Park Hyewon, Jung Youn-Kwan, Park Ok-Jin, Lee Yeon Ju, Choi Je-Yong, Choi Youngnim
Department of Oromaxillofacial Infection & Immunity and Dental Research Institute, School of Dentistry, Seoul National University, Jongro-gu, Seoul, Republic of Korea.
J Immunol. 2005 Dec 1;175(11):7193-201. doi: 10.4049/jimmunol.175.11.7193.
We incidentally found that osteoclast precursors and mature osteoclasts express Fas ligand (FasL) as well as Fas, which was confirmed by flow cytometry, immunofluorescent staining, and RT-PCR. The aim of this study was to determine the role of FasL in differentiation and cell death of osteoclasts. To study the role of FasL in osteoclastogenesis, neutralizing anti-FasL mAb or rFasL was added during receptor activator of NF-kappaB ligand (RANKL)-induced osteoclastogenesis using bone marrow-derived macrophages. Neutralization of endogenous FasL by anti-FasL mAb decreased osteoclastogenesis, whereas rFasL enhanced osteoclast differentiation in a dose-dependent manner. In addition, rFasL up-regulated the secretion of osteoclastogenic cytokines, such as IL-1beta and TNF-alpha, and the activation of NF-kappaB. Functional blocking of IL-1beta and TNF-alpha using IL-1 receptor antagonist and soluble TNFR confirmed that those cytokines mediated the effect of FasL on osteoclastogenesis. The osteoclast precursors were relatively resistant to rFasL-induced apoptosis especially before RANKL treatment, resulting in minimal cell loss by rFasL treatment during osteoclastogenesis. Although rFasL increased the cell death of mature osteoclasts, growth factor withdrawal induced much more cell death. However, anti-FasL mAb did not affect the survival of mature osteoclasts, suggesting that the endogenous FasL does not have a role in the apoptosis of osteoclasts. Finally, in contrast to the effect on apoptosis, rFasL-assisted osteoclastogenesis was not mediated by caspases. In conclusion, FasL has a novel function in bone homeostasis by enhancing the differentiation of osteoclasts, which was not considered previously.
我们偶然发现破骨细胞前体和成熟破骨细胞表达Fas配体（FasL）以及Fas，这通过流式细胞术、免疫荧光染色和逆转录聚合酶链反应得以证实。本研究的目的是确定FasL在破骨细胞分化和细胞死亡中的作用。为了研究FasL在破骨细胞生成中的作用，在使用骨髓来源的巨噬细胞进行核因子κB受体活化因子配体（RANKL）诱导的破骨细胞生成过程中加入中和性抗FasL单克隆抗体或重组FasL。抗FasL单克隆抗体对内源性FasL的中和作用降低了破骨细胞生成，而重组FasL以剂量依赖的方式增强了破骨细胞分化。此外，重组FasL上调了破骨细胞生成细胞因子如白细胞介素-1β（IL-1β）和肿瘤坏死因子-α（TNF-α）的分泌以及核因子κB的活化。使用IL-1受体拮抗剂和可溶性肿瘤坏死因子受体对IL-1β和TNF-α进行功能阻断证实，这些细胞因子介导了FasL对破骨细胞生成的作用。破骨细胞前体对重组FasL诱导的凋亡相对具有抗性，尤其是在RANKL处理之前，导致在破骨细胞生成过程中重组FasL处理引起的细胞损失最小。尽管重组FasL增加了成熟破骨细胞的细胞死亡，但生长因子撤除诱导的细胞死亡更多。然而，抗FasL单克隆抗体不影响成熟破骨细胞的存活，这表明内源性FasL在破骨细胞凋亡中不起作用。最后，与对凋亡的影响相反，重组FasL辅助的破骨细胞生成不是由半胱天冬酶介导的。总之，FasL通过增强破骨细胞分化在骨稳态中具有一种新功能，这是之前未被考虑到的。
