Layer-by-layer building up of heparin and glycol chitosan for rat pancreatic islet xenotransplantation to mouse

Abstract

Immunoprotective strategies are being developed to improve the graft survival rate of islets. Heparin,which has been widely used due to its anti-coagulant and anti-inflammatory effects, holds great promise for use in preventing blood coagulation and related immune reactions. In this study, the layer-by-layer modification of islets using heparin and glycol chitosan as an immunoprotective remedy was examined in xenogeneic islet transplantation.The surface coverage of heparin and glycol chitosan was evaluated in vitro. The viability and functionality of layerby-layer modified islets was evaluated using the CCK-8 assay and glucose-stimulated insulin secretion (GSIS) test,respectively. In addition, the effect of layer-by-layer on immunoprotection for transplanted islets was evaluated in a diabetic mouse model. Layer-by-layer modified islets were evenly covered with heparin and glycol chitosan. The viability of islets was not affected by the modification procedures up to the third layer modification. In addition, unmodified and layer-by-layer modified (three layers) islets transplanted into the recipients maintained a normal level of blood glucose for 9.0±0.6 and 9.0±0.5 days, respectively. However, when the recipients were administrated with FK506and CTLA4-Ig, the median survival time of the unmodified and layer-by-layer modified islets (three layers) were 17±1.2 and 23.0±1.3 days, respectively. These results demonstrated that the combination of FK506 and CTLA4-Ig along with layer-by-layer modification using heparin and glycol chitosan showed highly improved synergic effects on the inhibition of inflammation and immune reactions