Optimizing encapsulation to treat Type 1 diabetes mellitus: the role of oxygenation, antigen shedding and innate immune response in graft success

项目总结

PROJECT SUMMARY The past fifty years have seen substantial advances in the field of encapsulation of insulin producing tissues for the treatment of Type 1 Diabetes Mellitus. Persistent obstacles and limitations of the current technologies have prevented translation of these results to the clinical realm. Multiple groups are now poised for clinical translation, but still lack adequate, easily retrievable delivery devices. One major obstacle is the limitation of tissue loading in conventional encapsulation that results from the high metabolic demand of native islets/SC-β and the concomitant mass transport limitations of most encapsulation materials. Importantly, native islets experience oxygen and nutrient deficit in loading densities greater than 1.5 to 2% v/v in standard alginate microcapsules. In smaller capsules of alternate materials, mass transfer is impaired due to monomer structure and cross-linking strategies. This adversely affects the benefit afforded by the smaller diffusive distance. Fundamental aspects of cell encapsulation must be reexamined. Research efforts have been focused on the in vivo application where reduction in device geometry is crucial to clinical success through the reduction of oxygen transfer distances and overall biomaterial/graft volume. There has been little study of pre-transplant culture where hypoxia and loss of viability/function are the result of cell proximity to the plastic basal surface. This causes cell death and results in antigen shedding. In vivo, the opposite holds true where larger geometry results in increased chance of hypoxia at clinically relevant loading densities. The central hypothesis of this proposal is that impaired oxygen mass transfer results in increased hypoxia/anoxia, loss of function, apoptosis and antigen shedding. This proposal seeks to address these obstacles through the following specific aims: 1.) we will determine the effect of capsule geometry and pre-implant culture methods on encapsulated islet/SC-β viability, function, antigen shedding and in-vitro inflammatory response from co-culture with macrophages. 2.) we will employ oxygen carrying perfluorocarbon nanoemulsions in islet encapsulation devices in immune-deficient, immune competent and autoimmune mouse models (BALB/C, C57BL/6, NOD-SCID, NOD) with chemical induction (STZ) of diabetes to ascertain the additive effect of each on engraftment and restoration of normoglycemia. !