Eccrine sweat glands: Expression of transforming growth factor-beta and bone morphogenetic protein type I receptors and their intracellular signalling Smad proteins

The transforming growth factor-beta superfamily is thought to be involved i n the regulation and control of growth and differentiation. These growth fa ctors signal through transmembrane serine/threonine kinase receptors, The a ctivation of type I receptor kinase phosphorylates a family of intracellula r signalling proteins called Smads, In the present study, we wanted to loca lize type I and type II receptors and Smad proteins in human eccrine sweat glands. Expression of transforming growth factor-beta type I receptor was r estricted to myoepithelial cells only, whereas bone morphogenetic protein r eceptor IA was found selectively within the duct epithelium of both the der mal portion and the acrosyringium, Bone morphogenetic protein receptor IB a ntibody gave a faint staining of secretory epithelium and myoepithelial cel ls, Smad proteins were identified in different parts of the eccrine sweat g land apparatus. In particular, Smad 1 and Smad 3 were localized within myoe pithelial cells, whereas coils were stained weakly for Smad 1 and Smad 3, S mad 3 protein was also expressed by the duct epithelium, Smad 2, Smad 4, Sm ad 5, Smad 6 and Smad 7 were not identified in eccrine sweat gland epitheli a, Our data provide evidence for transforming growth factor-beta/bone morph ogenetic protein signalling in the eccrine sweat gland and the selective ex pression of Smad proteins. Myoepithelial cells and duct cells have been ide ntified as major targets of the transforming growth factor-beta pathway. Po ssible functions are growth inhibition and control of myoepithelial differe ntiation.