title: Hypoxia inhibits nephrogenesis through paracrine Vegfa despite the ability to enhance tubulogenesis.
abstract: Reduced nephron number predisposes to hypertension and kidney disease. Interaction of the branching ureteric bud and surrounding mesenchymal cells determines nephron number. Since oxygen supply may be critical for intrauterine development, we tested whether hypoxia and hypoxia-inducible factor-1α (HIF-1α) influence nephrogenesis. We found that HIF-1α is required for branching of MDCK cells. In addition, culture of metanephric mouse kidneys with ureteric bud cell-specific stabilization or knockout of HIF-1α revealed a positive impact of HIF-1α on nephrogenesis. In contrast, widespread stabilization of HIF-1α in metanephric kidneys through hypoxia or HIF stabilizers impaired nephrogenesis, and pharmacological HIF inhibition enhanced nephrogenesis. Several lines of evidence suggest an inhibitory effect through the hypoxia response of mesenchymal cells. HIF-1α was expressed in mesenchymal cells during nephrogenesis. Expression of the anti-branching factors Bmp4 and Vegfa, secreted by mesenchymal cells, was increased upon HIF stabilization. The conditioned medium from hypoxic metanephric kidneys inhibited MDCK branching, which was partially rescued by Vegfa antibodies. Thus, the effect of HIF-1α on nephrogenesis appears context dependent. While HIF-1α in the ureteric bud is of importance for proper branching morphogenesis, the net effect of hypoxia-induced HIF activation in the embryonic kidney appears to be mesenchymal cell-dependent inhibition of ureter branching.
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Schley
authors.affiliation: Department of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Scholz
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Andre
authors.initials: A
authors.lastname: Kraus
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hackenbeck
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Klanke
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Willam
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wiesener
authors.affiliation: Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Heinze
authors.affiliation: Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Burzlaff
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Eckardt
authors.affiliation: Department of Nephrology and Hypertension, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: Bjoern
authors.initials: B
authors.lastname: Buchholz