Bullous Pemphigoid With a Dual Pattern of Glomerular Immune Complex Disease.

A 75-year-old man presented with a blistering skin disease and nephrotic syndrome. Bullous pemphigoid was diagnosed by linear immunoglobulin G (IgG) and C3 staining along the basement membrane zone of a skin biopsy specimen and by the presence of circulating IgG recognizing the 180-kDa bullous pemphigoid antigen (BP180; type XVII collagen). A kidney biopsy specimen showed endocapillary inflammation without crescents. Direct immunofluorescence showed strong IgG and C3 staining in a combined granular and linear pattern along the glomerular basement membrane. Electron microscopy showed subepithelial deposits. In serum, no antibodies against the Goodpasture antigen (type IV collagen) or phospholipase A2 receptor were detected. Indirect immunofluorescence studies using the patient's serum showed a strikingly linear but not granular IgG pattern along the epithelial basement membranes of monkey esophagus and kidney. Although type XVII collagen was recently identified in the glomerulus, the patient's serum did not produce a 180-kDa band on immunoblot of kidney tissue and still stained glomeruli of BP180 knockout mice by indirect immunofluorescence. The patient was treated with prednisone and azathioprine, which resulted in complete remission of skin and kidney manifestations. Although bullous pemphigoid has been reported previously in association with anti-glomerular basement membrane disease or membranous nephropathy, this case demonstrates both elements in 1 patient. This concurrence and the linear pattern on indirect immunofluorescence support the possibility of cross-reactive or parallel autoantibodies to basement membranes with a secondary membranous component.

Advances in the pathology of glomerular diseases.

Glomerular injury can be caused by numerous insults including hemodynamics, infections and immunity, hereditary and metabolic diseases, and toxicity. Basic and translational experimental studies in combination with clinical research in patients with renal disease have advanced our understanding of the etiology and pathogenesis of many forms of glomerulonephritis. This new knowledge has facilitated classification and treatment and has contributed to a better outcome of patients with renal disease. Since renal disease almost without exception leads to systemic cardiovascular complications, these advances are also of general health interest. Here, we shall briefly review general principles in the pathology of glomerular injury and discuss recent developments in the study of podocytopathies; membranous glomerulopathy; ANCA-associated vasculitis; C3 glomerulopathies and the role of complement in endothelial injury; and the prognostic value of the renal biopsy in predicting long-term outcome in lupus nephritis, vasculitis and IgA nephropathy.

Acute kidney injury during therapy with an antisense oligonucleotide directed against PCSK9.

Antisense oligonucleotides have been explored widely in clinical trials and generally are considered to be nontoxic for the kidney, even at high concentrations. We report a case of toxic acute tubular injury in a healthy 56-year-old female volunteer after a pharmacologically active dose of a locked nucleic acid antisense oligonucleotide was administered. The patient received 3 weekly subcutaneous doses of experimental drug SPC5001, an antisense oligonucleotide directed against PCSK9 (proprotein convertase subtilisin/kexin type 9) that is under investigation as an agent to reduce low-density lipoprotein cholesterol levels. Five days after the last dose, the patient's serum creatinine level increased from 0.81 mg/dL at baseline (corresponding to an estimated glomerular filtration rate [eGFR] of 78 mL/min/1.73 m(2)) to 2.67 mg/dL (eGFR, 20 mL/min/1.73 m(2)), and this increase coincided with the presence of white blood cells, granular casts, and minimal hematuria on urine microscopy. The patient's serum creatinine level peaked at 3.81 mg/dL (eGFR, 13 mL/min/1.73 m(2)) 1 week after the last oligonucleotide dose. Kidney biopsy showed multifocal tubular necrosis and signs of oligonucleotide accumulation. Upon conservative treatment, the patient's serum creatinine level gradually decreased and reached her baseline level 44 days after the last oligonucleotide was administered. The patient recovered fully and kidney function was normal at every follow-up visit.

Kidney disease in lupus is not always 'lupus nephritis'.

In lupus erythematosus, elevated serum creatinine levels and urinary abnormalities implicate a kidney disorder, which may not always be lupus nephritis as defined by the current classification of the International Society of Nephrology/Renal Pathology Society. The signs of renal dysfunction may be caused by lupusunrelated renal injury such as drug toxicity or infection or by lupus-associated mechanisms that are not part of the classification, such as minimal change nephrotic syndrome or thrombotic microangiopathy. The latter seems to complicate lupus nephritis more frequently than previously thought. An unbiased assessment of kidney disease in lupus requires a kidney (re-)biopsy to define the appropriate management.

A position paper on standardizing the nonneoplastic kidney biopsy report.

The biopsy report for nonneoplastic kidney diseases represents a complex integration of clinical data with light, immunofluorescence, and electron microscopic findings. Practice guidelines for the handling and processing of the renal biopsy have previously been created. However, specific guidelines for essential pathologic parameters that should be included in these pathology reports do not exist. The Renal Pathology Society has coordinated an effort through the formation of an ad hoc committee to enumerate the essential elements and pathologic parameters that should be reported for every biopsy specimen. This endeavor aims to establish a minimum reporting standard and to improve communication between pathologists and other physicians. This document represents the collective effort and consensus opinions of this ad hoc committee of the Renal Pathology Society.

Involvement of connective tissue growth factor in human and experimental hypertensive nephrosclerosis.

BACKGROUND/AIMS: Connective tissue growth factor (CTGF; CCN2) has been implicated as a marker and mediator of fibrosis in human and experimental renal disease. METHODS: We performed a comparative analysis of CTGF expression in hypertensive patients with and without nephrosclerosis, and in uninephrectomized and sham-operated spontaneously hypertensive rats (UNX-SHR and 2K-SHR). RESULTS: Urinary and plasma CTGF were elevated in patients with hypertensive nephrosclerosis, and increased renal CTGF expression was mainly localized in podocytes. Accordingly, elevation of urinary, plasma, and tissue CTGF in UNX-SHR coincided and correlated with proteinuria, glomerulosclerosis, and tubulointerstitial fibrosis. Thirty-two weeks after uninephrectomy, mean glomerular CTGF mRNA expression was increased 1.3-fold over baseline, mainly due to 1.7-fold higher expression in glomeruli undergoing sclerosis. In parallel, tubulointerstitial CTGF and α-smooth muscle actin were upregulated in UNX-SHR. CTGF was increased in the media of arcuate and interlobar arteries, while arterioles remained negative. CONCLUSIONS: Glomerulosclerosis, tubulointerstitial fibrosis, and arterial media hypertrophy lesions of hypertensive nephrosclerosis are all characterized by increased CTGF tissue expression, which is associated with a concomitant increase in CTGF in blood and urine. These findings identify CTGF as a promising biomarker for progression of hypertensive nephrosclerosis, and as a likely key factor in the pathogenesis of this disease.

Expression patterns of connective tissue growth factor and of TGF-beta isoforms during glomerular injury recapitulate glomerulogenesis.

Transforming growth factor (TGF)-beta(1), -beta(2), and -beta(3) are involved in control of wound repair and development of fibrosis. Connective tissue growth factor (CTGF) expression is stimulated by all TGF-beta isoforms and is abundant in glomerulosclerosis and other fibrotic disorders. CTGF is hypothesized to mediate profibrotic effects of TGF-beta(1) or to facilitate interaction of TGF-beta(1) with its receptor, but its interactions with TGF-beta isoforms in nonpathological conditions are unexplored so far. Tissue repair and remodeling may recapitulate gene transcription at play in organogenesis. To further delineate the relationship between CTGF and TGF-beta, we compared expression patterns of CTGF and TGF-beta isoforms in rat and human glomerulogenesis and in various human glomerulopathies. CTGF mRNA was present in the immediate precursors of glomerular visceral and parietal epithelial cells in the comma- and S-shaped stages, but not in earlier stages of nephron development. During the capillary loop and maturing glomerular stages and simultaneous with the presence of TGF-beta(1), -beta(2), and -beta(3) protein, CTGF mRNA expression was maximal and present only in differentiating glomerular epithelial cells. CTGF protein was also present on precursors of mesangium and glomerular endothelium, suggesting possible paracrine interaction. Concomitant with the presence of TGF-beta(2) and -beta(3) protein, and in the absence of TGF-beta(1), CTGF mRNA and protein expression was restricted to podocytes in normal adult glomeruli. However, TGF-beta(1) and CTGF were again coexpressed, often with TGF-beta(2) and -beta(3), in particular in podocytes in proliferative glomerulonephritis and also in mesangial cells in diabetic nephropathy and IgA nephropathy (IgA NP). Coordinated expression of TGF-beta isoforms and of CTGF may be involved in normal glomerulogenesis and possibly in maintenance of glomerular structure and function at adult age. Prolonged overexpression of TGF-beta(1) and CTGF is associated with development of severe glomerulonephritis and glomerulosclerosis.

The Oxford IgA nephropathy clinicopathological classification is valid for children as well as adults.

To study the predictive value of biopsy lesions in IgA nephropathy in a range of patient ages we retrospectively analyzed the cohort that was used to derive a new classification system for IgA nephropathy. A total of 206 adults and 59 children with proteinuria over 0.5 g/24 h/1.73 m(2) and an eGFR of stage-3 or better were followed for a median of 69 months. At the time of biopsy, compared with adults children had a more frequent history of macroscopic hematuria, lower adjusted blood pressure, and higher eGFR but similar proteinuria. Although their outcome was similar to that of adults, children had received more immunosuppressants and achieved a lower follow-up proteinuria. Renal biopsies were scored for variables identified by an iterative process as reproducible and independent of other lesions. Compared with adults, children had significantly more mesangial and endocapillary hypercellularity, and less segmental glomerulosclerosis and tubulointerstitial damage, the four variables previously identified to predict outcome independent of clinical assessment. Despite these differences, our study found that the cross-sectional correlation between pathology and proteinuria was similar in adults and children. The predictive value of each specific lesion on the rate of decline of renal function or renal survival in IgA nephropathy was not different between children and adults.

Stem cell factor expression after renal ischemia promotes tubular epithelial survival.

BACKGROUND: Renal ischemia leads to apoptosis of tubular epithelial cells and results in decreased renal function. Tissue repair involves re-epithelialization of the tubular basement membrane. Survival of the tubular epithelium following ischemia is therefore important in the successful regeneration of renal tissue. The cytokine stem cell factor (SCF) has been shown to protect the tubular epithelium against apoptosis. METHODOLOGY/PRINCIPAL FINDINGS: In a mouse model for renal ischemia/reperfusion injury, we studied how expression of c-KIT on tubular epithelium and its ligand SCF protect cells against apoptosis. Administration of SCF specific antisense oligonucleotides significantly decreased specific staining of SCF following ischemia. Reduced SCF expression resulted in impaired renal function, increased tubular damage and increased tubular epithelial apoptosis, independent of inflammation. In an in vitro hypoxia model, stimulation of tubular epithelial cells with SCF activated survival signaling and decreased apoptosis. CONCLUSIONS/SIGNIFICANCE: Our data indicate an important role for c-KIT and SCF in mediating tubular epithelial cell survival via an autocrine pathway.

The Oxford classification of IgA nephropathy: pathology definitions, correlations, and reproducibility.

Pathological classifications in current use for the assessment of glomerular disease have been typically opinion-based and built on the expert assumptions of renal pathologists about lesions historically thought to be relevant to prognosis. Here we develop a unique approach for the pathological classification of a glomerular disease, IgA nephropathy, in which renal pathologists first undertook extensive iterative work to define pathologic variables with acceptable inter-observer reproducibility. Where groups of such features closely correlated, variables were further selected on the basis of least susceptibility to sampling error and ease of scoring in routine practice. This process identified six pathologic variables that could then be used to interrogate prognostic significance independent of the clinical data in IgA nephropathy (described in the accompanying article). These variables were (1) mesangial cellularity score; percentage of glomeruli showing (2) segmental sclerosis, (3) endocapillary hypercellularity, or (4) cellular/fibrocellular crescents; (5) percentage of interstitial fibrosis/tubular atrophy; and finally (6) arteriosclerosis score. Results for interobserver reproducibility of individual pathological features are likely applicable to other glomerulonephritides, but it is not known if the correlations between variables depend on the specific type of glomerular pathobiology. Variables identified in this study withstood rigorous pathology review and statistical testing and we recommend that they become a necessary part of pathology reports for IgA nephropathy. Our methodology, translating a strong evidence-based dataset into a working format, is a model for developing classifications of other types of renal disease.

The Oxford classification of IgA nephropathy: rationale, clinicopathological correlations, and classification.

IgA nephropathy is the most common glomerular disease worldwide, yet there is no international consensus for its pathological or clinical classification. Here a new classification for IgA nephropathy is presented by an international consensus working group. The goal of this new system was to identify specific pathological features that more accurately predict risk of progression of renal disease in IgA nephropathy, thus enabling both clinicians and pathologists to improve individual patient prognostication. In a retrospective analysis, sequential clinical data were obtained on 265 adults and children with IgA nephropathy who were followed for a median of 5 years. Renal biopsies from all patients were scored by pathologists blinded to the clinical data for pathological variables identified as reproducible by an iterative process. Four of these variables: (1) the mesangial hypercellularity score, (2) segmental glomerulosclerosis, (3) endocapillary hypercellularity, and (4) tubular atrophy/interstitial fibrosis were subsequently shown to have independent value in predicting renal outcome. These specific pathological features withstood rigorous statistical analysis even after taking into account all clinical indicators available at the time of biopsy as well as during follow-up. The features have prognostic significance and we recommended they be taken into account for predicting outcome independent of the clinical features both at the time of presentation and during follow-up. The value of crescents was not addressed due to their low prevalence in the enrolled cohort.

Endogenous tissue-type plasminogen activator is protective during ascending urinary tract infection.

BACKGROUND: Acute pyelonephritis is one of the most common bacterial infections. Tissue-type plasminogen activator (tPA) is a potent fibrinolytic agent, but can play a role in inflammatory processes as well. METHODS: We induced pyelonephritis in tPA(-/-) and C57BL/6 wild-type (WT) mice by intravesical inoculation with 10(10) CFU uropathogenic Escherichia coli 1677. The mice were killed after 24 and 48 h, after which bacterial outgrowth and cytokine levels in kidney homogenates were determined. Influx of neutrophils was quantified by myeloperoxidase-ELISA. Neutrophil phagocytosis and oxidative burst were measured. RESULTS: The tPA(-/-) kidneys contained significantly higher numbers of E. coli CFU, accompanied by higher levels of interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha). The number of infiltrating neutrophils was similar in tPA(-/-) and WT mice at both time points, suggesting that tPA(-/-) neutrophils have a lower ability to eliminate E. coli. Phagocytosis of E. coli organisms was not diminished in tPA(-/-) neutrophils. Interestingly, tPA(-/-) neutrophils showed a significantly lower ability to generate an oxidative burst reaction upon stimulation with E. coli than WT neutrophils. Incubation with recombinant tPA reversed this effect completely. CONCLUSIONS: These results show that deletion of the tPA-gene in mice leads to lower bactericidal potential of tPA(-/-) neutrophils, which results in significantly more bacterial outgrowth during experimental pyelonephritis.

Plasminogen activator inhibitor-1 regulates neutrophil influx during acute pyelonephritis.

Acute pyelonephritis, frequently caused by Escherichia coli, is a substantial health problem. Plasminogen activator inhibitor type-1 (PAI-1) not only inhibits plasminogen activation but is also involved in cell migration. To determine if it has a role in host defense, we induced pyelonephritis in PAI-1 gene knockout and wild-type mice by intravesical inoculation with uropathogenic E. coli 1677. Bacterial growth was determined on blood agar plates in portions of the kidneys homogenized in sterile saline. Kidney levels of PAI-1 were increased in infected compared to control mice, suggesting a physiological role for PAI-1 during pyelonephritis. The knockout mice had significantly more bacterial outgrowth in kidney homogenates compared to the wild-type mice. Strikingly, higher colony-forming units were accompanied by increased levels of the cytokines TNF-alpha, IL-1beta, and IL-6 in the kidneys of knockout mice, but levels of the chemokines KC and MIP-2 were not different. Remarkably, plasma levels of KC were higher, but renal neutrophil influx was significantly lower, in the knockout than in the wild-type mice. Our study shows that PAI-1 is critically involved in host defense against E. coli-induced acute pyelonephritis, in part, by modulating neutrophil influx.

Podocyte foot process effacement as a diagnostic tool in focal segmental glomerulosclerosis.

Podocyte foot process effacement is characteristic of proteinuric renal diseases. In minimal change nephrotic syndrome (MCNS) foot processes are diffusely effaced whereas the extent of effacement varies in focal segmental glomerulosclerosis (FSGS). Here we measured foot process effacement in FSGS and compared it to that in MCNS and in normal kidneys. A clinical diagnosis was used to differentiate idiopathic FSGS from secondary FSGS. Median foot process width, determined morphometrically by electron microscopy, was 3236 nm in 17 patients with idiopathic FSGS, 1098 nm in 7 patients with secondary FSGS, and 1725 nm in 15 patients with MCNS, as compared to 562 nm in 12 control patients. Multivariate analysis showed that foot process width did not correlate with proteinuria or serum albumin levels but was significantly associated as an independent factor with the type of disease. Foot process width over 1500 nm differentiated idiopathic from secondary FSGS with high sensitivity and specificity. Our results show that quantitative analysis of foot processes may offer a potential tool to distinguish idiopathic from secondary FSGS.

Enhanced mobilization of bone marrow cells does not ameliorate renal fibrosis.

BACKGROUND: The plasticity of bone marrow-derived stem cells, also comprising haematopoietic stem cells, has been shown to extend to renal epithelial lineages. Yet, the low rate of their contribution to the injured kidney has led to questions regarding their significance in tissue repair after acute injury. We describe here the effect of stem cell mobilization therapy on the progression of renal fibrosis in a mouse model of chronic obstructive nephropathy. METHODS: Mice were subjected to unilateral ureter obstruction (UUO) and treated with stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF) or saline. Circulating cells were analysed by flow cytometry; labelled bone marrow c-KIT(HIGH) cells were injected into animals subjected to UUO. Granulocytes, macrophages, cellular proliferation or apoptosis and myofibroblasts were detected by immunostaining. Collagen deposition was determined by measuring renal hydroxyproline contents. Cytokine levels were measured by ELISA. RESULTS: SCF/G-CSF treatment of mice induced significant haematopoietic stem and progenitor cell mobilization from the bone marrow. Although these cells are able to migrate to the obstructed kidney, they did not influence renal damage, fibrosis and inflammatory cell influx. CONCLUSIONS: Although SCF/G-CSF treatment significantly enhanced the availability of haematopoietic stem cells to the obstructed kidney, the progression of renal fibrosis could not be delayed or halted. Our results indicate that effective stem cell mobilization does not alter renal fibrosis.