Metformin Promotes Axonal Regeneration and Functional Recovery in Diabetic Rat Model of Sciatic Nerve Transection Injury
Round 1
Reviewer 1 Report
The article presented from Junxiong Ma et al., is not original, and the introduction should be extended.
Previous studies reported that metmorfin enhances Functional Recovery of Peripheral Nerve in Rats with Sciatic Nerve Crush Injury.
The authors should explain where is the novelty (is there?).
Liu L, Tian D, Liu C, Yu K, Bai J. Metformin Enhances Functional Recovery of Peripheral Nerve in Rats with Sciatic Nerve Crush Injury. Med Sci Monit. 2019;25:10067-10076. Published 2019 Dec 28. doi:10.12659/MSM.918277
Author Response
1. The article presented from Junxiong Ma et al., is not original, and the introduction should be extended.
Authors’ reply: We appreciate your constructive suggestions. We agree with you that novelty is important to present study. The article presented from Liu L et al., have reported that the role of autophagy induction by metformin in motor functions and peripheral nerve regeneration following sciatic nerve crush injury in rats. Metformin was also proved to have the capability of promoting nerve repair after crush injury in rats under non–diabetic condition. However, the promoting effect of metformin on nerve repair under the condition of nerve transection injury in diabetic rats is still not clear. We used different animal models to examine the sciatic nerve regeneration ability of metformin. We have added introduction on the significance and necessity of this study in the revised paper, which made the present study more clearly. Thank you again for your suggestions. Details see page 1-2 line 44-50.
2. Previous studies reported that metmorfin enhances Functional Recovery of Peripheral Nerve in Rats with Sciatic Nerve Crush Injury. The authors should explain where is the novelty (is there?). Liu L, Tian D, Liu C, Yu K, Bai J. Metformin Enhances Functional Recovery of Peripheral Nerve in Rats with Sciatic Nerve Crush Injury. Med Sci Monit. 2019;25:10067-10076. Published 2019 Dec 28. doi:10.12659/MSM.918277
Authors’ reply: Thank you for your comment. Liu L et al., have reported that the role of autophagy induction by metformin in motor functions and peripheral nerve regeneration following sciatic nerve crush injury in rats. Metformin was also proved to have the capability of promoting nerve repair after crush injury in rats under non–diabetic condition. However, the promoting effect of metformin on nerve repair under the condition of nerve transection injury in diabetic rats is still not clear. We used different animal models to examine the sciatic nerve regeneration ability of metformin. We have added introduction on the significance and necessity of this study in the revised paper, which made the present study more clearly. Thank you again for your comment. Details see page 1-2 line 44-50.
Reviewer 2 Report
In this manuscript, the authors use a variety of approaches to investigate the effect of metformin in a model of transection injury of the sciatic nerve in diabetic rats, they conclude that metformin possesses the capability of accelerating sciatic nerve repair after transection injury which might show the therapeutic potential of metformin in the treatment of nerve injuries among diabetes patients.
Minor changes:
- Figure 2B, typo “axions” in y axis.
- The flow would be better if the authors can consolidate Figure 1A-E with Figure 2 and consolidate Figure 1K-O with Figure 3.
- In Figure 3, missing alphabets “A” and “B”
- It would be much more organized if the font size (Line 186-189) and alphabets in each figure are in the same size throughout the entire paper, also the alphabets in the figure should be aligned.
- Regarding section 3.3, Figures 6A and 6b should be switched.
Author Response
Comments and Suggestions for Authors：
In this manuscript, the authors use a variety of approaches to investigate the effect of metformin in a model of transection injury of the sciatic nerve in diabetic rats, they conclude that metformin possesses the capability of accelerating sciatic nerve repair after transection injury which might show the therapeutic potential of metformin in the treatment of nerve injuries among diabetes patients.
Authors’ reply: Thank you for your valuable review of our work.
1) Figure 2B, typo “axions” in y axis.
Authors’ reply: Thank you for your correction，the “axions” in y axis have been amended to “axons” in the revised paper. Thank you again for your reminding. Details see Figure 1G.
2) The flow would be better if the authors can consolidate Figure 1A-E with Figure 2 and consolidate Figure 1K-O with Figure 3.
Authors’ reply: Thanks for your valuable suggestions. We have recombined the Figure 1, 2, and 3 in the revised paper. Details see Figure 1, 2.
3) In Figure 3, missing alphabets “A” and “B”
Authors’ reply: Thank you for your reminding. We have added alphabets “A” and “B” in the revised Figure 2. Details see Figure 2.
4) It would be much more organized if the font size (Line 186-189) and alphabets in each figure are in the same size throughout the entire paper, also the alphabets in the figure should be aligned.
Authors’ reply: Thanks for your valuable suggestions. We have amended the font size (Line 186-189) and alphabets in each figure in the revised paper, which made the present study more neatly. Thank you again for your suggestions. Details see Figure 1-5.
5) Regarding section 3.3, Figures 6A and 6b should be switched.
Authors’ reply: Thank you for your reminding. We have corrected the errors in the revised Figures 5. Details see Figure 5.
Reviewer 3 Report
This study describes the beneficial effect of metformin treatment on peripheral nerve regeneration in streptozotocin diabetic rats. Morphological, functional, behavioral and electrophysiological techniques were used to assess the progression of nerve regeneration after cutting and suturing the sciatic nerve. All of the measured parameters showed a significant effect of metformin treatment on nerve regeneration. Although the study is well designed, the manuscript needs to be improved by giving missing methodological details and considering some points to be clarified concerning the interpretation of the data.
Methods.
l. 55: Please give the date and identification number of the ethical permission.
l. 60: Please give the method of glucose determination, the number of rats and the mean ± S.E.M.
l. 63. Please give details of the surgical technique used to „suture” the sciatic nerve.
l. 77: Please give definitions/explanations of the "constants" given in the SFI formula.
l. 90: Please describe how was the paw on the operated side stimulated separately from the intact paw?
l. 117: Please give the mode of injection (glass micropipette, Hamilton syringe?).
l. 125: A brief description of the morphometric analysis should be provided, since this is crucial for the interpretation of the findings.
l. 128: Please give the precise site of specimen removal for the electron microscopic examinations.
l. 135. The method of measuring myelination and myelinated axon diameters should be given.
Results.
Figure 1.: Please give the segmental level of the spinal cord and ganglia shown in the figure.
Fig. 3. Please give the segmental levels of spinal cord and ganglia from which these data were collected. Please indicate the number of sections from which these data were obtained.
Discussion.
The data presented in this manuscript suggest a gradual recovery of function in the denervated skin and muscle which is enhanced by metformin treatment. The authors discussed their findings by assuming that this recovery may be attributed to regeneration of the lesioned sciatic nerve. Although this may be the case, the possibility cannot be excluded that sprouting of intact cutaneous nerves innervating adjacent skin regions may play a role in recovery of cutaneous sensation of the denervated skin (Diamond et al., Proc Natl Acad Sci U S A. 84:6596-600, 1987, doi: 10.1073/pnas.84.18.6596). Collateral sprouting of intact neighboring axons has been shown to significantly contribute to reinnervation of the denervated skin following lesions of hindlimb nerves in the rat (Devor et al., J Comp Neur, 185: 211-220, 1979, doi: 10.1002/cne.901850113; Lakatos et al., Front Physiol, 11:439, 2020, doi: 10.3389/fphys.2020.00439). Hence, this issue must be dealt with and discussed by the authors.
The manuscript would benefit from a stylistic and linguistic revision of the text.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 1 Report
The authors satisfied all my concerns, I would propose the acceptance in present form.
