Small islets are essential for successful intraportal transplantation in a diabetes mouse model.

Optimization of islet transplantation protocols is necessary for improved success of treatment for type 1 diabetes. Here, we investigated whether the size of islets transplanted into the portal vein (PV) of the liver can affect engraftment in the early post-transplantation in an experimental mouse model. Small (average diameter < 250 μm, group A) or large (average diameter > 250 μm, group B) islets (400 islet equivalents/recipient) purified from normal BALB/c mice were transplanted into syngenic recipients with diabetes induced by STZ. The percentage of mice returning to a non-diabetic status was higher in group A (100%) than that of group B (62.5%). Focal areas of liver necrosis associated with the islets emboli were observed in both groups, but the pathology in group B was significantly worse. Multiple proinflammatory cytokines were significantly higher in group B than that of A at 3 h post-transplantation. Our study determined that the size of islets plays a critical role in the success of intraportal islet transplantation (IPIT) and should be taken into account in future IPIT protocols for the treatment of diabetes.