MONDAY, June 3, 2002 (HealthDayNews) -- The Massachusetts company that created controversy last fall over its efforts to clone a human embryo has more big news.
They have used cloning to create heart "patches" and miniature kidneys, and then transplanted those back into the donor animals. In the process, they say, they have shown that therapeutic cloning can be performed without the fear of organ and tissue rejection.
"This is the first scientific study that shows cloned cells can be transplanted back into animals without being destroyed by the body's immune system," explains Dr. Robert Lanza, vice president of medical and scientific development at Advanced Cell Technology Inc. and lead author of the new study. The findings will appear as the cover story in the July issue of Nature Biotechnology.
"This was a study to investigate how the immune system would deal with cloned tissue in an animal model," Advanced Cell's Technology's President and Chief Executive Officer Michael D. West said in a statement.
The news is sure to rekindle the cloning debate, since the procedure involves discarding cow fetuses after the needed tissues are grown from them. Opponents of cloning will point to the discarded fetuses to buttress their position, experts say.
In a statement issued to coincide with the release of the report, the company's ethics advisory board points out that discarding animal fetuses is appropriate, but is never acceptable in human research. In addition, West said in a statement the technology should only be used to clone human embryonic stem cells, not an actual pregnancy.
Here's how the process worked in the latest experiment: Tissues were taken from adult cows and combined with an egg to create an embryo, which was then implanted inside a surrogate cow and left to develop for about six weeks. The scientists then took primitive stem cells from the embryos, and cultivated those in the lab to develop the heart "patches" and tiny kidneys. After that, they transplanted them back into the donor animals. At the same time, they transplanted uncloned tissues into the same animals to compare the results.
After three months, the cloned tissues all survived while the uncloned tissues did not, Lanza says. The cloned, miniature kidneys operated alongside the animal's original kidney. They excreted urea, the main component of urine, and otherwise acted normally. The heart "patches" also took hold and preserved their cardiac muscle.
Lanza explains they used a cow model for the experiment because the bovine has a much more sophisticated immune system than that of a mouse and is closer to the human immune system.
Besides the risk of rejection, Lanza says, the other hurdle in human transplant medicine is the organ shortage.
"Our results suggest it may be possible to overcome both these obstacles," he says.
Other experts in therapeutic cloning see pluses and minuses to the study.
The most important thing the researchers did was show that potential rejection of cloned tissue isn't much of a worry, says William Rideout, a postdoctoral associate at the Whitehead Institute for Biomedical Research at the Massachusetts Institute of Technology, where he works in the lab of cloning pioneer Dr. Rudolf Jaenisch.
However, in the current political climate, with federal bills pending that will decide the fate of cloning, it would have been better if the Massachusetts team had done the work in the lab rather than within animals, Rideout says.
"They did nuclear transfer, and implanted early embryos," Rideout says. "It would have been nice to differentiate the cells in a way that didn't destroy a fetus."
"Proponents will see the study as a plus," Rideout says. "They will say this proves rejection is not a problem." However, opponents will focus on the fact that the destruction of fetuses took place, he adds.
Already, a federal law prohibits the use of taxpayer money for human cloning, and three competing bills that address the issue are winding their way through the Senate. One would ban all cloning, while the others would outlaw human cloning but allow it for research into disease as long as the embryos were destroyed after a few days and never implanted in women.
Last fall, Advanced Cell Technology published a study in an online medical journal detailing its efforts to clone human embryos, and the news stirred up the national debate on the issue.
At that time, Lanza reiterated that the intention of the company is not to create cloned human beings but to generate lifesaving therapies that could help those with heart, kidney, lung, liver and other problems.
What To Do
For information on therapeutic cloning, go to Scientific American. For more information on the research, go to Advanced Cell Technology Inc.
