Urinary Astrocyte-derived Extracellular Vesicles: A Non-invasive Tool for Capturing Human In Vivo Molecular "Movies" of Brain

The identification of particularly individual-level biomarkers, for certain central nervous system (CNS) diseases remains challenging. A recent approach involving the enrichment of brain-derived extracellular vesicles (BDEVs) from peripheral blood has emerged as a promising method to obtain direct in vivo CNS data, bypassing the blood-brain barrier. However, for rapidly evolving CNS diseases (e.g., weeks or even days), the Nyquist-Shannon sampling theorem dictates the need for a high-frequency sampling rate. Obviously, daily collection of blood or cerebrospinal fluid from human subjects is impractical. Thus, we innovated a novel method to isolate astrocyte-derived EVs from urine (uADEVs). It involves three main steps: 1) concentrating urine samples, 2) isolating total EVs from urine (uTEVs) using ultracentrifugation, and 3) using an anti-glutamate/aspartate transporter (GLAST) antibody to isolate GLAST+EVs from uTEVs. Subsequently, we confirmed the identity of these GLAST+EVs as uADEVs using transmission electron microscopy, nanoparticle tracking analysis, western blotting, and the measurement of astrocyte-related neurotrophins. Furthermore, we applied the uADEVs protocol to depict the detailed trajectory of the N-methyl-d-aspartic acid receptor (NMDAR) subunit zeta-1 (GluN1) in an anti-NMDAR encephalitis patient, demonstrated the potential of this method for capturing intricate trajectories of CNS-specific molecular in vivo signals at the individual level. This non-invasive approach enables frequent sampling, up to daily or even half-daily, analogous to capturing molecular "movies" of the brain, coupled with appropriate signal processing algorithms, holds promise for identifying novel biomarkers or illuminating the etiology of rapidly evolving CNS diseases by tracking the precise trajectories of target molecules. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by grant from the National Natural Science Foundation of China (grant number: U21A20364). This work has not received funding/assistance from any commercial organizations. The funding source had no roles in the design of this study and will not have any roles during the execution, analyses, interpretation of the data, or decision to submit results. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was approved by both the Human Ethics Committee of Renmin Hospital of Wuhan University and Wuhan First Hospital. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data were presented in the Supplementary Material.