Microencapsulated Xenogeneic Pancreatic Islets In The Treatment Of Type 1 Diabetes Mellitus

Objective:Islet microencapsulation can reduce the immunogenicity of xenografted islet,and at the same time help the xenotransplant islet protect against or reduce the attack of recipient cells,which is a method for the treatment of type 1 diabetes.Therefore,this study investigated whether the microencapsulation of rat islet with Alg/PEI and transplanted into the intraperitoneal of type 1 diabetic mice,and whether the microencapsulated islets can control blood glucose,maintain the islets response to glucose and produce insulin without immunosuppressive therapy.Methods:（1）Isolation and microencapsulation of rat pancreatic islets: The islets of 2-monthold male SD rats were isolated and purified by collagenase P perfusion digestion and three discontinuous density gradient purification liquids（Ficoll-400,Histopaque-1077 and Lympholyte-1.1）.400 IEQ rat islets were isolated and microencapsulated with sodium alginate（Alg）and polyethyleneimine（PEI）.（2）Islet transplantation: Type 1 diabetes mellitus（T1DM）model was induced by STZ in 2-month-old male C57BL/6J mice.The non-microencapsulated islets were moved to the renal capsule of mice as control group（renal capsule control group）,the non-microencapsulated islets were moved to the intraperitoneal of mice as control group（intraperitoneal control group）,and the microcapsules were transplanted into the intraperitoneal of mice as experimental group（intraperitoneal experimental group）.（3）Blood glucose and body weight monitoring after islet transplantation: Blood glucose and body weight of mice were measured before and after modeling.Random blood glucose was measured daily at 1 week after transplantation and twice a week thereafter.（4）Intravenous glucose tolerance test（IVGTT）after islet transplantation: In the 5th and 14 th day after transplantation,IVGTT experiments were performed on mice in three groups.Blood glucose was measured and plotted at 0,5,15,30,60,90 and 120 min after glucose injection,and the curve was drawn.（5）HE and immunofluorescence staining after islet transplantation: In the 3rd and 14 th day after transplantation,the transplanted microcapsules and the transplanted kidney were collected for HE and immunofluorescence staining.HE staining was used to observe the morphology of islets after transplantation,and immunofluorescence staining was performed with insulin and glucagon to evaluate the function and survival of islets.Results:（1）Islet purification solution: By comparing the three purification solutions,Lympholyte-1.1 was selected as the purification solution for the subsequent purification of islets.（2）Blood glucose changes: After transplantation,the blood glucose of the mice in the three groups decreased to varying degrees.The blood glucose of the experimental group was maintained at about 200 mg/d L 60 days after transplantation.The blood glucose of the mice in the renal capsule control group and the intraperitoneal control group gradually recovered after 2 to 3 days of transplantation,and there were statistical differences between the experimental group and the experimental group at 2 and 4 days after transplantation,respectively.（3）IVGTT experiment: In the 5th and 14 th day after transplantation,the blood glucose of the experimental group decreased below 200 mg/d L90 minutes after the glucose injection,while the blood glucose of the renal capsule control group and the intraperitoneal control group remained high,showing a high glucose tolerance curve.（4）HE and immunostaining results: 3rd day after transplantation,both the experimental group and the renal capsule control group had less damage and the islet mass was relatively complete,indicating that the islets in both groups had better functions3 rd day after transplantation.14 th day after transplantation,the intraperitoneal experimental group could secrete insulin and glucagon better and the islet mass was more intact,while the renal capsule control group secreted less insulin and the islet mass was more fragmented.Conclusion:In the absence of immunosuppressive agents,Alg/PEI microencapsulated islets can effectively reverse the hyperglycemia state,better maintain the sensitivity of xenogeneic islets to glucose,and ensure the function of insulin secretion and release.