Preliminary data from small clinical studies in critical care medicine have identified two urinary exosomal proteins as candidate biomarkers of acute kidney injury (AKI): (i) activating transcriptional factor 3 (ATF3), which is activated in models of ischemic reperfusion injury [61], and (ii) fetuin-A which is expressed in the cytoplasm of renal tubular cells, especially those detached from the basal lamina [62]. Here, ATF3 is linked to acute kidney injury.