The Changes Of Brain Edema And Correlative Factors In The Target Area Of Rat Brain Radiated By Gamma Knife

Part 1: The change of brain edema in the target area of ratbrain radiated by Gamma knifeBackground and purposeRadiation-induced brain edema has to be more taken care whengamma knife is applicated in clinic. The pathological process andradiation biology in rat brain radiated by Gamma knife are variablebecause of different doses. In this study, 50 Gy, which is used frequentlyin Clinic for the treatment of intracranial diseases was used to irradiatethe rat brain. The investigation of pathophysiology and radiobiology inrat brain radiated with 50 Gy is helpful to the process of brain damagecaused by single radiation therapy and mechanism of early radiation braindamage.Methods180 healthy adult SD rats were divided into 3 groups, control group60, 60 for radiation therapy group with gamma knife, 60 sham radiationgroup. The rats were divided into 6 subgroups in different time points,12 hr, 1d, 2d, 3d, 7d and 14d. The 5 rats of each subgroup are tested forwater-content, Sodium, Potassium and examined with EM(two for everysubgroup with gamma knife, one in contral and sham radiationgroup).Other 5 rats in each subgroup were measured for EB-content.Results:1. Water-content of radiated brain tissue. 1) water-content in ratswith gamma knife is evidently higher than that of control, sham radiationgroup. It reached the peak at the 2nd day after radiation, and it was reduced at the 7th day and returned to normal at the 14th day(p＜0.05)Water-content is not significant on statistics between in control group andsham radiation group.2. Sodium concentration of radiated brain tissue:1) Sodiumconcentration in rats with gamma knife is evidently higher than that ofcontrol,sham radiation group. It reached the peak at the 2nd day afterradiation, and it reduced at the 7th day and returned to normal at the 14thday(p＜0.05).2). Sodium concentration is not significant on statisticsbetween in control group and sham radiation group.3. Potassium concentration of radiated brain tissue: 1) Potassiumconcentration in rats with Gamma knife is evidently lower than that ofcontrol, sham radiation group. It reached the peak at the 2nd day afterradiation, and it raised at the 7th day and retuned to normal at the 14thday (p＜0.05). 2). Potassium concentration is not significant on statisticsbetween in control group and sham radiation group.4. EB-content of radiated brain tissue: 1) EB-content in rats withgamma knife is evidently higher than that of control, sham radiationgroup. It reached the peak at the 2nd day after radiation, and it reduced atthe 7th day and 14th day(p＜0.05).2). EB-content is not significant onstatistics between in control group and sham radiation group.5. Pathological examination: radiated brain tissues in rats withgamma knife under EM were seen with edema around capillary and inglial cells, The change of edema was more seriously at the 2nd day afterradiation. It began to be dissolved at the 7th day and be eliminated at the14th day. 2). There were not significant changes in control group andsham radiation group. Conclusions:1. Acute brain edema was found in radiated brain tissues by gammaknife with 50 Gy, it reached the peak at the 2nd day after radiation, and itreduced at the 7th day and returned to normal at the 14th day(p＜0.05)2. Brain edema in radiated brain tissues was correlated with theconcentration of Sodium,Potassium and EB.Part 2: The change of expression of AQP4 in radiated rat brain aftergamma knife irradiation.Background and purposeAQP4 is located in H₂O channel in membrane of astrocyte axis, itplays an important role in H₂O trafficking thorough BBB and brainedema forming. AQP4 expressed lowly in normal brain tissues, but it ishighly in brain tissues with edema. The more brain edema is, and themore AQP4 expression is. However, it is not clear if brain edema iscaused by gamma knife, it is also not known what the process of brainedema is and if AQP4 expression increased. We tested the expression ofAQP4 in different time points after radiation with 50 Gy so as toinvestigate if the expression of AQP4 be related to radiation-inducedbrain edema, the process of acute brain edema and the mechanism ofearly radiation brain edema. Methods90 healthy adult SD rats were divided into control, radiation therapygroup with gamma knife and sham radiation group. Every group wasdivided into 6 subgroups in different time points, 12 hr, 1d, 2d, 3d, 7d and14d after decapitation. The 5 rats of each subgroup were examined forAQP4 expression with immunohistochemistry.Results:1. AQP4 was expressed in each time point after gamma knifeirradiation, it began to increase and reached the peak at the 2nd day, andthen reduced as the time was going on. It was evidently reduced at the14th day.2. The expression of AQP4 was not significant between in controland sham radiation group.3. The expression of AQP4 in radiation therapy group with gammaknife is higher than in control and sham radiation group at each timepoint.Conclusion1. The radiation with gamma knife produces the acuteradiation-induced brain edema.2. The expression of AQP4 can be induced by the irradiation ofgamma knife with 50Gy and reached the peak at the 2nd day. It wascorrelated with the course of acute radiation-induced brain edema.