Different subpopulations of kidney interstitial cells produce erythropoietin and factors supporting tissue oxygenation in response to hypoxia in vivo

Abstract

Genetic induction of hypoxia signaling by deletion of the von Hippel-Lindau (Vhl) protein in mesenchymal PDGFR-β⁺ cells leads to abundant HIF-2 dependent erythropoietin (EPO) expression in the cortex and outer medulla of the kidney. This rather unique feature of kidney PDGFR-β⁺ cells promote questions about their special characteristics and general functional response to hypoxia. To address these issues, we characterized kidney PDGFR-β⁺ EPO expressing cells based on additional cell markers and their gene expression profile in response to hypoxia signaling induced by targeted deletion of Vhl or exposure to low oxygen and carbon monoxide respectively, and after unilateral ureteral obstruction. CD73⁺, Gli1⁺, tenascin C⁺ and interstitial SMMHC⁺ cells were identified as zonally distributed subpopulations of PDGFR-β⁺ cells. EPO expression could be induced by Vhl deletion in all PDGFR-β⁺ subpopulations. Under hypoxemic conditions, recruited EPO⁺ cells were mostly part of the CD73⁺ subpopulation. Besides EPO production, expression of adrenomedullin and regulator of G-protein signaling 4 was upregulated in PDGFR-β⁺ subpopulations in response to the different hypoxic stimuli. Thus, different kidney interstitial PDGFR-β⁺ subpopulations exist, capable of producing EPO in response to different stimuli. Activation of hypoxia signaling in these cells also induces factors likely contributing to improved kidney interstitial tissue oxygenation.

Keywords: PDGFR-β; erythropoietin; hypoxia; renal injury; renal interstitial cells; tissue oxygenation.