Three-dimensional organization of the developing vasculature of the kidney

Kidney function depends on a well-developed vascular system. Any impairment of the blood supply disturbs the integrity and function of the organ. The differentiation of renal vessels has been investigation for many years, but little is known about the relationship between nephrogenesis and vessel development. In the present work the spatial organization of the differentiating vessels was analyzed in precisely oriented tissue sections and in optical sections acquired by laser scan microscopy. Developing vessels as well as small capillaries were visualized with two endothelium-detecting antibodies. Small vessels running in parallel towards the organ capsule were detected in numerous cortico-medullary-oriented tissue sections. Cross-sections of the nephrogenic zone showed a regularly arranged network, which was composed of cells detected by both monoclonal antibodies. Parts of this network were localized in regions of the nephrogenic zone which have been assumed to be free of vessels or vessel-like structures for a long time. These results were confirmed by the laser-scan-microscopic analysis of complete cortex explants. The extraordinarily regular arrangement of the endothelial network in the nephrogenic zone allowed us to reconstruct the developing vascular system. The results presented here underline the close relationship between nephrogenesis and vessel development.