Key Words. Human mesenchymal stem cell • Primary cilium • Mechanotransduction • Fluid flow • Osteogenic Differentiation • Proliferation

Physical loading is a potent stimulus required to maintain bone homeostasis, partly through the renewal and osteo-genic differentiation of mesenchymal stem cells (MSCs). However, the mechanism by which MSCs sense a biophys-ical force and translate that into a biochemical bone form-ing response (mechanotransduction) remains poorly understood. The primary cilium is a single sensory cellular extension, which has recently been shown to demonstrate a role in cellular mechanotransduction and MSC lineage commitment. In this study, we present evidence that short periods of mechanical stimulation in the form of oscilla-tory fluid flow (OFF) is sufficient to enhance osteogenic gene expression and proliferation of human MSCs (hMSCs). Furthermore, we demonstrate that the ciliu