Accurate detection of conduction disorders, a critical factor for arrhythmogenic risk assessment, is a key challenge in drug development and cardiovascular safety screening. This study presents a highly sensitive atomic force microscopy (AFM)-based biosensor using a dual-beating human pluripotent stem cell (hPSC)-derived organoid to discriminate between focal and conductive arrhythmic contractions. Analysis of the variance of the regression residuals revealed increased stochastic (random) fluctuations in unsynchronized clusters, indicative of arrhythmic instability. Mechanosensing assessed by force microscopy allows the differentiation of the vertical and lateral direction of contractile movement. The high biosensor sensitivity allowed detailed analysis of contractile behavior under pharmacological modulation with cardiomodulating drugs. Moreover, heptanol-induced arrhythmias were associated with inhibition of atrioventricular conduction, demonstrating the ability of the system to model mechanisms of conduction blockade. For the first time, an AFM-based transducer successfully discriminates focal from conductive arrhythmias, marking a significant advance in vitro cardiac biosensing. The dual organoid system enhances model robustness by reducing the variability inherent in single-cell studies, thereby improving translational relevance for cardiotoxicity assessment and precision medicine applications in cardiovascular health.

The combination of aminophylline and salbutamol is frequently used in clinical practice in the treatment of obstructive lung diseases. While the side effects (including arrhythmias) of the individual bronchodilator drugs were well described previously, the side effects of combined treatment are almost unknown. We aimed to study the arrhythmogenic potential of combined aminophylline and salbutamol treatment in vitro. For this purpose, we used the established atomic force microscopy (AFM) model coupled with cardiac organoids derived from human pluripotent stem cells (hPSC-CMs). We focused on the chronotropic, inotropic, and arrhythmogenic effects of salbutamol alone and aminophylline and salbutamol combined treatment. We used a method based on heart rate/beat rate variability (HRV/BRV) analysis to detect arrhythmic events in the hPSC-CM based AFM recordings. Salbutamol and aminophylline had a synergistic chronotropic and inotropic effect compared to the effects of monotherapy. Our main finding was that salbutamol reduced the arrhythmogenic effect of aminophylline, most likely mediated by endothelial nitric oxide synthase activated by beta-2 adrenergic receptors. These findings were replicated and confirmed using hPSC-CM derived from two cell lines (CCTL4 and CCTL12). Data suggest that salbutamol as an add-on therapy may not only deliver a bronchodilator effect but also increase the cardiovascular safety of aminophylline, as salbutamol reduces its arrhythmogenic potential.

Duchenne muscular dystrophy (DMD) is a devastating condition shortening the lifespan of young men. DMD patients suffer from age-related dilated cardiomyopathy (DCM) that leads to heart failure. Several molecular mechanisms leading to cardiomyocyte death in DMD have been described. However, the pathological progression of DMD-associated DCM remains unclear. In skeletal muscle, a dramatic decrease in stem cells, so-called satellite cells, has been shown in DMD patients. Whether similar dysfunction occurs with cardiac muscle cardiovascular progenitor cells (CVPCs) in DMD remains to be explored. We hypothesized that the number of CVPCs decreases in the dystrophin-deficient heart with age and disease state, contributing to DCM progression. We used the dystrophin-deficient mouse model (mdx) to investigate age-dependent CVPC properties. Using quantitative PCR, flow cytometry, speckle tracking echocardiography, and immunofluorescence, we revealed that young mdx mice exhibit elevated CVPCs. We observed a rapid age-related CVPC depletion, coinciding with the progressive onset of cardiac dysfunction. Moreover, mdx CVPCs displayed increased DNA damage, suggesting impaired cardiac muscle homeostasis. Overall, our results identify the early recruitment of CVPCs in dystrophic hearts and their fast depletion with ageing. This latter depletion may participate in the fibrosis development and the acceleration onset of the cardiomyopathy.

We have established an iPSC cell line carrying mutations in Plakophillin 2 (PKP2) and the A-kinase anchor protein 9 (AKAP9). Plakophilin 2 is an important protein of desmosomes, facilitating cell attachment and tissue strength. Its absence/mutation is associated with impaired cell adhesion and intracellular processes including calcium cycling and actin rearrangement. AKAP9, together with potassium channels and other enzymes, regulates cardiac repolarization. Mutations in both proteins are associated with arrhythmic cardiomyopathy, making this a valuable resource for the purposes of disease modeling and anti-arrhythmia drug testing.

Nijmegen breakage syndrome is a rare disease manifesting approximately in 1 out of 95 000 live births. It is caused, in most cases, by a deletion of 5 nucleotides in exon 6 of nibrin gene, resulting in production of truncated protein and chromosomal instability as functional nibrin is an important part of the homologous recombination pathway. Common symptoms include microcephaly, mild growth retardation, combined humoral and cellular immunodeficiency as well as high susceptibility to malignancies. We have reprogrammed fibroblasts from a patient carrying the founder mutation (homozygous) into pluripotent stem cells, obtaining a cellular model with no detectable nibrin expression.