The microglial activation profile and associated factors after experimental spinal cord injury in rats.

Background: Spinal cord injury (SCI) has imposed a great impact on the quality of life of patients due to its relatively young age of onset. The pathophysiology of SCI has been proven to be complicated. Microglia plays an important role in neuroinflammation and second injuries after SCI. Different environment and other factors may determine the microglial activation profile and what role they play. However, neither accurate time-course profiles of microglial activation nor influence factors have been demonstrated in varied SCI models.

Methods: A rat compressive SCI model was used. Microglial activation profile and contents of inflammatory factors including IL-1β, IL-6 and TNF-α were detected. Myelination status as well as levels of iron and glutamate concentration, adenosine triphosphate (ATP) and potassium are also assessed.

Results: Our results showed that the activated microglia participating in immune-mediated responses peaked at day 7 post SCI and gradually decreased during the following 3 weeks. Contrarily, myelination and oligodendroglia showed an opposite trend, indicating that microglia may be a key factor partly through inflammatory reaction. Iron and glutamate concentration were found to be the highest at day 7 after SCI while both ATP and potassium reached a low valley at the same time.

Conclusion: These findings showed a microglial activation profile and the alterations of associated factors after experiment SCI model. Moreover, our data suggest that high iron and glutamate concentration may be released by damaged oligodendroglia and contribute to the activation of microglial after SCI.