Detection of pancreatic islet regeneration after IL-22 treatment. Immunofluorescence localization of nuclear EdU and cytoplasmic insulin within pancreatic islets was done in 5 to 6-week-old NOD mice. Islets were treated with either DMEM media alone (A) or 10 ng/mL of recombinant IL-22 for 48 hrs (B) (red = EdU; green = insulin; blue = DAPI). Examples of dual-labeled cells are shown with arrows. The size bar = 50 μm. (C) The mean percentage ± SEM of β-cells immunopositive for both EdU and insulin relative to insulin alone. Results were taken from 26 control islets and 46 IL-22-treated islets derived from 4 animals for each group. The asterisk (*) denotes a significant difference from the control (P<0.001). As described in the Methods section, in parallel experiments we explored the nuclear expression of Ki/67 as a measure of islet cell proliferation (data not shown). This further confirmed the proliferation of islet cells by IL-22 treatment.