Effect of Lipopolysaccharide on alveolar bone metabolism

我们最近发现，在长期的人类脐带血培养中，LPS通过IL-1在其前体细胞上的产生来刺激破骨细胞的形成。这表明，破骨细胞对LPS的形成机制可能会被一些细胞类型的影响所消除，这些细胞类型存在于完整的骨中，介导细胞因子的反应。因此，我们测试了来自人骨肉瘤（MG63）的克隆成骨细胞和来自人牙槽骨的成骨细胞对无反应的破骨细胞前体恢复激素和细胞因子反应的能力。我们发现，LPS （100ng/ml）处理过的MG63细胞培养物的条件培养基（CM）诱导人造血干细胞形成破骨细胞的两倍刺激。培养基中CM浓度为33% （v/v）时，观察到刺激。在MG63细胞中研究LPS对IL-6、巨噬集落刺激因子（M-CSF）和粒细胞巨噬集落刺激因子（GM-CSF）基因表达的调控作用。在lps处理的MG63细胞中检测到GM-CSF、IL-6和M-CSF转录物。然而，GM-CSF基因在PTH或非刺激成骨细胞培养中没有表达。当cd34阳性造血细胞与脂多糖处理的成骨细胞CM孵育时，形成含有破骨细胞早期前体的CFU-GM菌落。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，在lps处理的正常人骨成骨细胞中，可以进行GM-CSF mRNA的原位杂交研究。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的形成，成骨细胞被LPS诱导产生IL-6、M-CSF和GM-CSF，这些细胞反过来刺激破骨细胞的形成，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.