Myocardial global longitudinal strain: An early indicator of cardiac interstitial fibrosis modified by spironolactone, in a unique hypertensive rat model

Catherine J. Leader; Mohammed Moharram; Sean Coffey; Ivan A. Sammut; Gerard W. Wilkins; Robert J. Walker

doi:10.1371/journal.pone.0220837

Peer Review History

Original SubmissionMay 29, 2019
5 Jul 2019 Decision Letter - Vincenzo Lionetti, Editor PONE-D-19-14918 Myocardial global longitudinal strain: an early indicator of cardiac interstitial fibrosis in a unique hypertensive rat model. PLOS ONE Dear Professor Walker, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. ============================== ACADEMIC EDITOR: All issues raised by expert reviewers are required. The authors should limit speculations and highlight limitations of the study. ============================== We would appreciate receiving your revised manuscript by Aug 19 2019 11:59PM. 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Note that authors should not be the sole named individuals responsible for ensuring data access. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: No ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: This article investigates the effect of spironolactone on cardiac function and fibrosis after induction of hypertension in a transgenic hypertensive rat model. The authors perfomes an advanced echocardiograpic evaluation assessing global longitudinal strain (myocardial and endocardial) that usually is not evaluated in the animal model. As the authors report GLS can give more information in particular in HFpEF where ejection fraction is preserved. The article is well written and the topic is relevant in clinical setting. There are some suggestions: - the authors should consider to add echocardiographic data of mass in Table 1: - the discussion section could be a little bit shortened - the are two figure 1 and no figure 2 - there are two figure 5 and no figure 4. Reviewer #2: This experimental study using a hypertensive rat model showed the reduction of myocardial fibrosis with spironolactone, showing the changes in left ventricular ejection fraction and longitudinal strain from speckle tracking echo. However, the findings do not provide novel insights as compared to previous studies referred. Comments 1. The title does not imply the aim and results exactly. The effect of spironolactone should be reflected in the title. 2. Myo-GLS is more sensitive to the myocardial fibrosis, as shown in Fig 5. However, in the mid portion of the myocardium, cardiac fiber may be located in the circumferential positions rather than longitudinal positions. Please explain the discrepancy between functional and pathological behaviors. 3. In addition, the transmural distribution of fibrosis is needed to conclude your findings. 4. This technique may have limitations in reproducibility of strain measurements. The intra- and inter-observers’ variabilities should be clarified. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes: Flora Pirozzi Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0220837.r001
Revision 1
12 Jul 2019 Author Response ACADEMIC EDITOR: All issues raised by expert reviewers are required. The authors should limit speculations and highlight limitations of the study. Response: Comments to the reviewers comments are detailed below. Changes made to manuscript both in PLOS ONE style as well as where requested. Reviewer #1: This article investigates the effect of spironolactone on cardiac function and fibrosis after induction of hypertension in a transgenic hypertensive rat model. The authors perfomes an advanced echocardiograpic evaluation assessing global longitudinal strain (myocardial and endocardial) that usually is not evaluated in the animal model. As the authors report GLS can give more information in particular in HFpEF where ejection fraction is preserved. The article is well written and the topic is relevant in clinical setting. There are some suggestions: - the authors should consider to add echocardiographic data of mass in Table 1: - the discussion section could be a little bit shortened - the are two figure 1 and no figure 2 - there are two figure 5 and no figure 4. Response: We thank the reviewer for her helpful comments. LV mass was considered but as this is also a derived calculation, it did not add any additional information, to what was already observed. So it has not been added. The discussion has been shortened where possible (see track change version). The incorrect labelling of the figures has been changed. Reviewer #2: This experimental study using a hypertensive rat model showed the reduction of myocardial fibrosis with spironolactone, showing the changes in left ventricular ejection fraction and longitudinal strain from speckle tracking echo. However, the findings do not provide novel insights as compared to previous studies referred. We would like to disagree with the reviewer. There are several important novel insights. Firstly we have reported the strong correlation between myo-GLS and the degree of cardiac interstitial fibrosis as seen histologically, confirming it as an important non-invasive means to assess cardiac fibrosis. This has not previously been reported. It is important to clearly define a normal range for ejection fraction in an animal model and not rely on a human range. We believe this is the first time it has been defined for an animal model. This also highlights the potential for this animal model as a model for HFpEF as identified by reviewer 1. Previous intervention studies have administered spironolactone (or other drugs) at the onset of hypertension, which does not reflect the clinical scenario where patients present with established hypertension and left ventricular hypertrophy. Our model more accurately reflects this. We used a dose for the rats equivalent to the standard human dose. Previous animal studies with spironolactone use supra-physiological doses (often 10 to 100 fold higher than what would be an equivalent human dose) and these are administered either subcutaneously (osmotic pumps) or intra-peritoneally, when spironolactone has no evidence for efficacy other than by oral administration as was used in this study. Comments 1. The title does not imply the aim and results exactly. The effect of spironolactone should be reflected in the title. Thank you for this. The title has been changed appropriately. 2. Myo-GLS is more sensitive to the myocardial fibrosis, as shown in Fig 5. However, in the mid portion of the myocardium, cardiac fiber may be located in the circumferential positions rather than longitudinal positions. Please explain the discrepancy between functional and pathological behaviors. Myocardial global longitudinal strain measures contractile activity in real-time, and cardiac fibers are not static, rather they contract in a 3 dimensional response. This is picked up and allowed for in the global longitudinal strain analysis. Therefore any alterations in contractility related to fibrosis would still be observed. 3. In addition, the transmural distribution of fibrosis is needed to conclude your findings. Serial sections were analysed for the extent of fibrosis and we focused on the myocardial component rather than including epi and endocardial regions as these were too small to be of significance. Figure 3 demonstrates the regions of interest. 4. This technique may have limitations in reproducibility of strain measurements. The intra- and inter-observers’ variabilities should be clarified. The echo analyses were undertaken blinded by two of the investigators (MM, SC). The inter-observer and intra-observer interclass variability correlation coefficients were 96% and 97% respectively. Attachments Attachment Submitted filename: PLos One response.docx https://doi.org/10.1371/journal.pone.0220837.r002
25 Jul 2019 Decision Letter - Vincenzo Lionetti, Editor Myocardial global longitudinal strain: an early indicator of cardiac interstitial fibrosis modified by spironolactone, in a unique hypertensive rat model. PONE-D-19-14918R1 Dear Dr. Walker, We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements. Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication. Shortly after the formal acceptance letter is sent, an invoice for payment will follow. 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With kind regards, Vincenzo Lionetti, M.D., PhD Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: (No Response) Reviewer #2: Authors politely addressed my questions and comments asked. The manuscript has been improved, then,I have no further comments. ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes: Flora Pirozzi Reviewer #2: No https://doi.org/10.1371/journal.pone.0220837.r003
Formally Accepted
2 Aug 2019 Acceptance Letter - Vincenzo Lionetti, Editor PONE-D-19-14918R1 Myocardial global longitudinal strain: an early indicator of cardiac interstitial fibrosis modified by spironolactone, in a unique hypertensive rat model. Dear Dr. Walker: I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. For any other questions or concerns, please email plosone@plos.org. Thank you for submitting your work to PLOS ONE. With kind regards, PLOS ONE Editorial Office Staff on behalf of Prof. Vincenzo Lionetti Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0220837.r004

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