Functional enhancement of electrofusion-derived BRIN-BD11 insulin-secreting cells after implantation into diabetic mice

Electrofusion-derived BRIN-BD11 cells are glucose-sensitive insulin-secreting cells which provide an archetypal bioengineered surrogate β-cell for insulin replacement therapy in diabetes mellitus. 5×10⁶ BRIN-BD11 cells were implanted intraperitoneally into severely hyperglycaemic (>24mmol/l) streptozotocin-induced insulin-treated diabetic athymic nude (nu/nu) mice. The implants reduced hyperglycaemia such that insulin injections were discontinued by 5-16 days (<17 mmol/l) and normoglycaemia (<9mmol/l) was achieved by 7-20 days. Implanted cells were removed after 28 days and re-established in culture. After re-culture for 20 days, glucose-stimulated (16.7 mmol/l) insulin release was enhanced by 121% (p<0.001) compared to non-implanted cells. Insulin responses to glucagon-like peptide-1 (10^-9mol/l), cholecystokinin-8 (10^-8 mol/l) and L-alanine (10mmol/l) were increased by 32%, 31% and 68% respectively (p<0.05-0.01). Insulin content of the cells was 148% greater at 20 days after re-culture than before implantation (p<0.001), but basal insulin release (at 5.6mmol/l glucose) was not changed. After re-culture for 40 days, insulin content declined to 68% of the content before implantation (p<0.01), although basal insulin release was unchanged. However, the insulin secretory responses to glucose, glucagon-like peptide-1, cholecystokinin-8 and L-alanine were decreased after 40 days of re-culture to 65%, 72%, 73% and 42% respectively of the values before implantation (p<0.05-0.01). The functional enhancement of electrofusion-derived surrogate β-cells that were re-cultured for 20 days after implantation and restoration of normoglycaemia indicates that the in vivo environment could greatly assist β-cell engineering approaches to therapy for diabetes.