TRPV4-mediates oscillatory fluid shear mechanotransduction in mesenchymal stem cells in part via the primary cilium

Abstract

Skeletal homeostasis requires the continued replenishment of the bone forming osteoblast from a mesenchymal stem cell (MSC) population, a process that has been shown to be mechanically regulated. However, the mechanisms by which a biophysical stimulus can induce a change in biochemical signaling, mechanotransduction, is poorly understood. As a precursor to loading-induced bone formation, deciphering the molecular mechanisms of MSC osteogenesis is a critical step in developing novel anabolic therapies. Therefore, in this study we characterize the expression of the mechanosensitive calcium channel Transient Receptor Potential subfamily V member 4 (TRPV4) in MSCs and demonstrate that TRPV4 localizes to areas of high strain, specifically the primary cilium. We demonstrate that TRPV4 is required for MSC mechanotransduction, mediating oscillatory fluid shear induced calcium signaling and early osteogenic gene expression. Furthermore, we demonstrate that TRPV4 can be activated pharmacologically eliciting a response that mirrors that seen with mechanical stimulation. Lastly, we show that TRPV4 localization to the primary cilium is functionally significant, with MSCs with defective primary cilia exhibiting an inhibited osteogenic response to TRPV4 activation. Collectively, this data demonstrates a novel mechanism of stem cell mechanotransduction, which can be targeted therapeutically, and further highlights the critical role of the primary cilium in MSC biology.