April 26, 2001 -- Undeveloped cells derived from mouse embryos can be coaxed in the lab into becoming a specialized type of insulin-producing cell. If the technique works in humans, it could represent a major breakthrough in the treatment of diabetes and could even replace injected insulin, report researchers in the April 26 issue of the journal Science.
But because the newly minted insulin-secreting cells are derived from a type of stem cell found only in the earliest stages of embryonic development, a human version of the treatment would face stiff opposition from the political and religious right, who oppose any medical research using cells from human embryos -- even when embryos created for the purpose of in vitro fertilization go unused and are slated for disposal.
"It's so short-sighted to try to deprive the world of a very promising intervention like this," stem cell researcher Evan Snyder, MD, PhD, tells WebMD. Snyder was not involved in the study.
If you'd like to share your opinion on the controversy, or just have a question about diabetes, go WebMD's Diabetes board, moderated by Gloria Yee, RN, CDE.
Type 1 diabetes is caused when the immune system turns on itself and begins to destroy its reservoir of beta-islet cells of the pancreas, the only cells in the body that produce the hormone insulin. Insulin is essential for the storage and efficient use by the body of energy obtained from food. People with type 1 diabetes must take multiple daily injections of insulin to replace the hormone that the missing beta cells would otherwise produce. In type 2 diabetes, the body still produces insulin, but the cells lose their ability to respond to it.
As Ron McKay, PhD, and colleagues from the National Institute for Neurologic Disease and Stroke report, it is possible to nudge stem cells from mouse embryos into becoming mature cells with all of the hallmarks of beta-islet cells, including their ability to release insulin in the presence of blood sugar.
When the cells were injected into mice with a form of drug-induced diabetes, the cells took on all the characteristics of insulin-secreting cells, and the mice maintained their weight and survived longer than similar, untreated animals. The injected cells did not fully restore blood sugar levels in the treated mice to normal, but this may have been due to the fact they are much less efficient at producing insulin than native beta cells, or because they were injected under the skin rather than directly into the pancreas.
McKay and colleagues built on earlier research showing that cells that grow up into brain and nerves are strikingly similar in early embryonic development to cells that go on to become part of the endocrine system, which controls hormones such as insulin.
"There has always been a belief that endocrine cells and neural cells have a kind of common history, way back early in development, and there are a lot of similarities between them, particularly beta cells of the pancreas," says Snyder, assistant professor of neurology at Harvard Medical School. "This work would support the common heritage that the two cell types have, and it would make some sense, in fact, that you could use selection techniques for neural cells to then derive endocrine cells, even from cells that seem to have the broad range of potential as embryonic stem cells do."
Although researchers have had some success with transplanting beta-islet cells from cadavers into people with type 1 diabetes, such cells are limited in supply and have the potential to evoke the same kind of harmful immune response from the patients as their own beta-cells do. In contrast, stem cells have the potential to provide a virtually limitless source of beta-islet cells.
But whether scientists will be able to develop human embryonic stem cells to their full potential is another question. Last week, the Bush administration ordered the National Institutes of Health to indefinitely postpone the first meeting of a committee that would review requests for government funding of research using stem cells derived from human embryos.
The move, combined with other statements and policy changes issued by Bush administration officials has scientists worried that critical medical research may be in jeopardy.
"Soon the Bush administration will decide the fate of human embryonic stem cell research at U.S. government-funded institutions, and the outcome of that decision will greatly influence the role of [embryonic stem cell] science in human developmental biology around the world," write stem cell researchers Irving Weissman, MD and David Baltimore, PhD in an accompanying editorial. "But although the forces that science brings to this field are powerful, the future of [embryonic stem cell] research will largely be determined by other interests: politics, organized religion, commerce, the legal community, and patient advocacy groups. The decision-making process needs to develop a policy that is fact-based and serves the best interests of society as well as science."
Weissman is professor of pathology and developmental biology at Stanford University. Baltimore is a Nobel Laureate and president of the California Institute of Technology, in Pasadena, Calif.
Their editorial echoes concerns expressed by another public figure. In testimony before Congress last September, actress Mary Tyler Moore, who has lived with type 1 diabetes for more than 30 years and represents the Juvenile Diabetes Foundation, spoke on behalf of the millions of people, both living and yet to be born, who could benefit from treatments developed through stem cell research. "Our obligation is to those of us who are here," she told lawmakers.