In this April 5, 2013 photo provided by Harvard University, Harvard Stem Cell Institute Co-Director Doug Melton, right, and Peng Yi, a post doctoral fellow in his lab, review data from recent experiments in Melton's lab in Cambridge, Mass. Melton and Yi have identified a hormone that can sharply boost a mouse's supply of cells that make insulin, a discovery that may someday provide a diabetes treatment. People make the hormone naturally, and the new work suggests that giving them more might one day let patients avoid insulin shots. (AP Photo/Harvard University)

Associated Press
In this April 5, 2013 photo provided by Harvard University, Harvard Stem Cell Institute Co-Director Doug Melton, right, and Peng Yi, a post doctoral fellow in his lab, review data from recent experiments in Melton's lab in Cambridge, Mass. Melton and Yi have identified a hormone that can sharply boost a mouse's supply of cells that make insulin, a discovery that may someday provide a diabetes treatment. People make the hormone naturally, and the new work suggests that giving them more might one day let patients avoid insulin shots. (AP Photo/Harvard University)
In this April 5, 2013 photo provided by Harvard University, Harvard Stem Cell Institute Co-Director Doug Melton, right, and Peng Yi, a post doctoral fellow in his lab, review data from recent experiments in Melton's lab in Cambridge, Mass. Melton and Yi have identified a hormone that can sharply boost a mouse's supply of cells that make insulin, a discovery that may someday provide a diabetes treatment. People make the hormone naturally, and the new work suggests that giving them more might one day let patients avoid insulin shots. (AP Photo/Harvard University)