Induced pluripotent stem cells: another breakthrough
In the laboratory of James Thomson, professor at the University of Wisconsin-Madison (University of Wisconsin-Madison), which in 1998 received the world's first culture of human embryonic stem cells, another step has been taken towards the therapeutic use of stem cells.
Attempts to create human embryonic stem cell lines with the genome of a patient in need of cell therapy, using the "Dolly method", by transferring the nucleus of a donor cell into an egg with a removed nucleus, have not brought success. The breakthrough was successful on another part of the front: at the end of 2007, Thomson and his collaborators simultaneously with a group of Japanese researchers received so-called induced pluripotent stem cells (iPSC). Viral vectors were used in both cases to deliver genes that return adult fibroblasts to the embryonic state. Despite the relative harmlessness of the adenoviruses used for this, infected cells are not ideal material for regenerative medicine. In addition, the genes necessary for reprogramming specialized adult cells into totipotent and capable of unlimited division are potential oncogenes.
Exactly a month ago, on March 1, 2009, the journal Nature published articles again by two teams of scientists from Scotland and Canada, who used a transposon instead of a viral vector – a "jumping gene", the remnants of which were removed from the genome after the delivery of four "stemness" genes. It remains to solve the problem of potential oncogenicity – and on March 26, 2009, an article appeared in the journal Science about the results of the work of the laboratory staff of the same Thomson (Junying Yu et al., Human Induced Pluripotent Stem Cells Free of Vector and Transgene Sequences). Reprogrammed stem cells, free of any extraneous genetic material, were obtained using a plasmid vector.
Plasmids – small circular DNA molecules in which transgenes necessary for reprogramming were embedded – synthesized proteins necessary for the return of fibroblasts to the embryonic state. After division, plasmids were randomly distributed among daughter cells, and some cells in the resulting population, while retaining all embryonic properties, turned out to be free of plasmids. These cells are practically indistinguishable from human embryonic stem cells and are capable of both unlimited growth in culture and differentiation into specialized cells of any type. It seems that regenerative medicine has tremendous prospects. Moreover, according to Thomson, with the current progress in the field of cell reprogramming, it is hoped that several methods for the safe production of induced pluripotent stem cells will soon be developed.
Portal "Eternal youth" www.vechnayamolodost.ru Based on ScienceDaily: Stem Cell Research: A New Way To Make Stem Cells Avoid Risk Of Cancer
30.03.2009