Scientists in Miami have made a great advance in transplanting islet (pronounced “eye-let”) cells into people with Type 1 diabetes. Here’s the exciting work they’re doing and the serious problems they still need to overcome.
The Diabetes Research Institute (DRI) at the University of Miami looks only for a cure for Type 1. They’re not looking to manage it with better drugs or equipment. They want to make it go away.
So far, the only people who have been “cured” of Type 1 diabetes are those who received a donor pancreas or donor islet cells to restore their insulin production. There are not many of these people, but such a transplant can be done. Often it doesn’t work, though, and DRI is trying to fix that.
What is an islet cell transplant?
Islet cells are clusters of cells scattered throughout the pancreas that produce and release hormones to help regulate blood sugar. The majority of the islets are beta cells, which produce insulin to get glucose into other cells. In Type 1 diabetes, a person’s beta cells are destroyed, so no insulin can be produced. A person with Type 1 needs to inject insulin for the rest of his life, with all the risks, expenses, and effort that involves.
In theory, this problem could be fixed by transplanting new beta cells into the body, and in some lucky people, transplanted beta cells have started working. Some of these people have not needed to inject insulin for years. It’s a promising approach, but it has serious limitations.
Islet cell transplants have been around for more than 40 years, first in animals, then in human subjects. Most of the time, the new islet cells don’t last very long. Islet cells are delicate. They need a lot of oxygen and blood supply, and they need protection from immune attack and waste products. Just popping them in and leaving them doesn’t usually work.
A big problem is where to transplant them. Usually, scientists put them in the liver. Livers are easy to get to and have a good blood supply. But according to DRI, when islets are put into the liver, inflammation develops and threatens the life of the cells. Because the liver processes most of our wastes, the new islet cells are continuously exposed to harmful wastes and toxins processed there.
For these reasons, islet cell transplantation into the liver doesn’t work long-term for most people. DRI has been working on a concept they call the BioHub. The BioHub will be a “mini-organ” made out of a piece of omentum, a layer of fatty tissue that covers the organs in the lower abdomen. The omentum has a very good blood supply and can be easily modified because it’s close to the surface.
In the current version of the BioHub, DRI starts with a gel made out of blood plasma and an enzyme called thrombin. Thrombin helps blood clot. The transplanted beta cells are placed in this gel, which is attached to a piece of omentum that is then folded over into a pouch. This creates a nice, safe space for the beta cells to grow. The gel is gradually absorbed by the body, leaving the healthy cells in place in their pouch.
Because beta cells need so much oxygen, DRI scientists figured out how to supply it temporarily. They engineered a material that releases a lot of oxygen for the roughly six weeks it lasts. Meanwhile, the beta cells cause new blood vessels to grow and supply them with nutrients and oxygen. By the time the implanted oxygen is used up, the beta cells are being adequately supplied by the body.
DRI proudly announced last week that the first patient to get this procedure was able to stop all insulin after only two weeks, record time for a transplant patient. Hopefully, this improvement will last and she will be cured.
But will it last, or will her immune system destroy the new cells, a complication called transplant rejection? Like almost all transplant recipients, she is currently on immune-suppressing drugs to prevent rejection, which may work but which also have many side effects and risks. DRI’s goal is to create a BioHub that will not need immunosuppressants, but they haven’t achieved this yet.
One thought is that they may deliver very-low-dose immune-suppressing drugs directly into the pouch, thus avoiding the side effects of taking the drugs by mouth or IV. Another idea is to find a way to “coat” the islet cells with protection from immune attack without blocking their insulin production. DRI is working on both of these tracks, but for now, they still use the immune-suppressing drugs.
Even if this BioHub or a later version affects a cure or near-cure of diabetes, it won’t be available to many people, unless the supply problem is solved. Where do we get these donor cells? So far, they are coming from dead donors. They can’t come from live donors because the process of getting them out of the pancreas would damage or kill the donor.
A recipient needs millions of islets for a successful transplant. It usually takes two donor pancreases to get enough beta cells for one transplant. That’s a major hurdle for the BioHub.
It is hoped that stem cells can replace donor cells at some point, but not yet. DRI and many other centers are working on turning stem cells into beta cells. They’re looking at stem cells from embryos, from bone marrow, and other sources.
It’s all exciting; it’s great, but unless you can get into a transplantation study, it’s pretty far away.
Part of Scott Coulter hates going to the doctor, and it’s not for the reasons you would think. Bookmark DiabetesSelfManagement.com and tune in tomorrow to learn what approaches he uses to deal with this all-too-common situation.
