Recontextualizing Neuromyelitis Optica as a Systemic Condition: A Perspective
Round 1
Reviewer 1 Report (New Reviewer)
The manuscript generally summarized the non-CNS pathologies for NMOSD including muscular disorder, cancer, autoimmune diseases and others, which are broadly characterized and well-organized. It exhibits a new link between NMOSD and its associated diseases. Overall, it is a great perspective with the novelty and interest.
Minor:
Please include more searching details to the supplemental materials. For example, how many papers from 741 searching results were counted to this perspective, and the number of papers was grouped to category II-3, and the number of papers included in that higher than category II-3.
Author Response
We are grateful for your time in reviewing our manuscript. Your advice was very helpful and we have made the following changes to utilize it:
Revision 1: "Please include more searching details to the supplemental materials. For example, how many papers from 741 searching results were counted to this perspective, and the number of papers was grouped to category II-3, and the number of papers included in that higher than category II-3."
We appreciate your feedback in this regard and have added the line "This resulted in 62 articles used in this perspective." to the end of Paragraph 1 of the "Methods" section. We have also added two sentences to Paragraph 2 of the "Methods" section that state "Of the 62 articles used, two are considered Level III. The remaining articles are Level I through Level II-3."
Reviewer 2 Report (New Reviewer)
The authors described a perspective short review of Neuromyelitis optica spectrum disorder (NMOSD) with the involvement of anti-aquaporin-4 IgG (AQP4) transporter antibody on its pathology.
The authors have provided well-written research data on NMOSD. However, a few minor things have been suggested by Reviewer that are mentioned below-
The manuscript should be thoroughly rechecked as it seems to need improvisation of the English language and sentences.
Authors should revise Figure 2 in the form of Table in place of the figure.
Comments for author File: 
Comments.docx
The manuscript should be thoroughly rechecked as it seems to need improvisation of the English language and sentences.
Author Response
We are grateful for your time in reviewing our manuscript. Your advice was very helpful and we have made the following changes to utilize it:
Revision 1: "The manuscript should be thoroughly rechecked as it seems to need improvisation of the English language and sentences."
Thank you for inspecting our manuscript for proper English. We have conducted a thorough re-read and made minor changes to grammar in order to improve the linguistic aspects of the paper.
Revision 2: "Authors should revise Figure 2 in the form of Table in place of the figure."
We appreciate that you have noticed this error. It has been addressed and Figure 2 is now Table 1. Likewise, Figure 3 is now Figure 2, and in-text references to these figures and tables have been updated to reflect the changes.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
It is commendable that the authors have tried to find extra-CNS manifestations of NMOSD. Of all the conditions described, it is not surprising that other autoimmune diseases are seen in the context of autoimmunity. However, as with any retrospective review all the other associations are purely speculative and is only likely to confuse the readers further. To suggest that rhabdomyolysis causes NMOSD or NMOSD causes myotonic dystrophy is misleading and extremely dangerous. Proper scientific evaluation is needed before such speculations are published.
Author Response
To whom it may concern,
We greatly appreciate the efforts by the reviewers to provide useful, detailed feedback to help us improve our manuscript. Below, please find a point-by-point response to reviewers with our responses in bold and excerpts from our manuscript italicized. We feel that the efforts we have made warrant a re-review of our manuscript and greatly look forward to future correspondence.
We hope that these revisions clarify the intent of this literature review and eliminate appearances of unsubstantiated claims. We always welcome further feedback, as you may deem necessary. Thank you for your time and attention to our project.
Comment 1 - It is commendable that the authors have tried to find extra-CNS manifestations of NMOSD. Of all the conditions described, it is not surprising that other autoimmune diseases are seen in the context of autoimmunity. However, as with any retrospective review all the other associations are purely speculative and is only likely to confuse the readers further. To suggest that rhabdomyolysis causes NMOSD or NMOSD causes myotonic dystrophy is misleading and extremely dangerous. Proper scientific evaluation is needed before such speculations are published.
Response:
We greatly appreciate your candid feedback. As you note, it is difficult to draw definitive conclusions by way of a literature review. In order to clarify the purpose of this paper and to avoid the appearance of unsubstantiated speculation, the following changes were made:
The paragraph that stated:
"However, a case study in 2019 substantiates a connection between NMOSD secondary to rhabdomyolysis.25 The authors propose that tissue destruction secondary to rhabdomyolysis leads to the creation of anti-AQP4-IgG in the muscle. These anti-AQP4-IgG antibodies then precipitate the development of NMOSD (See Fig. 1). Another case study demonstrated the second known occurrence of myotonic dystrophy type 2 secondary to NMOSD, though the authors state the coexistence could be coincidental.26 However, this relationship should be reexamined in the light of emerging evidence that demonstrates a relationship between NMOSD and muscular disorders."
was changed to state:
"However, a case study in 2019 substantiates a connection between NMOSD secondary to rhabdomyolysis.25 The authors propose that tissue destruction secondary to rhabdomyolysis leads to the creation of anti-AQP4-IgG in the muscle. These anti-AQP4-IgG antibodies then precipitate the development of NMOSD (See Fig. 1). Another case study demonstrated the second known occurrence of myotonic dystrophy type 2 secondary to NMOSD, though the authors state the coexistence could be coincidental.26 It is difficult to determine from these studies whether or not there is a substantial or causal link between the conditions described and NMOSD. However, this relationship should be reexamined in the light of emerging evidence that demonstrates a relationship between NMOSD and muscular disorders."
Also, the conclusion was edited so that the final sentence states:
"Future studies, such as a bioinformatic correlational analysis, should be done to provide more tangible evidence of observed associations."
Again, we appreciate the time of the reviewers and editorial team and look forward to hearing from you regarding our submission and we are happy to respond to any further questions and comments you may have!
Sincerely,
Parker Webber
Reviewer 2 Report
The paper deals with the interesting issue of looking at neuromyelitis optica as a systemic condition. It is known that autoimmune diseases never involve only one system and the search for possible involvement of other organs and systems is very important.
However interesting the paper is, it requires several additions and corrections before it is accepted for publication:
1. there should be no references in the abstract - please remove this
2. key words are missing
3. search strategies should be completed - how many articles qualified for the final analysis, how many were found initially, what were the exclusion criteria and how many were excluded
4. the introduction should be supplemented with a few sentences about the current state-of-the-art treatments for NMODS that may give systemic complications based on: https://pubmed.ncbi.nlm.nih.gov/33802046/
5. conditions can be supplemented by linking NMO to infections that worsen the course of the disease, for example:
https://pubmed.ncbi.nlm.nih.gov/35158468/
https://pubmed.ncbi.nlm.nih.gov/29454471/
Author Response
To whom it may concern,
We greatly appreciate the efforts by the reviewers to provide useful, detailed feedback to help us improve our manuscript. Below, please find a point-by-point response to reviewers with our responses in bold and excerpts from our manuscript italicized. We feel that the efforts we have made warrant a re-review of our manuscript and greatly look forward to future correspondence
Comment 1 - there should be no references in the abstract - please remove this
Response: Thank you for your response and your suggested revisions. We have removed the references from the abstract.
Comment 2 - Key words are missing
Response: Thank you for bringing this error to our attention. We have added the following keywords at the end of the abstract:
“Keywords: neuromyelitis optica spectrum disorder (NMOSD); aquaporin-4 (AQP4); paraneoplastic diseases; autoimmune disorders”
Comment 3- Search strategies should be completed - how many articles qualified for the final analysis, how many were found initially, what were the exclusion criteria and how many were excluded.
Response: Thank you for this observation. The following was added to the Methods section to address this:
“741 results were generated. Results that did not address the nature of NMOSD as an AQP-4 disease or that did not provide examples of symptoms outside of the CNS were excluded. Only articles in English in the last 10 years were included, with the exception of fundamental disease characterizations.”
Comment 4- The introduction should be supplemented with a few sentences about the current state-of-the-art treatments for NMODS that may give systemic complications based on: https://pubmed.ncbi.nlm.nih.gov/33802046/
Response: We appreciate your effort in improving our review by broadening the scope of view on NMOSD. It has increased the completeness of our project. We added the following paragraph near the end of the Background section based on the reference you provided:
“Recent advancements in NMOSD treatment have made great strides in improving our knowledge of potential therapeutic modalities to treat patients suffering from this debilitating disease. One example is the transition from immunosuppression to targeted treatments for NMOSD-specific elements of the autoimmune cascade. Another example is the greater emphasis on discovering and utilizing evidence-based therapeutic modalities rather than “off-label” adaptations.”
Alongside this paragraph, 3 other sources were cited to further deepen the discussion around NMOSD treatment at the suggestion of another reviewer. We feel that these combined additions have helped to make our paper more complete and useful to your readership.
Comment 5: conditions can be supplemented by linking NMO to infections that worsen the course of the disease, for example:
https://pubmed.ncbi.nlm.nih.gov/35158468/
https://pubmed.ncbi.nlm.nih.gov/29454471/
Response: We are very grateful for your provision of even further research regarding NMOSD complications occurring outside of the CNS. We feel that the following additions in the Other section utilizing both references you provided have improved the depth of our research and have addressed your recommendations.
“A systematic review performed from 2019 to 2021 provides strong evidence to suggest that patients with NMOSD are more susceptible to COVID-19 and have worse outcomes. The most significant risk factor appears to be pre-existing treatment of NMOSD with rituximab, therefore clinicians should bear this in mind as they develop treatment plans for their patients with NMOSD.
A case report from 2018 details the disease course of a pregnant female patient with Hepatitis C who subsequently developed NMOSD. Because of her pregnancy and the complicated status of her Hepatitis C, she was unable to be treated using the typical therapeutic modalities. This resulted in a more severe disease course. This report, along with the systematic review mentioned in the previous paragraph, suggest that improvements in NMOSD treatment—particularly for those with comorbidities—should be sought after.”
Again, we appreciate the time of the reviewers and editorial team and look forward to hearing from you regarding our submission and we are happy to respond to any further questions and comments you may have!
Sincerely,
Parker Webber
Reviewer 3 Report
Dear Editor,
The manuscript by Webber et al. discusses the current understanding and recent advances for the neuromyelitis optica as a systemic condition and the essential role of aquaporins (particularly AQP4) in its pathology.
The work is comprehensive, informative, nicely-written, timely and up-to-date (in most parts). Author was successful in providing some well compiled opinions and summaries.
However, there is a number of major and minor points that would need to be addressed in order to improve the quality of this paper before it can be accepted for publication.
General:
- This work overlooked some essential and up-to-date work regarding the recent advances in AQP target validation and future therapies. I have made some suggestions below but author is encouraged to consider citing updated references throughout the work, whenever possible.
Major:
-AQPs are historically known to be passive transporters of water. Lines of evidence in the last decade have highlighted the diverse function of AQPs beyond water homeostasis. Authors need to cover this point. A reference to be included:
https://www.ncbi.nlm.nih.gov/pubmed/26365508
Moreover, a subgroup of AQP water channels also facilitates transmembrane diffusion of small, polar solutes not only water; aquaglyceroporin. References to be included:
https://www.ncbi.nlm.nih.gov/pubmed/16715408
https://www.ncbi.nlm.nih.gov/pubmed/31889130
-The increased AQP expression and the redistribution/surface localization can be two different concepts. For example, previous studies have shown an increased in AQP4 membrane localisation in primary human astrocytes which wasn’t accompanied by a change in AQP4 protein expression levels. This mislocalization can be a potential therapeutic target. References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765450/
https://www.ncbi.nlm.nih.gov/pubmed/31242419
https://pubmed.ncbi.nlm.nih.gov/26013827/
-The authors omit a key study from Kitchen et al 2020 demonstrating that the development of edema following injury-induced hypoxia is AQP4 dependent. That study shows that CNS edema is associated with increases both in total aquaporin-4 expression and aquaporin-4 subcellular translocation to the blood-spinal-cord-barrier (BSCB). Pharmacological inhibition of AQP-4 translocation to the BSCB prevents the development of CNS edema and promotes functional recovery in injured rats.
This role has been recently been confirmed by the work of Sylvain et al BBA 2021 which has demonstrated that targeting AQP4 effectively reduces cerebral edema during the early acute phase in in stroke using photothrombotic stroke model. They have also shown a link to brain energy metabolism as indicated by the increase of glycogen levels. References to be included:
https://www.cell.com/cell/fulltext/S0092-8674(20)30330-5.
https://pubmed.ncbi.nlm.nih.gov/33561476/
-AQPs have been validated as an important drug target but there is no single drug that has yet been approved to successfully target it. This needs to be mentioned as it highlights the importance for studies similar to the current one by providing alternative routes of targeting AQP function compared to the traditional pore-blocking approach. References to be included:
https://pubmed.ncbi.nlm.nih.gov/34863533/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6480248/
Based on the above and towards the end of discussion, authors need to discuss recent trends in targeting the molecular and signalling mechanisms of AQPs rather than just the traditional approaches. The importance of this new approach has been discussed in these references which should be included to enrich the discussion of current manuscript. References:
https://pubmed.ncbi.nlm.nih.gov/34973181/
https://www.mdpi.com/1422-0067/23/3/1388
Minor:
- Authors are encouraged to briefly discuss future directions following towards the end of their discussion and conclusion. This could include, but not limit to, the use of humanized self-organized models, organoids, 3D cultures and human microvessel-on-a-chip platforms especially those which are amenable for advanced imaging such as TEM and expansion microscopy since they enable real-time monitoring of AQP4 dynamics. References to be included:
https://pubmed.ncbi.nlm.nih.gov/33117784/
https://pubmed.ncbi.nlm.nih.gov/30165870/
-NMOSD is yet incurable diseases. Author needs to point out to the recent advances in applying the use of high-throughput screening and computer-aided drug design as have been nicely reviewed by Aldewachi et al 2021 as they can provide a novel insight that can support AQP target validation in future studies. References to be included:
https://pubmed.ncbi.nlm.nih.gov/33925236/
https://pubmed.ncbi.nlm.nih.gov/33672148/
Best.
Author Response
To whom it may concern,
We greatly appreciate the efforts by the reviewers to provide useful, detailed feedback to help us improve our manuscript. Below, please find a point-by-point response to reviewers with our responses in bold and excerpts from our manuscript italicized. We feel that the efforts we have made warrant a re-review of our manuscript and greatly look forward to future correspondence.
Comment 1-AQPs are historically known to be passive transporters of water. Lines of evidence in the last decade have highlighted the diverse function of AQPs beyond water homeostasis. Authors need to cover this point. A reference to be included:
https://www.ncbi.nlm.nih.gov/pubmed/26365508
Moreover, a subgroup of AQP water channels also facilitates transmembrane diffusion of small, polar solutes not only water; aquaglyceroporin. References to be included:
https://www.ncbi.nlm.nih.gov/pubmed/16715408
https://www.ncbi.nlm.nih.gov/pubmed/31889130
Response: Thank you for your time and effort in reviewing our submission. Your feedback regarding more complete descriptions of AQP4 channels was greatly appreciated. The following has been added to the first paragraph of the Background section to incorporate the references you provided:
“The main fluid that aquaporin channels transport is water; however, research has also demonstrated their role in transporting substances such as glycerol, urea, and potentially some gases and ions.”
Comment 2:-The increased AQP expression and the redistribution/surface localization can be two different concepts. For example, previous studies have shown an increased in AQP4 membrane localisation in primary human astrocytes which wasn’t accompanied by a change in AQP4 protein expression levels. This mislocalization can be a potential therapeutic target. References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765450/
https://www.ncbi.nlm.nih.gov/pubmed/31242419
https://pubmed.ncbi.nlm.nih.gov/26013827/
Response: We greatly appreciate your feedback that has helped us improve our submission by developing a more complete Background to help readers understand AQP channels. We have incorporated the first and third references you recommended in this comment in the second paragraph of the Background section as follows:
“The pathogenesis of AQP4 diseases is complex. Within the last decade alone, researchers have identified various ways in which AQP4 expression and distribution change, due to physiologic and pathologic processes. When astrocyte tonicity was altered in rats, it was found that cell surface expression of AQP4 subsequently adapted to compensate. When human astrocytes were cultured at hypothermic and normothermic conditions, ELISA analysis demonstrated that the hypothermic conditions elicited an increase in surface expression of AQP4, suggesting the human body’s capacity to alter AQP4 expression to accommodate various physiologic states.”
We also incorporated the second reference you recommended in this comment in the third paragraph of the Background section as follows:
“Recent research has demonstrated that these anti-AQP4 antibodies target primary cortical astrocytes (see Fig. 1) and disrupt the ability of these AQP4 channels to redistribute in response to changes in their environment.”
Comment 3-The authors omit a key study from Kitchen et al 2020 demonstrating that the development of edema following injury-induced hypoxia is AQP4 dependent. That study shows that CNS edema is associated with increases both in total aquaporin-4 expression and aquaporin-4 subcellular translocation to the blood-spinal-cord-barrier (BSCB). Pharmacological inhibition of AQP-4 translocation to the BSCB prevents the development of CNS edema and promotes functional recovery in injured rats.
This role has been recently been confirmed by the work of Sylvain et al BBA 2021 which has demonstrated that targeting AQP4 effectively reduces cerebral edema during the early acute phase in in stroke using photothrombotic stroke model. They have also shown a link to brain energy metabolism as indicated by the increase of glycogen levels. References to be included:
https://www.cell.com/cell/fulltext/S0092-8674(20)30330-5.
https://pubmed.ncbi.nlm.nih.gov/33561476/
Response: Thank you for bringing these important studies to our attention. They have provided valuable information that has helped strengthen the portions of our paper addressing treatment modalities. Another reviewer also suggested several articles which have also been incorporated in our paper. To address these specific references you provided, we added the following to the second paragraph of the Background section, following descriptions of other related research:
“For example, hypoxia induces calmodulin-driven increases in AQP4 cell-surface localization.”
And the following to the fourth paragraph of the Background section:
“Recent advances have also demonstrated that it is possible to target the subcellular relocalization functions of AQP4, such as with the calmodulin-inhibiting antipsychotic drug, trifluoperazine.”
Comment 4 -AQPs have been validated as an important drug target but there is no single drug that has yet been approved to successfully target it. This needs to be mentioned as it highlights the importance for studies similar to the current one by providing alternative routes of targeting AQP function compared to the traditional pore-blocking approach. References to be included:
https://pubmed.ncbi.nlm.nih.gov/34863533/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6480248/
Based on the above and towards the end of discussion, authors need to discuss recent trends in targeting the molecular and signalling mechanisms of AQPs rather than just the traditional approaches. The importance of this new approach has been discussed in these references which should be included to enrich the discussion of current manuscript. References:
https://pubmed.ncbi.nlm.nih.gov/34973181/
https://www.mdpi.com/1422-0067/23/3/1388
Response: Thank you for providing so many references in this comment. All of them were found to be quite insightful. Based on our incorporation of previous references you had provided, as well as references provided by another reviewer, we felt that we have adequately addressed the emerging treatment modalities. The following was added to the fourth paragraph of the Discussion section to ensure that the readers are made aware of the importance of these treatments in understanding AQP4 diseases:
“Fortunately, increasing interest in treating AQP4 diseases has encouraged increased investigation into therapeutic modalities that may go beyond current conventional treatments. The research is still relatively new, and much has yet to be understood, therefore greater resources should be dedicated to researching and reconsidering therapeutic approaches to AQP4 diseases such as NMOSD.”
Comments 5 and 6 - Authors are encouraged to briefly discuss future directions following towards the end of their discussion and conclusion. This could include, but not limit to, the use of humanized self-organized models, organoids, 3D cultures and human microvessel-on-a-chip platforms especially those which are amenable for advanced imaging such as TEM and expansion microscopy since they enable real-time monitoring of AQP4 dynamics. References to be included:
https://pubmed.ncbi.nlm.nih.gov/33117784/
https://pubmed.ncbi.nlm.nih.gov/30165870/
-NMOSD is yet incurable diseases. Author needs to point out to the recent advances in applying the use of high-throughput screening and computer-aided drug design as have been nicely reviewed by Aldewachi et al 2021 as they can provide a novel insight that can support AQP target validation in future studies. References to be included:
https://pubmed.ncbi.nlm.nih.gov/33925236/
https://pubmed.ncbi.nlm.nih.gov/33672148/
Response: We greatly appreciate your recommendation to incorporate a more thorough discussion of emerging modalities. In the interest of remaining succinct, we have addressed comments 5 and 6 jointly in the fifth paragraph of the Background section as follows:
“Improvements in technology have also facilitated breakthroughs in our understanding of AQP4 diseases. Of note, Computer-aided Drug Design (CADD) and high-throughput screening platforms have enabled researchers to be far more efficient in screening compounds that do or do not have potential applications for their specific projects. Similarly, two novel devices termed “human blood-brain-barrier on-a-chip" and “human brain endothelial microvessel-on-a-chip" have allowed greater capacity to test pharmaceuticals in a model resembling the human blood-brain-barrier.”
Again, we appreciate the time of the reviewers and editorial team and look forward to hearing from you regarding our submission and we are happy to respond to any further questions and comments you may have!
Sincerely,
Parker Webber
Round 2
Reviewer 2 Report
Accept in present form.
Reviewer 3 Report
Dear Editor,
The authors have successfully addressed the majority of my comments and concerns in order to improve the quality of the manuscript.
I believe that the new sections, improved ones, and updated references, have contributed to enhancing the clarity of the manuscript, which I can now endorse for publication.
All the best!
