IGFBP7 and acute kidney injury: Tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) are both proteins that are involved in G1 cell cycle arrest and are released by renal tubular cells in response to cellular stress, and the combination of these two proteins in the urine has been validated for predicting the impending development of stage 2 or 3 AKI in critically ill patients [25].