Urinary excretion of S100A8/A9 also increased in AKI patients, and the levels were significantly correlated with the severity of kidney tissue injury and the amount of kidney S100A8/A9 expression, but were not related to the S100A8/A9 levels in the plasma (Figure 6D–F), indicating the kidney tissue origin of S100A8/A9 in the urine instead of being solely filtered from the blood. This evidence concerns the gene S100A8 and acute kidney injury.