Transplants and Diabetes

Three Toronto scientists have developed an organ transplant
procedure that could, among its many benefits, reverse

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.