Intraportal transplantation of allogenic pancreatic islets encapsulated in barium alginate beads in diabetic rats.

The survival of microencapsulated islets transplanted into the unmodified peritoneal cavity is limited, even if capsular overgrowth is restricted to a minimum, due to an insufficient oxygen supply to the islets. Therefore, research efforts should focus on finding or creating a transplantation site, which permits a closer contact between the encapsulated islets and the blood. For this reason, the liver could be an interesting candidate. The aim of the present study was to test the hypothesis that the intraportal transplantation of allogenic islets encapsulated in small-sized barium alginate beads is safe and succeeds to induce normoglycemia in diabetic rats. The intraportal transplantation of 1,500 islets encapsulated in barium alginate beads leads within 10 h and up to 24 h to blood sugar concentrations below 40 mg/dL, most likely due to an acute cell lysis of the graft. Afterwards, the reappearance of the diabetic state could be detected in these animals. Most likely these findings are induced by a sudden hypoxia to the islets. We believe that the occlusion of small- and medium-sized portal venules by the alginate beads is responsible for this effect. Therefore, in forthcoming studies, barium alginate beads, with a diameter below 350 micro m, stabilized with medical approved additives should be used.