Discovery of the Phenomenon of Intracellular Development of Cardiac Stem Cell: A New Step in Understanding of Biology and Behavior of Tissue-Specific Stem Cells

In our experiments with an in vitro culture of rat cardiac cells, we identified and described for the first time the phenomenon of intracellular development of CSCs in mature CMs with formation of the “cell-in-cell structures” (CICSs). Recently, we have confirmed the reproducibility of our results and existence of this phenomenon in rats of different age groups, 1-year-old bull, adult mice and humans. Moreover, we demonstrated the 5–10 times increase in the amount of CICSs after exposure of in vitro cultures to hypoxia and acidosis, that is, these conditions stimulate intracellular development of CSCs. Our data strongly suggest that transitory amplifying cells (TACs), which release from CICSs, are present as a very rare cell population in adult and old rats. Therefore, we assume that TACs are important for renewal of myocardium during ontogenesis. TACs should be considered as the major source of cells that can reduce myocardial damage in adult mammals with various pathologies of the cardiovascular system. In conclusion, precise and exhaustive analysis of the phenomenon of intracellular development of CSCs, CICSs and TACs will pave the way for cell technologies of new generation in regenerative medicine