Myofibroblast

A myofibroblast is a cell that is in between a fibroblast and a smooth muscle cell in phenotype. A myofibroblast is a cell that is in between a fibroblast and a smooth muscle cell in phenotype. Myofibroblasts are found subepithelially in many mucosal surfaces, for example, throughout almost the whole of the gastrointestinal and genitourinary tracts. Here they not only act as a regulator of the shape of the crypts and villi but also act as stem-niche cells in the intestinal crypts and as parts of atypical antigen-presenting cells. They have both support as well as paracrine function in most places. Myofibroblasts usually stain for the intermediate filament vimentin which is a general mesenchymal marker and 'alpha smooth muscle actin' (human gene = ACTA2) and for palladin, which is a cytoskeletal actin scaffold protein. They are positive for other smooth markers like intermediate filament type desmin in some tissues, but may be negative for desmin in some others. Similar heterogeneous positivity may exist for almost every smooth muscle marker except probably a few which are positive only in contractile smooth muscles like metavinculin and smoothelin. Some myofibroblasts (especially if they have a stellate form) may also be positive for GFAP.