| Spinal cord injury (SCI) often causes pitiful consequence, but its repair is actually the long-term puzzled clinical difficult problem, resulting in the huge suffering and the serious burden of the society and family. So, the pathology of SCI become a significant and difficult problem for science research. The primary mechanical injury not only destroy the tissue of spinal cord,but also damage the vessels, including the blood-spinal cord barrier (BSCB). It makes the edema, ischema, anoxia, and serious of serum proteins into spinal, aggravating the microenvironment in the injury site, producing a series of sequential damage function. Therefore, the research of BSCB permeability change after SCI appears extremely important.The area of injured blood-brain (spinal cord) barrier (BBB, BSCB) is often detected by injection of exogenous tracers. We had successfully made use of the endogenous immunoglobulin G (IgG) as an indicator to study the BBB permeability in the rat hypertension model. This research is divided into two parts: First, taking the exogenous IgG as the indicator, we investigate the extent of the BSCB opened at different time after injury. Second, we injected exogenous rabbit IgG, with the same molecular weight and biochemical property as rat, in different time, as the indicater, and compared the distribution of the tow types of IgG.In the first part, we inject rabbit IgG as an exogenous indicator and show its distribution of exogenous rabbet IgG with immunostaining, and threshold image segmentation to demonstrate the BSCB permeability change and analyze the extent of the opened BSCB at different time after injury(0 h, 1 d, 3 d, 5 d, 7 d), Distance of distribution (mm): 5.84±0.60, 8.33±0.47, 9.50±0.44, 4.48±0.23, 0.00±0.00 ; Area of distribution (mm2): 6.24±1.00, 5.73±0.37, 7.17±0.15, 0.75±0.06, 0.00±0.00. It clearly demonstrates the extent of the opened BSCB. In this test, we investigate the BSCB undergo secondary injury with detrimental multi-substance at early time, expanding the injured range to the largest at 3 d. Then, with the harmful factors removed and the capacity recovering, the extent of injured BSCB is diminishing, and restore completely at 7 d after contusion, and the exogenous IgG is already unable to pass through the capillaries system in the injury site at this time.In the second part, we show and compare the distribution of exogenous rabbit IgG with that of the endogenous rat IgG with double immunohistochemical staining, and discover there was the obvious difference in the time and distribution after SCI. In the time interval, the exogenous rabbit IgG have not observed after 7 d, but the endogenous rat IgG is not eliminated until 14 d. In the area distribution, the extent of endogenous rat IgG is bigger than that of exogenous rabbit IgG obviously in the damaged epicenter at the early time(before 3 d). Then (after 3 d), endogenous rat IgG is bigger than exogenous rabbit IgG in the entire damage area. It indicates that in areas where the enhanced BBB (BSCB) have recovered, there is still remaining endogenous IgG, whereas the exogenous IgG accurately depicte the area of injured blood-spinal cord barrier. Whether and how the endogenous IgG ingredient, remaining in the damage area, participates in the spinal cord injury pathology process, need to study further.
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