By Stephen Lin, PhD., CIRM Senior Science Officer
Type 1 diabetes affects millions of people. It is a disease where beta islet cells in the pancreas are targeted by the body’s own immune system, destroying the ability to produce insulin. Without insulin, the body cannot break down sugars from the bloodstream that produce energy for organs and that can lead to many significant health problems including damage to the eyes, nerves, and kidneys. It is a life-long condition, most commonly triggered in children and teenagers. However, type 1 diabetes can manifest at any time. I have a family member who developed type 1 diabetes well into adulthood and had to dramatically alter his lifestyle to live with it.
Fortunately most people can now live with the disease. There was a time, dating back to ancient civilizations when getting type 1 diabetes meant early death. Thankfully, over the past hundred years, treatments have been developed to address the disease. The first widespread treatment developed in the 1920s was injections of animal insulin isolated from pancreatic islets in cattle and pigs. Over 50 years later the first genetically engineered human insulin was produced using E. coli bacteria, and variations of this are still used today. However, the disease is still very challenging to manage. My family member constantly monitors his blood sugar and gives himself injections of insulin to regulate his blood sugar.
A therapy that can self-regulate blood sugar levels for diabetes would greatly improve the lives of millions of people that deal with the disease. Pancreatic islet cells transplanted into patients can act as a natural rheostat to continually control blood sugar levels. Pancreas organ transplantation and islet cell transplantation are treatment options that will accomplish this. Both options are limited in supply and patients must be kept on life-long immunosuppression so the body does not reject the transplant. Pancreatic beta cells are also being developed from pluripotent stem cells (these are cells that have the ability to be turned into almost any other kind of cell in the body).
Now in an advance using pluripotent stem cells, Dr. Ronald Evans and his team at the Salk Institute have created cell clusters called organoids that mimic several properties of the pancreas. Previously, in work supported by CIRM, the team discovered that a genetic switch called ERR-gamma caused the cells to both produce insulin and be functional to respond to sugar levels in the bloodstream. They incorporated these findings to create their functional islet clusters that they term “human islet-like islet organoids” (HILOs). Knowing that the immune system is a major barrier for long term cell replacement therapy, Dr. Evans’ team engineered the HILOs, in work also funded by CIRM, to be resistant to immune cells by expressing the checkpoint protein PD-L1. PD-L1 is a major target for immunotherapies whose discovery led to a Nobel Prize in 2018. Expressing PD-L1 acts as an immune blocker.
When the PD-L1 engineered HILOs were transplanted into diabetic mice with functioning immune systems, they were able to sustain blood glucose control for time periods up to 50 days. The researchers also saw significantly less mobilization of immune cells after transplantation. The hope is that these engineered HILOs can eventually be developed as a long term therapy for type 1 diabetes patients without the need for lifelong immunosuppression.
In a press release, the Salk researchers acknowledge that more research needs to be done before this system can be advanced to clinical trials. For example, the transplanted organoids need to be tested in mice for longer periods of time to confirm that their effects are long-lasting. More work needs to be done to ensure they would be safe to use in humans, as well. However, the proof of concept has now been established to move forward with these efforts. Concludes Dr. Evan’s in the announcement, “We now have a product that could potentially be used in patients without requiring any kind of device.”
The full study was published in Nature.