Combination of keratins and alpha-smooth muscle actin distinguishes secretory coils from ducts of eccrine sweat glands

Eccrine sweat glands are comprised of secretory coils and ducts, which are distinct in morphology and function. To better understand the roles of the two parts in development, homeostasis, wound repair and regeneration of eccrine sweat glands, we must distinguish between them. In this study, the localization of keratins and alpha-SMA in human eccrine sweat glands was examined by immunofluorescence staining. Based on the differential localization of keratins and alpha-SMA in different cell types, four pairs of antibodies (K5/K7, K5/alpha-SMA, K14/K7 and K14/alpha-SMA) were used to differentiate secretory coils from ducts by double-immunofluorescence staining. Immunofluorescence staining showed that myoepithelial cells of secretory coils expressed K5, K14 and alpha-SMA, whereas secretory cells of secretory coils expressed K7, K8, K15, K18 and K19. Ductal cells expressed K5, K8, K14 and K19. Double-staining showed that the secretory coils were K5+/K7+, K5+/alpha-SMA+, K14+/K7+ and K14+/alpha-SMA+, whereas ducts were K5+/K7−, K5+/alpha-SMA−, K14+/K7− and K14+/alpha-SMA−. In conclusion, by combining use of keratins and alpha-SMA antibodies, secretory coils can be easily differentiated from ducts in morphology.