Long-term Functioning of Allogeneic Islets in Subcutaneous Tissue Pretreated With a Novel Cyclic Peptide Without Immunosuppressive Medication

Background There exists a need for a minimally invasive method of islet transplantation without immunosuppressive drugs for the treatment of type 1 diabetes. Methods In diabetic August Copenhagen Irish rats, an agarose rod containing the cyclic oligopeptide SEK-1005 (agarose-SEK rod) was implanted at 2 dorsal subcutaneous sites. Then these rods were removed, and 1500 islets of Langerhans isolated from Fischer 344 rats were transplanted into each of the pockets. Results Ten days after implantation of agarose-SEK rods, vascularized pockets were present. Nonfasting blood glucose levels confirmed long-term survival of the allogeneic islet grafts, without immunosuppressive therapy, in 8 of 10 recipients. Flow cytometry and gene expression analyses were performed to investigate the mechanisms underlying graft acceptance. Agarose-SEK rod implantation led to the formation of granulomatous tissue containing regulatory T cells that suppressed immune reactions against the allogeneic islet grafts. Conclusions These results indicate that the use of an agarose-SEK rod to prevascularize a subcutaneous site may be a useful method for achieving successful allogeneic islet transplantation without immunosuppression.