Scarring of the glomerular and tubulointerstitial compartments is a hallmark of progressive kidney disease. Renal fibrosis involves a complex interplay between kidney cells, leukocytes and fibroblasts in which transforming growth factor-β (TGF-β) plays a key role. This eBook provides a comprehensive update on TGF-β signalling pathways and introduces a range of cellular and molecular mechanisms involved in renal fibrosis both upstream and downstream of TGF-β. The wide variety of potential new targets described herein bodes well for the future development of effective therapies to tackle the major clinical problem of progressive renal fibrosis.

This book systemically presents the latest research on renal fibrosis, covering all the major topics in the field, including the possible mechanisms, biomarkers, and strategies for prevention and treatment of chronic kidney disease (CKD). Due to its high prevalence, CKD represents a huge global economic and social burden. Irrespective of the initial causes, CKD progresses to end stage kidney disease (ESKD) due to renal fibrosis, which is characterized by glomerulosclerosis, tubule atrophy and atresia, and the excessive accumulation of extracellular matrix (ECM) in the kidney. Unfortunately, an estimated 1%-2% of the adult population living with CKD will need renal replacement therapy at some point as a result of ESKD. As such, strategies for preventing or slowing CKD progression to ESKD are of utmost importance, and studies aiming to understand the mechanisms of renal fibrosis have been the focus of intensive research. Recently, novel insights into the pathophysiological processes have furthered our understanding of the pathogenesis of renal fibrosis, and more importantly, promoted studies on the early diagnosis and treatment of CKD. This book draws lessons from the extensive, state-of-the-art research in this field, elaborating the new theories and new techniques to offer readers a detailed and comprehensive understanding of renal fibrosis and as well as inspiration for future research directions.

This publication provides a synopsis of the rapid progress made in the field of renal cell biology during the last decade, progress which has resulted in a better conceptual understanding of the cellular and molecular mechanisms of fibrotic renal disease. These developments have provided new therapeutic choices and led to the discovery of gene-based therapeutic options. The topics covered in this book have been carefully selected from the immense number of aspects of the disease to provide essential information on the molecular basis of renal fibrosis. Individual chapters discuss topics such as proteinuria and tubulointerstitial injury, the roles and regulation of TGF-beta, chemokines, oxidant stress, matrix remodeling, significance of renal expression of NF-kappa, and the potential impact of cell death in renal fibrosis.Written so as to present the complex information as simply as possible, this publication will be a very useful tool for general health professionals involved in the fields of immunology and cell biology, as well as for clinicians and researchers within the fields of nephrology, pathology and matrix biology.

Defining signaling and transcriptional regulators in a disease context is integral to the basic understanding of pathological functions of molecular pathways. Transforming growth factor-beta (TGF-ß) is a critical cytokine in wound healing and inflammatory responses, but over-activation contributes to pro-fibrotic disease processes. The goal of this work is to begin to define specific molecular facets of TGF-ß signaling in diabetic kidney fibrosis. State of the art mass spectrometric approaches were employed towards a label-free quantitative spectral counting method. These methods were applied in two contexts of TGF-ß signaling: 1) a murine model of diabetic kidney disease; and 2) a characterization of Notch4 intracellular domain-(ICD) protein complexes that we and others have shown to regulate TGF-ß signaling. In approach 1) kidney tubules were isolated from wild type and diabetic mice, proteins extracted were applied to 2-dimensional liquid chromatography fractionation followed by MS/MS (2D-LC-MS/MS) analysis and spectral counting. 476 significantly differentially abundant proteins were quantified. Of these, the SH2-SH3 adaptor GRAP (Grb2-related adaptor protein 2) was significantly elevated in diabetic tubule tissue. Findings were validated by immunohistochemistry and immunoblot. Upon further examination it was found that GRAP was elevated by TGF-ß stimulation and capable of enhancing a TGF-ß-based SMAD transcriptional reporter and enhanced secretion of pro-fibrotic matrix fibronectin in renal tubule cell cultures. These data indicate a novel role for GRAP in kidney tubule fibrosis via exacerbation of the TGF-ß pathway. Approach 2) employed affinity isolation of Notch4ICD followed by 2D-LC-MS/MS to define novel molecular partners imparting functional effects on Notch4 in proximal tubules. This approach identified the Elongin C (ElgC) ubiquitin ligase complex as a novel regulator of Notch4ICD in human proximal tubule cells. Further, ElgC regulates Notch4ICD transcriptional activity in a proteasome-dependent manner. Additionally, ElgC inhibits Notch4ICD dependent potentiation of SMAD-directed TGF-ß activity and fibronectin secretion. Co-expression of Notch4ICD and ElgC leads to the proteasome dependent degradation of a substantial portion of ectopic Notch4ICD. These findings indicate that ElgC mediates TGF-ß activity through regulating the expression levels and subsequent activity of Notch4ICD. In summary, proteomics approaches were utilized in an unbiased and targeted fashion to define novel mediators of TGF-ß signaling in kidney tubule cell biology and diabetic kidney disease.