Figure 1

Hematoxylin and eosin-stained sections of normal mouse pancreas and after partial pancreatectomy. (A) Normal pancreas section showing the presence of acinar cells, ducts, blood vessels as well as islets. (B) Pancreas on day 3 post pancreatectomy showing prominent ‘hypertrophied’ islets, probably because they have to compensate for the islets lost due to pancreatectomy. (C) A prominent layer of coelomic epithelium (arrow) covers the pancreas post pancreatectomy. (D) On day 1 post surgery, most of the infiltrating leukocytes appear to be neutrophils with multilobed nuclei. (E), (F) A large number of cells migrate under the coelomic epithelium layer; newly formed lobes can be visualized clearly (arrow). (G) Higher magnification of newly formed pancreatic lobe covered by coelomic epithelium. Note newly formed acinar cells aligned below the coelomic epithelium. (H), (I) At higher magnification, acinar cells are clearly differentiating adjacent to coelomic epithelium and a few distinct spherical stem cells with minimal cytoplasm are also visualized. Two distinct sizes of stem cell are observed, including very small (asterisk) and slightly bigger (arrow) in size. (J) Small islets are clearly visualized in the newly forming pancreatic lobes. Presence of new islets in the regenerating region clearly suggests their neogenesis rather than re-duplication from surviving islets as per existing paradigm. Scale bar represents 20 μm.