A potential gravity-sensing role of vascular smooth muscle cell glycocalyx in altered gravitational stimulation

Previously, we have shown that vascular smooth muscle cells (VSMCs) exhibit varied physiological responses when exposed to altered gravitational conditions. In the present study, we focused on elucidating whether the cell surface glycocalyx could be a potential gravity sensor. For this purpose, a roller culture apparatus was used with the intent to provide altered gravitational conditions to cultured rat aortic smooth muscle cells (RASMCs). Heparinase III (Hep.III) was applied to degrade cell surface heparan sulfate proteoglycans (HSPG) selectively. Sodium chlorate was used to suppress new synthesis of HSPG. Glycocalyx remodeling, nitric oxide synthase (NOS) activation, and F-actin expression induced by gravity alteration were assessed by flow cytometry, reverse transcription polymerase chain reaction (RT-PCR), and Western blot. Results indicate that the exposure of cultured RASMCs to altered gravitational conditions led to a reduction in cell surface HSPG content and the activation of NOS. It also down-regulated the expression of glypican-1, constitutive NOS (NOSI and NOSIII), and F-actin. On the other hand, Hep.III followed by sodium chlorate treatment of HSPG attenuated the aforementioned NOS and F-actin modulation under altered gravitational conditions. All these findings suggest that the glycocalyx, and HSPG in particular, may be an important sensor of gravitational changes. This may play an important role in the regulation of NOS activation, F-actin modulation, and HSPG remodeling in VSMCs.