May 5, 1999 IOWA CITY, Iowa -- Pregnant women with diabetes must deal with the costly and difficult tasks of checking their glucose levels and taking insulin several times daily in an effort to ensure their babies are born without birth defects. However, there may be a better way of handling the blood glucose condition during pregnancies, according to results from a University of Iowa study.
Stephen Hunter, M.D., Ph.D., UI assistant professor of obstetrics and gynecology, and his colleagues are investigating whether a transplant of specially encapsulated pancreatic islet cells can control a woman's diabetes during pregnancy. Pancreatic islet cells produce insulin, a hormone that becomes deficient in people with diabetes. The UI researchers have already tested the islet cell treatment on mice with great success.
"Successful use of this treatment in pregnancies complicated by diabetes would be a significant advancement for these patients and a major breakthrough in the battle against diabetes-induced birth defects," Hunter said.
An estimated 1.5 million women of child-bearing age in the United States have diabetes. A diabetic pregnancy is one of the leading causes of birth defects, Hunter said. A woman with diabetes is two to five times more likely to give birth to a baby with a birth defect than a woman without the condition.
Many researchers have investigated how to transplant the pancreatic islet cells into people with diabetes as a way to treat the condition permanently; however, there are problems with using the islet cells for life-long diabetes control because the body rejects the cells unless powerful anti-rejections drugs are used.
To prevent rejection without the need for anti-rejection drugs, investigators are encapsulating the pancreatic islet cells within a gelatin. The material allows small substances such as glucose and insulin to pass freely but prevents the large molecules and cells of the immune system from interacting with the islet cells and thereby prevents rejection. Unfortunately, the encapsulated islet cells do not survive for long periods of time because the isolating material decreases oxygen supply to the cells. However, in the case of a relatively short-term use, such as pregnancy, Hunter thought the approach might work.
Hunter tested his hypothesis using mice. His results showed that the mice treated with the encapsulated islet cells had significantly lower blood glucose levels throughout their pregnancies and were significantly less likely to give birth to pups with malformations (3.0 - 5.4 percent in the treated diabetic mice versus 40 - 50 percent in their untreated counterparts).
Hunter's study appears in a recent issue of the American Society for Artificial Internal Organs Journal.
Although the results are promising, there is still work to be done before researchers can test the treatment in humans, Hunter said. Many of the treated mice experienced hypoglycemia. Hunter is not exactly sure why this happened, but he speculated that it may involve an inability of isolated, encapsulated islets to communicate with one another and coordinate the total insulin secreted among them. Hunter and his colleagues are looking at how to produce genetically engineered islet cells to avoid this problem as well as how to improve the cells' use of oxygen and their ability to avoid rejection without the use of a protective barrier.
Hunter also wants to find a better way to implant the cells. In the mice, Hunter placed the cells directly into the abdomen's peritoneal cavity. Hunter would like to devise a way to implant the cells under the skin where doctors could remove the cells if complications arose.
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