轻度创伤性脑损伤大鼠海马学的高级扩散成像
Summary
这个程序的总体目标是获得轻度创伤性脑损伤大鼠海马的定量微结构信息。这是使用先进的扩散加权磁共振成像协议和基于兴趣区域的参数扩散图分析完成的。
Abstract
轻度创伤性脑损伤 (mTBI) 是最常见的后天性脑损伤类型。由于创伤性脑损伤患者表现出巨大的变异性和异质性(年龄、性别、创伤类型、其他可能的病理等),动物模型在解开临床研究中局限性的因素方面发挥着关键作用。它们提供了一个标准化和受控的设置,以研究损伤的生物机制和TBI后的修复。然而,并非所有动物模型都有效地模仿了mTBI的漫射和微妙特性。例如,常用的受控皮质撞击 (CCI) 和横向流体撞击损伤 (LFPI) 模型利用颅骨切除术暴露大脑并引起广泛的焦部创伤,这在 mTBI 中并不常见。因此,这些实验模型对模拟mTBI无效。因此,应该使用适当的模型来调查 mTBI。大鼠的Marmarou降重模型导致类似的微结构改变和认知障碍,如在轻度创伤患者中看到;因此,此模型是为此协议选择的。传统的计算机断层扫描和磁共振成像 (MRI) 扫描通常显示轻度损伤后没有损伤,因为 mTBI 通常只引起细微和漫反射性损伤。通过扩散加权MRI,可以研究脑组织的微观结构特性,从而更深入地了解轻度创伤后的微观变化。因此,本研究的目标是获得选定感兴趣区域(即海马区)的定量信息,以跟踪轻度和扩散性脑损伤后的疾病进展。
Introduction
创伤性脑损伤(TBI)近年来越来越受到关注,因为很明显,这些脑损伤会导致终生认知、身体、情感和社会后果。尽管这种意识的提高,轻度TBI(mTBI,或脑震荡)仍然经常被少报和未确诊。MTBI被称为无声流行病,有mTBI病史的个人表现出较高的药物滥用率或精神问题2。由于损伤的漫不经其道和微妙性质,每年有一些 mTBI 患者未确诊,这在传统的计算机断层扫描 (CT) 或磁共振成像 (MRI) 扫描中通常不可见。这种脑损伤的放射性证据的缺乏导致了更先进的成像技术的发展,如扩散核磁共振成像,后者对微结构变化更敏感3。
扩散MRI允许在体内绘制微结构图,这种MRI技术在TBI研究4、5、6中得到了广泛的应用。从扩散张量中,计算小数各向异性(FA)和平均扩散率(MD),以量化损伤后微结构组织的变化。最近对 mTBI 患者的检查报告 FA 增加,受伤后 MD 减少,这可能表明斧肿胀7。相反,MD 的增加和 FA 的减少也被发现,并已被建议在水肿形成、斧头退化或纤维失调/中断8之后,在帕伦奇结构中造成破坏。这些混合的发现可以部分解释为mTBI由不同类型的冲击和严重性(例如,旋转加速度、钝力创伤、爆炸损伤或前者的组合)造成的显著临床异质性。然而,目前对于支撑微观结构组织变化的基本病理学和生物/细胞基础没有明确的共识。
动物模型提供了一个标准化和受控的设置,以更详细地研究损伤的生物机制和TBI后的修复。已经开发了几种TBI实验模型,代表了人类TBI的不同方面(例如,焦点与漫射创伤或旋转力造成的创伤)9,10。常用的动物模型包括受控皮质冲击(CCI)和横向流体打击损伤(LFPI)模型11,12。虽然实验参数可以很好地控制,但这些模型利用颅骨切除术来暴露大脑。颅骨或颅骨骨折在 mTBI 中并不常见;因此,这些实验模型对模拟 mTBI 无效。Marmarou等人13开发的冲击加速模型利用了从一定高度掉落到大鼠头部的重量,该模型由头盔保护。这种动物模型诱导类似的微结构改变和认知障碍,如在患有轻度创伤的患者中。因此,这种马尔马鲁降重模型适用于研究漫射mTBI14、15的成像生物标志物。
本报告演示了使用Marmarou降重模型在mTBI大鼠模型中应用先进的扩散MRI。首先演示如何诱发轻度和漫反射性创伤,然后使用扩散张量成像(DTI)模型进行分析。使用更先进的扩散模型[即扩散峰度成像(DKI)和白质道完整性(WMTI)模型]获得特定的生物信息。具体来说,使用传统的T2加权MRI和先进的扩散成像方案,在海马区进行轻度创伤和微结构变化评估。
Protocol
Representative Results
Discussion
由于 mTBI 通常是扩散和细微损伤的结果,在 CT 和常规 MRI 扫描上没有异常,因此在轻度创伤后评估微结构损伤仍是一个挑战。因此,需要更先进的成像技术来可视化创伤的全部程度。扩散磁共振成像在TBI研究中的应用在过去十年中引起了更多的关注,其中扩散张量成像是最常用的5。DTI 模型的局限性是假设高斯扩散过程不是大脑微观结构的精确假设(由具有膜作为屏障的轴子和细胞组成…
Divulgations
The authors have nothing to disclose.
Acknowledgements
作者要感谢研究基金会 – 佛兰德斯(FWO)支持这项工作(授权号:G027815N)。
Materials
| Induction of trauma | |||
| 0.9% NaCl physiologic solution | B Braun | 394496 | |
| brass weight 450g | custom made | custom made | diamter 18mm and 210 mm height |
| catheter | Terumo | Versatus-W | 26G |
| ethilon II | Ethicon | EH7824 | FS-3, 4-0, 3/8, 16mm |
| Matrass | Foam to Size | Type E | |
| Plexiglas tube | ISPA Plastics | 416564 | M1 PMMA XT GOO tube 25×19 mm (inner diamter 19 mm, minimal length of 1.50 m) |
| Preclinical CT scanner | Molecubes | X-cube | |
| Steel helmet | custom made | custom made | diameter 10 mm and 3 mm thickness |
| Vetbond Tissue Adhesive | 3M | 1469SB | |
| Vetergesic (buprenorphin) | EcuPhar | VETERG20 | 0.05 mk/kg |
| Xylocaine 2% gel | AstraZeneca | Xylocaine 2% | gel |
| Xylocaine (lidocain 2%) | Aspen/AstraZeneca | Xylocaine 2% gel | 100 μl injection |
| Diffusion MRI | |||
| Preclinical MRI acquisition software | Bruker Biospin MRI GmbH | Z400_PV51_CENTOS55 | ParaVision 5.1 MRI software |
| Preclinical MRI scanner | Bruker Biospin MRI GmbH | PharmaScan 70/16 | 7T MRI scanner |
| Quadrature volume coil | Bruker Biospin MRI GmbH | RF RES 300 1H 075/040 QSN TR | Model No: 1P T13161C3 |
| Small animal physiological monitoring unit | Rapid Biomedical | EKGHR02-0571-043C01 | Unit for respiratory monitoring |
| Water-based heating unit | Thermo Fisher Scientific | Haake S 5P | Model No: 1523051 |
| Anaesthesia | |||
| Anaesthesia movable unit | Veterenary technics | BDO – Medipass, Ijmuiden | |
| isoflurane: Isoflo | Zoetis | B506 | |
| Oxygen generator | Veterenary technics | 7F-3 | BDO – Medipass, Ijmuiden |
| Diffusion image processing | |||
| Amide | http://amide.sourceforge.net | Version 1.0.5. | Medical Imaging Data Examiner Toolbox (Loening AM, Gambhir SS, " AMIDE: A Free Software Tool for Multimodality Medical Image Analysis", Molecular Imaging, 2(3):131-137, 2003) |
| ExploreDTI | http://www.exploredti.com | Version 4.8.6 | Toolbox for (pre-)processing and analysis of diffusion weighted MR images (Leemans A, Jeurissen B, Sijbers J, and Jones DK. ExploreDTI: a graphical toolbox for processing, analyzing, and visualizing diffusion MR data. In: 17th Annual Meeting of Intl Soc Mag Reson Med, p. 3537, Hawaii, USA, 2009) |
| MRtrix3 | http://www.mrtrix.org | Version 3.0_RC3-86-g4b523b41 | Toolbox for (pre-)processing and analysis of diffusion weighted MR images |
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