The Glymphatic–Venous Axis in Brain Clearance Failure: Aquaporin-4 Dysfunction, Biomarker Imaging, and Precision Therapeutic Frontiers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript reviews the glymphatic–venous axis as an integrated system for brain waste clearance, with a focus on the role of AQ-4 in removing amyloid-β and tau. It aims to unify arterial, venous, and parenchymal mechanisms into a single framework to explain how clearance failure contributes to neurodegenerative diseases and to highlight its translational potential for diagnosis and therapy.

Major comments

• Abstract: At the end of the abstract, a sentence emphasizing the translational relevance to neurological and neurodegenerative diseases related to amyloid-β and tau clearance is missing. Currently, various techniques and therapies are listed, but it is not clearly stated how these findings impact the understanding or treatment of Alzheimer’s, Parkinson’s, or other disorders. I recommend adding 2–3 sentences linking the findings on the “glymphatic–venous axis” with the potential diagnostic and therapeutic implications for these pathologies.
• Figures: The figures are useful but overly schematic. I suggest redesigning them with anatomical illustrations so readers can easily identify the related anatomical pathways. This would significantly enhance their didactic and conceptual value.
• Length and synthesis of the manuscript: Although the topic is attractive, the manuscript is tedious and difficult to read due to its excessive length and repetitive content. I recommend condensing it substantially, shortening redundant paragraphs, and emphasizing the final subsection, which effectively underscores the article’s significance.

• In the subsection "Neuroinflammatory and Infectious Diseases," many examples are listed (meningitis, neurosyphilis, SARS-CoV-2) with repetitive descriptions; a single paragraph summarizing the concept and providing references would suffice.
• The subsection 8. Clinical implications across neurological… would be sufficient to describe the pathology and its association with subsection four briefly. Pathological failure of the glymphatic–venous axis. I suggest merging and integrating both into one concise section.

• Objective and novelty: The stated goal is: “Integrating arterial pushing, parenchyma pulling, venous regulating, and imaging scarring marks into a single overall model to provide a coherent narrative of the glymphatic–venous axis…”. However, throughout the manuscript, multiple examples and pathologies are presented without achieving a truly systematic integration or displaying a final unified model. I suggest:

• Adding a summary figure or table at the end illustrates how these four elements integrate into a single conceptual framework.
• Explaining in the introduction why this approach is novel compared to previous reviews.
• Writing the conclusion to emphasize the need for translational research and highlight where apparent knowledge gaps remain.

Minor comments

• Abstract: There is an unnecessary period at the end.
  • The term and definition of the “glymphatic–venous axis” are repeated excessively throughout the text.
  • Acronyms: Define all abbreviations at first mention.
  • Keywords: Reduce to 5–7, avoiding repetition of terms already present in the title.

Author Response

Dear Esteemed Academic Reviewer,

We are deeply grateful for your thoughtful and encouraging evaluation of our manuscript. Your detailed and constructive comments have been invaluable in improving both the structure and scientific clarity of our work. We are humbled by your recognition of the manuscript’s integrative ambition—to frame the glymphatic–venous axis as a unified system for brain clearance—and we are sincerely thankful for your guidance, which has helped us refine the text to better serve its educational and translational purpose.
Below, we address each of your comments point by point with our heartfelt appreciation.

Major Comments

Comment 1 — Abstract: Translational relevance to neurodegenerative diseases.
The abstract currently lists techniques and therapies but does not explicitly link them to translational implications for disorders such as Alzheimer’s or Parkinson’s disease.

Response:
We sincerely thank the reviewer for this insightful observation. In response, we have expanded the end of the Abstract to include two new sentences that explicitly link the glymphatic–venous framework to impaired amyloid-β, tau, and α-synuclein clearance. The revised text highlights how restoration of AQP4 polarity, venous compliance, and lymphatic drainage could open new diagnostic and therapeutic pathways for Alzheimer’s and Parkinson’s disease. This addition strengthens the translational significance of the manuscript, in full accordance with the reviewer’s helpful suggestion.

Comment 2 — Figures: Need for anatomical context.
The figures are overly schematic; anatomical illustrations would make the pathways clearer and enhance didactic value.

Response:
We are sincerely grateful for this excellent suggestion. We believe this change substantially enhances the manuscript’s readability and impact.

Comment 3 — Length and synthesis of the manuscript.
The manuscript is lengthy and occasionally repetitive; it should be condensed and refocused on its key integrative message.

Response:
We thank the reviewer for this valuable observation. The manuscript has been carefully condensed, with redundant passages removed and overlapping descriptions unified. In particular, Section 4 and Section 8  were thoroughly revised for greater concision and fluency. We preserved all mechanistic and translational insights while improving readability and narrative flow. These changes have shortened the manuscript by approximately 25%, yielding a more cohesive and accessible synthesis.

Comment 4 — Neuroinflammatory and Infectious Diseases subsection.
This subsection lists multiple examples with repetitive descriptions; it could be condensed into a single paragraph summarizing the concept.

Response:
We are thankful for this precise recommendation. The subsection on Neuroinflammatory and Infectious Diseases has been rewritten as a concise synthesis that integrates all examples—meningitis, neurosyphilis, SARS-CoV-2—into a single paragraph. The new text emphasizes the shared mechanism of inflammation-induced lymphatic obstruction and endothelial dysfunction, supported by the same reference set. This adjustment reduces redundancy while retaining scientific completeness.

Comment 5 — Integration of Sections 4 and 8.
The clinical implications could be summarized more concisely and related to the preceding mechanistic section.

Response:
We appreciate the reviewer’s careful reading and agree that Sections 4 and 8 benefit from stronger coherence. While we retained them as distinct sections to preserve their structural clarity, Section 8 has been fully rewritten to mirror the style and tone of Section 4, providing a fluent conceptual transition between mechanistic failure and clinical translation. The revised Section 8 is now compact, dense in evidence, and cross-referenced to Section 4 where relevant.

Comment 6 — Objective and novelty of the manuscript.
The stated goal is not fully realized; the introduction should clarify novelty compared with previous reviews, and the conclusion should highlight translational research needs and remaining gaps.

Response:
We are most grateful for this important and constructive guidance. The Introduction (Section 1.7) has been carefully rewritten to clarify the novelty of our approach in a measured and humble tone. It now explicitly distinguishes this review from prior work by emphasizing the integrative modeling of arterial inflow, parenchymal exchange, and venous–lymphatic outflow within one biomechanical framework.
Furthermore, the Conclusion has been expanded to underline the need for translational validation, identification of unresolved mechanistic uncertainties (such as human scaling and biomarker standardization), and the call for cross-disciplinary collaboration. These revisions bring the manuscript closer to the reviewer’s vision of a truly integrative and forward-looking synthesis.

Minor Comments

Abstract punctuation: The redundant period has been removed.

Term frequency: The expression glymphatic–venous axis has been used more sparingly; where appropriate, it has been replaced with synonyms such as brain clearance coupling or cerebrovascular–lymphatic system to improve stylistic variation.

Acronyms: All abbreviations are now defined at first mention.

Keywords: Reduced to six terms, avoiding repetition with the title.

 

We once again express our deepest gratitude to the reviewer for the careful, insightful, and generous feedback. Your suggestions have strengthened the manuscript’s conceptual integrity, clarity, and translational focus. We are sincerely appreciative of the time and expertise you invested in reviewing our work and for helping us present it in a form that we hope will be more useful and instructive to the scientific community.

With profound respect and appreciation!

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript by Daniel Costea is devoted to the mechanisms of brain clearance through the functioning of glymphatic–venous axis. The authors have describe the structure, molecular regulators of glymphatic–venous axis, the role of its pathology in neurodegenerative diseases, biomarkers and therapy based on glymphatic–venous axis as a target. The manuscript forms a comprehensive picture of the object of research. However, an impressive amount of work requires a significant improvement in the visibility of the features of the physiology, structure and functioning of lymphatic–venous axis considered by the authors. I recommend the authors to schematize the main aspects of the manuscript especially morphology and molecular mechanisms of lymphatic–venous axis and its failure in different pathologies.

Author Response

Dear Esteemed Academic Reviewer,

We are deeply grateful for your generous and thoughtful evaluation of our manuscript. Your kind words recognizing the scope of the work and your insightful recommendation regarding the visualization of the lymphatic–venous axis were truly appreciated. Your comment reflected a remarkable understanding of the field and encouraged us to refine both the structure and the clarity of the paper.

Comment:
The manuscript is comprehensive but would benefit from improved visibility of the physiological, structural, and molecular features of the lymphatic–venous axis. It is recommended to schematize the main aspects of morphology, molecular mechanisms, and pathological failure.

Response:
We sincerely thank the reviewer for this perceptive and valuable suggestion. In direct response, we have completely rebuilt Sections 4 and 8 to present a clearer, more integrated description of the morphology, physiology, and pathological failure of the lymphatic–venous coupling. These sections now convey the relationship between molecular mechanisms and clinical translation with improved coherence and visual support.

Additionally, we have redesigned Figure 2, which now serves as an anatomically and mechanistically grounded schematic illustrating periarterial influx, interstitial transport, perivenous drainage, and meningeal lymphatic outflow, together with the key molecular regulators and their dysfunction in disease. This revised figure markedly enhances the visibility of the system’s physiological architecture and its relevance across pathologies.

We are sincerely thankful for this constructive recommendation, which guided a meaningful and lasting improvement in the manuscript’s clarity and educational value. Your insight helped us transform these sections into a more cohesive and visually accessible representation of the glymphatic–venous system.

With profound respect and appreciation!