What Is Xenotransplantation?

Xenotransplantation is the transplanting of animal tissues and organs into a human, and is being studied as a substitute for human organ donors.

Xenotransplantation is the transplanting of animal tissues and organs into a human, and is being studied as a substitute for human organ donors. Today the study and experimentation revolving around the subject of genetics is exciting and frightening at the same time. The fact that an estimated 10 people die every day because an organ is not available has researchers experimenting with various options - like injecting a pig heart with human genes to try to make it "invisible" to the human immune system - to try to trick the system into thinking the new pig heart belongs. In the future the recipient of a porcine part may also be able to get a blood transfusion from the pig. Scientists have already successfully cloned Xena, the piglet - named because of the hope she offers to the future of xenotransplantation. She and "Dolly" the cloned Finn Dorset sheep, are the first members of the new "cloned barnyard."

For scientists, the development of animal donors is exciting new territory. In human-to-human transplantation the person receiving the organ must be treated with powerful anti-rejection (immune-suppressing) drugs that can be devastating to their immune system. If an animal heart was available that had been genetically altered with a human gene, the possibility exists that the need for the anti-rejection drugs would be eliminated or reduced.

But everybody isn't jumping on the xenotransplantation bandwagon. There are many complicated issues involved and the "Campaign For Responsible Transplantation" addresses many of them.

Humans are built with natural barriers to certain diseases. Examples are the skin and the gastrointestinal tract. When these barriers are bypassed (via transplantation) the transmission of infectious disease is facilitated. Disease that might not have any effect on a pig, could kill a human being. The Macaque herpes virus is harmless to Macaque monkeys, but lethal to humans. If there is an animal virus residing in a xenograft recipient, their sneeze could broadcast a deadly new virus, infecting many people and possibly cause an epidemic worse than HIV, worldwide.

Scientists have targeted pigs to use for replacement parts for humans, due to the similarity in size of the organs and because they are easy to breed, having large litters of piglets instead of single offspring. There are over 25 diseases in pigs that are dangerous to humans and to date no way to screen to see if the viruses exist. In 1918 an influenza virus that resembled a common swine flu was responsible for killing more people than any other epidemic including AIDS and the Black Plague.

Recently, the "Nipah" virus, discovered in Malaysia in late 1998, spread from pigs to hundreds of humans, killing 100+ and leading to the mass slaughter of some one million pigs, as well as several dogs and horses. Humans that come into contact with living pig tissue could be the living incubator for the next great human plague. Some of the most deadly diseases in recent history are ones that have jumped from one species to another - i.e. HIV, influenza, "mad cow" disease and Ebola.

Xenotransplantation can really be seen as human experimentation. There is no way to know if diseases and viruses could lay dormant in the transplanted organ, until years later. Pig viruses related to the ones that can cause leukemia and other diseases can infect and multiply in human cells.

Alix Fano, the director of the "Campaign for Responsible Transplantation" believes that we may be opening a Pandora's box of problems that may cause great risk to human health. "By cloning pigs, you're not going to eliminate the threat of viruses being transferred to humans," says Fano. For instance, she says, porcine endogenous retrovirus "is present throughout the pig genome, in every single organ of the pig and will never be bred out." ¹

While scientists do what scientists do - experiment and move forward with safe alternatives - what can be done to help close the gap between people who need donor organs and the organs that could save their lives?

1.Become an organ donor and encourage others to fill out an organ donor card. Be sure your family knows that you desire to be an organ donor because they will have to sign a consent form.

The following can be donated:

Organs: heart, kidneys, pancreas, lungs, liver, and intestines.

Tissue: cornea, skin, bone marrow, heart valves, and connective tissue.

2. Researchers and policy makers should examine options like split-liver transplants, single kidney donations from living donors, expanding donor criteria and developing science in the area of regenerating the human organs.

3. Another option involves a presumed consent law, common in European countries, which means that unless patients specifically refuse to donate their organs upon their death, hospitals can assume that patients give consent. ¹

As technology moves forward so do issues of ethics and safety. We are entering territory that could advance the quality of human life, or wipe it out!

1.Move Over Dolly, by Nicolle Charbonneau, HealthScout Reporter from HealthScout.com

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