Induction of Pluripotent Stem Cells from Mouse Embryonic and Adult Fibroblast Cultures by Defined Factors
Kazutoshi Takahashi and Shinya Yamanaka
Department of Stem Cell Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
This research is about reprogramming the nuclear content of fibroblast cells to pluripotent stem cells. Since we all know the importance of pluripotent stem cells, they can growth and differentiate to all the three germs layers of tissues. However, collecting contamination-free pluripotent stem cells in a significant amount that are suitable for therapeutic use is problematic. This paper provided a possible solution about the source of pluripotent stem cells. As all cells in a single human body share the same DNA sequence, the only difference between cell types is that some genes are inhibited and some of them are enhanced. In this research, the Japanese scientists reprogrammed the nuclear content of the fibroblast cell by introducing four factors Oct3/4, Sox2, c-Myc, and Klf4; at the end they found that the modified fibroblast cells expressed some similar characteristics as pluripotent stem cell.
At first they started with 24 candidate genes, they modified the 24 genes of the fibroblasts and compared their morphology and resistance to G418 with pluripotent stem cells. Afterward, they narrowed to 10 genes and created colonies of modified cells with the combination of the 10 genes. They sorted out the colonies by their similarity with ES cell on G418-resistant, morphology, proliferation properties and RT-PCR analysis of ES cell markers; at last, the combination of Oct3/4, Sox2, c-Myc, and Klf4 is reported to have the closest characteristic with pluripotent stem cell. This “winning” combination of cells is called induced pluripotent stem (iPS).
Furthermore, additional tests were preformed on the iPS. They studied the iPS’s global gene-expression by DNA microarrays with pluripotent stem cell and found that their gene expression is similar, but not identical. Since they are not identical, this also confirmed that the result is not due to contamination of the modified fibroblasts cell colony by the pluripotent stem cell. At last, they transplanted the modified fibroblasts cells to a living mouse and caused a teratoma which contains all three germ layers as same as the pluripotent stem cell.
5 comments:
It's nice that fibroblasts now can be engineered into pluripotent stem cells. Do you know about the future study of this finding? I was thinking that this finding is still an early stage to applying it for benefits. It will be a good thing to have it from human so that the fibroblasts can be an alternative, less controversial source of pluripotent stem cells.
It has been suggested that some progenitor cells can be re- mis-programmed to become cancerous. Is there any mention of this phenomenon in this paper? If not, which would you think would have a greater effect: environmental factors or just the reprogram of the genomic content?
What are some applications of the induced pluripotent stem cells besides causing teratomas? Could they be used in medicine/as some sort of therapy?
As I mentioned in other comments, I believe stem cells offer a better way to construct a artificial Tissue. I like this direction: Yes, the current the biggest problem is control! Personally I don't see we can understand the principles such as why cell will respond to certain factors so the best way for now is trial and error. This should be the first step for a big discovery.
Is this "difference between cell types that some genes are inhibited and some of them are enhanced" the basis for pluripotent cells and their incapability to form into complete organisms?
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