Platelet-Rich Plasma-Derived Exosome Olfactory Cleft Injection for Treating Traumatic Olfactory Dysfunction
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors- In introduction This sentence, Head trauma leads the etiologies of olfactory disorder, should be expanded with additional discussion
- These abbrevations should beclarified ( TGF-beta, EGF, VEGF, NGF and IG)
- First line in Page 2, there are error dlete number 9
- Schedule proposal of the tested treatment should be clarified and provided
Author Response
Author’s response to reviewers' comments：
First of all, I would like to express my sincere gratitude to the reviewers for valuable comments. I have checked and revised them one by one. Thank you again! The reply is as follows:
- In introduction This sentence, Head trauma leads the etiologies of olfactory disorder, should be expanded with additional discussion
Response 1: Thank you for the insightful comment. We have expanded the sentence “Head trauma leads the etiologies of olfactory disorder.” in the section of Introduction.
Revision 1: Head trauma is one of the leading causes of persistent olfactory dysfunction, and its pathophysiology is often multifactorial [1]. The pathophysiology of traumatic olfactory dysfunction includes the fact that the olfactory nerves are sheared on the cribriform plate and the central olfactory structures are injured [2]. The prevalence of traumatic olfactory dysfunction varies according to the severity of the injury, ranging from approximately 5–30% after mild traumatic brain injury to more than 50% in patients with severe head trauma[3,4]. Although approximately one third of patients may recover spontaneously, recovery is often incomplete and usually occurs within the first year after trauma; therefore, persistent anosmia beyond 1 to 2 years generally indicates a poorer prognosis[5,6]. (Line 27-36)
- These abbrevations should be clarified ( TGF-beta, EGF, VEGF, NGF and IG)
Response 2: We appreciate this suggestion and these abbreviations have been clarified.
Revision 2: PRP contains growth factors such as transforming growth factor beta (TGF-beta), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), nerve growth factor (NGF), and insulin-like growth factor (IGF) and has been considered to have pro-regenerative properties[19,20]. (Line 46-49)
- First line in Page 2, there are error dlete number 9.
.Response 3: Thank you for pointing this out. We have deleted 9.
Revision 3: PRP olfactory cleft injection was also used to treat traumatic olfactory dysfunction in 2 small cohort studies that reported safe and promising results[22,23]. (Line 51-53)
- Schedule proposal of the tested treatment should be clarified and provided
Response: We appreciate this helpful comment. The schedule proposal of the tested treatment has been provided and clarified in the figure 3.
Revision: To improve her olfactory function, she opted to receive four additional PRE olfactory cleft injections during the period from April to October 2025 at 2-month intervals. (Line 93-95)
Reviewer 2 Report
Comments and Suggestions for AuthorsThe topic is interesting, especially the use of platelet-rich plasma-derived exosomes (PREs) for traumatic olfactory dysfunction (TOD). However, the manuscript has major issues regarding scientific rigor, methodology description, interpretation of results, language quality, and overstatement of conclusions from a single case.
I have the following comments:
-The manuscript claims PREs may be superior to PRP due to stability and lower immunogenicity, but the mechanistic explanation remains “shallow”. The authors should better explain why PREs would succeed after inadequate response to PRP, how exosomal cargo may influence olfactory neuroregeneration and whether PREs are expected to act locally on olfactory epithelium, olfactory neurons, or central pathways. The Discussion should include a more focused mechanistic framework supported by recent literature.
-The manuscript repeatedly implies efficacy of PRE injections despite reporting only one case. Improvement cannot confidently be attributed to PRE because spontaneous delayed recovery remains possible, prolonged olfactory training may contribute, and cumulative effects of prior PRP/HA injections cannot be excluded. The wording throughout the manuscript should be toned down.
-The chronology is hard to follow and should be summarized in a table or figure including date of trauma, timing of OT, PRP/HA injections, PRE injections, smell testing dates, MRI timing, and the clinical response after each intervention.
-The manuscript relies almost exclusively on PEA threshold values. The authors should clarify clinical interpretation of threshold changes, minimally clinically important difference, and reproducibility of measurements. In addition, the unilateral results remain poor despite bilateral improvement, which requires discussion.
-Subjective improvement is mentioned, but no validated questionnaire was used. Inclusion of patient-reported outcome measures would substantially strengthen the report.
-The exosome preparation section lacks critical information like exosome isolation method details, particle concentration, particle size distribution, markers used for characterization, sterility testing, storage duration, and release criteria. Reliance on “previous article” is insufficient for reproducibility.
-The authors state no adverse effects occurred, but systematic safety assessment is absent. Please clarify whether nasal endoscopy follow-up was performed, whether infection, bleeding, crusting, headache, or worsening smell occurred, and the duration of post-treatment surveillance.
-The conclusion should emphasize hypothesis generation only. Current data do not support efficacy claims.
-There are two Figure 2 captions. Please correct the figure numbering.
-Injection figure should better identify anatomical landmarks.
-The manuscript should specify exact injection volume per side, needle type, injection depth, and whether injections were submucosal.
-The ethical approval date appears inconsistent with the study timeline: Please clarify whether retrospective approval was obtained.
-Please define all abbreviations at first use, including:
-The manuscript would benefit from a dedicated limitations paragraph instead of embedding limitations within the Discussion.
Comments on the Quality of English Language
There are numerous grammatical and typographical errors throughout the manuscript. Extensive English language editing is required.
Author Response
Author’s response to reviewers' comments：
First of all, I would like to express my sincere gratitude to the reviewers for valuable comments. I have checked and revised them one by one. Thank you again! The reply is as follows:
Comments 1: The manuscript claims PREs may be superior to PRP due to stability and lower immunogenicity, but the mechanistic explanation remains “shallow”. The authors should better explain why PREs would succeed after inadequate response to PRP, how exosomal cargo may influence olfactory neuroregeneration and whether PREs are expected to act locally on olfactory epithelium, olfactory neurons, or central pathways. The Discussion should include a more focused mechanistic framework supported by recent literature.
Response 1: Thank you for your comment. I have better explain why PREs would succeed after inadequate response to PRP by including a more focused mechanistic framework in the section Discussion.
Revision 1: The mechanistic differences between PRP and PRE may include several aspects. Exosomes are nanoscale extracellular vesicles that can fuse directly with recipient cells and deliver molecular cargo intracellularly. Therefore, its biologic effect may be more targeted and durable than the extracellular diffusion of soluble PRP growth factors [33]. PREs contain selected proteins, lipids, messenger RNAs, and microRNAs rather than the full plasma environment. This selective enrichment may be important if previous PRP failed because growth factors degraded too quickly, inflammatory plasma proteins counteracted the benefit, tissue penetration was insufficient, or neuronal signaling pathways needed intracellular reprogramming rather than extracellular stimulation [34]. Because exosomes are extremely small, they can diffuse through mucus, extracellular matrix, and damaged neuroepithelium more effectively than bulk PRP preparations [35]. Lines 254-265.
Comments 2: The manuscript repeatedly implies efficacy of PRE injections despite reporting only one case. Improvement cannot confidently be attributed to PRE because spontaneous delayed recovery remains possible, prolonged olfactory training may contribute, and cumulative effects of prior PRP/HA injections cannot be excluded. The wording throughout the manuscript should be toned down.
Response 2: I thank the reviewer for this important comment. The wording about efficacy of PRE injections throughout the manuscript has be toned down.
Revision 2: Conclusions: This study presents a case of traumatic olfactory dysfunction treated with PRE olfactory cleft injections, but no real conclusions can be drawn regarding the efficacy of PRE olfactory cleft injection on traumatic olfactory dysfunction by a single case report. Lines 19-22.
The statement in the section of Limitations “Nevertheless, the experience of this patient suggests that the use of PRE olfactory cleft injections may warrant further investigation as a treatment option for traumatic olfactory dysfunction.”has been deleted.
The statement in the section of Conclusions ”but PRE gave a better improvement in olfactory function”has been deleted.
Comments 3: The chronology is hard to follow and should be summarized in a table or figure including date of trauma, timing of OT, PRP/HA injections, PRE injections, smell testing dates, MRI timing, and the clinical response after each intervention.
Response 3: I thank the reviewer for this important comment. I have added a chronology figure to show date of trauma, timing of OT, PRP/HA injections, PRE injections, smell testing dates, MRI timing, and the clinical response after each intervention.
Revision 3: Figure 3
Comments 4: The manuscript relies almost exclusively on PEA threshold values. The authors should clarify clinical interpretation of threshold changes, minimally clinically important difference, and reproducibility of measurements. In addition, the unilateral results remain poor despite bilateral improvement, which requires discussion.
.Response 4: Thank you for this valuable comment. In the revised manuscript, we added clarification regarding the clinical interpretation of PEA threshold changes, including the current lack of a well-established minimally clinically important difference (MCID) and the need for cautious interpretation of threshold changes. We also included additional information on the reproducibility and reliability of PEA measurements. Regarding the discrepancy between bilateral and unilateral outcomes, we expanded the Discussion section to address potential explanations, including differences in sensory integration, side-specific deficits, measurement variability, and the possible influence of limited sample size on unilateral findings.
Revision 4: Although the PEA threshold test is widely used for the smell test and is commercially available as the Snap & Sniff test, a minimally clinically important difference for PEA thresholds has not yet been universally defined [30]. Additionally, the reliability of the test and the re-test is not reported in the Snap & Sniff test administrative manual. Therefore, the clinical interpretation of changes in the PEA threshold must be cautious. Regarding the discrepancy between the results of unilateral and bilateral tests, the change in bilateral threshold may reflect enhanced central sensory integration or the summation effects of unilateral testing. On the contrary, unilateral performance can remain limited due to possible side-specific deficits after head trauma. Lines 244-252.
Comments 5: Subjective improvement is mentioned, but no validated questionnaire was used. Inclusion of patient-reported outcome measures would substantially strengthen the report.
Response 5: I thank the reviewer for this important point. The patient has reported her olfactory function using a 10-point Visual Analog Scale. I added the scores in the section of Case Report.
Revision 5: A 10-point Visual Analog Scale (VAS) and the phenyl ethyl alcohol (PEA) odor detection threshold test were used to assess her smell function[30]. On August 24, 2022, The test results showed that VAS score was 1, and the bilateral and unilateral PEA thresholds were each -1. Lines 74-77.
The patient reported her olfactory function using a 10-point VAS, where 0 indicated a complete loss of olfactory function and 10 represented normal olfactory function. Lines 121-122.
Comments 6: The exosome preparation section lacks critical information like exosome isolation method details, particle concentration, particle size distribution, markers used for characterization, sterility testing, storage duration, and release criteria. Reliance on “previous article” is insufficient for reproducibility.
Response 6: I thank the reviewer for this valuable comment. Because PREs were produced by a local company, I only drew the patient’ blood into a bag, and transported the bag to the company for production of PREs. I asked the company to give me the information like exosome isolation method details, particle concentration, particle size distribution, markers used for characterization, sterility testing, storage duration, and release criteria. However, the company did not respond to my request. This is why I referenced to their previous article which mentioned some information about procedures for both collection and purification of exosomes.
Comments 7: The authors state no adverse effects occurred, but systematic safety assessment is absent. Please clarify whether nasal endoscopy follow-up was performed, whether infection, bleeding, crusting, headache, or worsening smell occurred, and the duration of post-treatment surveillance.
Response 7: I thank the reviewer for noting the need for systematic safety assessment. I added a paragraph to describe our procedures for systematic safety assessment.
Revision 7: Since PRE olfactory cleft injections were performed under local anesthesia, the patient was asked about the severity of the pain of the procedures. Although she felt that the injected procedures were a little painful, she considered that the injection procedures were tolerable. After completing olfactory cleft injections, possible adverse effects were observed over a half-hour period. Mild epistaxis was observed after injected procedures, but no further procedure was performed to stop epistaxis. No headache was complained of. During each follow-up, she was asked about any adverse event related to PRE olfactory cleft injections, including a change in olfactory function, but no other severe adverse event was reported. She also received a rhinoscopic examination and PEA threshold test. No signs of wound infection, nasal crusting, or worsening of the smell were observed. Lines 106-116.
Comments 8: The conclusion should emphasize hypothesis generation only. Current data do not support efficacy claims.
Response 8: I thank the reviewer for this important comment. I have deleted the statements about efficacy claims.
Revision 8: Conclusions: This study presents a case of traumatic olfactory dysfunction treated with PRE olfactory cleft injections, but no real conclusions can be drawn regarding the efficacy of PRE olfactory cleft injection on traumatic olfactory dysfunction by a single case report. Lines 19-22.
The statement in the section of Conclusions ”but PRE gave a better improvement in olfactory function”has been deleted.
Comments 9: There are two Figure 2 captions. Please correct the figure numbering.
Response 9: I thank the reviewer for this comment. I have corrected the wrong figure numbering.
Revision 9: Figure 5. Platelet-rich exosome fluid was injected into the nasal septum. MT: middle turbinate; S: nasal septum; arrow: injection needle Lines 211-212.
Comments 10: Injection figure should better identify anatomical landmarks.
Response 10: I thank the reviewer for this comment. I have changed injection figure to better identify anatomical landmarks.
Revision 10: Figure 5
Comments 11: The manuscript should specify exact injection volume per side, needle type, injection depth, and whether injections were submucosal.
Response 11: I thank the reviewer for this comment. I have described injection procedures more clearly.
Revision 11: After removing the pledgets, a 2% xylocaine/epinephrine solution was then injected into the nasal septum and the middle turbinate using a 23 gauge spinal needle. Subsequently, an elevator was used to lateralize the middle turbinate to expose the olfactory cleft. Finally, approximately 2 cc of PRE fluid was injected into the upper middle region of the right nasal septum submucosally using a 23-gauge spinal needle, while approximately 1 cc of the fluid was injected into the medial surface of the right middle turbinates submucosally using a 23-gauge spinal needle. The same procedure was performed in the left nasal cavity (Figure 5) Lines 200-208.
Comments 12: The ethical approval date appears inconsistent with the study timeline: Please clarify whether retrospective approval was obtained.
Response 12: I thank the reviewer for this comment. I acquired the IRB proof on April 15, 2026 to perform a retrospective study of patients who received PRE olfactory cleft injection. Then, this lady gave her written informed consent to allow me to use her data for publication.
Comments 13: Please define all abbreviations at first use, including:
Response 13: I thank the reviewer for this comment. I have defined all abbreviations at first use in this manuscript.
Comments 14: The manuscript would benefit from a dedicated limitations paragraph instead of embedding limitations within the Discussion.
Response 14: I thank the reviewer for this comment. I have added a dedicated limitations paragraph in the section of Discussion.
Revision 10: Limitations Line 267.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have adequately addressed the major concerns. The revised manuscript now presents a more balanced interpretation of this single-case observation, appropriately emphasizing hypothesis generation rather than efficacy claims.
The addition of the mechanistic discussion, chronology figure, procedural details, safety assessment, and dedicated limitations section significantly improves the clarity.
The remaining limitation relates to incomplete characterization of the platelet-rich exosome preparation (particle concentration, size distribution, release criteria, etc.). The response is not ideal scientifically, but it is honest. Although the authors were unable to obtain this information from the manufacturer, this limitation should remain clearly acknowledged in the manuscript because it affects reproducibility and interpretation.
Comments on the Quality of English Language
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Author Response
Author’s response to reviewer’s comments：
First of all, I would like to express my sincere gratitude to the reviewer for valuable comments. I have checked and revised them one by one. Thank you again! The reply is as follows:
Comment 1: The authors have adequately addressed the major concerns. The revised manuscript now presents a more balanced interpretation of this single-case observation, appropriately emphasizing hypothesis generation rather than efficacy claims.
The addition of the mechanistic discussion, chronology figure, procedural details, safety assessment, and dedicated limitations section significantly improves the clarity.
Response 1: Thank you for your comment.
Comment 2: The remaining limitation relates to incomplete characterization of the platelet-rich exosome preparation (particle concentration, size distribution, release criteria, etc.). The response is not ideal scientifically, but it is honest. Although the authors were unable to obtain this information from the manufacturer, this limitation should remain clearly acknowledged in the manuscript because it affects reproducibility and interpretation.
Response 2: I thank the reviewer for your understanding. I have added the lack of the detailed information of their PRE preparation methods used in this case as a limitation.
Revision 2: Finally, the efficacy of PRE is significantly influenced by their preparation methods, primarily because different techniques can lead to substantial variations in their composition and concentration [36]. The manufacturer did not provide the detailed information of their PRE preparation methods used in this case. This makes it extremely challenging to compare the results of this case with others. Lines 277-281.
