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Akito Shimouchi, Harumasa Yokota, Chiemi Matsumoto, Akira Takamiya, Taiji Nagaoka, Akitoshi Yoshida; Quantitative morphometry of microglia in retinal inflammation. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3493. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Microglial form and function have been thought to be inextricably linked in various retinal diseases. We have demonstrated that computer-assisted morphometry is useful for precisely evaluating changes in microglial form during retinal neovascularization (Shimouchi et al, ARVO 2014). In this study, we investigated whether microglial morphometry could assess the sequential changes in microglial form during retinal inflammation.
Uveitis model was induced by intraperitoneal injection of lipopolysaccharide (LPS) in C57BL/6J mice. Retinal sections were prepared using the eyes collected at 12, 24 and 36 hours after LPS treatment. Retinal vessels were labeled with lectin and microglia were labeled with Iba1. Confocal images of retinal microglia were processed with Image J to calculate form factor (FF, roundness), branching density (BD), convexity (CON), solidity (SOL, spatial density), and fractal dimension (DF, structural complexity).
FF (Mean±SD; 0.076±0.038), BD (0.021±0.006) and SOL (0.407±0.160) were significantly higher and DF (1.351±0.037) was significantly lower in the retina at 12 hours compared with control (FF=0.034±0.014, BD=0.011±0.003, SOL=0.180±0.066, DF=1.447±0.010, control: n=24, 12 hours: n=27, p<0.0001), which meant that microglia significantly changed their form to be amoeboid. Although morphometric values of microglia still showed that microglia were significantly amoeboid at 24 hours (n=30) after LPS injection, the degree was attenuated in comparison with the retina at 12 hours. In contrast, there was no significant difference in those morphometric values of microglia between the retinas at 36 hours (n=17) after LPS injection and control.
Computer-assisted morphometry succeeded in depicting the sequential changes in microglial form during retinal inflammation. According to morphometric analysis in the current study, microglia became activated and returned to normal state by 36 hours after LPS injection. Microglial morphometry is suggested to offer a new index of retinal inflammation that takes place in a number of retinal diseases.
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