Alternations in inflammatory macrophage niche drive phenotypic and functional plasticity of Kupffer cells
Han-Ying Huang, Yan-Zhou Chen, Chuang Zhao, Xin-Nan Zheng, Kai Yu, Jia‐Xing Yue, Huai‐Qiang Ju, Yanxia Shi, Lin Tian
Abstract
Inflammatory signals lead to recruitment of circulating monocytes and induce their differentiation into pro-inflammatory macrophages. Therefore, whether blocking inflammatory monocytes can mitigate disease progression is being actively evaluated. Here, we employ multiple lineage-tracing models and show that monocyte-derived macrophages (mo-mac) are the major population of immunosuppressive, liver metastasis-associated macrophages (LMAM), while the proportion of Kupffer cells (KC) as liver-resident macrophages is diminished in metastatic nodules. Paradoxically, genetic ablation of mo-macs results in only a marginal decrease in LMAMs. Using a proliferation-recording system and a KC-tracing model in a monocyte-deficient background, we find that LMAMs can be replenished either via increased local macrophage proliferation or by promoting KC infiltration. In the latter regard, KCs undergo transient proliferation and exhibit substantial phenotypic and functional alterations through epigenetic reprogramming following the vacating of macrophage niches by monocyte depletion. Our data thus suggest that a simultaneous blockade of monocyte recruitment and macrophage proliferation may effectively target immunosuppressive myelopoiesis and reprogram the microenvironment towards an immunostimulatory state. In liver metastasis of cancer, the inflammatory macrophage niche is dominated by both circulating monocytes and local expansion, but the nature and dynamic of this niche is still unclear. Here the authors use mouse genetic models and lineage-tracing tools to show that, under the condition of monocyte depletion, Kupffer cells pursue epigenetic reprogramming to contribute to this niche.