Alpha-smooth muscle actin and other stromal markers in endometrial mucosa.

Stromal-epithelial interactions as expressed by alpha-smooth muscle actin (alpha-SM actin) collagen type IV, fibronectin, laminin and tenascin were studied in normal and pathological endometrial mucosa. There was complete or incomplete cuffing of scattered endometrial glands by alpha-SM actin mostly in the basal layer of endometrial mucosa and in dilated or cystic glands. Individual adenocarcinomatous glands were not encircled by alpha-SM actin-positive cells. Collagen type IV and laminin were found surrounding all glands irrespective of the presence of periglandular alpha-SM actin. Fibronectin was diffusely present in the stroma. Tenascin was identified, albeit not exclusively, in a periglandular location similar to that of alpha-SM actin. We conclude that the periglandular cells staining for alpha-SM actin, which were negative for cytokeratins, are probably myofibroblasts (MFs). Since this phenomenon was most commonly observed in dilated and cystic glands, we suggest that stromal cells immediately surrounding these glands may be subjected to mechanical or other stress resulting, as in other situations of tissue remodelling, in the development of MFs. This may also explain the appearance of tenascin in the same location. Thus, our finding may represent a further example of the local modulation of stromal cell phenotype, possibly under the action of micro-environmental factors.