Targeting Myofibroblasts in Model Systems of Fibrosis by an Artificial α-Smooth Muscle-Actin Promoter Hybrid

Myofibroblasts are the main cell types producing extracellular matrix proteins in a variety of fibrotic diseases. Therefore, they are useful targets for studies of intracellular communication and gene therapeutical approaches in scarring diseases. An artificial promoter containing the -702 bp regulatory sequence of the α-smooth muscle actin (SMA) gene linked to the first intron enhancer sequence of the β-actin gene and the β-globin intron-exon junction was constructed and tested for myofibroblast-dependent gene expression using the green fluorescent protein as a reporter. Reporter expression revealed myofibroblast-specific function in hepatic and renal myofibroblasts, in vitro. In addition, differentiation-dependent activation of the SMA-β-actin promoter hybrid was shown after induction of myofibroblastic features in mesangial cells by stretching treatment. Furthermore, wound healing experiments with SMA-β-actin promoter reporter mice demonstrated myofibroblast-specific action, in vivo. In conclusion, the -702 bp regulatory region of the SMA promoter linked to enhancing β-actin and β-globin sequences benefits from its small size and is suggested as a promising tool to target myofibroblasts as the crucial cell type in various scarring processes.