Exercise reduces C1qa⁺ microglia/monocytes in the aged cortex.

(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⁺ 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⁺ cells and IBA1⁺ cells (R² = 0.49, p = 0.01). Decreased number of pericytes correlates with increasing number of microglia/monocyte cells. (D) Representative sections of the cortex hybridized with C1qa riboprobe and coimmunostained with IBA1 (green) in young, aged Sd and aged Rn mice. (E) Quantification of C1qa/IBA1⁺ (magenta bars) and IBA1⁺ (green bars) cells in the cortex of young, aged Sd, and aged Rn mice showing a significant increase in C1qa⁺/IBA1 positive cells in aged Sd mice and a significant decline of these cells in the aged runner mice. A new quantification of IBA1⁺ cells (different from B) was performed for the analysis of C1qa⁺/IBA1 cells. (F) Representative sections of the hippocampal CA1 hybridized with C1qa riboprobe and coimmunostained with IBA1 (green) in young, aged Sd, and aged Rn mice. (G) C1q/IBA1⁺ (magenta bars) and IBA1⁺ (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 + SEM, n = 4 per group. In (B) **p = 0.0032 and *p = 0.0148, in (E) **p = 0.0065 and 0.0044, ***p = 0.0006 and *p = 0.0194 and in (G) ***p < 0.0006,***p = 0.0003, **p = 0.0025 and *p = 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 S1 Dataset.