An Isolated Venous Sac as a Novel Site for Cell Therapy in Diabetes Mellitus

Background. Transplanting pancreatic islets is of significant interest for type 1 diabetes mellitus. After intraportal injection of islets, inferior engraftment and eventual loss of transplanted islets constitute major limitations. Therefore, alternative approaches will be helpful. Here, we evaluated in animals whether an isolated venous sac would support survival of transplanted islets, along with correction of hyperglycemia. Methods. Pancreatic islets isolated from adult Lewis rats were transplanted either into an isolated venous sac made from lumbar vein or into the portal vein of syngeneic rats. The integrity and vascular organization of the venous sac was determined by studies of the local microcirculation. The engraftment, survival, and function of transplanted islets were analyzed by histology, including endocrine function in situ and by glycemic control in rats with streptozotocin-induced diabetes. Results. Transplanted islets showed normal morphology with insulin expression in isolated venous sac during the long term. Transplanted islets received blood supply from vasa vasorum and had access to drainage through venous tributaries in the venous sac. This resulted in restoration of euglycemia in diabetic rats. Removal of islet graft-bearing venous sac in diabetic rats led to recurrence of hyperglycemia. By contrast, euglycemia was not restored in rats treated by intraportal transplantation of islets. Conclusions. We demonstrated that pancreatic islets successfully engrafted and functioned in the isolated venous sac with ability to restore euglycemia in diabetic rats. Therefore, the isolated venous sac offers a new site for transplantation of pancreatic islets. This would be clinically beneficial as an alternative to intrahepatic islet transplantation.