Mechanosensitivity of human osteosarcoma cells and phospholipase C β2 expression

Bone adapts to mechanical load by osteosynthesis, suggesting that osteoblasts might respond to mechanical stimuli. We therefore investigated cell proliferation and phospholipase C (PLC) expression in osteoblasts. One Hertz uniaxial stretching at 4000 μstrains significantly increased the proliferation rates of human osteoblast-like osteosarcoma cell line MG-63 and primary human osteoblasts. However, U-2/OS, SaOS-2, OST, and MNNG/HOS cells showed no significant changes in proliferation rate. We investigated the expression pattern of different isoforms of PLC in these cell lines. We were able to detect PLC β1, β3, γ1, γ2, and δ1 in all cells, but PLC β2 was only detectable in the mechanosensitive cells. We therefore investigated the possible role of PLC β2 in mechanotransduction. Inducible antisense expression for 24 h inhibited the translation of PLC β1 in U-2/OS cells by 35% and PLC β2 in MG-63 by 29%. Fluid shear flow experiments with MG-63 lacking PLC β2 revealed a significantly higher level of cells losing attachment to coverslips and a significantly lower number of cells increasing intracellular free calcium.