Myofibroblasts in the mucosal layer of the uterine tube

Uterine tubes from cow, sheep, horse, pig, dog, cat, rabbit, and guinea pig were examined immunohistochemically for presence and distribution of contr actile cells in the mucosal lamina propria. We tested for the presence of a lpha-smooth muscle actin, tropomyosin, desmin, smooth muscle myosin (heavy chain) and cytoskeletal proteins vimentin and cytokeratin. Immunostaining f or alpha-smooth muscle actin showed two distribution patterns: either posit ive cells were freely dispersed in the mucosal lamina propria or a distinct subepithelial layer of positive cells was seen. The first distribution pat tern was found in the isthmic uterine tube segments of all animals examined . alpha-smooth muscle actin was colocalized with tropomyosin (all species), desmin (horse, sheep), and smooth muscle myosin (sheep, cow). All these ce lls were found reactive with anti-vimentin but not with anticytokeratin and therefore were classified as myofibroblasts. A distinct subepithelial laye r of alpha-actin and tropomyosin positive cells was seen in horse fimbriae. In other examined species alpha-smooth muscle actin immunoreactivity in th e subepithelial region was very weak. Contractile cells in the uterine tube mucosa were supposed to influence mucosal condition and motility, and ther efore to play a role in gamete transport.