Xenotransplantation of islets enclosed in agarose microcapsule carrying soluble complement receptor 1

Strong immunological reactions remain a major barrier to treating diabetic patients using xenogeneic islets. In a previous study, we developed a method for enclosing islets with agarose microbeads carrying soluble complement receptor 1 (sCR1-Mics), a potent complement inhibitor in both classical and alternative complement activation pathways. This is the follow-up in vivo study to evaluate the protective effect of these sCR1-Mics using a xenotransplantation model (rats to mice). ACI/NSIc rat islets enclosed in sCR1-Mics were transplanted into the intraperitoneal cavity of diabetic C57BL/6 mice without immunosuppression therapy. Transplantation of islets in plain agarose microbeads (Mics) was used as a reference. While islets enclosed in plain Mics were rapidly destroyed (graft survival in recipients of 1000 islets: 11.6 ± 3.8 days), transplantation of islets in sCR1-Mics significantly prolonged graft survival (34.1 ± 3.2 days). Moreover, intraperitoneal glucose tolerance tests revealed that islets in sCR1-Mics normalized blood glucose levels in a similar manner as islets in pancreas of normal mice. In conclusion, sCR1 immobilized onto agarose microbeads exerted some protective effect in xenogeneic islets resulting in prolonged graft survival.