Granzyme B contributes to subretinal fibrosis in neovascular age-related macular degeneration by modulating inflammation and epithelial-mesenchymal transition

Sep 28, 2026

Uploaded by nayy☆

More than half of patients with neovascular age-related macular degeneration (nAMD) develop subretinal fibrosis despite anti-VEGF therapy, and no direct treatment exists because underlying mechanisms remain unclear. The study tests the role of Granzyme B (GzmB), a serine protease elevated in nAMD eyes, using a two-stage laser-induced mouse model and in vitro ARPE-19 wound healing and bulk RNA sequencing to define effects on fibrosis, inflammation, EMT, and photoreceptor survival.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages23

Reading Time58 min

AccessFree to download

Abstract

Background

Methods

Results

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Introduction

Yoo et al. Journal of Neuroinflammation (2026) 23:1 Journal of Neuroinflammation [https://doi.org/10.1186/s12974-025-03619-9](https://doi.org/10.1186/s12974-025-03619-9) RESEARCH Open Access Granzyme B contributes to subretinal fibrosis in neovascular age-related macular degeneration by modulating inflammation and epithelial-mesenchymal transition Hyung-Suk Yoo1, Harshini Chakravarthy1, Jeanne Xi1, Jing Cui1, Zhengyuan Ai1, Amir Hosseini1, Jun Song2, NeilanTan1, Natalie Ma1, Ceres Zhou1, Boaz Li1, Robert Bell3,4, Anne Haegert3,4, Stephane Le Bihan3,4, Myeong Jin Ju1,2, David J. Granville5,6 and Joanne A. Matsubara 1* Abstract Background More than half of patients with neovascular age-related macular degeneration (nAMD) develop subretinal fibrosis, regardless of anti-vascular endothelial growth factor (VEGF) therapy. No treatment exists for subretinal fibrosis, as its pathophysiology remains elusive. Granzyme B (GzmB) is a serine protease elevated in human eyes with nAMD and contributes to choroidal neovascularization (CNV) . Although GzmB is involved in dermal and cardiac fibrosis, its role in subretinal fibrosis has yet to be elucidated. Methods Using the two-stage laser-induced mouse model of subretinal fibrosis, fibrotic lesions were induced in younger (3–6 months old) and older (7–14 months old) C57BL/6J and GzmB deficient mice. Seven days after the second laser, in vivo imaging of fibrotic lesions was performed using custom-built polarization diversity-optical coherence tomography (PD-OCT) system. Eyes were collected and used for either retina wholemounts or crosssections. Wholemounts were immunostained to assess pathological features of fibrosis and determine the size offibrotic lesions and mast cell counts within fibrotic lesions. Cross-sections were processed to quantify the levels of GzmB substrates within fibrotic lesions, namely pro-fibrotic thrombospondin-1 (TSP-1) and anti-fibrotic decorin (DCN), the extent of macrophage-to-myofibroblast transition (MMT), activation of astrocytes/Müller cells and finally photoreceptor cell death. ARPE-19 wound healing assay was performed to study the direct role of GzmB in RPE wound healing in vitro. GzmB-mediated transcriptional changes in ARPE-19 were determined by performing bulk RNA sequencing. Immunocytochemistry was performed to assess epithelial-mesenchymal transition (EMT) . Results GzmB deficiency resulted in smaller fibrotic lesions in older mice and was associated with decreased levelsofTSP-1 and increased levels of DCN within fibrotic lesions. It also led to increased MMT but reduced mast cell counts within fibrotic lesions, which was correlated with reduced photoreceptor cell death. In ARPE-19, exogenous *Correspondence: Joanne A. Matsubara [jms@mail.ubc.ca](jms@mail.ubc.ca) Full list of author information is available at the end of the article © The Author(s) 2025, modified publication 2026. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit [http://creativecom](http://creativecom)[mons.org/licenses/by/4.0/](mons.org/licenses/by/4.0/.)[.](mons.org/licenses/by/4.0/.) Yoo et al. Journal of Neuroinflammation (2026) 23:1 Page 2 of 23 application of GzmB impaired wound closure and promoted partial EMT by s

FAQs

Why is subretinal fibrosis a major unmet need in nAMD?

More than half of nAMD patients develop subretinal fibrosis regardless of anti-VEGF therapy, and no treatment specifically targets it because its pathophysiology is not fully understood.

How did the researchers evaluate the role of Granzyme B (GzmB)?

They used a two-stage laser-induced mouse model of subretinal fibrosis, performed in vivo PD-OCT imaging, quantified fibrosis and immune features in retinal wholemounts and cross-sections, and tested direct effects in ARPE-19 wound healing with EMT readouts and bulk RNA sequencing.

What were the key findings when GzmB was deficient?

GzmB deficiency produced smaller fibrotic lesions in older mice, decreased TSP-1 and increased decorin in lesions, increased macrophage-to-myofibroblast transition while reducing mast cell counts, and correlated with reduced photoreceptor cell death.

Sep 28, 2026

Uploaded by nayy☆