Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article is a well-written review of the literature on the stated topic. The authors examine a large pool of data characterizing changes in muscles and their recovery. The review considers examples of studies in humans and animals. All material is supported by references. The authors also refer to their own research conducted in their laboratory, but nowhere do they mention the ethical component of the procedures they carried out independently, the number of animals, and the conditions of the study, for which it was conducted. It would be nice to include a reference to this study, if the authors have one. When giving examples with athletes, in my opinion, it is worth considering examples related not only to weightlifting, but also to team sports, since there are also significant changes in muscle damage and subsequent recovery in these sports. Studies related to marathon runners, trail runners, and sky runners could also be considered, but this suggestion should not be taken as a mistake on the part of the authors. Another suggestion for the authors is to review the literature on muscle recovery after immobilization/inactivity and compare it with the conditions described earlier by the authors. This would allow for a more detailed review. The review presented by the authors is very relevant and deserves attention, as Duchenne muscular dystrophy is a severe genetic disease caused by mutations in the dystrophin gene, leading to progressive muscle weakness, predominantly in boys. The incidence is estimated at an average of 1 case per 3,500–5,000 newborn boys, with a prevalence of about 3.3–3.5 per 100,000 population. Therefore, research in this area is very necessary and important, since the average life expectancy for this disease is 28–30 years with the necessary and correct therapy. The team of authors has done a great job in creating this review, and it certainly deserves to be published in the journal after minor corrections (bioethics).

Author Response

The article is a well-written review of the literature on the stated topic. The authors examine a large pool of data characterizing changes in muscles and their recovery. The review considers examples of studies in humans and animals. All material is supported by references.

Comment 1: The authors also refer to their own research conducted in their laboratory, but nowhere do they mention the ethical component of the procedures they carried out independently, the number of animals, and the conditions of the study, for which it was conducted. It would be nice to include a reference to this study, if the authors have one.

Response 1: The notexin injury paragraph has been updated to reflect outcomes in wild-type mice following a single notexin injection to the EDL, including recovery of maximal force, stiffness, twitch kinetics, and mechanical stability, and this statement is now explicitly supported by citation of the primary study (Ref. 35). As this is a literature review, ethics approval, animal numbers, and experimental conditions are not restated here; these details are available in the cited primary publication (Ref. 35).

 

Comment 2: When giving examples with athletes, in my opinion, it is worth considering examples related not only to weightlifting, but also to team sports, since there are also significant changes in muscle damage and subsequent recovery in these sports. Studies related to marathon runners, trail runners, and sky runners could also be considered, but this suggestion should not be taken as a mistake on the part of the authors.

Another suggestion for the authors is to review the literature on muscle recovery after immobilization/inactivity and compare it with the conditions described earlier by the authors. This would allow for a more detailed review.

Response 2: Thank you for these suggestions. We have added two brief statements to broaden the context while keeping the review focused on branched fiber formation: (i) we note that team-sport and endurance athletes also experience repeated eccentric loading and transient muscle damage–recovery cycles, while clarifying that branched fibers are rarely quantified directly in these cohorts; and (ii) we include immobilization/disuse with subsequent reloading as a comparator paradigm, emphasizing that reloading can provoke secondary damage and regeneration, but that direct evidence linking disuse–reloading to branched fiber formation remains limited.

The review presented by the authors is very relevant and deserves attention, as Duchenne muscular dystrophy is a severe genetic disease caused by mutations in the dystrophin gene, leading to progressive muscle weakness, predominantly in boys. The incidence is estimated at an average of 1 case per 3,500–5,000 newborn boys, with a prevalence of about 3.3–3.5 per 100,000 population. Therefore, research in this area is very necessary and important, since the average life expectancy for this disease is 28–30 years with the necessary and correct therapy.

The team of authors has done a great job in creating this review, and it certainly deserves to be published in the journal after minor corrections (bioethics).

Reviewer 2 Report

Comments and Suggestions for Authors

see attached

Comments for author File: Comments.pdf

Author Response

 Comments on manuscript entitled “Twisting paths: The paradox of fiber branching in muscle re-generation”:

Comments to the Authors:

The purpose of the manuscript was to review the literature regarding muscle fiber branching as it pertains to pathologic and non-pathologic conditions with the hope of providing insight into potential ways this process could be leveraged for the development of therapeutic strategies for muscle diseases. In general, the review paper is comprehensive, relevant to the field and of interest to the Journal readership. However, the paper would benefit from some adjustments prior to making a determination regarding publication. Should the authors wish to make the below-mentioned major and minor adjustments to the paper, the reviewer is willing to reassess the manuscript for publication in IJMS. Specific suggestions include the following (for ease, these are listed by manuscript section):

Comment 1: Overall comment: the paper requires additional references for numerous claims/statements made without citation, and the authors should pay close attention to maintaining referencing style formatting as there is a lot of variability throughout the orrestructuring (see bullet point 2 below) so that the implications / significance of the muscle findings in non-pathologic conditions could be mentioned earlier versus waiting until the discussion initiated on line 317. In contrast, sections 3-5 are much better structured and made for easy reading.

Response 1: We have added citations throughout the manuscript where claims required additional supporting references, and we have harmonized referencing formatting for consistency. In addition, we inserted a brief framing paragraph early in Section 2 to summarize the significance/implications of branching in non-pathologic (non-dystrophic) contexts, so the “so what” is introduced before the later discussion.

Comment 2: Introduction: Although the initial paragraph is well-written (lines 29-44), the statements made require references to substantiate the claims.

Response 2: We added references supporting the key statements in the opening paragraph describing regeneration, atypical remodeling/branching during regeneration, increased branching with repeat injury, and the relevance to dystrophic pathology.

Comment 3: Lines 58-59: recommend deleting the second use of the term “over time” (in line 59) as this is redundant with line 58.

Response 3: Revised as suggested to remove redundancy.

Comment 4: Figure 1 comments: For referencing consistency, I recommend that the authors continue to use the numbered referencing style used throughout the rest of the manuscript (see line 64). The same is true for all figures (lines 98, 217, 243, 371, 377, 466, 576)

Response 4: We updated figure legends to use the same numbered citation style used throughout the manuscript and removed any inconsistent author–year formatting.

Comment 5: Line 65-66 would benefit from rephrasing as the statement made regarding satellite cells is overly simplistic and technically incorrect. Specifically, not all satellite cells ARE myoblasts. Upon activation, a subset of satellite cells will become myoblasts, however, owing to asymmetric self-renewal, another subset (Pax7+/Myf5-) remain quiescent and are involved in maintaining the stem cell niche.

Response 5: We revised the text (and Figure 1 legend text) to clarify that satellite cells are muscle stem cells that, upon activation, can generate myoblasts for repair while also self-renewing to maintain the satellite cell pool, rather than implying all satellite cells are myoblasts.

Comment 6: Lines 71-72: If the figure was generated using multiple studies, as the authors claim, then these studies should also be referenced in the figure.

Response 6: In line with the approach taken throughout the manuscript, we cite the primary source used for the schematic adaptation (Dueweke et al. [7]). Readers can trace the lineage of the schematic components through this primary source and the underlying literature cited therein; therefore, we did not add an extended list of historical sources to the figure legend.

Comment 7: Minor comment- the figure seems slightly blurred and would benefit from enhanced resolution if possible.

Response 7: We replaced the figure with a higher-resolution version.

Comment 8: The statements made in lines 73-77 require referencing, as do lines 81-82.

Response 8: We added appropriate citations supporting these statements and ensured consistency with the manuscript referencing style.

Comment 9: Line 109: The inclusion of the word “Words” at the beginning of the sentence does not make sense. Please verify the structure of the sentence for the intended meaning.

Response 9: Removed.

Comment 10: Muscle fiber branching in healthy muscle: Overall this section currently reads more like an extensive list of examples to show that muscle fiber branching can occur via numerous physiological and experimental mechanisms (lines 120-316). Although the reviewer appreciates the authors’ detailed investigation into the topic, the section would benefit from a restructure to get to the point faster – i.e., the reviewer suggests this section could be rewritten so that the implications / significance of the muscle findings could be mentioned earlier versus waiting until the discussion initiated on line 317. Lines 124-126 read a little redundant / unclear as the examples provided appear to be a continuation of the prior list (in lines 121-142) rather than examples specific to healthy muscle (especially as I would not consider toxin/ablation-induced injury a “healthy”/physiological mechanism of injury). The authors may wish to revise lines 121-126 for added clarity.

Response 10: Without substantially restructuring Section 2, we added a concise framing paragraph early in the section to state the implications/significance of branching in non-dystrophic muscle and to provide context for later dystrophic sections. We also revised the opening lines to clarify that this section focuses on non-dystrophic muscle and that branching is most commonly reported following experimental injury and/or extreme loading paradigms, thereby avoiding describing toxin/ablation paradigms as “healthy” mechanisms.

Comment 11: Please provide a reference for the statements made in lines 129-132 regarding muscle fiber type differences.

Response 11: We added references to support the fibre type-related statement while keeping the review focused and avoiding unnecessary expansion.

Comment 12: For in text citations listed on lines 138, 154, 162, 165, 178, 189 please reformat to maintain a consistent referencing style. For example, papers with 2 authors should be named with an “and” between the primary authors (vs. a comma), and citations with three or more authors can be listed as First author et al., (citation number). There are other examples not listed, so please check the rest of the document for formatting style.

Response 12: We standardized in-text author formatting throughout the manuscript to match this style guidance (two authors “and”; three or more “et al.”) and checked the remainder of the manuscript for similar instances.

 

Additional minor details and/or clarification within specific areas of this section are also required:

 

Comment 13: Lines 329-340 require referencing.
Response 13: We added supporting citations for the statements regarding slowed kinetics/putative protective effects in highly branched muscles and ensured consistent formatting with adjacent sections.

Like preceding sections, pay attention to referencing style

Comment 14: Please combine the references on line 456

Response 14: Combined as requested.