Overview of injury and repair mechanisms. In the early stages of kidney injury, there is involvement of numerous inflammatory and immune modulators, including NF-κB, adhesion molecules such as ICAM and junctional adhesion molecule (JAM)-C, chemokines, neutrophils, and CD4+ T cells. Apoptotic molecules including p53, caspases, and tBid play a corresponding role along with these inflammatory factors. The late stages of injury involve ‘clean house’ molecules including mainly Tregs and macrophages in preparation for tissue recovery. If the insult is severe and/or prolonged it may progress to chronic kidney disease (CKD), driven by the production of free radicals and activated fibroblasts. Reparative mechanisms include angiogenic factors such as vascular endothelial growth factor (VEGF), anti-apoptotic factors like Netrin-1, and growth/proliferation factors such as Wingless (Wnt)/β-catenin, and transforming growth factor (TGF)-α and -β. Transcription factors including the Fox family, as well as Toll-like receptors (TLR)-2 and interleukin (IL)-6, -8 are involved in the influences of adult/renal progenitor stem cells and mesenchymal cells on repair.