Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Structural Preclinical Imaging, Medical University of Vienna & General Hospital of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria; Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria.
Department of Surgery, Division of Plastic & Reconstructive Surgery, Medical University of Vienna, Spitalgasse 23, 1090 Vienna, Austria.
J Inorg Biochem. 2021 Sep;222:111495. doi: 10.1016/j.jinorgbio.2021.111495. Epub 2021 May 29.
Amino-dextrans (AD) conjugated with gadolinium (Gd) were developed as neuro-specific contrast agents (CA) for the visualization of the sciatic nerve in rats by magnetic resonance imaging (MRI). AD with 3, 10, and 70 kDa molecular weights were assessed as carrier molecules known to be transported with various speed by axonal microtubules. Detailed spectroscopic characterizations, analyses by Fast Protein Liquid Chromatography (FPLC), Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), and inductively coupled plasma-mass spectrometry (ICP-MS), were carried out. For MRI, the paramagnetic Gd ion was coupled as a T1 signal enhancer. The well-established linear chelator, diethylenetriaminepentaacetic acid (DTPA), was used and subsequently replaced by the more stable cyclic chelator 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). In addition, a fluorescently labeled AD-DTPA-Gd was prepared to demonstrate an active transport to the spinal cord by histochemistry. After successful synthesis and characterization, molecular migration of the AD-DTPA-Gd in the sciatic nerve of healthy Sprague Dawley rats was monitored by MRI for up to seven days. Enhancement of nerve structures was evaluated by MRI and correlated with ICP-MS analyses. To investigate the distribution of CA along the neuraxis, all animals were sacrificed after the final MRI monitoring. Nerves, spinal ganglions, and corresponding spinal cord sections were harvested, to determine the localization and concentration of the paramagnetic element. This is the first report that demonstrates the active uptake and transport of AD-Gd conjugates within the sciatic nerve. This new concept may serve as a potential diagnostic tool for the direct visualization and monitoring of the continuity of injured nerves.
氨基酸葡聚糖（AD）与钆（Gd）偶联，开发为神经特异性对比剂（CA），用于通过磁共振成像（MRI）可视化大鼠坐骨神经。3、10 和 70 kDa 分子量的 AD 被评估为已知通过轴突微管以不同速度转运的载体分子。进行了详细的光谱特性分析、快速蛋白液相色谱（FPLC）分析、十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）和电感耦合等离子体质谱（ICP-MS）分析。对于 MRI，将顺磁 Gd 离子偶联作为 T1 信号增强剂。使用了成熟的线性螯合剂二乙三胺五乙酸（DTPA），随后被更稳定的环状螯合剂 1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸（DOTA）取代。此外，还制备了荧光标记的 AD-DTPA-Gd，以通过组织化学证明对脊髓的主动转运。成功合成和表征后，通过 MRI 监测 AD-DTPA-Gd 在健康 Sprague Dawley 大鼠坐骨神经中的分子迁移，持续长达七天。通过 MRI 评估神经结构的增强，并与 ICP-MS 分析相关联。为了研究 CA 在神经轴上的分布，所有动物在最后一次 MRI 监测后均被处死。收获神经、脊神经节和相应的脊髓切片，以确定顺磁元素的定位和浓度。这是首次报道证明 AD-Gd 缀合物在坐骨神经内的主动摄取和转运。这个新概念可能成为直接可视化和监测受损神经连续性的潜在诊断工具。
