Figure 3

Small β cell clusters are the preferred site of β cell (re)division in PDL pancreas. Eight-week-old male Balb-c mice underwent PDL surgery and were continuously labeled with thymidine analogs via the drinking water. Proliferation was analyzed by immunofluorescence staining for either IdU or IdU and CldU in insulin⁺ cells. Small clusters were defined as clusters of 1–20 β cells on cross-section while large clusters contained 21–200 β cells. Data are expressed as mean±S.E.M. of the percentage of β cells that were positive for thymidine analog in each size category. (a) Seven days IdU-labeling of β cells in PDL tail (n=5, **P<0.005), (b) 14 days IdU-labeling of β cells in PDL head and tail (n=4–7, *P<0.02, ns: P>0.05). (c) Thirty-five days of IdU-labeling of β cells in the PDL tail (n=3, **P<0.01). (d) Data from (c) analyzed for subcategories of clusters, and expressed as the percentage of clusters consisting of only analog⁺ β cells. Clusters comprising >60 insulin⁺ cells never consisted entirely of analog⁺ β cells. (n=3, **P<0.01 by one-way Anova) (e) 7 days CldU labeling followed by 28 days IdU labeling and evaluation of the percentage of CldU⁺IdU⁺ labeled (redivided) β cells according to cluster size (n=3, **P<0.01 by one-way Anova). (f) 8 h IdU pulse labeling of β cells in small and large clusters of PDL and Sham tail pancreas (n=3; *P<0.05, **P<0.01 versus same time point for Sham tail, by 2-way Anova). See also Supplementary Figure S4B