Multimodal imaging and electroretinography highlights the role of VEGF in the laser-induced subretinal fibrosis of monkey

Subretinal fibrosis secondary to neovascular age-related macular degeneration: mechanisms and potential therapeutic targets

Subretinal fibrosis is the end-stage sequelae of neovascular age-related macular degeneration. It causes local damage to photoreceptors, retinal pigment epithelium, and choroidal vessels, which leads to permanent central vision loss of patients with neovascular age-related macular degeneration. The pathogenesis of subretinal fibrosis is complex, and the underlying mechanisms are largely unknown. Therefore, there are no effective treatment options. A thorough understanding of the pathogenesis of subretinal fibrosis and its related mechanisms is important to elucidate its complications and explore potential treatments. The current article reviews several aspects of subretinal fibrosis, including the current understanding on the relationship between neovascular age-related macular degeneration and subretinal fibrosis; multimodal imaging techniques for subretinal fibrosis; animal models for studying subretinal fibrosis; cellular and non-cellular constituents of subretinal fibrosis; pathophysiological mechanisms involved in subretinal fibrosis, such as aging, infiltration of macrophages, different sources of mesenchymal transition to myofibroblast, and activation of complement system and immune cells; and several key molecules and signaling pathways participating in the pathogenesis of subretinal fibrosis, such as vascular endothelial growth factor, connective tissue growth factor, fibroblast growth factor 2, platelet-derived growth factor and platelet-derived growth factor receptor-β, transforming growth factor-β signaling pathway, Wnt signaling pathway, and the axis of heat shock protein 70-Toll-like receptors 2/4-interleukin-10. This review will improve the understanding of the pathogenesis of subretinal fibrosis, allow the discovery of molecular targets, and explore potential treatments for the management of subretinal fibrosis.

Aqueous humor cytokine levels in patients with subretinal fibrosis in neovascular age-related macular degeneration

PURPOSE

To investigate aqueous humor cytokine levels in neovascular age-related macular degeneration (nAMD) patients with subretinal fibrosis and to explore the relationship between cytokine levels and disease severity.

METHODS

The aqueous humor samples were collected from 16 eyes with subretinal fibrosis due to nAMD (SRFi group), 33 eyes with nAMD without subretinal fibrosis (nAMD group) and 28 eyes with cataract patients (control group). Clinical samples were analyzed for 5 cytokines,including vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), basic fibroblast growth factor (bFGF), transforming growth factor-α (TGF-α), platelet-derived growth factor-BB (PDGF-BB).

RESULTS

Aqueous humor cytokines VEGF and bFGF were significantly higher in nAMD patients than controls (all P < 0.05), and VEGF, bFGF and TGF-α levels were significantly higher in SRFi patients than controls (all P < 0.05). No significant differences in 4 cytokine levels were observed between nAMD and SRFi patients in aqueous humor. We also identified a positive correlation between the aqueous humor levels of IL-6 and VEGF in the SRFi group, while bFGF and TGF-α in the nAMD group. Moreover, VEGF levels were strongly related to BCVA, and bFGF levels were positively related to the maximum thickness of subretinal hyperreflective material (SHRM) in fibrosis due to nAMD.

CONCLUSION

VEGF and bFGF levels in aqueous humor were elevated in macular neovascularization with and without subretinal fibrosis. TGF-α levels exclusively differed in neovascular AMD with fibrosis. Cytokines are distributed differently and play a synergistic role in different stages (angiogenesis and fibrogenesis) of nAMD. The bFGF levels could predict the negative prognosis in fibrosis due to nAMD.

LncRNA XIST facilitates hypertrophy of ligamentum flavum by activating VEGFA-mediated autophagy through sponging miR-302b-3p

BACKGROUND

Increasing evidences have shown that long non-coding RNAs (lncRNAs) display crucial regulatory roles in the occurrence and development of numerous diseases. However, the function and underlying mechanisms of lncRNAs in hypertrophy of ligamentum flavum (HLF) have not been report.

METHODS

The integrated analysis of lncRNAs sequencing, bioinformatics analysis and real-time quantitative PCR were used to identify the key lncRNAs involved in HLF progression. Gain- and loss-function experiments were used to explore the functions of lncRNA X inactive specific transcript (XIST) in HLF. Mechanistically, bioinformatics binding site analysis, RNA pull-down, dual-luciferase reporter assay, and rescue experiments were utilized to investigate the mechanism by which XIST acts as a molecular sponge of miR-302b-3p to regulate VEGFA-mediated autophagy.

RESULTS

We identified that XIST was outstandingly upregulated in HLF tissues and cells. Moreover, the up-regulation of XIST strongly correlated with the thinness and fibrosis degree of LF in LSCS patients. Functionally, knockdown of XIST drastically inhibited proliferation, anti-apoptosis, fibrosis and autophagy of HLF cells in vitro and suppressed hypertrophy and fibrosis of LF tissues in vivo. Intestinally, we uncovered that overexpression of XIST significantly promoted proliferation, anti-apoptosis and fibrosis ability of HLF cells by activating autophagy. Mechanistic studies illustrated that XIST directly medullated the VEGFA-mediated autophagy through sponging miR-302b-3p, thereby enhancing the development and progression of HLF.

CONCLUSION

Our findings highlighted that the XIST/miR-302b-3p/VEGFA-mediated autophagy axis is involved in development and progression of HLF. At the same time, this study will complement the blank of lncRNA expression profiles in HLF, which laid the foundation for further exploration of the relationship between lncRNAs and HLF in the future.

YAP is critical to inflammation, endothelial-mesenchymal transition and subretinal fibrosis in experimental choroidal neovascularization

Subretinal fibrosis causes local damage to the retina and irreversible vision loss, as the final stage of neovascular age-related macular degeneration (nAMD). More recently, the endothelial-to-mesenchymal transition (EndoMT) has been considered one of the most significant sources of myofibroblasts in subretinal fibrosis, though the underpinning molecular mechanisms remain unclear. In this study, a series of experiments were performed to test the hypothesis that Yes-associated protein (YAP) may be involved in EndoMT and subretinal fibrosis. We demonstrated that transforming growth factor (TGF)-β2 stimulation induces YAP dephosphorylation (activated) and nuclear transcription in human umbilical vein endothelial cells (HUVECs) by increasing reactive oxygen species (ROS) levels. Moreover, TGF-β2-mediated EndoMT and proinflammatory cytokine production in HUVECs were reduced by ROS clearance or YAP knockdown. Furthermore, the severity of subretinal fibrosis was markedly relieved by intravitreal administration of a small interfering RNA targeting YAP in the mouse laser-induced choroidal neovascularization (CNV) model. Our findings provide novel insights into a previously unknown effect of YAP on the EndoMT process and reveal YAP as a potential target for suppressing CNV-related subretinal fibrosis and protect vision.