Stem Cell Scaffolds for the Treatment of Spinal Cord Injury—A Review

Round 1

Reviewer 1 Report

This manuscript reviewed the scaffolds encapsulated with stem cells for the treatment of SCI. Here are some questions:

1. How to use the scaffolds in animal models?
2. Several pathways regulate the differentiation process. How do the scaffolds modulate the pathways?
3. In section 3 “Substrates Indicated for Axonal Regrowth”, how does the substrate regulate axonal regrowth? 2D or 3D?
4. How to monitor cell differentiation in scaffolds?

N.A.

Author Response

Response to Review 1 Comments

Point 1: Asked how stem cell scaffolds for SCI are used in animal models.

Response 1: The use of stem cell scaffolds for animal models is outlined in section 5, titled “Emerging Pre-Clinical Studies and Their Applications for Clinical Adoption. To make this section clearer, all animal studies have been identified by stating in the sentence what animal model the scaffolding modality was used in. Additionally, this information is included in Table 1 and Table 2.

Point 2: Asked how stem cell scaffolds modulate cell differentiation pathways.

Response 2: There appears to be a gap in the literature regarding how stem cell scaffolds for SCI modulate various NSC differentiation pathways. To address this, we have included an additional paragraph discussing this discrepancy in section 6 titled “Conclusion and Future Research Directions”. We have indicated this as a future research direction.

Point 3: Asked to clarify whether section 3 titled “Substrates Indicated for Axonal Regrowth” talks about axonal regrowth in a 2D or 3D manner.

Response 3: To clarify this, we have indicated that section 3 talks about axonal regrowth in a 3D manner. We have changed the first sentence to read “Three-dimensional (3D) axonal regrowth is a complex process that occurs after an injury involving multiple genes, signaling molecules, proteins, and extracellular environment components”.

Point 4: Asked how to monitor cell differentiation in scaffolds.

Response 4: Similar to point/response 2, there appears to be a gap in the literature regarding how to monitor cell differentiation in scaffolds specifically for SCI. To highlight this lack of evidence, we have included this as a future research direction in section 6 titled “Conclusion and Future Research Directions”.

Reviewer 2 Report

This review is very comprehensive and can be used for fundamental knowledge for scientist and surgeons.  However, I recommend adding some tables to summarise the different platforms available, its potential adv and disadvantages etc. for easy referencing.

Good.

Author Response

Point 1: Suggested to add in tables to summarize emerging preclinical stem cell scaffolding platforms for SCI for easy referencing.

Response 1: We thank reviewer 2 for the positive feedback. We agree with reviewer 2 that it would be valuable to include tables summarizing emerging pre-clinical stem cell scaffolding platforms for SCI. As such, in section 5 we have included Table 1 “Summary of emerging pre-clinical studies utilizing collagen-based stem cell scaffolds for the treatment of SCI” and Table 2 “Summary of emerging pre-clinical studies utilizing hydrogel-based stem cell scaffolds for the treatment of SCI”.

Reviewer 3 Report

Comments to authors:

·       In the abstract, it is not clear what is meant by: “Present SCI treatment strategies aim to improve neurologic functioning, though the role of surgical intervention remains contradictory in the literature.” What exactly is contradictory? I’m not sure this should be included in the abstract as it is not a major focus of the review.

·       In the introduction (lines 42-44), it is not clear what is meant by: “The availability of such neurotrophic factors is mediated by the presence of matrix vehicles which act to exclusive provide the regenerating axon with specific growth factors.” Better to leave this statement for Section 3.4.

·       In Figure 1 and throughout the manuscript, the term “neuronal stem cell” should be changed to “neural stem cell”. “Neuronal stem cell” is not an appropriate term.

·       Line 73: “Somewhat contrastingly, microglia are of hematopoietic origin.” Please remove the word “somewhat”.

·       Lines 140-141: “This growth cone can be described as a mobile structure that uses various growth factors and signaling molecules in the surrounding environment to elongate and navigate the axon back to its original target.” What is the evidence that growth cones are able to navigate back to their original targets after injury in vivo?

·       Regarding use of polymers for membrane re-sealing after axonal injury, there is a conspicuous absence of citations for George Bittner’s group (arguably the top group in the field who has done this, successfully, to promote axonal fusion after injury)

·       Figure 2 legend: It’s not entirely correct to call it a “turning motion”, which suggests that the direction of the growth cone is simply rotated as it continues moving. The turning effect is modulated by dynamic changes on the GC itself. It is a stabilization of filopodia on the side with the higher concentration of chemoattractant molecules, and a destabilization of filopodia on the opposite side, that mediates the change in direction of growth.

·       Section 3.4. This reviewer is not familiar with “matrix vehicles”. More information is needed. Are they transplanted or injected into a lesion site? Have they been validated in vitro or in vivo? What makes these different than other bioscaffolds?

·       Section 3.5. It’s not clear why the term “intraoperative” is used here. This generally refers to, for example, stimulating the brain of an awake patient during surgery to ensure correct placement of electrical probes or map the cortical areas. The type of ES referred to in this section is not typically referred to as “intraoperative”. The authors can just call it “ES”.

·       Line 276: Worth mentioning that there are other types of functionally important axons (aside from corticospinals) that might have much larger diameters, when considering pore size.

·       Lines 292-294: The authors mention a “trend”. Please elaborate on the findings of this study.

·       Line 297: “College”

·       Section 4.4: This section is surprisingly short (2 sentences) which is very surprising given the decades of research on hydrogel scaffolds for SCI. Please expand on this section for an accurate appraisal of what has been done in the field.

·       Line 340: “A major challenge…” This sentence seems incomplete. Does SPI mean SCI?

·       Line 346: “This is particularly effective as growth factors often have short degrade quickly within tissue.”

Some sentences are poorly written and words misspelled, but these are infrequent.

Author Response

Response to Reviewer 3 Comments

Point 1: Suggests removing the statement in the abstract which talks about the contradictory role of surgery in SCI

Response 1: We agree with reviewer 3 that this should be removed from the abstract as it is not the focus of our review. The abstract has been modified to read “Common causes of SCI include traumatic motor vehicle accidents, falls, and sports injuries. Present SCI treatment strategies aim to improve neurologic functioning, and the potential for neural stem cells (NSCs) to differentiate into a variety of neural and glial cell precursors has led to the investigation of stem cell scaffolds as a therapeutic for SCI.”

Point 2: Suggested to remove the statement in lines 42-44 reading “The availability of such neurotrophic factors is mediated by the presence of matrix vehicles which act to exclusive provide the regenerating axon with specific growth factors” from the introduction.

Response 2: We agree that this statement should be left out of the introduction. We have removed this statement.

Point 3: Suggested to use the term “neural stem cell” instead of “neuronal stem cell”.

Response 4: We have changed every mention of “neuronal stem cell” to instead be “neural stem cell”

Point 5: Suggested to remove the word “somewhat” in line 73.

Response 5: The word “somewhat” has been removed.

Point 6: Mentioned the statement in lines 140-141 is not entirely clear.

Response 6: This sentence has been changed to read “This growth cone can be described as a mobile structure that uses various growth factors and signaling molecules in the surrounding environment to guide and elongate the axon”. We hope this change makes this sentence clearer and easier to understand.

Point 7: Suggests including citations from George Bittner’s group in section 3.1 “Plasma Membrane Sealants”.

Response 7: We have updated section 3.1 to include several studies from the Bittner group. We hope that the addition of these studies will strengthen the manuscript.

Point 8: Highlighted the use of “turning motion” in figure 2 is not entirely correct.

Response 8: To improve the accuracy of this legend, rather than using the phrase “turning motion” we have written “As depicted by this schematic, the neurotrophic factors bind to tyrosine kinase receptors which dimerize and induce a cascade of downstream protein pathway activations, resulting in a change in direction of axonal growth toward the source of the neurotrophic factors. This change in growth is ultimately made possible through the stabilization of filopodia on the side with the higher concentration of chemoattractant molecules, and a destabilization of filopodia on the opposing side with the lower concentration of chemoattractant molecules.”

Point 9: Requests more information regarding matrix vehicles.

Response 9: We have added an additional paragraph to section 3.4 with more detail regarding matrix vehicles. We hope this additional information clarifies the role and purpose of a matrix vehicle.

Point 10: Suggested removing the word “intraoperative” from section 3.5.

Response 10: We agree with reviewer 3 and have removed the word “intraoperative” from section 3.5 unless it was specified in the cited studies the ES was in fact intraoperative.

Point 11: Suggests mentioning other large functionally important axons in line 276.

Response 11: We agree that this inclusion would be valuable for this review. As such, we have mentioned pyramidal tract axons, purkinje cell axons, Aα sensory fibers, and Aβ sensory fibers.

Point 12: Asked to elaborate on the findings of the study mentioned in lines 292-294.

Response 12: We have modified our original manuscript to now read “However, a Bayesian network meta-analysis conducted by Zhang et al. determined collagen, fibrin, and gelatin to be the most ideal compounds used to create natural polymer stem cell scaffolds in a rat model of SCI” to clarify the results of the study.

Point 13: Indicated “College” in line 297 should be “collagen”.

Response 13: We have fixed this spelling error.

Point 14: Asked to provide more information regarding hydrogel scaffolding.

Response 14: We have included more information in section 4.4 that further elaborates on the function of hydrogel scaffolds. 

Point 15: Suggested to reword the sentence in line 340 for clarity as it seems incomplete in its original form. Additionally point 15 asked to clarify if SPI means SCI.

Response 15: We have removed this sentence entirely for clarity. SPI has been changed to SCI.

Point 16: Highlighted the original sentence in line 346 does not make sense.

Response 16: We have addressed this issue. The new sentence now reads “This is particularly effective as growth factors often degrade quickly within tissue.”

Reviewer 4 Report

           The manuscript entitled "Stem Cell Scaffolds for the Treatment of Spinal Cord Injury" offers a thorough examination of spinal cord injury (SCI), the significant role of neuronal stem cell differentiation in SCI recovery, and the multifaceted pathways engaged in this differentiation process. Furthermore, it explores the promising potential of stem cell scaffolding as an innovative therapeutic approach for SCI. The review presents a detailed analysis of various substrates for axonal regrowth, encompassing a wide array of research and mechanisms. Each process is elucidated with great detail, demonstrating an in-depth understanding of the subject matter.

Overall, this review is exceptionally informative, well-structured, and offers a comprehensive view of the topic. With the proposed modifications and additions, it has the potential to become an indispensable resource in the arena of stem cell scaffold development for SCI treatments.

Below are some suggestions to enhance the quality of the manuscript:

1. The manuscript mentions a two-stage pathogenesis of SCI (primary and secondary). The primary stage is clearly defined as the initial mechanical injury. However, it could be beneficial to include more details on secondary SCI to clearly delineate the chain of events following the initial injury.

2. The review mentions the role of neurotrophic factors in mediating axonal regrowth. Adding a more detailed discussion on the interaction of these factors with other cell types or molecular mechanisms involved in regeneration could enrich this section.

3. The review mentions pharmacologic agents and surgical intervention as current standard treatments but does not specify what these are. Providing more detail on these treatments would be helpful for readers not familiar with the current standard of care for SCI.

4. The manuscript introduces the concept of stem cell scaffolding, but it may be worth exploring more about how these scaffolds are introduced into the SCI site and how they interact with the existing neuronal and non-neuronal environment. Furthermore, discussing any potential risks or challenges associated with this approach would be beneficial.

5. The description of Figure 1 is concise. However, adding more detail regarding the specific markers seen at each differentiation stage and the changes that occur as the cells differentiate could help improve readers' understanding.

6. The manuscript covers the main signaling pathways involved in NSC differentiation but could benefit from a more detailed discussion on the specific roles of these pathways in relation to SCI. For example, are there particular pathways that are more relevant in the context of SCI? How might these pathways be manipulated to promote recovery?

7. The paper uses many complex scientific terminologies that might be difficult for a general audience to understand. It would be beneficial to include a section to explain some of the more complicated concepts, or perhaps provide a simplified summary of the main points.

8. The paper cites numerous studies, but some of them are not properly identified in the text. For instance, the paper refers to 'one study' or 'later study', but it does not clearly identify which studies these are. This should be addressed to ensure proper credit is given, and to allow readers to follow up on the original research if they so wish.

9. This section could benefit from a more thorough explanation of the mechanism of growth cone formation and stabilization. Further clarification is needed on the role of microtubules and actin filaments in these processes.

10. Neurotrophic Factors and Guidance: It is recommended that the authors explain the importance of these factors in more detail. While the article does a good job of outlining which factors are important, it does not fully explain why these factors are important for axonal growth.

11. Matrix Vehicles for Axonal Regeneration: More recent or updated studies regarding the use of other types of media for axonal regrowth could be included to provide a more up-to-date review of this area of research.

12. Intraoperative Electrical Stimulation for Axonal Growth: The authors should elaborate more on the mechanism of how electrical stimulation promotes axonal growth. If possible, it would also be beneficial to mention the specific parameters for electrical stimulation (e.g., intensity, duration, frequency) that have been found to be most effective in promoting axonal growth.

13. I suggest the authors could give a bit more focus on the synthesis, biocompatibility, biodegradability, and overall performance of the synthetic and hybrid/composite scaffolds. Some specific examples, perhaps in table format, would greatly enhance the understanding of these materials and their applications.

14. The concept of incorporating growth-modulating factors into the scaffolds for promoting neuronal, axonal, and vascular growth and integration is well discussed, however, I recommend adding more references to support this claim and elaborate on how different growth factors can be integrated into different types of scaffolds. It would be beneficial if the authors could include more recent references or indicate why older references are still relevant.

15. There's a mention of a phase 1 trial using collagen scaffold with human umbilical cord-mesenchymal stem cells, and this is really exciting. A deeper discussion on the mechanisms and outcomes would further strengthen the paper.

16. The authors should draw more comparisons between the different types of scaffolds (collagen-based, hydrogel-based, etc.), highlighting their advantages and disadvantages.

17. Some terms are used without definition or explanation. For instance, the term "OSMI-4" is used without any introduction. The authors should provide brief descriptions or definitions of such terms for the benefit of readers who may not be familiar with them.

18. In reference to the clinical trial (NCT 02510365), the authors should provide more details. For instance, who conducted it? What were the key findings? And why is it relevant to the discussion?

19. Future Research Directions: The conclusion and future directions section is well-written. It could be improved by adding some potential challenges and barriers that might be encountered in translating these preclinical findings into clinical practice.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 4 Comments

Point 1: Suggests including more information about secondary SCI in the introduction of the manuscript.

Response 1: We agree with reviewer 4 that more information regarding secondary SCI should be included in the introduction. As such, we have modified the discussion of secondary SCI in the introduction to read “Primary SCI refers to the initial mechanical injury while secondary SCI involves a cascade of increased immune activation, neuroinflammation, and excitotoxicity following the initial injury. Specific mechanisms of secondary SCI include lipid peroxidation, axon degermation and demyelination, calcium influx, free radical formation, and remodeling of the surrounding extracellular matrix. The extent of secondary SCI is presumed to predict and influence SCI severity and can be acute or chronic, highlighting its potential role as a target for intervention.”

Point 2: Suggested to add a more detailed discussion regarding the interactions of neurotrophic factors with other cell types and molecular mechanisms involved in regeneration.

Response 2: To improve upon this section of the manuscript, section 3.3 “Neurotropic Factors and Guidance” has been updated to include more detailed information regarding BDNF, NT3, and NGF. Specifically, we have included a more detailed discussion of NT3 and NGF as the original version of the manuscript focused primarily on BDNF.   

Point 3: Suggests being more specific with respect to what pharmacological agents and surgical interventions are current standards of care of SCI.

Response 3: We agree with reviewer 4 that this should be more specific. As such, we have included paracetamol, weak opioids, and non-steroidal anti-inflammatory drugs in addition to spinal decompression as standard of care therapies for SCI.

Point 4: Suggests including more information regarding how stem cell scaffolds are introduced into the SCI site and how they interact with the surrounding neuronal and non-neuronal environment including benefits and risks.

Response 4: Section 5 titled “Emerging Pre-Clinical Studies and Their Applications for Clinical Adoption” explains how various scaffolds are introduced at the site of the SCI lesion. Most often, this occurs with injection. Additionally, the interactions of various scaffolds with the surrounding neuronal and non-neuronal environment is discussed in section 5.

Point 5: Suggested to add more detail regarding activation markers at different stages of stem cell differentiation to figure 1.

Response 5: We agree with reviewer 4 that more detail should be added to figure 1. As such, we have included specific activation markers.

Point 6: Suggests providing a more detailed discussion of how the major signaling pathways in NSC differentiation discussed in the original version of this review relate specifically to SCI.

Response 6: We agree that there should be more information included in the current version of the manuscript detailing how the discussed signaling pathways involved in NSC differentiation relate to SCI specifically. As such, we have included more information in sections 2.1, 2.2, 2.3, and 2.4 regarding how these signaling pathways are affected in SCI.

Point 7: Highlighted that there are complex terminologies utilized throughout the manuscript that may be difficult for readers to understand if they are not clarified or simplified.

Response 7: We agree with reviewer 4 that some of the processes outlined in the review, particularly in section 2, could be further explained and/or simplified. To improve this aspect of the paper, all of the major signaling pathways discussed in section 2 have been explained further.

Point 8: Suggested to identify studies properly in-text for easy reference.

Response 8: All of the in-text citations in this manuscript have been double checked. All of the sentences that begin with ‘one study’ or ‘later study’ have been updated to include the author and study information.

Point 9: Suggested to explain further the mechanism of growth cone formation and stabilization, making sure to further clarify the role of actin and microtubules in these processes.

Response 9: We are that the manuscript in its present form could benefit from a more detailed discussion of growth cone formation and stabilization. We have included a more detailed discussion of growth cone formation and stabilization in section 3.2 “Growth Cone Formation and Stability”.

Point 10: Suggests explaining the importance of neurotrophic factors in more detail, specifically highlighting the role they play in axonal regrowth.

Response 10: We agree with reviewer 4 that the original version of section 3.3 “Neurotrophic Factors and Guidance” should be revised to include more information that explains why these factors are important for axonal regrowth. As such, we have included more information about the various signaling pathways and biological mechanisms neurotrophic factors utilize to exert positive effects on axonal regrowth. We hope that this additional biochemical background will help explain and clarify why and how neurotrophic factors are able to exert these positive effects following axonal injury.

Point 11: Suggested to include more recent studies regarding matrix vehicles for axonal regeneration.

Response 11: We agree with reviewer 4 that more recent studies should be included in this section of our manuscript. We have added an additional paragraph to section 3.4 “Matrix Vehicles for Axonal Regeneration” which discusses a few more modern approaches.

Point 12: Suggested to elaborate more on the mechanisms of how electrical stimulation promotes axonal regrowth. Additionally, it was suggested to include the specific parameters for electrical stimulation in the mentioned murine models.

Response 12: To clarify and better explain how electrical stimulation promotes axonal regrowth, the first paragraph of section 2.5 “Intraoperative Electrical Stimulation for Axonal Growth” has been slightly modified. In the second paragraph, the specific parameters of electrical stimulation have been included for all of the studies that disclosed this information.

Point 13: Suggested to provide more information regarding the synthesis, biocompatibility, biodegradability, and overall performance of synthetic and hybrid/composite scaffolds outlined in sections 4.2 and 4.4.

Response 13: We agree that sections 4.2 and 4.4 could be strengthened. As such, we have included a deeper discussion of synthetic and hybrid/composite scaffolds in the most updated version of the manuscript. It is important to note that this section is designed to be a basic overview of the different scaffolding modalities available as their applications to clinical medicine/emerging preclinical studies are discussed in section 5.

Point 14: Suggests to include more references and elaborate more on section 4.5 which discuses growth modulating factors.

Response 14: We agree with reviewer 4 that this section would benefit from the addition of more recent studies and a more in-depth discussion. As such, we have included this information in section 4.5 “Growth Modulating Factors”.

Point 15: Suggests elaborating more on the phase 1 clinical trial using collagen scaffold with human umbilical cord-mesenchymal stem cells mentioned in section 4.1 “Natural Polymer Scaffolds”.

Response 15: This phase 1 clinical trial is discussed in-depth in section 5 “Emerging Pre-Clinical Studies and Their Applications for Clinical Adoption”. As such, we have removed mention of this clinical trial from section 4.1.

Point 16: Suggested to draw more comparisons between different types of scaffolds taking care to highlight advantages and disadvantages.

Response 16: We agree with reviewer 4 that including these comparisons will strengthen section 4 “Overview of Stem Cell Scaffolding”. As such, we have included comparisons, advantages, and disadvantages within each subsection (4.1, 4.2, 4.3, and 4.4)

Point 17: Suggested to introduce and define the term “OSMI-4”.

Response 17: In the original version of the manuscript, OSMI-4 is defined as a small molecule O-GlcNAc transferase inhibitor. 

Point 18: Asked to provide more details regarding the clinical trial (NCT 02510365) mentioned in section 5. Reviewer 4 specifically asked to include information about who conducted it, what the key findings were, and why the trial is relevant to the overall discussion of the paper.

Response 18: In the original manuscript, the key findings and author of this clinical trial is stated in section 5. To clarify, the name of the author has been included in the sentence. We have additionally included a brief summary of why this clinical trial is relevant to the overall discussion of the paper.q

Point 19: Suggested to include potential challenges and barriers that may be encountered in translating these preclinical findings into clinical practice.

Response 19: We thank reviewer 4 for the kind words regarding section 6. To improve this section, we have included several challenges including administration method, cost, and scaffold composition.

Round 2

Reviewer 1 Report

The main focus of this review is scaffold for SCI treatment. In section 3, how the scaffold impact "plasma membrane sealants", "Growth Cone Formation and Stability", "Neurotrophic Factors and Guidance", or "Electrical Stimulation for Axonal Growth"?

Please double-check the font.

Author Response

Point 1: Asked about in section 3 how stem cell scaffolds influence plasma membrane sealants, growth cone formation and stability, neurotrophic factors and guidance, as well as electrical stimulation for axonal growth.

Response 1: It remains largely unknown in the literature how exactly stem cell scaffolds influence plasma membrane sealants, growth cone formation and stability, neurotrophic factors and guidance, as well as electrical stimulation for axonal growth. We have added additionally information into ach section explaining more research is necessary to understand the role of how stem cell scaffolds influence these aspects of neural regeneration.

Point 2: Asked to double-check fonts throughout the manuscript.

Response 2: In response to this comment, we have ensured that the entire document, figures included, contains times new roman size 12 font.

Reviewer 3 Report

The authors have satisfactorily addressed my previous concerns. No additional changes are needed.

Author Response

We thank reviewer 3 for their comments. We have made no additional changes to our manuscript. 

Reviewer 4 Report

Thank you to the authors for addressing all of my concerns and making improvements to the manuscript. However, the final abstract could benefit from further refinement. I suggest you include more specific details about the different types of stem cell scaffolding platforms discussed in your review. Additionally, provide a concise summary of the main conclusions or significant insights of your study.

As for the keywords, you have done well to expand them. I recommend including even more specific terms related to your findings to optimize the discoverability of your work.

*Please see the reviewer's suggests Abstract as follows:

Spinal cord injury (SCI) is a profoundly incapacitating and frequent condition of the central nervous system, leading to substantial morbidity and mortality rates. Major causes encompass traumatic incidents such as motor vehicle accidents, falls, and sports injuries. Existing treatment strategies for SCI focus on enhancing neurological functionality. The capacity of neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the exploration of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities, including composite materials, natural polymers, synthetic polymers, and hydrogels, have been examined. Nonetheless, most trials remain in the preclinical phase, emphasizing the necessity to further evolve and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, the substrates required for axonal regrowth post-injury, and an overview of the current and emerging stem cell scaffolding platforms for SCI.

*Expanded Keywords: Spinal cord injury; stem cell therapy; scaffolding; neuroregeneration; neural stem cells; axonal regrowth; tissue engineering

Author Response

Point 1: Suggests to further refine the abstract per the reviewer’s suggestions.

Response 1: We agree with reviewer 4 that our abstract could be further refined for clarity. We have incorporated some of reviewer 4’s suggestions into our new abstract which now reads:

“Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the to need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.”

Point 2: Suggested to add some additional keywords to our review.

Response 2: We agree that our work could benefit from the addition of more keywords. We have added 7 more keywords to our manuscript based on reviver 4’s suggestions. Specifically, our keywords now include “spinal cord injury; stem cell therapy; scaffolding; neuroregeneration; neural stem cells; axonal regrowth; tissue engineering; composite scaffolds; natural polymer scaffolds.”

Round 3

Reviewer 1 Report

The Authors have addressed all my concerns

Author Response

We thank Reviewer 1 for their response. We have made no changes to our manuscript.