Microencapsulated Xenoislet Transplantation Into Retroperitoneal Space In Diabetic Mice For Diabetic Treatment

Objective:Using portal vein as the standard infusion method,the clinical effect of islet allotransplantation has been improved.However,the current implant location is not ideal due to short-term thrombosis and long-term immune disruption.Meanwhile,the shortage of human organ donors further limits its use.To find a new strategy,we tested a novel polymer combination for islet encapsulation and transplantation.At the same time,we explored a new site for mouse xenoislet transplantation.Methods:(1)Isolation,purification and microencapsulation of pancreatic islets of rats,neonatal porcines and human: the pancreas was digested with collagenase P and collagenase V,purified by centrifugation with 1.1 Lympholyte density gradient,and then it was coated with hydrogel combined with alginate and poly-ethylene-imine(Alg/PEI);(2)Islet transplantation: Type 1 diabetes mellitus(T1DM)was induced in 8-week-old male C57BL/6J mice by STZ.Free islets were transplanted into the renal capsule as control group(renal capsule control group),encapsulated islets were transplanted into the peritoneum as control group(peritoneum control group),and encapsulated islets were transplanted into the retroperitoneal space as experimental group(experimental group).(3)Biochemical indicators were determined after transplantation,including blood glucose level,glucose tolerance,C-peptide level,and immunohistochemical staining of insulin and glucagon after harvesting the transplanted islets.In addition,the macrophages were analyzed by tissue staining.Results:Mice receiving encapsulated rat,neonatal porcine,and human islets transplanted into the retroperitoneal space maintained normal blood glucose for a median of 275,145.5,and 146 days,respectively.In contrast,encapsulated xenoislets transplanted into the peritoneum maintained function for a median of 61,95.5,and 82 days.In addition,xenoislets transplanted free into the renal capsule lost function within 3 days after transplantation.Immunohistochemical staining of wrapped rat,neonatal porcine,and human islets from retroperitoneal space transplantation sites showed that the islets of the three groups of mice had normal morphology and high expression of insulin β cells and glucagon α cells at 70,60,and 100 days after transplantation,respectively.Conclusion:Transplantation of Alg/PEI encapsulated xenogeneic islets into the retroperitoneal space provides a valuable new implantation strategy for the treatment of type 1 diabetes.