Immunohistochemical staining of SDF-1 in each group. The proportion of positive cells was analyzed under a high magnification (×400) in the (A) IR3d, (B) HBO-PC3d, (C) IR5d, (D) HBO-PC5d and (E) SH groups. (F) SDF-1-positive cells in the IR and HBO-PC groups were significantly higher than those in the SH group (*P<0.05; **P<0.01). Compared with the same day IR groups, SDF-1-positive cells were significantly increased in the HBO-PC groups (##P<0.01). IR, ischemia reperfusion; HBO-PC, hyperbaric oxygen preconditioning; SH, sham-operated.