Einfluss fluider Scherspannungen auf die Mechanotransduktion in Osteoblasten

Bone adapts to mechanical loading. The bone cells in the lacuno-cananicular network are exposed to fluid flow, resulting in shear stress. Are the bone cells mechanosensitive for shear stress and do they activate calcium dependent intracellular signaltransduction pathways? We exposed primary bovine osteoblasts to shear stresses of 25, 45, 65 and 95 dyn/cm² and osteosarcoma cells MG-63 to 25 and 45 dyn/cm². Furthermore we measured the traction force of the cells by the method of Dembo and Wang under flow with 1 dyn/cm² and mechanical loading with 65 dyn/cm². We saw a calcium increase in 6% up to 26,4% of the POb under shear stress. So they are meachanosensitive for fluid flow. We measured no increase in cells with calcium release by raising the loading from 45 to 65 dyn/cm², so a threshold must exist, where cells in a mechanosensitive phase, react. Also the osteosarcoma cells MG-63 showed an increase in the fraction of cells with calcium response (13 % with 25 dyn/cm², 14,2% with 45 dyn/cm²). Under ground flow with 1 dyn/cm² we measured traction forces between 60,4 nN and 464,9 nN for POb and values from 3,4 nN to 222,4 nN for MG-63. Significant changes in traction forces by loading with 65 dyn/cm² appeared firstly after 120 s, so that calcium mobilisation goes ahead and changes in traction forces follow.