OBSTACLES IN THE APPLICATION OF MICROENCAPSULATION IN ISLET TRANSPLANTATION

Several factors stand in the way of successful clinical transplantatio n of alginate-polylysine-alginate microencapsulated pancreatic islets. These obstacles can be classified into three categories. The first re gards the technical aspects of the production process. Limiting factor s are the insufficient ability to produce small capsules with an adequ ate production rate, and insufficient insight into the factors determi ning the optimal chemical and mechanical properties of the capsules. T he second category regards the functional aspects of the microencapsul ated islets, such as the limitations of the transplantation site and t he absence of a physiologic insulin response of the encapsulated islet s to elevated blood glucose levels. The third category regards the fac t that survival times of encapsulated islet grafts are still limited t o several weeks or months, which is mainly explained by a pericapsular fibrotic overgrowth reaction as a consequence of the bioincompatibili ty of the capsule membrane. This study describes these obstacles, and thereby summarizes the requirements needed for successful clinical app lication of encapsulated islet transplantation.