Shimizu Sadanori, Okuda Naoki, Kato Norihiko, Rittling Susan R, Okawa Atsushi, Shinomiya Kenichi, Muneta Takeshi, Denhardt David T, Noda Masaki, Tsuji Kunikazu, Asou Yoshinori
International Research Center for Molecular Science in Tooth and Bone Diseases, and Tokyo Medical and Dental University, Tokyo, Japan.
Arthritis Rheum. 2010 May;62(5):1329-37. doi: 10.1002/art.27400.
To investigate the molecular mechanisms underlying particle-induced osteolysis, we focused on osteopontin (OPN), a cytokine and cell-attachment protein that is associated with macrophage chemoattractant and osteoclast activation.
We compared OPN protein levels in human periprosthetic osteolysis tissues with those in osteoarthritis (OA) synovial tissues. To investigate the functions of OPN during particle-induced osteolysis in vivo, titanium particles were implanted onto the calvaria of OPN-deficient mice and their wild-type (WT) littermates. Mice were killed on day 10 and evaluated immunohistologically. The effects of OPN deficiency on the secretion of inflammatory cytokines were examined using cultured bone marrow-derived macrophages (BMMs). BMMs from OPN-deficient and WT mice were cultured with titanium particles for 12 hours, and the concentrations of inflammatory cytokines in the conditioned media were measured by enzyme-linked immunosorbent assay.
Expression of OPN protein was enhanced in human periprosthetic osteolysis tissues as compared with OA synovial tissues. In the particle-induced model of osteolysis of the calvaria, bone resorption was significantly suppressed by OPN deficiency via inhibition of osteoclastogenesis, whereas an inflammatory reaction was observed regardless of the genotype. Results of immunostaining indicated that OPN protein was highly expressed in the membrane and bone surface at the area of bone resorption in WT mice. When BMMs were exposed to titanium particles, the concentration of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1alpha (IL-1alpha), IL-1beta, and IL-6, as well as chemotactic factors, such as monocyte chemoattractant protein 1 and macrophage inflammatory protein 1alpha, in the conditioned medium were significantly reduced by OPN deficiency. Whereas phagocytic activity of BMMs was not attenuated by OPN deficiency, phagocytosis-mediated NF-kappaB activation was impaired in OPN-deficient BMMs. These data indicated that OPN was implicated in the development of particle-induced osteolysis via the orchestration of pro-/antiinflammatory cytokines secreted from macrophages.
OPN plays critical roles in wear debris-induced osteolysis, suggesting that OPN is a candidate therapeutic target for periprosthetic osteolysis.
为研究颗粒诱导骨溶解的分子机制，我们聚焦于骨桥蛋白（OPN），一种与巨噬细胞趋化因子及破骨细胞活化相关的细胞因子和细胞黏附蛋白。
我们比较了人类假体周围骨溶解组织与骨关节炎（OA）滑膜组织中OPN蛋白水平。为研究体内颗粒诱导骨溶解过程中OPN的功能，将钛颗粒植入OPN基因缺陷小鼠及其野生型（WT）同窝小鼠的颅骨。于第10天处死小鼠并进行免疫组织学评估。使用培养的骨髓来源巨噬细胞（BMMs）检测OPN缺陷对炎性细胞因子分泌的影响。将OPN基因缺陷和WT小鼠的BMMs与钛颗粒共培养12小时，通过酶联免疫吸附测定法测量条件培养基中炎性细胞因子的浓度。
与OA滑膜组织相比，人类假体周围骨溶解组织中OPN蛋白表达增强。在颅骨颗粒诱导的骨溶解模型中，OPN缺陷通过抑制破骨细胞生成显著抑制了骨吸收，而无论基因型如何均观察到炎症反应。免疫染色结果表明，WT小鼠骨吸收区域的细胞膜和骨表面OPN蛋白高表达。当BMMs暴露于钛颗粒时，OPN缺陷显著降低了条件培养基中促炎细胞因子如肿瘤坏死因子α、白细胞介素-1α（IL-1α）、IL-1β和IL-6以及趋化因子如单核细胞趋化蛋白1和巨噬细胞炎性蛋白1α的浓度。虽然OPN缺陷未减弱BMMs的吞噬活性，但OPN缺陷的BMMs中吞噬作用介导的核因子κB活化受损。这些数据表明，OPN通过协调巨噬细胞分泌的促炎/抗炎细胞因子参与颗粒诱导骨溶解的发生发展。
OPN在磨损碎屑诱导的骨溶解中起关键作用，提示OPN是假体周围骨溶解的候选治疗靶点。
