Fig. 2. Differentiation of pancreatic explants in culture. (A) Low magnification microscopy shows rounding of the explant, expansion and branching morphogenesis of the epithelium (e) and redistribution of the mesenchyme (m), for the same explant over the 7 days (d) in culture. (B) Hematoxylin and Eosin staining of sections shows that on day 0 the pancreas consists of epithelial precursors surrounded by mesenchymal cells, and that by day 7 epithelial cells have differentiated into ducts (d) and acini (a). The surrounding mesenchyme has invaded the epithelial structures. (C) Double immunostaining for the pancreatic epithelial cell marker Pdx-1 (green) and the proliferation marker Ki67 (red) in d1 (left) and d7 (right) pancreatic explants. Both epithelial cells and mesenchymal cells are proliferating on day 1 and on day 7. Scale bars, 500 µm for A, 100 µm for B and 50 µm for C.