Human myocardial slices reveal enhanced calcium handling following PLN-ASO therapy
M De Graaf, Z Iqbal, F E Deiman, C Ahlstrom, G Foldes, I Maxvall, P Davidson, P Van Der Meer, N Bomer, T Seidel, N Grote BeverborgAbstract
Background
The Phospholamban (PLN) R14del variant is highly prevalent in the Northern Netherlands and causes dilated (DCM) or arrhythmogenic cardiomyopathy (ACM) with a high risk of mortality. No disease-specific therapy is available, and PLN R14Δ/+ carriers often respond poorly to conventional heart failure treatment. Translating calcium-dependent genetic cardiomyopathies from mouse models to humans remains challenging due to fundamental species differences in calcium handling. Although PLN-targeting antisense oligonucleotides (ASOs) show efficacy in PLN-knockout mice, their mechanisms and human relevance remain unclear. Human myocardial slice cultures provide a unique ex vivo platform to bridge this translational gap, enabling mechanistic and therapeutic evaluation in patient-derived human myocardium.
Purpose
The objective of this study is to investigate the impact of PLN-targeting ASOs (PLN-ASOs) on contractile function in human myocardial slices.
Methods
Left ventricular tissue samples were collected from patients with DCM or PLN R14Δ/+ cardiomyopathy undergoing LVAD implantation or heart transplantation. Precision-cut myocardial slices were generated and treated with either vehicle or PLN-targeting ASOs (PLN-ASOs). Contractile function, calcium handling, and transcriptomic profiles were assessed to evaluate treatment effects.
Results
PLN-ASO treatment significantly reduced PLN expression at both mRNA and protein levels. This was accompanied by a dose-dependent increase in post-rest potentiation in both PLN R14Δ/+ and DCM slices, indicative of enhanced sarcoplasmic reticulum calcium handling. Contraction duration and time to peak was also decreased in a dose-dependent manner in PLN R14del slices suggesting enhanced calcium cycling. No significant changes were observed in contraction force, force-frequency relation, or refractory period. Subsequent mRNA sequencing confirmed calcium related pathways to be altered following PLN-ASO therapy. Transcriptomic analyses revealed altered expression of genes linked to calcium signalling pathways and calcium-sensitive actin filament regulation, pointing towards enhanced calcium sensitivity in myocardial contraction.
Conclusion
PLN-ASO therapy effectively silences PLN expression in human myocardial slices, leading to enhanced calcium cycling. These findings highlight its potential as a therapeutic strategy for PLN R14Δ/+ patients, with potential applicability to broader forms of heart failure.For image description, please refer to the figure legend and surrounding text.