CX3CR1 Deficient Macrophages Present An Impaired Clearance From The Subretinal Space

Abstract

Purpose: : We have previously shown that Cx3cr1-/- mice present a subretinal macrophage/microglial cell accumulation with age and light-injury. The mechanism that leads to this accumulation is unknown. We here studied the clearance of subretinally injected wild type and Cx3cr1-/- macrophages.

Methods: : Peritoneal macrophages (PM) were prepared from thioglycolate injected wild type and Cx3cr1-/- mice. Cx3cr1 expression was analyzed by RT-PCR. Cells were stained with CFSE and 20 000 cells were injected in the subretinal space of wild type mice. At 12h and 24h, subretinal PMs were TUNEL stained and positive cells were quantified on retinal and RPE flatmounts from wild type PMs and Cx3cr1-/- PMs injected mice.

Results: : Wild type PMs express Cx3cr1. Subretinally injected PMs undergo apoptosis mainly at 12h and are quickly cleared from the subretinal space. At 24h the number of subsisting subretinal Cx3cr1-/- PMs is significantly (4 fold) increased as compared to wild type PMs.

Conclusions: : Wild type PMs are quickly eliminated from the subretinal space. The clearance of subretinal Cx3cr1-/- PMs is significantly impaired. The relative resistance of Cx3cr1-/- PMs to elimination from the subretinal space might explain the accumulation of subretinal macrophages/microglial cells with age and light-injury.

Keywords: age-related macular degeneration • pathology techniques