However, the supply of islets from cadavers is extremely limited, so medical researchers are looking elsewhere. Several research groups have reported that embryonic stem cells and cells found in the pancreas (other than beta cells) could be converted into insulin-producing cells, but until now no one had specifically explored the bone marrow as a source of beta cells. (The bone marrow normally replenishes blood cells and in recent years researchers have shown that stem cells from the marrow can become cells of other organs.)
The CRE-loxP system is a sort of DNA editing technique that molecular biologists widely employ to engineer genes. In the new study, Dr. Hussain used the system to ingeniously create male mice with bone marrow cells that produce a protein called enhanced green fluorescent protein (EGFP) only in the presence of activated insulin genes, which are typically found in pancreatic beta cells. EGFP imparts a green glow to cells, which makes it easy to identify them. He then transplanted the bone marrow from these males into female mice whose bone marrow had been destroyed by radiation.
After four to six weeks, Dr. Hussain detected a small number of the glowing green cells in the pancreatic islets of Langerhans of the female mice. Further analysis showed that these cells came from the bone marrow and functioned as the insulin-producing beta cells. These cells all contained the Y chromosome, which could only have come from the
Contact: Pamela McDonnell
New York University Medical Center and School of Medicine