The Role Of Serum Response Factor (SRF) In The Repair Of Spinal Cord Injury

Spinal cord injury is a common disease in modern society,the sensory and motor function of the injured plane is completely lost after the spinal cord injury,which can bring a heavy burden to the patients and their families.At present,there is no an effective treatment.So the treatment of spinal cord injury has a great social significance.As a transcription factor of the MRTF family,serum response factor(SRF),is widely expressed in the different organisms.The research has found that SRF plays an important role in the development of central nervous system(CNS);SRF deficiency might cause the severe demyelination in neurons and overexpression of SRF could increase the length of axons.Another study found that SRF could promote the regeneration of facial neurons in the peripheral nervous system(PNS),but there is no experimental study on the effect of SRF on spinal cord injury.In order to explore the role of SRF in spinal cord injury,immunohistochemical staining was used to detect the expression of SRF in normal and injured spinal cord at different time points(0d,7d,14d,28d).The expression of SRF was detected by RT-RCR and Western blot(WB)in our study.Immunohistochemical staining showed that SRF was expressed in the gray matter of the normal spinal cord,and was also expressed in the nucleus and cytoplasm of the spinal cord neurons.The results of the immunohistochemical staining,WB and RT-PCR showed that the content of SRF increased gradually after the spinal cord injury and reached the highest level on the seventh day,then began to decrease and the expression of SRF was close to normal at twenty-eighth days.In order to further explore the role of SRF in repair of spinal cord injury,this study used RNAi(RNA silencing)technology,a lentivirus vector expression of SRF(LV-srf)and control(NC)and SRF virus(srf-RNAi),and the silence was detect the lentivirus,which was transfected into PC 12 cells to get the best titer.SD rat model of spinal cord injury was constructed and the virus with the best titer was injected into the spinal cord injury site of the rat.We used the immunohistochemical staining,WB and RT-PCR technology to verify the virus expression in vivo transfection after 1 weeks of injection and BBB score was applied to each group with a total of 8 weeks.After the two months of the operation,the rats on the transverse section of the spinal cord at 0.5cm spinal cord tissue were cut,the transmission electron microscopy observed the ultrastructure of tissue,immunofluorescence assessed the express of GAP43 and BDA anterograde tracing observed the spinal nerve fiber repair to evaluate the effect of SRF in spinal cord injury.BBB score showed that the normal group score was 21 points,the scores was 0 points when the spinal cord injury rats were completely paralyzed;the overexpression of SRF group was higher than that of the control group,with a score of 2 and lpoints at the second weeks after injury;The score was 5 points in overexpression group of SRF and the control group is 2 after injury at the 4th weeks;the overexpression group of SRF was 7 points and the control group was 3 after injury at the 6th weeks;And at the 8th weeks after injury,the score of the SRF overexpression group could reach to 9 points,the hind legs could withstand a certain amount of gravity,visible 2-3 joints slightly active,while the control group was 5 points and just rely on the forelimb drag forces to accomplish crawling movement(There was significant difference between the groups in each time stage).The results of electron microscopy showed that there were dense axonal myelin around neurons in the SRF overexpression group,the control group showed the axonal peripheral myelin loose arrangement of immunity.Fluorescence results showed GAP43 was overexpression in the SRF group,while in the control group only an extremely small number of GAP43.BDA expression results showed that SRF overexpression group nerve fiber growth could through the glial scar,while the control group only a small amount of nerve fiber glial scar.In conclusion,SRF plays an important role in the repair of spinal cord injury process,which can effectively promote the axon regeneration and improve the motor function of animal spinal cord injury recovery.Therefore,SRF is expected to be a new target for the treatment of spinal cord injury.