Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors compare immune cell populations and the expression of genes associated with angiogenesis and extracellular matrix remodeling between patients with brain arteriovenous malformations (AVMs) and control subjects using the Molecular Signatures Database. Their analysis demonstrates an increased abundance of both lymphoid and myeloid cell populations in brain AVM specimens. Notably, myeloid cells exhibited increased expression of genes involved in angiogenesis and extracellular matrix remodeling, suggesting a potential role for these cells in AVM pathobiology.

Despite the relatively small sample size and the inherent limitation that transcriptional profiles do not necessarily reflect functional cellular activity, as appropriately acknowledged by the authors, these findings provide valuable insight into the molecular and immunologic landscape of brain AVMs. The observed association between myeloid cell activation and angiogenic and extracellular matrix remodeling pathways may contribute to a better understanding of AVM progression and mechanisms underlying hemorrhagic risk.

An additional limitation is the lack of detailed clinical and angioarchitectural information regarding the AVMs included in the analysis. Characteristics such as rupture status, lesion size, location, Spetzler-Martin grade, venous drainage pattern, and associated aneurysms could substantially influence the inflammatory microenvironment. In particular, ruptured AVMs are expected to exhibit a distinct inflammatory response compared with unruptured lesions, potentially confounding the observed transcriptional differences.

Overall, this study provides an important preliminary characterization of the immune microenvironment in brain AVMs and identifies promising biological pathways that warrant further investigation in larger, clinically well-characterized cohorts.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This is a small but interesting contribution, based on the analysis of already published data.

Major issues:

Highlights (line 19-20): "may actively contribute". It is more appropriate to say "are associated with", as the authors do not demonstrate causation.

Abstract, Results: "Compared with controlled tissue..." the authors state themselves (line 179) that this difference was not significant. This claim is thus not supported. "Extracellular matrix-related programs...", here p=0.09, so again, this is not significant.

2.7 Statistical analysis. Please provide a more detailed description: what exactly was compared using the Wilcoxon test, how many comparisons were made (and then what number was used for adjustment using BH)?

Limitations: The control tissue was derived from epileptic patients; epilepsy is known to contribute to neuroinflammation, BBB disfunction, and activation of microglia (https://www.ncbi.nlm.nih.gov/books/NBK609862/). How could it affect the results? Similarly, if the bAMVs patients had a history of say recent hemorrhage, could that affect the results?

Minor issues:

Please harmonize the nomenclature throughout the paper and figures. You use  'Proliferating T' in Figures 1b, 2a, 2b, 3a, and S2b, but 'Proliferating CD8 T' in Figures 1a, 3b, S2a, and S3b; 'Activated T' (Figures 1b, 2a, 2b, 3a, S2b), but  'Activated T cells' (Figures 1a, 3b, S2a, S3b);'Plasma cell' vs. 'Plasma cells', 'NK' vs. 'NK cells;, 'M1 like MDM' in Figure 1a vs. 'M1-like MDM' in Figure 1b, 'Plasma cell' and 'NK' (Figure 1a), but 'Plasma cells' and 'NK cells (Figure 2a).

What do error bars represent in Figure 2b? Standard deviation, standard error of the mean, confidence intervals?

Figure 3 and S3. Usually one star is used for p<0.05, so please do that and choose some other symbol for p<0.1.

Please use 'bAVMs' rather than 'Bavms' in section titles.

Author Response

Please see the attachment.

Author Response File: Author Response.docx