RGC-32 regulates TGF-β extracellular matrix production in multiple sclerosis.

Abstract Extracellular matrix (ECM) deposition in demyelinating multiple sclerosis (MS) lesions may impede axonal regeneration and modify immune responses. RGC-32 plays an important role in mediation of TGF-β downstream effects, but its role in ECM deposition and gliosis has not been investigated. To gain more insight into the role played by RGC-32 in gliosis, we examined the role of RGC-32 in mediation of ECM production and reactive astrocyte marker α-smooth muscle actin (α-SMA) expression. In MS lesions, collagen I, IV and V were found to be expressed by astrocytes which were also expressing RGC-32. In cultured astrocytes, α-SMA, collagens I, IV, V and fibronectin were significantly induced at 18 h of stimulation with TGF-β. Next, we silenced RGC-32 expression by transfecting astrocytes with siRGC-32 and compared the effect of this treatment to that of control siRNA. The RGC-32 siRNA effectively decreased the mRNA and protein RGC-32 expression by 90% when compared to astrocytes transfected with control siRNA. RGC-32 silencing resulted in a significant reduction in TGF-β- induced collagens I, IV, V and fibronectin expression. Using astrocytes isolated from RGC-32 knockout (KO) mice, we found that TGF-β- induced collagen IV and α-SMA expression were significantly reduced in RGC-32 KO when compared with wild type mice. Our data also indicate that RGC-32 plays an important role in the TGF-β-mediated induction of ECM and is also required for the transition of astrocytes to a reactive state. Therefore, RGC-32 may represent a new target for therapeutic intervention in MS.