Versatile hiPSC Models and Bioengineering Platforms for Investigation of Atrial Fibrosis and Fibrillation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The present review is quite extensive. Due to the length of the manuscript it is not easy to read.

Thus, the authors should include at least one schematic summary figure showing the most relevant issues.

It is unclear why the authors do  not include the concept of atrial cardiomyopathy in their text. The recent global consensus document might help. Recently, Schotten et al published a similar review in Nature Cardiology Reviews 2025. What is truely different and new in the present manuscript compared to other reviews?  There are results on hematopoetic stem cells in Patients with AF ( Goette et al Circulation 2003). This aspect should be included.

 

V

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors Panahi et al review in detail several  human induced pluripotent stem cell (hiPSC) based models for investigation of atrial fibrosis and atrial fibrillation and discuss the various techniques available to characterize the disease phenotype. The topic is interesting for the readers but there is a lot of scope for improvement in the review (especially in formatting) as highlighted in the following points:

• The current title of the review does not reflect the main text-suggest to update it to a more suitable title- My suggestion-  "Versatile hiPSC models and bioengineering platforms for investigation of atrial fibrosis and fibrillation".
• It would be better if the writing style is made uniform.
  • The authors keep switching between abbreviations (AF, ECM, CMs, CFs etc) and full forms (Atrial Fibrosis or atrial fibrillation, Extracellular Matrix, cardiomyocytes, cardiac fibroblasts etc) throughout the review.
  • Sometimes the font style changes in the draft- for eg – introduction – “pulmonary venous-LA junction”
  • sometimes the font color is different- Section 5.6.8.- font color is different in “atrial-specific ion channels- please update.

 

• Section 2.1 –
  • neurohumoral already includes hormone influence. So the sentence is a bit redundant- “neurohumoral regulation and hormonal influence”

 

• Section 2.2 –
  • Pls add references for statements such as– “primary human atrial cardiomyocytes rapidly de-differentiate in culture”

 

• Figure 1-
  • it is misleading that there are still iPSCs at day 7 of the differentiation timeline
  • If the metabolic selection is working efficiently then there should be a decrease of non-cardiomyocytes from day 11 to 15. However if there is still non-cardiomyocytes remaining (as shown in the schematic) then this would proliferate over time until day 50 and be present in larger numbers compared to cardiomyocytes which exit cell cycle. This part in the schematic should be corrected.

 

• The authors describe various models (hiPSC-aCMs and EHTs) for investigating AFs. One limitation with these models is the long and costly production and thereafter the culture of the “mature” cells for final experiments which makes it a very lengthy experimental strategy. Such points have not been discussed- it is crucial to highlight limitations as well and not only comment on the advantages.
  • Ex vivo human living myocardial slices (PMID: 38442291, 39082743) is an important platform that has huge potential in this research. Biopsy material from patients with AF can be cultured for elucidating disease mechanism or drug screening. This technology was missing in the review and the authors should consider including it as well.
  • The authors did not refer to the cardiac organoid (PMID:35867781) model in this review as well which is a valuable tool for such research questions. Recent efforts have enabled achieving vascularization which drastically improves the translatability of these models in terms of studying disease development and progression (PMID: 40472086)

• Also, it would be useful to mention the advantages /disadvantages / downstream analysis methods which can be applied with them respectively in a tabular format- for eg for EHTs patch clamp is not feasible / high throughput drug screening is practically done on hiPSC-aCMs instead of EHT platform.

 

• Figure 2-
  • it is misleading that schematic shows “myofibroblasts” (after stress injury) even though the section is talking about differentiating hiPSCs into cardiac fibroblasts. Please revise the figure legend to reflect this better.
  • Also in previous figure the retinoic acid was abbreviated and here not- kindly use a uniform style.
• Section 4.1 : the title starts with “D Monolayer approach”- I think it should read “2D”
  • If the metabolic selection is working efficiently then there should be a decrease of non-cardiomyocytes from day 11 to 15 . However if there is still non-cardiomyocytes remaining (as shown in the schematic) then this would proliferate over time until day 50 and be present in larger numbers compared to cardiomyocytes which exit cell cycle. This part in the schematic should be corrected.
• Section 5.2 : the title has a type “D Bioprinting….” The “D” is a typo or missing a number 2D / 3D
• Page 18- The line (For eg, Niro et al 2024, successfully utilized……. fibrotic remodelling”) has been repeated twice – Please check and update
• Figure 4- please label which proteins have been stained in the image panel A. Blue is nuclei, green is sarcomeric protein (cTnT ? ) and what is red ?

 

 

Author Response

Please see attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Review of the manuscript entitled: “Examining the Role of Atrial Fibrosis in Augmenting Atrial Fibrillation Using hiPSCs and Bioengineering”. The manuscript presents a very extensive and well-documented review of the role of atrial fibrosis in the pathogenesis of atrial fibrillation (AF), with particular emphasis on the use of human induced pluripotent stem cells (hiPSCs) and modern bioengineering technologies. The topic is timely, interdisciplinary, and of high translational value, bridging experimental cardiology, tissue engineering, and regenerative medicine. The text is written in correct scientific language, well organized and detailed; however, in its current form it resembles a methodological compendium rather than a concise and critical literature review. Therefore, it requires shortening, restructuring, and a deeper interpretative discussion.

Below I provide a more detailed review.

The manuscript does not include an abstract. It is unclear why the authors chose to omit this essential element of a scientific article. An abstract appears to be present in the submission system, so this may be a formatting error.

The manuscript has been prepared rather carelessly, which may reflect a lack of respect for the journal. For instance, on the first page the introductory text uses several different fonts — why? In addition, the citation style in the text is incorrect. While these may seem minor issues, they do indicate the authors’ attitude toward scientific work.

Both the introduction and the abstract lack a clearly defined objective. Why did the authors undertake this review? The purpose of the paper should appear early in the abstract, and in the case of the introduction, it should form its final paragraph. These are elementary principles of scientific writing. Moreover, the current introduction is too long; it would be better to divide it into separate sections such as Introduction and Atrial Fibrillation and ECM Remodeling.

I believe that the manuscript would benefit from the inclusion of several additional tables.

I very much appreciate the figures, but their captions should be enriched — at present, they consist only of titles.

Some sections (e.g., 5.5) lack any references and should be supplemented.

In Figure 4, there are no details regarding magnification, etc. Such data must be provided in the legend. If the figure was adapted from another publication, the source and permission for reuse must be clearly indicated.

The manuscript also lacks a statement specifying the individual contributions of each author.

Most sections (especially 3.2, 4.2, and 5.6) are purely descriptive. There is a need for critical elements — for example, an evaluation of which models best reproduce specific aspects of fibrosis (electrophysiological, metabolic, structural) and which have limitations. A summary table comparing in vivo, ex vivo, in vitro, and hiPSC-based models, with their respective strengths and weaknesses, would be a good solution.

The article discusses the molecular basis of fibrosis and atrial remodeling only to a limited extent. It would be valuable to include a concise overview of key signaling pathways (TGF-β/SMAD, Wnt/β-catenin, ROS, and ion-channel remodeling) that link fibroblast activation to conduction abnormalities in AF.

The introduction presents up-to-date epidemiological data, but it could be complemented with newer information from the Global Burden of Disease 2023 report. In general, the number of references from 2022–2024 is quite limited and should be increased.

Abbreviations (MEA, HS-OM, LEAP) should be explained at first mention.

In the section on bioprinting (4.2.3), it would be advisable to add numerical data on oxygen diffusion limits (>300 µm) and to cite examples of constructs with embedded microvascular networks.

In section 5.6.10 (Ca²⁺ handling), the authors could mention the role of RyR2 phosphorylation and SERCA dysfunction in AF mechanisms.

Author Response

Please see attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

In my opinion, the authors have adequately revised the manuscript, and I accept it for publication. I believe that the Highlights section is unnecessary, but it can be removed at later stages after acceptance. The abstract is scientifically sound but somewhat too long; it should be around 250 words. If the Editor considers it too lengthy, they may change my decision to “minor revision” so that the authors can slightly shorten the abstract.