According to a team of researchers in the United States, under optimum conditions, any adult cell can be coaxed into becoming stem-cell like.
Led by Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, the researchers could speed up the process, cutting the time required for cells to become stem-cell like by around half.
AdvertisementThe results could help scientists working towards unraveling the complex biology of these cells, know as induced pluripotent stem (iPS) cells - which can develop into any other cell type.
Until now, the experimental conversion or 'reprogramming' of adult cells into iPS cells has been slow and inefficient, leaving some wondering whether only an elite subset of adult cells could make the switch.
Jaenisch and his colleagues developed a sophisticated system to study reprogramming, which involves using genetically identical mouse immune cells that contain additional copies of four genes required for reprogramming.
The genes include switches that allow them to be turned on by the addition of a drug.
In initial experiments, the researchers grew individual immune cells, switched on their reprogramming genes and allowed them to continue growing and dividing.
The team monitored how quickly the cells divided, and at what stage they began to produce a chemical signal that indicated they had become iPS cells.
Some of the cell populations began to signal after just two weeks. Others took longer - up to 18 weeks - but only 8 percent of the populations failed to generate iPS cells by this time.
"Essentially, all cells have the potential to become pluripotent," Nature quoted Jaenisch as saying.
The scientists thought that genes such as NANOG might have a role in accelerating some cells' path to pluripotency.
When the team increased expression of this gene, the rate of division in the immune cells did not change significantly, but the cells did require fewer cell divisions - and so less time - to become pluripotent.
In other experiments, the researchers were also able to cut the time required to generate iPS cells by increasing the expression of cancer-related genes, such as p53, which have recently been found to affect the efficiency with which adult cells can be reprogrammed.
Activating molecular pathways involved in cancer increased the rate at which the immune cells divided, and the rate of reprogramming increased in parallel: nearly all cell populations generated iPS cells within eight weeks.
Cells with and without cancer-gene modification produced iPS cells after the same number of cell divisions.
Jaenisch suspects that reprogramming involves a series of epigenetic events - whereby DNA is modified by chemical signals to control the rate of particular genes' expression - and that these mostly occur as cells are dividing.
Thus, it makes sense that when cells divide more quickly, as cancer cells do, they also become pluripotent more quickly, he said.
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