Scientists have developed a method to shield transplanted cells from the transplant recipient’s immune system, enabling them to transplant a diabetic patient with insulin-producing islet cells that remained invisible to his immune system.

For now, the system is too complex for widespread use. “There [are] technical problems that need to be addressed to make this accessible to a regular patient,” co-author Stefan Bornstein told BioWorld Today.

But “for almost a year, these human islets survived without any immunosuppression” – the first report of a transplant that has not necessitated immunosuppressive treatment for the patient.

Islet cell transplantation, to replace the insulin-producing cells lost in Type I diabetes, is not new. The technique was pioneered in Canada in the 1990s, and the so-called “Edmonton protocol” for transplanting pancreatic islet cells was published in the New England Journal of Medicine in 2000.

But the new case study, which Bornstein and his colleagues reported in the Oct. 28, 2013, online edition of the Proceedings of the National Academy of Sciences, could open the procedure up for a larger number of patients.

For one, getting rid of the need for long-term immunosuppression, which carries the risk of infectious disease and can damage the transplanted cells, would allow larger numbers of patients to receive such transplants.

And if the transplanted cells can be kept out of the immune system’s crosshairs, it would open up the possibilities for xenotransplantation – the transplantation of cells from another species.

A shortage of donor organs is the major limiting factor in the transplantation of many different organs, and pancreatic islet cells are no exception. Bornstein, who is at the University Hospital of the German University of Dresden, said even though his institution has one of the largest programs in Germany, “large” translates into a few dozen transplant surgeries a year.

And with Type I diabetics numbering in the hundreds of thousands, “if you can offer therapy to 20 or 30 people, it’s nice for those people. But [in the big picture], it’s nothing.”

Stem cell-derived islet cells are another possibility, but Bornstein said that for now, pig islet cells are closer to human islet cells than those derived from embryonic or induced pluripotent stem cells. His team hopes to test the device with pig islet cells in future clinical trials.

Previous attempts to hide islet cells from the transplant recipient’s immune system have run up against the problem that any approach that would shield islet cells from the immune system also would shield them from red blood cells. “If you put these islets in an immunoprotective environment, you won’t have oxygen,” he said.

Researchers responded by trying to “vascularize” the packaged islets – bringing them back to their other problem. “Once you have vessels, you again have the full immune system.”

Bornstein and his team developed a chamber that shielded islets from the recipient immune system but can supply oxygen to the cells – though at this point, it needs to have its air supply exchanged daily via a port system. They transplanted that chamber into the stomach cavity of a patient with longstanding Type I diabetes. The islet cells remained functional, that is, able to release insulin in response to stimulation with glucose, throughout the 10 months that the device remained implanted, and the patient was not treated with immunosuppressive drugs.

The clinical benefit is in the eye of the beholder. Bornstein himself called the benefit “moderate,” noting that the patient continued to need insulin throughout the time he had the device implanted.

But the transplant did stabilize hypoglycemia, which is one of the biggest dangers to long-term diabetics, who don’t recognize low blood sugar levels.

And the transplant consisted of only about 100,000 cells, an amount which is not expected to allow a patient to achieve insulin independence. The minimum for such independence is on the order of 500,000 to 700,000 islet cells.

Given those numbers, Bornstein said, it’s “surprising that we got a response” at all.

And insulin independence, he said, “is not really the aim at this point.”