On 2023-08-22 12:27:24, user Bruno Pelozin wrote:
This assessment of a preprint is part of a research evaluation course within my Ph.D. program, in which I was tasked with selecting a preprint manuscript to formulate questions and suggestions for improvement. I was delighted to come across your article, and the experience of reading it has been truly remarkable. It has been a rewarding endeavor to contemplate potential alternatives and novel experiments that could further enhance the significance of your work. I hope that you receive this message and find value in these collaborative insights.
The lncRNA Sweetheart regulates compensatory cardiac hypertrophy after myocardial injury.
In the elegant study by Rogala et al., they demonstrated that the expression of the long non-coding RNA "sweetheart RNA" (Swhtr), which is expressed in the same region as the crucial transcription factor Nkx2-5, exerts favorable effects on both cardiac function and morphology in animals subjected to left anterior descending artery ligation (LAD). The Swhtr lncRNA is chromatin-localized, and although its deletion does not induce cardiac structural changes during embryonic phases or fetal lethality, nor yield structural or functional cardiac modifications in adulthood, its recovery in transgenic animals induced an enhancement in cardiac morphology and function following myocardial infarction induced by LAD surgery. Although its precise function remains undefined, this manuscript suggests its influence on genes associated with the NKX2-5 transcription factor.
Major
1- I found the introduction to be quite engaging. However, enhancing the overall coherence of the work could involve establishing a more explicit connection between collagen deposition, scar formation, and fibrosis within the context of a myocardial infarction model. Addressing this interrelationship in the introduction would be particularly advantageous, given its enduring significance over time, as opposed to the relatively less prevalent occurrence of compensatory hypertrophy.
2- In the study conducted by Werber et al. (2014), the group generated a comprehensive dataset elucidating the transcriptional landscape of cardiac tissue. Notably, they identified a specific RNA molecule that exhibits exclusive expression within the heart tissue context. Conversely, in the context of the present research, the rationale behind investigating the lncRNA Swhtr appears to lack clarity Establishing a logical connection with the Nkx2-5 factor could potentially serve to justify the selection of the lncRNA under investigation. This strategic link could bolster the rationale for studying lncRNA Swhtr and its potential relevance within the broader context of cardiac biology.
3- I appreciate the researchers' elegant approach in illustrating the spatial distribution of lncRNA across diverse embryonic stages. Nevertheless, I am left wondering whether the researchers considered expanding their analysis to encompass additional developmental stages, such as the newborn (NB) phase. This query stems from the findings highlighted in the current study, where the NB phase emerges as the highest lncRNA window expression and, conceivably, a pivotal period of heightened lncRNA activity (Bridges et al., 2021; Gomes et al., 2017). Remarkably, this pattern aligns with the outcomes derived from Fluorescence in Situ Hybridization (FISH) analyses conducted on cultured cardiac cells (Fig. 1H). Thus, contemplating lncRNA dynamics during the newborn phase could offer valuable insights into its plausible functional roles and accentuate its significance within the intricate framework of cardiac biology.
4- In figures 3A-F, the inclusion of a Sham WT control group would be highly valuable. While I recognize the challenges associated with conducting additional experiments for a new group, the incorporation of Sham animals could substantially enhance the interpretability of the results. Specifically, the comparison between disease-induced (LAD) effects on both WT and KO (Swhtr3x/pA3xpA) groups and their corresponding Sham WT counterparts would offer insightful insights into survival rates and cardiac function data.
For instance, the introduction of a Sham WT group could illuminate noteworthy differences in ejection fraction. It is conceivable that the KO animals subjected to LAD would exhibit a potentially significant reduction in ejection fraction when contrasted with the healthy Sham WT group. In contrast, both the WT and Transgenic animals may not display statistically significant deviations from the Sham WT group, thereby accentuating the therapeutic benefits conferred by the treatment. Incorporating a Sham WT control group would contribute significantly to the robustness of the findings, allowing for a more comprehensive assessment of the treatment's efficacy and its impact on cardiac function under both normal and disease conditions.
5- I believe that a more comprehensive characterization of the animals subjected to LAD would greatly enrich the study. Showing fibrosis and hypertrophy could lead to more holistic understanding of the animals' phenotype. Also, presenting the expressions of specific collagen types, particularly collagen III, which typically manifests in the initial weeks following an infarction, would help. This additional analysis would provide a deeper insight into the fibrotic response triggered by the myocardial infarction and contribute to a comprehensive appreciation of the tissue remodeling process. Furthermore, the inclusion of molecular markers associated with cardiac hypertrophy would be a significant asset to the study.
6- Extending the observation period for animals subjected to LAD and tracking them until the development of heart failure would offer a comprehensive perspective on morphological and functional cardiac changes over time. This longitudinal approach holds the promise of uncovering the dynamic role of the identified lncRNA in disease progression, providing valuable insights into its potential as a modulator or indicator of pathological processes associated with heart failure.
7- An elegant dimension could be added to the study if the researchers were to explore the effects of lncRNA Swthr deletion and gain of function in alternate models of hypertrophy. Considering the potential role of this lncRNA in governing cardiac hypertrophy, examining its impact on both pathological and physiological hypertrophic scenarios could yield valuable insights. Employing the transverse aortic constriction (TAC) model for inducing pathological hypertrophy would provide a robust hypertrophic stimulus, while unveiling the lncRNA's effects in physiological hypertrophy through aerobic exercise sessions would establish a nuanced connection between hypertrophy modulation and lncRNA activity. By encompassing these distinct scenarios, the study could present a comprehensive perspective on lncRNA's role in different hypertrophic contexts, thereby enhancing our understanding of its regulatory influence on cardiac adaptation.
8- The utilization of cardiac tissue culture is indeed an intriguing aspect of the study. Expanding this approach, perhaps in future studies, to encompass diverse infarction zones, including border and remote areas, would not only enhance the study's sophistication but also provide invaluable insights into the nuanced RNA profile characteristics of distinct zones adapting to the pathological stimulus. Moreover, performing an RNA expression profile analysis within the hearts of transgenic animals subjected to LAD holds promise in uncovering potential gene alterations and regulatory effects mediated by the lncRNA. This multifaceted exploration could unravel a comprehensive landscape of gene expression changes triggered by the lncRNA, thereby contributing to a deeper understanding of its intricate role in the cardiac response to myocardial infarction.
Minor
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I believe it would be important to use Medical Subject Headings for the keywords, I suggest: Cardiac hypertrophy, long non-coding RNA, myocardial infarction.
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In figures 1C-E the researchers interestingly use the lacZ reporter technique. It would be interesting and necessary to present the technique used in the methods.
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The sentence to describe Swhtr labeling in heart and other tissue was a bit confusing and could be improved in clarity (line 199-122).
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In Figure 1F, I believe there was a significant difference; if possible, provide the statistical symbol. Also in figure F, did the authors use any housekeeping gene to correct the expression? I think it would be more interesting to show the relative expression versus the absolute.
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During the manuscript, Swhtr and Swhtr lncRNA are used, I particularly think the name followed by lncRNA is more elegant.
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I believe that if the 1G figure were presented with separate bars, it will make the result much easier to understand.
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I believe it would make the text easier to understand if 3G figure were moved to position 3B
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It would be very interesting to demonstrate in figure 3H, in addition to the knock-out and Tg, also the LAD surgery and the time course.
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Line 218, I think you addressed the wrong image (is it 3G?).
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In the methods it would be important to define the term ES cells and mESCs (Embryonic stem cells) (line 342); Line 415, 465, 466, 467 use qPCR as in the rest of manuscript. It would be important to state in the manuscript how much tissue or cells were used for RNA extraction. It would also be nice to tell in the body of the text the time it took to extract the tissues, they are described in the methods, but I believe that it would enhance the work by being close to the results.
Werber M, Wittler L, Timmermann B, Grote P, Herrmann BG. The tissue-specific transcriptomic landscape of the mid-gestational mouse embryo. Development. 2014 Jun;141(11):2325-30. doi: 10.1242/dev.105858. Epub 2014 May 6. PMID: 24803591.
Singh, S. R., Hoffman, R. M., & Singh, A. (Eds.). (2021). Mouse Genetics. Methods in Molecular Biology. doi:10.1007/978-1-0716-1008-4
Bridges MC, Daulagala AC, Kourtidis A. LNCcation: lncRNA localization and function. J Cell Biol. 2021 Feb 1;220(2):e202009045. doi: 10.1083/jcb.202009045. PMID: 33464299; PMCID: PMC7816648.
Gomes CPC, Spencer H, Ford KL, Michel LYM, Baker AH, Emanueli C, Balligand JL, Devaux Y; Cardiolinc network. The Function and Therapeutic Potential of Long Non-coding RNAs in Cardiovascular Development and Disease. Mol Ther Nucleic Acids. 2017 Sep 15;8:494-507. doi: 10.1016/j.omtn.2017.07.014. Epub 2017 Jul 28. PMID: 28918050; PMCID: PMC5565632.