Continuous inhibition of MAPK signaling promotes the early osteoblastic differentiation and mineralization of the extracellular matrix.
We screened the small molecule compounds that stimulate osteogenesis by themselves or promote bone morphogenetic protein (BMP)-induced bone formation. We found that a specific inhibitor for MAPK/extracellular signal-regulated kinase kinase (MEK)-1, promoted the early osteoblastic differentiation and mineralization of extracellular matrix (ECM) in C2Cl2 pluripotent mesenchymal cells treated with recombinant human BMP-2 (rhBMP-2) and MC3T3-E1 preosteoblastic cells. ALP activity was synergistically increased by the treatment with a specific MEK-1 inhibitor PD98059 and rhBMP-2 in both cell lines. Twenty-five micromolar PD98059 promoted mineralization of ECM in rhBMP-2-treated C2Cl2 cells and MC3T3-E1 cells. In contrast, PD98059 reduced osteocalcin (OCN) secretion and its transcriptional level in rhBMP-2-treated C2Cl2 cells but increased its secretion and mRNA level in MC3T3-E1 cells. Stable expression of a dominant-negative MEK-1 mutant in C2Cl2 cells represented high ALP activity and low osteocalcin production in the presence of rhBMP-2, while a constitutively active mutant of MEK-1 attenuated both of them. Together, our results indicated that BMP-2-induced mineralization of ECM of pluripotent mesenchymal stem cells and preosteoblastic cells could be controlled by a fine tuning of the MAPK signaling pathway. Further, MEK-1 inhibitors would be useful for the promotion of bone formation, for instance, the treatments for delayed fracture healing or advance of localized osteoporotic change after fracture healing.
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005109:Extracellular Matrix / Q000187:drug effects* / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology*; D005799:Genes, Dominant; D006801:Humans; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D008903:Minerals / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000502:physiology; D011994:Recombinant Proteins; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta; D048051:p38 Mitogen-Activated Protein Kinases
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008903:Minerals; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D015675:Osteocalcin; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one