Daily injections of insulin are painful and inconvenient, so scientists are developing implants that can treat diabetes without the need for injections. A new implant looks particularly promising because it produces oxygen to provide nutrients to the implanted islet cells.
In most people, pancreatic islet cells produce the insulin needed to maintain proper blood sugar levels. Unfortunately, the immune system of people with type 1 diabetes destroys these cells, so insulin must be injected manually into the bloodstream.
One alternative to injecting insulin is the implantation of islet cells extracted from cadavers or derived from stem cells. While this does work in many cases, patients must take immunosuppressants for life to prevent these cells from being rejected.
Scientists have tried wrapping islet cells in tiny, flexible implants that shield the cells from the host's immune system but still allow the insulin produced by these cells to diffuse into the bloodstream. However, these implants also prevent life-sustaining oxygen from entering the cells, meaning the cells don't live as long.
Some implants address this deficiency by incorporating prefilled oxygen chambers or chemical agents that produce oxygen. Over time, however, the oxygen and reagents are depleted, so the implant must be replaced or refilled.
A team at MIT and Boston Children's Hospital recently developed a new device in pursuit of a longer-term alternative.
The device houses hundreds of thousands of islet cells and a proton exchange membrane, which separates water vapor (naturally found in the human body) into hydrogen and oxygen. Hydrogen diffuses harmlessly, while oxygen enters the implant's storage chamber. A breathable membrane in the storage chamber then allows oxygen to flow to the storage chamber containing the islet cells.
Triggering the water vapor splitting requires a small voltage, which is transmitted wirelessly from an external magnetic coil to the implant's antenna. The coils can be adhered to the patient's skin, immediately adjacent to the implant site.
In experiments on diabetic mice, one group had a complete oxygen-producing device implanted under their skin, while another group received a non-oxygen-producing device containing only pancreatic islet cells. While both groups of rodents did well initially, the non-oxygenated group developed hyperglycemia within about two weeks.
Current plans are to conduct trials on larger animals and then clinical trials in humans. It is hoped that this technology can also be used to produce other types of therapeutic proteins to treat other diseases. In fact, the device has been used to support cells' production of erythropoietin, a protein that stimulates the production of red blood cells.
"Patients with a variety of diseases require exogenous protein intake, sometimes very frequently," said Daniel Anderson, a professor at MIT and senior author of the study. "If we could replace the need for infusions every other week with a single implant that works long-term, I think that could really help a lot of patients."