Old age promotes retinal fibrosis in choroidal neovascularization through circulating fibrocytes and profibrotic macrophages

Abstract

Background Retinal fibrosis affects 40–70% of neovascular age-related macular degeneration patients. This study investigated the effect of ageing on subretinal fibrosis secondary to choroidal neovascularization and the mechanism of action. Methods Subretinal fibrosis was induced in young (2.5-month) and aged (15–16-month) C57BL/6J mice using the two-stage laser protocol. Five and 30 days later, eyes were collected and stained for CD45 and collagen-1 and observed by confocal microscopy. Fibrocytes (CD45+collagen-1+) were detected in the bone marrow (BM), blood and fibrotic lesions by flow cytometry and confocal microscopy, respectively. BM-derived macrophages (BMDMs) were cultured from young and aged mice with or without TGF-β1 (10 ng/mL) treatment. The expression of mesenchymal marker αSMA (Acta2), fibronectin (Fn1) and collagen-1 (Col1a1) was examined by qPCR and immunocytochemistry, whereas cytokine/chemokine production was measured using the Luminex multiplex cytokine assay. BM were transplanted from 22-month (Ly5.2) aged mice into 2.5-month (Ly5.1) young mice and vice versa. Six weeks later, subretinal fibrosis was induced in recipient mice and eyes were collected for evaluation of fibrotic lesion size. Results Under normal conditions, the number of circulating fibrocytes (CD45+collagen-1+) and the expression levels of Tgfb1, Col1a1, Acta2 and Fn1 in BMDMs were significantly higher in aged mice compared to young mice. Induction of subretinal fibrosis significantly increased the number of circulating fibrocytes, enhanced the expression of Col1a1, Acta2 and Fn1 and the production of soluble urokinase plasminogen activator surface receptor (suPAR) but decreased the production of CXCL10 in BMDMs. BMDMs from aged subretinal fibrosis mice produced significantly higher levels of VEGF, angiopoietin-2 and osteopontin than cells from young subretinal fibrosis mice. The subretinal fibrotic lesion in 15–16-month aged mice was 62% larger than that in 2.5-month young mice. The lesion in aged mice contained a significantly higher number of fibrocytes compared to that in young mice. The number of circulating fibrocytes positively correlated with the size of subretinal fibrotic lesion. Transplantation of BM from aged mice significantly increased subretinal fibrosis in young mice. Conclusions A retina–BM–blood–retina pathway of fibrocyte/macrophage recruitment exists during retinal injury. Ageing promotes subretinal fibrosis through higher numbers of circulating fibrocytes and profibrotic potential of BM-derived macrophages.

Wnt5a/β-catenin-mediated epithelial-mesenchymal transition: a key driver of subretinal fibrosis in neovascular age-related macular degeneration

“…The underlying mechanisms of subretinal fibrosis secondary to nAMD are complicated and remain incompletely elucidated. Extensive literature corroborated the involvement of additional factors, such as pericyte-myofibroblast transition (PMT) [ 53 ], EndMT [ 54 ], activated microglia [ 55 ], macrophages [ 56 ] and Müller glia [ 57 ] in the laser-induced CNV mouse model, which contribute to the accumulation of differentiated myofibroblasts and deposition of ECM, ultimately leading to fibrosis formation in nAMD. Therefore, the contribution of Wnt5a or Wnt/β-catenin in the MT of other cell types during subretinal fibrosis remains to be elucidated.…”

Analysis of shared ceRNA networks and related-hub genes in rats with primary and secondary photoreceptor degeneration

“…The study reported that the miR-128 expression was significantly lower in patients with Ikzf1 deletion than those without Ikzf1 deletion in B-cell precursor acute lymphoblastic leukemia ( Krzanowski et al, 2017 ). Importantly, these hub genes not only participate in immune regulation but also play important roles in neurodegenerative diseases through the ceRNA network regulation ( Javed et al, 2023 ; Yi et al, 2023 ). Qin et al (2023) revealed that miR-6734-3p and its target mRNA Cyth4 expression were correlated with patients’ age in Alzheimer’s disease.…”

Aging in Ocular Blood Vessels: Molecular Insights and the Role of Oxidative Stress

“…Aging, a major risk factor for fibrotic processes, contributes to organ fibrosis incidence, particularly evident in proliferative diabetic retinopathy and neovascular age-related macular degeneration (nAMD). Fibrosis-related conditions including nAMD and choroidal neovascularization (CNV), secondary to other eye diseases, with aging promoting CNV-induced subretinal fibrosis [55]. Human choroidal vasculature undergoes aging changes, evidenced by age-related decreases in overall choroidal thickness, choriocapillaris density, vessel diameter, and choroidal blood flow.…”