Pancreatic islet transplantation into the bone marrow of the rat

Background The liver is the current site for pancreatic islet transplantation, but presents important technical complications and limitations. We asked whether pancreatic islets could be engrafted in the bone marrow, an easily accessible and widely distributed transplant site that may lack the limitations seen in the liver. Methods We implanted pancreatic islet isografts (Lewis islets to Lewis rats), allografts (Wistar Furth islets to Sprague Dawley rats), and xenografts (Tilapia islets to Sprague Dawley rats) into the bone marrow of nondiabetic recipients and assessed survival by histology and immunocytochemistry. No immunosuppression was used. Results Isografts and allografts showed positive staining for insulin and glucagon and no evidence of allograft rejection up to 21 days posttransplant. Xenografts were acutely rejected. Conclusions The bone marrow may be an attractive alternative site for pancreatic islet transplantation. The acceptance of allografts and isografts but rejection of xenografts suggests a selective phenomenon for the inflammatory process.