Alginate Macroencapsulation of Pig Islets Allows Correction of Streptozotocin-Induced Diabetes in Primates up to 6 Months Without Immunosuppression

BACKGROUND.: This study assessed the capacity of alginate-encapsulated islets to reverse diabetes in a pig-to-primate model. METHODS.: Adult pig islets were encapsulated in microcapsules implanted under the kidney capsule (n=4) or in a subcutaneous macrodevice (n=5) in diabetic primates. Fasting blood glucose (FBG), insulin, porcine C-peptide, glycosylated hemoglobin (HbA1C), and cellular and humoral responses were followed. RESULTS.: Nonencapsulated pig islets were rejected within 7 days. A transient decrease of FBG was observed only during the 2 weeks after microencapsulated pig islet implantation under the kidney capsule. After subcutaneous transplantation of a macrodevice, diabetes was corrected up to a maximum of 6 months in five animals: FBG less than 107 mg/dL and HbA1C at 8%±1.4%. Two of the five animals received a new macrodevice between 25 and 35 weeks after the first graft dysfunction (HbA1C ≥13), and diabetes was controlled for an additional 18 weeks in these animals. Although a strong humoral response was elicited after transplantation of encapsulated islets, a total impermeability of alginate 3% wt/vol to IgG was demonstrated before and up to 20 weeks after transplantation of the subcutaneous macrodevice. CONCLUSIONS.: Pig islets encapsulated in a subcutaneous macrodevice can control diabetes up to 6 months without immunosuppression.