RESUMEN
Neointimal formation in atheromatous blood vessels is associated with both growth factor-induced differentiation of smooth muscle cells and endothelial-to-mesenchymal transition. Transforming growth factor beta (TGFß)-signaling is well known to play a critical role in the regulation of vessel remodeling as well as in atherosclerosis and restenosis. Here, we investigated the role of TGFß1 and N-cadherin on the differentiation and migration of human vascular smooth muscle cells (VSMC). TGFß1-treatment of cultured VSMC reduced their migratory activity as determined in cell migration assays. This reduced migration correlated with increased concentration of N-cadherin on mRNA and protein level. The TGFß1-induced increase of N-cadherin was sensitive against pharmacological inhibition of the ALK5 TGFß receptor and was accompanied by TGFß1-induced expression of the transcription factor snail1. Activation of N-cadherin by using a HAV-containing peptide of N-cadherin also decreased the migration of VSMC. N-cadherin-mediated suppression of VSMC migration was associated with an increased activity of RhoA, which is activated by binding of the HAV peptide to N-cadherin. Our results demonstrate that TGFß1 induces the differentiation of primary VSMC cells by Smad2/3-dependent up-regulation of the transcription factor snail1 and subsequently of N-cadherin, leading to inhibition of VSMC migration by RhoA-dependent modulation of the actin cytoskeleton.
Asunto(s)
Cadherinas/metabolismo , Movimiento Celular/efectos de los fármacos , Músculo Liso Vascular/citología , Músculo Liso Vascular/metabolismo , Factor de Crecimiento Transformador beta/farmacología , Cadherinas/genética , Adhesión Celular/efectos de los fármacos , Adhesión Celular/genética , Línea Celular , Movimiento Celular/genética , Electroforesis en Gel de Poliacrilamida , Humanos , Inmunohistoquímica , Músculo Liso Vascular/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteínas de Unión al GTP rho/genética , Proteínas de Unión al GTP rho/metabolismoRESUMEN
INTRODUCTION: Insulin-like growth factors (IGFs) are known to play an important role in atherogenesis. The aim of our study was to assess the local expression of IGF-related peptides in stenosed hemodialysis fistulas and compare these with their respective serum levels. METHODS: We investigated 15 stenosed vein segments of primary arteriovenous fistulas, 29 non-stenosed control vein segments from uremic patients and 15 non-stenosed control saphenous vein segments. Immunohistochemistry was performed for IGF-I, insulin, IGF-binding proteins (IGFBPs)-1, -2, -3 and -4, the acid labile subunit (ALS) and type 1 IGF-receptor (IGF-R). Serum levels were measured by specific radioimmunoassays. RESULTS: Compared to both control groups, a significantly higher expression of the following IGF-related peptides was seen in the stenotic (neo)intima: IGF-I, IGFBP-1, -2, -3, -4 and IGF-R; in the stenotic media: IGF-I and IGFBP-3 and in the endothelium of stenotic fistulas: IGF-I (all p<0.05). Staining against ALS and insulin was negative in all vessels. Serum IGF-I levels did not differ. Serum levels of IGFBP-1, -2, -3 and -4 were significantly higher in patients with renal disease (all p<0.05). There were no correlations between local and systemic IGF-related peptide levels. There were correlations of neointimal expression of IGF-I, IGFBP-1, -2, -3, -4 and IGF-R with both hypercellularity and the presence of inflammatory cells (p<0.05). CONCLUSION: In the stenotic arteriovenous fistula of hemodialysis patients, expression of the peptides IGF-I, IGFBP-1, -2, -3, -4 and IGF-R was significantly increased and showed a positive correlation with neointimal inflammation and hypercellularity (all p<0.05). IGF-related peptides are most likely synthesized locally and might be involved in the initiation and/or progression of neointimal thickening of primary arteriovenous fistulas.