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Akira Haga, Eri Takahashi, Yasuya Inomata, Hidenobu Tanihara; The subtypes of retinal microglia in rat after optic nerve crush injury. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4946.
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To investigate the localization of type1 and type 2 microglia (MG) in a rat model of optic nerve crush injury.
Optic nerve crush (ONC) was unilaterally performed on adult male Sprague Dawley rats, and the eyes with injured optic nerve were enucleated 7, 14, 21, or 28 days after ONC (N=4 per group). The fellow eyes without ONC were used as control. Paraffin-embedded sections of rat eyes were subjected to immunostaining and photographed by a fluorescence microscopy. Antibody against ionized calcium binding adaptor molecule 1 (Iba-1) was used to identify the mixed type 1 and type2 MG (pan-MGs), and anti-CD68 antibody for active form of MG, anti-9F5 antibody for type 1 MG and anti-neuron-specific class Ⅲ b-tubulin (Tuj-1) antibody for retinal ganglion cell (RGC) were also used. Statistical significance was determined by Student’s t-test. Multiple comparisons were adjusted by Bonferroni’s method.
Immunohisotochemical analysis showed that 9F5-positive (9F5+) and Iba1-positive (Iba1+) type 1 MGs were detected in optic nerve (ON) at day 14 (124.5 ± 7.79 cells/mm2 p<0.0001 vs. control), but not found at day 7, 21 and 28. Type 1 MGs were detected at neither RGC layer nor ONH. On other hand, Iba1+ 9F5- type2 MGs localized at RGC layer (57.5 ± 4.68 cells/ mm), optic nerve head (ONH) (112.5 ± 54.49 cells/ mm2) and ON (105 ± 9.0 cells/ mm2) in control. Type 2 MGs increased at day 7, 14 and 21 in RGC layer (p<0.01 vs. control) and at all time points in ONH (p<0.01 vs. control) and ON (p<0.01 vs. control). CD68-positive (CD68+) and Iba1+ active MGs were found at day14 and 21 in RGC layer (p<0.01 vs. control) and at all time points investigated in ON area. Active form of MGs was not detected in ONH after ONC.
Our findings suggest that two microglia subtypes has different roles in RGC survival and optic nerve gliosis at the cruch sites.
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