The role of the mitogen-activated protein kinase (MAPK) pathway in choroidal neovascularization (CNV) remains unclear. This study investigates the involvement of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 pathways in CNV development, as well as the therapeutic potential of sprouty 2 (SPRY2), an MAPK inhibitor, in a laser-induced mouse model. The expressions of ERK, JNK, and p38 proteins were analyzed using Western blotting and immunostaining. Immunofluorescence imaging revealed increased p-ERK and p-JNK expression in the retina, retinal pigment epithelium (RPE), and choroid up to day 7. Co-immunostaining showed p-ERK colocalized with CD31, CD11b, F4/80, cytokeratin, and GFAP in the retina, while p-JNK and p-p38 were associated with angiogenesis and inflammation throughout the retina and choroid. Compared to aflibercept, SPRY2 administration significantly inhibited CNV lesions, endothelial proliferation, fibrosis, and apoptosis, while better-preserving RPE integrity. SPRY2-treated mice showed a stronger reduction in CNV-related inflammation, epithelial–mesenchymal transition, and photoreceptor apoptosis. These results highlight the MAPK pathway’s role in CNV pathogenesis, with ERK primarily mediating Müller cell gliosis and JNK, contributing to angiogenesis and inflammation. SPRY2 effectively suppressed CNV lesions, supporting its potential as a therapeutic target for CNV treatment via MAPK pathway modulation.

To address the shortcomings of existing anti-VEGF monotherapy in neovascular age-related macular degeneration (nAMD), we investigated the therapeutic capabilities of exosomes obtained from human induced pluripotent stem cell (hiPSC)-derived retinal organoids in a mouse model of laser-induced choroidal neovascularization (CNV). To evaluate Retinal Organoid-derived exosome (RO-Exo) distribution after intravitreal (IVT) injection, calcein-labeled RO-Exo was observed using confocal microscopy. CNV was induced in C57BL/6 J mice by laser photocoagulation. RO-Exo was isolated from retinal organoids (differentiation days 55–65) and injected 5 days post-laser. Therapeutic efficacy was evaluated on day 12. Vascular leakage and CNV size were assessed by angiography and CD31 immunostaining. We also examined HIF-1α/VEGF-A expression (Western blotting), Retinal Pigment Epithelium (RPE) integrity markers (immunofluorescence staining for α-SMA, fibronectin, and ZO-1), and the activation of the Mitogen-Activated Protein Kinase (MAPK) pathway (phospho-ERK, -p38, -JNK) in CNV lesions. After IVT injection, RO-Exo migrated to the RPE layer, showing high retinotropic distribution. In the CNV model, RO-Exo significantly reduced vascular leakage and CNV size, with greater suppression of HIF-1α and VEGFA expression than aflibercept, the standard-of-care anti-VEGF drug. CD31-positive vasculature was decreased, accompanied by downregulation of fibronectin (a fibrotic marker) and restoration of RPE hexagonality and integrity. Furthermore, RO-Exo inhibited the activation of ERK, P38, and JNK in CNV lesions. Our study results demonstrate that RO-Exo exhibits multi-target therapeutic effects—including anti-angiogenic, anti-fibrotic, and neuroprotective actions—offering a promising alternative to conventional anti-VEGF therapy for nAMD.