Insulin Secretion and DNA Synthesis of Cultured Islets of Langerhans Are Influenced by the Matrix

Abstract

To compare the effect of matrix on glucose-stimulated insulin release, we cultured neonatal (3- to 5-day-old) rat islets of Langerhans, devoid of mesenchyma1 cells, on fibronectin, Cell-Tak, or endothelial basement membranes, free-floating, or dispersed into single cells. We also examined the rate of DNA synthesis during the culture period. Compared to free-floating islets [0.386 ± 0.03 (SEM) ng per 24 h/ng total], single-cell cultures had the lowest basal insulin release (0.159 ± 0.03 ng per 24 h/ng total; p < 0.0001), which was also low in islets attached to endothelial basement membrane (0.294 ± 0.02 ng per 24 h/ng total; p = 0.01). The spontaneous insulin release (1 h in medium with 2.7 mM glucose) was lowest in islets attached to endothelial basement membrane (0.003 ± 0.00023 ng per h/ng total; p < 0.0001 vs. free-floating) and highest in single-cell cultures (0.01153 ± 0.00259 ng per h/ng total; p = 0.039 vs. free-floating). The ability to increase insulin release following a glucose challenge (16.1 mM for 1 h) was highest in islets grown on endothelial basement membranes (16.4-fold) and fibronectin (12.6-fold) compared to free-floating islets (8.7-fold), Cell-Tak (7.9-fold), and single-cell cultures (5.4-fold). After 6 days in culture, the DNA synthesis rate in islets grown on fibronectin (27,808 ± 1,318 cpm/μg DNA), Cell-Tak (23,858 ± 2,114 cpm/μg DNA), or free-floating (23,576 ± 3,013 cpm/μg DNA) was significantly higher than in islets grown on endothelial basement membranes (15,929 ± 566 cpm/μg DNA; p = 0.0032) or in single-islet cell cultures (9,010 ± 625 cpm/μg DNA; p < 0.00001). The basal (24-h) insulin release correlated with the DNA synthesis rate under the different culture conditions. We conclude that adhesion to matrix influences the function of cultured islets of Langerhans and may be important for devising new culture techniques for islet transplantation.