January
23, 2001
Presentation
Write-Up
ASC
128
My
topic for my presentation was on the use of animal organs in human transplants.The
technical term used to describe the use of animal organs along with their
tissue and organs is known as xenotransplantation.
Xenotransplantation
has been in existence since the 1700’s, but the use of an animal’s whole
organ started in 1906.The French
surgeon, Mathieu Jaboulay was the first person to perform an animal-to-human
transplant.Jaboulay implanted the
kidney of a pig in one woman and the liver of a goat into another woman,
but bother never survived. Sine then there has been between 20-50 xenotransplants.However,
in the past few years there has been a tremendous shortage of human organs.Because
of the shortage more than 40,000 Americans are on waiting lists for human
organs, one third to one half will die before an organ can be found.Transplant
patients are more likely to die waiting for a human donor than in the first
two years of transplantation.These
finding have led doctors to consider xenotransplantation.
The
animal that is a human’s closest genetic kin is the chimpanzee, sharing
more than a 99% genome.This would
minimize the chance of organ rejection.The
longest survivor of xenotransplantation was a woman who received a chimpanzee
kidney in1964; she lived for nine months.The
problem with using the chimpanzee is that they are extinct creatures so
there are not many to use in experimentation.Other
animals that can however be considered are the baboon and the pig.
Baboons
are also genetically close to humans, so they are most often used for initial
experiments.Baboons are not endangered
and they are able to breed easily so they can be ver useful from that perspective.In
October of 1984 doctors at Loma Linda University Medical Center in California
transplanted the heart of a 7 month old baboon into a newborn human baby
(“Baby Fae”) born with a malformed heart.She
lived for only twenty day after dying from kidney failure.The
first baboon to human liver transplant was done in 1992.A
35-year-old male with Hepatitis B (which affects the liver) was given the
liver of a baboon because it is believed that the Hepatitis B virus can
not affect baboons, therefore the virus would not affect the liver. However
the drawback of using baboons is that they harbor many viruses. For long
term use pigs are considered to be a better choice.
Pigs
have a similar anatomy to humans and their organs are of a suitable size
for use in adult patients.Pigs
are the healthiest primates and they breed easily producing litters at
a time.One of the best things about
pigs is that they can be genetically manipulated to reduce the possibility
and severity of transplant rejection.In
1992 two women were given the liver of pigs to act as “bridges” until organs
were found.On of the women who received
the pig liver kept it outside her body in a plastic bag and hooked it up
to her main arteries.The woman
survived long enough to receive a human liver transplant. As with any surgery,
there are risks to xenotransplantation.
The
main concern of doctors is that the body will treat the animal organ as
a foreign object and reject the organ.Everyone
is born with an immune system that learns how to detect and resist foreign
substances in the body called antigens.The
antigens trigger the body’s white cells called lymphocytes to produce antibodies.Different
lymphocytes recognize and produce antibodies against particular agents.Doctors
give patients immunosuppressive drugs so the immune system would be lower
and there would less chance of rejection.The
problem with immunosuppressive drugs is that in massive amounts it can
cause severe toxicity.Another major
risk of xenotransplantation is that animal viruses can jump the species
barrier and kill humans (xenosis: diseases that can be transmitted to humans
under natural conditions).Some doctors
feel that by performing xenotransplantaion it will cause an outbreak just
as the worldwide spread of the HIV infection, which is believed to be transmitted
from African monkeys to humans. They also believe that using animal organs
in human transplants breaks the “natural barriers” that prevent infection
and the use of animal organs will only help the transmission of infectious
diseases from animals to humans.There
are over 20 known potentially lethal viruses that can be transmitted from
non-human primates to humans.A
greater concern should be placed on the diseases that doctors do not know
about.This is because some viruses
may be harmless to their animal hosts can be deadly when transmitted to
humans (xenotropic organisms).With
all of these risks xenotransplantation does have benefits.
Xenotransplantation
will save the lives of thousands of people who are on the waiting for human
organs and it can provide unlimited numbers of organs, making transplantation
available to a greater number of patients.Xenotransplantation
can also serve as a bridge for those on the waiting list for organs.With
the design of new immunosuppressive drugs it will not only help transplant
patients but those with arthritis, diabetes, and multiple sclerosis.Whenever
researching such a controversial issue on should consider the ethical issues
surrounding the topic.
There
are many ethical concerns about xenotransplantation.One
of the biggest concerns is the possibility of diseases spreading not only
to the patient, but also into the general population.What
has also stirred up major controversy is do we have the right to sacrifice
thousands of animals for human survival.Another
major concern is where the funding for xenotransplantation will come from,
the taxpayers or the individual. Then we have some religious groups who
feel that xenotransplantation is “Playing God”.There
are so many issues and concerns surrounding this topic, but the responsibility
of xenotransplantation becoming a new type of surgery is up to the doctors
to prove to the FDA that this will be a safe process.
Regarding
my evaluations, I believe overall they were fair and I do appreciate that
from my classmates and yourself.One
student made the comment that I seemed very nervous, but the truth is I
was very relaxed maybe it was because of my cold changed my voice.Everyone
really impressed me when they actually had opinion on the topic, I think
the class discussion went very well.I
did forget to pass around a petition that I had from the Council for Responsible
Transplantation just in case someone wanted to sign it, but everyone seemed
to agree with xenotransplantation.