London, Feb 28 : A small US biotech company has claimed that it has removed a major safety obstacle to using "reprogrammed" human stem cells, which pose a risk of turning cancerous.
PrimeGen, based in Irvine, California, claims that its scientists have converted specialised adult human cells back to a seemingly embryonic state, employing methods that are much less likely to trigger cancer than those deployed previously.
The company also says that it has been able to produce reprogrammed cells faster and much more efficiently than other scientists.
Presently, the newest area in stem cell biology is that of induced pluripotent stem cells, or iPS cells, which have the ability to develop into several different tissue types, first created by Shinya Yamanaka of Kyoto University in Japan.
Following the discovery, researchers in Japan and Wisconsin had reprogrammed skin cells to make primordial stem cells without destroying embryos.
However, little-noted in the news reports at the time was that to make these cells, the scientists needed to introduce cancer-causing genes into the cells using gene-altered viruses, thus making the resultant cells unsuitable for human therapy.
But now, PrimeGen has claimed that it had circumvented this problem.
Rather than using retroviruses to ferry the genes into the cells, PrimeGen used tiny carbon-based particles coated with DNA that codes for the same four reprogramming genes used by Yamanaka, including Oct3/4 and a fifth gene called Nanog.
The team then mixed the particles with human skin cells, kidney cells, or cells from the retina. The particles were quickly taken up by the adult cells, which were reprogrammed into an iPS cell-like state, says PrimeGen president John Sundsmo.
He added that coating the delivery particles with the proteins encoded by the five genes had the same effect.
Sundsmo said that colonies of iPS-like cells formed after about a week, contrasting Yamanaka's technique, which takes more than a month to form colonies of iPS cells.
Most remarkably, he claimed that PrimeGen's method is much more efficient, forming about 1000 times as many colonies of reprogrammed cells.
However, given previous claims in stem cell biology that have failed to stand up, other scientists are taking a cautious line.
"This is fascinating. But without more information, it's hard to know exactly how much they have done," New Scientist magazine quoted Arnold Kriegstein, head of developmental and stem cell biology at the University of California, San Francisco, as saying.
Sundsmo said that the company is writing up scientific papers on the method, and plans to release more details at a stem cell scientific meeting later this year.
He added that an independent lab has tested its cells and it has brought in top researchers to examine the results.