Abstract:

Objective To explore changes of the activity of PI3K/Akt/mTOR signaling pathway in early stage of spinal cord injury (SCI) of rats and the effects on the recovery of motor function of posterior limbs. Methods SD rats were randomly divided into the normal group, control group, and 4 experiment groups (1 d, 3 d, 5 d and 7 d after SCI groups). The Allen’s WD-SCI model was established for rats of the control group and experiment groups. Then 20 μL LY294002 (inhibitor of PI3K/Akt/mTOR signaling pathway) and 20 μL sterile purified water were intrathecally injected into the rats of control group and other groups. The combine behavioral score (CBS) method was adopted to evaluate the motor function of posterior limbs. The changes of the activity of PI3K/Akt/mTOR signaling pathway of spinal cord tissue of injured segments were detected by the RT-PCR and immunohistochemistry assay. Results For experiment groups, the motor function of both posterior limbs improved and the CBS scores declined with time after SCI. The relative mRNA expressions of PI3K, Akt, and mTOR in spinal cord tissue of injured segments upregulated and the number of cells with positive expression of PI3K, Akt, and mTOR proteins increased. Compared with rats of the 7 d after SCI group, the recovery of muscle strength and motor function of both posterior limbs of the control group were poor, and the relative mRNA expressions of PI3K, Akt, and mTOR and the number of cells with positive expression of PI3K, Akt, and mTOR proteins in spinal cord tissue of injured segments decreased. Conclusion PI3K/Akt/mTOR signaling-pathway is relevant to the reconstruction of nerve function in early-phase of SCI and can be used as a target of clinical treatment.

Key words: spinal cord injury, PI3K/Akt/mTOR signaling-pathway, RT-PCR, immunohistochemistry