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 12 4天 (足月为 14 7天 )时通过双侧颈动脉阻塞 30min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 90min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 96h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 (2 7.8± 4 .8)比较 ,缺血损伤组MBP密度 (4.7± 7.1,P <0 .0 0 1)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± 2 3.7,P <0 .0 0 1) ,rhIGF 1治疗可减少 β APP阳性细胞数 (17.9± 16 .5 ,P <0 .0 1)。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

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.