伽玛刀照射大鼠前脑时小胶质细胞的反应

Alterations of microglia in forebrain of gamma knife irradiated rats

目的 本研究以小胶质细胞作为中枢神经系统对损伤反应和免疫防护的一种标志 ,在伽玛刀治疗仪中用不同剂量的伽玛射线照射正常大鼠前脑一侧尾壳核 ,探讨小胶质细胞与射线损伤的剂量 -效应关系 ,为伽玛刀的治疗剂量选择提供依据 .方法 以 OX42抗体作为检测小胶质细胞的标志 ,用免疫组织化学方法观察小胶质细胞在照射靶区及其周围组织的形态和数量变化 .结果 1低剂量 (10～ 30 Gy)射线照射时 ,小胶质细胞数目在照射侧增加 ,而对侧各组织阳性细胞数较少 ;2中剂量 (4 0～ 6 0 Gy)照射时 ,照射靶区 (尾壳核 )阳性细胞数目减少 ,且靶区及其周围组织出现活化小胶质细胞即胞体变大 ,形态多样 ,突起变短、少 ;3大剂量 (70～ 10 0 Gy)照射时 ,照射靶区出现坏死空洞 ,该空洞随剂量加大而增大 ,靶区及其周围组织水肿 ,且小胶质细胞变为吞噬细胞状并且胞体内可见吞噬颗粒 ,对侧脑中阳性细胞数目增多但形态上仍多为分枝状小胶质细胞 .结论 以上结果表明小胶质细胞是中枢神经系统损伤的敏感指标 ;靶区的损伤程度与照射剂量成正相关 ;

AIM To investigate the dose effect of gamma rays on microglia and to provide evidence for dosage selection of clinical treatment. METHODS Microglia, part of defensesystem of the CNS against injury, served as a signal by examining its changes after different dosage of gamma ray irradiation on unilateral caudate putamen nucleus of normal rats. Primary antibody OX42 was used to detect changes of morphology and the number of microglia in the irradiated target and its surrounding tissues. RESULTS At dose of 10～30 Gy, the number of microglia was increased remarkably in the ipsilateral side whereas the contralateral side displayed much fewer reactive cells. When irradiated with 40～60 Gy, microglia in the target tissue was reduced. But some activated microglia with hypertrophic cell body and fewer and shorter processes were seen in the target and its surrounding tissues. At dose of 70～100 Gy, necrotic hole began to appear and became bigger with dosage increasing. The target and nearby regions were swollen. Microglia manifested as phagocytic cells with recognizable particles in the cell bodies. In contrast, microglia in the contralateral side proliferated with the majority as ramified cells. CONCLUSION These results suggest that microglia is a sensitive marker for assessing CNS injury. The injury to target area is positively related to the radiation dosage. The morphology and the number of microglia in the surrounding tissues may vary with graded damage to the target area.