AI Website BuilderIn healthy cardiomyocytes, action potentials propagate through the transverse-axial tubular system (TATS), ensuring synchronized and uniform calcium release across the cell. In heart failure structural remodeling of the TATS leads to asynchronous calcium signaling, contributing to impaired contractile function.
At OptoCARD, we have developed a novel imaging approach that enables simultaneous monitoring of TATS electrical activity and localized calcium release. Using this system, we identified TATS elements that fail to propagate action potentials. These non-conductive regions exhibit delayed and reduced calcium transients compared to electrically coupled sites, highlighting the crucial role of TATS electrical integrity in maintaining proper excitation-contraction coupling.
Our system also allows for precise probing and manipulation of subcellular membrane domains in optogenetically modified cardiomyocytes. Through this, we demonstrated that the TATS network is not only a passive conductor but intrinsically excitable, capable of generating self-sustained tubular action potentials with distinct electrophysiological properties.
More recently, our research has expanded to explore how T-tubular remodeling affects calcium release synchronization across multiple cells in multicellular cardiac preparations. This line of investigation opens new perspectives on the role of subcellular electrical architecture in shaping intercellular calcium dynamics, particularly under pathological conditions such as heart failure.
Optogenetics has revolutionized cardiovascular research, offering novel approaches for cardiac pacing, resynchronization therapy, and cardioversion. While previous studies have shown the feasibility of optically controlling cardiac function, most current stimulation strategies don’t consider the complex wave dynamics that occur across the entire epicardial surface.
At OptoCARD, we have developed an all-optical platform, enhanced by custom-designed software, to monitor and modulate cardiac electrical activity in a truly panoramic fashion. This system integrates a wide-field mesoscope with a high-resolution digital projector, enabling both supra- and sub-threshold optogenetic stimulation across the whole epicardium.
Our recent findings demonstrate that sub-threshold illumination - stimulation that does not directly trigger action potentials - profoundly influences cardiac electrical dynamics. Specifically, we observed that continuous sub-threshold optogenetic input increases the degree of cardiac alternans and significantly reduces ventricular tachycardia stability. This destabilization is primarily driven by amplified electrical oscillations induced by the light stimulus.
This innovative methodology provides the first proof-of-concept that cardiac dynamics can be precisely modulated using light, even in the absence of direct excitation. By enabling real-time, spatially controlled manipulation of cardiac excitation patterns, our approach opens new avenues for investigating both normal and pathological heart function - and for developing future non-invasive, light-based therapeutic strategies.
Leonardo Sacconi, Elisabetta Cerbai, Gerard Marchal, Valentina Romanelli, Chiara Palandri, Lorenzo Rezza
Genetic and non-genetic cardiac diseases lead to remodelling processes that can lead to conduction disturbances, mechanical dysfunctions, and life-threatening arrhythmias. There is an urgent need for predicting tools, but current models often lack integration between high-resolution functional and structural data, limiting their predictive power and physiological relevance.
At OptoCARD, we have developed a multi-modal optical strategy to directly correlate electrophysiological dysfunction with structural alterations in the context of Arrhythmogenic Cardiomyopathy using a mouse model.
We first employed high-resolution optical mapping to analyze conduction and action potential characteristics in entire healthy and diseased hearts. To obtain matching structural data from the same heart, we integrated advanced tissue clearing, and advanced light-sheet fluorescence microscopy, enabling 3D reconstruction of the myocardium at cellular resolution.
A key innovation was the optimization of a tissue transformation protocol for whole-heart clearing, allowing uniform visualisation of the heart. In parallel, we developed a dedicated cytoarchitectonic analysis software capable of identifying individual cells and mapping fiber alignment in three dimensions.
These detailed structural datasets were then used to build high-resolution, image-based computational models simulating action potential propagation across the entire organ. This allowed us to directly explore how cellular disorganization contributes to conduction abnormalities previously identified via optical mapping.
Our goal is to establish an integrated framework that combines structural and functional data to investigate the morpho-functional interplay underlying electrical dysfunctions in remodeled hearts. We believe this unified approach will offer new insights into the mechanisms of arrhythmogenesis and support the development of more predictive and physiologically accurate cardiac models.
Leonardo Sacconi, Elisabetta Cerbai, Francesco Giardini, Chiara Palandri, Gerard Marchal
Pioner et al., Circ. Res. 2023; Vermoortele et al, Commun Eng. 2024; Tolstik et al., Trends Biotechnol. 2024
Emerging evidence indicates that myosin motors adopt at least two distinct conformations in relaxed muscle. In the first, myosin motors extend outward from the thick filament backbone, while in the second confirmation, they fold back onto the filament surface, forming a structurally sequestered, energy-conserving “reserve” pool. Alterations in the balance between these confirmations have been implicated in congenital cardiovascular diseases such as Hypertrophic Cardiomyopathy, contributing to both mechanical and energetic dysfunction.
Understanding myosin conformational dynamics in the relaxed state is therefore essential to elucidate their role in force generation and energy homeostasis.
At OptoCARD, we have developed a label-free imaging methodology based on Second-Harmonic Generation (SHG) to directly probe and quantify the structural conformations of myosin in intact cardiac preparations. This technique allows us to non-invasively visualize myosin architecture with high spatial resolution and without the need for exogenous markers.
Using this approach, we have obtained novel structural insights into the R403Q mutation associated with HCM. Our findings reveal that this mutation not only destabilizes the thick filament organization but also enhances the intrinsic activity of myosin motors, disrupting the equilibrium between energy-conserving and force-generating states.
By integrating SHG imaging with energetic profiling, we aim to advance the understanding of myosin-based mechanisms of dysfunction in genetic cardiomyopathies and contribute to the identification of new therapeutic targets for restoring contractile efficiency.
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