FRIDAY, Aug. 24, 2001 (HealthDayNews) -- Revelations that the government-approved human stem cell lines have been mixed with mouse cells don't disturb federal overseers or at least one stem cell researcher.
The Washington Post reported today that many, if not all, of the now-growing colonies of embryonic stem cells were cultivated on beds of mouse tissue.
The U.S. Food and Drug Administration has strict rules regarding the use of animal tissue in humans. The technology, known as xenotransplantation, sparks fears in many experts that it could spread strange diseases.
President George Bush earlier this month said he would permit federal funding for experiments on about 60 stem cell lines derived from destroyed human embryos. Bush made no mention of the potential wrinkle involving mouse tissue.
However, a spokesman for the Department of Health and Human Services, which oversees federally financed scientific research and agencies including the FDA and the National Institutes of Health, dismisses the notion that contact with mouse cells would keep embryonic stem cell treatments from patients.
"This is no impediment to going forward with basic research, and we don't see any reason why this is an impediment to clinical research in the future," Bill Pierce says, adding that such studies on humans are at least three to five years off.
Brigid Hogan, a Vanderbilt University stem cell expert, also says the use of animal tissue to help grow embryonic stem cells isn't a problem for existing research, which is aimed chiefly at perfecting how to convince the primitive cells to become mature lines like muscle and nerves.
"For the purposes of what we need at the moment, I don't think it matters," says Hogan, whose research focuses on mouse, not human, stem cells. Ultimately, she says, once researchers have learned what it takes to make stem cells grow into various kinds of tissue, they can then turn their attention to growing them without the mouse tissue "lawn."
Embryonic stem cells can develop into virtually any tissue in the body and are touted as a potential treatment for everything from Parkinson's and Alzheimer's diseases to heart failure and spinal cord injuries.
Although scientists are trying to grow free-standing embryonic stem cells, most if not all of the existing colonies were seeded on layers of mouse embryonic "feeder" cells.
Experts say the animal tissue has been irradiated and treated with a drug to stop them from multiplying. But the tissue still produces some yet-unidentified chemicals, perhaps growth factors or other nutrients that encourage the human cells to thrive. The fear is that microbes like viruses may be harmless in the animal host but may sicken or kill a human who is passed them during a transplant.
The Washington Post report quoted a White House official involved in stem cell policy as saying the administration was aware that the cells would fall under the FDA's xenotransplant rules.
However, the White House considered the problem a minor one that scientists could solve by finding ways to avoid using the animal tissue or otherwise comply with FDA regulations, the official told the Post.
While xenotransplantation may fall under tighter regulatory supervision than conventional drug trials, it's not barred outright.
Diabetes researchers, for example, are testing pig pancreas cells to stimulate insulin production in people who don't make enough of the blood sugar hormone. Pig tissue transplants are also being used as a possible treatment for Parkinson's disease.
Earlier this year, the FDA proposed new regulations for xenotransplantation and gene therapy experiments. They include a controversial policy that would require scientists to post study design and patient safety information on the agency's Web site. That stipulation ruffled the biotechnology industry, which says such disclosure could compromise trade secrets and jeopardize patient privacy.
Bush today defended his decision to authorize limited funding of embryonic stem cell research in remarks from his ranch in Crawford, Texas.
"The NIH came into the Oval Office, and they looked me right in the eye and they said, 'We think there is ample stem-cell lines to determine whether or not this embryonic stem-cell research will work or not,''' Bush told reporters, according to a Reuters report.
What To Do
To learn more about stem cells, try the National Institutes of Health, or the U.S. Department of Health and Human Services. You can also visit the Coalition for the Advancement of Medical Research.
