Microglial ramification and redistribution concomitant with the attenuation of choroidal neovascularization by neuroprotectin D1

PURPOSE: Neuroprotectin D1 (NPD1) attenuates laser-induced choroidal neovascularization (CNV) when administered intraperitoneally. Due to its lipophilicity and low molecular weight, NPD1 is well suited for topical delivery; thus, we investigated the efficacy of topically applied NPD1 in attenuating CNV. We also examined the effect of NPD1 on the recruitment and activation of microglia surrounding CNV lesions. METHODS: Mice were given laser-induced CNV and treated with NPD1 eye drops. CNV was evaluated by fluorescein leakage using a novel image analysis method and by isolectin B4 immunofluorescence of neovasculature. Microglia; recruitment was assessed by quantification. Using form factor, solidity, convexity, and fractal dimension, microglial activation was quantitatively assessed by two-dimensional, and for the first time, three-dimensional morphology. An ImageJ plugin, 3D Shape, was developed to enable this analysis. RESULTS: NPD1 attenuated leakage and neovascularization. The proximity of microglia to CNV lesions was significantly closer with NPD1. Consistent with the cellular ramification, microglia in NPD1-treated eyes were larger and exhibited a lower form factor and higher fractal dimension. CONCLUSIONS: Our data show that NPD1 signaling induces a ramified, non-injury-inducing microglial phenotype coincident with attenuation of CNV. Since microglia are crucial participants in neurodegenerative diseases, the discovery that microglia are potential targets of NPD1 signaling warrants further investigation.