The dream of doing in a lab dish what an egg cell does naturally began to come true in June, when [Shinya] Yamanaka’s team identified four genes in mouse skin cells that, when operating together, can turn countless other genes on and off in just the right pattern to transform skin cells so that they are almost indistinguishable from embryonic stem cells. He put copies of those four genes into retroviruses, Trojan horse-like viruses that insert their genetic payloads into the DNA of cells they infect. Once infected by the engineered viruses, the skin cells took on virtually all the characteristics embryonic ones.
Because the rejuvenated cells did not come from embryos and behave slightly differently than embryonic stem cells, Yamanaka named them “induced pluripotent stem cells,” or “ips” cells (pluripotent means “able to become virtually every kind of cell”).
He immediately tried the same technique on human skin cells, but failed repeatedly. What he did not realize, he said, was that the process takes weeks in human cells, compared to just days in mouse cells. After waiting several days for signs of colonies, he had been making the mistake of throwing his cultures out in frustration.
“We were not patient enough,” he said.
Ultimately, he found he could get about ten ips cell colonies from every 50,000 skin cells, an acceptable efficiency given how easy it is to grow thousands of skin cells from a tiny sample. He coaxed the ips cells to become nerve cells, beating heart cells and other major cell types. And he showed that they were exact genetic matches to the skin cells they came from, suggesting that tissues or organs grown from them could be transplanted into the person who donated the skin cells and not be rejected.
James Thomson, the American scientist who first isolated embryonic stem cells in 1998, was working concurrently with (and independent of) Yamanaka on the same task and got the same result — although two of the four skin-cell genes he used were different from Yamanaka’s, suggesting there may be various combinations that can do the job. There’s a minor problem left to solve insofar as retroviruses, the delivery mechanism for the transformative genes, apparently can cause cancer, but they don’t think that’ll be a tough nut to crack. Quoth a spokesman from the U.S. Conference of Catholic Bishops, which has already been briefed on the findings: “All the Catholic scientists and ethicists at the conference … had no moral problem with it at all.”
Next stop: Artificial selection!
Update: Jonah Goldberg makes a point I’m seeing in the comments here too.
What I find fascinating about this — indeed, what I find fascinating about the role of technology generally (I’ve long wanted to write a big think piece on this) — is how necessity is not only the mother of invention, it’s the father of immorality.
Because President Bush wisely placed limitations on one scientific path, scientists needed to come up with another route to the same goal. It now sounds like they found it. Huzzahs to everyone (Memo to the Communications Director: Bush should give a speech on this taking his share of the credit).
It assumes too much to think there are no ethical scientists who wouldn’t have explored this avenue on their own without Bush’s decision to limit funding. But that decision surely accelerated the process.
Anyone know how long, precisely, they’ve been working in this vein? The Times’s report refers to the work as “laborious” but I can’t find any dates in either their story or WaPo’s.