Vindictive induced pluripotent stem cells
Induced pluripotent stem cells retain the characteristics of the original cell linesDmitry Safin, Compulenta
Two groups of biologists presented evidence that "reprogrammed" mature cells differ from each other and from embryonic stem cells (ESCs).
Induced pluripotent stem (iPS) stem cells, which are obtained on the basis of mature cells by "forced" expression of certain genes, are considered one of the most important achievements of modern medicine. It was assumed that they would become analogues of ESCs, free from ethical restrictions. Last year, however, data began to arrive that iPS cells do not correspond to traditional ESCs in their characteristics.
The results of two new studies indicate a possible reason for this: it turns out that mature cells retain "memories" of the original type of tissue even after turning into iPS cells.
The authors of the first study tried to obtain blood cells using different types of stem cells. In the case of iPS cells, which were themselves created on the basis of blood cells of adult mice, the task was solved quite easily, but scientists failed to reproduce this result in experiments with fibroblasts (connective tissue cells). Further analysis showed that each iPS cell line has its own indicators of DNA methylation - modification of the DNA molecule without changing the nucleotide sequence.
Biologists also managed to establish that stem cells obtained without the participation of "reprogramming" factors by the method of nuclear transplantation are devoid of these disadvantages. Core transplantation refers to cloning technologies and was used in the cultivation of Dolly sheep.
The scheme of the process of core transplantation
(illustration from the website Biotechnologyonline.Gov.Au ).
The second group of scientists worked with four types of iPS cells, which were based on leukocytes, muscle progenitor cells, B-lymphocytes and fibroblasts of mice. As it turned out, iPS cell lines are easily distinguished from each other by gene expression indicators, but over time, when cells are passioned, the differences disappear.
"Obviously, the "reprogramming" of cells is a long process, and it does not end at the iPS stage," concludes Konrad Hochedlinger, a participant in the second study from the Massachusetts General Hospital.
Full versions of the reports will be published in the journals Nature (K. Kim et al., Epigenetic memory in induced pluripotent stem cells) and Nature Biotechnology (Jose M Polo et al., Cell type of origin influences the molecular and functional properties of mouse induced pluripotent stem cells).
Prepared based on the materials of ScienceNOW: The Persistence of Memory ... in Reprogrammed Cells.
Portal "Eternal youth" http://vechnayamolodost.ru20.07.2010