WHAT ARE TRANSPLANTATION PROCEDURES?
Beta-Cell Transplantation
After a very successful small trial,
major clinical trials are now underway using a beta-cell
islets transplantation procedure called the Edmonton
protocol and more recent variations. In one 2001 report
of 12 patients, four had normal glucose levels, five
had impaired glucose tolerance, and three had post-transplant
diabetes. Those who still had diabetes, however, required
much less intensive treatments. These are still encouraging
findings and longer and larger trials are under way.
The procedure involves the following steps:
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As soon as there are sufficient numbers of islets
for transplantation, the patient is given intravenous
antibiotics and oral vitamins E, B6, and A.
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A machine isolates islet cells taken from two
separate donors. (Cadavers are used for donated
islets.)
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Once the islets have been isolated, they are
injected directly in a major vein in the patient's
liver.
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The islets are carried to capillaries in the
liver where they produce insulin.
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Key to the success of this treatment are specific
agents, particularly sirolimus, or rapamycin (Rapamume),
that are used to suppress the immune system. (Unlike
other transplantation procedures, the agents used
do not contain steroids, which destroy islet cells.)
One center is also testing another agent called
humanized OKT3 gamma-1 (ala-ala), which may allow
the need for only one donor. Immunosuppressants
are needed for the rest of the patient's life
so that the body does not reject these foreign
islet cells.
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The procedure has to be performed two or more
times over a period of two to three months, requiring
multiple pancreas donors in order to achieve complete
independence from insulin therapy. This is a major
limitation to the procedure. Some researchers
argue that transplanting fewer cells from one
donor would still achieve sufficient health benefits,
and would be accessible to more people. More research
is needed to discover just how successful transplantation
from one donor could be. One small study reported
some success with the use of pancreases from cadavers.
Other approaches are using islet cells from pigs,
fetal islet cells, or cloning techniques.
Organ Transplantation
Whole pancreas transplants and double
transplants of pancreases and kidneys are proving to
have a good long-term success rate for selected type
1 patients. The operations help to prevent further kidney
damage, and long-term studies are finding that they
may even eventually reverse some existing damage. There
is some evidence that heart disease and diabetic neuropathy
improves after pancreas transplantation (although not
retinopathy). One 10-year study reported that survival
rate at 10 years was 76.3%, and two-thirds of the patients
had both pancreas and kidney function. Immunosuppressive
drugs are also needed life-long with this procedure.
Experts are now recommending transplants in cases of
end-stage kidney failure or when diabetes poses more
of a threat to the patient's life than does the transplant
itself. |
