Effect of Extracellular Matrix and 3D Morphogenesis on Islet Hormone Gene Expression by Ngn3-lnfected Mouse Pancreatic Ductal Epithelial Cells

We verified the proendocrine effects of Matrigel overlay in an adult mouse pancreatic ductal epithelial cells (PDEC) model and then decomposed the environment to delineate the specific factors responsible for this effect. Following overlay with Matrigel, supplementation of Matrigel to the culture medium, or suspension within Matrigel, neurogenin3-infected mouse PDEC underwent dramatic morphogenesis, transitioning from a two-dimensional monolayer to three-dimensional (3D) cysts. Along with these morphogenic changes, the cells displayed up to approximately sixfold increase in mRNA for the islet hormones somatostatin and ghrelin. Following overlay with collagen or suspension within collagen, PDEC also displayed similar morphogenic changes, but a much smaller increase in expression was observed (1.5- to 3-fold), suggesting that while 3D morphogenesis is capable of independently enhancing islet differentiation, biochemical factors present within Matrigel also have proendocrine effects. Following suspension within laminin gels, PDEC formed 3D cysts and also displayed an increase in islet hormone expression, similar to those cultured within Matrigel. However, medium supplemented with laminin failed to promote 3D morphogenesis of PDEC or enhance islet hormone expression, suggesting that while laminin is capable of enhancing islet hormone expression, 3D morphogenesis is required for this effect. Cell clustering appeared to maximize differentiation, as PDEC cultured on Matrigel formed aggregates and stimulated the highest expression of somatostatin and ghrelin (up to similar to 200-fold).