Pathogenesis Of Glomerular Diseases Research Articles

Profiling dendritic cells subsets in renal tissue of patients with crescentic glomerulonephritis.

Dendritic cells (DCs) have been speculated to be involved in the pathogenesis of glomerular diseases. However, the numbers and distribution of DC subsets in the kidneys of patients with crescentic glomerulonephritis (CrGN) have not been clearly elucidated. A total of 26 patients with biopsy-proven CrGN were enrolled. Indirect immunofluorescence staining was used to quantify DC subsets in renal specimens. Double staining of HLA with CD11C, BDCA2 and CD209 respectively was performed to detect DC subsets. The correlation between DC subsets infiltrated in the kidney and clinical and pathological parameters was investigated. DC subsets were predominantly present in the kidney interstitium, particularly in the peri-glomerular area. The numbers of CD11C+DCs, BDCA2+DCs and CD209+DCs increased in the patients with CrGN and varied among different types of CrGN. Though significant correlation between DC subsets and the percentage of crescents had not been identified, a notable increase in the number of CD11C+DCs were observed with the chronic development of crescents. Furthermore, patients with severe tubulointerstitial injury exhibited significantly more infiltrations of CD11C+DCs, BDCA2+DCs and CD209+DCs. Moreover, the numbers of CD11C+DCs and BDCA2+DCs were found to correlate with the level of serum C3. Patients with CrGN showed increased kidney infiltration of DC subsets, primarily localized in the renal interstitium and peri-glomerular region. The correlation between DC subsets and fibrosis of crescent and severe tubulointerstitial injury implied a potential involvement of DCs in the development of CrGN.

#2407 Multiomics analysis of isolated zebrafish glomeruli to unravel the impact of alternative splicing in glomerular diseases

Abstract Background and Aims Alternative splicing (AS) is a known key factor in gene regulation. There is evidence that changes in the alternative mRNA splicing can lead to the onset of various diseases. However, the potential role of AS in the pathogenesis of glomerular diseases has only been investigated to a very limited extent. In the past, the zebrafish larva (Danio rerio) has been established as an animal model for the in vivo investigation of kidney diseases, since the glomeruli of zebrafish larvae are genetically, molecularly, and functionally similar to those of mammals. As part of the Sys_CARE (Systems Medicine Investigation of AS in Cardiac and Renal Diseases) project, we wanted to identify specific AS events that might be involved in the development of focal segmental glomerulosclerosis (FSGS). Method For all experiments, the double transgenic strain [Tg (nphs2: GAL4-VP16); (UAS:Eco.nfsB-mCherry)] was used. At 4 dpf (days post fertilization), the zebrafish larvae were divided into two groups. The control group was treated with 0.1% dimethyl sulfoxide (DMSO) in E3 medium. To induce FSGS, zebrafish larvae were treated with 50 nM nifurpirinol (NFP) in 0.1% DMSO in E3 medium for 24 hours. Glomeruli were manually isolated at 5 and 6 dpf and analyzed together with lysates of whole larvae by LC-MS/MS and RNA-Seq. To identify AS events, RNA-Seq data were analyzed by MAJIQ, Multivariate Analysis of Transcript Splicing (rMATS), leafcutter, Whippet as well as IsoformSwitchAnalyzeR. Gene set enrichment analysis (GSEA) identified proteins and genes which were classified according to their related biological processes. Results Proteomics and transcriptomics showed significant differences in the glomerular protein and transcript levels between NFP-treated larvae and the control group. The abundance of the podocyte-specific protein nephrin as well as the podocin promotor-driven expression of the fluorescent dye mCherry was significantly reduced after NFP treatment confirming the onset of the injury. Subsequent analyses identified more than 1000 transcripts that were significantly differentially expressed, as well as several splicing events in the larvae with a FSGS-like damage. There was also a marked shift in isoform patterns in larvae with FSGS. Gene set enrichment analysis indicated an enrichment in the up-regulated transcripts and proteins involved in metabolic processes, especially those related to rRNA and ncRNA processing. Conversely, transcripts and proteins that were down-regulated showed significant clusters in catabolic processes, extracellular matrix, and cytoskeleton organization as well as in nephron and glomerulus development. Conclusion Using our zebrafish model, in-depth transcriptomics and proteomics analysis provided novel insights into the pathogenesis of podocyte-associated glomerular diseases. Data suggest, that pathological changes are accompanied by alternative splice events which might therefore be a new therapeutic approach in glomerular nephropathy.

DPP8/9 inhibition attenuates the TGF-β1-induced excessive deposition of extracellular matrix (ECM) in human mesangial cells via Smad and Akt signaling pathways

The pathogenesis of glomerular diseases is strongly influenced by abnormal extracellular matrix (ECM) deposition in mesangial cells. Dipeptidyl peptidase IV (DPPIV) enzyme family contains DPP8 and DPP9, which are involved in multiple diseases. However, the pathogenic roles of DPP8 and DPP9 in mesangial cells ECM deposition remain unclear. In this study, we observed that DPP8 and DPP9 were significantly increased in glomerular mesangial cells and podocytes in CKD patients compared with healthy individuals, and DPP9 levels were higher in the urine of IgA nephropathy (IgAN) patients than in control urine. Therefore, we further explored the mechanism of DPP8 and DPP9 in mesangial cells and revealed a significant increase in the expression of DPP8 and DPP9 in human mesangial cells (HMCs) following TGF-β1 stimulation. Silencing DPP8 and DPP9 by siRNAs alleviated the expression of ECM-related proteins including collagen Ⅲ, collagen Ⅳ, fibronectin, MMP2, in TGF-β1-treated HMCs. Furthermore, DPP8 siRNA and DPP9 siRNA inhibited TGF-β1-induced phosphorylation of Smad2 and Smad3, as well as the phosphorylation of Akt in HMCs. The findings suggested the inhibition of DPP8/9 may alleviate HMCs ECM deposition induced by TGF-β1 via suppressing TGF-β1/Smad and AKT signaling pathways.

Loss of MTX2 causes mitochondrial dysfunction, podocyte injury, nephrotic proteinuria and glomerulopathy in mice and patients.

Proteinuria is a common and important clinical manifestation of chronic kidney disease (CKD) and an independent risk factor for the progression of kidney disease. As a component of the glomerular filtration barrier (GFB), podocyte plays a key role in the pathogenesis of glomerular diseases and proteinuria. However, the pathophysiology of glomerular diseases associated with mitochondrial function is incompletely understood. Here, we identified three novel mutations in MTX2, encoding a membrane protein in mitochondria, associated with multisystem manifestations including nephrotic proteinuria and kidney injury in two Chinese patients. Conditional podocyte-specific Mtx2 knockout (Pod-Mtx2-KO) mice present a series of podocyte and glomerular abnormalities from 8 weeks to old age, including microalbuminuria, glomerular mesangial hyperplasia, fusion and effacement of foot process. MTX2 deficiency impaired podocyte functions in vitro, manifested by reductions of adhesion, migration and endocytosis, which were further restored by overexpression of MTX2. Moreover, MTX2 defects led to abnormal mitochondrial structure and dysfunction, evidenced with defects of complex I and III, increased production of reactive oxygen species (ROS), and decreased protein levels of Sam50-CHCHD3-Mitofilin axis in the mitochondrial intermembrane space bridging (MIB) complex which is responsible for maintaining mitochondrial cristae morphology. Collectively, these findings reveal that the normal expression of MTX2 in glomerulus plays an important role in the adhesion, migration, endocytosis, proliferation and other physiological functions of podocytes, which may be realized by maintaining the morphological structure and function of mitochondria. Abnormal expression of MTX2 can lead to mitochondrial dysfunction and structural abnormalities by Sam50-CHCHD3-Mitofilin axis in podocyte, which further induces podocyte injury, glomerular lesions and proteinuria.

Proteomic patterns in glomerular research, a laser capture microdissection and liquid chromatography-tandem mass spectrometry approach

Abstract Introduction: Molecular techniques have the potential to shed light on glomerular diseases that conventional renal pathology may be unable to reveal. The aim of this study was to investigate whether proteomic patterns of glomeruli obtained from kidney biopsies can differentiate between minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS) and control groups (CTR). Methods: 18 formalin-fixed, paraffin-embedded (FFPE) renal biopsies comprising three groups of samples (CTR=3, MCD=6, FSGS=9) were subjected to label-free quantitative mass spectrometry. Glomeruli were excised from FFPE renal biopsies by laser capture microdissection (LCM) and, to increase both yield and protein identifications, single-pot solid-phase-enhanced sample preparation (SP3) digest method was applied. The samples were analyzed by mass spectrometry based shotgun proteomics. Results: The proteome profiling resulted in the identification of a total of 723 proteins. Multivariate analysis provided several proteins important in the separation of the three groups. Pattern Hunter analysis revealed moderate and high correlation of proteins against CTR-FSGS-MCD or CTR-MCD-FSGS patterns. The most significant pathways involved were associated with nephrin family and cytoskeleton interactions, as well as laminin/extracellular matrix related proteins. Univariate analysis revealed 58 significant different proteins among the three groups. Signaling pathways of these proteins were also associated with nephrin family interactions and cytoskeleton organization. Conclusions: This study demonstrates that mass spectrometry-based shotgun proteomic analysis of LCM glomeruli yields reproducible and quantitative data capable of discriminating between different disease conditions. Differentially expressed proteins provide insights into pathogenesis of glomerular disease.

The Role of PKGIα and AMPK Signaling Interplay in the Regulation of Albumin Permeability in Cultured Rat Podocytes.

The permeability of the glomerular filtration barrier (GFB) is mainly regulated by podocytes and their foot processes. Protein kinase G type Iα (PKGIα) and adenosine monophosphate-dependent kinase (AMPK) affect the contractile apparatus of podocytes and influence the permeability of the GFB. Therefore, we studied the interplay between PKGIα and AMPK in cultured rat podocytes. The glomerular permeability to albumin and transmembrane FITC-albumin flux decreased in the presence of AMPK activators and increased in the presence of PKG activators. The knockdown of PKGIα or AMPK with small-interfering RNA (siRNA) revealed a mutual interaction between PKGIα and AMPK and influenced podocyte permeability to albumin. Moreover, PKGIα siRNA activated the AMPK-dependent signaling pathway. AMPKα2 siRNA increased basal levels of phosphorylated myosin phosphate target subunit 1 and decreased the phosphorylation of myosin light chain 2. Podocytes that were treated with AMPK or PKG activators were characterized by the different organization of actin filaments within the cell. Our findings suggest that mutual interactions between PKGIα and AMPKα2 regulate the contractile apparatus and permeability of the podocyte monolayer to albumin. Understanding this newly identified molecular mechanism in podocytes provides further insights into the pathogenesis of glomerular disease and novel therapeutic targets for glomerulopathies.

Angiotensin II Type 1 Receptor Antibodies Are Higher in Lupus Nephritis and Vasculitis than Other Glomerulonephritis Patients

Angiotensin II type 1 receptor (AT1R) antibodies are considered non-HLA (human leukocyte antigen) antibodies connected with humoral rejection after kidney transplantation. The role of AT1R antibodies in the pathogenesis of glomerular diseases and systemic vasculitis is unknown. We assessed the level of AT1R antibodies in 136 patients with different types of glomerulonephritis and systemic vasculitis and we observed kidney function and proteinuria, serum albumin and total protein levels for 2 years. The mean levels of AT1R antibodies were the following: 6.00 ± 1.31 U/ml in patients with membranous nephropathy (n = 18), 5.67 ± 1.31 U/ml with focal and segmental glomerulosclerosis (n = 25), 6.26 ± 2.25 U/ml with lupus nephropathy (n = 17), 10.60 ± 6.72 U/ml with IgA nephropathy (n = 14), 6.69 ± 2.52 U/ml with mesangial proliferative (non IgA) glomerulonephritis (n = 6), 6.63 ± 1.38 U/ml with systemic vasculitis (n = 56), including c-ANCA (anti-neutrophil cytoplasmic antibodies) vasculitis: 11.22 ± 10.78 U/ml (n = 40) and p-ANCA vasculitis: 12.65 ± 14.59 U/ml (n = 16). The mean AT1R antibodies level was higher in patients with lupus nephropathy and systemic vasculitis compared to glomerulonephritis groups. An inverse statistically significant correlation between AT1R antibodies and serum albumin (r = − 0.51) in membranous nephropathy group was also found. Prospective analysis of creatinine levels indicated an increase of creatinine levels during time among patients with higher AT1R antibodies levels in p-ANCA vasculitis. Lupus nephropathy and systemic vasculitis patients may have high levels of AT1R antibodies. AT1R antibodies may be associated with the severity of membranous nephropathy and the course of p-ANCA vasculitis, although influence of concomitant factors is difficult to exclude.

YAP Translocation Precedes Cytoskeletal Rearrangement in Podocyte Stress Response: A Podometric Investigation of Diabetic Nephropathy.

Podocyte loss plays a pivotal role in the pathogenesis of glomerular disease. However, the mechanisms underlying podocyte damage and loss remain poorly understood. Although detachment of viable cells has been documented in experimental Diabetic Nephropathy, correlations between reduced podocyte density and disease severity have not yet been established. YAP, a mechanosensing protein, has recently been shown to correlate with glomerular disease progression, however, the underlying mechanism has yet to be fully elucidated. In this study, we sought to document podocyte density in Diabetic Nephropathy using an amended podometric methodology, and to investigate the interplay between YAP and cytoskeletal integrity during podocyte injury. Podocyte density was quantified using TLE4 and GLEPP1 multiplexed immunofluorescence. Fourteen Diabetic Nephropathy cases were analyzed for both podocyte density and cytoplasmic translocation of YAP via automated image analysis. We demonstrate a significant decrease in podocyte density in Grade III/IV cases (124.5 per 106 μm3) relative to Grade I/II cases (226 per 106 μm3) (Student’s t-test, p < 0.001), and further show that YAP translocation precedes cytoskeletal rearrangement following injury. Based on these findings we hypothesize that a significant decrease in podocyte density in late grade Diabetic Nephropathy may be explained by early cytoplasmic translocation of YAP.

Канал TRPC6 в подоцитах почечных гломерул

The most important component of the filtration apparatus of the renal glomeruli is specialized visceral epithelial cells podocytes. The normal physiological function of podocytes is critically dependent on the proper regulation of the intracellular Ca2+ content; excessive Ca2+ influx in cells can lead to a disorder of cell morphology, podocytopathy, apoptosis and subsequent glomeruli damage. Podocytopathy is one of the primary characteristics of proteinuria and focal segmental glomerulosclerosis. One of the key proteins responsible for Ca2+ influx in podocytes is the TRPC6 channel. Since the first discovery of a mutation in a gene encoding TRPC6, the attention of the scientific community has been focused on studying the role of this ion channel in the onset and development of kidney diseases. Both an increase and a decrease in the functional activity of TRPC6 are associated with the manifestation of severe nephrotic syndromes leading to the end-stage of chronic kidney disease. The review contains materials related to the regulation of TRPC6 activity and the role of this channel in the pathogenesis of glomerular diseases.

Role of Sphingolipid Signaling in Glomerular Diseases: Focus on DKD and FSGS.

Sphingolipids are well-recognized as major players in the pathogenesis of many human diseases, including chronic kidney disease. The kidney is a very sensitive organ to alterations in sphingolipid metabolism. The critical issues to be addressed in this review relate to the role of sphingolipids and enzymes involved in sphingolipid metabolism in the pathogenesis of glomerular diseases with a special focus on podocytes, a key cellular component of the glomerular filtration barrier. Among several sphingolipids, we will highlight the role of ceramide, sphingosine, sphingosine-1-phosphate and ceramide-1-phosphate. Additionally, we will summarize the current knowledge with regard to the use of sphingolipids as therapeutic agents for the treatment of podocyte injury in kidney disease.

Sonic hedgehog connects podocyte injury to mesangial activation and glomerulosclerosis.

Glomerular disease is characterized by proteinuria and glomerulosclerosis, two pathologic features caused by podocyte injury and mesangial cell activation, respectively. However, whether these two events are linked remains elusive. Here, we report that sonic hedgehog (Shh) is the mediator that connects podocyte damage to mesangial activation and glomerulosclerosis. Shh was induced in glomerular podocytes in various models of proteinuric chronic kidney diseases (CKD). However, mesangial cells in the glomeruli, but not podocytes, responded to hedgehog ligand. In vitro, Shh was induced in podocytes after injury and selectively promoted mesangial cell activation and proliferation. In a miniorgan culture of isolated glomeruli, Shh promoted mesangial activation but did not affect the integrity of podocytes. Podocyte-specific ablation of Shh in vivo exhibited no effect on proteinuria after adriamycin injection but hampered mesangial activation and glomerulosclerosis. Consistently, pharmacologic blockade of Shh signaling decoupled proteinuria from glomerulosclerosis. In humans, Shh was upregulated in glomerular podocytes in patients with CKD and its circulating level was associated with glomerulosclerosis but not proteinuria. These studies demonstrate that Shh mechanistically links podocyte injury to mesangial activation in the pathogenesis of glomerular diseases. Our findings also illustrate a crucial role for podocyte-mesangial communication in connecting proteinuria to glomerulosclerosis.

Identifying geospatial “hot spots” of glomerular diseases: opportunities and challenges

Canney etal. discovered significant geographic clustering of incident glomerular diseases by applying geospatial modeling techniques to routinely collected information. The results provide further evidence to support the role of environmental triggers in the pathogenesis of glomerular diseases. The study highlights the largely untapped capacity to exploit routinely collected administrative data with appropriate analyses to explore disease pathogenesis and inform health service planning.

Epidemiology of Glomerular Disease in Southern Arizona: Review of 10-Year Renal Biopsy Data.

Glomerulonephritis stands third in terms of the etiologies for end-stage kidney disease in the USA. The aim of this study was to look at the patterns of biopsy-proven glomerulonephritis based on data from a single center.Kidney biopsy specimens of all patients above the age of 18 years, over a 10-year period, who had diagnosis of nondiabetic glomerular disease, were selected for the study.The most common histopathological diagnosis was focal and segmental glomerulosclerosis (FSGS) (22.25%, 158/710) followed by membranous nephropathy (20.28%, 144/710) and immunoglobulin (Ig)A nephropathy (19.71%, 140/710). There was male preponderance in all histological variants except IgA nephropathy, lupus nephritis, and pauci-immune glomerulonephritis. The race distribution was uneven, and all histological variants, except minimal change disease and lupus nephritis, were more commonly seen in whites. In a separate analysis of the histological pattern in Hispanics, lupus nephritis was the most common pathology (28.70%, 62/216) followed by FSGS (18.05%, 39/216). In American Indian population, the most common pathology was IgA nephropathy (33.33%, 8/24) followed by FSGS (16.67%, 4/24).This study highlights the histopathological patterns of glomerular disease in southern Arizona. The data suggest regional and ethnic variations in glomerular disease that may point towards genetic or environmental influence in the pathogenesis of glomerular diseases.

The Players: Cells Involved in Glomerular Disease.

Glomerular diseases are common and important. They can arise from systemic inflammatory or metabolic diseases that affect the kidney. Alternately, they are caused primarily by local glomerular abnormalities, including genetic diseases. Both intrinsic glomerular cells and leukocytes are critical to the healthy glomerulus and to glomerular dysregulation in disease. Mesangial cells, endothelial cells, podocytes, and parietal epithelial cells within the glomerulus all play unique and specialized roles. Although a specific disease often primarily affects a particular cell type, the close proximity, and interdependent functions and interactions between cells mean that even diseases affecting one cell type usually indirectly influence others. In addition to those cells intrinsic to the glomerulus, leukocytes patrol the glomerulus in health and mediate injury in disease. Distinct leukocyte types and subsets are present, with some being involved in different ways in an individual glomerular disease. Cells of the innate and adaptive immune systems are important, directing systemic immune and inflammatory responses, locally mediating injury, and potentially dampening inflammation and facilitating repair. The advent of new genetic and molecular techniques, and new disease models means that we better understand both the basic biology of the glomerulus and the pathogenesis of glomerular disease. This understanding should lead to better diagnostic techniques, biomarkers, and predictors of prognosis, disease severity, and relapse. With this knowledge comes the promise of better therapies in the future, directed toward halting pathways of injury and fibrosis, or interrupting the underlying pathophysiology of the individual diseases that lead to significant and progressive glomerular disease.

Non-immunologic actions of calcineurin inhibitors in proteinuric kidney diseases.

Diseases affecting the glomerulus are the most common cause of end-stage kidney disease in developed countries (1). These disorders are characterized by significant proteinuria, and the level of proteinuria is an independent risk factor for disease progression (2). Podocytes are thought to play a key role in the pathogenesis of glomerular diseases (3, 4). The importance of podocytes in glomerular diseases is highlighted by genetic studies, which have identified mutant podocyte proteins that cause familial forms of nephrosis (5). Because podocytes are terminally differentiated cells with little capacity for replication, their ability to compensate for podocyte loss is limited (3). A component of current therapy is, therefore, focused on reducing podocyte injury by decreasing systemic blood pressure (BP) and inhibition of the renin–angiotensin system (2, 6).

SPLA2 IB induces human podocyte apoptosis via the M-type phospholipase A2 receptor.

The M-type phospholipase A2 receptor (PLA2R) is expressed in podocytes in human glomeruli. Group IB secretory phospholipase A2 (sPLA2 IB), which is one of the ligands of the PLA2R, is more highly expressed in chronic renal failure patients than in controls. However, the roles of the PLA2R and sPLA2 IB in the pathogenesis of glomerular diseases are unknown. In the present study, we found that more podocyte apoptosis occurs in the kidneys of patients with higher PLA2R and serum sPLA2 IB levels. In vitro, we demonstrated that human podocyte cells expressed the PLA2R in the cell membrane. After binding with the PLA2R, sPLA2 IB induced podocyte apoptosis in a time- and concentration-dependent manner. sPLA2 IB-induced podocyte PLA2R upregulation was not only associated with increased ERK1/2 and cPLA2α phosphorylation but also displayed enhanced apoptosis. In contrast, PLA2R-silenced human podocytes displayed attenuated apoptosis. sPLA2 IB enhanced podocyte arachidonic acid (AA) content in a dose-dependent manner. These data indicate that sPLA2 IB has the potential to induce human podocyte apoptosis via binding to the PLA2R. The sPLA2 IB-PLA2R interaction stimulated podocyte apoptosis through activating ERK1/2 and cPLA2α and through increasing the podocyte AA content.

Acute effects of angiotensin II on calcium influx in the podocytes of the freshly isolated glomeruli of the wild type and TRPC6‐deficient mice (892.1)

Podocytes play a key role in regulating glomerular permeability and maintaining glomerular structure. It was previously reported that angiotensin (Ang II) enhances albuminuria and increases calcium flux in podocytes by activating TRPC6 channels. The goal of this study was to examine acute effects of Ang II on intracellular calcium levels and endogenous ion channels activity in their native setting, podocytes of freshly isolated mouse glomeruli. Single channel patch‐clamp experiments demonstrated that an ion channel with distinct TRPC6 properties (22 pS) was present in the wild type animals, however it was not identified in TRPC6 knockout mice. Ang II acutely activated these native channels in the podocytes of wild type, but not TRPC6 deficient mice; the effect was mediated by changes in the channel open probability. Data obtained in CHO cells transiently expressed with TRPC6 and AT1R confirmed these findings. We further measured alterations in intracellular calcium stimulated by Ang II in the presence and absence of the TRPC inhibitors gadolinium chloride and SKF 96365, and TRPC6 activator flufenamic acid; these experiments were performed in Fluo4/FuraRed loaded podocytes of the intact glomeruli of the wild type and TRPC6‐deficient mice. Our data have provided the first direct evidence of Ang II‐dependent activation of TRPC6 channels and calcium influx in podocytes, which might play a significant role in the pathogenesis of glomerular diseases.Grant Funding Source: Supported by NIH HL108880, DK079968, Z01‐ES‐101684, ADA 1‐10‐BS‐168, ASN Ben J Lipps Fellowship

Actin-associated Proteins in the Pathogenesis of Podocyte Injury

Podocytes have a complex cellular architecture with interdigitating processes maintained by a precise organization of actin filaments. The actin-based foot processes of podocytes and the interposed slit diaphragm form the final barrier to proteinuria. The function of podocytes is largely based on the maintenance of the normal foot process structure with actin cytoskeleton. Cytoskeletal dynamics play important roles during normal podocyte development, in maintenance of the healthy glomerular filtration barrier, and in the pathogenesis of glomerular diseases. In this review, we focused on recent findings on the mechanisms of organization and reorganization of these actin-related molecules in the pathogenesis of podocyte injury and potential therapeutics targeting the regulation of actin cytoskeleton in podocytopathies.

Close Relations between Podocyte Injuries and Membranous Proliferative Glomerulonephritis in Autoimmune Murine Models

Background: Membranous proliferative glomerulonephritis (MPGN) is a major primary cause of chronic kidney disease (CKD). Podocyte injury is crucial in the pathogenesis of glomerular disease with proteinuria, leading to CKD. To assess podocyte injuries in MPGN, the pathological features of spontaneous murine models were analyzed. Methods: The autoimmune-prone mice strains BXSB/MpJ-Yaa and B6.MRL-(D1Mit202-D1Mit403) were used as the MPGN models, and BXSB/MpJ-Yaa⁺ and C57BL/6 were used as the respective controls. In addition to clinical parameters and glomerular histopathology, the protein and mRNA levels of podocyte functional markers were evaluated as indices for podocyte injuries. The relation between MPGN pathology and podocyte injuries was analyzed by statistical correlation. Results: Both models developed MPGN with albuminuria and elevated serum anti-double-strand DNA (dsDNA) antibody levels. BXSB/MpJ-Yaa and B6.MRL showed severe proliferative lesions with T and B cell infiltrations and membranous lesions with T cell infiltrations, respectively. Foot process effacement and microvillus-like structure formation were observed ultrastructurally in the podocytes of both MPGN models. Furthermore, both MPGN models showed a decrease in immune-positive areas of nephrin, podocin and synaptopodin in the glomerulus, and in the mRNA expression of Nphs1, Nphs2, Synpo, Actn4, Cd2ap, and Podxl in the isolated glomerulus. Significant negative correlations were detected between serum anti-dsDNA antibody levels and glomerular Nphs1 expression, and between urinary albumin-to-creatinine ratio and glomerular expression of Nphs1, Synpo, Actn4, Cd2ap, or Podxl.Conclusion: MPGN models clearly developed podocyte injuries characterized by the decreased expression of podocyte functional markers with altered morphology. These data emphasized the importance of regulation of podocyte injuries in MPGN.

Inflammatory Chemokine Expression via Toll-Like Receptor 3 Signaling in Normal Human Mesangial Cells

The innate and adaptive immune systems have been reported to play an important role in the pathogenesis of glomerular diseases. Since viral infections may trigger the development of inflammatory renal disease or the worsening of preexisting renal disease, recent studies have focused on the involvement of toll-like receptors (TLRs) and their signaling pathways in the inflammatory processes of glomerular cells. Viral double-stranded RNA (dsRNA) can activate not only TLR3 located within intracellular endosomes but also retinoic-acid-inducible-gene-I- (RIG-I-) like helicase receptors located within the cytosol. RIG-I and melanoma differentiation-associated gene 5 (MDA5) are members of the RNA helicase family in the cytosol, and both act as pathogen recognition receptors. The activation of TLRs and their downstream immune responses can be induced by both infectious pathogens and noninfectious stimuli such as endogenous ligands, and this mechanism may be involved in the pathogenesis of autoimmune renal diseases. However, there are few data on the interaction between TLR3, MDA5, and RIG-I in autoimmune glomerular diseases. Based on our recent experimental studies using cultured normal human mesangial cells (MCs), we found that novel TLR3-mediated signaling pathways in MCs may be involved in the pathogenesis of glomerular diseases. In the present paper, we summarize our recent findings.