INSULIN-SECRETION AND DNA-SYNTHESIS OF CULTURED ISLETS OF LANGERHANS ARE INFLUENCED BY THE MATRIX

To compare the effect of matrix on glucose-stimulated insulin release, we cultured neonatal (3- to 5-day-old) rat islets of Langerhans, devo id of mesenchymal cells, on fibronectin, Cell-Tak, or endothelial base ment membranes, free-floating, or dispersed into single cells. We also examined the rate of DNA synthesis during the culture period. Compare d 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 a ttached to endothelial basement membrane (0.294 +/- 0.02 ng per 24 h/n g total; p = 0.01). The spontaneous insulin release (1 h in medium wit h 2.7 mM glucose) was lowest in islets attached to endothelial basemen t membrane (0.003 +/- 0.00023 ng per h/ng total; p < 0.0001 vs. free-f loating) and highest in single-cell cultures (0.01153 +/- 0.00259 ng p er h/ng total; p = 0.039 vs. free-floating). The ability to increase i nsulin release following a glucose challenge (16.1 mM for 1 h) was hig hest 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/mu g DNA), Cell-Tak (23,858 +/- 2,114 cpm/mu g DNA) , or free-floating (23,576 +/- 3,013 cpm/mu g DNA) was significantly h igher than in islets grown on endothelial basement membranes (15,929 /- 566 cpm/mu g DNA; p = 0.0032) or in single-islet cell cultures (9,0 10 +/- 625 cpm/mu g DNA; p < 0.00001). The basal (24-h) insulin releas e correlated with the DNA synthesis rate under the different culture c onditions. We conclude that adhesion to matrix influences the function of cultured islets of Langerhans and may be important for devising ne w culture techniques for islet transplantation.