Gleaning stem cells from cloned monkey embryos, as a team of Oregon researchers has done, is an impressive step. But it probably won't lead to medical treatments anytime soon.
One hurdle is ethical and political: Human embryos have to be destroyed to produce stem cells.
That has aroused opposition to human embryonic-stem-cell research, and it led the Bush administration to restrict federal funding for it. Scientists say that has slowed science in this effort.
Another hurdle is the inefficiency of the process. Even if the method described by scientists online Wednesday in the scientific journal Nature works in humans, it would demand too much of a resource — women's unfertilized eggs.
A team led by Shoukhrat Mitalipov of the Oregon National Primate Research Center in Portland, merged skin cells of a rhesus macaque male with unfertilized monkey eggs that had the DNA removed.
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The eggs, now operating with DNA from the skin cells, grew into early embryos in the laboratory. Stem cells were recovered from these embryos.
The promise of producing stem cells by cloning is that they can be genetically matched to a particular patient. The process used in the new experiment is "quite inefficient," Mitalipov told reporters Wednesday.
He and his colleagues reported getting two batches of stem cells that required using about 150 monkey eggs apiece.
That's far too many if one hopes to use human unfertilized eggs, which are cumbersome to obtain from women.
If further work can get that down to maybe five to 10 eggs per stem-cell batch, "we will be closer to clinical applications," Mitalipov said.
