Mechanism of condensing osteitis crisis following viral infection through toll-like receptors

本课题旨在阐明与病毒感染有关的冷凝性骨炎危象的发生机制。Toll样受体（TLR）1、3 -7在成骨细胞MC 3 T3-E1（E1）中表达，TLR 1-7在基质ST 2细胞中表达，TLR 3、6和7在骨肉瘤细胞MG-63中表达。TLR-3在所有细胞中表达最高。当这些细胞生长至汇合时，然后用poly I：C处理两周以上，它们形成矿化结节。它似乎比对照培养中更早。用含有6个拷贝的cbfa 1或最小碱性磷酸酶（ALP）启动子片段的报告基因构建体在poly I：C处理的MG-63细胞中进行DNA转染实验。在这两种情况下，启动子活性增加。DNA微阵列技术显示，poly I：C可增加E1细胞成纤维细胞生长因子2（FGF 2）mRNA的表达。此外，FGF 2的转录因子之一的早期生长反应1（EGR 1）蛋白表达也增加。因此，病毒感染骨组织后，可能会激活成骨细胞和基质细胞的天然免疫系统，导致骨矿化。这一机制可能与cbfa 1的激活和FGF 2的生成有关。对FGF 2信号转导系统的进一步研究可能需要详细阐明这些机制。

The aim of this project is to clarify the mechanisms of condensing osteitis crisis concerning to viral infection. Toll-like receptors (TLR) 1,3-7 expressed in osteoblastic MC3T3-E1 (E1) cells, TLR 1-7 in stromal ST2 cells, and TLR 3,6, and 7 in osteosarcoma cell, MG-63. TLR-3 expression is maximal in all of cells. When these cells were grown to confluent, and then treated with poly I:C for more two weeks, they formed mineralized nodules. It seems to be earlier than in control culture. DNA transfection experiments in with poly I:C treated-MG-63 cells were performed with reporter gene constructs containing 6 copies of cbfa1 or minimal alkaline phosphatase (ALP) promoter fragment. In both cases, the promoter activities increased. Moreover, it was shown using DNA microarray technology that poly I:C increased fibroblast growth factor 2 (FGF 2) mRNA expression in E1 cells. In addition, early growth response 1 (EGR 1), one of the transcription factors of FGF 2, protein expression also increased. Taken together, viral infection in bone tissue might cause to bone mineralization following to activate innate immunity systems of osteoblasts and stromal cells. It was suggested that activation of cbfa 1 following increase of FGF 2 production might be involved in this mechanism. More investigation with signal transduction systems in concerned with activation of FGF 2 signaling might need to elucidate these mechanism in detail.