Cell interactions during the in vitro neoformation of fetal rat pancreatic islets.

As shown by scanning electron microscopy, transmission electron microscopy and membrane labeling analysis, the in vitro neoformation of rat pancreatic islets arose from two main processes: a budding from explants containing duct cells, and a competition between endocrine monolayers and fibroblasts on the culture substratum. The stronger cytoskeleton of fibroblasts and their higher adhesive properties, probably related to their more homogeneous distribution of membrane charges, may explain the spherization of the islets. The pure endocrine cell population of neoformed islets was composed mainly of insulin-secreting cells, and the other types of endocrine cells were distributed in the periphery. Preformed extracellular matrices of osmotically disrupted fibroblasts enhanced the yield of the cultures by increasing the anchorage of endocrine cells and slowing down the fibroblastic growth.