 |
 |
University of Wisconsin-Madison lab makes new kind of stem cells safer By DAVID WAHLBERG 608-252-6125 [log in to unmask] The UW-Madison scientists who created a new kind of stem cells two years ago have removed a major obstacle to using the cells to develop treatments: genetic mutations that could cause cancer. To make the cells - called induced pluripotent stem cells, or iPS cells - scientists put key genes into skin cells to reprogram the cells back to their embryonic states. They previously used viruses to deliver the genes, but that caused permanent changes in the cells that scientists feared could cause cancer and other problems. Now they have found a way to transfer the genes temporarily, using rings of DNA called plasmids. The result is safer iPS cells because the genes that cause the cells to revert to their embryonic state dissipate and cannot cause further genetic changes. . James Thomson's lab . UW-Madison stem-cell center . National Institute of General Medical Sciences . Science journal The iPS cells behave like embryonic stem cells but don't carry their ethical baggage because no embryos are used. Now iPS cells, apparently free of significant safety concerns, could be closer to being ready for use in cell transplants for diabetes, Parkinson's disease, heart disease and other conditions, though other hurdles remain. The new development, from the lab of campus stem-cell pioneer James Thomson, is reported in today's issue of the journal Science. It's "a major advance toward safely reprogramming cells for clinical use," Marion Zatz, a leader of the National Institute of General Medical Sciences, part of the National Institutes of Health, said in a statement. When viruses are used to make iPS cells, the reprogramming genes become a permanent part of the cells, causing mutations that can impair the function of the cells and possibly lead to cancer if the cells were used in treatments. When plasmids deliver the genes, they die off as the cells divide, the researchers said. That should remove the risk of cancer and other problems, they said. Problem fully solved Groups in Toronto and Boston recently announced other methods of making iPS cells more safely. But Thomson said his team is the first to fully solve the problem by getting rid of the viruses and the permanent genes. "This is a fairly big milestone," he said. "With this approach, the genes never integrate into the cells' genome. It's clean and safer." The Wisconsin Alumni Research Foundation, the university's tech-transfer arm, has applied for a patent on the new cells, he said. Thomson was the first scientist in the world to successfully grow human embryonic stem cells, in 1998. The process requires the destruction of days-old embryos, usually left over from fertility clinics. This month, President Barack Obama lifted Bush administration restrictions on the use of federal funding for research on the cells. In 2007, Thomson and his campus colleague Junying Yu co-discovered the original recipe for iPS cells, along with a competing team led by Japanese researcher Shinya Yamanaka. Thomson and Yu worked together again - along with Kejin Hu, Kim Smuga-Otto, Shulan Tian, Ron Stewart and Igor Slukvin - to develop the safer method for iPS cells. Seven key genes They relied on plasmids, the rings of DNA. They inserted seven key genes into the plasmids, which were then placed into cells from the foreskins of newborns. The genes caused the cells to revert to their embryonic state, from which they are thought capable of becoming any of the body's 220 cell types. Some of the new iPS cells have grown successfully for at least seven months. Unlike viruses, plasmids don't take root in the genetic structures of the cells, Thomson said. They last long enough to trigger the reprogramming but not long enough to cause cancer or other problems, he said. Several other safer methods of making iPS cells likely will be announced this year, as different scientists try different strategies, Thomson said. Researchers will analyze each kind and figure out which iPS cells are easiest to grow and most like embryonic stem cells, he said. Once the best approach is identified, Thomson said, scientists will have the same hurdles and hopes with iPS cells as with embryonic stem cells: figuring out how to grow them into heart, brain or pancreas cells and other cell types in a way that can repair or replace tissues damaged by disease without harming patients. Rayilyn Brown Director AZNPF Arizona Chapter National Parkinson Foundation [log in to unmask] ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn