Study On The Immunoisolating Effects Of Barium-alginate Microencapsulation On Rat Islets Allograft Survival

Objective To develop a reliable method for isolating , purifying and encapsulating rat pancreatic islets, and observe the characteristics of the purified and microencapsulated islets in vitro and in vivo, and the immunoisolating effect of barium-alginate microencapsulation on islets allograft survival.Methods The Sprague Dawley rat pancreas was digested in situ by the injection of collagnase solution into the pancreatic duct and was purified by Ficoll-400 discontinuous density gradient or filtration through cell strainer. A simple droplet generator was used for encapsulation of the rat pancreatic islets with the purified alginate crosslinked with BaCl2. The naked islets and microencapsulated islets were transplanted under the kidney capsule or intraperitoneally into Wistar rats with STZ-induced diabetes. The blood glucose and insulin secretion of grafts were observed. The funtion of lymphocyte proliferation was measured by means of lymphocyte-islet co-culture, and expressed by stimulating index (SI) . IL-2 and IFN- Y were determined by ELISA.Results (l)The crude islet yields were 1024 156 per pancreas. After purified by filtration, the islet yields were 867 104 per pancreas. (2) In response to glucose sitmulation from 3.3 mmol/L to 16.7 mmol/L, there was no difference of insulin release between microencapsulated-and unencapsulated-islets (P<0.001). Five diabetic rats became euglycemic 48h to 72h after transplantation. The survival time of transplanted islets was about 6W. (3) The stimulating index ofmicroencapsulated islets allogeneic transplantation was similar to those in normal controls (P>0.05), while SI and IL-2, IFN- levels of naked islets allogeneic group were significantly higher than those in microencapsulated islets group (P<0.05).Conclusions (1) We developed a simple and effective procedure for islet isolation and purification with high output and functional intergrity of islets. (2) The purified barium-alginate microencapsules have good biological function and biocompatibility. (3) Microencapsulation with barium-alginate membrane can prolong islet survival and protect islets against allorejection.