Promoting Tropoelastin Expression in Arterial and Venous Vascular Smooth Muscle Cells and Fibroblasts for Vascular Tissue Engineering

Elastin, critical for its structural and regulatory functions, is a missing link in vascular tissue engineering. Several elastin-inducting compounds have previously been reported, but their relative efficiency in promoting elastogenesis by adult arterial and venous vascular smooth muscle cells (VSMCs) and fibroblasts, four main vascular and elastogenic cells, has not been described. In addition to elasto-inductive substances, microRNA-29a was recently established as a potent post-transcriptional inhibitor of elastogenesis. Here, we explored if stimulating positive regulators or blocking inhibitors of elastogenesis could maximize elastin production. We tested whether the elasto-inducing compounds IGF-1, TGF-1, and minoxidil could indeed augment elastin production, and whether microRNA-29a antagonism could block elastin production in adult arterial and venous fibroblasts and VSMCs. The effects on elastin, lysyl oxidase, and fibrillin-1 mRNA expression levels and tropoelastin protein were determined. IGF-1 and minoxidil exerted little effect on tropoelastin mRNA expression levels in all cell types, while TGF-1 predominantly enhanced mRNA tropoelastin levels, but this mRNA increase did not impact tropoelastin protein abundance. In contrast, microRNA29a inhibition resulted in the upregulation of tropoelastin mRNA in all cell types, but most pronounced in venous VSMCs. Importantly, microRNA-29a-antagonism also enhanced lysyl oxidase and fibrillin-1 mRNA expression, and revealed a dose-dependent increase in tropoelastin protein expression in venous VSMCs. Our studies suggest that the elastogenic potential of microRNA-29a inhibition in vascular cells is superior to that of established elastin-stimulating compounds IGF-1, TGF-1, and minoxidil. Thus, microRNA-29a antagonism could serve as an attractive means of enhancing elastin synthesis in tissue-engineered blood vessels.