Effect of Lipopolysaccharide on alveolar bone metabolism

我们最近发现，LPS刺激破骨细胞形成的IL-1的前体细胞在长期的人脐带血培养。这表明破骨细胞在LPS上形成的机制可能通过解聚来消除，这是由于存在于完整骨中的某些细胞类型的影响，介导了细胞因子的反应性。因此，我们测试了来自人骨肉瘤（MG 63）的克隆成骨细胞和来自人牙槽骨的成骨细胞对破骨细胞前体无反应群体的恢复激素和细胞因子反应的能力。我们发现LPS（100 ng/ml）处理的MG 63细胞培养物的条件培养基（CM）诱导人造血干细胞破骨细胞形成的两倍刺激。在培养基中以33%（v/v）浓度的CM稀释时观察到刺激。LPS对MG 63细胞IL-6、巨噬细胞集落刺激因子（M-CSF）和粒细胞巨噬细胞集落刺激因子（GM-CSF）基因表达的影响。在LPS处理的MG 63细胞中可检测到GM-CSF、IL-6和M-CSF转录物。然而，GM-CSF基因表达没有发生在PTH或非刺激成骨细胞培养。当CD 34阳性造血细胞与LPS处理的成骨细胞的CM孵育时，形成含有破骨细胞早期前体的CFU-GM集落。这一发现证明GM-CSF存在于刺激破骨细胞形成的无细胞CM中。此外，还证明了原位杂交研究可以在LPS处理的正常人骨成骨细胞中检测GM-CSF mRNA。这些实验表明，LPS通过对成骨细胞的主要作用刺激破骨细胞形成，所述成骨细胞被LPS诱导产生IL-6、M-CSF和GM-CSF，所述IL-6、M-CSF和GM-CSF又刺激破骨细胞形成，导致破骨细胞骨吸收。

We recentily found that LPS stimulates osteoclast formation by IL-1 production on its precursor cell in long-term human cord blood cultures. This suggests that the mechanisms of osteoclast formation on LPS might removed by disaggregation from the influence of some cell typy, present in intact bone, that mediates cytokine resposiveness. We therefore tested the ability of cloned osteoblastic cell derived from human osteosalcoma (MG63) and osteoblastic cells derived from human alveolar bone restore hormone and cytokine responsiveness to unresponsive populations of osteoclast precursors. We found that conditioned medium (CM) from LPS (100ng/ml) -treated MG63 cell cultures induced a two-fold stimulation of osteoclast formation from human hemopoietic stem cells. Stimulation was observed at dilution of 33% (v/v) concentration of CM in the medium. The effects of LPS onthe regulation of IL-6, macrophage-colony stimulating factor (M-CSF), and granulocyte macrophage-colony stimulating factor (GM-CSF) gene expression were also studied in MG63 cells. GM-CSF,IL-6, and M-CSF transcripts were detectable in LPS-treated MG63 cells. However, GM-CSF gene expression did not occur in PTH or non stimulated osteoblast cultures. When CD34-positive hemopoietic cells were incubated with CM from LPS-treated osteoblasts, CFU-GM colonies which contain osteoclast early precursors were formed. This finding is proof that GM-CSF was present in the cell-free CM that stimulated osteoclast formation. Furthermore demonstrate in situ hybridization studies could be performed to have GM-CSF mRNA in LPS-treated osteoblasts from normal human bone. These experiments suggest that LPS stimulates osteoclast formation through a primary action on osteoblastic cells, which cells are induced by the LPS to produce IL-6, M-CSF,and GM-CSF which in turn stimulate osteoclast formation, resulting in osteoclastic bone resorption.