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Samantha Dando, Paul G McMenamin; Myeloid cell dynamics in the mouse uveal tract during systemic inflammation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):984.
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© ARVO (1962-2015); The Authors (2016-present)
The uveal tract contains dense populations of myeloid cells, which may function as an immune barrier to protect the closely-associated neural retina. However, very little is known about the nature of immune responses within the uvea. The purpose of this study was to characterise the effects of systemic inflammation on myeloid cell populations within the mouse uveal tract and retina.
BALB/c Cx3cr1gfp/gfp mice received an i.p. injection of either lipopolysaccharide (LPS, 9 mg/kg, n=20) or saline (n=16). Eyes were collected 24h later and single cell suspensions were prepared from pooled iris-ciliary body, choroid and retina. Flow cytometry was used to characterise the expression of surface markers on uveal tract and retinal myeloid cell populations. In a second study, eyes were collected from BALB/c Cx3cr1gfp/gfp mice at 2, 24 or 48h post-LPS injection (n= 3-5 per timepoint). Tissues were stained with I-A/I-E antibodies, flatmounted and examined by confocal microscopy. Cell densities were quantified using FIJI.
Cx3cr1-GFP+ myeloid cells within the iris-ciliary body of control mice displayed the phenotype of macrophages (F4/80+CD11b+CD86+); 56% of these cells also expressed I-A/I-E. Within the normal choroid, two Cx3cr1-GFP+ populations were observed: F4/80+CD11b+CD86+I-A/I-E+ and F4/80-CD11b-CD11c+I-A/I-E+, potentially resembling distinct populations of macrophages and dendritic cells. Twenty-four hours after LPS injection, the expression of I-A/I-E and CD86 was markedly decreased on myeloid cell populations within the iris-ciliary body and choroid, whereas CD80 expression was increased, suggesting that these cells were in a late-activated state. In contrast, the surface phenotype of retinal microglia was not altered by systemic LPS exposure. By 48h, there was a dramatic decrease in the density of Cx3cr1-GFP+ I-A/I-E+ cells within the uveal tract compared to controls (p<0.05) but a significant increase in the density of round Cx3cr1-GFP+ I-A/I-E- cells (p<0.05).
Systemic LPS exposure altered the expression of activation markers on uveal tract myeloid cell populations, but not retinal microglia, at 24h. By 48h post-LPS injection, the landscape of myeloid cells within the iris, ciliary body and choroid had undergone extensive remodelling, suggesting that phenotypic switching, cell migration and/or recruitment readily occurs within the uveal tract.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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