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Tao Li, Bogale Aredo, Xiao Chen, Kaiyan Zhang, Rafael Ufret-Vincenty; Change in the Distribution and Phenotype of Subretinal Microglia in C57BL/6J and RD8 Mutant Mice with Aging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):81. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To study the natural history of subretinal microglia in RD8 mutant mice and compare it to the appearance of subretinal microglia in naïve C57BL/6J mice as they age.
Subretinal microglia in mice homozygous for the RD8+/+ recessive mutation on Crb1 were compared to mice heterozygous or wild type for this mutation. The mice were divided into two age groups: young/adult (1-9 months) and old (14-21 months). Retinal images were taken using a Micron III rodent fundus camera (Phoenix Research Labs). The “central” or “posterior fundus” was defined as the posterior 5 disc diameters centered on the optic disc. Fundus white spots (on fundus photographs) and Iba-1+ cells (on flat mounts) were counted in the central fundus. Cells staining for CD16/CD32, mouse Macrophage Mannose Receptor (MMR), and/or Iba-1 were counted both in the central and total flat mounts. Morphological parameters of microglial activation were also measured.
There was a high correlation (r=0.863, p<0.0001, n=39 eyes) between the number of fundus white spots and the number of Iba-1+ microglia in the posterior fundus. Both, the fundus spots and the number of Iba-1+ cells increased significantly with age in RD8+/+ mice, but not wild type mice. The fraction of CD16+ cells localizing to the posterior fundus was higher in RD8+/+ mice relative to WT. Also, there was a significant increase in the ratio of CD16+ cells in old vs. young RD8+/+, compared to the ratio in old vs. young WT mice. Meanwhile, there was no difference in the ratio of MMR+ cells in old vs. young RD8+/+ compared to WT mice. A microglial morphology activation value (MMAV) parameter was defined as the area of the microglial cell body divided by the product of the number of extensions by the average extension length. The CD16+ cells were morphologically different from CD16- cells with a significantly increased MMAV. Furthermore, the CD16+ cells from old RD8+/+ mice had increased MMAV compared to young RD8+/+ and old WT mice.
The RD8+/+ mutation accelerates subretinal microglial accumulation. Furthermore, this mutation is associated with an increase in CD16+ cells, which show morphological evidence of activation.
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