Renal fibrosis: New insights into the pathogenesis and therapeutics

Renal fibrosis is the inevitable consequence of an excessive accumulation of extracellular matrix that occurs in virtually every type of chronic kidney disease. The pathogenesis of renal fibrosis is a progressive process that ultimately leads to end-stage renal failure, a devastating disorder that requires dialysis or kidney transplantation. In a simplistic view, renal fibrosis represents a failed wound-healing process of the kidney tissue after chronic, sustained injury. Several cellular pathways, including mesangial and fibroblast activation as well as tubular epithelial - mesenchymal transition, have been identified as the major avenues for the generation of the matrix-producing cells in diseased conditions. Among the many fibrogenic factors that regulate renal fibrotic process, transforming growth factor-beta (TGF-beta) is one that plays a central role. Although defective matrix degradation may contribute to tissue scarring, the exact action and mechanisms of the matrix-degrading enzymes in the injured kidney have become increasingly complicated. Recent discoveries on endogenous antifibrotic factors have evolved novel strategies aimed at antagonizing the fibrogenic action of TGF-beta/Smad signaling. Many therapeutic interventions appear effective in animal models; however, translation of these promising results into humans in the clinical setting remains a daunting task. This mini-review attempts to highlight the recent progress in our understanding of the cellular and molecular pathways leading to renal fibrosis, and discusses the challenges and opportunities in developing therapeutic strategies.