HITS | News Release: HITS Project Director Addresses ADA Diabetes Expo (12-May-03)

News Release

May 5, 2003 contact:
Rich Murphy, PNRI
(206) 726-1200
rmurphy@pnri.org

HITS PROJECT DIRECTOR ADDRESSES ADA DIABETES EXPO

Looking to the Future of Human Islet Transplantation

Seattle, WA -Dr. Paul Robertson, President and CEO of the Pacific Northwest Research Institute, and project director of the HITS program in Seattle, looked to the future at this spring's ADA-sponsored Diabetes Expo. Drawing on the results of phase one of the islet program in Seattle, Robertson summarized for the audience four important questions involved in improving human islet transplantation for type 1 diabetes.

Robertson's questions were all provocative, challenging the existing assumptions and procedures for islet transplantation. And he made no apologies for the complexity of his answers. "I'm not going to talk down to you," he said. His audience was clearly up to the challenge. They were eager and informed. They included patients with diabetes as well as others with diabetes in their families, and they have been following the research developments in islet transplantation with great attention.

How Many Islets

"How many islets should be needed to render type 1 diabetic patients insulin-free?" Robertson asked. To answer this question, he pointed to data from a number of pancreas (and auto-islet) transplant patients who continue to be insulin-free years after their transplants. Their experience suggests an answer that should make the provision of healthy islets more plausible than it is at present. "There's no reason why we should need two or three pancreases to achieve insulin-freedom for islet transplants," Robertson said. According to his analysis of the available evidence, 300,000-350,000 islets (or, roughly half or less of a healthy pancreas) should be sufficient.

Islet Viability

Robertson's second question was "How can islet viability after organ procurement be improved?" One of the important factors in the success of islet transplantation today is the viability of the islets that are recovered from the donor pancreas. The more viable they are, the fewer are needed. So the HITS program is studying two refinements in the technology of the process: a new, more oxygen-rich method for preserving the pancreas until the islets can be removed, and a less rigorous method of purifying the islets once they have been isolated. Experience with auto-islet transplantation leads Robertson to believe that islets left closer to their natural state thrive better than excessively purified islets once they are transplanted.

Follow-up Infusions

For those patients who require a follow-up islet infusion, Robertson asked, "How much time should elapse between sequential islet transplantations?" Patients being transplanted within the current research protocol sometimes receive one or more subsequent islet infusions. Robertson believes that if these are performed without sufficient delay, the islets may not have time to establish themselves in their new site and to begin their full and healthy functioning. Such subsequent transplants might therefore be unnecessary. "Let's wait," Robertson said. "At least three months. Let's give the islets a chance to get settled and working, and we may discover that they do just fine."

The theme driving Robertson's talk was a look to the future. Each of his questions proposed a way to improve the process of islet transplantation by drawing on the research experience to date.

The Liver

The last of his four questions challenged the idea that the liver is the optimal site for islet transplantation. Currently islets are transplanted into the portal vein of the recipient's liver because the liver is a circulation-rich environment where islets seem to thrive. But there are also reasons for thinking that the liver may not be optimal. For one thing, there are the potentially toxic effects of drug concentrations in the liver on islets in residence there. Another downside is marked by the various procedural complications encountered in recent intra-hepatic transplants.

Robertson conceded that he couldn't provide a confident answer to this question yet. Is the liver the best place for transplanted islets? His answer: "Maybe. Maybe not."

But one thing is certain after hearing him address the Expo visitors. The phase 1 research completed by the HITS program here in Seattle-as well as the results of the islet transplantation being conducted at partner institutions in the U.S. and abroad-has led to new ideas about how to make this enormously promising treatment even more effective.