Aquaporin-4 expression dynamically varies after acute spinal cord injury-induced disruption of blood spinal cord barrier in rats.

ABSTRACT

The blood-spinal cord barrier (BSCB) changes badly after spinal cord injury (SCI), and it is an important pathophysiological basis of SCI secondary damage. Aquaporin-4 (AQP4), one of the transmembrane proteins in spinal cord, has been shown to be closely related to the development of the BSCB and edema. We established a SCI model in rats using a free-falling weight drop device to subsequently investigate AQP4 expression. AQP4 messenger RNA (mRNA) and protein expression and immunoreactivity were detected in spinal cord tissue using reverse transcription-real-time quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry and Western blot analysis. We found the water content and edema of the spinal cord were significantly higher than the control group after SCI, which was related to the growth of BSCB permeability; both reached their peak on the third day after injury. One, 3, 5, 7 days after injury, the immune response and protein expression in the model group increased from 1 to 3 days, with a plateau period from 3 to 5 days and a decline from 5 to 7 days, showing a significant difference compared with the sham group at each time point (P < 0.05), while the RT-qPCR results showed a decline of mRNA just after 3 days. In conclusion, after SCI, the water content of the spinal cord and the BSCB permeability increases, together with the excessive expression of AQP4, which reached a peak on the third day. AQP4 expression is closely relative to the permeability of BSCB and the water content of the spinal cord.