Cysteine-rich protein 61 (Cyr61), a secreted matrix-associated heparin-binding protein, belongs to the "CCN" family. It regulates a broad spectrum of cellular activities, including cell adhesion, migration, proliferation, survival, differentiation, apoptosis, angiogenesis, and extracellular matrix production of multiple cell types. By the kidney ischemic/reperfusion injury animal model, Cyr61 gene was found to be rapidly up-regulated in the renal outer medulla. That portion of the kidney is corresponding to the area of marginally oxygenated under normal condition and most tubular injury following renal ischemic/reperfusion injury.18 Elevation of Cyr61 protein was detected in the kidney and also in urine following injury, making it a potential marker of AKI.