Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript reads smoothly and is well-organized, and presents an excellent overview of the aging process of scalp, hair, and the inter-relationships between them.  As a clinician, the manuscript supplies an excellent foundation for understanding the aging process.  As I read it, I found that I was able to correlate my clinical understanding with the story told by the authors. The illustrations reflected positively on the text.

I found a few minor errors, for example:  Line 860 "Compared to the hair follicle in the young scalp skin, a less pigmented hair fibre is produced in the ageing hair follicle and appears to have a smaller hair diameter, coarser, less 861 lustrous, and more susceptible to breakage."  Coarser reflects a larger, not a smaller, diameter, which contradicts the message delivered in this sentence. 

Comments on the Quality of English Language

 The English was clear and concise.  It is a well-written, informative manuscript. 

Author Response

Comment 1: Line 860 "Compared to the hair follicle in the young scalp skin, a less pigmented hair fibre is produced in the ageing hair follicle and appears to have a smaller hair diameter, coarser, less 861 lustrous, and more susceptible to breakage."  Coarser reflects a larger, not a smaller, diameter, which contradicts the message delivered in this sentence.

Response 1: Thank you for pointing this out. I agree with your comment that coarser hair refers to a larger hair diameter. Therefore, I have removed the word 'coarser' in Line 860 to avoid any confusion to the reader. This edit has been indicated in the text via tracked changes.

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript, "A Multifaceted View on Ageing of the Hair and Scalp," is recommended for acceptance following minor revision. It offers a well-organized overview of the literature, supported by a broad range of references, and addresses key aspects such as pigmentation, alopecia, morphology, scalp physiology, and the microbiome. The paper is relevant to both dermatology and cosmetic science. To improve flow and accessibility, I suggest clarifying the statement of novelty, tightening the links between sections, and adding summary visuals. With these revisions, the manuscript will be a valuable contribution to the journal.

Author Response

Comment 1: To improve flow and accessibility, I suggest clarifying the statement of novelty, tightening the links between sections, and adding summary visuals. With these revisions, the manuscript will be a valuable contribution to the journal.

Response 1: Thanks for your suggestions. I agree with your comments to clarify my statement of novelty, improving the links between sections and using summary visuals to improve understanding for the reader. 

1) To emphasize the novelty of my article, I have added these sentences in Line 17 and Line 879 (respectively), "Consideration of the morphological changes of the hair fibre, biological processes occurring within the hair follicle and its enveloping scalp environment provide a unique, holistic overview of hair and scalp changes during ageing.", and "In these present times, it is no longer sufficient to consider individual aspects of hair science separately but to embrace a holistic perspective that all these factors can collectively influence age-related changes of the hair and scalp."

2) On the improvement of text cohesiveness, I have better highlighted the links between my article's summary visual Figure 3 and the relevant paragraphs. For example, with the additions of Line 597 "These differing characteristics are depicted in the summary visual comparing healthy young and aged human skin (Figure 3)", Line 626 "These differences have also been included in Figure 3", Line 753 ", as illustrated in Figure 3".

Reviewer 3 Report

Comments and Suggestions for Authors

1. Abstract is missing scietific style and probably need language improvements too
2. Line 30 - are 3 references really needed for this slightly irrelevant statement
3. Line 53 - which program was used to produce this figure? Sentence in bracket is not necessary
4. Latin words should be in italic (eg line 60)
5. Line 90 title is enough, explanation can be added to main text
6. Line 238 - not all excessive loss will result with alopecia
7. Line 752 - add table with previous studies, search and add more literature for this section as it will probably be most interesting to readers
8. Improve quality of all figures (maybe bigger font as it is hard to read)

This review is interesting but I believe it would benefit from some refinements. I believe those would help this review to add to the existing body of literature in the field of hair science.

Author Response

Comment 1: Abstract is missing scietific style and probably need language improvements too.

Response 1: Thanks for your suggestions. I have edited my abstract to sharpen my language and added "Consideration of the morphological changes of the hair fibre, biological processes occurring within the hair follicle and its enveloping scalp environment provide a unique, holistic overview of hair and scalp changes during ageing" to further highlight the novelty of this review paper.

Comment 2: Line 30 - are 3 references really needed for this slightly irrelevant statement.

Response 2: With regards to this statement (Line30), since it is in introduction, I intended to include additional interesting reads not solely on biology, but that also draws on psychology, anthropology and biology, with well-rounded perspectives. To also highlight that beauty cannot be defined scientifically, it is also cultural, societal views that shape them and cause us to deem as important.

Comment 3: Line 53 - which program was used to produce this figure? Sentence in bracket is not necessary

Response 3: This figure on 'stages of the hair growth cycle' was created on Microsoft Powerpoint. After some thought, I have decided to retain the sentence in bracket which states, 'Starting from the top box; clockwise direction' (Line 57-58), as it indicates the direction to read the hair cycle for a reader new to the understanding about hair.

Comment 4: Latin words should be in italic (eg line 60)

Response 4: With regards to Comment 4, I believe that the word referred to in Line 60 is pilosebaceous unit. To be certain, I have checked other scientific articles that have mentioned 'pilosebaceous unit', but none is italicized. This is because it is viewed as a common medical and anatomical term, not a formal taxonomic or scientific name that requires italics.

Response 5: Line 90 title is enough, explanation can be added to main text

Comment 5: Thanks for your suggestion on retaining only the title of the figure. After much deliberation, we have decided to still include the explanation of the figure. This is because there are two parts to the figure and we would like to clearly delineate which part of the hair we are depicting.

Response 6: Line 238 - not all excessive loss will result with alopecia

Comment 6: Thanks for your comment of Line 238 that not all excessive loss will result with alopecia. I agree that this statement can be misleading, hence I have edited Line 240 to 'While an individual typically sheds approximately 50 – 100 hairs a day, excessive hair loss leads to balding. This loss or absence of hair from areas of the body where it is expected to be found is medically termed as alopecia [8,11,63].'.

Comment 7: Line 752 - add table with previous studies, search and add more literature for this section as it will probably be most interesting to readers

Response 7: Thanks very much for your valuable suggestion. Aligned with your comment, I have expanded Section 4 on Hair and Scalp Care to include your suggestions. My additions are as follows, Line 840-"These, in addition to more commonly seen caffeine, adenosine and biotin, can be formulated into hair products [217,218,219]. Although scientific evidence supporting these ingredients are varying and show limitations, requiring further optimization of dosage and delivery, as well as large-scale clinical validation. Alternatively, new and emerging stem cell-based and exosome therapies are still in the early stages of research and development, and are still considered to be experimental solutions [217]."

Comment 8: Improve quality of all figures (maybe bigger font as it is hard to read)

Response 8: Thanks for your comment. According to your suggestions, I have redone the fonts of all my figures 1, 2, 3 and also have sought to improve their quality.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have done a complete narrative review, which is suitable and interesting to consider the biological and potential clinical aspects of hair ageing. It is useful for clinicians willing to employ innovative solutions.

The narrative is clear and the topic suits the audience. However, a few internal inconsistencies, mechanistic overstatements, and wording issues reduce precision. Addressing the items below would strengthen the manuscript and align figures, mechanisms, and text.

1. Scalp TEWL. There are some inconsistencies among the trends in the text. This leads to some confusion in an important aspect. please check it and harmonise it across the text:

- “older age group (mean age: 62 ± 2 years) exhibited significantly higher values of TEWL”

- “men in the 50s age group showed only reduced TEWL at the scalp occipital”

- “such as lower TEWL, lower sebum secretion, a thinning epidermal layer … (Figure 3)”

2. Normal daily shedding it also being referenced differently across the text (100-150 and 50-100). Please also check the references

3. 18-MEA yearly loss's claim might need some revision. Perhaps softening it and checking the literature cited.

4. The reference to EGF, IGF-1 and FFG-7 as upregulator of the WNT/beta-catenin signalling should also be reviewed as there are conflicting literature on this.

5. You note S. aureus as a source of oxidative stress, then include it among commensals that promote regeneration in WIHN. Please clarify strain- and context-specific effects, i.e., pathogenic vs commensal states, and model limitations.

6. Minor English corrections

Author Response

Comment 1: Scalp TEWL. There are some inconsistencies among the trends in the text. This leads to some confusion in an important aspect. please check it and harmonise it across the text:

- “older age group (mean age: 62 ± 2 years) exhibited significantly higher values of TEWL”

- “men in the 50s age group showed only reduced TEWL at the scalp occipital”

- “such as lower TEWL, lower sebum secretion, a thinning epidermal layer … (Figure 3)”

Response 1: Thanks for your comment. I also agree with your suggestion. Upon close examination, I have corrected Line 575-“older age group (mean age: 62 ± 2 years) exhibited significantly higher values of TEWL” to "it was reported that Caucasian women of an older age group (mean age: 62 ± 2 years) exhibited significantly lower values of TEWL and decreased scalp surface temperatures at the scalp vertex". While there still exists small variations between gender and age, as mentioned in the text, overall it is recognized there's a significantly lower TEWL of ageing scalp skin. The above sentence now coincides with Line 589-“men in the 50s age group showed only reduced TEWL at the scalp occipital”, as well as Line 864-“such as lower TEWL, lower sebum secretion, a thinning epidermal layer … (Figure 3)”.

Comment 2: Normal daily shedding it also being referenced differently across the text (100-150 and 50-100). Please also check the references.

Response 2: Thanks for pointing out this rate of normal, daily shedding of hairs. I have checked through the references 8, 11, 63 and proceeded to synchronise both statements, Line 54-"..., with normal shedding taking place at a rate of 100 - 150 strands per day" and Line 241-"While an individual typically sheds approximately 100 hairs a day".

Comment 3: 18-MEA yearly loss's claim might need some revision. Perhaps softening it and checking the literature cited.

Response 3: Thank you for your suggestion. After reviewing various literature, I have followed your comment to soften the statement. This has now been changed to (Line 501)-"Through these daily stresses, the amount of 18-MEA naturally decreases with age, with studies showing more pronounced loss of total 18-MEA content starting from age 50."

Comment 4: The reference to EGF, IGF-1 and FFG-7 as upregulator of the WNT/beta-catenin signalling should also be reviewed as there are conflicting literature on this.

Response 4: Thanks for this comment. I also agree that there can be further explanation on the roles of the 3 growth factors - EGF, IGF-1 and FGF-7 mentioned. Hence, I have corrected Line 265-"Several studies have proposed that hair loss treatments involving EGF (epidermal growth factor), IGF-1 (insulin-like growth factor 1) and FGF-7 upregulates Wnt/β-catenin signalling in DP that stimulate anagen entry and hair growth [73]." to now Line 265-"Several studies have proposed that hair loss treatments involving IGF-1 (insulin-like growth factor 1) and FGF-7 upregulates Wnt/β-catenin signalling in DP that stimulate anagen entry and hair growth. Another well-studied growth factor EGF (epidermal growth factor) also has an important role in regulating hair follicle growth, however recent findings indicate that EGFR signalling downregulates Wnt/β-catenin signalling to delay differentiation and lineage commitment, in doing so helps to coordinate normal hair follicle formation [73]."

Comment 5: You note S. aureus as a source of oxidative stress, then include it among commensals that promote regeneration in WIHN. Please clarify strain- and context-specific effects, i.e., pathogenic vs commensal states, and model limitations.

Response 5: Thanks for your comment. I also agree with your suggestions. Firstly, I have acknowledged that S. aureus is part of the commensal microbiome, this is apparent in Line 752-"..there is new, promising data indicating that the commensal microbiome (also including S. aureus) is able to promote regeneration of hair follicles..". To respond to your additional pointers, I have edited Line 750 to "Striking the right balance between the skin microbiota and host environment (i.e. strain-specificity and context-dependence) is ultimately key,..", as well as included another sentence to point out how WIHN does not occur in humans, but the study further showed improved healing in humans as well - Line 756-"While the WIHN phenomenon is not evident in human skin, commensal microbes, such as S. aureus, are able to accelerate wound healing in mouse and human [204] which suggests an overlapping mechanism".

Comment 6: Minor English corrections

Response 6: Thanks for your comment. I have noted that certain English corrections are still necessary and have corrected them accordingly.

Reviewer 5 Report

Comments and Suggestions for Authors

For the Authors:

Suggestions and Comments:

The manuscript presents valuable and well-organized data. However, several revisions are necessary before it can be considered for publication:

1. Please enhance the clarity of the text in Figure 2, as some labels are currently difficult to read.
2. Expand the discussion on genetic influences and regional differences in hair and scalp ageing.
3. Strengthen the analysis of gender-related effects on hair and scalp ageing.
4. Consider adding a flowchart summarizing all possible factors contributing to hair changes with age.
5. Include a section discussing potential methods to reduce age-related hair changes, such as innovative shampoo or crème rinse ingredients, and lifestyle factors like sun exposure avoidance.
6. Add a "Future Perspectives" section to guide readers through potential research avenues and unresolved questions.
7. Ensure the manuscript complies with the journal’s plagiarism policy by reviewing the iThenticate report.

Best of luck with your revisions!

 

Author Response

Comment 1: Please enhance the clarity of the text in Figure 2, as some labels are currently difficult to read.

Response 1: Thanks for your suggestion. I have since improved the clarity of the text in Figure and also increased the font for some words.

Comment 2: Expand the discussion on genetic influences and regional differences in hair and scalp ageing.

Response 2: Thanks for your comment. I understand that readers may also be wondering the underlying basis of differences in greying pattern across the different scalp sites. Hence I have added an explanation at Line 129-"This varying rate and timing of hair greying, as well as other hair parameters, across the different parts of the scalp may be attributed to embryonic derivation, where the anterior scalp (frontal and temporoparietal areas) originates from the neural crest and the posterior scalp, consisting of the occipital area) is derived from the mesoderm [26]".

Comment 3: Strengthen the analysis of gender-related effects on hair and scalp ageing.

Response 3: Thanks for your suggestion. I also agree with your comment and have edited these sentences to emphasize on these gender-related effects on hair and scalp ageing, Line 11-"...this review includes current knowledge of biological processes underlying hair pigmentation and hair growth, highlights variations in gender and ethnicity, as well as delineating hair fibre diameter, ellipticity, elasticity properties that collectively contribute to the outcome of aged hair.", as well as Line 902-"Notably, various differentiations of the hair and scalp across gender and ethnicities that were addressed in the text should be contemplated as well."

Comment 4: Consider adding a flowchart summarizing all possible factors contributing to hair changes with age.

Response 4: Firstly, many thanks for this suggestion. After some consideration, I would like to point out that I had tried summarizing these ageing changes in Figure 3, which illustrates my comparison between the young scalp skin/hair and aged scalp skin/hair. In both the figure and caption, I have tried to distinguish the differences of young and aged scalp, these differences mentioned are intended to be an overview summary of the main points mentioned in the text.

Comment 5: Include a section discussing potential methods to reduce age-related hair changes, such as innovative shampoo or crème rinse ingredients, and lifestyle factors like sun exposure avoidance.

Response 5: Thanks very much for your valuable suggestions. Aligned with your comment, I have expanded Section 4 on Hair and Scalp Care to include your suggestions. My additions are as follows, Line 840-"These, in addition to more commonly seen caffeine, adenosine and biotin, can be formulated into hair products [217,218,219]. Although scientific evidence supporting these ingredients are varying and show limitations, requiring further optimization of dosage and delivery, as well as large-scale clinical validation. Alternatively, new and emerging stem cell-based and exosome therapies are still in the early stages of research and development, and are still considered to be experimental solutions [217]."

Comment 6: Add a "Future Perspectives" section to guide readers through potential research avenues and unresolved questions.

Response 6: Thanks for your suggestion, I also that my article needs to have more expansion of future perspectives on hair research. Hence I have edited my concluding remarks to include Line 912 onwards-"Equipped with more integrated knowledge, together with recent advances in omics platforms for the discovery of active ingredients, developing research on stem cell-based therapeutic solutions, optimisation of delivery systems of actives, they will all help drive future research in hair ageing. Ultimately, deeper and more well-rounded understanding can aid scientists to better match the performance of hair care formulations to the needs of their target consumers".

Comment 7: Ensure the manuscript complies with the journal’s plagiarism policy by reviewing the iThenticate report.

Response 7: Pending confirmation from internal team.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Arrector pili is latin 

Author Response

Comment 1: Arrector pili is latin 

Response 1: Thank you for your suggestion. To address your comment, I have now included in the text where 'arrector pili' is first observed, Line 85,"It consists of 1 – 4 hair follicles, a sebaceous gland and an arrector pili (latin) muscle [7]."

Reviewer 5 Report

Comments and Suggestions for Authors

Good response. Now, the manuscript is acceptable for publications.

Author Response

Comment 1: Good response. Now, the manuscript is acceptable for publications.

Response 1: Thanks for your kind comment, I also appreciate your suggestions given in Round 1.