Encapsulated pancreatic cells may replace insulin injections

Boston: MIT scientists have developed a new material that can be used to encapsulate human pancreatic islet cells, an advance that could provide better treatment for diabetics and help replace painful insulin injections.

Patients suffering from Type 1 diabetes must monitor their blood sugar amounts and inject themselves with insulin. A better diabetes treatment, many researchers believe, would be to replace patients' destroyed pancreatic islet cells with healthy cells.

This approach has been used in hundreds of patients, but it has one major drawback - the patients' immune systems attack the transplanted cells, requiring patients to take immunosuppressant drugs for the rest of their lives.

Now, a new advance from Massachusetts Institute of Technology (MIT), Boston Children's Hospital, and several other institutions may offer a way to fulfill the promise of islet cell transplantation. The researchers have designed a material that can be used to encapsulate human islet cells before transplanting them.
In tests on mice, they showed that these encapsulated human cells could cure diabetes for up to six months, without provoking an immune response.

This approach "has the potential to provide diabetics with a new pancreas that is protected from the immune system, which would allow them to control their blood sugar without taking drugs," said Daniel Anderson, professor at MIT's
Department of Chemical Engineering.

The researchers began by exploring chemical derivatives of alginate, a material originally isolated from brown algae. Alginate gels can be made to encapsulate cells without harming them, and also allow molecules such as sugar and proteins to move through, making it possible for cells inside to sense and respond to biological signals.

However, when alginate capsules are implanted in primates and humans, scar tissue builds up around the capsules, making the devices ineffective, researchers said. They decided to try to modify alginate to make it less likely to provoke this kind of immune response.

After creating a library of nearly 800 alginate derivatives, the researchers performed several rounds of tests in mice and nonhuman primates. One of the best of those, known as triazole-thiomorpholine dioxide (TMTD), they decided to study further in tests of diabetic mice.

They chose mice with a strong immune system and implanted human islet cells encapsulated in TMTD into a region of the abdominal cavity known as the intraperitoneal space. Following implantation, the cells immediately began
producing insulin in response to blood sugar levels and were able to keep blood sugar under control for the length of the study, 174 days.

The researchers also found that 1.5-millimetre diametre capsules made from their best materials could be implanted into the intraperitoneal space of nonhuman primates for at least six months without scar tissue building up.
The research was published in the journals Nature Medicine and Nature Biotechnology.