Fig. 3. CCR2-dependent monocyte recruitment contributes to left atrial macrophage expansion and atrial disease.

(A) Flow cytometric quantification of recruited (YFP⁺ Td⁻) and locally sourced (YFP⁺ Td⁺) left atrial macrophages in Cx3cr1^CreER/+ Ai9^fl/+ sham and HOMER mice. n = 8 to 12 per group from two independent experiments, two-tailed Student’s t test. Td, tdTomato; YFP, yellow fluorescent protein. (B) Relative Spp1 expression levels by qPCR in recruited (YFP⁺ Td⁻) and locally sourced (YFP⁺ Td⁺) left atrial macrophages in Cx3cr1^CreER/+ Ai9^fl/+ HOMER mice. n = 8 per group from two independent experiments, two-tailed Wilcoxon matched-pairs signed rank test. (C) Flow cytometric quantification of myeloid cell populations in left atrial tissues from C57BL/6 and Ccr2^−/− HOMER mice. Macrophages: 21 C57BL/6 and 19 Ccr2^−/− HOMER mice from five independent experiments; monocytes and neutrophils: 12 C57BL/6 and 10 Ccr2^−/− HOMER mice from three independent experiments; two-tailed Student’s t test. (D) Flow cytometric quantification of TREM2⁺ CD9⁺ left atrial macrophages in C57BL/6 and Ccr2^−/− HOMER mice. n = 7 to 9 per group from two independent experiments, two-tailed Student’s t test. (E) AFib inducibility and burden in C57BL/6 and Ccr2^−/− HOMER mice by means of electrophysiological (EP) study. n = 8 to 9 per group from two independent experiments. (Left) Two-sided Fisher’s exact test. (Right) Two-tailed Mann–Whitney test. Other EP parameters are shown in table S8. All bar graph data are mean ± SEM with individual values for data distribution.