Interaction between glymphatic and vascular systems for waste clearance in brain

摘要 该应用程序的目标是首先开发和验证整个大脑的微血管测量 利用增强的超顺磁性氧化铁(SPIO)将微血管的检测灵敏度提高10倍 磁化率加权成像(SWI，SPIO-SWI)，然后研究淋巴和 糖尿病大脑中清除废物的血管系统。新出现的数据表明，淋巴系统 在大脑中，介导脑脊液(CSF)-间质(ISF)交换和脑内溶质清除 脑实质，在神经系统疾病中起着重要作用。尽管取得了许多里程碑式的成就， 关于溶质外流途径的结论相对有限。因此，两国之间的互动 血管和淋巴系统对废物清除的影响，特别是在患有神经系统疾病的情况下，尚不清楚。 对外流途径研究的匮乏可能部分归因于技术困难，如 具有挑战性的需要进行微创的体内，超高检测灵敏度的管状流入和 外流途径和全脑成像。虽然磁共振成像可以克服双光子共聚焦的弱点 显微镜提供非侵入性的全脑活体淋巴系统成像，常规MRI 对于所需的空间分辨率而言，灵敏度不足以研究淋巴微血管和 血管系统。我们已经开发出高灵敏度的MRI方法(图1)，这些方法显著改善了 磁共振剂的高敏感性结合水华检测小血管的敏感性 效果7-9。新方法为研究废物清除的外流途径提供了极好的工具。 在正常和病理生理条件下。最近提出了三种外流途径和解决方案 可以通过嗅球穿过筛板10、11到达淋巴网络或通过功能 脑膜中的常规淋巴管系统12。我们发现静脉系统中的示踪剂浓度 随着糖尿病的发生显著增加(图9)，从而增加了一条清除脑废物的新途径。基于我们的 新的初步数据和其他人发表的研究，我们假设，新开发的SPIO-SWI 该技术显著提高了血管和淋巴系统中微血管的检测灵敏度， 糖尿病患者和非糖尿病患者的排泄物排出途径可以用以下方法识别和研究 这种优化的SPIO-SWI方法。为了检验这些假设，我们将首先(目标1)进一步开发、优化和 验证SPIO-SWI技术可提高血管和淋巴的检测灵敏度 微血管。我们将进行计算机模拟，优化SWI技术和实验条件 动物实验，然后通过激光共聚焦显微镜测量验证USPIO-SWI技术。然后我们将(目标2) 糖尿病脑内废物清除中血管和淋巴系统相互作用的研究 优化的USPIO-SWI技术。此应用程序生成的数据将提供有关外流的新见解 糖尿病脑中淋巴系统和血管系统之间的通路。

ABSTRACT The objective of this application is to first develop and validate microvessel measurement for the entire brain to enhance detection sensitivity of microvessels by ten-fold using superparamagnetic iron oxide (SPIO) enhanced susceptibility weighted imaging (SWI, SPIO-SWI) and then to investigate the interaction between glymphatic and vascular systems for waste clearance in the diabetic brain. Emerging data indicate that the glymphatic system in the brain mediates the cerebrospinal fluid (CSF)-interstitial (ISF) exchange and solute clearance from the brain parenchyma and plays an important role in neurological diseases1-6. Despite many milestone achievements, conclusive findings on the solute efflux pathways are relatively limited. Consequently, the interaction between vascular and glymphatic systems on waste clearance, especially with neurological diseases, is unclear. The paucity of research into the efflux pathway may be attributed in part to technical difficulties, such as the challenging need to perform minimally invasive in-vivo, ultra-high detection sensitivity for tube-shaped influx and efflux pathways, and whole brain imaging. Although MRI can overcome the weak points of two-photon confocal microscopy to provide non-invasive whole brain in-vivo imaging of the glymphatic system, conventional MRI sensitivity is insufficient for the required spatial resolution for investigating microvessels of glymphatic and vascular systems. We have developed highly sensitive MRI methods (Fig. 1) which significantly improve the detection sensitivity of small vessels by using the combination of high susceptibility of MRI agents with blooming effects7-9. The new methods provide excellent tools for investigating the efflux pathways of waste clearance under normal and pathophysiological conditions. Three efflux routes have been recently proposed and solutes in the brain could reach the lymphatic network by the olfactory bulb across the ethmoid plate10, 11 or by functioning conventional lymphatic vasculature in the meninges12. We found that tracer concentration in the venous system significantly increased with diabetes (Fig. 9), thus adding a new route for brain waste clearance. Based on our novel preliminary data and published studies by others, we hypothesize that, the newly developed SPIO-SWI technique significantly increases detecting sensitivity of microvessels in both vascular and glymphatic systems, and the efflux pathways of waste clearance with and without diabetes can be identified and investigated using this optimized SPIO-SWI method. To test these hypotheses, we will first (Aim 1) further develop, optimize and validate SPIO-SWI techniques to enhance the detection sensitivity for both vascular and glymphatic microvessels. We will perform computer simulation, optimize SWI technique and experimental conditions in animal studies and then validate USPIO-SWI technique by LSCM measurements. We will then (Aim 2) investigate the interaction between vascular and glymphatic systems for waste clearance in diabetic brain using the optimized USPIO-SWI technique. Data generated from this application will provide new insights into the efflux pathways between glymphatic and vascular systems in diabetic brain.