Molecular signatures and markers of erythropoietin competence in the kidney

About This Grant

Anemia is common in the elderly and a risk factor for adverse cardiovascular events, cognitive decline and poor quality of life. It is often due to underlying inflammation or chronic kidney disease (CKD). Major etiological factors in the pathogenesis of anemia in CKD or inflammation are relative erythropoietin (EPO) deficiency and dysregulation of iron metabolism. Relative EPO deficiency refers to the reduced ability of the diseased or inflamed kidney to produce adequate amounts of EPO in response to hypoxia or anemia. EPO is a glycoprotein hormone and essential for erythropoiesis, with the kidney being its main production site under most physiological conditions. In the kidney, EPO is produced by interstitial perivascular fibroblast-like cells and pericytes, which, under injury conditions, can transdifferentiate into fibrosis-promoting, collagen- producing myofibroblasts, thus linking EPO deficiency to kidney fibrogenesis. The major regulator of EPO synthesis in the kidney is hypoxia-inducible factor (HIF)-2, a heterodimeric transcription factor that consists of an oxygen-regulated alpha-subunit and a constitutively expressed beta-subunit. HIF-2 activity is controlled by 2-oxoglutarate-dependent dioxygenases, which function as the oxygen sensors of the HIF pathway. Despite the significant advances in understanding oxygen-dependent regulation of EPO transcription, relatively little is known about the molecular identity of EPO- competent renal interstitial cells and the molecular mechanisms that lead to EPO-deficiency associated with CKD. Under Aim 1 of this exploratory grant, we use single-cell RNA sequencing in rats to characterize the molecular signatures and pathways that inform about EPO competence of renal interstitial perivascular cells in normal kidneys and in a model of chronic kidney injury and inflammation induced by adenine. These studies aim to identify and validate molecular markers and pathways that differentiate renal interstitial cells with EPO-producing capacity from cells that do not produce EPO. Under Aim 2, we leverage high-definition spatial transcriptomics in mice to map EPO and associated HIF-induced transcriptomic responses in healthy and injured kidneys.