[Epithelial-mesenchymal transition (EMT) plays a central role in physiological and pathological processes of embryogenesis, carcinogenesis and tissue fibrosis. During EMT epithelial cells may transform to myofibroblasts, which are the effector cells of fibrosis. In our summary the process of EMT and its medical importance will be reviewed in relation to renal fibrosis. Regardless of the initiating cause the final common mechanism of organ fibrosis is similar in the different chronic renal diseases. It always involves major inflammatory responses, however the molecular mechanisms involved are still elusive. The EMT now takes centre stage as the point of convergence between inflammation and the progression of degenerative fibrotic diseases. Understanding the pathomechanism of EMT and the significance of signalling pathways involved in this process may lead to a new therapeutic approach in the treatment of chronic renal diseases.]

[There are about a quarter of million patients who need chronic renal replacement therapy in Europe, and the estimated number of patients with chronic kidney disease is about tenfold higher. Interestingly, regardless of the initiating cause the mechanism of fibrosis is similar to each other in the different chronic kidney diseases. In general, the damaged glomerular or tubular cells release danger signals and produce chemotactic stimuli, which trigger the rapid recruitment of leukocytes. The infiltrating immune cells and the damaged renal cells then produce high levels of proinflammatory cytokines, growth factors, chemokines and adhesion molecules which contribute to glomerular/tubular injury, accumulation of further leukocytes and myofibroblasts, which are the effector cells of renal fibrosis. However the origin of myofibroblasts is still controversial. Recent hypotheses suggest that they are originated from different renal cells, such as epithelial and endothelial cells, pericytes or bone marrow derived fibrocytes. The myofibroblasts thus generated serve as key cellular mediators of renal fibrosis. Myofibroblasts have migratory capacity, are resistant to apoptosis, produce several growth factors and cytokines and according to our present knowledge these cells are the main source of collagen-I and -III rich extracellular matrix in the fibrous tissue. Organ fibrosis is characterized with excessive deposition of extracellular matrix leading to glomerular sclerosis and renal tubulointerstitial fibrosis. The excessive deposition of fibrous tissue replaces healthy kidney tissue; nephrons disappear and kidney function declines gradually. In this article the knowledge is summarized on the molecular changes leading to the generation of renal myofibroblasts.]

[The high incidence of chronic kidney diseases and, regardless of the etiology, their progression to renal fibrosis with end-stage renal failure rise the urgent need to reveal the pathomechanisms. As the disease leads to complex changes in the body, it is essential to use in vivo model systems for these investigations. Animal experiments choosing the appropriate model system helps to develop more sensitive early diagnostic markers and new therapeutic approaches. Several animal experimental model descriptions can be found in the literature, which mimic specific or more general human diseases in order to help the better understanding of the pathomechanisms. Using these model systems, we are able to analyze the detailed pathophysiology of glomerulonephritis, tubulointerstitial fibrosis, glomerular scarring or generalized renal fibrosis. The most commonly used model systems for renal fibrosis are presented and discussed.]

[The souvenirs of Hans Selye as a teacher of graduate and post graduate students are presented and discussed. The main aim of his teaching was to orient the student toward importance and originality of findings.]