Fig. 5

The microglial scar is mainly composed of microglia, with few scattered blood-derived myeloid cells and CNS border-associated macrophages. a Schematic diagram showing the protocol used to generate radiation bone marrow chimeras in which microglia express TdT and bone marrow-derived cells the GFP reporter. b–e Representative confocal images showing the microglial scar formed of TdT⁺ microglia (red), some of which are in close apposition with GFAP-immunoreactive astrocyte endfeet (blue) on one side and bone marrow-derived cells (eGFP⁺, green) on the other side at 14 days post-SCI. f Schematic of experimental procedure and timeline to generate bone marrow chimeras in which Cx3cr1^creER::R26-TdT mice were used as bone marrow donors for irradiated recipient C57BL/6 mice. g and h Representative confocal images showing the virtual absence of bone marrow-derived TdT⁺ cells (red) medial to the astrocytic scar (as defined by GFAP⁺ astrocyte endfeet in blue), where the microglial scar normally develops, at 14 days post-SCI in Cx3cr1^creER::R26-TdT → WT chimeric mice. i–o Confocal images showing the absence (or very weak expression) of CD206 (green) in microglia (TdT⁺, red) forming the microglial scar at the lesion borders at 14 days post-SCI. In contrast, border-associated macrophages express high levels of the CD206 protein. p Representative confocal image showing the absence of colocalization between TdT (red) and MHCII (cyan) in the injured spinal cord of a Cx3cr1^creER::R26-TdT mouse at 14 days. Scale bars: (b–e, in e) 20 µm, (g and h, in h) 200 µm, (i, p) 200 µm, (j–o, in o) 10 µm