Diabetes-treating implant produces oxygen to support islet cells
Daily insulin injections are painful and inconvenient, which is why scientists are developing implants that treat diabetes without any need for needles. A new one looks particularly promising, as it produces oxygen to feed onboard islet cells.
In most people, pancreatic islet cells produce the insulin which is required to maintain proper blood sugar levels. Unfortunately, the immune system of people with Type 1 diabetes destroys those cells, so insulin must be manually injected into the bloodstream.
One alternative to those injections involves implanting islet cells that have either been harvested from a cadaver or derived from stem cells. While doing so does work in many cases, patients have to take immunosuppressive drugs for the rest of their lives in order to keep those cells from being rejected.
Scientists have tried encapsulating islet cells in tiny flexible implants that shield the cells from the host's immune system, yet still allow insulin produced by those cells to diffuse into the bloodstream. These implants also prevent life-sustaining oxygen from reaching the cells, however, which means those cells won't last long.
Some implants have addressed that shortcoming by incorporating either a preloaded oxygen chamber or chemical reagents which produce oxygen. Both the oxygen and the reagents run out over time, though, so the implants will have to be replaced or refilled.
Seeking a longer-term alternative, a team from MIT and Boston Children’s Hospital recently developed the new device.
It's packed with hundreds of thousands of islet cells, along with a proton-exchange membrane that splits water vapor (which occurs naturally in the body) into hydrogen and oxygen. The hydrogen harmlessly diffuses, while the oxygen goes into a storage chamber in the implant. A thin, permeable membrane in that chamber then allows the oxygen to flow through to the chamber containing the islet cells.
A small voltage is required to trigger the water-vapor-splitting action, which can be wirelessly relayed from an external magnetic coil to an antenna in the implant. The coil could be adhered to the patient's skin, adjacent to the implant site.
In tests performed on diabetic mice, a full oxygen-generating version of the device was implanted under the skin of one group of the rodents, while another group received a non-oxygenated version that simply contained the islet cells. Although both groups initially did well, the non-oxygenated group became hyperglycemic within approximately two weeks.
Plans now call for tests to be performed on larger animals, followed by clinical trials on humans. It is hoped that the technology could also be utilized to produce other types of therapeutic proteins, for the treatment of other conditions. In fact, the device has already been used to support cells that produce erythropoietin, which is a protein that stimulates red blood cell production.
"There are a variety of diseases where patients need to take proteins exogenously, sometimes very frequently," said MIT's Prof. Daniel Anderson, senior author of the study. "If we can replace the need for infusions every other week with a single implant that can act for a long time, I think that could really help a lot of patients."