Brain Stem Cells Produce Insulin

This feat could lead to new ways of transplanting insulin-producing cells into diabetics.

Because embryonic stem cells are difficult to work with in a laboratory and most existing human embryonic stem cells lines are contaminated and cannot be transplanted into humans, an alternative was sought by Seung Kim, M.D., Ph.D., assisstant professor of developmental biology at the Stanford University School of Medicine (Palo Alto, CA).

Dr. Kim thought that human neural stem cells might work. "When you look at islet cells you realize that they resemble neurons,” he noted. Like neurons, islet cells respond to external signals by changing their electrical properties and releasing packages of proteins. In the case of islets, that protein is insulin. In fact, the cells that produce insulin and regulate sugar in fruit flies are neurons.

Working with the cells in a lab dish, Dr. Kim and postdoctoral fellow Yuichi Hori, M.D., Ph.D., added a cocktail of chemicals in a sequence they knew might prod the stem cells to mature into insulin-producing cells. The result was a dish full of cells that could produce insulin and release it in response to sugar being added. These cells did not perfectly mimic human islet cells. They made some, but not all, proteins normally made by islet cells and they continued to make some proteins found in neurons.

Dr. Kim then transplanted the cells into a cavity in the kidneys of mice. When the blood sugar went up in these mice, the cells released insulin. After four weeks, the cells were still alive and producing insulin. Although the amount of insulin produced was not enough to treat diabetes, the work is a first step toward that eventual goal. Dr. Kim is the lead author of a paper describing the project, published in the April 26, 2005, issue of PLoS Medicine.