THE EFFECTS OF MECHANICAL STIMULATION ON THE DISTRIBUTION OF BETA(1) INTEGRIN AND EXPRESSION OF BETA(1)-INTEGRIN MESSENGER-RNA IN TE-85 HUMAN OSTEOSARCOMA CELLS

Mechanical stimulation of the skeleton alters the metabolism of bone c ells, but the effects of mechanical strain on the cytoskeleton of oste oblasts are poorly understood. While changes in the distribution of th e cytoskeleton in mechanically strained cells have been reported, litt le is known about the pathways by which these changes are transduced i nto cell functions. Human osteosarcoma (HOS) TE-85 cells were cultured in Dubelcco's modified Eagle's medinm/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 b eta(1) integrin was studied immunocytochemically. Total RNA was isolat ed at every period of time and Northern blots were used to study the e ffects of strain on the levels of beta(1)-integrin expression. The res ults indicated that mechanical strain increased the synthesis of beta( 1) integrin. Northern blots showed that beta(1) mRNA expression was in creased significantly (p < 0.005) at 30 min and 3 days of strain appli cation. Strain also affected beta(1) distribution markedly in 24-h cul tures. The response of HOS cells to mechanical strain demonstrates tha t the cytoskeleton of the osteoblast adapts to strain through the stim ulation of specific cytoskeletal and receptor proteins. These results suggest a pathway through which mechanical strain is transmitted to th e osteoblastic-like cells.