UNITED STATES:SCIENTISTS ARE reporting that they have overcome a major obstacle to using a promising alternative to embryonic stem cells, bolstering the prospects for bypassing the political and ethical tempest that has embroiled hopes for a new generation of medical treatments.
The researchers said they found a safe way to coax adult cells to regress into an embryonic state, alleviating what had been the most worrisome uncertainty about developing the cells into potential cures.
"We have removed a major roadblock for translating this into a clinical setting," said Konrad Hochedlinger, a Harvard University stem-cell researcher whose research was published online yesterday by the journal Science. "I think it's an important advance."
The development is the latest in the rapidly-advancing and politically-charged field of stem-cell research.
Embryonic stem cells are believed capable of becoming any type of cell in the body. Researchers hope eventually to use them to create replacement tissue and body parts tailored to individual patients. But the work has been mired in controversy because the cells were obtained by destroying very early embryos.
Scientists last year shook up the scientific and political landscape by discovering how to manipulate the genes of adult cells to revert them into the equivalent of embryonic cells - entities dubbed "induced pluripotent stem" or iPS cells - which could then be transformed into any type of cell in the body.
Subsequent work has found that the cells can alleviate symptoms of Parkinson's disease and sickle-cell anemia in mice.
But the first iPS cells were created by ferrying four genes into the DNA of adult cells using retroviruses, which can cause cancer in animals.
There was also concern because the viruses integrated their genes into the cells' DNA in the course of transforming them. In the new work, Hochedlinger and his colleagues used a different type of virus, known as an adenovirus, which does not integrate its genes into a cell's DNA and therefore is believed to be harmless.
"The adenovirus will infect the cells but then will clear themselves from the cells. After a few cell divisions there are no traces of the virus in the cell," he said. Like iPS cells produced using retroviruses, tests showed that the cells were indistinguishable from embryonic stem cells and could be transformed into any type of tissue, including lung, brain, heart and muscle, without producing cancerous tumours.
Rudolf Jaenisch, a professor of biology at the Whitehead Institute in Cambridge, Massachusetts, praised the work, but noted that the process was 100 times less efficient than using retroviruses.
Hochedlinger said his team is already working to streamline the conversion. Many researchers suspect they will eventually find ways to transform cells much more cleanly without transferring genes.
Although additional work will be necessary to prove the approach will work with human cells, Hochedlinger said he was confident it will.
- (LA Times-Washington Post service)