| Spinal cord injury (SCI) often cause lifelong disability of the patients, resulting in enormous suffering and burden of the family and society. So the pathology of SCI is a significant and difficalt problem for scientists for many years. After SCI, primary injury was caused by mechanical damage and incontinuity of the tissue and vessels, which will lead to a complex secondary injury process such as hemorrhage, inflammation and exitotoxicity et al. The damage of microvessels caused by primary injury will insult the BSCB directly. Serum proteins will cross the compromised BSCB, and edema, ischema and anoxia, inflammation and change of blood flow will issue. Because of the important roles BSCB palyed in the SCI pathology, a lot of research about BSCB was performed, but changes of BSCB and its relationship with secondary damage was not well known. At present study, we use the NYU contusion SCI model of rat to study the change of BSCB permeability and its impact on secondary injury.This thesis comprises two parts. In part one, we used immunohistochemical staining of immunoglobulin G (IgG) to study BSCB permeability after SCI. In past, injection of tracers was used to study the BSCB permeability after SCI, which was complicated in operation and will affect other investigations. In order to search more convenience and reliable method, we considered using endogenous IgG to assess the BSCB permeability to macromolecules. Evans Blue injection was a conventional method to study the BSCB permeability after trauma. We examined the distributions of IgG and EB at 0 h, 8 h, 24 h, 72 h, 1 w after injury. The reault showed that, the rostral-caudal distance of IgG (mm) at every time point was: 7.14±0.50, 11.43±1.63, 9.48±1.71, 9.82±0.63, 5.59±0.55, and that of EB was:7.2±0.51, 11.25±1.60, 9.27±1.65, 9.42±0.54, 5.58±0.48. Interestingly, in spite of diffusion of these molecules, the distributions of IgG and EB were almost coincident at all time points, especially in the caudal-rostral dimension in gray matter. So IgG staining was a convenience and reliable method to investigate BSCB permeability after SCI.In part two, BSCB permeability was estimated by IgG immunostaining. To assess the secondary injury, HE staining was used to estimate the injury extention, and NeuN immunostaining to estimate the extention of neuron loss. The range of IgG was compared to that of secondary injury including injury area and neuron loss. At 0 h, 4 h, 8 h, 24 h, 72 h, 1 w after injury, the range of injury (mm) was 3.64±0.92, 6.03±0.47, 7.04±0.42, 7.11±0.53, 9.32±0.17, 8.63±0.31, respectively, and that of IgG distribution was 7.27±0.43, 7.74±0.53, 11.43±1.60, 9.48±1.65, 9.90±0.60, 5.55±0.40, respectively.The IgG positive area actually include the BSCB damage area and the area of diffusion. At 0 h to 72 h, injury range (mm) increased gradually, and the tendency of IgG range was increasing, too, but peaked at 8 h. From 72 h to 1 w after injury, the injury area changed not significantly, and the IgG area decreased (p<0.05).Neuron death was investigated to further study the relationship between BSCB damage and secondary injury. We found that at 0 h after injury, IgG was accumulated in many neurons at and near the injury site. In EB injection group, EB was in these neurons either. The distributions of available neurons at 0 h and 4 h were consistent, and the IgG positive neurons were disappeared at 4 h. Thus the IgG positive neurons were probably vital cells, and died quickly, but no significant died signs were investigated in HE and Nissl's staining. At 0 h, the range of neuron loss (mm) was 1.06±0.21, this range increased significantly to 4.73±0.27 at 4 h (p<0.05). At 8 h, 24 h, 72 h, 1 w after injury the neuron death area was 4.99±0.81, 5.22±0.85, 5.91±0.07, 6.42±0.32, respectively. The neuron loss increased but not significantly from 4 h to 1 w after injury. These results suggest that neuron death after NYU contusion SCI occurred primarily within 24 h after injury, and mainly attributed to mechanical insult.In conclusion, using IgG immunostaing to estimate the BSCB permeability to endogenous IgG after SCI has many advantages, and it is a convenience and reliable method to investigate BSCB permeability after SCI. With the injury area increased gradually, the BSCB damage area increased, too. Thereafter, the injury area stabled, and the range of BSCB damage decreased. Neuron death after NYU injury mainly attributed to mechanical insult, and occurred primarily within 24 h after injury. The reason and significance of IgG entering neurons need to be researched further. |
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