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.

Cardiac arrhythmias are common disorders that can be fatal. Modern methods of treating bradyarrhythmias include the implantation of pacemakers and cardioverter–defibrillators. However, implantable devices can cause various complications related to the electrodes installed inside the heart, including infection. Less invasive heart rhythm modulation could be beneficial for some cohorts of patients. Here, we demonstrate an alternative approach to heart pacing based on thermogenetics. We used adeno-associated viruses to deliver genetic human transient receptor potential subfamily V member 1 (TRPV1), a heat-sensitive cation channel, into isolated cardiomyocytes and the mouse heart. This allowed us to induce action potentials and control contractility using short heat pulses delivered by infrared laser illumination. Using this approach, we demonstrated the thermogenetic pacing of isolated cardiomyocytes in vitro and in the mouse heart in vivo . Our results demonstrate the potential of thermogenetics for developing therapeutic strategies for heart rhythm modulation.

Mesenchymal stem cells are a cell population with the ability to self-replicate and differentiate into various types of somatic cells. The present review focuses on the potential of mesenchymal stem cell cultures for cell therapy using transplantable cells or tissue-engineered constructs, and the paracrine factors secreted by mesenchymal stem cells. The methodological aspects of the use of these cells in various diseases both in clinical and preclinical trials have been demonstrated through examples of experimental therapy, with an overview of their primary mechanisms. In the context of cell therapy, mesenchymal stem cells are of significant interest because of their abundance and renewability. Although the differentiation pathways of mesenchymal stem cells are not yet fully elucidated, the cells themselves play a pivotal role in stem cell biology in view of their regulatory properties, including immunomodulatory, antiapoptotic, proliferation-promoting, and antifibrotic effects. It is important to emphasize that the paracrine functions of mesenchymal stem cells are the primary factor contributing to their enhanced integration into tissues, when compared to induced pluripotent stem cells, particularly in the context of cardiac tissue engineering. The review also highlights the role of exogenous factors, such as substrates, in modulating the efficacy of the paracrine effects of mesenchymal stem cells, which is crucial for identifying the optimal cellular microenvironment to enhance therapeutic outcomes without adverse effects.

Introduction: Preservation of isolated hearts in cardioplegic solution at normothermia is a promising strategy for increasing the organ lifespan. Further development of this strategy and search for new products for solution delivery can help optimize the technology of donor heart transportation. Objective: The study was aimed to test the efficacy of device for normothermic constant perfusion flow with innovative lines for the cardioplegic solution delivery (CardioSystemPharma, Khimki, Moscow Region, Russia) according to the Langendorff mode in comparison with a system based on nodes and tubes of Radnoti Langendorff Constant Perfusion Flow Apparatus (ADInstruments, Colorado Springs, USA) in a series of experiments on rat hearts.Methods: The innovative cardioplegic delivery system (CardioSystemPharma) and traditional perfusion system (Radnoti) were compared in experiments on rat hearts at normothermia without cardioplegic solution and using the cardioplegic solution Normacor (Mosfarm, Moscow Region, Russia). The time until complete cardiac arrest and the changes in the NADH coenzyme fluorescence were recorded. After cardiac arrest, immunohistochemical staining of ventricular sections was performed to detect myocardial injury during perfusion.Results: It was shown that the innovative cardioplegic delivery system was not inferior to the traditional perfusion system (Radnoti) and even surpassed it in terms of the time duration for preservation of the isolated heart. It was found that the using of elevated glucose concentration during normothermic perfusion could significantly increase the organ lifespan. The efficacy of normothermic perfusion in the experiment was confirmed by monitoring cellular respiration through recording the NADH fluorescence.Conclusion: Testing showed that long-term preservation under normothermia with usage of an innovative delivery system of Russian manufacture is a promising replacement for Radnoti solution delivery system. Received 16 October 2024. Revised 23 November 2024. Accepted 10 December 2024. FundingThe study was carried out within the framework of the project “Innovative cardioplegic lines for cardiac surgery” under the Agreement on the provision of a grant from the Government of the Moscow Region in the fields of science, technology, engineering and innovation No. 12/04-24 dated 04/27/2024. Conflict of interestThe authors declare no conflict of interest. Contribution of the authorsConception and study design: V.A. Tsvelaya, S.D. Robustova, V.S. Kachan, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, K.I. AgladzeData collection and analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. Turchaninova, V.A. TsvelayaStatistic analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. TurchaninovaDrafting the article: S.D. Robustova, V.S. Kachan, D.V. Kononova, Z.V. Obrazumova, E.A. Turchaninova, V.A. TsvelayaCritical revision of the article: S.D. Robustova, E.A. Turchaninova, V.A. Tsvelaya, K.I. AgladzeFinal approval of the version to be published: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, E.A. Turchaninova, S.S. Bakumenko, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, V.A. Tsvelaya, K.I. Agladze

Fibrotic scars post-myocardial infarction disrupt cardiac conduction, causing arrhythmias. We developed a minimized 4-component cocktail (CHIR99021/BMP4/Activin A/IWP2) for efficient fibroblast-to-cardiomyocyte transdifferentiation. The use of the developed four-component protocol enables the generation of cells with electrical excitability and key cardiomyocyte markers, as evidenced by 56–83% of cells expressing α-actinin. This level of partial reprogramming of fibroblast cells into cardiac cells is sufficient to restore cardiac tissue conductivity, with an efficiency that exceeds the critical percolation threshold. Systemic delivery of components is safe, but requires further optimization, which will open up opportunities for localized delivery through smart substrates and combinations with cell therapy. Minimization of the transdifferentiation cocktail is not a compromise, but a strategic advantage that provides an optimal balance between functional efficiency and clinical applicability, including safety, delivery, and manufacturing.

A critical obstacle in cardiac cell therapy is the unpredictable and poorly understood initial electrophysiological integration of grafted cardiomyocytes into the host tissue, a process that dictates therapeutic success and arrhythmic risk. Current models fail to capture the earliest stages of functional coupling formation. Here, we employed a tailored bioengineering platform, where single cardiomyocytes were stabilized on minimalist electrospun polycaprolactone (PCL) nanofibers, to model the "graft-host" interface and study the dynamics of excitation wave transmission in real-time. Using high-speed optical mapping enhanced by a custom SUPPORT neural network, we achieved the first quantitative insights into the efficiency of nascent intercellular contacts. We determined that within the first 3 hours, these initial connections are 39-44 times less effective at conducting excitation than mature contacts within the native monolayer, explaining the observed partial (46%) synchronization of grafted cells. This work provides the first direct measurement of the functional deficit during the initial minutes and hours of graft integration. It establishes that simple, inert polymer fibers can act as a catalytic scaffold to enable this fundamental biological process, offering a powerful strategy to deconstruct and ultimately control the integration of engineered tissues (or cells) for safer cell therapies.