TGF-β1 activates RSC96 Schwann cells migration and invasion through MMP-2 and MMP-9 activities.

Following peripheral nerve injury, remnant Schwann cells adopt a migratory phenotype and remodel the extracellular matrix allowing axonal regrowth. Although much evidence has demonstrated that TGF-beta 1 promotes glioma cell motility and induces the expression of extracellular matrix proteins, the effects of TGF-beta 1 on Schwann cell migration has not yet been studied. We therefore investigated the cellular effects and the signal transduction pathways evoked by TGF-beta 1 in rattus norvegicus neuronal Schwann RSC96 cell. TGF-beta 1 significantly increased migration and invasion of Schwann cells assessed by the wound-healing assay and by cell invasion assay. TGF-beta 1-enhanced migration/invasion was blocked by inhibition of MMP-2 and MMP-9. Consistently, by real-time and western blot analyses, we demonstrated that TGF-beta 1 increased MMP-2 and MMP-9 mRNA and protein levels. TGF-beta 1 also increased MMPs activities in cell growth medium, as shown by gelatin zymography. The selective TGF-beta Type I receptor inhibitor SB431542 completely abrogated any effects by TGF-beta 1. Indeed, TGF-beta 1 Type I receptor activation provoked the cytosol-to-nucleus translocation of SMAD2 and SMAD3. SMAD2 knockdown by siRNA blocked MMP-2 induction and cell migration/invasion due to TGF-beta 1. TGF-beta 1 also provoked phosphorylation of MAPKs extracellular regulated kinase 1/2 and JNK1/2. Both MAPKs were upstream to p65/NF-kB inasmuch as both MAPKs' inhibitors PD98059 and SP600125 or their down-regulation by siRNA significantly blocked the TGF-beta 1-induced nuclear translocation of p65/NF-kB. In addition, p65/NF-kappa B siRNA knockdown inhibited the effects of TGF-beta 1 on both MMP-9 and cell migration/invasion. We conclude that TGF-beta 1 controls RSC96 Schwann cell migration and invasion through MMP-2 and MMP-9 activities. MMP-2 is controlled by SMAD2 whilst MMP-9 is controlled via an ERK1/2-JNK1/2-NF-kappa B dependent pathway.