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Stem Cell Therapy to Prevent Type 1 Diabetes
Diabetes is one of the most common chronic diseases affecting humans - the WHO estimates that around 350 million people have diabetes globally. Approximately 10% have type 1 diabetes - a disease that is often diagnosed during childhood or adolescence. In type 1 diabetes, the pancreas does not make enough of the hormone insulin that keeps blood sugar levels in the normal range. People with type 1 diabetes must frequently take finger prick tests of their blood sugar level and receive multiple daily injections of insulin or wear an implanted insulin pump. While the cause of type 1 diabetes is not fully understood, the immune system plays a major role in causing the damage to the insulin producing cells in the pancreas. There is currently no prevention or cure for type 1 diabetes - but stem cells may be a promising new approach.
The role of stem cells
Stem cells are basic cells that have the capacity to multiply - either into specialized cells or to regenerate themselves. Cord blood stem cells are particularly unique because they not only have the capacity to develop into other cell types, but are also immune tolerant - that is they are less likely to provoke an immune response. They also contain greater numbers of regulatory T cells - a particular type of white blood cell that helps to keep the immune system in balance. This makes cord blood stem cells potentially useful for treating diseases where the immune system has 'gone astray' - such as type 1 diabetes.
Can stem cells prevent or cure type 1 diabetes?
To date no studies have shown that stem cells can prevent type 1 diabetes in humans, but cord blood has been able to prevent and also cure type 1 diabetes in mice.
The first study that used cord blood to treat children with type 1 diabetes was performed by Dr. Michael Haller and colleagues at the University of Florida. They gave children their own cord blood stem cells (that had been stored at birth) within 6 months after the children had been diagnosed with type 1 diabetes. That study succeeded in increasing the number of regulatory T cells in the children's blood and demonstrated that the cord blood infusions were safe. But the study failed to cure the children of diabetes, because the increase in regulatory T cells only lasted for 6 to 9 months. It may be that once type 1 diabetes has been diagnosed, too many of the insulin producing cells in the pancreas have already been destroyed, and it is too late for the cord blood stem cells to rescue them. Perhaps cord blood stem cells could defeat diabetes if they were given early enough to protect the insulin producing cells?
Another important study on children was performed by Dr. Piotr Trzonkowski and colleagues at the Medical University of Gdansk in Poland. They harvested regulatory T cells from children who had been diagnosed with diabetes, multiplied the cell number by culturing them in the laboratory, and returned the cells to the children. This study of high dose of regulatory T cells showed a benefit compared to a control group, because the children who received the infusion continued to make insulin.
Cord blood from donors has also been used to treat diabetics as part of Stem Cell Educator therapy. This work was conducted by Dr. Yong Zhao and colleagues from both the University of Illinois and the General Hospital of Jinan Military Command in China. The study treated adults who had been diagnosed with type 1 diabetes for more than a year. The white blood cells of the patients were passed through filters holding cord blood stem cells that came from donors in a public cord blood bank. After mingling in the filter for 2 to 3 hours, the "re-educated" immune system cells were returned to the patients. Afterwards, the patients exhibited improved diabetes control, needing less insulin and making more regulatory T cells.
Testing cord blood as prevention of type 1 diabetes
In Australia, we are conducting a pilot trial called "Cord blood Reinfusion in Diabetes" (CoRD) that seeks to prevent diabetes with cord blood. The study is supported by the family cord blood bank Cell Care. To be eligible, children must: 1. have their own cord blood in storage, 2. have a relative with type 1 diabetes, and 3. have antibodies which signal that their immune system is already attacking their insulin producing cells in the pancreas. Study participants will have their own cord blood reinfused in Children's Hospital at Westmead. The hope is that a reinfusion of their cord blood stem cells will reset the immune systems of these children, before the auto-immune damage leads to a diagnosis of type 1 diabetes.
This research is one of a number of potential avenues in which scientists hope that stem cells will help patients to preserve their insulin producing cells and thereby be cured of diabetes.