title: BMP9 and COX-2 form an important regulatory loop in BMP9-induced osteogenic differentiation of mesenchymal stem cells.
abstract: Mesenchymal stem cells (MSCs) can self-renew and differentiate into osteogenic, chondrogenic, adipogenic and myogenic lineages. It's reported that bone morphogenetic protein 9 (BMP9) is one of the most potent osteogenic BMPs to initiate the commitment of MSCs to osteoblast lineage. Cyclooxygenase-2 (COX-2) is critical for bone fracture healing and osteogenic differentiation in MSCs. However, the relationship between COX-2 and BMP9 in osteogenesis remains unknown. Herein, we investigate the role of COX-2 in BMP9-induced osteogenesis in MSCs. We demonstrate that COX-2 is up-regulated as a target of BMP9 in MSCs. Both COX-2 inhibitor (NS-398) and COX-2 knockdown siRNAs can effectively decrease alkaline phosphatase (ALP) activities induced by BMP9 in MSCs. NS-398 also down-regulates BMP9-induced expression of osteopontin and osteocalcin, so does the matrix mineralization. The in vivo studies indicate that knockdown of COX-2 attenuates BMP9-induced ectopic bone formation. In perinatal limb culture assay, NS-398 is shown to reduce the hypertropic chondrocyte zone and ossification induced by BMP9. Mechanistically, knockdown of COX-2 significantly inhibits the BMP9 up-regulated expression of Runx2 and Dlx-5 in MSCs, which can be rescued by exogenous expression of COX-2. Furthermore, knockdown of COX-2 apparently reduces BMP9 induced BMPR-Smad reporter activity, the phosphorylation of Smad1/5/8, and the expression of Smad6 and Smad7 in MSCs. NS-398 blocks the expression of BMP9 mediated by BMP9 recombinant adenovirus. Taken together, our findings suggest that COX-2 plays an important role in BMP9 induced osteogenic differentiation in MSCs; BMP9 and COX-2 may form an important regulatory loop to orchestrate the osteogenic differentiation in MSCs.
authors: Chongqing key Laboratory for Oral Diseases and Biomedical Sciences, Chongqing, People's Republic of China; The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing, People's Republic of China.
authors: Jin-Hua
authors: JH
authors: Wang
authors: Ying-Zi
authors: YZ
authors: Liu
authors: Liang-Jun
authors: LJ
authors: Yin
authors: Liang
authors: L
authors: Chen
authors: Jun
authors: J
authors: Huang
authors: Yang
authors: Y
authors: Liu
authors: Ran-Xi
authors: RX
authors: Zhang
authors: Long-Yang
authors: LY
authors: Zhou
authors: Qiu-Jun
authors: QJ
authors: Yang
authors: Jin-Yong
authors: JY
authors: Luo
authors: Guo-wei
authors: GW
authors: Zuo
authors: Zhong-Liang
authors: ZL
authors: Deng
authors: Bai-Cheng
authors: BC
authors: He
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D055427:Growth Differentiation Factor 2 / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects*; D051379:Mice
chemical_list: D055427:Growth Differentiation Factor 2; D051546:Cyclooxygenase 2
keywords: BMP/Smad signaling; BMP9; COX-2; Mesenchymal stem cells; Osteogenic differentiation