Cambridge team reports safer stem cell technique

The work appears on the heels of another report describing a different method also used to create a safer, virus- and gene-free version of such stem cells.

"The problem is if you leave the factors behind ... they could misbehave and could create cancer," said Andras Nagy, senior scientist at the Samuel Lunenfeld Research Institute in Toronto, who led the other work creating safer iPS cells published in Nature this week. "Everyone's trying to find a way to remove them after they do their job."

The technical advances are being unveiled at a timely moment, as researchers are anxiously waiting for President Obama to fulfill his promise to reverse restrictions on federal funding for embryonic stem cell research.

"We scientists are eager to see an executive order expanding federal funding for stem cells, since it would be a shame if the stimulus money ... couldn't be exploited for all of the exciting new opportunities in stem cell research," Dr. George Q. Daley, a prinicipal faculty member at the Harvard Stem Cell Institute, wrote in an e-mail.

Opponents have argued that iPS cells should replace research on controversial embryonic stem cells, but the new research actually found hints that the predominant way of making iPS cells today may not yield cells that are truly equivalent to the gold standard embryonic stem cells.

Jaenisch and colleagues compared the iPS cells they made using the new technique that removes the genes, with normal iPS cells in which they are still present in the cell. They also compared those cells with human embryonic stem cells. The results, Jaenisch said, were surprising.

The pattern of gene activity of the iPS cells created with the new technique was closest to that of the human embryonic stem cells. Gene activity was different in iPS cells that still harbored the genes.

"That is a warning sign," Jaenisch said. "For studying diseases, you might not get the right result because the biological properties might be affected."

Konrad Hochedlinger, a principal faculty member at the Harvard Stem Cell Institute not involved with the new study, said that the finding could help explain differences he has seen in his own research when using mouse embryonic stem cells and iPS cells to create heart muscle cells.

"What we still don’t really know is whether iPS cells ... are fully equivalent" to embryonic stem cells, Hochedlinger said. "We still need to compare them side by side, and figure out which cells are better and what are the differences."