Biology subjects

Kutschka, I.

Publications and source records attributed to Kutschka, I..

5 recordsLinked to original sources

bioRxiv2024

Polycystin-1 loss of function increases susceptibility to atrial fibrillation through impaired DNA damage response

BackgroundThe increasing prevalence of atrial fibrillation (AF) and chronic kidney diseases highlights the need for a deeper comprehension of the molecular mechanisms linking them. Mutations in PKD1, the gene encoding Polycystin-1 (PKD1 or PC1), account for 85% of autosomal dominant polycystic kidney disease (ADPKD) cases. This disease often includes cardiac complications such as AF. In cardiomyocytes, PC1 deletion reduces hypertrophic response to pressure overload but promotes baseline ventricular dysfunction, while deletion in fibroblasts ameliorates post-myocardial infarction fibrosis. Despite its known cardiac impact, the role of PC1 in atrial cardiomyocytes and arrhythmias is less understood. Here, we sought to investigate the role of PC1 in AF. MethodsWe used intracardiac programmed stimulation and optical mapping to evaluate AF inducibility in two mouse models, Pkd1 R3277C, which recapitulates human ADPKD progression, and cardiomyocyte-specific Pkd1 deletion, and their respective controls. Isolated adult mouse atrial cardiomyocytes, human iPSC-derived atrial cardiomyocytes (hiPSC-aCM), and HL-1 cells served as in vitro cellular models. Molecular mechanisms were evaluated using optical mapping and molecular and biochemical approaches. ResultsLoss-of-function PC1 mutations significantly increased AF susceptibility in vivo and facilitated local reentry in ex vivo left atrial appendages. Comprehensive in vitro experiments supported a direct effect of PC1 in atrial cardiomyocytes. PC1-deficient monolayers exhibited increased arrhythmic events, escalating into reentrant spiral waves post-tachypacing. Transcriptomics analysis revealed PC1-dependent regulation of DNA repair, with PC1 deficiency leading to increased DNA damage under stress. PARP1 inhibitors or nicotinamide riboside, which counteract DNA damage-related metabolic consequences, reduced in vitro arrhythmias PC1-deficient monolayers. Overexpression of the C-terminus of PC1 had the opposite effects in DNA repair genes, suggesting its regulatory effects in atrial cardiomyocytes through retinoblastoma/E2F. Analyses of human atrial tissue from non-ADPKD AF patients showed reduced levels of mature PC1, suggesting a broader relevance of impaired PC1 in AF. ConclusionsImpaired PC1 increases in vivo AF inducibility under programmed electrical stimulation and promotes in vitro arrhythmias in hiPSC-aCM and HL-1 cells. Our findings indicate that PC1 protects against DNA damage to reduce AF susceptibility.

pathology↗

bioRxiv2023

Structure and dynamics of human cardiac fibroblast nanotubes

Efficient and dynamic interactions between cardiac fibroblasts and their environment are essential for the maintenance of tissue homeostasis in healthy hearts and play an important role during pathological remodelling. Here, we investigate a relatively obscure mechanism through which human atrial fibroblasts communicate with each other, with other cells, and with the extracellular matrix (ECM) - nanotubes (NT). We investigated NT structure and dynamics in primary right atrial fibroblasts isolated from patients in sinus rhythm (SR) and atrial fibrillation (AF), in an immortalised human atrial fibroblasts cell line, and in intact human tissue, using a wide range of imaging approaches (including confocal microscopy, label-free reflection microscopy, rotating coherent scattering microscopy, and cryo-electron tomography). We show that fibroblasts maintain continuous NT activity in vitro, with numerous protrusions constantly probing the surrounding environment. NT structure and activity change during AF and following pharmacological (transforming growth factor-{beta}, latrunculin B) and environmental (hypoxia) interventions. We also show that cardiac fibroblast NT mediate intercellular organelle exchange and dynamically interact with ECM. Finally, we present evidence for the presence of fibroblast-borne NT in human atrial tissue. Our results advance our understanding of how cardiac fibroblasts interact with their environment. NT are versatile structures capable of both sensory and actuating functions, and offer a dynamic and rapid communication conduit that facilitates cell-cell and cell-extracellular matrix interactions.

cell biology↗

bioRxiv2023

The role of structural vs cellular remodeling in arrhythmogenesis: personalized computer models of atrial fibrillation.

Atrial fibrillation (AF) is a progressive disease involving both structural and functional remodeling. To investigate the contribution of cell-scale functional remodeling to AF pathogenesis, we combined personalized 3D anatomical models with pathology-specific ionic models. The latter were developed using recordings in myocytes isolated from patients in sinus rhythm, paroxysmal, postoperative, and persistent AF. To quantify AF dynamics, we developed a novel algorithm for locating RDs by backtracking the conduction velocity field from the wavebreak regions. We demonstrate that our novel algorithm is at least 700 times faster than the traditional phase singularity analysis. The inducibility of simulated AF was not pathology-dependent, but pathological models demonstrate a more extensive arrhythmogenic substrate compared to the sinus rhythm. AF driver locations depend on electrophysiological remodeling; differences between pathology-specific models are explained by differences in wavebreak patterns. Specifically, RDs tend to dwell in the regions with the highest wavebreak probability.

physiology↗

bioRxiv2022

Alteration of myocardial structure and function in RAF1associated Noonan syndrome: Insights from cardiac disease modeling based on patient-derived iPSCs

Noonan syndrome (NS), the most common among the RASopathies, is caused by germline variants in genes encoding components of the RAS-MAPK pathway. Distinct variants, including the recurrent Ser257Leu substitution in RAF1, are associated with severe hypertrophic cardiomyopathy (HCM). Here, we investigated the elusive mechanistic link between NS-associated RAF1S257L and HCM using three-dimensional cardiac bodies and bioartificial cardiac tissues generated from patient-derived induced pluripotent stem cells (iPSCs) harboring the pathogenic RAF1 c.770C>T missense change. We characterize the molecular, structural and functional consequences of aberrant RAF1 -associated signaling on the cardiac models. Ultrastructural assessment of the sarcomere revealed a shortening of the I-bands along the Z disc area in both iPSC-derived RAF1S257L cardiomyocytes, and myocardial tissue biopsies. The disease phenotype was partly reverted by using both MEK inhibition, and a gene-corrected isogenic RAF1L257S cell line. Collectively, our findings uncovered a direct link between a RASopathy gene variant and the abnormal sarcomere structure resulting in a cardiac dysfunction that remarkably recapitulates the human disease. These insights represent a basis to develop future targeted therapeutic approaches.

cell biology↗

bioRxiv2020

Personalization of mathematical models of human atrial action potential

Atrial cardiomyocytes demonstrate a wide spectrum of patient-specific, tissue-specific, and pathology-specific action potential (AP) phenotypes due to differences in protein expression and posttranslational modifications. Accurate simulation of the AP excitation and propagation in healthy or diseased atria requires a mathematical model capable of reproducing all the differences by parameter rescaling. In the present study, we have benchmarked two widely used electrophysiological models of the human atrium: the Maleckar and the Grandi models. In particular, patch-clamp AP recordings from human atrial myocytes were fitted by the genetic algorithm (GA) to test the models' versatility. We have shown that the Maleckar model results in a more accurate fitting of heart rate dependence of action potential duration (APD) and resting potential (RP). On the other hand, both models demonstrate the poor fitting of the plateau phase and spike-and-dome morphologies. We propose that modifications to L-type calcium current-voltage relationships are required to improve atrial models' fidelity.

biophysics↗