OBJECTIVEMechanical stimulation alters cell's metabolism, but little is known about the effects of mechanical strain on the cytoskeleton of osteoblasts. This study was to investigate the changes of F-actin, a cytoskeleton protein of rat-derived osteoblast-like cell line UMR-106, and to provide theoretical basis for further investigation of mechanism of bone-remodeling.

METHODSCentrifugation was used to inflict UMR-106 the top-bottom axial stress (225 x g) expected and, confocal laser scanning microscope (LSCM) was used to examine the morphological changes 15, 30 min, and 1, 4, 6, 12, and 24 hr after undergoing physical strain. Unstrained cells were used as the controls respectively. The distribution of F-actin was observed after immunofluorescent staining and electronic photo was scanned for further analysis of osteoblasts' average fluorescence by spectrofluorimetric quantification.

RESULTSExcept the 24 hr group, the actin filaments of the strained osteoblasts were much shorter, more flimsy and tenuous than that of untreated osteoblasts and unlike the normal distribution of bundles or membrane-like of the control group, and they were arranged without direction. Its quantified fluorescence was significantly less than that of the controls. But the 24 hr group showed a normal distribution and a stronger fluorescence.

CONCLUSIONIt is concluded that the cytoskeleton of the strained osteoblasts has a reduced number of F-actin fibers and a unique abnormal morphology and could recover in 24 hr.