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. 2021 Jul 12;10:e61173. doi: 10.7554/eLife.61173

Figure 1. In vivo imaging of microglia shows limited migration and turnover in the physiological brain.

(A) A field of microglia in an awake mouse imaged over 14 consecutive days. The dark diagonal lines in the center and top right of the image are blood vessels that remain structurally stable and can be used as landmarks to identify the same location for chronic imaging. Several microglia are identified with the same-colored circles at different time points to show the stability of their somas. (B) Nearest neighbor quantification in 3D demonstrates the distribution of neighboring microglial cells over consecutive days. (C) The translocation index, which captured the average displacement of microglia over time, was ~15 µm when consecutive imaging sessions were compared. (D) The translocation index increased when D1 is compared to imaging carried out later (D2–D14). (E) Microglia translocation between D1-D2, D1-D4, D1-D7, D1-D10, D1-D12, and D1-D14. On average, the majority of microglia remained within ~10 µm away (white bars, circles) from their original location. The number of microglia that moved within their domain (10–30 µm; orange bars, squares), (20–30 µm; blue bars, triangles) or translocated a further distance (>30 µm; gray bars, filled circles) stayed relatively constant with increasing interval between imaging sessions (n=3, 30–40 µm stacks, 13–17 microglia per mouse). Scale bar, 50 μm. Figure 1—source data 1: Source data for microglia turnover and migration in the physiological brain.

Figure 1—source data 1. Source data for microglia turnover and migration in the physiological brain.
Figure 1—source data 2. Source data for CSF1R inhibition in the adult brain.
Figure 1—source data 3. Source data for the Cytokine panel conducted.

Figure 1.

Figure 1—figure supplement 1. CSF1R inhibitor consistently eliminates microglia from the adult brain.

Figure 1—figure supplement 1.

(A–C) Representative maximum intensity projections of confocal images of microglia from the primary visual cortex (V1) in fixed sections of control (A), 7 days PLX (B), and 7 days repopulated (C) mice. (D) Microglial numbers significantly decreased with PLX. n=3–4 animals, average of 3–4 slices per animal. T-test, **p<0.01. Graphs show mean ± s.e.m. Points represent individual animals. Scale bar, 50 µm. Figure 1—source data 2: Source data for CSF1R inhibition in the adult brain.
Figure 1—figure supplement 2. No change in inflammatory milieu following microglial depletion.

Figure 1—figure supplement 2.

(A–L) A combination of anti-inflammatory and pro-inflammatory cytokines including IL-1b, IL-4, IL-6, IL-10, and TFNα were tested using a Multiplex Assay. Each experiment was assayed in triplicate. n=seven animals. T-test, ns. Graphs show means ± s.e.m. Points represent individual animals. Figure 1—source data 3: Source data for the Cytokine panel conducted.