Hypoxic resistance of hypodermically transplanted pancreatic islets by using cell-absorbable antioxidant Tat-metallothionein

Abstract

Subcutaneous site is ideal for clinical islet transplantation because it has the advantage of simple operation procedure under local anesthesia and can be biopsied when needed. However, the transplantation outcomes at subcutaneous site have been disappointing due to hypoxia-induced oxidative stress by poor vascularization. We hypothesized that subcutaneously transplanted islets would have hypoxia resistance by using internalization of metallothionein (MT), an antioxidant scavenging enzyme, which was mediated by fusion between MT and cell penetrating Tat peptide. The Tat-MT was close-dependently transclucecl into islets without any damage. Tat-MT- treated islets could be protected from oxidative stress induced by intracellular nitric oxide donor, sodium nitroprusside (SNP). When Tat-MT-treated islets were subcutaneously transplanted into diabetic nude mice, they normally controlled the blood glucose levels without severe fluctuation (median survival time (MST): >30 clays), whereas most untreated islets were rejected (MST 17 clays). From the intraperitoneal glucose tolerance test 5 clays after posttransplantation, glucose responsiveness of Tat-MT-treated islets was similar to that of normal healthy mice, while untreated islets had delayed glucose responsiveness. From the results of immunohistochemical stain, Tat-MT-treated islets had strong anti-insulin positive cells and lower anti-HIF-l alpha positive cells. However, untreated islets had rare anti-insulin positive cells and strong anti-HIF-l alpha-positive cells. Collectively, these findings demonstrated that Tat-MT delivery into islet could offer a new strategy for successful islet transplantation under subcutaneous space.