Flow Shear Stress Enhances the Proliferative Potential of Cultured Radial Glial Cells Possibly Via an Activation of Mechanosensitive Calcium Channel

Radial glial cells (RGCs) which function as neural stem cells are known to be non-excitable and their proliferation depends on the intracellular calcium (Ca2+) level. It has been well established that Inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release and Ca2+ entry through various Ca2+ channels are involved in the proliferation of RGCs. Furthermore, RGCs line the ventricular wall and are exposed to a shear stress due to a physical contact with the cerebrospinal fluid (CSF). However, little is known about how the Ca2+ entry through mechanosensitive ion channels affects the proliferation of RGCs. Hence, we hypothesized that shear stress due to a flow of CSF boosts the proliferative potential of RGCs possibly via an activation of mechanosensitive Ca2+ channel during the embryonic brain development. Here, we developed a new microfluidic two-dimensional culture system to establish a link between the flow shear stress and the proliferative activity of cultured RGCs. Using this microfluidic device, we successfully visualized the artificial CSF and RGCs in direct contact and found a significant enhancement of proliferative capacity of RGCs in response to increased shear stress. To determine if there are any mechanosensitive ion channels involved, a mechanical stimulation by poking was given to individual RGCs. We found that a poking on radial glial cell induced an increase in intracellular Ca2+ level, which disappeared under the extracellular Ca2+-free condition. Our results suggest that the shear stress by CSF flow possibly activates mechanosensitive Ca2+ channels, which gives rise to a Ca2+ entry which enhances the proliferative capacity of RGCs.