Figure 7

Unaltered dynamics of microglial processes in LPS-treated mice. (A) Morphology of microglia imaged by in vivo two-photon microscopy of Iba1-GFP mice. A1 shows a cell from a mouse without LPS administration. A2 and A3 show cells from LPS-treated mice at two and 28 days after LPS treatment, respectively. Scale bar, 10 μm. (B1) An example of a microglial cell utilized for time-lapse analysis (identical cell shown in A3). This image shows the morphology at zero time point, with an overlay of green lines (numbered from 1 to 10) on individual processes. The tips of these green lines were recorded and their distances between adjacent time frames (3 min intervals) were calculated as an index of process motility shown in C and D. (B2) Binary images of a microglial process (green line) extracted from time-lapse sequences in the image area marked by a dotted rectangle in B1, illustrating the extent (yellow line) of rapid growth and shrinkage (red line). Numbers in the upper left corner indicate elapsed time in min. Scale bar, 2 μm. (C) The motility of microglial processes. Extension and retraction of processes were plotted for three representative processes with time intervals of three min. Positive values indicate process extension and negative values indicate retraction. (D) Summation of absolute distances of extension and retraction during 30 minutes was calculated and the average speeds per frame (three min) were estimated from 10 processes of control and LPS-treated mice. The average motility was comparable among control and LPS-treated groups.