论文部分内容阅读
目的淀粉样前体蛋白(β-APP)是脑白质损伤早期敏感的指标,并参与缺氧缺血性脑损伤机制.本研究观察胎羊缺血性脑白质损伤及胰岛素样生长因子-1(IGF-1)治疗对淀粉样前体蛋白(β-APP)表达的影响.方法胎羊于胎龄117-124天(足月为147天)时通过双侧颈动脉阻塞30 min造成双侧脑缺血损伤,损伤后胎羊随机分为损伤组(n=8)和重组人IGF-1(rhIGF-1)治疗组(n=9);另设正常对照组(n=5),为假手术动物.治疗组缺血后90 min经侧脑室注射3μgrhIGF-1;损伤组经侧脑室注射等量人工脑脊液.缺血损伤后96 h结束实验,处死动物,取出胎羊,固定脑组织.免疫组化法检测脑白质胶质原纤维酸性蛋白(GFAP)、β-APP阳性细胞及白质内髓鞘碱性蛋白(MBP)密度.应用免疫荧光双标记观察APP表达阳性细胞.结果与正常对照组(27.8±4.8)比较,缺血损伤组MBP密度(4.7±7.1,P＜0.001)明显减少.正常对照组未见β-APP阳性细胞,损伤后阳性细胞数明显增加(49.6±23.7,P＜0.001),rhIGF-1治疗可减少β-APP阳性细胞数(17.9±16.5,P＜0.01).免疫荧光双标记显示部分细胞为β-APP-GFAP双标阳性细胞.结论胎羊缺血性脑白质损伤可导致星形胶质细胞表达β-APP,β-APP表达增加可能与脑损伤有关.IGF-1可减少β-APP表达,可能是减轻脑白质损伤的机制之一.“,”Objective β-amyloid precursor protein (β-APP) is thought to be a sensitive marker for brain white matter damage (WMD) and participates in the mechanisms of hypoxic-ischemic brain damage. This paper aims to study the influence of ischemia and IGF-1 treatment on the expression of β-APP in white matter of near-term fetal sheep.Methods Romney-Suffolk fetal sheep were instrumented at 117 to 124 days of gestation (term= 147 days). Reversible cerebral ischemia was induced by occlusion of bilateral carotid arteries for 30 mins. After damage the sheep were randomly divided into two groups: the Ischemic group ( n =8) and the IGF-1 treatment group (Treatment group, n = 9). The sham-operation group ( n = 5) was used as Control group. In the Treatment group, 3 μg( 1 ml) recombinant human IGF-1 (rhIGF-1) was infused into the left lateral ventricle, 90 mins after reperfusion. The Control group received infusion of 1 ml artificial cerebrospinal fluid into the left ventricle. Ninety-six hrs after ischemia, the sheep were sacrificed and the brains were fixed. Immunohistochemical staining was performed to assess glial fibrillary acidic protein (GFAP),β-APP positive cells and the myelin basic protein (MBP) density in the white matter. Fluorescent staining was performed for double labeling. Results The MBP density of the Ischemic group (4.7 ± 7.1) was significantly reduced as compared with the Control group (27.8 ± 4.8, P ＜0. 001). Β-APP positive cells were not observed in the Control group. Β-APP positive cells of the Ischemic group increased significantly after ischemia (49.6 ± 23.7, P ＜ 0.001). IGF treatment significantly reduced the β-APP positive cells (17.9 ± 16.5, P ＜ 0.01). Fluorescent double labeling showed that the β-APP positive cells were co-localized with GFAP positive cells. Conclusions Ischemia increases the expression of β-APP by astrocytes in near-term fetal sheep white matter, which may underlie the mechanisms of ischemic WMD. IGF-1can reduce the expression of β-APP, which may be mechanism of its protective effect against WMD.