Generation of renal tubules at the interface of an artificial interstitium. (a) SBA label visualizes in an individual sample tubules developing within an artificial interstitium consisting of a polyester fleece. (b) Scanning electron microscopy illuminates growth of renal tubules (T) between fibers of the polyester fleece (PF). (c) Semithin section after Richardson staining shows generated tubules in oblique and vertical view. (d) Transmission electron microscopy demonstrates that regenerating tubules contain a polarized epithelium. Neighboring cells are separated by a tight junctional complex (arrow head). Basal lamina (asterisk), lumen (arrow).