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, 68 (3), 574-588

Inhibition of Inflammatory Cells Delays Retinal Degeneration in Experimental Retinal Vein Occlusion in Mice

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Inhibition of Inflammatory Cells Delays Retinal Degeneration in Experimental Retinal Vein Occlusion in Mice

Joël Jovanovic et al. Glia.

Abstract

The role of microglia in retinal inflammation is still ambiguous. Branch retinal vein occlusion initiates an inflammatory response whereby resident microglia cells are activated. They trigger infiltration of neutrophils that exacerbate blood-retina barrier damage, regulate postischemic inflammation and irreversible loss of neuroretina. Suppression of microglia-mediated inflammation might bear potential for mitigating functional impairment after retinal vein occlusion (RVO). To test this hypothesis, we depleted microglia by PLX5622 (a selective tyrosine kinase inhibitor that targets the colony-stimulating factor-1 receptor) in fractalkine receptor reporter mice (Cx3cr1gfp/+ ) subjected to various regimens of PLX5622 treatment and experimental RVO. Effectiveness of microglia suppression and retinal outcomes including retinal thickness as well as ganglion cell survival were compared to a control group of mice with experimental vein occlusion only. PLX5622 caused dramatic suppression of microglia. Despite vein occlusion, reappearance of green fluorescent protein positive cells was strongly impeded with continuous PLX5622 treatment and significantly delayed after its cessation. In depleted mice, retinal proinflammatory cytokine signaling was diminished and retinal ganglion cell survival improved by almost 50% compared to nondepleted animals 3 weeks after vein occlusion. Optical coherence tomography suggested delayed retinal degeneration in depleted mice. In summary, findings indicate that suppression of cells bearing the colony-stimulating factor-1 receptor, mainly microglia and monocytes, mitigates ischemic damage and salvages retinal ganglion cells. Blood-retina barrier breakdown seems central in the disease mechanism, and complex interactions between different cell types composing the blood-retina barrier as well as sustained hypoxia might explain why the protective effect was only partial.

Keywords: blood-retina barrier; inflammation; ischemia; microglia; receptor tyrosine kinase inhibitor; retinal ganglion cell; retinal vein occlusion.

Figures

Figure 1
Figure 1
Monitoring of retinal microglia depletion by in vivo confocal scanning laser ophthalmoscopy. (a) There is quick and sustained suppression of microglia with PLX5622 treatment. (b) Representative images of microglia depletion kinetics. Pictures were taken in blue‐light autofluorescence mode using a 102° ultra‐widefield optic at baseline, 7d, 14d, and 21d, ****p < .0001 (Dunnett's multiple comparison test)
Figure 2
Figure 2
Schematic representation of treatment regimen in the three experimental groups and representative in vivo fundus images at baseline and 3 weeks after induction of eBRVO. (a) Animals in the first group were continuously fed with PLX5622 diet (BRVO + PLX5622). Infiltration of GFP+ cells around the optic nerve and targeted blood vessels. (b) In the second group, chow was switched to control diet after induction of retinal vein occlusion (BRVO + Microglia Recovery). In addition to changes visible in the first group, dense repopulation of the retina is noted after 3 weeks. (c) In the third group, eBRVO was induced and mice were continuously kept on control diet (BRVO). Pathologic changes and density of GFP+ cells are similar to those in the second group [Color figure can be viewed at http://wileyonlinelibrary.com]
Figure 3
Figure 3
Retinal thickness changes in (a) occluded and (b) nonoccluded retinal areas after experimental retinal vein occlusion. Thinning is partially prevented in animals with continuous depletion. Two‐way ANOVA confirms that PLX5622 treatment has a significant effect in ischemic retina (p = .0007)
Figure 4
Figure 4
Retinal ganglion cells are partially salvaged in PLX5622 treated mice. Two‐way ANOVA confirms that treatment affords significant protection in the ischemic retina
Figure 5
Figure 5
Representative examples of retinal whole mounted retinas stained for retinal ganglion cells (Brn3a) in (a) continuously depleted mice (BRVO + PLX5622) and (b) control mice (BRVO) at baseline, 7d, 14d, and 21d after eBRVO induction. Scale bars, 500 μm [Color figure can be viewed at http://wileyonlinelibrary.com]
Figure 6
Figure 6
Semiquantitative grading of microglia repopulation in (a) occluded and (b) nonoccluded retina. (c) Analysis for all animals with cessation of treatment at time of laser (BRVO + Microglia Recovery) and (d) control mice. Templates used for grading are shown in (e). P‐Values are shown for two‐way ANOVA with factors “treatment” and “time.” *p < .05, **p < .01, p < .001, ****p < .0001 [Color figure can be viewed at http://wileyonlinelibrary.com]
Figure 7
Figure 7
Results from mouse cytokine antibody microarray for a selection of (a) proinflammatory and (b) anti‐inflammatory proteins. Significance levels: *p < .05, **p < .01, ***p < .001, ****p < .0001; ♦: expression level below detection threshold (0.1 pg/ml)

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References

    1. Acharya M. M., Green K. N., Allen B. D., Najafi A. R., Syage A., Minasyan H., … Limoli C. L. (2016). Elimination of microglia improves cognitive function following cranial irradiation. Scientific Reports, 6, 31545 10.1038/srep31545 - DOI - PMC - PubMed
    1. Anderson C. F., & Mosser D. M. (2002). A novel phenotype for an activated macrophage: The type 2 activated macrophage. Journal of Leukocyte Biology, 72(1), 101–106. - PubMed
    1. Berti R., Williams A. J., Moffett J. R., Hale S. L., Velarde L. C., Elliott P. J., … Tortella F. C. (2002). Quantitative real‐time RT‐PCR analysis of inflammatory gene expression associated with ischemia‐reperfusion brain injury. Journal of Cerebral Blood Flow and Metabolism, 22(9), 1068–1079. 10.1097/00004647-200209000-00004 - DOI - PubMed
    1. Chan‐Ling T., & Stone J. (1991). Factors determining the migration of astrocytes into the developing retina: Migration does not depend on intact axons or patent vessels. The Journal of Comparative Neurology, 303(3), 375–386. 10.1002/cne.903030304 - DOI - PubMed
    1. Chen Y., Hallenbeck J. M., Ruetzler C., Bol D., Thomas K., Berman N. E., & Vogel S. N. (2003). Overexpression of monocyte chemoattractant protein 1 in the brain exacerbates ischemic brain injury and is associated with recruitment of inflammatory cells. Journal of Cerebral Blood Flow and Metabolism, 23(6), 748–755. 10.1097/01.WCB.0000071885.63724.20 - DOI - PubMed

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