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Induced pluriptoent stem cells used for therapy

A team from Rudy Jaenisch's lab at the Whitehead Institute reports this week in Science that it has used induced pluripotent stem cells to treat sickle cell anemia in mice. The researchers are touting the results as "proof of principle" that iPS cells can used for therapies, though they caution there's a lot of work to be done before iPS cells should be used in humans.

Here's what the Jaenisch team did:

+ Using mice that had been created with the human gene that causes sickle cell anemia, skin cells from the tail were reprogrammed to become pluripotent.

+ The now pluripotent cells were prompted to differentiate into cells that would become hemopoeitic (bone marrow) stem cells.

+ The researchers then took those cells and swapped out the gene for sickle cell anemia with the version of the gene that doesn't cause disease.

+ The bone marrow in the donor mice was killed off and the corrected hemopoetic cells were transplanted into the mice.

+ Tests of the mice indicated that the transplants were successful and the mice didn't exhibit signs of sickle cell anemia.

There are still a number of obstacles to using this approach in humans. The process used to create the iPS cells is known to increase the likelihood of the cells turning cancerous. Part of the problem is that one of the four genes used to induce pluripotency seems to play a role in cancer formation. The Jaenisch team tried to get around this issue by deleting that gene after they had reprogrammed the cells. But there's still the issue of how the four pluripotency-inducing genes are inserted in the first place. The current method uses retroviruses, which can introduce random errors into the DNA of the reprogrammed cell. The search is on to find ways around these problems. (Back in November Jaenisch told the Washington Post he didn't think the retrovirus issue was a big hurdle)

So where does this most recent iPS cell advance leave embryonic stem cell research? According to Jaenisch, ES cell research is still important. "We wouldn’t have known anything about IPS cells if we hadn’t worked with embryonic stem cells. For the foreseeable future, there will remain a continued need for embryonic stem cells as the crucial assessment tool for measuring the therapeutic potential of IPS cells," Jaenisch said in a Whitehead press release.

-Greg Dahlmann