Existence of a dense reticular meshwork surrounding the nephron inducer in neonatal rabbit kidney

While more and more humoral factors involved in nephrogenesis are being discovered, there is no detailed knowledge of the morphological structures at the interface of the nephron inducer and the surrounding mesenchyme. For that reason we examined this area in the cortex of neonatal rabbit kidneys by scanning electron-microscopical and transmission electron-microscopical techniques. Our interest was focused on the basal aspect of the collecting duct ampulla and the surrounding competent mesenchyme, where morphogenic signals are to be exchanged during nephron induction. Close contact between these two tissues involved in nephrogenesis is assumed to allow direct cellular contact or diffusion of soluble factors across a short distance. Our data, however, show the presence of a dense fibrillar meshwork around the collecting duct ampulla, spatially separating the inducer and the competent mesenchyme during nephron induction.