Effects of hyperbaric oxygen on the expressions of vascular endothelial growth factor and connexin 43 in the rats with acute spinal cord injury

Objective To explore the mechanism of hyperbaric oxygen (HBO) in the enhancement of neurological function recovery in the rats following spinal cord injury, through the observation of the effects of HBO on the expressions of vascular endothelial growth factor (VEGF) and connexin 43 (CX43) in the injured spinal cord tissue. Methods One hundred and sixty healthy adult SD rats were randomly divided into 4 groups: the spinal cord injury group(or the SCI group), the SCI+ HBO group, the sham surgery group (or the control group) and the sham surgery + HBO group. In the SCI group, the spinal cord injury model was developed by using the modified Allen's method and MASCIS spinal cord injury impactor. For the SCI+ HBO group, the animals received HBO therapy following development of the SCI model. In the control group, the vertebral lamina in T10 was surgically opened, but without SCI. In the sham surgery + HBO group, the animals also received HBO therapy after laminotomy. The animals of the 4 groups were further subdivided at random into the 1d, 3d, 7d and 14d subgroups, each consisting of 10. The motor function of the hinder limb was evaluated by Basso Beattie Bresnahan (BBB) scores at different time points after injury. The injured tissue of the spinal cord was collected and then, the expressions of VEGF and CX43 were detected with immunohistochemistry. Results The BBB scores of the SCI and SCI+ HBO groups at various time points after injury were significantly lower than those of the sham surgery group and the sham surgery + HBO group (P<0.01). Seven and 14 days after surgery, the BBB scores of the SCI+ HBO group(7 d: 4.67±1.97, 14 d: 10.83±2.23) were significant higher than those of the SCI group (7 d: 1.83±0.75, 14 d: 6.67±2.16) (P<0.05). When compared with those of the sham surgery group and the sham surgery + HBO group, the expression levels of VEGF and CX43 in the spinal cord for the SCI group and the SCI+ HBO group were significantly increased at various time points (P<0.01). The expression of VEGF in the SCI+ HBO group (3 d: 81.16±10.37, 7 d: 96.00±8.50, 14 d: 84.67±8.39)was significantly higher than that of the SCI group(3 d: 71.68±8.45, 7 d: 81.92±9.63, 14 d: 73.30±7.96), and statistical significance could be noted, when comparisons were made between the 2 groups(P<0.05). The expression level of CX43 in the spinal cord of the SCI+ HBO group (3 d: 72.46±7.52, 7 d: 67.10±8.06) was significantly lower than that of the SCI group (3 d: 83.65±8.70, 7 d: 77.64±7.78), and statistical significance could be seen, when comparisons were made between them (P<0.05). However, the expression level of CX43 at d 14 after surgery in the spinal cord of the SCI+ HBO group (74.81±10.05) was significantly higher than that of the SCI group (66.74±8.30)(P<0.05). Conclusions HBO could obviously improve the neurological recovery of the hinder limb of the SCI rat, through enhancing the expression levels of VEGF and CX43 following injury of the spinal cord Key words: Hyperbaric oxygen; Spinal cord injury; Vascular endothelial growth factor; Connexin 43; Rats