Integrated Protocol for Assessing Meningeal Lymphatics: Cisterna Magna Injection, Lymph Node Imaging, Meningeal...

Meningeal lymphatic vessels (MLVs) have emerged as critical regulators of central nervous system (CNS) homeostasis, and MLVs dysfunction has been implicated in various neurological disorders. A comprehensive assessment of MLVs' morphology and function is therefore essential for understanding their role in CNS physiology and disease. This protocol describes an integrated method for evaluating MLVs in mice using four key techniques: Intra-cisterna-magna (i.c.m.) injection of fluorescent tracers, live imaging of cervical lymph nodes (CLNs), meningeal dissection, and whole-mount staining. First, the 30 G needle is connected to the syringe and infusion pump via a polyethylene (PE) tube. After the mouse is anesthetized, the dura mater is exposed by blunt dissection of the neck muscles, and the injection needle is inserted into the cisterna magna (CM) to deliver the tracer into the cerebrospinal fluid (CSF) with precise control. Tracer drainage to the CLNs can be visualized in real time, while subsequent meningeal dissection and whole-mount staining enable detailed morphological analysis of the dorsal MLVs. The entire procedure can be completed within 3 h, encompassing i.c.m. injection, tissue perfusion, skull isolation, and placement in fixative solution. This protocol can also be adapted for intracranial drug delivery or combined with molecular analyses, as the meningeal dissection procedure is compatible with fresh, unfixed tissues suitable for RNA and protein extraction.