 |
 |
Hi All, Read the whole article.... Not much promise in store for Parkinson's yet IMHO.... murray Pigs show promise as source for lifesaving transplants Jay Bookman - Staff Sunday, March 18, 2001 An estimated 6,000 people die each year in this country waiting for an organ transplant that never comes. Their salvation --- and the salvation of thousands of others suffering from Parkinson's, Alzheimer's and strokes --- may come from pigs. At least a half-dozen companies around the world are experimenting with ways to harvest hearts, kidneys, brain and liver cells and other living tissue from pigs for transplanting into human patients. The cross-species surgery, called xenotransplantation, is controversial in some quarters because of its experimental nature, its potential for spreading new forms of disease and because, well, we're taking pig parts to use in people. But many surgeons --- and patients --- see it as the potential answer to their prayers. The need for transplant organs is immense. For the first time in history, more than 75,000 people are now on the organ transplant waiting list, according to the United Network for Organ Sharing. In 1990, that number was barely 20,000. There are more than 1,000 on the waiting list in Georgia alone, according to Jeff Al-Mashat of Lifelink of Georgia. "I'm very much in favor of (xenotransplants)," says Dr. Mark Deierhoi, head of the Division of Transplantation Surgery at the University of Alabama-Birmingham, one of the two largest transplant centers in the country. "It's terribly tragic to see patients die that we could be helping if we could just order up the organs they needed." Deierhoi has performed 1,400 kidney transplants, sometimes on patients who have waited as long as five years for a new organ. "It's rough on them," he says. "It's not unusual to call someone after five or six years and have them tell you they never thought the call would come." And for some, especially heart transplant patients, that call never does come. While kidney transplant candidates can turn to dialysis to keep them alive until an organ becomes available, heart transplant patients don't have that option. As Deierhoi points out, if they don't get an organ in time, they face death. For more than 25 years now, surgeons have been using pig valves to patch up faulty human hearts, so the idea itself isn't new. However, the pig tissue in those transplants is dead and has been specially treated. It's just a piece of material, like plastic or steel, and is not a living part of the body. With xenotransplantation, however, the organ is living tissue. The biggest obstacle to xenotransplantation is rejection by the patient's immune system. That's a problem even in human-to-human transplants, but it's particularly difficult with two different species. Without some form of protection, the human immune system would destroy transplanted pig organs, quickly reducing them to a black ooze. Nextran, a company based in Princeton, N.J., hopes to solve the rejection problem by harvesting organs from specially engineered pigs. Other companies take a similar approach. Nextran's process begins by injecting human DNA into pig embryos specially bred for xenotransplantation. When the pigs are grown, their organs "look like human organs to the human immune system," says Deborah Spak, a spokesman for Nextran. Early signs are promising. Nextran pig livers have already been used to "bridge" several critically ill patients awaiting transplants of human livers. The patients were hooked up to the pig livers outside their bodies for several hours, and according to Spak the livers functioned well. "It was a good way to gain some basic knowledge, and it also kept some of those patients alive until human organs became available," Spak says. Three bridge patients lived long enough to receive transplants. Two were too critically ill to survive. Nextran will apply to the Food and Drug Administration sometime next year for permission to conduct human trials on heart or kidney transplants, Spak says. "But given this subject matter, we have no clue how long it would take to get a go-ahead (from the FDA). The standard doesn't apply in a case like this, and we understand that." While xenotransplantation of whole organs is at least several years away, other companies are already implanting other types of pig tissue into human patients. Researchers at Diacrin, based in Boston, have injected specially engineered brain cells from fetal pigs into the brains of human beings as treatment for Parkinson's disease, strokes and epilepsy. The cells are equipped with special antibodies designed to disarm the human immune system. The company is also developing pig cells to treat acute liver failure and macular degeneration, an eye disease that typically ends in blindness. Diacrin is still in the early phases of human trials for treating strokes and epilepsy, However, its approach may not work for Parkinson's. A clinical trial that ended Friday found no discernible improvement in patients who received the cell transplant. Eighteen patients were enrolled in the study: Ten received the treatment, while the remaining eight were given sham surgery and were used as a control group. Doctors injected 24 million fetal pig brain cells into each half of the brain of patients in advanced stages of Parkinson's. In all of the test patients, the disease had progressed far enough that the usual drugs and medicines were no longer effective. Had the treatment worked, the control group members would have been offered the surgery immediately. Cross-species transplantation also creates another serious risk. By transplanting living pig tissue into human bodies, it is possible to transplant pig diseases as well. HIV, the virus that causes AIDS, is believed to have been transferred to humans from monkeys. As the course of AIDS indicates, diseases transferred from animals can be disastrous for new victims who lack the evolutionary defenses of the original hosts. With pigs, the main fear is porcine endogenous retrovirus, or PERV. So far, none of the patients involved in Diacrin's clinical trials has shown any sign of PERV, says Dr. Thomas Fraser, CEO of Diacrin. Nor has it shown up in research conducted by other companies. Nonetheless, the possibility has made the FDA understandably cautious. "I wouldn't say we're ever going to eliminate that hurdle," Fraser says. "Even with a low-probability event, you can't guarantee it would never happen, especially as this kind of treatment expands in numbers. But even if it happens, I don't believe that particular retrovirus is going to be all that dangerous." Many diseases can be transmitted between species. In 1998-99, more than 100 people were killed in Malaysia by a previously unknown virus, called Nipah, that was transmitted from pigs to pig farmers. And some of the most dangerous forms of influenza originate in pigs. As Fraser points out, however, human-to-human transplants have also been shown to spread disease. Most scientists believe that while it's a problem to be monitored, it's not dire enough to halt research. The stakes in the business are certainly high. For Diacrin, Nextran and other companies, clinical success and FDA approval would turn xenotransplantation into a multibillion-dollar business. And it would turn their pigs into the most lucrative "pharm animals" on the planet. http://www.accessatlanta.com/partners/ajc/epaper/editions/today/news_a34bc59063c1123a007b.html ********* ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn