Xenotransplantation of pig islets in diabetic dogs with use of a microcapsule composed of agarose and polystyrene sulfonic acid mixed gel.

INTRODUCTION: The authors have designed a microcapsule composed of agarose and polystyrene sulfonic acid (PSSa) mixed gel that provides a protective barrier against complement attack. Xenografts of islets, encapsulated in an agarose-PSSa microcapsule, have been shown to normalize blood glucose in rodents with chemically induced diabetes for extended periods of time without immunosuppression. AIM: To investigate the efficacy of agarose-PSSa microencapsulated pig islets in reversing diabetes in a large animal model.
METHODOLOGY: Diabetes was induced in beagle recipients by total pancreatectomy. Each recipient received three to five intraperitoneal injections of either encapsulated (n = 5) or nonencapsulated pig islets (n = 2).
RESULTS: In all dogs receiving microencapsulated islets, the graft function was achieved for 7.4 +/- 3.1 weeks (mean +/- standard error), as determined by elimination or reduction of exogenous insulin requirement. In three recipients, the fasting blood glucose levels were maintained at < or = 200 mg/dL without any exogenous insulin for a period of 6, 50, and 119 days. Circulating porcine C-peptide was detected in the sera of all dogs after transplantation of encapsulated islets. Immunohistologic examination revealed the presence of insulin-positive cells in the microcapsules. In contrast, in two dogs receiving nonencapsulated islets there was no graft function.
CONCLUSIONS: This preliminary study demonstrates that agarose-PSSa microencapsulated pig islets can survive and function for weeks or months in totally pancreatectomized diabetic dogs without immunosuppression.