Although PCs are considered the major kidney erythropoietin (EPO) producing cells through HIF-dependent gene transcription, and HIF stabilizers are emerging as promising treatments for anemia in chronic kidney disease (CKD) patients [5], PCs are also considered the major precursor cells of myofibroblasts in CKD and a source of fibrosis in the kidney [6]. Here, EPO is linked to chronic kidney disease.