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.

Hypoxia-inducible factor prolyl-4-hydroxylation in FOXD1 lineage cells is essential for normal kidney development

“…7, 30–33 Our genetic studies establish that the stromal PHD/HIF axis is a critical component of the renal hypoxia response system that regulates late nephrogenesis in a HIF-2-dependent manner. However, the developmental impact of HIF activation and the role of individual HIF transcription factors in other cell types is less clear.…”

“…Whereas mice with germline HIF-1α deletion die in utero between E9.5 and E11 precluding studies of renal development, 34, 35 hypoxia and wide-spread induction of HIF-1 signaling has been shown to restrict branching morphogenesis in vitro , possibly through the release of anti-branching factors. 33 Genetic HIF activation in UB cells specifically increased kidney size and number of glomeruli and very modestly enhanced UB branching, whereas UB-directed HIF-1α inactivation had the opposite effect, suggesting cell type-dependent functions of renal HIF signaling during development. 33 In contrast renal development was reported to be normal in a mixed-background strain of mice with germ line HIF-2α inactivation.…”

“…33 Genetic HIF activation in UB cells specifically increased kidney size and number of glomeruli and very modestly enhanced UB branching, whereas UB-directed HIF-1α inactivation had the opposite effect, suggesting cell type-dependent functions of renal HIF signaling during development. 33 In contrast renal development was reported to be normal in a mixed-background strain of mice with germ line HIF-2α inactivation. 20 Normal kidney development was also reported in a genetic model of renal epithelial HIF activation generated by Vhl gene deletion in SIX2 + epithelial progenitor cells.…”

Glucose promotes secretion-dependent renal cyst growth

“…RNA from embryonic kidneys was extracted as described previously [12]. RNA preparation from plMDCK cells was performed by the use of the peqGOLD TriFast (peqlab/ VWR International GmbH, Erlangen, Germany) according to the manufacturer's instructions.…”

Role of hypoxia during nephrogenesis

“…Furthermore, E13 rat kidney explants cultured in 5% O 2 for 96 hours had significantly more UB branching than kidneys cultured in 21% O 2 [49]. In contrast, a 2015 study found that E12 and E13 mouse kidney explants cultured in 21% O 2 had improved kidney growth and ureteric branching, while kidneys cultured in 5% and 1% O 2 were significantly smaller and had fewer ureteric branches [50]. This disparity may be attributed to different culturing conditions, since the same mouse strains were used.…”