Islet-Cell Transplants: Stop Diabetes?
Transplanted Cells Help Prevent Life-Threatening Blood-Sugar Crashes
Sept. 27, 2006 -- Islet-cell transplants aren't -- yet -- a cure for diabetes, an international clinical trial shows.
The trial tested the Edmonton protocol, a revolutionary technique for transplanting insulin-making pancreas cells from cadavers to desperately ill diabetes patients. A few years ago, it seemed that the technique -- in which islet cells are infused into the liver -- could free most patients from the need for insulin shots.
It does, find Edmonton protocol inventor James Shapiro, MD, PhD, and colleagues. But now it's clear that only some 10% of study patients remained insulin-free after five years. Even so, the transplanted cells kept many of the patients from having life-threatening blood-sugar crashes.
This means that the hunt for a diabetes cure isn't over. But researchers are on the right trail, says study researcher Camillo Ricordi, MD, chief of cellular transplantation and scientific director of diabetes research at the University of Miami Miller School of Medicine.
"The drawback right now is that virtually all patients show slow deterioration of islet function over several years," Ricordi tells WebMD. "We will have to develop strategies to educate the recipient's immune system to tolerate the islet cells. When we do this, we can treat all type 1 diabetes patients -- and also type 2 diabetes patients who are dependent on insulin."
The study appears in the Sept. 28 issue of The New England Journal of Medicine.
Making the Liver Work as a Pancreas
Shapiro, Ricordi, and colleagues carefully screened some 2,000 desperately ill type 1 diabetes patients at nine diabetes centers in the U.S. and Europe. They picked only 36 subjects -- all adults (average age, 41), all with long-term diabetes (27 years on average), and all failing to get control of their blood sugar with insulin injections.
The patients received insulin-making islet cells from brain-dead organ donors. The carefully prepared islet cells were infused into the patients' livers -- where, it was hoped, the cells would survive and multiply. All patients received immune-suppressing drugs to prevent rejection of the transplanted cells. These drugs were carefully selected to minimize their toxic effects on the transplanted cells.
At some point during the study, 58% of the patients no longer needed insulin injections. But three out of four of these patients again needed insulin within two years.
Even so, the islet cells kept working in some patients. These patients no longer had severe blood-sugar crashes.
"Perhaps ... even a small number of islets may be able to protect against this life-threatening complication," write Mount Sinai School of Medicine researchers Jonathan S. Bromberg, MD, PhD, and Derek LeRoith, MD, PhD, in an editorial accompanying the study.
Bromberg and LeRoith suggest that the study results represent a "glass half full or half empty" situation.
"The Edmonton protocol is clearly orders of magnitude better than previous attempts at islet transplantation," they suggest. "The problem remains that the medium- to long-term results are not durable, so much more work is needed."
Ricordi is confident that future advances will solve all these problems, allowing islet transplants to regenerate the body's ability to make insulin and control blood sugar.
"Regenerative medicine will in the future be a cure for diabetes," he says. "Then the challenge will be that the few thousand donor organs available each year will not be sufficient for the millions of patients who would benefit from this treatment."