In vitro formation of ß cell pseudoislets using islet-derived endothelial cells.

ABSTRACT

ß cell pseudoislets (PIs) are used for the in vitro study of ß-cells in a three-dimensional (3-D) configuration. Current methods of PI induction require unique culture conditions and extensive mechanical manipulations. Here we report a novel co-culture system consisting of high passage ß-cells and islet-derived endothelial cells (iECs) that results in a rapid and spontaneous formation of free-floating PIs. PI structures were formed as early as 72 h following co-culture setup and were preserved for more than 14 d. These PIs, composed solely of ß-cells, were similar in size to that of native islets and showed an increased percentage of proinsulin-positive cells, increased insulin gene expression in response to glucose stimulation, and restored glucose-stimulated insulin secretion when compared to ß-cells cultured as monolayers. Key extracellular matrix proteins that were absent in ß-cells cultured alone were deposited by iECs on PIs and were found in and around the PIs. iEC-induced PIs are a readily available tool for examining ß cell function in a native 3-D configuration and can be used for examining ß-cell/iEC interactions in vitro.