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Genetic Piggybacking May Improve Transplants

Scientists sneak human genes into pig sperm

MONDAY, Oct. 21, 2002 (HealthDayNews) -- Italian researchers say they've discovered a new and improved way to inject human genes into pig sperm, raising hopes that it may become easier to breed pigs whose organs can be transplanted into people.

"This is definitely an advance," says Dr. Daniel Salomon, an expert in organ transplantation and a scientist at Scripps Research Institute in San Diego. "This technology frees us up and improves the whole process, making it easier and cheaper to do it."

Scientists think pigs, which are anatomically similar to humans, could provide an inexhaustible supply of body parts for people. However, human immune systems already have plenty of trouble adapting to body parts from other humans. Convincing a patient's immune system to accept a pig heart or liver is an even greater hurdle, and doctors think it may be years before pigs turn into organ donors instead of sausages.

For now, researchers are trying to figure out how to insert helpful human genes in pig sperm so the organs of the grown animals will get a better reception from the immune system of patients. Some researchers have tried injecting the genes into the pig sperm, but the approach doesn't always work.

Scientists at several Italian universities tried another approach. They grew pig sperm in a solution that contained a human gene that prevents the immune system from gearing up against foreign cells.

The findings of the study appear in tomorrow's issue of the Proceedings of the National Academy of Sciences.

Ninety-three piglets were born after the researchers tinkered with the pig sperm, and 57 percent of them contained the human gene, suggesting the sperm soaked it up from the solution. When researchers injected sperm with the gene, only 4 percent of the piglets born had the gene inside them.

Dr. Fritz Bach, director of the Immunobiology Research Center at Beth Israel Deaconess Medical Center in Boston, says the approach described by the Italian researchers would make it much easier to insert a number of human genes into pig sperm. One gene might not be enough, and scientists may learn more about which other ones are needed as they gain greater understanding of organ rejection, he says.

Salomon agrees. "Solving the problems of transplantation isn't going to be as easy as simply putting in one gene," he says.

Regardless, the approach will make it easier to test the insertion of a variety of genes into pigs. "If I need five different genes in a pig, I can make five pigs each with the right gene and then I can breed all five together and then pick the [piglets] that have all five," he explains.

The process will still take time, however. "It's still going to take a couple of years, and it's still going to be expensive," he says.

Despite the obstacles, it's possible that human bodies may someday be able to accept pig organs without being doomed to a life of immune-suppressing drugs, Bach says, "but I only foresee that in my very most optimistic moments."

What To Do

For more on xenotransplantation, check out the U.S. Food and Drug Administration or the U.K. Department of Health.

SOURCES: Daniel Salomon, M.D., physician scientist, Scripps Research Institute, San Diego; Fritz Bach, M.D., professor, surgery, Harvard Medical School, and director, Immunobiology Research Center, Beth Israel Deaconess Medical Center, Boston; Oct. 22, 2002, Proceedings of the National Academy of Sciences
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