Prior Exposure to Immunosuppressors Sensitizes Retinal Microglia and Accelerates Optic Nerve Regeneration in Zebrafish

Figure 4

Local treatment with clodronate liposomes efficiently depletes microglia/macrophages in the retina. Retinal microglia/macrophages are assessed in naive fish and after a single intravitreal injection of either saline or clodronate liposomes (3 dpIVT). Different focal planes are used to show microglia on retinal flat mounts in the innermost retina (GCL/NFL) and in the INL, respectively. (a-d) A single intravitreal injection of saline does not affect the retinal microglial morphology or number, as compared to naive uninjected fish. (e-g) At 3 days after intravitreal injection of clodronate liposomes, retinal microglia migrate towards the vitreous, leaving the retina almost completely depleted, as can be seen on retinal flat mounts (e-f), and is even more obvious in a retinal cross-section (g). Scale bars: 50 μm (a-f); 20 μm (g). GCL: ganglion cell layer; INL: inner nuclear layer; IPL: inner plexiform layer; NFL: nerve fiber layer; ONL: outer nuclear layer; OPL: outer plexiform layer; PRL: photoreceptor layer.