2.8. TUNEL Assay

TUNEL staining was detected using an One Step TUNEL Apoptosis Assay Kit (Beyotime, Shanghai, China), according to the manufacturer’s protocols. Briefly, after deparaffination and rehydration, paraffin sections were incubated with the TUNEL reaction mixture at 37 °C for 1 h. Then the sections were stained with DAPI and the images were obtained by using a fluorescence microscope (Carl Zeiss, Jena, Germany). TUNEL-positive cells were counted from a minimum of 10 fields and 80 intact crypts per mouse using Image J software.