In the 1960s, surgeons experimented by transplanting chimpanzee organs into humans in need of an organ transplant. In 1985, Baby Fae received a baboon heart and survived 20 days. Since then, doctors have continued to look to animals as a source for organs, tissues and cells to treat various diseases, all with varying degrees of success. Here's a look at the controversy surrounding cross-species transplant -- also known as xenotransplantation.
Dick Beyer has Parkinson's. "I move in slow motion," he says. Betsy Ray has diabetes. "I've got retinopathy in my eyes," she says. "I have cataracts." George Jones has kidney failure "I guess if it wasn't for dialysis, I wouldn't be here." Some doctors predict pigs will cure them.
"The holy grail of all this is a pig whose organs are not recognized as pig organs but rather are seen essentially to have tissues that our immune system thinks is human tissue," says Marlon Levy, a transplant surgeon at Baylor All Saints Medical Center in Fort Worth, Texas.
Five years ago, Dr. Levy used pig livers to do the job two patients' livers could not. "The ending of this story is that both of these patients are doing remarkably well today," he says.
It has been know that since the early 1990s about 16 people have died in human xenotransplantation trials. There have been patients in Parkinson's disease trials who have had pig cells injected into their brains who have come down with malignant cancers," says Fano, who is Executive Director of the Campaign for Responsible Transplantation in New York.
But no research has been done to show a link, and scientists are expanding their research. Pig cells are now being studied for strokes, epilepsy and Huntington's disease. And doctors from Mexico recently transplanted pig islet cells into 12 diabetic children. Doctors say one is off insulin and the others reduced their insulin requirement by more than 60 percent.
"We do know that patients who have been exposed to pig cells and tissues do have pig DNA circulating in their blood," says Fano, "And that means they most certainly have pig viruses in their blood as well." It's these viruses that concern her most. "We're talking about putting the entire population at risk from a pig virus that could mutate and spread and kill lots of other people."
Biotech companies are working to eliminate that. They're breeding pigs they say do not pass on the PERV virus --the one deemed most dangerous to humans.
While it may be too early for species to share organs, researchers continue their work -- hoping to give patients a second chance at life.
However lack of funding remains the main reason the research is going so slowly.
Researchers also say cloned pigs may play an important role in xenotransplantation and this is even more controversial.