OBJECTIVETo explore the effects of cofilin on the actin cytoskeleton reorganization in osteoblasts induced by fluid shear stress.

METHODSFluid shear stress (1.2 Pa) was applied to osteoblasts for 0 (control group), 15, 30, 45, 60, 120 min in vitro. Cells were stained with fluorescein isothiocyanate (FITC)-phalloidin for fiber-actin, and confocal laser scanning microscope(CLSM) was used to observe the fluorescence of fiber-actin. Western blotting was used to detect the expression of the cofilin and the phospho-cofilin.

RESULTSActin filaments became organized into stress fibers that were thicker and more abundant than those in non-flowed cells. The fluorescence intensity (38.00 ± 6.88) of fiber-actin after 120 min (42.93 ± 6.41) loading it was 2.8 times as much as that in control group (15.41 ± 3.60, P < 0.05). Additionally, the level of phospho-cofilin protein was dramatically elevated after loading. Fluid shear stress induced an initial decrease of cofilin at 60 min. However, at 120 min cofilin (0.254 ± 0.026) increased to 1.5 times as much as that at 60 min (0.162 ± 0.004).

CONCLUSIONSThe results indicate that cofilin phosphorylation mediates fiber-actin reorganization in the osteoblasts induced by fluid shear stress.