Effect of olfactory ensheathing cells transplantation on RhoA expression in injured region after spinal cord injury

AIM:Axonal growth inhibitor,combining with its receptor,can activate the signal RhoA and then result in cytoskeletal collapse and inhibit the neural regeneration.Basic and clinical researches have both proved that olfactory ensheathing cells(OECs)can improve the recovery of spinal function,we conducted a study to investigate the effect of OECs transplantation on level of RhoA in the injured region after spinal cord injury(SCI),and explore the possible mechanism of OECs transplantation in the treatment of SCI. METHODS:The experiment was enforced from September 2005 to May 2006 in the Key Laboratory of Environment and Genes Related to Diseases of Ministry of Education,Xi'an Jiaotong University.①Forty adult SD rats were randomly divided into void group,model group,OECs group and DF12 control group,with 10 animals in each group.In addition, another 30 healthy male SD rats were served as the source for OECs.All the disposals in the experiment fit the ethical standard of animals.②Rats were executed after anesthesia,which was followed by removing pia mater in the isolated bilateral olfactory bulb and cutting olfactory nerve layer as well as glomerular layer.OEC suspension was obtained after centrifugation and trypsin digestion.All the animals apart from void group were established SCI model by transection. Then the OECs were primarily cultured for 12 days,and the suspension(1×10~(11)L~(-1))was injected into four regions about 1mm from the margin of injury(about 1.0mm deep)of OECs group,1μL every point.DF12 culture fluid was injected into DF12 control group in the same dose and same method.The void group and model group were untreated.③In the 1~(st),2~(nd),4~(th),6~(th)and 8~(th)weeks after injection,immunohistochemistry and Westem blot assay were used to evaluate the level of RhoA in the injured region after OECs transplantation.And the silver staining was applied to detect the histomorphological changes in the 8~(th)week after injection. RESULTS:①RhoA protein level in void group were obviously lower than that in other groups(P0.05),and it in OECs group was distinctly lower than that in DF12 control group and model group after transplantation(P0.01).There were no significant differences between model group and DF12 control group(P0.01).②All the animals apart from the void's had an obvious regeneration of injured axons,but the regenerated fiber in model group and DF12 control group aligned in disorder and appeared bad directivity compared with that in OECs group after transplantation for 8 weeks;in OECs group,there were obvious regenerated axons and nerve fiber could repair SCI over the injured lesion.So the results were superior to that of model group and DF12 group. CONCLUSION:OECs transplantation may enhance the repair of injured spinal cord by depressing the level of RhoA in the injured region.