Supplementary Material for: Myeloid SOCS3 Deficiency Regulates Angiogenesis via Enhanced Apoptotic Endothelial Cell Engulfment

Mononuclear phagocytes, such as macrophages and microglia, are key regulators of organ homeostasis including vascularization processes. Here, we investigated the role of the suppressor of cytokine signaling 3 (SOCS3) in myeloid cells as a regulator of mononuclear phagocyte function and their interaction with endothelial cells in the context of sprouting angiogenesis. As compared to SOCS3-sufficient counterparts, SOCS3-deficient microglia and macrophages displayed an increased phagocytic activity toward primary apoptotic endothelial cells, which was associated with an enhanced expression of the opsonin growth arrest-specific 6 (Gas6), a major prophagocytic molecule. Furthermore, we found that myeloid SOCS3 deficiency significantly reduced angiogenesis in an ex vivo mouse aortic ring assay, which could be reversed by the inhibition of the Gas6 receptor Mer. Together, SOCS3 in myeloid cells regulates the Gas6/Mer-dependent phagocytosis of endothelial cells, and thereby angiogenesis-related processes. Our findings provide novel insights into the complex crosstalk between mononuclear phagocytes and endothelial cells, and may therefore provide a new platform for the development of new antiangiogenic therapies.

单核吞噬细胞（mononuclear phagocytes），如巨噬细胞（macrophages）与小胶质细胞（microglia），是调控包括血管形成过程在内的器官稳态的关键因子。本研究探讨了髓系细胞中细胞因子信号抑制因子3（SOCS3）作为单核吞噬细胞功能调控因子的作用，及其在出芽血管生成（sprouting angiogenesis）背景下与内皮细胞的相互作用。与SOCS3充足的对照细胞相比，SOCS3缺陷型小胶质细胞和巨噬细胞对原代凋亡内皮细胞的吞噬活性显著增强，该现象与促吞噬核心分子——调理素生长停滞特异性蛋白6（Gas6）的表达上调密切相关。此外，本研究发现髓系SOCS3缺陷可显著降低体外小鼠主动脉环实验中的血管生成水平，且该效应可通过抑制Gas6受体Mer得以逆转。综上，髓系细胞内的SOCS3通过调控Gas6/Mer通路依赖性的内皮细胞吞噬作用，进而影响血管生成相关进程。本研究结果为阐明单核吞噬细胞与内皮细胞间的复杂细胞串扰提供了全新视角，或可为新型抗血管生成治疗的研发提供可靠研究平台。