Posted on Jul 24, 2009, 10 a.m.
By gary clark
For the first time, scientists created "virtual genetic duplicates" of mice using skin cells from adult animals, which were manipulated into the equivalent of embryonic stem cells.
The use of human embryonic cells in research has generated tremendous controversy over the years, despite the widespread belief that human embryonic stem cell research could revolutionize medicine by allowing doctors to use genetically matched tissue to treat disease. In 2006, scientists made a major breakthrough, discovering that they could induce adult stem cells to regress to a stage in which the cells appeared to be identical to embryonic stem cells -- called induced pluripotent stem (iPS) cells. However, questions lingered as to whether those cells were truly equivalent.
To answer that question, Chinese researchers put iPS cells through the most rigorous test to date. They used viruses to “flip genetic switches” in the DNA of skin cells from adult mice in order to transform them into iPS cells. Some of those iPS cells were then injected into very early mice embryos that are capable of forming a placenta, but not of fully developing on their own. The researchers then transferred the resulting embryos into the wombs of surrogate mice.
Of the 37 iPS cell lines created, three produced 27 live offspring. One of those offspring, a 7-week-old male, impregnated a female, who had a baby of her own. Over time, the researchers bred approximately 100 first-generation mice and hundreds of second-generation mice that were almost identical from a genetic standpoint as the mice from which the iPS cells were originally derived. “This gives us hope for future therapeutic interventions using patients' own reprogrammed cells," Fanyi Zeng of Shanghai Jiao Tong University. And says Konrad Hochedlinger, a stem cell researcher at Harvard University, "This clearly says for the first time that iPS cells pass the most stringent test."
The research using mice bred from the iPS cells may open the door to an alternative to using human embryonic stem cells, a welcome advance by both supporters and opponents of human embryonic stem cell research. The scientists' work is considered a major step forward in demonstrating that iPS cells could be as useful as embryonic cells for studying and curing many illnesses. However, there are now concerns that the technique may fuel the cloning and genetic engineering of embryos. Those concerns could spark new calls for bans on attempts to clone humans and for restrictions on genetic manipulation of embryos. "The implications of this are both enormously important and troublesome," says Robert Lanza, a stem cell researcher at Advanced Cell Technology in Worcester, Mass. "It revives many of the issues raised by reproductive cloning."
News Release: Researchers may have found equivalent of embryonic stem cells www.washingtonpost.com July 24, 2009