Electron and fluorescence microscopic investigations on composition and structure of the epithelial basement membrane of the human inferior nasal concha.

Light and electron microscopic as well as immunohistochemical investigations were performed on the basement membrane (BM) of the nasal mucosa from the inferior nasal conchae of 20 patients, aged 15-50 years. Two of the patients served as controls. Clinical disorders requiring the turbinectomies were hyperplastic nasal inferior conchae (17 patients) and immobile cilia syndrome (1 patient). In all cases light microscopy demonstrated a 10-15 microns thick homogeneous BM underneath an intact epithelium. Electron microscopic findings revealed a typical subepithelial basal lamina (BL). The remaining parts of the BM consisted of single, isolated 25-mm-thick collagenous fibrils. Only a few cells and small unmyelinated nerves occurred in this layer. Immunohistochemical investigations showed BL components (collagen type IV, laminin, nidogen and heparan sulfate proteoglycan) directly underneath the epithelium. Collagen types I, III, V, and VI could also be demonstrated immunohistochemically in the remaining parts of the BM. Collagen type VII was allocated to the anchor filaments beneath the BL. This special BM is presumed to contribute to mechanical stabilization of the epithelium. The significance of the BL and the subepithelial connective tissue for the behavior of the epithelium--e.g. direction of differentiation--are discussed.