ACTA2 and Familial Aortopathies: Creation and Validation of an Exploratory Cellular Model

The prevalence of hereditary aortic disease (HTAD), responsible for aneurysm or dissection, is estimated at 25%. Mutations in the ACTA2 gene represent the main cause of non-syndromic forms (10-21%). ACTA2 is expressed in vascular wall smooth muscle cells (VSMC) and encodes alpha actin (α-SMA). This actin isoform is in the majority in VSMCs and plays a key role in their contractile properties. The mutations are dominant-negative and lead, in a fibroblast model, to defects in the organisation of the actin cytoskeleton and to an increase in the migratory and proliferative potential of the cells. In vivo, VSCMs exist in a phenotypic continuum ranging from a quiescent differentiated contractile state to a so-called synthetic state in which cells are proliferative, synthesise extracellular matrix elements and exhibit enhanced migratory capabilities. To understand how ACTA2 mutations deregulate VSMC functions and steer them towards a synthetic phenotype, it is necessary to have a cellular model as close as possible to the affected tissue..