Increased cell proliferation within the ductal epithelium of Sst-Cre::Pax4-OE pancreata. (A–H) Immunofluorescence analyses were performed on pancreas sections of control (A–D) and Sst-Cre::Pax4-OE (E–H) mice. An increase in proliferation was observed solely within the ductal lining of 2-mo-old transgenics after a short-term 3-d IdU pulse (A and E). Chasing the label for another 7 d resulted in a massive increase of IdU⁺ cell counts within the endocrine compartment of 2-mo-old Sst-Cre::Pax4-OE pancreata (B and F). After 10 d of IdU treatment, a further increase in proliferating cells was noted in the ductal epithelium (inset in G) and islets (H) of transgenic mice as compared with controls (C and D). (I) Quantitative analyses revealed a 5.73 ± 0.38-fold increase in proliferating cell counts within the ductal lining or epithelium after short-term IdU treatment. Interestingly, chasing the label for 7 d resulted in a 3.93 ± 0.41-fold increase in IdU⁺ cells within the endocrine compartment of 2-mo old Sst-Cre::Pax4-OE pancreata (I). After a long-term IdU treatment (10 d), a 2.47 ± 0.29-fold and a 3.34 ± 0.79-fold increase in IdU⁺ cells is outlined in the endocrine compartment and ductal lining, respectively, of Sst-Cre::Pax4-OE pancreata (I). For the purpose of clarity, in selected photographs, islets are outlined with dashed white lines. All values are depicted as mean ± SEM of a minimum of n = 4 independent animals. Statistical analyses were performed with the Mann–Whitney test or unpaired t test with Welch’s correction. ****, P < 0.0001; **, P < 0.01; ns, P > 0.05. Error bars indicate SEM. Bars: 50 µm; (insets) 20 µm. DBA, dolichos biflorus agglutinin; INS, insulin.