| Although studies on repair of spinal cord injury by neural stem cells transplantation and gene engineering have made great progress, nerve regeneration can not be satisfied until today. So it is very important to prevent SCI, especially during operation of spinal column and cord. However, it is can not be avoided to stretch and compress spinal cord when osteophyte and tumor are removed or scoliokyphosis operation is performed. Previous studies have found that sodium aescinate has the effects of anti-inflammation, anti-edema, and resisting oxygen free radicals. It has been widely used in treatment of brain and limbs edema and so on. Could it protect spinal cord by injection before operation? This was the motive of present study.Objective : Through establishment of tractive spinal cord injury (TSCI) model inrats, we discussed the pathophysiological changes of this scathe by evaluation of behavioral functional tests and somatosensory evoked potential, and investigated the influence of sodium aescinate on locomotion function and somatosensory evokedpotential.Methods : 80 adult female Wistar rats, weighing 220~250g,were selected anddivided into four experimental groups (24h, 3d, 7d, 14d after operation, n=10) and matched control groups randomly. All rats were anaesthetized with sodium pentobarbital (30mg/kg). Sodium aescinate (SA) was given intravenous injection 30min before SCI at the high dose 1.5mg (6mg/kg) in the experimental groups. Equal volume of normal saline was given intravenous injection in control groups. After exposing the spinal cord entirely via dual laminectomy at T10 level, cortical somatosensory evoked potential (CSEP) was recorded by KEYPOINT 4M/4C SEP instrument, latency of CSEP PI wave and Pl-Nl amplitude were measured. Then the spinal cord was pull horizontally (displacement of 1.7mm,duration of 5min) by a special retractor imitating the neural ecarteur, and SEP was recorded again. The behavioral functional tests of hind limbs of rats were evaluated by using BBB locomotion scores and inclined plane test at each time point (24h, 3d, 7d, 14d) after SCI.The sensory function of rats was monitored by CSEP. The locomotion scores ofhind limbs ,latency,and amplitude were expressed as x ± s, P < 0.05 was considered satistically significant.Results ? (1) It could lead to incomplete paralysis of rats to pull spinal cord for1.7mm and 5min horizontally. (2) The behavioral functional test was not different significantly in 24h between experimental groups and control groups after tractive spinal cord injury and CSEP as well. BBB score, incline plane test and latency of CSEP (except the amplitude ) showed significant difference in 3d .The behavioral functional scores of experimental groups were higher markedly than that of control groups .The behavioral functional tests and CSEP (latency and amplitude ) were significant different in 7d and 14d , PI wave latency was shorter and Pl-Nl amplitude was higher obviousely in experimental groups. (3)The spinal cord function was better in experimental groups than that in control groups.In experimental groups (injection SA before operation), the BBB average score raised from 1.4 to 11.8, average inclineplane test angle raised from 26.4° to 60.19° , amplitude raised from 1.20uv to 2.01uv and latency shortened from 8.7ms to 5.3ms. (4) There was no significant correlation in experimental group between the delayed value of latency and the increased scores of BBB from 3d to 7d after SCI (r=0.448).Conclusion :The tractive spinal cord injury model of incomplete paralysis can beduplicated certainly by pulling spinal cord at T10 level. The model of this study was a valuable assistance in understanding the etiopathology of spinal cord injury. CSEP examination can provide an objective and quantitative standard for judging the sensory functional status in the spinal cord injury. It can decrease spinal cord injury and is benefit to recovery of spinal cord by injecting high dose SA before SCI. The protection of SA can be reflected by neural electophysiological changes.Part TwoSignificance of Expression of Bcl-2, Bax Protein and Neural Cell Apoptosis and Inhibition of Sodium Aescinate on Cell Apoptosis after Tractive Spinal Cord Injury in Rats Spinal cord injury can divided into primary injury and secondary injury. Secondary injury will lead to delayed neuronal death, including the death from excitatory toxicity and apoptosis. The radio of protein bcl-2, bax will determine whether apoptotic cells will die or not. In Part One of present study, we have investigated the tractive spinal cord injury, but how did the cell apoptosis after trative spinal cord injury, and whether did the mechanism of protecting spinal cord injury by injection sodium aescinate. relate to inhibition of cell apoptosis? This was the aim of Part Two.Objective: To observe the changes of expression of bcl-2, bax protein and neural cell apoptosis, and explore the molecular mechanism of secondary spinal cord injury, study the inhibition effects of SA on neural cell apoptosis after tractive spinal cord injury in rats.Methods: 80 Wistar rats (the experiment of Part One) were reanaesthetized with sodium pentobarbital (30mg/kg) and sacrificed in 24h, 3d, 7d, 14d after SCI (n=10, at each time point). 4% paraformaldehyde was perfused from the left ventricle of the rats, 2cm-long spinal cord was removed from wounded areas and fixed with 4% paraformaldehyde for 24~48h. A serials of 5um cross section was cut at epicenter and caudal to epicenter. The hematoxylin and eosin (HE) staining for histology and the immunochemicaly staining for bcl-2, bax protein were performed. Cell apoptosis was examined by method of terminal deoxynucleotidyal transferase-medicatedd-UTP-biotin nick end labeling (TUNNEL) .The construction of spinal cord was observed under light microscope, bcl-2, bax protein and cell apoptosis index were examined at each time point.Result: (1) The segment of HE staining showed that destruction of spinal cord and neural cells necrosis were more severe in the control groups, such as reduced number of motor neurons of anterior horn, disappearance of Nissl bodies and nuclei, and vacuolation of gray matter. That was not serious in the experimental groups. (2) There were not expression of bcl-2, bax protein and apoptotic cells in normal control group, but expression of bcl-2, bax protein and apoptotic cells could be observed. They increased at 24h. Bcl-2 expression reached at peak in 7d and declined in 14d in experimental groups, while it did at peak in 3d and declined significantly in 7d in the control groups. Bax protein reached at peak in 3d and declined significantly in 7d in experimental groups, but it did at peak at 7d and declined till 14d in the control groups. (3) At each time point, expression of bcl-2, bax protein apoptosis cells showed significant difference (P < 0.01) .The apoptosis index was lower in experimental groups than that in control groups (P < 0.01).Conclusion: There is cell apoptosis phenomenon after tractive spinal cord injury in rats. Cell apoptosis plays an important role on secondary SCI. SA may effectively inhibit the neural cell apoptosis, decrease the secondary SCI, because it has a strong important role of anti-inflammation, anti-edema, resisting oxygen free radicals. It can improve the mini-envionment of neural cells and protect spinal cord.
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