Tools and Techniques to Map Glomerular Distribution and Nephron Function Using MRI

The nephrons are the primary functioning units of the kidney. Nephrons maintain filtration, blood pressure, and electrolyte homeostasis. Nephron number is fixed at birth, and human nephron number varies approximately ten-fold between individuals. Nephrons are damaged and lost due to injury, aging, or disease. A reduced or low nephron number likely predicts susceptibility to kidney disease and functional decline. However, there are no clinical tools to directly measure nephron number. A MRI-based tool using cationic ferritin (CF) as a targeted contrast agent can detect and map nephrons in 3D. Many studies have used cationic ferritin-enhanced MRI (CFE-MRI) to phenotype kidneys based on nephron number, measure kidney function in individual nephrons, and stage the development of pathology and nephron loss in models of human disease and in isolated human kidneys. CF has also been adapted for use with positron emission tomography (PET) to detect nephrons and quantify nephron loss in a clinically translatable manner. An improved understanding of the clinical course of nephron loss in kidney injury and disease may facilitate the development of earlier markers and interventions to slow the progression of kidney disease.