Dry eye disease (DED) is a complex ocular surface disorder characterized by tear film instability, chronic inflammation, and epithelial damage, for which current treatments remain limited. Marine-derived bioactive oligosaccharides have attracted increasing interest due to their diverse pharmacological activities and favorable safety profiles. In this study, we investigated the therapeutic potential of neoagarotetraose (NA4), a marine oligosaccharide derived from red algal agar, in a murine model of DED. DED was induced in eight-week-old female C57BL/6 mice by topical instillation of 0.2% benzalkonium chloride for seven consecutive days. NA4 was administered topically at concentrations of 125, 250, and 500 mg/L. Therapeutic outcomes were evaluated by tear secretion, corneal fluorescein staining, histopathological analysis, immunofluorescence staining for Ki67, F4/80, IL-1β, IL-6, and TNF-α, TUNEL assay for apoptosis, and ELISA for cytokine levels. NA4 treatment significantly improved tear secretion and reduced corneal fluorescein staining scores. Histological analysis revealed that NA4 preserved corneal epithelial thickness and restored conjunctival goblet cell density. Immunofluorescence analysis revealed that NA4 reversed inflammation-associated epithelial hyperproliferation and attenuated macrophage infiltration. Moreover, NA4 markedly suppressed the expression and tissue levels of IL-1β, IL-6, and TNF-α, and attenuated corneal epithelial apoptosis, with the 500 mg/L NA4 group showing no significant difference in efficacy compared to the positive control 0.1% sodium hyaluronate. These findings demonstrate that NA4, a marine-derived oligosaccharide, exerts multi-targeted protective effects against DED by improving tear film stability, preserving ocular surface integrity, suppressing inflammation, and reducing apoptosis. Our study highlights the potential of marine oligosaccharides such as NA4 as promising candidates for ocular surface disease management and supports the further exploration of marine resources for ophthalmic therapeutic applications.
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