Objective: To investigate the relationship between the expression of MMP-9 and the formation of spinal cord edema in presyrinx state of experimental syringomyelia in rabbits and evaluate the inhibitory function of doxycycline in the formation of spinal cord edema in presyrinx state.
Methods: A total of 96 Chinese white rabbits were divided randomly into four groups:kaolin group (n = 24), doxycycline treatment group (n = 24), physiological saline group (n = 24) and control group (n = 24). Under ketamine anesthesia, 0.6 ml of 25% kaolin solution was injected into the cisterna magna in all rabbits of kaolin and doxycycline groups while 0.6 ml of 37°C physiological saline into the cistern in those of saline group; doxycycline (25 mg × kg(-1) × d(-1)) was applied post-operatively for doxycycline group. At Days 1, 3, 7 and 14 after kaolin injection, 6 rabbits of all four groups were selected randomly for sacrificing. Water content of spinal cord could be obtained. The expression of MMP-9 activity was measured by Western blot and immunohistochemistry.
Results: At any time point, the water content of spinal cord and the expression of MMP-9 in kaolin group improved obviously more than those of saline and control groups (P < 0.01). At Day 1, there was no marked difference in the water content of spinal cord and the expression of MMP-9 between doxycycline and kaolin groups (P > 0.05). At other time points, the water content of spinal cord and the expression of MMP-9 in doxycycline group markedly decreased than those of kaolin group (P < 0.01).
Conclusion: In the model of experimental syringomyelia, MMP-9 plays an important role in causing edema in presyrinx state. Thus doxycycline may be used to prevent and treat syringomyelia.