Tissue and organ regeneration is a major challenge in modern medicine. The inability or limited potential to restore the functional structure of damaged tissues in humans, such as myocardium, has led to the search for novel therapeutic approaches. Stem cell (SC)-based therapies appear to be particularly promising. SCs have the ability to differentiate into other cell types in response to certain environmental cues. A special type of SCs are induced pluripotent stem cells (iPSCs), which have the ability to differentiate into all cell types that make up the adult organism and can be maintained in culture indefinitely. iPSCs are artificially generated in the laboratory, so their use in biomedical research does not raise ethical controversies. Therefore, iPSCs are excellent tools for modeling disease or testing new drugs, and are a potential source of cells for transplantation and repair of damaged organs. Importantly, iPSCs, like other cells, secrete bioactive nanostructures called extracellular vesicles (EVs). EVs are nano-sized vesicles that contain bioactive components such as proteins, lipids and RNA molecules. EVs can enter other cells and, upon delivery of their cargo, alter the behavior and function of target cells. Thus, the use of both iPSCs and EVs secreted by these cells represents an attractive tool in regenerative medicine. Given that the natural environment for SCs niche is characterized by reduced oxygen concentration (known as hypoxia), in this project we aimed to investigate the effect of oxygen concentration on the molecular characteristics and biological properties of human iPSCs (hiPSCs) and their secreted EVs.

To achieve this goal, we used advanced research methods to verify the molecular composition of hiPSCs and their EVs. We also investigated the effects of hiPS-EVs derived from different oxygen conditions on various cell types of the heart, including cardiomyocytes (contractile cells), endothelial cells, and fibroblasts. In addition, we directly tested the therapeutic properties of hiPS-EVs in a mouse model of cardiac dysfunction (Figure 1). The results indicate that oxygen concentration alters the molecular composition of both cells and EVs, which is reflected in their biological activity. We have demonstrated beneficial effects of hiPS-EVs on various cardiac cell populations, such as enhanced survival, resistance to oxidative stress, increased proliferation and maintenance of cellular phenotype. Using an in vivo study of cardiac injury in experimental mice, we confirmed the beneficial effects of hiPS-EV-based therapy.

In conclusion, the results obtained in this project provided new insights into the effect of oxygen concentration in the hiPSC microenvironment on the molecular composition and biological functions of hiPSCs and their secreted EVs. These results open new avenues in a variety of biomedical research areas. Importantly, the beneficial effects of hiPS-EVs on cardiac cells confirmed in this project can be further advanced in regenerative medicine, including experimental cardiology. Ultimately, the goal is to improve the health of patients.