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MOSCOW, June 9. /TASS/ Russian scientists have demonstrated that stem cells obtained by reprogramming from normal cells of an organism scarcely differ from the reference stem cells. This discovery has been recently reported on the popular-science web portal "Cherdak" at TASS, with the reference to the press service of Moscow Institute of Physics and Technology (MIPT).
The results of the study have been published in the journal Cell Cycle. It is noted in the article, that this investigation could hasten the in vitro creation of artificial organs. The researchers have concluded that reprogramming process does not imprint on the induced stem cells. All minor differences between induced and embryonic cells have been attributed by scientists to the influence of arbitrary factors, as reported in the press-release.
Embryonic stem cells vs. reprogrammed stem cells
Pluripotential stem cells can divide through numerous cycles and transform into other cell types. They serve as a sort of internal repair system in many tissues, and theoretically could be used to derive any organ of the body. The problem is that there are no pluripotent stem cells in the body of an adult human. This particular type of cells is specific only for cells of an early embryonic development. For the medical purposes, it was suggested to take stem cells from early stage embryos, but in practice this way is obviously restricted both from ethic and from technical sides.
The alternative to the embryonic stem cells is the induced pluripotent stem cells. In 2007, the Japanese scientists have shown that the ordinary stem cells could be transformed into the stem ones by means of several manipulations turning off the genes responsible for the cell specialization and turning on the genes which are active in a stem cell. However, up to now, it is not clear, whether the induced (reprogrammed) stem cells differ from the embryonic.
Russian scientists from the Institute of General Genetics, Federal Research Center for Physicochemical Medicine (FRC PM), MIPT, and Kazan Federal University have compared embryonic stem cells, three types of cells produced from stem cells (neurons, fibroblasts - the cells of connective tissues, and from epithelium of retina), as well as three types of stem cells reprogrammed back from the ordinary cells. All these cells have the same gene set, and the differences between them have been controlled only by the different activity of some genes.
Scientists have analyzed the transcriptome – the set of all products encoded, synthesized and used in a cell. Moreover, they have identified the methylated (chemically modified with methyl groups) DNA areas, because methylation plays a critical role in cell specialization and decrease the gene activity. As a result, it has been concluded, that the induced stem cells of all three types (starting from neurons, fibroblasts, and epithelium) only in minor extent differ from the original embryonic. All the tiny variations in the mechanisms governing the gene activity could be attributed to the arbitrary factors.
"During the study, we have also formulated an optimal strategy of generating induced pluripotent cells." - tells Dmitry Ischenko, the Ph.D. student of MIPT and the research assistant from FRC PM. "If one starts the experiment with the embryonic cells, then let it transform into 5 different types of specialized cells and afterward reprogram them back into stem cells, the probability to find in all five groups the same stem cell as the original embryonic one, is 95%."
Clearly, no one is going to convert embryonic stem cells into neurons and reprogram them into induced stem cells – that would be too time-consuming and expensive. But the approved similarity between embryonic and reprogrammed stem cells make the last ones a very promising tool for the cell therapy. Moreover, understanding the mechanisms of cell growth regulation together with tiny adjustment of cell specialization is a key point for further investigations of organism development and potentially of clarifying the transformation of ordinary cells to cancer ones.