Phenotypic and functional heterogeneity of macrophages is known to be the main reason for their ability to regulate inflammation and promote tumorigenesis. Mesenchymal stem cells (MSCs) are one of the principal cells commonly found in the tumor stromal niche, with capability of macrophage phenotypic switching. The objective of this study was to evaluate the role of C-X-C motif chemokine ligand 12 (CXCL12) produced by marrow-derived MSCs in the phenotypic and functional pattern of bone marrow-derived macrophages (BMDMs). First, the CRISPR/Cas9 system was used for the CXCL12 gene knock-out in MSCs. Then, coculture systems were used to investigate the role of MSCsCXCL12−/− and MSCsCXCL12+/+ in determination of macrophage phenotype. To further analyze the role of the MSC-derived CXCL12 niche, cocultures of 4T1 mammary tumor cells and macrophages primed with MSCsCXCL12−/− or MSCsCXCL12+/+ as well as in-vivo limiting dilution assays were performed. Our results revealed that the expression of IL-4, IL-10, TGF-β and CD206 as M2 markers was significantly increased in macrophages co-cultured with MSCsCXCL12+/+ , whereas the expression of IL-6, TNF-α and iNOS was conversely decreased. The number and size of multicellular tumor spheroids were remarkably higher when 4T1 cells were cocultured with MSCCXCL12+/+-induced M2 macrophages. We also found that the occurrence of tumors was significantly higher in coinjection of 4T1 cells with MSCCXCL12+/+-primed macrophages. Tumor initiating cells were significantly decreased after coinjection of 4T1 cells with macrophages pretreated with MSCsCXCL12−/−. In conclusion, our findings shed new light on the role of MSC-derived CXCL12 in macrophage phenotypic switching to M2, affecting their function in tumorigenesis.

中文翻译：

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MSC 衍生的 CXCL12 引起的巨噬细胞极化决定肿瘤生长


已知巨噬细胞的表型和功能异质性是其调节炎症和促进肿瘤发生能力的主要原因。间充质干细胞（MSC）是肿瘤基质微环境中常见的主要细胞之一，具有巨噬细胞表型转换的能力。本研究的目的是评估骨髓源性 MSC 产生的 CXC 基序趋化因子配体 12 (CXCL12) 在骨髓源性巨噬细胞 (BMDM) 的表型和功能模式中的作用。首先，利用CRISPR/Cas9系统在MSC中敲除CXCL12基因。然后，使用共培养系统研究 MSCsCXCL12−/− 和 MSCsCXCL12+/+ 在确定巨噬细胞表型中的作用。为了进一步分析 MSC 衍生的 CXCL12 生态位的作用，进行了 4T1 乳腺肿瘤细胞和用 MSCsCXCL12−/− 或 MSCsCXCL12+/+ 引发的巨噬细胞的共培养以及体内有限稀释测定。我们的结果显示，与 MSCsCXCL12+/+ 共培养的巨噬细胞中，作为 M2 标记物的 IL-4、IL-10、TGF-β 和 CD206 的表达显着增加，而 IL-6、TNF-α 和 iNOS 的表达则显着增加。反之则减少。当 4T1 细胞与 MSCCXCL12+/+ 诱导的 M2 巨噬细胞共培养时，多细胞肿瘤球体的数量和大小显着更高。我们还发现，将 4T1 细胞与 MSCCXCL12+/+ 引发的巨噬细胞共注射时，肿瘤的发生率显着更高。将 4T1 细胞与经 MSCsCXCL12−/− 预处理的巨噬细胞共注射后，肿瘤起始细胞显着减少。总之，我们的研究结果为 MSC 衍生的 CXCL12 在巨噬细胞表型转变为 M2 中的作用提供了新的线索，从而影响其在肿瘤发生中的功能。