ABSTRACT
Mechanical stress plays an important role in bone growth and bone remodeling. It causes stretch stress and fluid shear stress (FSS), which can be sensed by mechanosensory cells, e.g. osteocytes and osteoblasts, and further induce changes of gene expression in those cells. The FSS is thought to be the main cause in this process. However, up to now, it is still not clear what signals are triggered in the mechanosensory cells cultured in vitro and how the FSS exactly affects the expression of specific proteins. Evidences have shown that Ca2+ signaling pathway, Cyclooxygenase-prostaglandin E2 pathway, protein kinase A/protein kinase C (PKA/PKC) pathway, and drosophila mothers against decapentaplegic (Smad) protein pathway may be the key players in osteoblast differentiation by FSS. The precise mechanism involved in mechanotransduction and signal transduction remains to be elucidated. The present review gives a brief summary on the effects of these signaling pathways on the differentiation of osteoblasts cultured in vitro under FSS, to get the message of the present situation of the research on the stress transmission and signal transduction influencing osteoblast molecular activity, and to provide reference for further study on its specific mechanism.