2.7 Determination of cellular apoptosis
For detection of cellular apoptosis, slices were stained with terminal deoxynucleotide transferase–mediated dUTP-biotin nick-end labeling (TUNEL) using an in situ cell apoptosis detection kit (Meilunbio, Dalian, China) [18]. Briefly, slices were incubated with TUNEL at 37 ◦C for 1 h, washed with PBS for three times and then mounted and observed with a fluorescence microscopy. Quantified analysis was performed with ImageJ software by independent investigators.