Abstract 18427: Dysregulation of the miR143/145 Cluster and Mir133a During Progression of Vein Graft Neointima Formation
Background: The late failure of autologus human saphenous vein bypass grafts due to neointimal formation carries a major clinical burden. Therefore, identifying novel strategies to prevent neointimal formation is desirable. The principal cell type responsible for the neointimal lesion are smooth muscle cells (SMC), which are activated in response to injury leading to accelerated rates of proliferation and migration. MicroRNAs (miRs) are small non-coding RNAs that play an important role in modulating vascular phenotypes through regulation of gene expression.
Methods and results: We undertook a microarray profiling approach to identify miRs which may be modulated during the development of neointimal lesions in the setting of vein graft disease. Profiling experiments revealed several miRs (miR133a, miR143 and miR145) which have been previously implicated in SMC de-differentiation and activation. These results were validated by q-PCR which demonstrated that miR-133a and miR-143 were down-regulated 4-5 fold and miR-145 was down regulated between 7-11 fold in the human saphenous vein ex vivo culture model and the porcine interposition model of vein graft neoinitma formation (both models, n=6). Treatment of isolated SMC harvested from human saphenous veins with TGF-β1 (10ng/ml), to induce differentiation to a more quiescent and contractile phenotype, up-regulated miR-145 by 2.2+0.2 fold (n=3) but miR-133a levels were unaffected. A wounding assay was utilised to determine whether miR levels were elevated during SMC migration. Following quiescence, SMC were subjected to multiple scratch wounds and placed in serum to induce migration for a period of 16 hours. Quantification of miR-145 levels in migrating SMC revealed a 5-fold reduction in miR-145 levels following induction of migration.
Conclusion: These results suggest that the miR-143/145 cluster plays an important role in the dedifferentiation of SMCs during neointimal formation following vein grafting. We also demonstrate that TGF-β1, an established modulator of SMC differentiation and proliferation, increased miR-143/145 levels suggesting that elevation of miR-143/145 in vein grafts may prevent SMC de-differentiation and elevated rates of SMC proliferation and migration.
- © 2012 by American Heart Association, Inc.