title: A monoclonal antibody against alpha-smooth muscle actin: a new probe for smooth muscle differentiation.
abstract: A monoclonal antibody (anti-alpha sm-1) recognizing exclusively alpha-smooth muscle actin was selected and characterized after immunization of BALB/c mice with the NH2-terminal synthetic decapeptide of alpha-smooth muscle actin coupled to keyhole limpet hemocyanin. Anti-alpha sm-1 helped in distinguishing smooth muscle cells from fibroblasts in mixed cultures such as rat dermal fibroblasts and chicken embryo fibroblasts. In the aortic media, it recognized a hitherto unknown population of cells negative for alpha-smooth muscle actin and for desmin. In 5-d-old rats, this population is about half of the medial cells and becomes only 8 +/- 5% in 6-wk-old animals. In cultures of rat aortic media SMCs, there is a progressive increase of this cell population together with a progressive decrease in the number of alpha-smooth muscle actin-containing stress fibers per cell. Double immunofluorescent studies carried out with anti-alpha sm-1 and anti-desmin antibodies in several organs revealed a heterogeneity of stromal cells. Desmin-negative, alpha-smooth muscle actin-positive cells were found in the rat intestinal muscularis mucosae and in the dermis around hair follicles. Moreover, desmin-positive, alpha-smooth muscle actin-negative cells were identified in the intestinal submucosa, rat testis interstitium, and uterine stroma. alpha-Smooth muscle actin was also found in myoepithelial cells of mammary and salivary glands, which are known to express cytokeratins. Finally, alpha-smooth muscle actin is present in stromal cells of mammary carcinomas, previously considered fibroblastic in nature. Thus, anti-alpha sm-1 antibody appears to be a powerful probe in the study of smooth muscle differentiation in normal and pathological conditions.
mesh_terms: D000199:Actins / Q000276:immunology* / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D001011:Aorta / Q000166:cytology; D003893:Desmin / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008321:Mammary Glands, Animal / Q000378:metabolism; D009130:Muscle, Smooth / Q000276:immunology* / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D012469:Salivary Glands / Q000378:metabolism
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D003893:Desmin