The effects of mechanical stimulation on the distribution of β1 integrin and expression of β1-integrin mRNA in TE-85 human osteosarcoma cells

Mechanical stimulation of the skeleton alters the metabolism of bone cells, but the effects of mechanical strain on the cytoskeleton of osteoblasts are poorly understood. While changes in the distribution of the cytoskeleton in mechanically strained cells have been reported, little is known about the pathways by which these changes are transduced into cell functions. Human osteosarcoma (HOS) TE-85 cells were cultured in Dubelccoʹs modified Eagleʹs medium/F-12 and grown to confluency in Flexercell type I dishes in a humidified incubator with 5% CO2 and 95% air. Intermittent strain (3 cycles/min) was applied to the cells for periods of 15 and 30 min, 2, 4 and 24 h, and 3, 5, 7, 10, 14, 20 and 28 days. Unstrained cells were used as controls. The distribution of β1, integrin was studied immunocytochemically. Total RNA was isolated at every period of time and Northern blots were used to study the effects of strain on the levels of β1-integrin expression. The results indicated that mechanical strain increased the synthesis of β1-integrin. Northern blots showed that β1 mRNA expression was increased significantly (p < 0.005) at 30 min and 3 days of strain application. Strain also affected β1 distribution markedly in 24-h cultures. The response of HOS cells to mechanical strain demonstrates that the cytoskeleton of the osteoblast adapts to strain through the stimulation of specific cytoskeletal and receptor proteins. These results suggest a pathway through which mechanical strain is transmitted to the osteoblastic-like cells.