检测AD的特异性核磁示踪剂USPIO-OA-Aβ42的实验研究

Amyloid plaques are a key pathological hallmark of Alzheimer’s disease (AD). The detection of amyloid plaques in the brain is important for the diagnosis of AD, as well as for following potential amyloid targeting therapeutic interventions. The aim of this research is to test nontoxic contrast agents with great specificity and sensitivity, capable of rendering reliable MR images upon Aβ in brains. In this study, we plan to use bifunctional ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, chemically coupled with Aβ1-42 peptide to image amyloid plaque deposition in the mouse brain, and moreover, coupled the nanoparticles to oleic acid (OA) in order to improve BBB permeability. Through the binding affinity and toxicity studies、in vivo & ex vivo MRI brain imaging、histological studies and Voxel-based analysis (VBA), we propose to establish the use of OAylated UPSIO coupled to a targeting peptide which binds to Aβ as a method for the specific detection of AD plaques using mMRI, in AD model mice without the use of any agent to increase the permeability of the BBB. Such a method of plaque detection will be helpful in the development and evaluation of potential novel therapeutic interventions to reduce amyloid deposits.

老年斑是阿尔茨海默病（AD）显著的病理生理特征，因此，建立脑内老年斑的早期检测方法并用以指导临床治疗措施的开发是非常迫切的。因目前尚无能够检测AD患者的特异性核磁示踪剂，老年痴呆的早期诊断及疗效的评价无法实现，本研究旨在制备一种无毒、特异性和敏感性良好的纳米微粒示踪剂, 可以探测AD沉积的Aβ，并能在MRI上清晰成像。本研究以Aβ同源多肽作为脑内β淀粉样蛋白的靶向物，以超小型顺磁性的氧化铁颗粒USPIO为显像剂，制备能够通过血脑屏障并能与Aβ特异性结合的核磁纳米微粒示踪剂。通过体内、外毒性实验、生物相容性实验及MRI成像检测鉴定该示踪剂无毒且可探测AD脑内沉积的Aβ，并能在MRI上清晰成像。本研究揭示该示踪剂作为分子影像的检测剂可以为今后AD早期诊断和评估疗效方面提供新的方法。

阿尔兹海默症(AD)是中老年人群中最常见的一种神经退行性疾病，因目前尚无能够检测AD患者的特异性核磁示踪剂，AD的早期诊断及疗效的评价无法实现。通过本项目，我们原创合成了造影剂PB@PEI@Mal-cys-Aβ42,并对其进行粒径和电位的表征，并进一步分析了紫外吸收峰、红外吸收峰，及MRI T1、T2的弛豫率。体内外实验均证实该示踪剂能够特异性结合Aβ，并具有较好的生物安全性。另外，AD大脑周细胞严重受损，但其机制并不清楚。我们通过体内外实验发现APP/PS1转基因鼠内血管周细胞受损的原因是Aβ40和Aβ42通过ERK1/2信号通路抑制了间充质干细胞向周细胞的分化(α-SMA, desmin, and PDGFRβ表达降低)，进而导致脑血管表面周细胞数量减少。项目资助发表SCI论文6篇，国内中文期刊2篇，专利1项；培养硕士2名，其中1名已经取得硕士学位，1名在读。项目投入经费21万元，支出21万元。各项支出基本与调整后预算相符。

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