The renal (myo-)fibroblast: a heterogeneous group of cells

Renal fibrosis is a central pathological process in kidneys of patients with chronic kidney disease (CKD). Identification of effective treatments that halt or reverse fibrosis would be beneficial for most, if not all, CKD patients. Key to this is an understanding of fibrogenesis, including the principal responsible cells, the renal fibroblasts. It is in part due to their inconspicuous appearance that it was believed that there might not be much more to a fibroblast than a simple interstitial mesenchymal cell which makes up the organ stroma. The so-called 'renal fibroblasts' are a heterogeneous population of mesenchymal cells with various essential functions during kidney development and in adult life. Still, remarkable uncertainties exist in the nomenclature of renal mesenchymal cells—or renal fibroblasts—and molecular characterization remains poor. The embryonic origin of fibroblasts is unclear as well, although some studies point to a neural crest origin of these cells. The renal myofibroblasts appear de novo in renal fibrosis, originating from renal fibroblasts. Myofibroblasts most likely represent a stressed and dedifferentiated phenotype of fibroblasts. We have only just begun to appreciate that renal fibroblasts are anything but simple renal interstitial cells.