Lots of organizations are working on new ways to accomplish islet cell transplantation in which the immune system does not kill off the transplanted cells. If they could do that, we’d likely have a cure for diabetes. But it ain’t easy, especially because we’re talking about transplanting into people whose immune systems are in mega-attack mode to begin with (type 1 diabetics).
The Diabetes Research Institute (DRI) in Florida is currently working on this challenge in an especially intriguing way. Borrowing a concept called “stealth tolerance” from cancer research, they’ve looked at areas in the body where the immune system seems to be less aggressive, i.e. an “immune safe” area. One of those happens to be male genitalia (ewww — dismissed!) The other happens to be inside the eye. The stealth approach does away with the need for the “cocktail of immuno-suppressants” that’s usually required, and that causes the patient’s body so much trouble.
The DRI’s researchers are using the anterior chamber of the eye as a spot to implant islet cells, derived from adult stem cells. So far they’ve 
found the transplants do indeed reduce the amount of insulin needed in animals. Of course they still need to “encapsulate” these cells to protect them when implanted.
“Encapsulation is not new, but the coating was too thick in the past,” DRI Chief Operating Officer, Dr. Mitra Zehtab, explained at a recent research update held at a private home in Northern California (just a few miles from my house!). “We’ve developed new ultra-thin material for encapsulation — it’s miniscule thinness — that coats the islets to protect them. It works like slow release capsules.”
Dr. Zehtab further explained that researchers are trying to put these coated capsules into small “biohybrid devices” like a tiny mesh cylinder that houses and protects transplanted cells. (See our previous coverage of these “reverse IUD devices” here.)
Because the eye affords a new, clear way to directly view and monitor how transplanted insulin-producing cells function after they’re infused into a patient, the approach is called the “Living Window.” DRI researcher Per-Olof Berggren also presented about progress on it at the ADA Conference last week. Th
Thanks for posting on my favorite topic. There are so many directions that islet cell transplantation research is moving. This direction offers both an alternative site for the islets and a means of learning more about their behavior in vivo.
I appreciate the work they do too! Fascinating!
Yes the eye model is currently an experimental tool, a highly versatile one that is, that is being used to investigate many aspects of islet physiology and immunobiology in vivo. We have been able to address many questions that could not be addressed using conventional in vitro studies.
While transplantation into the anterior chamber of the eye has provided us with great advantages over other transplantation sites by enabling longitudinal and non-invasive in vivo imaging of the very same individual pancreatic islets with cellular resolution, like other experimental transplantation sites the eye model will fall short of the real situation within the pancreas.
Nonetheless, while currently practiced in the clinic islet transplantation into the liver is still considered an experimental approach that has its limitations as well (e.g., IBMIR), which is the reason why many funding agencies including the NIH have had active funding opportunities to look for alternative sites….
With that said, the eye may offer a viable transplantation site in the future for a variety of reasons including: 1) easy access for implantation, 2) possible local immunosuppression and minimization/elimination of systemic side effects, 3) easy non-invasive observation/imaging of islets to assess islet function and follow up on islet mass, 4) immune privilege properties and possible tolerance induction (great advantage given the high interest in immune tolerance), 5) possibly less islet required for transplantation given the non-enzymatic environment.
Of course we still need to address many remaining issues regarding the eye model including possible effects on eye sight. As a first step in that direction, we have already moved these studies into non-human primates in Miami and we recently provided a proof-of-principle of the feasibility of islet transplantation into the eye of large mammals (see our study in Diabetologia 2011 May;54(5):1121-6. Epub 2011 Mar 1, http://www.ncbi.nlm.nih.gov/pubmed/21360190). We have also recently expanded these studies to South Korea where we hope to address many of the remaining issues before considering translation into the clinic.
I believe that I stated it clearly in the UTM interview by saying “We believe the eye may one day be used…” because this is what we believe and hope to achieve in the future.
Regards,
Midhat Abdulreda, M.S, Ph.D
Diabetes Research Institute (DRI)
University of Miami Miller School of Medicine