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[Impacts of high-dose methylprednisolone on gene expression profiling in acute spinal cord injury].

OBJECTIVE
Methylprednisolone (MP) is the only active drug for acute spinal cord injury (SCI), but the molecular mechanism is still further studied. To investigate the pathophysiology of SCI and the molecular mechanism of MP in treating SCI.


METHODS
Nine rabbits were randomly divided into 3 groups, weighing (3 100 +/- 140) g: sham operation group (group A, n = 3), model group (group B, n = 3), and drug treatment group (group C, n = 3). After laminectomy was performed in 3 groups, no treatment was given in group A, and the model of SCI was established with modified Allen's falling strike method in groups B and C at L4; then high-dose MP equivalent with human dose was adopted in group C at 2 hours after SCI and the normal saline in group B. All rabbits were sacrificed at 8 hours after SCI, and then the spinal cord tissues about 8 mm long which included the injured site were obtained. Total RNA was isolated with Trizol one-step method to examine the gene expression profile by using Oglio technologies with standard operating procedures and quality control as recently described respectively. GeneSpring11.0 analyzer software was used to filter potential candidate genes for statistical significance using Welch's t test, and only genes with P < 0.05 and fold change (FC) > or = 2 were retained for further analysis. Some differentially expressed genes were also verified by RT-PCR to ensure the reliability of microarray results.


RESULTS
The SCI model was set up and the samples of spinal cord tissues were acquired successfully at 8 hours after SCI. The qualify of total RNA from each group met the requirement for the microarray examination and data analysis. These differentially expressed genes involved inflammation, immunity, ion transportation, transcription factors, and so on. The results of genes IL-1alpha, IL-1beta, and defensin 4 (NP-4) by RT-PCR were consistent with that of gene-chips. The immuno-related genes included NP-3, NP-4, corticostatin 6, CAP-18, and antimicrobial peptide, which displayed obvious differential expression.


CONCLUSION
High-dose MP has protective effects on nervous function by the immunity mechanism, and the main effector may be neutrophil.