Monitoring the perivascular cerebrospinal fluid dynamics of the glymphatic pathway using co-localized photoacoustic microscopy

Meningeal lymphatic drainage: novel insights into central nervous system disease

In recent years, increasing evidence has suggested that meningeal lymphatic drainage plays a significant role in central nervous system (CNS) diseases. Studies have indicated that CNS diseases and conditions associated with meningeal lymphatic drainage dysfunction include neurodegenerative diseases, stroke, infections, traumatic brain injury, tumors, functional cranial disorders, and hydrocephalus. However, the understanding of the regulatory and damage mechanisms of meningeal lymphatics under physiological and pathological conditions is currently limited. Given the importance of a profound understanding of the interplay between meningeal lymphatic drainage and CNS diseases, this review covers seven key aspects: the development and structure of meningeal lymphatic vessels, methods for observing meningeal lymphatics, the function of meningeal lymphatics, the molecular mechanisms of meningeal lymphatic injury, the relationships between meningeal lymphatic vessels and CNS diseases, potential regulatory mechanisms of meningeal lymphatics, and conclusions and outstanding questions. We will explore the relationship between the development, structure, and function of meningeal lymphatics, review current methods for observing meningeal lymphatic vessels in both animal models and humans, and identify unresolved key points in meningeal lymphatic research. The aim of this review is to provide new directions for future research and therapeutic strategies targeting meningeal lymphatics by critically analyzing recent advancements in the field, identifying gaps in current knowledge, and proposing innovative approaches to address these gaps.

Research Trends and Visualization of Cerebrospinal Fluid Dynamics (2013-2023)

OBJECTIVE

This study aims to analyze cerebrospinal fluid (CSF) dynamics using VOSviewer, CiteSpace, and the Bibliometrix R-package software to identify research hotspots and future directions.

METHODS

Search by Web of Science Core Collection Database for related literature on CSF dynamics from 2013 to 2023. Bibliometric and visual analysis of data on number of citations, number of publications, most productive countries and institutions, important authors and journals, time of publication, popular topics, and keywords were performed by CiteSpace and VOSviewer.

RESULTS

In the field of CSF dynamics, there is a clear upward trend in annual publications. The United States, Japan, and China are among the top three countries in publishing output. The University of Copenhagen, the University of Idaho, and the University of Zurich are leading institutions in research publications. The most prolific writers in this field are Bryn A. Martin, and Olivier Baledent. Active authors and institutions in the field form multiple structurally stable research teams with each other, but the collaboration between different authors and institutional teams needs to be further strengthened. The literature with the highest citation rates in the past decade is "Blood-Brain Barrier Breakdown in the Aging Human Hippocampus," "Blood-Brain Barrier Breakdown Is an Early Biomarker of Human Cognitive Dysfunction," "Serum Neurofilament Dynamics Predicts Neurodegeneration and Clinical Progression in Presymptomatic Alzheimer's Disease," and Coupled Electrophysiological, Hemodynamic, and Cerebrospinal Fluid Oscillations in Human Sleep." Key research keywords such as CSF, hydrocephalus, dynamics, brain, blood flow, CSF, pressure, CSF flow, and MRI highlight focal areas for CSF dynamics studies. These keywords represent current research priorities and research frontiers in this field.

CONCLUSIONS

This bibliometric analysis reveals hot and future research issues in the field of CSF fluid dynamics, demonstrating the need for enhanced international collaboration and interdisciplinary research to deepen the field. Keyword analysis further clarified the research focus and provided useful guidance for subsequent studies.

Advancing insights into in vivo meningeal lymphatic vessels with stereoscopic wide-field photoacoustic microscopy

Meningeal lymphatic vessels (mLVs) play a pivotal role in regulating metabolic waste from cerebrospinal fluid (CSF). However, the current limitations in field of view and resolution of existing imaging techniques impede understanding the stereoscopic morphology and dynamic behavior of mLVs in vivo. Here, we utilized dual-contrast functional photoacoustic microscopy to achieve wide-field intravital imaging of the lymphatic system, including mLVs and glymphatic pathways. The stereoscopic photoacoustic microscopy based on opto-acoustic confocal features has a depth imaging capability of 3.75 mm, facilitating differentiation between mLVs on the meninges and glymphatic pathways within the brain parenchyma. Subsequently, using this imaging technique, we were able to visualize the dynamic drainage of mLVs and identify a peak drainage period occurring around 20-40 min after injection, along with determining the flow direction from CSF to lymph nodes. Inspiringly, in the Alzheimer's disease (AD) mouse model, we observed that AD mice exhibit a ~ 70% reduction in drainage volume of mLVs compared to wild-type mice. With the development of AD, there is be continued decline in mLVs drainage volume. This finding clearly demonstrates that the AD mouse model has impaired CSF drainage. Our study opens up a horizon for understanding the brain's drainage mechanism and dissecting mLVs-associated neurological disorders.

Correction of high-rate motion for photoacoustic microscopy by orthogonal cross-correlation

Photoacoustic imaging is a promising technology for in vivo imaging. However, its imaging performance can be hampered by motion artifacts, especially when dealing with high-rate motion. In this paper, we propose an orthogonal motion correction method that utilizes cross-correlation along orthogonal scan directions to extract accurate motion displacements from the photoacoustic data. The extracted displacements are then applied to remove artifacts and compensate for motion-induced distortions. Phantom experiments demonstrate that the proposed method can extract the motion information and the structural similarity index measurement after correction is increased by 26.5% and 11.2% compared to no correction and the previous correction method. Then the effectiveness of our method is evaluated in vivo imaging of a mouse brain. Our method shows a stable and effective performance under high-rate motion. The high accuracy of the motion correction method makes it valuable in improving the accuracy of photoacoustic imaging.