Mechanical Strain Regulates Osteoblast Proliferation through Integrin-Mediated ERK Activation

Mechanical strain plays a critical role in the proliferation, differentiation and maturation of bone cells. As mechanical receptor cells, osteoblasts perceive and respond to stress force, such as those associated with compression, strain and shear stress. However, the underlying molecular mechanisms of this process remain unclear. Using a four-point bending device, mouse MC3T3-E1 cells was exposed to mechanical tensile strain. Cell proliferation was determined to be most efficient when stimulated once a day by mechanical strain at a frequency of 0.5 Hz and intensities of 2500 µε with once a day, and a periodicity of 1 h/day for 3 days. The applied mechanical strain resulted in the altered expression of 1992 genes, 41 of which are involved in the mitogen-activated protein kinase (MAPK) signaling pathway. Activation of ERK by mechanical strain promoted cell proliferation and inactivation of ERK by PD98059 suppressed proliferation, confirming that ERK plays an important role in the response to mechanical strain. Furthermore, the membrane-associated receptors integrin β1 and integrin β5 were determined to regulate ERK activity and the proliferation of mechanical strain-treated MC3T3-E1 cells in opposite ways. The knockdown of integrin β1 led to the inhibition of ERK activity and cell proliferation, whereas the knockdown of integrin β5 led to the enhancement of both processes. This study proposes a novel mechanism by which mechanical strain regulates bone growth and remodeling

Sodium-hydrogen exchanger, cardiac overload, and myocardial hypertrophy

Overload of neonatal and adult cardiomyocytes and multicellular myocardial preparations, which include whole hearts, are accompanied by an enhanced activity of the Na+/H+ exchanger 1 (NHE-1). Exogenous administration of prohypertrophic agents such as angiotensin II (Ang II), endothelin-1 (ET-1), and α1-adrenergic agonists also stimulates NHE-1 activity, which leads to an increased concentration of intracellular Na+ ([Na+]i). Moreover, inhibition of NHE-1 activity prevents the increase in [Na+]i, induces the regression of cardiac hypertrophy, and exerts beneficial effects in experimental heart failure. The present review summarizes the current knowledge of the causative factors and pathophysiological correlation of cardiac overload and NHE-1 activity.Centro de Investigaciones Cardiovasculare

Sodium-hydrogen exchanger, cardiac overload, and myocardial hypertrophy

Overload of neonatal and adult cardiomyocytes and multicellular myocardial preparations, which include whole hearts, are accompanied by an enhanced activity of the Na+/H+ exchanger 1 (NHE-1). Exogenous administration of prohypertrophic agents such as angiotensin II (Ang II), endothelin-1 (ET-1), and α1-adrenergic agonists also stimulates NHE-1 activity, which leads to an increased concentration of intracellular Na+ ([Na+]i). Moreover, inhibition of NHE-1 activity prevents the increase in [Na+]i, induces the regression of cardiac hypertrophy, and exerts beneficial effects in experimental heart failure. The present review summarizes the current knowledge of the causative factors and pathophysiological correlation of cardiac overload and NHE-1 activity.Centro de Investigaciones Cardiovasculare

Sodium-hydrogen exchanger, cardiac overload, and myocardial hypertrophy

Overload of neonatal and adult cardiomyocytes and multicellular myocardial preparations, which include whole hearts, are accompanied by an enhanced activity of the Na+/H+ exchanger 1 (NHE-1). Exogenous administration of prohypertrophic agents such as angiotensin II (Ang II), endothelin-1 (ET-1), and α1-adrenergic agonists also stimulates NHE-1 activity, which leads to an increased concentration of intracellular Na+ ([Na+]i). Moreover, inhibition of NHE-1 activity prevents the increase in [Na+]i, induces the regression of cardiac hypertrophy, and exerts beneficial effects in experimental heart failure. The present review summarizes the current knowledge of the causative factors and pathophysiological correlation of cardiac overload and NHE-1 activity.Centro de Investigaciones Cardiovasculare

Cellular Mechanotransduction: From Tension to Function

Living cells are constantly exposed to mechanical stimuli arising from the surrounding extracellular matrix (ECM) or from neighboring cells. The intracellular molecular processes through which such physical cues are transformed into a biological response are collectively dubbed as mechanotransduction and are of fundamental importance to help the cell timely adapt to the continuous dynamic modifications of the microenvironment. Local changes in ECM composition and mechanics are driven by a feed forward interplay between the cell and the matrix itself, with the first depositing ECM proteins that in turn will impact on the surrounding cells. As such, these changes occur regularly during tissue development and are a hallmark of the pathologies of aging. Only lately, though, the importance of mechanical cues in controlling cell function (e.g., proliferation, differentiation, migration) has been acknowledged. Here we provide a critical review of the recent insights into the molecular basis of cellular mechanotransduction, by analyzing how mechanical stimuli get transformed into a given biological response through the activation of a peculiar genetic program. Specifically, by recapitulating the processes involved in the interpretation of ECM remodeling by Focal Adhesions at cell-matrix interphase, we revise the role of cytoskeleton tension as the second messenger of the mechanotransduction process and the action of mechano-responsive shuttling proteins converging on stage and cell-specific transcription factors. Finally, we give few paradigmatic examples highlighting the emerging role of malfunctions in cell mechanosensing apparatus in the onset and progression of pathologies