The structural integrity of the islet in vitro: The effect of incubation temperature

The purpose of this study was to examine the effect of incubation temperature on the structural integrity of the islet during culture. Islets were isolated from the pancreas of the Syrian golden hamster and cultured in a collagen gel for less than or equal to 12 days at 24 degrees C or 37 degrees C. At 24 degrees C, cells in the islet periphery died, leading to a complete disintegration of the mantle region in 37.4 +/- 5.6% of the islets. In comparison, at 37 degrees C, few islets exhibited mantle disintegration (p < 0.001). Insulin immunoreactivity was distributed nonhomogeneously in islets at 24 degrees C, and the intensity of the staining, by using a semiquantitative scale (0-3), was +1. Islets cultured at 37 degrees C had a normal homogeneous distribution of insulin immunoreactivity with a score of +3. As the pancreas is a complex gland composed of different cell types, and cell-cell interactions are known to be important in the maintenance of cell survival, additional experiments were repeated to include the coculture of islets with duct epithelial cells. The proportion of islets that developed mantle disintegration was now reduced to 2.5 +/- 0.3% (p < 0.001), comparable to that seen at 37 degrees C. Similar results were obtained for islets cultured in the presence of duct-conditioned medium (DCM). Together with the preservation of the islet mantle, islets cultured in the presence of duct epithelial cells or DCM had a normal homogeneous distribution of insulin immunoreactivity, with a staining intensity of +3. We conclude that incubation temperature has a profound effect on the structural integrity of islets, and that the detrimental effects of low-temperature culture can be mitigated by coculture of islets with secretory products derived from pancreatic ductal cells. These data provide evidence for a trophic relation between pancreatic islets and ductal epithelium.