Biology subjects

Hocini, M.

Publications and source records attributed to Hocini, M..

3 recordsLinked to original sources

bioRxiv2026

Desmin p.R406W mutation is associated with arrhythmias through structural and electrophysiological remodeling

Background and AimsMutations in the desmin (DES) gene cause a variety of cardiomyopathies associated with arrhythmias, yet the electrophysiological consequences of these variants remain largely uncharacterized. The aim of this study was to investigate the pathogenic mechanisms of the de novo DES p.R406W variant, which was identified in a 9-year-old patient who suffered from severe ventricular arrhythmias and sudden cardiac death without overt structural heart disease. MethodsHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the DES p.R406W variant (including the patients line) were compared to isogenic controls. Action potentials (AP) of hiPSC-CMs were recorded using patch-clamp. Furthermore, 3D engineered heart tissues (EHTs) were generated from hiPSC-CMs and their APs were recorded with sharp microelectrodes. Analytical techniques also included transmission electron microscopy (TEM) and integrated transcriptomic and proteomic profiling. Finally, a heterozygous knock-in (KI) mouse model carrying the Des p.R405W ortholog was evaluated through surface ECG, echocardiography and ex vivo cardiac optical mapping. ResultsThe DES p.R406W mutation prolonged AP duration in IM-R406W hiPSC-CMs and EHTs vs Control ones. Multi-omics analysis of EHTs revealed a dysregulation of genes and proteins involved in contractile function, cell adhesion, and electrical activity. TEM imaging revealed changes in Z-disc architecture in mutant tissues. Twenty-week-old Des p.R405W KI mice exhibited ventricular conduction slowing (prolonged QRS) and a high susceptibility to ventricular tachyarrhythmias, likely due to reentrant mechanisms. Mild hypertrophy was also observed, but only in females. ConclusionThe DES p.R406W variant is highly pathogenic, causing electrical and structural remodeling of the myocardium. This study highlights the effectiveness of hiPSC-CMs and EHTs in recapitulating the clinical phenotype of desminopathy, providing a platform for investigating the mechanisms of early-onset cardiac arrhythmias and SCD.

pathology↗

bioRxiv2023

Increased spontaneous Ca2+ activity in Cardiac Purkinje cells after myocardial infarction; A consequence of a dramatic shift of SERCA isoforms as potential adaptation to acute ischemia?

BackgroundStudies of Purkinje cells (Pcells) from canine hearts have suggested an increase of Ca2+-release by the sarcoplasmic reticulum (SR) but also reported a potential augmentation of SR-Ca2+-uptake after MI. Abnormal increase of SR-Ca2+-uptake in heart cells is novel and contrasts with the reduction of this function in cells of failing heart. Our study examined the origin of this increased SR-Ca2+-uptake by considering a change in SR-Ca2+ pump (SERCA2) expression in Purkinje fibers (PFs) post MI. MethodsPcells were isolated from canine hearts 48Hrs post MI. Intracellular Ca2+-activity was captured by confocal microscopy. Purkinje-typical Ca2+ events were analyzed to probe the regional Ca2+-dynamics within Pcells. A Purkinje-specific numerical model assisted in the interpretation of Ca2+-anomalies detected in Pcells Ca2+-transients. SR-Ca2+-uptake system was studied by immunofluorescence in Pcells from canine, ovine and human hearts post MI. SERCA protein and gene expressions in PFs and myocardium were measured by Western Blots and RT-qPCR in a classical porcine model of MI. Results48Hrs after MI, Pcells showed 60% increase in spark-rate and 37% acceleration of Ca2+ wave decay. In the model of normal wave, 35% increase of Ca2+-uptake rate reproduced the actual post-MI wave alterations. In apparent contrast with increased Ca2+-uptake rate, SERCA2 protein expression was reduced in canine, sheep, and human Pcells after MI. In pig MI model, the protein level of cardiac-specific SERCA2-splicing variant SERCA2a was reduced by 52% in the whole infarcted ventricle whereas the "non-cardiac" SERCA2b level was increased by 120%. In the infarcted regions, PFs showed 30% downregulation of SERCA2a gene expression and 630% upregulation of SERCA2b. ConclusionOur results confirm that elevated spontaneous Ca2+-activity in post-MI PFs is due to increased SR-Ca2+-uptake within Pcells. Data suggest that a replacement of "cardiac" SERCA2a by the "non-cardiac" SERCA2b sub-isoform in cardiac cells in response to ischemia is implicated in this alteration.

cell biology↗

bioRxiv2021

Optimizing large organ scale micro computed tomography imaging in pig and human hearts using a novel air-drying technique

Underlying electrical propagation in the heart and potentially fatal arrhythmia is the cardiac microstructure. Despite the critical role of muscle architecture, a non-destructive approach to examine not only myocyte orientation, but cellular arrangement in to laminar organization is lacking in hearts from translational animal models and humans. X-ray micro computed tomography using contrast enhancing agents achieves three-dimensional images at near-histological resolutions. However, imaging large mammalian hearts presents challenges including X-ray over-attenuation and loss of image contrast. The goal of this study was to rethink tissue pre-treatment to optimize, and benefit from micro computed tomography imaging resolution in large tissues. Whole pig and human hearts were dehydrated and perfused with a tissue reinforcing agent, hexamethyldisilazane, and slowly air-dried. Heart morphology was conserved and temporally stable. This enabled direct air-mounting for micro computed tomography imaging. Moreover, the desiccated tissue density was significantly reduced compared to the initial hydrated state (P=0.04). Three-dimensional image reconstructions of air-dried hearts segmented using a single intensity threshold revealed detailed microstructural architecture of myolaminae. Conversely, one-step segmentation of hearts loaded with contrast agents poorly estimated the gross anatomical morphology of the heart and lacked identification of tissue microarchitecture. Air-drying large mammalian hearts optimizes X-ray imaging of cardiac microstructure.

physiology↗