TUNEL staining in liver tissues

The liver tissues were post-fixed in 4% paraformaldehyde for 2 days. A sequential 20% to 30% sucrose treatment was performed for 1 day; then, the intestinal samples were cryosectioned (10 μm thickness), and the samples were sliced. Cell apoptosis in the intestines was evaluated by TUNEL staining using an In Situ Cell Death Detection Kit (Roche, Shanghai, China) according to the manufacturer’s protocol. A Leica DM 4000B microscope or Leica TCS SP5 microscope was used to examine staining via conventional or confocal imaging, respectively. TUNEL quantification was made by counting the TUNEL-positive cells using five random fields at 400× magnification.