Study on osteoclast activiting factor expressed by osteoblasts/stromal cells

我们研究了成骨细胞/基质细胞表达的破骨细胞激活因子的特性。本研究建立了大量纯化的单核和多核破骨细胞的获取方法。利用纯化方法，我们分析了成骨细胞/基质细胞激活破骨细胞的机制：(1)成骨细胞促进纯化的单核和多核破骨细胞存活，从而形成多核破骨细胞。(2)成骨细胞产生的M-CSF也能刺激破骨细胞的存活，但不能刺激破骨细胞的凹坑形成活性。(3)从M-CSF缺陷的OP/OP小鼠获得的成骨细胞不仅能刺激破骨细胞的存活，而且还能刺激破骨细胞的凹坑形成活性。(4)成骨细胞诱导的破骨细胞凹坑形成活性被骨保护素(a dec…)抑制(5)破骨细胞高表达IL-1 1型受体和ODF受体(RANK)。IL-1或ODF处理破骨细胞可诱导NF-κB的激活。(6)IL-1和ODF刺激破骨细胞凹陷形成活性。IL-1受体拮抗剂可抑制IL-1诱导的破骨细胞激活，而OPG不抑制OPG诱导的破骨细胞激活，而OPG可特异性抑制ODF诱导的破骨细胞激活。最近有研究表明，TRAF6基因敲除小鼠发生了严重的骨化病。在TRAF6基因敲除的小鼠中，在骨骼中发现了许多破骨细胞，但它们没有形成褶皱的边界。由于IL-1受体和RANK被证明与TRAF6相互作用，TRAF6介导的信号在IL-1和RANK诱导的破骨细胞激活中似乎是重要的。研究还表明，核因子-kB的激活在诱导破骨细胞凹陷形成活性中起重要作用。较少

We have investigated characteristics of osteoclast activating factor expressed by osteoblasts/stromal cells. The method for obtaining a large number of purified mononuclear and multinucleated osteoclasts was established in this study. Using the purification method, we analyzed the mechanism of activation of osteoclasts by osteoblasts/stromal cells.(1) Osteoblasts enhanced survival of purified mononuclear and multinucleated osteoclasts, which resulted in formation of multinucleated osteoclasts. Osteoblasts also stimulated resorption pit-forming activity of osteoclasts through a mechanism involving cell-to-cell contact.(2) M-CSF produced by osteoblasts also stimulated the survival of osteoclasts, but failed to stimulated pit-forming activity of osteoclasts.(3) Osteoblasts obtained from M-CSF-deficient op/op mice stimulated not only survival of osteoclasts but also their pit-forming activity.(4) Osteoblast-induced pit forming activity of osteoclasts was inhibited by osteoprotegerin (a dec … More oy receptor for ODF) simultaneously added.(5) Osteoclasts expressed high levels of IL-1 type 1 receptors and ODF receptors (RANK). Treatment of osteoclasts with IL-1 or ODF induced activation of NF-κB.(6) IL-1 and ODF stimulated pit-forming activity of osteoclasts. IL-1 -induced osteoclast activation was inhibited by IL-1 receptor antagonist but not OPG, whereas ODF-induced osteoclast activation was specifically inhibited by OPG.These results indicate that osteoclast activating factor expressed by osteoblasts/stromal cells is indeed ODF, the cDNA of which cloned in 1998. Recently, it was shown that TRAF6 knockout mice developed severe osteopetrosis. In TRAF6 knockout mice, many osteoclasts were found in bone but they failed to develop ruffled borders. As IL-1 receptors and RANK are shown to be interact with TRAF6, TRAF6-mediated signals appear to be important for IL-1 and RANK-induced activation of osteoclasts. It is also suggested that activation of NF-KB is important for induction of pit-forming activity of osteoclasts. Less