Alerni, N. | Search bioRxiv

bioRxiv2026

Multi-scale electrophysiological characterization of human cardioids reveals progressive maturation

Background: Human induced pluripotent stem cell-derived cardiomyocytes are valuable for cardiac disease modelling and drug testing but remain limited by immature structural and electrophysiological properties in conventional two-dimensional cultures. Three-dimensional cardiac models, including cardioids, provide a more physiological environment through multicellular organization and enable tissue-level functional analysis. Their electrophysiological properties and maturation, however, remain incompletely characterized. Methods: We performed an integrated electrophysiological characterization of human cardioids over the first three weeks of maturation using sharp microelectrode recordings, calcium transient measurements, whole-cell patch clamp recordings, immunofluorescence, transcriptomic analysis, and pharmacological interventions. Results: During maturation, cardioids exhibited progressive electrophysiological maturation, characterized by more physiological resting membrane potentials (-54.0{+/-}3.1mV to -68.1{+/-}1.2mV), increased action potential amplitude (73.5{+/-}4.8mV to 101.7{+/-}2.1mV) and upstroke velocity (44.3{+/-}5mV/ms to 86.6{+/-}8.4mV/ms), and shorter action potential duration (178.9{+/-}8.7ms to 144.0{+/-}4.8ms at 1Hz stimulation). These changes were associated with progressively increased INa density and enhanced SCN5A mRNA and Nav1.5 protein expression, consistent with progressive maturation of cardiac excitability. IKr current and KCNH2/hERG expression were already present at early maturation stages and remained stable, as evidenced by preserved sensitivity to dofetilide-blockade. Pharmacological inhibition of barium- and HMR-sensitive currents altered resting membrane and/or action potential characteristics in intact cardioids, whereas in isolated cardiomyocytes classical IK1 remained undetectable and IKs was small, highlighting a certain degree of persisting immaturity of the model. Conclusions: These findings demonstrate that human cardioids undergo progressive electrophysiological maturation and provide complementary tissue- and cellular-level insights into cardiac function, establishing their suitability for investigating INa and IKr-related cardiac pathologies.

physiology↗

bioRxiv2023

Simultaneous assessment of mechanical and electrical function in Langendorff-perfused ex-vivo mouse heart

BackgroundThe Langendorff-perfused ex-vivo isolated heart model has been extensively used to study cardiac function for many years. However, electrical and mechanical function are often studied separately - despite growing proof of a complex electro-mechanical interaction in cardiac physiology and pathology. Therefore, we developed an isolated mouse heart perfusion system that allows simultaneous recording of electrical and mechanical function. MethodsIsolated mouse hearts were mounted on a Langendorff setup and electrical function was assessed via a pseudo-ECG and an octapolar catheter inserted in the right atrium and ventricle. Mechanical function was simultaneously assessed via a balloon inserted into the left ventricle coupled with pressure determination. Hearts were then submitted to an ischemia-reperfusion protocol. ResultsAt baseline, heart rate, PR and QT intervals, intra-atrial and intra-ventricular conduction times, as well as ventricular effective refractory period, could be measured as parameters of cardiac electrical function. Left ventricular developed pressure (DP), left ventricular work (DP-heart rate product) and maximal velocities of contraction and relaxation were used to assess cardiac mechanical function. Cardiac arrhythmias were observed with episodes of bigeminy during which DP was significantly increased compared to that of sinus rhythm episodes. In addition, the extrasystole-triggered contraction was only 50% of that of sinus rhythm, recapitulating the "pulse deficit" phenomenon observed in bigeminy patients. After ischemia, the mechanical function significantly decreased and slowly recovered during reperfusion while most of the electrical parameters remained unchanged. Finally, the same electro-mechanical interaction during episodes of bigeminy at baseline was observed during reperfusion. ConclusionOur modified Langendorff setup allows simultaneous recording of electrical and mechanical function on a beat-to-beat scale and can be used to study electro-mechanical interaction in isolated mouse hearts.

physiology↗