Organogenesis in a defined medium supplemented with transferrin.

Organ culture of embryonic tissues provides means to analyse complex morphogenetic processes. Differentiation of the metanephrogenic mesenchyme into the epithelium of the nephron is know to occur in vitro. We have now formulated a synthetic medium which permits induction of the nephrogenic mesenchyme and its differentiation into the main segments of the nephron, the proximal and the distal tubules and primitive glomeruli. The medium consists of a basal medium supplemented with a single factor, transferrin. In the absence of transferrin differentiation failed to occur. None of the other factors tested (EGF, FGF, insulin, Pedersen fetuin) could replace transferrin.