| BackgroundSpinal cord injury is a relatively common central nervous system damage, and it lead to big destruction and can cause very serious consequences, which is a disabling disease, injured segments and segments dominated by them make motor and sensory dysfunction, then there may be frequent urinary tract and respiratory infections, at the same time it can lead to complications of bedsores, gastrointestinal and cardiovascular, which will severely influence physiological and heart health in patients. In the case of spinal cord injury, it will be a devastating blow to individuals and families, but also to society and thus become a huge burden. How to restore spinal function and reduce complications after spinal cord injury has become a major problem placed in front of patients and medical workers. With the continuous development of technology, especially for re-recognising epidemiology and pathophysiology of spinal cord injury, the rapid development of imaging technologies, perfecting the medical and surgical treatment, these patients seem to see a glimmer of hope, although the research for treatment of spinal cord injury were reported frequently at home and abroad, the cure is still has not gotten. Therefore, positive and sustained research for treatment of spinal cord injury is bound to have an important and far-reaching social significance.The pathophysiological mechanism caused by spinal cord injury is extremely complex, ischemia and microcirculation disorder after the injury can cause a series of complex chain reaction, mainly in the following two aspects, namely neurons necrosis in spinal cord injury site, apoptosis of oligodendrocyte, myelin disintegration, degeneration and necrosis of nerve and the inflammatory reaction in the acute phase, while in subacute stage, apoptosis and necrosis of neuron further, glial cells gradually appeared pathological hyperplasia and fibrosis, where axons appeared demyelination changes, which will eventually hinder the recovery of neural function, therefore, to recovery of nervous function after spinal cord injury, we should make myelin axonal regeneration at first. Remyelination is when the axon occurred demyelination, the oligodendrocyte precursor cell around demyelinating lesions can proliferate and migrate to demyelinating areas, gradually transform into mature oligodendrocytes and wrap axis, finally new myelin are rebuild. Thus, mature of oligodendrocytes is the main element for the myelin cells regeneration, and mature oligodendrocytes are mainly derived from oligodendrocyte precursor cells. The oligodendrocyte precursor cell in spinal cord is a class of glial cells which have the ability of proliferation and differentiation, in the appropriate microenvironment, it can be activated and differentiate to be oligodendrocytes, which will play an important role in reformating of damaged myelin and recovering spinal cord injury. Oligodendrocyte precursor cells in spinal cord under the normal physiological environment is always in a dynamic steady state, i.e. increasing or decreasing the volume and the number of cells is in a relatively stable state, when the spinal cord injury resulted in changes in local microenvironment, the oligodendrocyte precursor cells in a steady state are activated, the volume and the amount of cells were increased. Early studies suggested that, relying on its own ability to repair is difficult after spinal cord injury, deads neurons after damage can not be producted by spinal cord itself or replaced by nearby neurons, because accumulation ability of oligodendrocyte precursor cells in the regeneration process is limited, and there is interference during the differentiation and maturation process of the aggregated oligodendrocyte precursor cell, which can lead to unsuccessfully differentiated into mature oligodendrocytes. Oligodendrocyte precursor cells are affected by many factors during the migration and differentiation process, how to make the oligodendrocyte precursor cells in injured spinal cord accelerate proliferation, migration and differentiation is the topic of the first part.The current studies in the treatment of spinal cord injury mainly includes the following several aspects:(1) Control the secondary injury after spinal cord injury through the hormone shock, ion channel blocking, scavenging free radicals and other methods.(2) By restoring damaged local microenvironment of the spinal cord to improve damaged axons and myelin regeneration, enhance the plasticity of the central nervous and promote an undamaged area nerve compensatory ability, including cell transplantation, the application of nerve growth factor and electrical stimulation, etc.(3) Using gene silencing technology and axon growth inhibitory factor to remove or neutralize the disadvantageous factors of inhibition of axon regeneration after spinal cord injury, in order to promote axon regeneration indirectly. Electrical stimulation is becoming a hot spot of research in recent years. Research shows that adding electric field around the spinal cord injury can eliminate endogenous injury current, reduce the axonal degeneration and atrophy, promote the regeneration of the axon and myelin sheath formed again, can effectively inhibit the proliferation of astrocytes, inhibit the scarring on spinal cord injury in lacerated end. This can alleviate limb muscle spasms, prevent unnecessarily muscle atrophy, facilitating the recovery of muscle function. The method can also improve the function of bladder contraction after spinal cord injury, promote urination, thus improving the prognosis of spinal cord injury. Direction changing of the electric field stimulation of cathode and anode plays a pivotal role on nerve regeneration after spinal cord injury. In order to clarify the effect of the the direction of the electrodes stimulation on nerve regeneration after spinal cord injury, a new special electric stimulation technology is developed, namely the oscillating electric field stimulation. Oscillating electric field stimulation is a recent physical method, whose mechanisms related to promote the regeneration of the myelin sheath. Implanting devices every15minutes to transform the polarity of the electric field, to promote the growth of another side neurites to the cathode before the anode rejection neural axon growth, are the processes of oscillating electric field stimulation. So as to ensure the two-way growth of axon, alleviate the degree of nerve reverse disintegrating, reduce the formation of glial scar and enhance neural functional recovery.Based on the above analysis, this study intends to through applying oscillating electric field stimulation on rats with spinal cord injury, watch the dynamic changes of activation of oligodendrocyte precursor cells in damaged spinal cord, and watch myelin regeneration and neural functional recovery of experimental animals. This study intends to confirm that the oscillating electric field stimulation can speed up proliferation and differentiation of oligodendrocyte precursor cells in damaged spinal cord,the injury in the spinal cord less value and differentiation of glial progenitor cells, and can improve the speed of the recovery of motor function, and provide a more detailed study basis for the oscillating electric field stimulation to repair spinal cord injury. We can clarify the role of oscillating electric field stimulation in the repairment of spinal cord injury through this topic research, further deepen the recognition of oscillating electric field stimulation, and provide a new train of thought for later study on treatment of spinal cord injury.The study is divided into two parts:Part I:Oscillating electrical field stimulation makes an active effect on spinal cord oligodendrocyte precursor cells in spinal cord injury rats;Part II:oscillating electric field makes an effect on nerve function and myelinin regeneration in spinal cord injury rats. Part I:Oscillating field stimulation makes an active effect on spinal cord oligodendrocyte precursor cells in spinal cord injury ratsObjective:By observing oligodendrocyte precursor cell proliferation and differentiation in the injured spinal cord, and the dynamic changes of proliferation and differentiation in the injured spinal cord stimulation via dynamic oscillating electric field, to reveal the active effect of oscillating electrical field stimulation on oligodendrocyte precursor cell in injured spinal cord.Method:Construct SD rat spinal cord injury model, using Allen hit method and randomly dividing into normal group, control group and experimental group,ie the normal group (no treatment), spinal cord injury group (SCI) and spinal cord injury+oscillating electrical field stimulation group (SCI+OFS), rats in experimental group were given an oscillating electrical field stimulation, while rats in control group were only placed in oscillating electric field stimulator without giving oscillating electrical field stimulation. Oscillating electric field stimulator operating parameters are set as follows:current intensity40u A, the electric field strength400u V/mm, the electric field polarity exchange once every15min, using continuous-type power supply for power supply and continuous electrical stimulation. According to the observation time, each group was randomly divided into4d,7d,10d and14d four subgroups.Using BrdU and the oligodendrocyte lineage cells plane markers labeled oligodendrocyte cell line, using frozen sections, immunofluorescence staining and electron microscopy detected the dynamics of proliferation and differentiation and co-localization of receptor expression of oligodendrocyte precursor cell in spinal cord in the two groups. Result:1. In4d to14d, the number of oligodendrocyte precursor cells in the spinal cord injury group and spinal cord injury+oscillating electric field stimulation group showed a decreasing trend, while mature oligodendrocytes showed increasing trend;2. Oligodendrocyte cell line in spinal cord injury+oscillating electrical field stimulation group expressed in4d,7d,10d and14d were better than the spinal cord injury group, but the expression difference in4d and14d was the most significant.Co-localization expression of NG2-P1under oscillating electrical field stimulation in4d,7d,10d and14d were superior to spinal cord injury group; but in oscillating electric field group, co-localization expression of NG2-P1became weaker from4d to14d.Conclusion:Oligodendrocyte precursor cells in the early spinal cord injury gradually differentiate into mature oligodendrocytes. Oscillating electrical field stimulation can improve oligodendrocyte precursor cell activation in the injured spinal cord, promote oligodendrocyte precursor cells differentiate into mature oligodendrocytes. Part IIoscillating field stimulation makes an effect on nerve function and myelin regeneration in spinal cord injury ratsObjective:Assess the effect of oscillating electric field stimulation on nerve function and myelin regeneration in spinal cord injury ratsMethod:Construct SD rat spinal cord injury model, using Allen hit method and randomly dividing into normal group, control group and experimental group,ie the normal group (no treatment), spinal cord injury group (SCI) and spinal cord injury+oscillating electrical field stimulation group (SCI+OFS), rats in experimental group were given an oscillating electrical field stimulation, while rats in control group were only placed in oscillating electric field stimulator without giving oscillating electrical field stimulation. Oscillating electric field stimulator operating parameters are set as follows:current intensity40μA, the electric field strength400μV/mm, the electric field polarity exchange once every15min, using continuous-type power supply for power supply and continuous electrical stimulation. According to the observation time, each group was randomly divided into1w,2w,4w,6w,8w, lOw and12w seven subgroups. After modeling successfully, spinal cord injury rats were given BBB Rating, inclined plane detection test and MEP test at each time point, while making histopathological observation and statistical analysis.Result:Before two weeks of oscillating electrical field stimulation, BBB Rating and inclined plane test results in spinal cord injury group were similar to spinal cord injury+oscillating electrical field stimulation group, which had no statistically significance (P>0.05), from the second week, BBB Rating and inclined plane test results in two groups were significantly increased, from the4th week, BBB Rating and inclined plane test results in spinal cord injury group were significantly lower than the spinal cord injury+oscillating electrical field stimulation group, the difference between the two groups were statistically significant (P<0.05); and evoked potential test showed that MEP latency in spinal cord injury+oscillating electrical field stimulation group at each time point were lower than the spinal cord injury group, there was significant difference (P<0.05)of the latency between the two groups since the4th week. From the6th week, the relative amount of myelin in spinal cord injury+oscillating electrical field stimulation group was significantly higher than that in the spinal cord injury group, and it was statistically significant (P<0.05). Data in the last two weeks in each group were stabilized.Conclusion:1oscillating electrical field stimulation can improve conduction function of spinal cord in spinal cord injury rats, promote nerve function recovery in spinal cord injury rats;2oscillating electrical field stimulation of more than four weeks can promote nerve function recovery in spinal cord injury rats, but after10weeks its role will be significantly weakened;3oscillating electrical field stimulation can promote the regeneration of myelin. |
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