Translational Nephrology Renal fibrosis and the origin of the renal fibroblast

transition; fibrosis; progression Many studies have determined that the extent of tubulointerstitial involvement, particularly fibrosis, correlates better with renal function than glomerular changes do, thus, the extent of tubulointerstitial damage in any given renal biopsy has important implications for the renal prognosis of the patient (summarized in [1]). Tubulointerstitial fibrosis is characterized by the accumulation of extracellular matrix components including collagen types I, III, IV, proteoglycans and fibronectin. In recent years, much controversy has been created in the nephrology community regarding the origin of matrix-producing cells in the kidney. Several possibilities exist, including activation of resident interstitial fibroblasts, migratin