Biology subjects

Pavlovic, D.

Publications and source records attributed to Pavlovic, D..

3 recordsLinked to original sources

bioRxiv2022

Generation of cardiomyocytes from human induced pluripotent stem cells resembling atrial cells with ability to respond to adrenoceptor agonists

Cardiovascular disease is the leading cause of global mortality and morbidity. Cardiac dysrhythmias contribute significantly to this disease burden. Atrial fibrillation (AF) is the most common chronic dysrhythmia. Human induced pluripotent stem cell-derived atrial cardiomyocytes (hiPSC-AMs) present an exciting new model for AF but currently fail to reach maturity and so are limited in translational potential currently. We report a new approach using a combination of Gremlin 2 and retinoic acid treatment of human iPSCs for generating cardiomyocytes resembling atrial cells. More than 40% of myocytes generated by this approach showed rod-shaped morphology, expression of cardiomyocyte proteins (including RyR2 receptors, a-actinin-2, F-actin) and typically a striated appearance, all of which were broadly similar to the characteristics of adult atrial myocytes. Isolated myocytes were electrically quiescent until stimulated to fire action potentials with an atrial myocyte profile and an amplitude of approximately 100 mV, arising from a resting potential of approximately -70 mV. Single-cell RNA sequence (scRNASeq) analysis showed a high level of expression of several atrial specific transcripts including NPPA, MYL7, HOXA3, SLN, KCNJ4, KCNJ5 and KCNA5. Amplitudes of calcium transients recorded from spontaneously beating cultures were increased by the stimulation of -adrenoceptors (activated by phenylephrine and blocked by prazosin) or {beta}-adrenoceptors (activated by isoproterenol and blocked by CGP20712A). Thus, our new method provides an efficient approach for differentiating human atrial myocytes with mature characteristics from hiPSCs. This preparation will be very useful for studying signalling pathways in human atrial myocytes, and provides a valuable model for investigating atrial fibrillation and drug discovery.

bioengineering↗

bioRxiv2022

Male sex hormone and reduced plakoglobin jointly impair atrial conduction and cardiac sodium currents

Androgenic anabolic steroids (AAS) are commonly abused by young men. Male sex associates with earlier manifestation of common and rare cardiac conditions including atrial fibrillation and arrhythmogenic right ventricular cardiomyopathy (ARVC). Clinical data suggest an atrial involvement in ARVC. The disease is caused by desmosomal gene defects such as reduced plakoglobin expression. Analysis of clinical records from 146 ARVC patients identified male preponderance and increased prevalence of atrial arrhythmias in patients with definite ARVC. Definite patients displayed ECG changes suggesting atrial remodelling. To study mechanisms of atrial remodelling due to desmosomal vulnerability and AAS, young adult male mice, heterozygously deficient for plakoglobin (Plako+/-) and wildtype (WT) littermates, were chronically exposed to 5-dihydrotestosterone (DHT) or placebo. DHT increased atrial expression of pro-hypertrophic, fibrotic and inflammatory transcripts. DHT caused atrial conduction slowing, decreased peak sodium current density, reduced action potential amplitude and lowered the peak depolarisation rate in Plako+/- but not WT atria. Super-resolution microscopy revealed a reduction in Nav1.5 clustering in Plako+/- atrial cardiomyocytes following DHT exposure. These data reveal that AAS combined with plakoglobin deficiency cause pathological atrial electrical remodelling in young male hearts. AAS abuse may increase the risk of atrial myopathy in males with desmosomal gene variants.

molecular biology↗

bioRxiv2022

Increased early sodium current provokes familial atrial fibrillation and reduces effectiveness of sodium channel block

(1) AimsAtrial fibrillation (AF) is the most common cardiac arrhythmia. Pathogenic variants in genes encoding ion channels are associated with familial AF. The point mutation M1875T in the SCN5A gene, which encodes the -subunit of the cardiac sodium channel Nav1.5, has been associated with increased atrial excitability and familial AF. (2) MethodsWe designed a new murine model carrying the Scn5a-M1875T mutation enabling us to study the effects of the Nav1.5 mutation in detail in vivo and in vitro using patch clamp and microelectrode recording of atrial cardiomyocytes, optical mapping, ECG, echocardiography, gravimetry, histology and biochemistry. (3) ResultsAtrial cardiomyocytes from newly generated adult Scn5a-M1875T+/- mice showed a selective increase in the early (peak) cardiac sodium current, larger action potential amplitude and a faster peak upstroke velocity. Conduction slowing caused by the sodium channel blocker flecainide was less pronounced in Scn5a-M1875T+/- compared to wildtype atria. Overt hypertrophy or heart failure in Scn5a-M1875T+/- mice could be excluded. (4) ConclusionThe Scn5a-M1875T point mutation causes gain-of-function of the cardiac sodium channel. Our results suggest increased atrial peak sodium current as a potential trigger for increased atrial excitability and thus AF. Whats newO_LIThe point mutation M1875T in the C-terminal domain of the cardiac sodium channel Nav1.5 causes an increase in early peak sodium current in left atria. C_LIO_LIThe observed changes induced by this point mutation suggest an increase in peak sodium current as a cause of familial atrial fibrillation (AF). C_LIO_LIOur findings provide a possible explanation for the variable effectiveness of sodium channel blockers in patients with AF. Carriers of such sodium channel gain-of-function mutations may benefit more from tailored treatments. C_LI Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

molecular biology↗