Cell Characterization. Cultured rat coronary artery adventitia fibroblasts (LAD) and aortic vascular smooth cells (VSM) (positive control) stained for desmin, α-smooth muscle actin (α-SMA) and vimentin. LAD stained negative for desmin and αSMA and positive for vimentin, a fibroblast marker. VSM stained positive for all 3 proteins. Desmin and α-SMA are specific VSM markers.