A major hurdle to islet transplantation is the risk of rejection due to normal immune system responses to foreign substances (besides the autoimmune process ongoing in people with T1D). Encapsulation of pancreatic islets using a device developed by the company TheraCyte has been shown to protect against implant rejection in normal animal recipients. However, the ability of this device to prevent rejection in sensitized animal recipients (simulating autoimmunity in T1D) has not yet been studied. In this study, the protective capacity of the TheraCyte encapsulation device was evaluated in a rat model using both normal rats and those with a sensitized immune system. Survival of non-encapsulated implanted cells was shorter in sensitized animals than in normal ones (5 days vs. 9 days, respectively). When islets were implanted in the TheraCyte encapsulation device, islet function was maintained during the six month study period in both normal and sensitized rats. In oral glucose tolerance tests performed at one month after implantation, both groups had similar insulin and blood glucose levels indicating similar metabolic functions. This study suggests that the TheraCyte encapsulation device successfully protects implanted islets in sensitized rats. These results further highlight the potential for using macroencapsulation to avoid immunosuppressive therapy in clinical islet implantation in people with T1D to restore their insulin independence.
Ramifications for Individuals with T1D:
TheraCyte has a device product that is being adapted by others interested in transplanting alternative beta cell source material for the treatment of T1D. In animal studies, it provides near normal response to blood glucose concentrations because of the unique vascularization properties of the encapsulation system. Long-term functionality is provided by the biocompatible and immune-protective membranes, which, in the case of diabetes, must protect against immune system rejection and autoimmune attack. The product is designed to be minimally invasive and easily retrieved towards the goal of making the therapy safer and more easily terminated, if necessary. Clinical trials with this products adapted from this design are projected to begin within two years.
This study was not funded by JDRF.
Investigators and Institutions:
This work was conducted by Dr. Tibell and her colleagues at the Karolinska Institute.
Kumagai-Braesch M, Jacobson S, Mori H, Jia X, Takahashi T, Wernerson A, Flodström-Tullberg M, Tibell A. (2012) The TheraCyte(TM) Device Protects against Islet Allograft Rejection in Immunized Hosts. Cell Transplant. 2012 Oct 3. [Epub ahead of print].