Response to mechanical strain in an immortalized pre‐osteoblast cell is dependent on ERK1/2

Fan, Xian; Rahnert, Jill A.; Murphy, Tamara C.; Nanes, Mark S.; Greenfield, Edward M.; Rubin, Janet

doi:10.1002/jcp.20581

Cited by 60 publications

(70 citation statements)

References 45 publications

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“…Our data were consistent with previous reports stating that mechanical stress induced the expression of the osteogenic transcription factor Runx2 at mRNA and/or protein levels (24). The expression of ALP, COLI and OC were elevated following the early application of CMS.…”

Section: Discussionsupporting

confidence: 93%

Osteogenic response of mesenchymal stem cells to continuous mechanical strain is dependent on ERK1/2-Runx2 signaling

et al. 2012

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Abstract. Mechanical stimuli are responsible for bone remodeling during orthodontic tooth movement. The role of mechanical stimulation in the regulation of the fate of bone mesenchymal stem cells (BMSCs) is of interest in bone regeneration and tissue engineering applications. However, the signaling pathway involved in strain-induced biochemical events in BMSCs is not well established and can be controversial. This study investigated strain-induced proliferation and differentiation of BMSCs, as well as the mechanism of mechanotransduction. BMSCs were exposed to continuous mechanical strain (CMS) of 10% at 1 Hz. The results showed that CMS reduced the proliferation of BMSCs and stimulated osteogenic differentiation by activating Runx2, followed by increased alkaline phosphatase (ALP) activity and mRNA expression of osteogenesis-related genes (ALP, collagen type I and osteocalcin). Furthermore, the phosphorylation level of extracellular regulated protein kinase (ERK)1/2 increased significantly at the onset of strain. However, the presence of U0126, a selective inhibitor of ERK1/2, blocked the induction of Runx2 and subsequent osteogenic events. These findings demonstrate that CMS regulated Runx2 activation and favored osteoblast differentiation through activation of the ERK1/2 signaling pathway. These results will contribute to a better understanding of strain-induced bone remodeling and will form the basis for the correct choice of applied force in orthodontic treatment.

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Section: Discussionsupporting

confidence: 93%

Osteogenic response of mesenchymal stem cells to continuous mechanical strain is dependent on ERK1/2-Runx2 signaling

et al. 2012

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“…We were not entirely surprised by this finding, since we have been able to show RANKL downregulation in an immortalized osteoblast line which does not express much eNOS or nNOS, and does not respond to strain with NO generation [5]. In the eNOS replete situation, in contrast, part of mechanical strain's effect is to increase eNOS expression, a process that requires earlier activation of ERK1/2 [9].…”

Section: Discussionmentioning

confidence: 91%

“…Skeletal loading promotes an anti-catabolic state where osteoclastic bone resorption is prevented [38]; this requires suppression of RANKL signaling by bone cells. Mechanistically, strain produces this catabolic state by decreasing RANKL mRNA expression in bone cells [5,39], while concurrently causing the generation of nitric oxide [9]. This is also true for loading effects due to shear, where fluid flow generates nitric oxide [10,40], and also decreases RANKL [6].…”

Section: Discussionmentioning

confidence: 99%

“…Many laboratories have shown that loading in vitro and in vivo leads to positive skeletal balance [1][2][3]. Anti-catabolic effects of loading involve inhibition of the expression of Receptor for Activated NF-κB Ligand (RANKL) [4][5][6] which decreases the potential for osteoclast formation [7,8]. Mechanical load also increases nitric oxide generation in bone cells: mechanical strain induces eNOS [9] and fluid shear both activates and induces this NOS isoform [10].…”

Section: Introductionmentioning

confidence: 99%

“…Mechanical load also increases nitric oxide generation in bone cells: mechanical strain induces eNOS [9] and fluid shear both activates and induces this NOS isoform [10]. Nitric oxide has potent effects on osteoclasts in bone, both decreasing their formation through repression of RANKL [5,11] as well as through decreasing resorptive activity [12]. In an effort to understand mechanical effects on the skeleton, it is important to clarify whether nitric oxide is required for the anti-catabolic effects of mechanical loading.…”

Section: Introductionmentioning

confidence: 99%

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The role of nitric oxide in the mechanical repression of RANKL in bone stromal cells

Rahnert

Fan

Case

et al. 2008

Bone

Self Cite

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Both mechanical loading and nitric oxide (NO) have positive influences on bone mass. NO production is induced by mechanical strain via upregulation of eNOS mRNA and protein, the predominant NOS in adult bone. At the same time, strain causes decreased expression of RANKL, a factor critical for osteoclastogenesis. In this study, we harvested primary stromal cells from wildtype (WT) and eNOS (−/−) mice to test whether induction of NO by mechanical strain was necessary for transducing mechanical inhibition of RANKL. We found that strain inhibition of RANKL expression was prevented by NOS inhibitors (L-NAME and L-NMMA) in WT stromal cells. Surprisingly, stromal cells from eNOS (−/−) mice showed significant mechanical repression of RANKL expression (p<0.05). Mechanical strain still increased NO production in the absence of eNOS, and was abolished by SMTC, a specific nNOS inhibitor. nNOS mRNA and protein expression were increased by strain in eNOS (−/−) but not in WT cells, revealing that nNOS was mechanically sensitive. When NO synthesis was blocked with either SMTC or siRNA targeting nNOS in eNOS (−/−) cells however, strain still was able to suppress RANKL expression by 34%. This indicated that strain suppression of RANKL can also occur through non-NO dependent pathways. While our results confirm the importance of NO in the mechanical control of skeletal remodeling, they also suggest alternative signaling pathways by which mechanical force can produce anti-catabolic effects on the skeleton.

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Effects of physiological mechanical strains on the release of growth factors and the expression of differentiation marker genes in human osteoblasts growing on Ti‐6Al‐4V

Kokkinos

Zarkadis

Kletsas

et al. 2008

J Biomedical Materials Res

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Mechanical loading factors at the bone-implant interface are critical for the osseointegration and clinical success of the implant. The aim of the present investigation was to study the effects of mechanical strain on the orthopedic biomaterial Ti-6Al-4V/osteoblast interface, using an in vitro model. Homogeneous strain was applied to human bone marrow derived osteoblasts (HBMDOs) cultured on Ti-6Al-4V, at physiological levels (strain magnitudes 500 microstrain (microepsilon) and 1000 microepsilon, at frequencies of load application 0.5 Hz and 1 Hz), by a mechanostimulatory system, based on the principle of four-point bending. Semi-quantitative reverse transcription-polymerase chain reaction (sqRT-PCR) was used to determine the mRNA expression of Cbfa1 and osteocalcin at different loading conditions. The release of growth factors as a response to stretch was also investigated by transferring stretch-conditioned media to nonstretched cells and by measuring their effect on the regulation of DNA synthesis. Mechanical loading was found to contribute to the regulation of osteoblast differentiation by influencing the level of the osteoblast-specific transcription factor Cbfa1, both at the mRNA and protein level, and also the level of osteocalcin, which is regarded as the most osteoblast-specific gene. Both genes were differentially expressed shortly after the application of different mechanical stimuli, in terms of strain frequency, magnitude, and time interval. Media conditioned from mechanically stressed HBMDOs stimulate DNA synthesis more intensely compared to media conditioned from unstressed control cultures, indicating that mechanical strain induces the release of a mitogenic potential that regulates cell proliferation.

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Response to mechanical strain in an immortalized pre‐osteoblast cell is dependent on ERK1/2

Cited by 60 publications

References 45 publications

Osteogenic response of mesenchymal stem cells to continuous mechanical strain is dependent on ERK1/2-Runx2 signaling

Osteogenic response of mesenchymal stem cells to continuous mechanical strain is dependent on ERK1/2-Runx2 signaling

The role of nitric oxide in the mechanical repression of RANKL in bone stromal cells

Effects of physiological mechanical strains on the release of growth factors and the expression of differentiation marker genes in human osteoblasts growing on Ti‐6Al‐4V

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