title: ERK 1/2 activation in enhanced osteogenesis of human mesenchymal stem cells in poly(lactic-glycolic acid) by cyclic hydrostatic pressure.
abstract: The aim of this study was to identify the signal transduction pathways and mechano-transducers that play critical roles in the processes induced by changes in cyclic hydrostatic pressure and fluid shear in 3-dimensional (3D) culture systems. Mesenchymal stem cells were loaded into a polymeric scaffold and divided into three groups according to the stress treatment: static, fluid shear, and hydrostatic pressure with fluid shear. Cells were exposed daily to a hydrostatic pressure of 0.2 MPa for 1 min followed by 14 min rest with fluid flow at 30 rpm. Protein extracts were analyzed by Western blot for extracellular signal-regulated kinase 1/2 (ERK1/2). The complexes were cultured under the mechanical stimuli for 21 days with or without phospho-ERK1/2 inhibitor (U0126) and evaluated by RT-PCR, calcium contents, and immunohistochemistry. Under conditions of mechanical stimulation, the activation of ERK1/2 was sustained or increased with time. U0126 suppressed mechanical stimuli-induced expression of osteocalcin. In addition, calcium contents and the degrees of osteocalcin and osteopontin staining were decreased by this inhibitor. These results demonstrate that mechanical stimuli, particularly hydrostatic pressure with fluid shear, enhance osteogenesis in 3D culture systems via ERK1/2 activation.
authors.affiliation: Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, Korea.
authors.forename: Su-Hyang
authors.initials: SH
authors.lastname: Kim
authors.forename: Yon Rak
authors.initials: YR
authors.lastname: Choi
authors.forename: Min Sung
authors.initials: MS
authors.lastname: Park
authors.forename: Jung Woog
authors.initials: JW
authors.lastname: Shin
authors.forename: Ki Dong
authors.initials: KD
authors.lastname: Park
authors.forename: Sung-Jae
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Lee
mesh_terms: D018929:Cell Culture Techniques; D002478:Cells, Cultured; D006801:Humans; D006874:Hydrostatic Pressure; D040542:Mechanotransduction, Cellular; D059630:Mesenchymal Stem Cells / Q000201:enzymology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010012:Osteogenesis; D013314:Stress, Mechanical
chemical_list: D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3