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.
