Expression of Polymerase I and transcript release factor (PTRF) in mouse kidney in each group. (a) PTRF immunohistochemical staining of mouse renal tissues in each group (×400). N1–N2 = Negative control group, A1–A2 = Control kidney. B1–B2 = MG53-treated kidney. Scale bar denotes 100 µm. (b) The mean optical density score for PTRF expression in each group. The score for control kidney was 313,110.9 ± 44,570.2. The score for MG53-treated kidney was 315,946.8 ± 35,043.3. There was no statistically significant difference in mean optical density score between the groups (P = 0.890).