Glucose metabolism in vitro of cultured and transplanted mouse pancreatic islets microencapsulated by means of a high-voltage electrostatic field

The aim of this study was ro assess the function of mouse pancreatic islets microencapsulated using a high-voltage electrostatic field. Islets were mi croencapsulated in alginate/poly-L-lysine/alginate (APA) capsules and maint ained in tissue culture. Rates of glucose oxidation and insulin release wer e then assessed. Glucose metabolism was also measured in microencapsulated islets retrieved after transplantation to normal syngeneic mice. The high-v oltage electrostatic system made possible the production of uniformly sized microcapsules, which were smaller than those produced by co-axial air-jet systems, Nonencapsulated islets were used as controls. Empty microcapsules or islet-containing microcapsules were transplanted intraperitoneally and r etrieved after 2 weeks for assessment of foreign-body reactions and glucose oxidation rates. After 1 day and 2 weeks in tissue culture, both control i slets and microencapsulated islets increased their rates of glucose oxidati on and insulin release 7- to 10-fold in response to an increase in glucose concentration from 1.7 to 16.7 mmol/l. Both empty and islet-containing micr ocapsules, retrieved 2 weeks after transplantation, showed high rates of gl ucose oxidation at both low and high glucose concentrations, suggesting ove rgrowth with metabolically active fibroblasts. Morphological studies indica ted a marked foreign-body reaction on the surface of all transplanted micro capsules. The islets in cultured microcapsules had a normal histological ap pearance, whereas the islets within transplanted microcapsules showed a ran ge of morphological appearances, from intact islets to cell debris. In conc lusion, this study shows that mouse pancreatic islets survive and remain fu nctionally competent for at least 2 weeks in vitro after microencapsulation in APA capsules generated in an electrostatic field. However, a foreign-bo dy reaction with cellular growth on the capsular surface was present after intraperitoneal syngeneic transplantation.