RNA-seq expression profiling of cardiac macrophages and splenic monocytes from naïve and CAWS challenged mice

The adult heart contains macrophages derived from both embryonic and adult bone-marrow derived precursors. Such population diversity raises the possibility that macrophages of distinct origins occupy differing biological roles or anatomical niches within the heart. Here, we provide evidence for the latter, showing that bone-marrow derived macrophages express the chemokine receptor Ccr2 and preferentially localise to the aortic root of the heart. This targeted migration occurs via a Ccr2-Ccl7 axis, whereby Ccl7-producing cardiac fibroblasts populating the aortic root, recruit Ccr2pos macrophages. Notably, the selective recruitment of Ccr2pos macrophages renders the aortic root sensitive to inflammatory disease. In a mouse model of Kawasaki Disease, acute inflammation drives a numerical increase in bone-marrow derived Ccr2pos macrophages, which accumulate at the aorta and trigger local inflammation at this site. We propose that cardiac fibroblasts recruit Ccr2pos macrophages to the aortic root, and that this process targets inflammatory disease to the heart’s major vessels. Mice were either naïve or challenged with a Candida albicans water-soluble complex (CAWS) to induce a mouse model of Kawasaki Disease. Cardiac macrophages were extracted from three independent pools of naive mice and three independent pools of CAWS challenged mice. Splenic monocytes were extracted from three independent pools of naive mice. In each case, cardiac macrophages were divided into three subpopulations (R1, R2 and R3) based on Ccr2 and MHC-II expression.

成年心脏中存在源自胚胎及成年骨髓前体的巨噬细胞。这类巨噬细胞的群体异质性提示，不同起源的巨噬细胞在心脏内可能具备不同的生物学功能或解剖微环境。本研究为这一假说提供了实证：骨髓来源的巨噬细胞可表达趋化因子受体Ccr2，并优先定位于心脏主动脉根部。该靶向迁移依赖于Ccr2-Ccl7轴：定位于主动脉根部的心脏成纤维细胞可分泌Ccl7，借此招募Ccr2阳性巨噬细胞。值得注意的是，这种对Ccr2阳性巨噬细胞的选择性招募，使得主动脉根部更易受到炎症性疾病的侵袭。在川崎病（Kawasaki Disease）小鼠模型中，急性炎症会促使骨髓来源的Ccr2阳性巨噬细胞数量显著增加，这些细胞在主动脉处聚集并触发该部位的局部炎症。我们推测，心脏成纤维细胞将Ccr2阳性巨噬细胞招募至主动脉根部，这一过程将炎症性疾病的发生靶向限定于心脏的主要血管。实验小鼠分为未致敏小鼠（naive mice）组与经白色念珠菌水溶性复合物（Candida albicans water-soluble complex, CAWS）造模组，后者用于构建川崎病小鼠模型。分别从3批独立的未致敏小鼠及3批独立的CAWS造模小鼠中分离心脏巨噬细胞；同时从3批独立的未致敏小鼠中分离脾脏单核细胞。所有心脏巨噬细胞样本均根据Ccr2与主要组织相容性复合体II类（Major Histocompatibility Complex II, MHC-II）的表达水平，被划分为R1、R2、R3三个亚群。