Osteoblast cells are responsible for synthesizing new bone tissue, and determining how to control osteoblastic differentiation is vital to the treatment of osteoporosis. In this study, we show that pentraxin 3 (PTX3) signaling is involved in the regulation of osteoblastic differentiation in MC3T3-E1 cells. Our data reveal that PTX3 is abundantly expressed in MC3T3-E1 cells and that its expression is inducible by the introduction of osteogenic induction medium (OIM). Overexpression of PTX3 was observed to significantly increase the expression of four osteoblast signature genes, including runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OCN) and osterix (OSX), suggesting that the overexpression of PTX3 promotes osteoblastic differentiation. The relative level of gene expression between OIM and OIM plus overexpressed PTX3 was evaluated using the Affymetrix Gene Chip® mouse gene microarray. PTX3-related DEGs were screened. GO functional and KEGG pathway enrichment analyses were performed, and the PI3K/Akt signaling pathway was primarily involved in the osteogenic differentiation of PTX3. Protein-protein interactions were also constructed, and the MCODE plugin calculated modules of PPI networks. Moreover, we show that the effect of PTX3 is mediated by its induction of the PI3K/Akt signaling pathway. Mechanistically, we show that the action of PTX3 requires the activation of PI3K and Akt, and deactivation of PI3K by its inhibitor LY294002 weakens the PTX3-mediated induction of osteoblast signature genes, ALP, and matrix mineralization. This study revealed a new role played by PTX3 and suggest a potential mechanism governing the osteoblastic differentiation of MC3T3-E1 cells.

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