May 20, 2010
By Hillary Hoffman for Diabetes1
According to the American Diabetes Association, almost 6% of the US population currently suffers from diabetes. Most of these are Type 2, or insulin-resistant, diabetics. Type 2 diabetics can often control their diabetes with the help of diet, exercise, and in some cases medication. The outlook is bleaker for Type 1 diabetics, who suffer from an autoimmune disease for which no cure yet exists. In Type 1 diabetes, the body’s immune system attacks and destroys pancreatic islet cells, the cells responsible for the production of insulin. Type 1 diabetics are therefore also referred to as “insulin dependent.” A normal day in the life of a Type 1 diabetic includes scrupulous attention to blood glucose levels and several insulin injections. Insulin may also be administered by an insulin pump.
Stem cells offer an intriguing option for the treatment of Type 1 diabetes. If the destroyed islet cells could be replenished with stem cells, the body might be able to start making its own insulin again.
The idea of replacing islet cells, or even the entire pancreas, is not a new one. Each year, over one thousand Type 1 diabetics receive a pancreas transplant. After one year, over 80% of the transplant recipients have no diabetic symptoms and no longer have to take insulin. So, what’s the drawback?
For one thing, the number of organs available for transplantation far exceeds the number of Type 1 diabetics. Moreover, transplantation is a risky surgical procedure that requires patients to embark on a life-long regime of immunosuppressants. The immune system suppression leaves the patient vulnerable to a host of other infections. In other words, the cure might be worse than the disease. In fact, the dangers of immunosuppressant therapy are so great that many hospitals will not consider a pancreas transplant unless the patient is also in need of a kidney.
Successes have also been realized when patients have received injections of islet cells. While this procedure is less extreme than a whole-organ pancreas transplant, the risks and drawbacks are similar. The donor cells must be extracted from a suitable cadaver within 8 hours of death, then immediately injected into the patient. Furthermore, patients who receive islet cells must also undergo immunosuppressive therapy.
If you're thinking about a stem cell transplant:
Consider joining a clinical trial
Keep up-to-date on current research
Think about waiting a few years until the procedures are better developed
Stem cell transplants would eliminate the difficulty of finding a suitable, genetically compatible donor cadaver. Doctors could even transplant a patient’s own stem cells into the pancreas. In fact, they did just that in a clinical trial published in 2009. Doctors removed blood stem cells from twenty three Type 1 diabetics and re-implanted those cells into the patients by intravenous injection. The majority of the patients became insulin-free and stayed that way for an average of 31 months. The patients didn’t have to wait for suitable donors to become available since their own cells were used, but like the transplant patients, they were put on immunosuppressant therapy.
Why? Remember that Type 1 diabetes is an autoimmune disease, which means that the patients’ immune systems would immediately destroy the new insulin-producing cells formed from the stem cells. To avoid this, the stem cell recipients’ immune systems were chemically suppressed, which resulted in predictable side effects. Out of the 23 patients in the study, 2 developed pneumonia, 3 developed endocrine problems, and 9 faced issues with sperm deficiency.
Indeed, in the progress toward a long-term fix for Type 1 diabetes, the autoimmunity is the hardest hurdle to overcome. Researchers remain hopeful that they will find a way to engineer stem cells to escape or reduce detection by the immune system. Another idea is to somehow encapsulate the injected cells in a material that would allow insulin to pass freely but would not allow the stem cells or their derivatives to interact with the immune system. Both of these ideas have yet to be realized in a laboratory setting.
However, clinical trials for stem cell transplants continue. Earlier this month, Osiris Therapeutics announced that it has been granted Orphan Drug designation from the FDA for Prochymal, a formulation of adult stem cells, as a treatment for Type 1 diabetes. In the coming years we can expect more new advances.
What do you think about stem cell transplants as a diabetes treatment? Discuss it in the forums.
Sources and Related Links
Stem Cells and Diabetes report from the NIH
Diabetes Research Institute: Stem Cells
Stem cell therapy for type 1 diabetes mellitus. Nature reviews endocrinology, 2010 [PubMed abstract]
Image credit: Wikipedia