title: Fate mapping reveals that microglia and recruited monocyte-derived macrophages are definitively distinguishable by phenotype in the retina.
abstract: The recent paradigm shift that microglia are yolk sac-derived, not hematopoietic-derived, is reshaping our knowledge about the isolated role of microglia in CNS diseases, including degenerative conditions of the retina. However, unraveling microglial-specific functions has been hindered by phenotypic overlap of microglia with monocyte-derived macrophages. The latter are differentiated from recruited monocytes in neuroinflammation, including retina. Here we demonstrate the use of fate mapping wherein microglia and monocyte-derived cells are endogenously labeled with different fluorescent reporters. Combining this method with 12-color flow cytometry, we show that these two populations are definitively distinguishable by phenotype in retina. We prove that retinal microglia have a unique CD45(lo) CD11c(lo) F4/80(lo) I-A/I-E(-) signature, conserved in the steady state and during retinal injury. The latter was observed in the widely used light-induced retinal degeneration model and corroborated in other models, including whole-body irradiation/bone-marrow transplantation. The literature contains conflicting observations about whether microglia, including in the retina, increase expression of these markers in neuroinflammation. We show that monocyte-derived macrophages have elevated expression of these surface markers, not microglia. Our resolution of such phenotypic differences may serve as a robust way to help characterize isolated roles of these cells in retinal neuroinflammation and possibly elsewhere in CNS.
authors: Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA.
authors: E G
authors: EG
authors: O'Koren
authors: Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA.
authors: R
authors: R
authors: Mathew
authors: Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA.|Department of Immunology, Duke University School of Medicine, Durham, NC, USA.
authors: D R
authors: DR
authors: Saban
mesh_terms: D000818:Animals; D058948:Cell Tracking / Q000379:methods*; D005434:Flow Cytometry / Q000379:methods*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D017628:Microglia / Q000166:cytology / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000378:metabolism