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 to assess the function of mouse pancreatic islets microencapsulated using a high-voltage electrostatic field. Islets were microencapsulated in alginate/poly-L-lysine/alginate (APA) capsules and maintained in tissue culture. Rates of glucose oxidation and insulin release were then assessed. Glucose metabolism was also measured in microencapsulated islets retrieved after transplantation to normal syngeneic mice. The high-voltage 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 retrieved after 2 weeks for assessment of foreign-body reactions and glucose oxidation rates. After 1 day and 2 weeks in tissue culture, both control islets and microencapsulated islets increased their rates of glucose oxidation 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 microcapsules, retrieved 2 weeks after transplantation, showed high rates of glucose oxidation at both low and high glucose concentrations, suggesting overgrowth with metabolically active fibroblasts. Morphological studies indicated a marked foreign-body reaction on the surface of all transplanted microcapsules. The islets in cultured microcapsules had a normal histological appearance, whereas the islets within transplanted microcapsules showed a range of morphological appearances, from intact islets to cell debris. In conclusion, this study shows that mouse pancreatic islets survive and remain functionally competent for at least 2 weeks in vitro after microencapsulation in APA capsules generated in an electrostatic field. However, a foreign-body reaction with cellular growth on the capsular surface was present after intraperitoneal syngeneic transplantation.