Activation Of Microglia Following Spinal Cord Injury And Its Relationship With Blood Spinal Cord Barrier In The Rat

Spinal cord injury (SCI) often cause lifelong disability of the patients, resulting in enormous suffering and burden of the family and society. Most of the patients are under 30 years, who experience such an injury. So the pathology of SCI is a significant and difficult issue for scientists for many years. SCI include primary injury and secondary injury. Mechanical insult to the spinal cord caused primary injury; it results in the destruction of the local neural tissue. Secondary injury after traumatic spinal cord injury is related not only to grossly injured vessels but also to a series of pathological changes.Since spinal cord has rich blood supply, the blood vessels are destroyed at the time when SCI occurred, and the function of the BSCB was influenced. As a type of immunocyte in central nervous system, Microglia is activated after SCI and migrate into the lesion site secreting cytokines, which is closely related to the secondary injury.A great number of studies were carried on the mechanism of SCI, but whether there is a relationship between the changes of BSCB after SCI and the activation of microglia is not clear. So we used spinal cord crushing as a model to study the relationship between the destruction of Blood Spinal Cord Barrier and the activation of microglia cells and in the experiment we use H.E staining to observe pathologic changes after SCI. We investigate the area of the injury lesion at 0h, 8h, 24h, 72h, 1w, 2w and 4w group. The result showed that the area at every time point was 0.47±0.11mm2, 1.60±0.60mm2, 1.80±0.57mm2, 3.88±1.86mm2, 3.51±1.29mm2, 2.33±0.53mm2 and 2.23±1.44mm2. At the same time we use fluro-immunostained with an anti-OX-42 for examination of microglia cells. Evens Blue was injected via the femoral vein for detecting the changes of the Blood Spinal Cord Barrier. Activated microglia cells started to appear at 24h group. Later, a number of the microglia cells migrated into the lesion and became macrophages for removal of the necrotic debris. The activated astrocytes at the vicinity of the lesion could be identified and is know to stay there for a long tine thereafter. Evens Blue can not pass through the normal Blood Spinal Cord Barrier At 1w group it could no more be detected in the spinal cord, the Blood Spinal Cord Barrier had fully recovered. There was a prominent mismatch between the time of the presence of microglia phagocytes and that of the impaired Blood Spinal Cord Barrier. The result of this study showed that the activated microglial alone is not enough to disrupt the Blood Spinal Cord Barrier.In conclusion ,there was a prominent mismatch between the time of the presence of microglial phagocytes and that of the impaired BSCB, activated microglial alone is not enough to disrupt the Blood Spinal Cord Barrier.The area of the injuryed lesion reach the peak and form a cavity at 2w group.