Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.
Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN, USA.
J Bone Miner Res. 2021 Aug;36(8):1580-1593. doi: 10.1002/jbmr.4314. Epub 2021 May 14.
Osteomacs (OM) are specialized bone-resident macrophages that are a component of the hematopoietic niche and support bone formation. Also located in the niche are a second subset of macrophages, namely bone marrow-derived macrophages (BM Mφ). We previously reported that a subpopulation of OM co-express both CD166 and CSF1R, the receptor for macrophage colony-stimulating factor (MCSF), and that OM form more bone-resorbing osteoclasts than BM Mφ. Reported here are single-cell quantitative RT-PCR (qRT-PCR), mass cytometry (CyTOF), and marker-specific functional studies that further identify differences between OM and BM Mφ from neonatal C57Bl/6 mice. Although OM express higher levels of CSF1R and MCSF, they do not respond to MCSF-induced proliferation, in contrast to BM Mφ. Moreover, receptor activator of NF-κB ligand (RANKL), without the addition of MCSF, was sufficient to induce osteoclast formation in OM but not BM Mφ cultures. OM express higher levels of CD166 than BM Mφ, and we found that osteoclast formation by CD166 OM was reduced compared with wild-type (WT) OM, whereas CD166 BM Mφ showed enhanced osteoclast formation. CD110/c-Mpl, the receptor for thrombopoietin (TPO), was also higher in OM, but TPO did not alter OM-derived osteoclast formation, whereas TPO stimulated BM Mφ osteoclast formation. CyTOF analyses demonstrated OM uniquely co-express CD86 and CD206, markers of M1 and M2 polarized macrophages, respectively. OM performed equivalent phagocytosis in response to LPS or IL-4/IL-10, which induce polarization to M1 and M2 subtypes, respectively, whereas BM Mφ were less competent at phagocytosis when polarized to the M2 subtype. Moreover, in contrast to BM Mφ, LPS treatment of OM led to the upregulation of CD80, an M1 marker, as well as IL-10 and IL-6, known anti-inflammatory cytokines. Overall, these data reveal that OM and BM Mφ are distinct subgroups of macrophages, whose phenotypic and functional differences in proliferation, phagocytosis, and osteoclast formation may contribute physiological specificity during health and disease. © 2021 American Society for Bone and Mineral Research (ASBMR).
成骨细胞（OM）是一种专门的骨驻留巨噬细胞，是造血龛的组成部分，支持骨形成。龛中还存在另一群巨噬细胞，即骨髓来源的巨噬细胞（BM Mφ）。我们之前报道过，OM 的一个亚群同时表达 CD166 和巨噬细胞集落刺激因子（MCSF）的受体 CSF1R，OM 形成的破骨细胞比 BM Mφ 更多。本文报道了单细胞定量 RT-PCR（qRT-PCR）、质谱流式细胞术（CyTOF）和标记物特异性功能研究，进一步鉴定了来自新生 C57Bl/6 小鼠的 OM 和 BM Mφ 之间的差异。虽然 OM 表达更高水平的 CSF1R 和 MCSF，但与 BM Mφ 不同，它们对 MCSF 诱导的增殖没有反应。此外，核因子-κB 配体受体激活剂（RANKL），无需添加 MCSF，足以诱导 OM 培养物中的破骨细胞形成，但不能诱导 BM Mφ 培养物中的破骨细胞形成。OM 表达的 CD166 水平高于 BM Mφ，我们发现与野生型（WT）OM 相比，CD166 OM 形成的破骨细胞减少，而 CD166 BM Mφ 显示出增强的破骨细胞形成。OM 中还表达更高水平的 CD110/c-Mpl，它是血小板生成素（TPO）的受体，但 TPO 不会改变 OM 衍生的破骨细胞形成，而 TPO 刺激 BM Mφ 破骨细胞形成。CyTOF 分析表明，OM 独特地共同表达 CD86 和 CD206，分别是 M1 和 M2 极化巨噬细胞的标志物。OM 对 LPS 或 IL-4/IL-10 的吞噬作用反应相同，这分别诱导向 M1 和 M2 亚型的极化，而 BM Mφ 在向 M2 亚型极化时吞噬能力较低。此外，与 BM Mφ 不同，LPS 处理的 OM 导致 M1 标志物 CD80 的上调，以及抗炎细胞因子 IL-10 和 IL-6 的上调。总的来说，这些数据表明 OM 和 BM Mφ 是巨噬细胞的不同亚群，它们在增殖、吞噬作用和破骨细胞形成方面的表型和功能差异可能有助于在健康和疾病期间发挥生理特异性。
