IPSC from somatic cells with an efficiency of 100%
The efficiency of stem cell production can be increased up to 100 percent
NanoNewsNet based on materials from NYU Langone Medical Center:
NYU Langone Scientists Report Reliable and Highly Efficient Method for Making Stem CellsScientists at the Langon Medical Center of New York University have found a way to significantly increase the efficiency of the process of reprogramming somatic cells into so-called induced pluripotent stem cells by applying a combination of three well-known compounds, including vitamin C. Using a new technique on mouse cells, the researchers increased the number of stem cells obtained from skin cells by more than 20 times compared to the standard method.
Considering their technique effective and reliable, they hope that it will give a new impetus to research aimed at using stem cells to grow various types of biological tissue.
"A significant increase in efficiency gives us the opportunity to study the mechanisms of stem cell programming at a deeper level," says study leader Matthias Stadtfeld, PhD, associate professor of Cell Biology and researcher at the Skirball Institute of Biomolecular Medicine and the Kimmel Center for Stem Cell Biology (Helen L. and Martin S. Kimmel Center for Stem Cell Biology) of the Langon Medical Center of New York University.
The world learned about the possibility of reprogramming skin cells, blood cells or other tissue-specific cells into so-called induced pluripotent stem cells (iPSCs) in 2006. This was achieved by the Japanese scientist Shinya Yamanaka from Kyoto University, who later received the Nobel Prize for his achievement. Yamanaka's method is based on the artificial expression of four key genes (Oct4, Klf4, Sox2 and Myc), collectively called OKSM. The joint activity of this quartet slowly pushes the cells to an immature state, close to the state of the cells of the early embryo.
Theoretically, it is possible to take cells of a specific person, reprogram them into iPSCs, multiply iPSCs in the laboratory and induce their transformation into the desired type of cells, for example, into blood, brain or heart cells. Such cells can be used to restore injured or diseased tissues of the same person.
But in practice, scientists face many serious technical obstacles, including the low efficiency of the protocols currently used. In stable iPSCs, 1 percent or less of most cell types are reprogrammed, and this process can take several weeks.
Laboratories around the world are looking for ways to improve the efficiency of reprogramming, and in some cases they manage to achieve significant success. However, these procedures often affect vital genes, which makes therapies based on such cells far from safe. Dr. Stadtfeld and his lab decided to take a less invasive approach and study chemical compounds that temporarily modulate enzymes present in most cells.
"We especially wanted to find out if it is possible to combine these compounds to increase the efficiency of stem cell production," comments Dr. Stadtfeld.
Two of these compounds affect known signaling pathways – Wnt and TGF-beta – that regulate many processes related to cell growth. The third is vitamin C, or ascorbic acid. Best known as a powerful antioxidant, vitamin C has recently been found to aid in the induction of iPSCs by activating enzymes that remodel chromatin – the helical framework of DNA – thereby affecting gene expression.
Simon Vidal, a graduate student at Stadtfeld, and postdoctoral fellow Bhishma Amlani began experiments with mouse skin fibroblasts, the most common type of cell used to study iPSCs. The addition of either vitamin C to genetically modified fibroblasts expressing OKSM, or a compound activating Wnt signaling, or a compound inhibiting TGF-beta signaling, increased the efficiency of obtaining iPSCs to about 1 percent per week of cell culture. Adding any two of these compounds gave a better result. But the combination of all three increased efficiency by up to 80 percent over the same time period.
In another series of experiments, the researchers worked with blood progenitor cells. The OKSM gene cocktail, taken in its pure form, can slowly convert these cells into stem cells with an efficiency of up to 30 percent. Using OKSM together with three compounds raised the efficiency to almost 100 percent in less than a week. Almost 100% efficiency was also achieved in experiments with mouse liver progenitor cells.
Colony of induced pluripotent stem cells,
obtained using a new technique from a single mature immune cell
Dr. Stadtfeld believes that a sharp increase in the degree of conversion of somatic cells into stem cells with the properties of embryonic cells will facilitate the future study of the IPSC induction process primarily due to the fact that the induction process has become more predictable.
"It's just so much easier to study the mechanisms that control reprogramming. It is easier to identify any undesirable properties that iPSCs can acquire," the scientist explains.
Vitamin C and two compounds used to manipulate the Wnt and TGF-beta pathways have been well studied and, according to researchers, may not have many unknown or dangerous effects. On the contrary, the use of OKSM in some cases is the cause of undesirable properties of iPSCs, leading, for example, to malformations. As for Dr. Stadtfeld's new technique, by making the receipt of iPSCs faster and more effective, it also increases their safety.
"Presumably, it reduces the risk of developing anomalies by smoothing the reprogramming process," says Dr. Stadtfeld. "This is one of those issues that we keep under control."
"This is a very significant achievement," says Ruth Lehmann, PhD, director of the Kimmel Center and the Skirball Institute, head of the Department of Cell Biology. "The new technique of effective reprogramming of differentiated cells developed in the Stadtfeld laboratory brings us closer than ever before to the methods of their safe use in regenerative medicine."
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