不同剂量移植小胶质细胞对阿尔茨海默病大鼠脑内β-淀粉样蛋白的作用

Different doses transplanted microglia effect on β-amyioid protein in rat Aizheimer＇s model

目的探索移植不同剂量小胶质细胞（MG）对阿尔茨海默病（AD）大鼠脑内β-淀粉样蛋白（Aβ）的作用。方法60只大鼠分实验组和对照组，于海马区分别注射Aβ-42和生理盐水，3d后经颈内动脉将不同剂量体外培养的持续表达增强型绿色荧光蛋白（EGFP）的小胶质细胞注入大鼠体内。注射后第3天进行Aβ荧光免疫组化染色，荧光显微镜观察各组海马区EGFP小胶质细胞和Ap的表达情况；RT-PCR检测各组大鼠脑内APP（A6前体蛋白）mRNA的相对表达情况。结果实验组各组EGFP平均荧光强度（5．62±0．61、8．85±0．33、10．24±0．45、11．26±0．37、12．75±0．65）明湿高于对照组（2.22±0．32，均P〈0．05）；荧光免疫组化娩示AB的平均荧光强度在实验组4×10^6剂量组（9．53±0．23）和12×10^6剂量组（8．32±0．46）明显高于8×10^6剂量组（4．56±0．13，均P〈0．05）；且Aβ与EGFP的荧光区存在部分一致性；RT—PCR显示实验组APPmRNA的相对表达量在实验组4×10^6剂量组（1．83±0．22）和12×10^6剂量组（1.94±0．28）明显高于8×10^6剂量组（0．43±0．12，均P〈0．05）。结论在AD中，A6有趋化MG的作用，MG可以吞噬Aβ；但大剂量的MG在对Aβ吞噬作用的同时加速了Aβ的形成。

Objective To explore the effects of different doses of transplanted microglia （MG） on β-amyloid protein （Aβ） in rat brain model of Alzheimer＇s disease （AD）. Methods A total of 60 SD rats were randomly divided into experimental group and control group. The experimental group was injected with Aβ-42 and the control group saline in hippocampus. At Day 3, different doses of continuously expressed enhanced green fluorescent protein （EGFP） microglial cells cultured in vitro were injected into the rats via carotid artery. At Day 3 post-injection, Aβ was labeled by immunofluoreseent method. And the expressions of EGFP microglia and Aβ were detected in hippocampus by fluorescence. The relative brain expression of β-amyloid precursor protein （APP） mRNA was analyzed by RT-PCR （reverse transeription-polymerase chain reaction ）. Results The mean fluorescent intensity of EGFP was significantly higher in each experimental group （5.62 ±0.61, 8.85 ±0.33, 10.24 ±0.45, 11.26 ±0.37, 12.75 ±0.65） than the control group （2. 22 ± 0. 32, all P 〈 0.05 ） ; Fluorescent immunohistochemistry showed that the mean fluorescent intensity of Aβ in the 4 × 10^6 dose group （9.53±0.23） and the 12 × 10^6 dose group （8.32 ±0.46 ） were significantly higher than that in the 8 × 10^6 dose group （4.56 ± 0.13, both P 〈 0.05 ） ; The fluorescent regions had partial consistence of EGFP and Aβ; RT-PCR （reverse transcription-polymerase chain reaction） results showed that the relative expressions of APP mRNA in the 4 ×10^6 dose group （ 1.83 ± 0.22） and the 12× 10^6 dose group （ 1.94 ± 0.28） were significantly higher than that in the 8 × 10^6 dose group （0.43 ±0.12, both P 〈 0.05 ）. Conclusion Aβ has the ehemotactic role of MG. MG may swallow Aβ protein partially. But a high dose of MG also accelerates the formation of Aβ.