Alpha Smooth Muscle Actin (α-SMA), encoded by the ACTA2 gene, is a 42 kDa cytoskeletal protein belonging to the actin family. It is a key marker of smooth muscle cells and myofibroblasts, playing crucial roles in cell contraction, motility, and structural integrity. Unlike β- and γ-actin isoforms found in most cell types, α-SMA is specifically expressed in vascular smooth muscle cells, myoepithelial cells, and activated myofibroblasts during tissue repair or fibrosis.
Antibodies targeting α-SMA are widely used in research and diagnostics to identify smooth muscle-containing tissues and pathological conditions involving myofibroblast activation. In histopathology, these antibodies help distinguish vascular lesions, stromal tumors, and fibrotic processes. They are particularly valuable in cancer research for detecting cancer-associated fibroblasts (CAFs) in tumor microenvironments and assessing fibrotic progression in organs like the liver, lungs, and kidneys.
Common applications include immunohistochemistry, immunofluorescence, and Western blotting. Commercially available α-SMA antibodies are typically monoclonal (e.g., clone 1A4) or polyclonal, with species reactivity spanning human, mouse, and rat samples. Proper validation using knockout controls or siRNA-treated cells is essential due to potential cross-reactivity with other actin isoforms. Recent studies also utilize α-SMA antibodies in flow cytometry for characterizing mesenchymal cell populations and in mechanobiology research investigating cell-matrix interactions.