Tissue-resident macrophages play essential functions in the maintenance of tissue homeostasis and repair. Recently, the endocardium has been reported as a de novo hemogenic site for the contribution of hematopoietic cells, including cardiac macrophages, during embryogenesis. These observations challenge the current consensus that hematopoiesis originates from the hemogenic endothelium within the yolk sac and dorsal aorta. Whether the developing endocardium has such a hemogenic potential requires further investigation. Here, we generated new genetic tools to trace endocardial cells and reassessed their potential contribution to hematopoietic cells in the developing heart. Fate-mapping analyses revealed that the endocardium contributed minimally to cardiac macrophages and circulating blood cells. Instead, cardiac macrophages were mainly derived from the endothelium during primitive/transient definitive (yolk sac) and definitive (dorsal aorta) hematopoiesis. Our findings refute the concept of endocardial hematopoiesis, suggesting that the developing endocardium gives rise minimally to hematopoietic cells, including cardiac macrophages.

中文翻译：

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谱系追踪阐明了发育中心脏中组织驻留巨噬细胞的细胞起源

组织驻留巨噬细胞在维持组织稳态和修复中发挥重要作用。最近，据报道，心内膜是胚胎发生过程中造血细胞（包括心脏巨噬细胞）贡献的从头造血部位。这些观察结果挑战了目前的共识，即造血起源于卵黄囊和背主动脉内的造血内皮。发育中的心内膜是否具有这样的造血潜力还需要进一步研究。在这里，我们开发了新的遗传工具来追踪心内膜细胞，并重新评估了它们对发育中的心脏中造血细胞的潜在贡献。命运图谱分析显示，心内膜对心脏巨噬细胞和循环血细胞的贡献微乎其微。相反，心脏巨噬细胞主要源自原始/瞬时定形（卵黄囊）和定形（背主动脉）造血过程中的内皮细胞。我们的研究结果反驳了心内膜造血的概念，表明发育中的心内膜最低限度地产生造血细胞，包括心脏巨噬细胞。