The results of a breakthrough study conducted last year by researchers at Massachusetts General Hospital (MGH) suggest that spleen cells may have the ability to develop into insulin-producing pancreatic islet cells in adult animals with type 1 diabetes, replacing old islet cells that were destroyed by the disease. This exciting finding could lead to a potential cure for type 1 diabetes, a disease that is less common in minority populations than type 2 diabetes but is still a serious health problem. Among minority patients with diabetes, 5%-10% of African Americans, 5%-10% of Hispanics and 2%-4% of American Indians have the type 1 form of the disease.
Type 1 diabetes develops when the body's immune system attacks and destroys islet cells in the pancreas, which secrete insulin. As islet cells die, insulin production ceases and blood sugar levels rise, damaging organs throughout the body.
The MGH study, led by Dr. Denise Faustman, director of the hospital's immunobiology laboratory, builds on the results of a 2001 study that discovered a treatment that cures advanced type 1 diabetes in mice.
This earlier study, also led by Faustman, had found a way to retrain the mice's immune systems to stop attacking islet cells, in part by injecting the mice with adult donor spleen cells. The researchers expected to follow that process, which eliminated the autoimmune basis of the animals' diabetes, with transplants of donor islet cells. However, they were surprised to find that most of the mice did not need the transplant: Their bodies were producing normal islet cells that were making insulin.
The source of these regenerated, healthy islet cells is even more surprising: The results of the 2003 study, published in the November 14 issue of Science, strongly suggest that they had developed from the donor spleen cells. "The unanswered question from [the first] study was whether this was an example of rescuing a few remaining islet cells in the diabetic mice or of regeneration of the insulin-secreting islets from another source," says Faustman. "We've found that [new islet cells] were growing from both the recipients' own cells and from the donor cells. This discovery opens up an entirely new approach to diabetes treatment."