Study Of Differential Gene Expressional Changes After Injury Of Different Spinal Cord Tracts

Objective:To compare the different gene expressional changes and difference in gene ontology and pathway between RST and dCST after transection at 24h; try to explain different regeneration abilities of different evolved spinal cord tracts using evolutionism at the gene level; and provide a robust framework in the treatment of SCI in the light of evolutionism.Methods:Gene expressional profiles obtained in former experiments were analyzed, and the differentially expressed genes were screened and compared by SAM. The biological processes and pathways between RST and dCST were analyzed by MAS, GO, Kegg, and GenMAPP.To corroborate and validate microarray results, Fos, Ntrkl, Gadd45a, Myc, Sox7, Tnfrsfl2a, Slc5a3 and Rnf6 were selected for RT-PCR test.12 female Sprague-Dawley rats, which weighed 200-230g (average 220g), were divided randomly into 4 groups:bilateral dCST+FCFG transection group (n=3), bilateral FCFG transection group (n=3), bilateral RST transection group (n=3) and sham operation group (n=3). Rats were sacrificed24h after injury,5mm length spinal cord specimens centered injury site were procured. Total RNA were extracted and purified. RT-PCR was performed and the results were compared with results of microarray analysis.Results:Differences of gene expressional profiles exist between RST and dCST after injury. The expression of 153 genes changed after transection of RST, 136 were up-regulated and 17 were down-regulated. The expression of 26 genes changed after transection of dCST,22 were up-regulated and 4 were down-regulated. The number of biological process terms significantly changed (P < 0.05) after RST transection was 164,25 terms involved with no less than 3 gene counts; the number of pathways significantly changed (P< 0.05) was 25,17 terms involved with no less than 3 gene counts. The number of biological process terms significantly changed (P< 0.05) after dCST transection was 7, the number of pathways significantly changed (P< 0.05) was 1, all involved with less than 3 gene counts. Most of the functions were related to acute phase response such as immune response, antigen processing and presentation, inflammatory response. Few genes were related to neural regeneration.The expressional changes of Myc, Fos, Tnfrsfl2a, and Gadd45a tested by RT-PCR were in accordance with the results of microarray analysis. The expressional changes of Sox7 and Rnf6 showed no significant changes after RST transection. The expressional changes of Ntrkl and Slc5a3 after RST transection were contrast to the results of microarray analysis.Conclusion:The different expressional changes of genes have nothing to do with injured area. Further experiments should be performed to testify if it is related to different evolution. Genes related to neural regeneration such as Fos and Ntrkl were more up-regulated after RST transection, pathways related to axon regeneration such as MAPK pathway was activated after RST transection, which suggest RST has stronger regeneration ability at the gene level. However, this should be testified at the protein and histology level. Other genes significantly up-regulated after RST injury, such as Tnfrsfl2a and Gadd45a may have relationship with axon regeneration, and deserves further research.