In vivo neuronal visualization for ocular disease models through a novel NIR-II neurotracer

Early detection of glaucomatous neurodegeneration represents a crucial approach in the fight against blindness caused by glaucoma. In clinical practice, it demands for real-time in vivo analysis of the retinal ganglion cells (RGCs) as well as their central projections under pathological conditions. However, current methodology remains challenging due to limitations in deep-tissue penetration and spatiotemporal resolution of conventional neural tracers. Here, through covalent conjunction of FDA-approved indocyanine green (ICG) and cholera toxin subunit B (CTB), a novel fluorescent neurotracing probe (ICG-CTB) in the second near-infrared region (NIR-II) was developed for anterograde labeling of RGCs via intravitreal injection. With merits of novel neuro-tracing property, high biosafety profile and functional efficacy, ICG-CTB achieved effective labeling and real-time NIR-II bioimaging of the soma and axons of RGCs with signal persistence over 1 week. With this, dynamic axonal degeneration was successfully examined in both acute ocular hypertension (AOH), optic nerve crush (ONC) and visual pathway compression (VPC) models. This proposed novel ICG-CTB probe could facilitate high-fidelity in vivo mapping of pathological axonal alterations across glaucomatous and neoplastic contexts, providing a critical tool for evaluating therapeutic interventions targeting optic neuropathies.