Fig. 3

Fractionated pelvic irradiation impairs rectal epithelial regeneration. a Schematic representation of the fractionated pelvic irradiation timeline. b Representative Brdu immunohistochemistry of mice rectum section. Note the decrease in Brdu-positive cells (stained brown, indicated with arrow) in irradiated cohort. c Histogram showing mean Brdu-positive cells per crypt. Fractionated pelvic irradiation significantly reduces Brdu-positive cells compared to un-irradiated control (p < 0.0007, Mann-Whitney test). d Representative TUNEL staining of mice rectum section. Note the increase in TUNEL-positive cells (stained red, indicated with arrow) in irradiated cohort. e Histogram showing mean TUNEL-positive cells per crypt. Fractionated pelvic irradiation significantly increased TUNEL-positive cells compared to un-irradiated control (p < 0.004, Mann-Whitney test). f Schematic representation of the fractionated pelvic irradiation and tamoxifen treatment timeline. g Confocal microscopic images of the rectum section from Lgr5-eGFP-IRES-CreERT2; Rosa26-CAG-tdTomato mice. tdTomato (tdT)-positive cells are shown in red; Lgr5+ GFP+ cells are shown in green. Nuclei are stained with DAPI (blue). Marked expansion of tdT-positive red cells representing transit amplifying cells (regenerative cells) in crypt were noted with un-irradiated rectal tissue compared to mice exposed to pelvic irradiation. h The number of regenerative cells reduced significantly in irradiated mice rectum compared to un-irradiated mice (p < 0.0381, Mann-Whitney test)