Early hyperbaric oxygen therapy combined with methylprednisolone in the treatment of spinal cord injury associated with seawater immersion in rabbits

Objective To establish an animal model of open spinal cord injury associated with seawater immersion, and then to observe the effects of hyperbaric oxygen (HBO), methylprednisolone (MP) and MP + HBO on the spinal cord injury associated with seawater immersion, and finally to evaluate the therapeutic effects of the 3 intervention methods and analyze the advantages and disadvantages of the 3 treatment methods. Methods Eighty Japanese white rabbits with a weight range from 2.5kg to 3kg were used in the study. The animal model of the 10th thoracic spinal cord injury was developed by using the modified Allen's method, and then they were exposed to artificial seawater. The animals were randomly divided into 4 groups, the control group, the HBO group, the MP group, and the MP + HBO group, each consisting of 20 animals. Respectively at 4 different time points after injury, i. e. at hours 6, 12, 24 and 48, neurological function scores were evaluated by using the Tarlov method, and the expression levels of Bax, Bcl-2 and NF200 were detected by immunohistochemistry, and apoptosis of neurons in the spinal cord tissue was evaluated by the TUNEL method. Results Both the Tarlov scores and histopathological indexes of the MP + HBO group and the MP group were superior to those of the blank control group, and statistical differences could be noted, when comparison were made between them (P<0.05). The detected data of the MP + HBO group were superior to the other treatment groups, and statistical differences could be noted, when comparison were made between them (P<0.05). Conclusions Separate application of HBO or MP could reduce apoptosis of spinal cord cells and promote recovery of the injured spinal cord through the inhibition of Bax and reduction of the expression levels of Bcl-2 and NF200, thus alleviating injury to neural cells of the spinal cord. Nevertheless, the combined application of HBO and MP would result in synergistic and enhancing effects on the damaged tissue. Key words: Hyperbaric oxygen; Spinal cord injury; Methylprednisolone; Seawater immersion; Apoptosis; Apoptosis regulatory protein; Rabbits