Kidney epithelial cells.

Kidney tubules are an essential component of an organism's blood clearance mechanism, recovering essential metabolites from glomerular filtration by active transport. Tubules are subject to injury, usually as the result of ischemia-reperfusion events that damage the polarized tubular cell layer that coats the tubule basement membrane, causing dysfunction and necrosis that is often associated with acute renal failure. However, tubules are capable of self-repair, forming new proximal tubular cells to replace failing or necrotic cells. The origin of the progenitor cells that give rise to new tubular cells is unknown. At one extreme, it is possible that all or a fraction of tubular cells can undergo a form of dedifferentiation and subsequent mitosis to form new tubular cells, or alternatively, it is possible that tubular regeneration follows the stem cell/transit-amplifying cell paradigm described for more rapidly regenerating organ systems. Regardless of the mechanism employed to generate new tubular cells, human tubular cells are readily grown in primary cultures and can recapitulate many of the metabolic, endocrine, and immunological properties attributable to endogenous renal proximal tubules when engrafted into bioartificial devices.