Cellular and molecular pathways that lead to progression and regression of renal fibrogenesis

Renal fibrosis is a common consequence and often a central feature of all the progressive renal diseases that lead to end-stage renal failure. In comparison to wound healing, during kidney fibrosis the length of the post-inflammatory phase often exceeds and continues unchecked resulting in scar formation. Infiltrating immune cells and a heterogeneous colony of interstitial cells derived from a variety of cellular origins such as resident mesenchymal cells, tubular epithelial cells, circulating fibrocytes, and bone marrow derived stem cells, communicate with each other and with inflamed and surviving parenchymal cells via a network of cytokines and adhesion molecules to populate the renal tubulointerstitial space during early fibrogenesis. Such fibroblasts subsequently secrete abundant extracellular matrix to achieve architectural remodeling in parallel with functional deterioration. Renal fibrosis is a dominant determinant of the clinical outcome of patients and yet for the most part, current therapies are ineffective or only marginally effective. This review highlights recent advances in our understanding of the cellular and molecular events leading to the progression of renal fibrosis.