26 September 2008

A New Age for Stem Cells and Regeneration

A new way of inducing the creation of pluripotent stem cells (iPS) from mature cells is opening the way for a positive deluge of new stem cell research--unrestricted by government funding limitations, access to embryos, or danger of cancerous transformation. Regenerative medicine has never been as promising as it is right now.
Many view the creation of genetically unmodified iPS cells as regenerative medicine's magic bullet. The cells are not derived from embryos, so researchers can circumnavigate the ethical gray areas. And if these cells turn out to be as potent as embryonic stem cells, they could be used to help regrow tissues damaged in conditions ranging from paralysis to Parkinson's disease to diabetes. If they can be grown from a patient's own cells, they could furthermore be transplanted without triggering immune rejection.

...The efficiency, as described in latest edition of the journal Science, is still incredibly low. Out of 1 million adenovirus-infected cells, the researchers ultimately produced just one stable line of stem cells. But the line was genetically unaltered, and when the cells were implanted in mice, they formed a cluster of cells that had differentiated into multiple tissue types (a standard test for pluripotency). When the researchers injected the cells into mouse embryos, the resulting mice had integrated the stem cells into a number of different types of tissue, including tissue in the brain, lungs, and heart. And mice as old as 13 weeks remained tumor-free.

Until now, iPS cells couldn't be compared to embryonic stem cells, since the effects of the integrated virus were unknown. "It was like comparing apples and oranges," Hochedlinger says. Now, however, the potency of the two cell types can be evaluated head to head. "You can really think about doing this in a human setting now, and about making genetically unmodified human cells for modeling or even for therapy."

The finding already has other stem-cell experts thinking about the possibilities. "The paper represents a major breakthrough in reprogramming research and proves to the field that we can reprogram cells directly without viral contamination," says George Daley, a Harvard biologist and stem-cell researcher who was not involved with the research. "It is a major step towards making clinical transplantation of patient-specific cells feasible."

Hochedlinger and his colleagues are now working to increase the efficiency of their adenovirus technique and to repeat their methods to create human iPS cells. "Once we do that," Hochedlinger says, "we can figure out whether [embryonic stem] cells and unmodified iPS cells are really identical to each other or not. I don't know the answer yet." _TechReview
Once the efficiencies of the process are improved, availability of patient-specific pluripotent stem cells should skyrocket, and ethical and technical obstacles to clinical use of stem cells should steadily melt away.


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