A Comprehensive Examination Of Xenotransplants

  • Category: Science
  • Words: 1912
  • Grade: 88
Xenotransplant -zEE'nO'trans'plant
The surgical removal of an organ or tissue from one species and transplanting it into a member of a different species, for example: the use of a baboon heart in a human being.

        Over the past several years the topic of xenotransplantation has continued to be in the scientific and media spotlight, and with just cause. The thought of using parts from other creatures in a human sounds like something out of a horror film and one would probably no doubt be burned at the stake for even suggesting the idea at one point in time. However, with all of the medical advances in today's society, (cloning, the human genome project and modifying other organisms to our own specifications), does a xenograft really seem that far fetched? The History, societal concerns, animal rights, environmental issues, regulatory matters and reasons for xenotransplants will all be looked at in this essay.

A Brief History

        Xenotransplantation was practiced as early as the 17th century but was not seriously pursued until the early 20th century, with grafts from rabbits, pigs, goats, lambs and non-human primates. The 1960's were a prominent year for xenotransplants and its research. Keith Reemtsma, a professor of surgery at Tulane University, paved the way with 13 chimpanzee-to-human kidney transplants. Tragically all but one recipient died within days, the last died 9 months later.



Time Line of Xenotransplantation in History


        1682-Animal tissues were transplanted into a human for the first time using a canine skull fragment         
        to repair the skull of an injured Russian nobleman.

        
        Late 1800's- Frog's skin was often grafted onto human burn victims.

        
        1920-Serge Voronoff, an émérége doctor began transplanting tissues from the testicles of         

        monkeys         into elderly men. He claimed this instilled a new sexual vigour in the patients.

        
        1977-Christian Bernard (left) tried to use a baboon and chimpanzee heart as a temporary tack-up         pumps in two patients. It was unsuccessful as the hearts were too small for the patients and         

        rejected.

        
        1984-Baby Fae (left), born prematurely with a malformed heart, received a heart from a baboon.         

        The infant only survived 20 days after surgery.

        
        1992-Live transplants from baboons to humans conducted at the University of Pittsburgh.

        
        1997- Clinical trial using pig fetal nerve cells in patients with Parkinson's disease indicated some         

        success.


                                                                                        



Public Health Risks
        
        Risks posed by xenotransplants to the general publics health is a serious concern. There are many different ways viruses spread for host to recipient, a virus residing in a xenograft patient could become air born and infect scores of people or the virus may be completely harmless and go unnoticed in human. This is a risk that is taken when one deals with xenotransplants. It is definitely an unacceptable risk. Although donor organs can be screened for virus's one must remember the screening is only checking for disease that we know about, there may very well be an infinite number of unknown diseases and viruses not yet known to us. Proceeding with a xenotransplant could expose both patients and non-patients to a host of new animal viruses. Even if the above mentioned concern was no longer an issue (i.e. We knew of all potential hazards and could screen for them) one must consider that many animal viruses have the ability to jump species barriers and kill humans. Meaning, viruses that are harmless to their animal host, can be deadly when transmitted to humans. For example, Macaque herpes is harmless to Macaque monkeys, but lethal to humans. Lastly, concerning genetically altered pigs who carry human genes, pro-xeno researchers claim they will breed "germ-free" pigs thereby diminishing the risk of viral transmission. This theory can easily be blown out of the water as no animal can remain completely free of parasites or endogenous viruses. Ironically, theses genetically modified animals would be more susceptible to illness because they would
                                                                                        

posses a compromised immune system.
        

        Safest End Of Transplant Spectrum        Midrange Of Transplant Spectrum        Riskiest End Of Transplant Spectrum Disease Treated        Diabetes        Kidney Failure        Heart Failure Organ Transplanted        Pancreatic Islets        Kidney        Heart Donor Animal        Pig        Transgenic Pig        Baboon Immunosupression        None (Immunobarriers)        Systematic (lifelong)        Systematic (lifelong) Graft Failure        Return to insulin injections        Dialysis        Death

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        Rejection of the transplanted organ is also a major concern for doctors and patients alike. The data listed on the following chart details the organ, donor animal, no. of cases, year the procedure was performed and the outcome for the patient (namely how long they survived for) after the surgery.

Experience in Clinical Xenografting
Donor        Organ        Outcome        No. Cases        Year Chimpanzee        Kidney        < 9 months        12        1964 Monkey        Kidney        10 days        1        1964 Baboon        Kidney        4 ½ days        1        1964 Chimpanzee        Heart         Insufficient cardiac out put        1        1964 Baboon        Heart         Acute rejection        1        1977 Chimpanzee        Liver         < 14 days        1        1977 Baboon        Heart        4 weeks        1        1985 ("baby Fae")


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Economic Concerns
        
        In today's money worshiping society effective technology is hailed. Unfortunately, xenotransplantation is in no way cost effective. It is riskier and more expensive than human-to-human transplants (approximately $300,000/operation for a xenotransplant not including the hidden costs of breeding, housing, feeding, medicating, testing, transporting, rendering and disposing of transgenic animal waste). These costs are for regular animals, the transgenic animal waste disposal cost only applies to "germ-free" animals ,(not the germ-free mentioned in the above paragraph. These animals still have the potential for infection, they simply live in "clean" conditions), which can cost an extra $25,000-$100,000 due to the maintenance of the "clean" environment they live in.

Animal Rights
        
        Considering that pigs are used in xenografts because they are so closely linked to humans anatomically a valid question to ask would be does the pig know/feel what is happening to it. Most people would say no and justify it by the fact that pigs live in, shall we say, less than desirable conditions. Scientific studies conducted on pigs beg to differ however. The studies have demonstrated that pigs are not only highly intelligent but emotionally sensitive animals. "Pigs used at the University of Pennsylvania manipulated joysticks with their mouths to solve mazes and play games on a computer." (Animal Welfare Concerns, www.crt-online.org).
        Many area's of the U.S have stated that it is "ethical" to use pigs for xenotransplant research as they are killed for food. This is an incredibly ironic statement as it is the consumption of large amounts of pork (and other animal fats) , along with an inactive lifestyle that has caused the need for this type of research. A question our society needs to ask itself is "is it ethically/morally sound to use another species as
a scapegoat for our self-destructive nature?
        
        Although it cannot be denied that the science behind transgenic animals is no doubt impressive, it
                                                                                        

has resulted in the creation of animals who would otherwise never be subjected to arthritis, stomach ulcers, muscular weakness, poor vision and many other painful abnormalities. ""¦the creation of transgenic animals for xenotransplantation"¦[is] scientifically flawed and morally unjustifiable. [It carries] inherent hazards in facilitating cross-species exchange and recombination of viral pathogens. These projects ought not to be allowed to continue without full public review." (Ho, Mae-Wan, Genetic Engineering: Dream or Nightmare).

Environmental Concerns
        
        Highly significant threats are posed towards the environment by xenotransplantation. How? The animals needed in xeno research and who are candidates to be donors will increase the already massive amount of animal manure (1.4 billion tons) put out by animal-based agriculture. Pigs and pig waste cause special concerns as they have the ability to contract and spread many human diseases, meningitis, salmonella, chlamydeous, worms and influenza being just a few.
        The disposal of the remains of the genetically modified animals after a transplant is done is also a concern. Incineration, composting and burial are all unhygienic, expensive and environmentally problematic. The worry behind disposing of transgenic bodies is if they are disposed of improperly their DNA could potentially replicate, spread and recombine, picking up genes from viruses and disease in other species and consequently creating new pathogens.

Regulatory Issues
        
        A set of draft voluntary guidelines on xenotransplants was issued in September, 1996 by the Department of Health and Human Services (HHS) in the United States . Currently, xenotransplants are monitored by the FDA who has approved limited clinical trials with animal cells, organs and tissues, typically porcine. However, the FDA's support for xeno research is inconsistent with positions it has taken in the past. In 1991 Sporicidin, a disinfectant used by doctors and dentists, was recalled by the FDA who claimed it did not adequately protect patients from infectious micro organisms. FDA commissioner at the
                                                                                        


time David Kessler said " [the FDA]"¦ will not tolerate products that would permit the transmission of disease from one patient to another." This seems slightly hypocritical knowing what we do about species jumping viruses and diseases.

Alternatives
        
        Knowledge. This is key, with knowledge comes prevention. If we educate ourselves on ways to prevent the need for an organ transplant (i.e., liver or heart due to poor lifestyle) we can eliminate the need for xenotransplantation and all of the above mentioned problems disappear. Active living and a healthy diet are only 2 of many ways to prevent needing this risky surgery.
        Surgery is expensive, there is no beating around the bush. Instead of investing so much time and energy in to a science which could only benefit those who can afford it (and demographically speaking, this is not many AT ALL), our time would be more wisely spent in the development of synthetic organs and new surgical techniques to repair what you have, instead of simply replacing it. What message are we sending to young children by taking out an organ and replacing it. To me it sounds as though it is ok to eat greasy food, sit around and play video games, smoke and drink excessively. Is this not the exact opposite of what the public service commercials on leading a healthy lifestyle, (sponsored by the same government who is funding xenon research), are telling us?

The Pro's of Xenotransplants
        
        Although it may seem that there is nothing good about xenotransplantation there is evidence which suggests otherwise. The demand for human organs keeps growing while the supply is dwindling. Xenotransplantation may not be a perfect solution but there is no question that although there are concerns with the procedure it is bridging the gap for many people waiting for a transplant. People suffering from diabetes have had great success in keeping the disease under control through the use of transplanted islets
from donor pigs. This is the safest xenograft. No immunosuppressive drugs are needed and if there are
                                                                                        


complications the patients simply returns to insulin injections everyday. Xenotransplants also offer hope to people with Parkinson's disease. Something which was once thought untreatable through transplantation surgery shows great promise when fetal pig cells are injected into the brain of the patient.


Conclusion
        In conclusion we see there are both pro's and cons' to xenotransplantation, and no "right" or "wrong" answer when one gives their opinion on the topic. The procedure offers hope to many people suffering from illness, yet it worries many other. Animals rights activists, doctors, lawyers and families of potential recipients can all come up with as many reasons not to do the procedure as the patient or the people developing this technology can to do it. As of right now it is a personal choice. Something a potential recipient must deeply consider, weighing the value they place on the animal, the risks associated with it and the monetary issue. Then and only then can one truly make the decision.
        My personal opinion is that xenotransplants are cruel and inhumane. I would not want to have this procedure done to myself under any circumstances. I am a vegan and in researching this topic I discovered many disturbing things which only re enforced my views on animal rights. I do however understand the views of those considering the procedure and although I do not agree with them I respect them.
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