Faculty of Medicine and Health Sciences, Macquarie University, Technology Place, Sydney, NSW, 2109, Australia.
Elsevier Inc, John F Kennedy Boulevard, Philadelphia, PA, 19103, USA.
Fluids Barriers CNS. 2019 Mar 26;16(1):7. doi: 10.1186/s12987-019-0127-8.
Fluid homeostasis in the central nervous system (CNS) is essential for normal neurological function. Cerebrospinal fluid (CSF) in the subarachnoid space and interstitial fluid circulation in the CNS parenchyma clears metabolites and neurotransmitters and removes pathogens and excess proteins. A thorough understanding of the normal physiology is required in order to understand CNS fluid disorders, including post-traumatic syringomyelia. The aim of this project was to compare fluid transport, using quantitative imaging of tracers, in the spinal cord from animals with normal and obstructed spinal subarachnoid spaces.
A modified extradural constriction model was used to obstruct CSF flow in the subarachnoid space at the cervicothoracic junction (C7-T1) in Sprague-Dawley rats. Alexa-Fluor 647 Ovalbumin conjugate was injected into the cisterna magna at either 1 or 6 weeks post-surgery. Macroscopic and microscopic fluorescent imaging were performed in animals sacrificed at 10 or 20 min post-injection. Tracer fluorescence intensity was compared at cervical and thoracic spinal cord levels between control and constriction animals at each post-surgery and post-injection time point. The distribution of tracer around arterioles, venules and capillaries was also compared.
Macroscopically, the fluorescence intensity of CSF tracer was significantly greater in spinal cords from animals with a constricted subarachnoid space compared to controls, except at 1 week post-surgery and 10 min post-injection. CSF tracer fluorescence intensity from microscopic images was significantly higher in the white matter of constriction animals 1 week post surgery and 10 min post-injection. At 6 weeks post-constriction surgery, fluorescence intensity in both gray and white matter was significantly increased in animals sacrificed 10 min post-injection. At 20 min post-injection this difference was significant only in the white matter and was less prominent. CSF tracer was found predominantly in the perivascular spaces of arterioles and venules, as well as the basement membrane of capillaries, highlighting the importance of perivascular pathways in the transport of fluid and solutes in the spinal cord.
The presence of a subarachnoid space obstruction may lead to an increase in fluid flow within the spinal cord tissue, presenting as increased flow in the perivascular spaces of arterioles and venules, and the basement membranes of capillaries. Increased fluid retention in the spinal cord in the presence of an obstructed subarachnoid space may be a critical step in the development of post-traumatic syringomyelia.
中枢神经系统（CNS）中的液体动态平衡对于正常的神经功能至关重要。蛛网膜下腔中的脑脊液（CSF）和 CNS 实质中的间质液循环可清除代谢产物和神经递质，并清除病原体和多余的蛋白质。为了理解包括创伤后脊髓空洞症在内的中枢神经系统液体紊乱，需要充分了解正常生理学。本项目旨在通过示踪剂的定量成像比较正常和阻塞性蛛网膜下腔脊髓中的液体转运。
在 Sprague-Dawley 大鼠颈胸交界处（C7-T1）硬膜外使用改良的外膜缩窄模型阻塞蛛网膜下腔中的 CSF 流动。在手术后 1 或 6 周将 Alexa-Fluor 647 卵清蛋白缀合物注入枕大池。在注射后 10 或 20 分钟处死动物，进行宏观和微观荧光成像。在每个手术后和注射后时间点，比较对照和缩窄动物颈椎和胸椎脊髓水平的示踪剂荧光强度。还比较了示踪剂在小动脉、小静脉和毛细血管周围的分布。
宏观上，与对照组相比，蛛网膜下腔狭窄动物的脊髓 CSF 示踪剂荧光强度明显更高，除了在手术后 1 周和注射后 10 分钟。手术后 1 周和注射后 10 分钟，狭窄动物的白质微观图像中的 CSF 示踪剂荧光强度明显更高。在缩窄手术后 6 周，在注射后 10 分钟处死的动物中，灰质和白质的荧光强度均显著增加。在注射后 20 分钟，这种差异仅在白质中显著，并且不那么明显。CSF 示踪剂主要存在于小动脉和小静脉的血管周围间隙以及毛细血管的基膜中，这突出了血管周围途径在脊髓中液体和溶质转运中的重要性。
蛛网膜下腔阻塞的存在可能导致脊髓组织内的液体流量增加，表现为小动脉和小静脉的血管周围间隙以及毛细血管的基膜中的流量增加。在蛛网膜下腔阻塞的情况下，脊髓中液体的保留增加可能是创伤后脊髓空洞症发展的关键步骤。
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