ABSTRACT: Background: F.nucleatum is one of the important pathogens of periodontitis, and the main symptom of periodontitis is alveolar bone loss. The study of F.nucleatum in alveolar bone loss caused by periodontitis is still very insufficient. In this study, the biological behavior of osteoblasts stimulated by F.nucleatum was studied to elucidate the mechanism of bone loss in periodontitis. Methods:A primary rat calvarial osteoblast culture model was established and invaded repeatedly with F.nucleatum (ATCC 25586). Transcriptome analysis at multiple time points(days 1, 3, 7, 14, 21 and 28) was applied to identify gene expression changes in osteoblasts stimulated by F.nucleatum. Cell-counting and EDU-labeling assay were used to analyze the effects of F.nucleatum on the cell proliferation. Flow cytometry and enzyme linked immunosorbent assay (ELISA) was used to analysis the cell apoptosis, cell cycle and secreted inflammatory cytokines changes. ALP activity testing, Alizarin red mineralized nodules staining and calcium content assays, qPCR and western blot were carried on to evaluate the osteogenic differentiation and mineralization of osteoblasts. Results: Cytology experiments and RNA-seq analysis showed that F.nucleatum could inhibit cell proliferation, promote cell apoptosis, block cell cycle of osteoblasts and promote inflammatory cytokines production in a dose- and time-dependent manner. Besides, F. nucleatum could significantly inhibited osteoblasts differentiation and mineralization via a series inhibition of the differentiation regulatory genes and proteins. Whole-transcriptome analysis identified a total of 235 transcripts that were differentially expressed in all six time-points, most of which were inflammatory-related genes. The genes, Ccl2, Ccl20, Csf1, Cx3cl1, Cxcl1, Cxcl3, Il6, Birc3, Map3k8, Nos2, Nfkb2, Tnfrsf1b and Vcam1, played core roles in a PPI network and interacted closely with other ones in the infection. In addition, 133 osteogenesis-related DEGs were time-serially dynamically changed in a short time-series expression miner (STEM) analysis, which were enriched in multiple cancer-related pathways. The core dynamic DEGs (Mnda, Cyp1b1, Comp, Phex, Mmp3, Tnfrsf1b, Fbln5 and Nfkb2) had been reported to be closely related to the development and metastasis in tumor and cancer progress. This study is the first to evaluate the long-term interaction of F. nucleatum on osteoblasts, which might increase the risk of cell carcinogenesis of normal osteoblasts, and provides new insight into the pathogenesis of bacterial-induced bone destruction.
