increases nuclear susceptibility to mechanical stress, causing mechanotransduction failure and cardiomyocyte apoptosis that can be mitigated by mechanical unloading. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.ESTABLISHES_NEW_DIRECTION.

Jort S.A. van der Geest; Atze van der Pol; Leon H.L. Hermans; Achmed H.S. Al-Khaqani; Jeroen I.M. van Asten; Marlinne A.M.E. van Roessel; Willem B. van Ham; Anneline S.J.M. te Riele; Alain van Mil; Vasco Sampaio‐Pinto; Pieter A. Doevendans; Zhiyong Lei; Vito Conte; Joost P. G. Sluijter; Carlijn V. C. Bouten

doi:10.64898/2026.10.23.761407

October 27, 2026

Increased Nuclear Susceptibility to Mechanical Stress in Phospholamban R14del Cardiomyopathy: A New Perspective on Disease Heterogeneity

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Key result

Mechanical unloading reverses nuclear vulnerability, mechanotransduction failure, and apoptosis in PLN R14del cardiomyopathy.

Why the study?

The highly variable clinical presentation of phospholamban (PLN) R14del cardiomyopathy cannot be fully explained by sarcoplasmic reticulum calcium handling disturbances alone. How the R14del variant affects nuclear calcium signalling and mechanosensing under mechanical loading remained unclear.

Does the PLN R14del variant impair nuclear calcium handling and increase nuclear susceptibility to mechanical stress in human cardiomyocytes and patient myocardium?

Key Points

To determine the impact of the phospholamban (PLN) R14del pathogenic variant on mechanosensing and nuclear calcium handling, and to explore how these defects relate to variable cardiomyopathy severity.
Subjected wild-type, isogenic control, and PLN R14del human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to cyclic uniaxial stretch (4%, 1 Hz for up to 48 hours) or hydrogels with physiological (10-20 kPa) and pathological (65-85 kPa) stiffness.
Evaluated nuclear calcium dynamics, cytoskeletal organization, PML nuclear bodies, and apoptosis via immunofluorescence, electron microscopy, TUNEL, and cleaved caspase-3 assays.
Examined cardiac tissue and living myocardial slices from PLN R14del patients, dilated cardiomyopathy patients, and healthy controls under mechanical loading and unloading conditions.
PLN R14del hiPSC-CMs exhibited abnormal calcium handling, including a lower intrinsic beating rate, prolonged rise times, and extended calcium transient decay duration (nuclear and cytosolic CTD90, CTD50, and CTD20).
During cyclic stretch, mutant cells displayed elevated PML nuclear bodies peaking at 6 hours and triggered a strain-avoidance response (reorienting nuclei and F-actin fibers ~30° away from the strain axis), but this failed to stop progressive apoptosis by 24 to 48 hours.
Across both substrate stiffness levels, mutant cells lacked adequate actin cap shielding, developed perinuclear desmin aggregates, and displayed nuclear dysmorphologies that normalized in patient cardiac tissue following mechanical unloading.

Structured PICO

Does the PLN R14del variant impair nuclear calcium handling and increase nuclear susceptibility to mechanical stress in human cardiomyocytes and patient myocardium?

P

Population

Human iPSC-derived cardiomyocytes, living myocardial slices (N=11 from a 52-year-old male), and paired cardiac tissue biopsies from PLN R14del cardiomyopathy patients, dilated cardiomyopathy patients, and healthy controls assessed under mechanical loading and unloading.

I

Intervention

Mechanical stimulation and loading: continuous cyclic uniaxial stretch (4%, 1 Hz for 0, 30 min, 6 hrs, 24 hrs, and 48 hrs); culture on polyacrylamide hydrogels with pathological stiffness (65-85 kPa) for 3 days; quasistatic mechanical overloading of living myocardial slices (stretched to 29% of original slice length); or in vivo hemodynamic loading (sampled at LVAD implantation).

C

Comparator

Isogenic control (PLN corr) and wildtype (PLN WT) hiPSC-CMs; culture on substrates with physiological stiffness (10-20 kPa); physiological loading conditions in living myocardial slices; mechanical unloading at the time of heart transplantation; and cardiac tissues from DCM patients and healthy controls.

O

Outcome

Nuclear calcium dynamics (CTD90, CTD50, CTD20, rise time, amplitude), nuclear morphology (area, circularity, eccentricity, height, envelope invaginations), nuclear injury marker expression (PML-NBs), cytoskeletal and LINC complex organization (F-actin, Desmin, Nesprin-1, nuclear YAP localization), cellular force generation (traction force microscopy), and cellular apoptosis (TUNEL and cleaved Caspase-3 positivity).surrogate

Identifies increased nuclear susceptibility to mechanical stress and impaired nuclear mechanotransduction as a novel pathological mechanism in PLN R14del cardiomyopathy that reverses upon mechanical unloading.

Implication

Nuclear mechanosensing defects may drive PLN R14del cardiomyopathy progression; leaves open whether mechanical unloading could alter disease course in patients.

Abstract

Background: Clinical presentation of phospholamban (PLN) R14del cardiomyopathy is highly variable, from asymptomatic carriers to rapidly progressing heart failure. which cannot be fully explained by its known disturbance of sarcoplasmic reticulum calcium handling. Nuclear calcium signalling, shaped by sarcoplasmic reticulum calcium release, plays a key role in regulating gene expression and the cellular response to mechanical stress. However, how the R14del variant affects nuclear signalling under mechanical loading remains unclear. Objective: To uncover the impact of the PLN R14del variation on mechanosensing, nuclear calcium handling and its link to the variable clinical representation of this cardiomyopathy. Methods: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the PLN R14del variant, an isogenic control, and wildtype control were subjected to mechanical stimulation by cyclic stretch or cultured on substrates with physiological (10-20 kPa) and pathological (65-85 kPa) stiffness. Nuclear morphology, cytoskeletal organisation and nuclear body formation were assessed via immunofluorescence. Traction force microscopy was used to assess mechanical stress and force generation. Cardiac tissues from PLN R14del cardiomyopathy patients, dilated cardiomyopathy patients, and healthy controls were analysed under mechanical loading (at left ventricular assist device implantation) and unloading (at heart transplantation). Living myocardial slices from a PLN R14del patient were maintained under overloading or physiological loading conditions. Results: PLN R14del hiPSC-CMs showed impaired nuclear calcium handling and, under mechanical stress, exhibited impaired mechanotransduction and elevated nuclear bodies. A strain-avoidance response was triggered but failed to prevent apoptosis. Nuclear abnormalities were confirmed in patient myocardial slices and cardiac biopsies which normalized upon relative mechanical unloading. Conclusion: PLN R14del increases nuclear susceptibility to mechanical stress, linking nuclear dysfunction to new disease insights and highlighting potential for mechanobiology-based therapeutic interventions.

Discussion

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Cite This Study

Geest et al. (2026) studied Phospholamban (PLN) R14del cardiomyopathy. Mechanical stress (cyclic uniaxial stretch at 4%, 1 Hz; pathological substrate stiffness 65-85 kPa; quasistatic overloading at 29% stretch; or in vivo hemodynamic loading pre-LVAD) vs. Isogenic control and wildtype hiPSC-CMs, physiological substrate stiffness (10-20 kPa), physiological loading in living myocardial slices, or mechanical unloading at heart transplantation / dilated cardiomyopathy and healthy control tissues was evaluated on Nuclear calcium handling, nuclear morphology (area, circularity, eccentricity, height, invaginations), nuclear injury (PML-NBs), mechanotransduction (LINC complex, YAP localization, traction forces), and cellular apoptosis (TUNEL, cleaved Caspase-3). PLN R14del cardiomyocytes exhibited impaired nuclear calcium handling and heightened nuclear vulnerability to mechanical stress, resulting in failed mechanotransduction and apoptosis that normalized upon unloading in patient tissue.

synapsesocial.com/papers/6ae2e29861f440a81e658f2e https://doi.org/10.64898/2026.10.23.761407

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Increased Nuclear Susceptibility to Mechanical Stress in Phospholamban R14del Cardiomyopathy: A New Perspective on Disease Heterogeneity

Key Points

Structured PICO

Implication

Abstract

Discussion

Cite This Study

Increased Nuclear Susceptibility to Mechanical Stress in Phospholamban R14del Cardiomyopathy: A New Perspective on Disease Heterogeneity

Key Points

Structured PICO

Implication

Abstract

Discussion

Cite This Study

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