Functional assessment of microencapsulated porcine islets with agarose polystyrene sulfonic acid in vitro and in xenotransplantation.

We evaluated the functional efficacy of microencapsulated porcine islet xenografts transplanted into nonobese diabetic (NOD) mice. Islets were isolated from the pancreata of CSK miniature swine by manual collagenase digestion and Ficoll purification. Purified porcine islets were immediately encapsulated into microbeads of agarose polystyrene sulfonic acid (Ag-PSSa). They remained morphologically intact by dithizone staining after 7 days in culture. Insulin secretion from encapsulated islets was determined in response to glucose challenge during perifusion. When encapsulated islets were exposed to 200 mg/dL glucose, within 5 minutes, insulin release became 5-fold greater than that at 80 mg/dL. However, a second phase insulin secretion appeared in response to 250 mg/dL glucose challenge. In xenotransplantation, microencapsulated porcine islets (1000 to 1800 MC islets) were transplanted into the peritoneal cavity of diabetic NOD mice (n = 4) without immunosuppression. The survival times after the onset of diabetes were observed after both MC islets transplanted NOD mice and nontransplanted NOD mice (n = 4). MC islets transplant recipients had significantly (P < .05) longer survival (47.5 +/- 18.6; mean +/- SD) than nontransplanted NOD mice (21.0 +/- 9.31), although random blood glucose levels were not normalized.