Biocompatibility and function of microencapsulated pancreatic islets.

Area of Science:

• Biomaterials Science
• Transplantation Immunology
• Endocrinology

Background:

• Alginate encapsulation is a strategy to mitigate xenogenic rejection of pancreatic islets.
• Optimizing alginate composition and immunosuppression is crucial for successful islet xenotransplantation.

Purpose of the Study:

• To investigate the impact of alginate composition and transient immunosuppression on bovine islet xenotransplantation in rats.
• To evaluate the efficacy of different alginate formulations and cyclosporin A (CyA) in prolonging islet graft function.

Main Methods:

• Bovine islets were encapsulated in Manugel or ultrapure low viscosity guluronic acid alginate (UP-LVG).
• Microcapsules were transplanted into diabetic rats, with some receiving transient cyclosporin A (CyA) therapy.
• Capsule integrity and fibrotic overgrowth were assessed post-transplantation.

Main Results:

• Unmodified encapsulation provided short-term normoglycemia (7-12 days).
• Transient CyA treatment significantly extended normoglycemia (18-55 days) and reduced fibrotic overgrowth, particularly with Manugel alginate.
• Capsular overgrowth was not solely dependent on the presence of xenogenic islet tissue.

Conclusions:

• A combination of highly purified alginate (Manugel) and short-term immunosuppression effectively prolongs islet graft function in a rat model of bovine islet xenotransplantation.
• This approach offers a promising strategy for improving outcomes in islet xenotransplantation.