Myocardial remodeling is an inevitable risk factor for cardiac arrhythmias and can potentially be corrected with cell therapy. Although the generation of cardiac cells ex vivo is possible, specific approaches to cell replacement therapy remain unclear. On the one hand, adhesive myocyte cells must be viable and conjugated with the electromechanical syncytium of the recipient tissue, which is unattainable without an external scaffold substrate. On the other hand, the outer scaffold may hinder cell delivery, for example, making intramyocardial injection difficult. To resolve this contradiction, we developed molecular vehicles that combine a wrapped (rather than outer) polymer scaffold that is enveloped by the cell and provides excitability restoration (lost when cells were harvested) before engraftment. It also provides a coating with human fibronectin, which initiates the process of graft adhesion into the recipient tissue and can carry fluorescent markers for the external control of the non-invasive cell position. In this work, we used a type of scaffold that allowed us to use the advantages of a scaffold-free cell suspension for cell delivery. Fragmented nanofibers (0.85 µm ± 0.18 µm in diameter) with fluorescent labels were used, with solitary cells seeded on them. Cell implantation experiments were performed in vivo. The proposed molecular vehicles made it possible to establish rapid (30 min) electromechanical contact between excitable grafts and the recipient heart. Excitable grafts were visualized with optical mapping on a rat heart with Langendorff perfusion at a 0.72 ± 0.32 Hz heart rate. Thus, the pre-restored grafts’ excitability (with the help of a wrapped polymer scaffold) allowed rapid electromechanical coupling with the recipient tissue. This information could provide a basis for the reduction of engraftment arrhythmias in the first days after cell therapy.

The occurrence of atrial fibrillation (AF), one of the most socially significant arrhythmias, is associated with the presence of areas of fibrosis. Fibrosis introduces conduction heterogeneity into the cardiac tissue and, thus, may be a substrate for spiral wave reentry, which provokes the onset of AF and is often associated with its persistence. Despite results from computer and animal models of cardiac tissues, data on the conditions under which microreentries occur in human tissues are limited. In this work, we conducted a study of the new approach to modeling the fibrous atrial tissue, which takes into account the cellular structure and conduction in fibrosis areas. Using the Potts model, we created a realistic texture of atrial tissues remodeled by fibroblasts and showed the presence of pathways in such a system with a low proportion of fibroblasts. Our study revealed the relationship between the shape of the cells’ action potential, their location in the tissue, and the direction of the wave propagation. The wavefront obtained in the model creates a dynamic heterogeneity of the tissue, which affects the migration and pinning of spiral waves, and explains the formation of microreentries in the cardiac tissue. In the future, such a model can become a potential tool for predictive modeling of AF and the search for ablation target identification.

Modern therapies aimed at stimulating heart vascularization are critical for regenerating damaged heart tissue and treating ischemic heart disease. Approaches based on developmental biology concepts, particularly those involving the use of cells to coordinate vascular network formation, are of great interest. In this context, epicardial mesothelial cells (MCs) have emerged as a key regulator of blood and lymphatic vessel development during cardiogenesis. However, therapeutic targeting of MCs remains challenging because of anatomical constraints and the difficulties related to isolation of viable cell cultures for research. In this study, we demonstrate for the first time that the pericardial fluid contains cell layers, being an easily accessible source of cardiac MCs. These cells exhibit a characteristic epithelial-like morphology and robust in vitro proliferation, and an ability to undergo epicardial-to-mesenchymal transition in response to TGFβ1. They secrete a broad range of proangiogenic and proinflammatory factors and exert a potent effect on endothelial cells, stimulating proangiogenic behavior and promoting vascular structure formation on Matrigel^TM. Treating MCs with TGF-β1 enhances the secretion of VEGF, G-CSF, GM-CSF and MCP-3, thereby boosting their proangiogenic properties. Therefore, pericardial fluid is an easily accessible source of MCs for studying their regulatory mechanisms, for being applied in tissue engineering, and for developing approaches to improve heart vascularization.

Epicardial mesothelial cells (EMCs), which form the epicardium, play a crucial role in cardiac homeostasis and repair. Upon damage, EMCs reactivate embryonic development programs, contributing to wound healing, progenitor cell amplification, and regulation of lymphangiogenesis, angiogenesis, and fibrosis. However, the mechanisms governing EMC activation and subsequent regulation remain poorly understood. We hypothesized that hepatocyte growth factor (HGF), a pleiotropic regulator of various cellular functions, could modulate EMC activity. To verify this hypothesis, we developed HGF-overexpressing mesenchymal stromal cell sheets (HGF-MSC CSs) and evaluated their effects on EMCs in vitro and in vivo. This study has revealed, for the first time, that EMCs express the c-Met (HGF receptor) on their surface and that both recombinant HGF and HGF-MSC CSs secretome cause c-Met phosphorylation, triggering downstream intracellular signaling. Our findings demonstrate that the HGF-MSC CSs secretome promotes cell survival under hypoxic conditions by modulating the level of autophagy. At the same time, HGF-MSC CSs stimulate EMC proliferation, promoting their amplification in the damage zone. These data demonstrate that HGF-MSC CSs can be considered a promising regulator of epicardial cell activity involved in heart repair after ischemic damage.

Cardiac arrhythmias are a major cause of cardiovascular mortality worldwide. Functional heterogeneity of cardiac tissue is an inevitable arrhythmogenic condition that may create nonlinear wave turbulence or reentry with subsequent arrhythmia initiation. The relation between propagation heterogeneity and the onset of reentry is of great theoretical and practical importance. Here, we present a conceptual representation of heterogeneous tissue expressed through alternating local and global tissue anisotropy with discreteness of membrane conductance. To contrast the influence of distributed heterogeneity, we investigated the interaction of a highfrequency wavetrain at a sharp anisotropy-symmetric obstacle. The revealed tendency of a heterogeneous system to form reentry was formalized into the single concept of a vulnerable frequency corridor that can be estimated experimentally. Using the joint in vitro–in silico approach, we defined an anomalous stable growth of a unidirectional block in the vicinity of an obstacle, depending on the direction of the anisotropy vector. This effect explains the limited applicability of homogeneous models to predicting the occurrence of primary reentry. Furthermore, computer simulations showed the special role played by other possible mechanisms of excitation, as ephaptic intercellular coupling, in the formation of a unidirectional

1. Cell motility, shape supporting, and intracellular signaling are followed by changes in cell morphology and cytoskeleton. The cell reaction and the reorganization of the cytoskeleton occurs in a single volume of the cytoplasm and affects all components of the cytoskeleton: intermediate filaments, microtubules and microfilaments. A promising way to manipulate cells is magnetic nanoparticles that control cellular physiology. This approach is called magnetogenetics and has found application in various fields of cell and molecular biology. Using a magnetic field, it is possible to non-invasively regulate biochemical processes, migration and changes in the morphology of cells with magnetic nanoparticles. Our work opens up new possibilities for spatial manipulation of individual cytoskeletal components in vitro and operates biochemical pathways associated with individual cytoskeletal components.