James A. Deane

Colony-stimulating factor-1 promotes kidney growth and repair via alteration of macrophage responses.

Colony-stimulating factor (CSF)-1 controls the survival, proliferation, and differentiation of macrophages, which are recognized as scavengers and agents of the innate and the acquired immune systems. Because of their plasticity, macrophages are endowed with many other essential roles during development and tissue homeostasis. We present evidence that CSF-1 plays an important trophic role in postnatal organ growth and kidney repair. Notably, the injection of CSF-1 postnatally enhanced kidney weight and volume and was associated with increased numbers of tissue macrophages. Moreover, CSF-1 promotes postnatal renal repair in mice after ischemia-reperfusion injury by recruiting and influencing macrophages toward a reparative state. CSF-1 treatment rapidly accelerated renal repair with tubular epithelial cell replacement, attenuation of interstitial fibrosis, and functional recovery. Analysis of macrophages from CSF-1-treated kidneys showed increased expression of insulin-like growth factor-1 and anti-inflammatory genes that are known CSF-1 targets. Taken together, these data suggest that CSF-1 is important in kidney growth and the promotion of endogenous repair and resolution of inflammatory injury.

Molecular mechanisms of leukocyte trafficking in T-cell-mediated skin inflammation: insights from intravital imaging

Infiltration of T cells is a key step in the pathogenesis of the inflammatory skin diseases atopic dermatitis, allergic contact dermatitis and psoriasis. Understanding the mechanisms of T cell recruitment to the skin is therefore of fundamental importance for the discovery and application of novel therapies for these conditions. Studies of both clinical samples and experimental models of skin inflammation have implicated specific adhesion molecules and chemokines in lymphocyte recruitment. In particular, recent studies using advanced in vivo imaging techniques have greatly increased our understanding of the kinetics and molecular basis of this process. In this review, we summarise the current understanding of the cellular immunology of antigen-driven dermal inflammation and the roles of adhesion molecules and chemokines. We focus on results obtained using intravital microscopy to examine the dermal microvasculature and interstitium to determine the mechanisms of T cell recruitment and migration in experimental models of T-cell-mediated skin inflammation.

The Contribution of Bone Marrow-Derived Cells to the Development of Renal Interstitial Fibrosis

Recent evidence suggests that bone marrow (BM)‐derived cells may integrate into the kidney, giving rise to functional renal cell types, including endothelial and epithelial cells and myofibroblasts. BM‐derived cells can contribute to repair of the renal peritubular capillary (PTC) network following acute ischemic injury. However, the cell fate and regulation of BM‐derived cells during the progression of chronic renal disease remains unclear. Using chimeric mice transplanted with enhanced green fluorescent protein (EGFP)‐expressing BM, we demonstrate that the number of BM‐derived myofibroblasts coincided with the development of fibrosis in a mouse adriamycin (ADR)‐induced nephrosis model of chronic, progressive renal fibrosis. Four weeks after ADR injection, increased numbers of BM‐derived myofibroblasts were observed in the interstitium of ADR‐injected mice. Six weeks after ADR injection, more than 30% of renal α‐smooth muscle actin (+) (α‐SMA+) interstitial myofibroblasts were derived from the BM. In addition, BM‐derived cells were observed to express the endothelial cell marker CD31 and the myofibroblast marker α‐SMA. Blockade of p38 mitogen‐activated protein kinase (MAPK) and transforming growth factor (TGF)‐β1/Smad2 signaling was found to protect BM‐derived PTC endothelial cells and inhibit the number of BM‐derived von Willebrand factor (vWF)(+)/EGFP(+)/α‐SMA(+) cells, EGFP(+)/α‐SMA(+) cells, and total α‐SMA(+) cells in ADR‐injected mice. Inhibition of the p38 MAPK and TGF‐β1/Smad signaling pathways enhanced PTC repair by decreasing endothelial‐myofibroblast transformation, leading to structural and functional renal recovery and the attenuation of renal interstitial fibrosis. Investigation of the signaling pathways that regulate the differentiation and survival of BM‐derived cells in a progressive disease setting is vital for the successful development of cell‐based therapies for renal repair.

Renal primary cilia lengthen after acute tubular necrosis.

Renal primary cilia are sensory antennas required for the maintenance of normal epithelial differentiation and proliferation in the kidney, but they also have a potential role in epithelial differentiation during renal injury and repair. In mice, tubular damage causes an increase in the length of renal cilia, which may modify their sensory sensitivity during repair. Here, we investigated whether the alteration of renal cilium length during renal injury is clinically relevant. Using biopsies of human renal transplants that suffered acute tubular necrosis during transplantation, we compared the length of renal primary cilia with renal function. Serial biopsies showed that acute tubular necrosis resulted in more than a doubling of cilium length throughout the nephron and collecting duct approximately 1 wk after injury. Allografts displayed a trend toward normalization of cilium length in later biopsies, and this correlated with functional recovery. A mouse model of renal ischemia-reperfusion confirmed the increase and subsequent regression of cilium length during renal repair, displaying complete normalization of cilium length within 6 wk of injury. These findings demonstrate that the length of renal cilia is a clinically relevant indicator of renal injury and repair.

A stereological study of the renal glomerular vasculature in the db/db mouse model of diabetic nephropathy

In diabetic nephropathy, glomerular hypertrophy is evident early in response to hyperglycaemia. Alterations of capillary length and vascular remodelling that may contribute to glomerular hypertrophy and the subsequent development of glomerulosclerosis remain unclear. The present study used the db/db mouse model of Type 2 diabetes to examine the glomerular microvascular changes apparent with long‐term diabetic complications. Unbiased stereological methods and high‐resolution light microscopy were used to estimate glomerular volume, and glomerular capillary dimensions including length and surface area in 7‐month‐old db/db diabetic mice and age‐matched db/m control mice. The db/db diabetic mice showed significant glomerular hypertrophy, corresponding with elevated blood glucose levels, and increased body weight and kidney weight, compared with db/m control mice. Glomerular enlargement in db/db mice was associated with increases in the surface area (5.387 ± 0.466 × 104 µm2 vs. 2.610 ± 0.287 × 104 µm2; P < 0.0005) and length (0.3343 ± 0.022 × 104 µm vs. 0.1549 ± 0.017 × 104 µm; P < 0.0001) of capillaries per glomerulus, compared with non‐diabetic mice. Stereological assessment at the electron microscopic level revealed increased glomerular volume density of mesangial cells and mesangial matrix, and thickening of the glomerular basement membrane in db/db mice. These results demonstrate that glomerular hypertrophy evident in advanced diabetic nephropathy in this model is associated with increased length and surface area of glomerular capillaries. The contribution of angiogenesis and vasculogenesis to the glomerular microvascular alterations in response to hyperglycaemia remain to be determined.

Adult stem cells in renal injury and repair.

SUMMARY:  There has been considerable focus on the ability of bone marrow‐derived cells to differentiate into non‐haematopoietic cells of various tissue lineages, including cells of the kidney. This growing evidence has led to a reconsideration of the source of cells contributing to renal repair following injury. The kidney has an inherent ability for recovery and regeneration following acute damage. It is thought that dedifferentiation of glomerular and tubular cells to a more embryonic/mesenchymal phenotype represent key processes for recovery in response to damage. However, there has been much contention as to the source of regenerating renal cells. The present review focuses on new aspects of the plasticity of intrinsic renal cells and their role in renal remodelling and scarring. Growing support also suggests that bone marrow‐derived cells have the ability to contribute to structural and functional repair following acute renal failure. Evidence for bone marrow cell engraftment in the repairing kidney leading to incorporation into a variety of tissue types is discussed. Because cell death and fibrosis is a common end‐point in a variety of acute and chronic renal nephropathies, the paradigm of stem cell plasticity may have important implications in the cellular and pathological mechanisms of renal injury and repair. A better understanding of the processes controlling extra‐renal cell engraftment and intrinsic renal cell differentiation may provide important clues for the development of new cell‐based therapies in the field of renal reparative medicine.

Alterations in renal cilium length during transient complete ureteral obstruction in the mouse

The renal cilium is a non‐motile sensory organelle that has been implicated in the control of epithelial phenotype in the kidney. The contribution of renal cilium defects to cystic kidney disease has been the subject of intense study. However, very little is known of the behaviour of this organelle during renal injury and repair. Here we investigate the distribution and dimensions of renal cilia in a mouse model of unilateral ureteral obstruction and reversal of ureteral obstruction. An approximate doubling in the length of renal cilia was observed throughout the nephron and collecting duct of the kidney after 10 days of unilateral ureteral obstruction. A normalization of cilium length was observed during the resolution of renal injury that occurs following the release of ureteral obstruction. Thus variations in the length of the renal cilium appear to be a previously unappreciated indicator of the status of renal injury and repair. Furthermore, increased cilium length following renal injury has implications for the specification of epithelial phenotype during repair of the renal tubule and duct.

BTB-ZF transcriptional regulator PLZF modifies chromatin to restrain inflammatory signaling programs

Significance Maintaining physiological balance is vital in the primary response to infectious and other stress stimuli to avert damaging inflammation. Delineation of the cell regulatory processes that control inflammatory processes better enable the development of informed strategies to treat associated pathologies. Toward this end, we identify that the promyelocytic leukemia zinc finger (PLZF) transcription factor limits pathogen-induced inflammation. PLZF stabilizes a repressor complex that encompasses histone deacetylase activity, which modifies the state of chromatin. This activity maintains homeostasis by decreasing the scale of induction of select immune response genes. In the absence of PLZF, the chromatin structure is altered, enabling active transcriptional complexes to immediately assemble on gene promoters, resulting in inordinate production of inflammatory cytokines. Inflammation is critical for host defense, but without appropriate control, it can cause chronic disease or even provoke fatal responses. Here we identify a mechanism that limits the inflammatory response. Probing the responses of macrophages to the key sensory Toll-like receptors, we identify that the Broad-complex, Tramtrack and Bric-a-brac/poxvirus and zinc finger (BTB/POZ), transcriptional regulator promyelocytic leukemia zinc finger (PLZF) limits the expression of inflammatory gene products. In accord with this finding, PLZF-deficient animals express higher levels of potent inflammatory cytokines and mount exaggerated inflammatory responses to infectious stimuli. Temporal quantitation of inflammatory gene transcripts shows increased gene induction in the absence of PLZF. Genome-wide analysis of histone modifications distinguish that PLZF establishes basal activity states of early response genes to maintain immune homeostasis and limit damaging inflammation. We show that PLZF stabilizes a corepressor complex that encompasses histone deacetylase activity to control chromatin. Together with our previous demonstration that PLZF promotes the antiviral response, these results suggest a strategy that could realize one of the major goals of immune therapy to retain immune resistance to pathogens while curbing damaging inflammation.

Blockade of p38 Mitogen-Activated Protein Kinase and TGF-β1/Smad Signaling Pathways Rescues Bone Marrow–Derived Peritubular Capillary Endothelial Cells in Adriamycin-Induced Nephrosis

The peritubular capillary (PTC) network is a component of the tubulointerstitium of the kidney with important roles in renal function and hemodynamics. Bone marrow (BM)-derived cells can contribute to repair of the renal PTC network after ischemic injury. However, the cell fate and the regulation of renal BM-derived cell engraftment in comparison with somatic cells during disease progression are unclear. This study characterized the time course and regulation of PTC endothelial cell injury in adriamycin (ADR)-induced nephropathy in mice, a model of chronic, irreversible, progressive renal disease. Enhanced green fluorescence protein-positive BM cells that coexpressed two endothelial cell markers, von Willebrand factor and CD31, were found to engraft into the PTC of chimeric ADR-injected mice in a time-dependent manner. The number of BM-derived PTC endothelial cells peaked 2 wk after ADR injection, then declined dramatically thereafter. In these mice, apoptosis was evident in BM-derived PTC endothelial cells, and the p38 mitogen-activated protein kinase (MAPK) and TGF-beta1/Smad signaling pathways were activated. Blocking both the p38 MAPK and TGF-beta1/Smad signaling pathways by administration of a p38 MAPK inhibitor (SB203580) and a TGF-beta receptor 1 inhibitor (ALK5I) to ADR-injected mice rescued BM-derived PTC endothelial cells from apoptosis, reduced the loss of PTC, and restored kidney function. Investigation into the signaling pathways that regulate the differentiation and survival of BM-derived cells that engraft into the kidney in the proinflammatory setting of progressive renal disease is vital for the successful development of cell-based therapies to promote renal regeneration and repair.

Polycystic kidney disease and the renal cilium (Review Article)

SUMMARY:  Polycystic kidney disease (PKD) is a common genetic condition characterized by the formation of fluid‐filled cysts in the kidney. Mutations affecting several genes are known to cause PKD and the protein products of most of these genes localize to an organelle called the renal cilium. Renal cilia are non‐motile, microtubule‐based projections located on the apical surface of the epithelial cells that form the tubules and ducts of the kidney. With the exception of intercalated cells, each epithelial cell bears a single non‐motile cilium that projects into the luminal space where it is thought to act as a flow sensor. The detection of fluid flow through the kidney by the renal cilium is hypothesized to regulate a number of pathways responsible for the maintenance of normal epithelial phenotype. Defects of the renal cilium lead to cyst formation, caused primarily by the dedifferentiation and over‐proliferation of epithelial cells. Here we discuss the role of renal cilia and the mechanisms by which defects of this organelle are thought to lead to PKD.