The Optimal Juncture Of Preventing Spinal Cord Ischemia-reperfusion Injury With Methylprednisolone

When the factors that lead to spinal cord ischemia are removed, the spinal cord will be reperfused with blood. It's found that the spinal cord function is disabled obviously; the neurons tardively decease irreversibly even. This phenomenon is called spinal cord ischemia reperfusion injury (SCII).The spinal cord ischemia reperfusion injury is common in clinical, but it is hard to cope with. This kind of injury can be found in the patient whose spinal cord is oppressed obviously by herniated nucleus pulposus, hypertrophy of ligamenta flava or posterior longitudinal ligament, for example, serve cervical spondylotic myelopathy, thoracic canal stenosis cause by serve ossification of ligamenta flava or posterior longitudinal ligament. After the spinal cord is decompressed in a surgical way, it reperfused and SCII take place. In the SCII patient, the spinal cord function deteriorates obviously, and paraplegina or tetraplegia occurs subsequently in severe case. SCII brings great hazard to the physical and mental health of the patient, and a heavy burden to the society and patient's family.Heat Shock Protein 27 (HSP27) is a kind of protective protein. It has extensive effect, especially improve cells' adaption ability to harmful environment.Methylprednisolone (MP) is a kind of glucocorticoids. It's has the function of inflammation suppression, anti-oxidation, decrease the calcium ion accumulation in the cell and reduce the release of active amino acids. MP has been used preventing SCII in clinical. It has been certificated that high-dose MP per-treatment in an early period induces the up- regulation of HSP27 in local spinal cord tissue of acute spinal cord injured SD rat. But it is hard to found any report on the expression of HSP27 in the spinal cord of SCII animal model, and the relation of HSP27 expression and the use of MP for pretreatment.Aim: In this research, we built SCII animal model and use MP (30mg/kg) at 30min,lh or 3h prior to reperfusion to prevent SCII. With the different of the time of pretreatment, the HSP27 expression in the spinal cord is observed. We want to know the effects of pretreated with methylprednisolone to the expression of Heat shock protein 27 in rat's ischemia-reperfusion injured spinal cord; and the optimal juncture of preventing spinal cord ischemia-reperfusion injury with MP.Methods: Seventy-five SD rats were divided into five groups at random (n=15): Group A, B, C, D and E. The group is sham operated group; the abdominal aorta is exposed without occlusion. The group B is control group and the group B, C, D and E all underwent 30 min of aortic occlusion before the spinal cord reperfusion. The group C received 30mg/kg of MP 30 min prior to reperfusion. The group D and E received the same dose of MP at 1h and 3h prior to reperfusion respectively. The group B receive Sodium Chloride for control. Three hours after reperfusion, Spinal cord samples were taken for histopathological and immunohistochemistry evaluation. We observed the morphous, the nucleus, the nucleolus and the Nissl body of the neurons in a histopathological method, and the level and location of HSP27 expression an immunohistochemistrical method. The value of absorbance (A) is calculated in a computer analysis way and A stand for the relative amount of HSP27. The date is analysis with SPSS 10.0.Results: As we can see in the HE stained pathological section of group B, the atrophy of the neurons, the blur of the nucleus, the nucleolus and the Nissl body occur. That is to say the pathological change was severe in the group B. With 30mg/kg of MP was received 30 min prior to reperfusion, the pathological change, as we can see in the group C and D, was alleviated obviously. In various groups of experiment, the intensity of HSP27 expression differed, and the value of absorbance ((x|-)x±s×400) of five groups were 63.76±3.02, 100.32±4.13, 132.05±5.03, 121.92±4.68, 102.16±5.96 respectively. The expression in the group C and D was higher than the control group (P< 0.01), and the expression in the group C was also found statistically significant compared with the group B (P< 0.05). There is no significant statistical difference between the group C and the control group. The pathological changes of spinal cord cells were significantly improved in group A and B, compared with the control group.It's found that the expression of HSP27 in the SCII spinal cord tissue is up regulated, meanwhile the neuron lesion is alleviated, when the animal is pretreated with MP at special juncture. That is to say pretreatment with MP protects the spinal cord from SCII, and up regulate the expression of HSP27 may be one of the mechanisms of the protection effect.Also, it's discovered that the degree of spinal cord pathological changes alleviation and expression of HSP27 is different, when MP is used at different time junctures, 30min, 1h, and 3h for example. The best effect can be gain when MP is used 30min prior to reperfusion, and the effect is decrease when MP is used 1h prior to reperfusion. It's hard to found any effect of spinal cord protection when MP is used 3h prior to reperfusion. It indicate that, there is a best time window in the juncture of pretreated with MP.Conclusion: Pretreated with methylprednisolone up-regulate the expression of HSP27, especially when MP is used 30min prior to reperfusion, in rat's ischemia-reperfusion injured spinal cord cells, and the pathological change is trivial simultaneously. The expression of HSP27 achieves the maximum of efficiency when it was pretreated 30min before reperfusion, and this juncture might be the best time to prevent SCII with MP.