Transplants and Diabetes

Three Toronto scientists have developed an organ
transplant procedure that could, among its many
benefits, reverse diabetes. The procedure was
developed by Bernard Leibel, Julio Martin and
Walter Zingg at the University of Toronto and the
Hospital for Sick Children. The story of their work
began in 1978, when they delved into research
which had never before been tried. They wanted
to determine if the success rate of organ
transplants would increase if the recipient was
injected with minute amounts of organ tissue prior
to the transplant. The intention was to adapt the
recipient to the transplanted tissue and thereby
raise the threshold of rejection. In the case of the
diabetes experiment, this meant injecting rats with
pancreatic tissue before transplanting islets of
Langerhans, small clusters of cells scattered
throughout the pancreas which produce insulin,
glucagon, and somatostatin. In their first
experiment, outbred Wistar rats were injected
with increasing amounts of minced pancreas from
unrelated donor rats for one year while a control
group was left untreated. Then both the treated
and control groups received injections of
approximately 500-800 islets of Langerhans from
unrelated donors. Of the five treated animals, two
became clinically and biochemically permanently
normal. Six months later, Martin examined the
cured rats and found intact, functioning islets
secreting all of their hormones, including insulin.
None of the controls were cured. Encouraged by
their first results, Leibel, Martin, and Zingg
decided to repeat the experiment with rats with
much stronger immune barriers (higher levels of
rejection). Seven rats out of nine were cured. "We
set up a protocol and worked patiently with small
numbers," says Leibel, "but the results are
indisputable." In addition to reversing diabetes,
there are two other benefits to the pre-treatment
procedure, according to the scientists. The first is
that the pancreas produces all the other hormones
of a normal pancreas, not just insulin. The second
benefit is that the transplant recipient doesn\'t have
to take immunosuppressive drugs, which are so
toxic for diabetics. At present, diabetics who
receive a transplanted pancreas must take such
drugs for life. The scientists eventual goal is a
human trial, but they admit it will be years before
such a study is conducted. The obvious benefit for
diabetics, if human trials prove successful, would
be a return to a normal life without dietary
restrictions or insulin shots. But to Liebel, the most
important reason to continue research is to
eliminate the debilitating, degenerative diseases
such as kidney, eye and heart failure that
eventually plague the aging diabetic.

Category: Science