Exercise reduces <i>C1qa</i><sup>+</sup> microglia/monocytes in the aged cortex.

<p>(A) Representative sections from an aged sedentary and aged runner mouse immunostained with PDGFRβ (magenta) for pericytes and IBA1 (green) for microglia/monocyte cells. (B) Quantification of IBA1<sup>+</sup> cells in aging, aged sedentary (Sd), and aged runner (Rn) mice shows a decrease in microglia/monocyte density in the aged runners versus the aged sedentary mice. (C) Correlation between PDGFRβ<sup>+</sup> cells and IBA1<sup>+</sup> cells (R<sup>2</sup> = 0.49, <i>p</i> = 0.01). Decreased number of pericytes correlates with increasing number of microglia/monocyte cells. (D) Representative sections of the cortex hybridized with <i>C1qa</i> riboprobe and coimmunostained with IBA1 (green) in young, aged Sd and aged Rn mice. (E) Quantification of <i>C1qa</i>/IBA1<sup>+</sup> (magenta bars) and IBA1<sup>+</sup> (green bars) cells in the cortex of young, aged Sd, and aged Rn mice showing a significant increase in <i>C1qa</i><sup>+</sup>/IBA1 positive cells in aged Sd mice and a significant decline of these cells in the aged runner mice. A new quantification of IBA1<sup>+</sup> cells (different from B) was performed for the analysis of <i>C1qa</i><sup>+</sup>/IBA1 cells. (F) Representative sections of the hippocampal CA1 hybridized with <i>C1qa</i> riboprobe and coimmunostained with IBA1 (green) in young, aged Sd, and aged Rn mice. (G) <i>C1q</i>/IBA1<sup>+</sup> (magenta bars) and IBA1<sup>+</sup> (green bars) cells in the hippocampal CA1 are significantly increased in aged Sd mice and significantly reduced in aged Rn mice. In panels (B, E, and G) values are mean <u>+</u> SEM, <i>n =</i> 4 per group. In (B) **<i>p</i> = 0.0032 and *<i>p</i> = 0.0148, in (E) **<i>p =</i> 0.0065 and 0.0044, ***<i>p =</i> 0.0006 and *<i>p</i> = 0.0194 and in (G) ***<i>p <</i> 0.0006,***<i>p</i> = 0.0003, **<i>p =</i> 0.0025 and *<i>p</i> = 0.0302 by ANOVA followed by Tukey’s posthoc tests. Scale Bars: 50 μm. The data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002279#pbio.1002279.s001" target="_blank">S1 Dataset</a>.</p>