Effects of astrocyte and microglia on spinal cord injury of the rabbits in decompression sickness

Objective To investigate the effects of astrocyte and microglia on spinal cord injury of the rabbits in decompression sickness (DCS). Methods Twenty-one healthy adult male New Zealand rabbits were averagely divided into 3 groups according to random number table: control group, safety relief group and DCS group. Experimental animals were placed in the pressure cabin. Safety relief group model referred to the Chinese Navy diving decompression tables when decompression applied. In DCS group, the pressure equably was increased to 0.8 MPa (absolute pressure) within 5 min by compressed air, maintained for 60 min and then equably decompressed to normal pressure within 5 min. The change of pathology morphology in the spinal cord of thoracolumbar vertebra was observed by light microscope. The expression of tumor necrosis factor-α (TNF-α) and Glial Fibrillary Acidic Protein (GFAP) mRNA were measured by real-time polymerase chain reaction (real-time PCR) and the expression of TNF-α, GFAP, ionized calcium binding adapter molecule 1 (IBA1) protein was measured by immunohistochemistry method. Results There were some cavity formations on white matter of spinal cord in DCS group. The relative expression of TNF-α mRNA was higher in DCS (6.28±1.73) than that in control group (1.00±0.14) and in safety relief group (1.34±0.42) (P<0.01). The relative expression of GFAP mRNA was higher in DCS (7.39±2.04) than in that control group (1.02±0.26) and in safety relief group (1.63±0.90) (P<0.01). The expression of TNF-α protein was significantly higher in DCS group (24.14±2.61) than that in control group (6.71±1.25) and in safety relief group (8.28±1.11) (P<0.01). The expression of GFAP protein was also significantly higher in DCS (18.20±4.38) than that in control group (4.30±2.70) and in safety relief group (6.20±2.92) (P<0.01). The expression of IBA1 protein was also significantly higher in DCS (21.53±1.37) than that in control group (5.94±0.36) and in safety relief group (6.69±0.81) (P<0.01). Conclusions The astrocyte and microglia may play a key role in pathophysiology of spinal cord injury. They are activated in the early stage of DCS and accompanied with massive release of TNF-α, which causes excessive inflammation reaction and induces the spinal cord injury finally. Key words: Decompression sickness; Spinal cord injuries; Astrocytes; Microglia; Tumor necrosis factor-alpha