Retinal microglia and uveal tract dendritic cells and macrophages are not CX3CR1 dependent in their recruitment and distribution in the young mouse eye.

PURPOSE: The chemokine receptor CX3CR1 is expressed by monocyte-derived dendritic cells (DCs) and macrophages. CX3CR1 mediates leukocyte migration and adhesion in homeostatic and inflammatory conditions. Mice lacking Cx3cr1 have altered distribution and function of DC subpopulations in some tissue microenvironments. The present study compares the distribution of monocyte-derived cells in the normal retina and uveal tract as a prelude to the investigation of the role of CX3CR1 in murine models of ocular disease.
METHODS: Transgenic mice in which either one (Cx3cr1 gfp/+, heterozygous) or both (Cx3cr1 gfp/gfp, homozygous) copies of the Cx3cr1 gene have been replaced by the enhanced green fluorescent protein (eGFP) reporter gene were used to investigate the role of Cx3cr1 expression on macrophages and DCs in the normal uveal tract and retina. Chimeric mice were used to investigate turnover of these cells in the normal, uninflamed eye.
RESULTS: Confocal analysis found no significant differences in the density, phenotype or morphology of eGFP+ cells between Cx3cr1 gfp/+ and Cx3cr1 gfp/+ mice in immunostained iris, ciliary body, or choroidal and retinal wholemounts. Flow cytometry also failed to detect any difference in the density or cell shape of eGFP+ cells between Cx3cr1 gfp/+ and Cx3cr1 gfp/+ mice. Chimeras revealed 73% turnover of monocyte-derived cells in the iris and 63% in the choroid by 6 weeks after transplantation.
CONCLUSIONS: These data illustrate that homing or migration of DCs and macrophages to the uveal tract and retina in normal young mice is not Cx3cr1 dependent and provide a solid foundation for future studies of monocyte-derived cells and the role of Cx3cr1 in models of ocular disease.