Metanephric transforming growth factor-alpha is required for renal organogenesis in vitro

The role of transforming growth factor-alpha (TGF-alpha) in metanephric development was examined. Metanephroi were removed from 13-day-old rat embryos and grown in organ culture for up to 6 days using serum-free chemically defined media. During this time the metanephroi increased in size and morphological complexity. Messenger RNA for TGF-alpha was present in the renal anlage. Immunoreactive TGF-alpha was produced by metanephroi in vitro and released into culture media. TGF-alpha of metanephric origin coeluted with recombinant human 125I-TGF-alpha after high-performance liquid chromatography of media. In contrast, epidermal growth factor was not detectable. Levels of TGF-alpha were relatively constant during 4 days in culture and averaged approximately 10(-10) M. Growth of the metanephric anlage, arborization of the ureteric bud, and tubulogenesis within the metanephric blastema were inhibited by the addition of anti-TGF-alpha antibodies to organ cultures. These data demonstrate production of TGF-alpha by developing rat metanephroi in organ culture. The peptide is necessary for growth and development in vitro. Our findings suggest a necessary role for TGF-alpha of metanephric origin as a promoter of renal organogenesis in vivo.