Clinical and Pathologic Characterization of Proteinuric Kidney Disease in Australian and New Zealand Dogs.

Podocytes regulate the glomerular basement membrane protein nephronectin by means of miR-378a-3p in glomerular diseases

Glomerulonephropathy is a rare complication of Takayasu's arteritis (TA). To date, most glomerulonephropathies associated with TA show the histological feature of mesangial proliferation. Membranous glomerulonephropathy (MG) is a form of glomerulonephropathy in which the mesangial proliferation is not conspicuous and its association with TA is extremely rare. A 54-year-old man was referred to our hospital due to progressive edema in the lower limbs and nephrotic range proteinuria. Five years previously, he underwent percutaneous angioplasty for left subclavian artery stenosis. Kidney biopsy revealed stage II MG. General examination including enhanced CT scan confirmed the presence of TA. He started oral prednisolone therapy at a dose of 40 mg daily. The C-reactive protein level normalized 7 days after the prednisolone therapy. Three months later, proteinuria had remitted. Though the true relationship between MG and TA was not revealed in present case, considering the fact that complete remission of nephrotic syndrome occurred following the improvement of C-reactive protein level in response to steroid therapy, TA might be the secondary cause of MG. To our best knowledge, only two case reports described the association of MG and TA previously. Those two patients, however, also demonstrated the feature of systemic lupus erythematosus in addition to TA. This is the first case report that describes a patient who presented as MG associated with TA, but not complicated by systemic lupus erythematosus.

Oxidative stress plays a role in mediating podocyte injury and proteinuria. However, the underlying mechanism remains poorly understood. In this study, we investigated the potential role of C-X-C chemokine receptor type 4 (CXCR4), the receptor for stromal cell-derived factor 1α (SDF-1α), in mediating oxidative stress-induced podocyte injury. In mouse model of adriamycin nephropathy (ADR), CXCR4 expression was significantly induced in podocytes as early as 3 days. This was accompanied by an increased upregulation of oxidative stress in podocyte, as demonstrated by malondialdehyde assay, nitrotyrosine staining and secretion of 8-hydroxy-2'-deoxyguanosine in urine, and induction of NOX2 and NOX4, major subunits of NADPH oxidase. CXCR4 was also induced in human kidney biopsies with proteinuric kidney diseases and colocalized with advanced oxidation protein products (AOPPs), an established oxidative stress trigger. Using cultured podocytes and mouse model, we found that AOPPs induced significant loss of podocyte marker Wilms tumor 1 (WT1), nephrin, and podocalyxin, accompanied by upregulation of desmin both in vitro and in vivo. Furthermore, AOPPs worsened proteinuria and aggravated glomerulosclerosis in ADR. These effects were associated with marked activation of SDF-1α/CXCR4 axis in podocytes. Administration of AMD3100, a specific inhibitor of CXCR4, reduced proteinuria and ameliorated podocyte dysfunction and renal fibrosis triggered by AOPPs in mice. In glomerular miniorgan culture, AOPPs also induced CXCR4 expression and downregulated nephrin and WT1. Innovation and Conclusion: These results suggest that chemokine receptor CXCR4 plays a crucial role in mediating oxidative stress-induced podocyte injury, proteinuria, and renal fibrosis. CXCR4 could be a new target for mitigating podocyte injury, proteinuria, and glomerular sclerosis in proteinuric chronic kidney disease. Antioxid. Redox Signal. 27, 345-362.

To the Editor: We thank Benigni and Remuzzi1 for their informative editorial relating to our study.2 They raise a number of pertinent issues. They comment that it would be interesting to know whether subjects included with focal segmental glomerulosclerosis (FSGS) had idiopathic or secondary disease, because there are currently few treatments available for this condition. We agree that specifically studying FSGS would be of great interest. However, all of the FSGS subjects included in our study had secondary disease. Idiopathic FSGS, more often than secondary, presents with problematic nephrotic syndrome (a specific exclusion for our study), …

Nephrology Crossword: Genetics and glomerulopathies

Background and Aims Proteinuria is not only a biomarker of chronic kidney disease (CKD) and a risk predictor of adverse outcomes but also a driver of kidney disease progression. The excessive filtration of plasma proteins through the glomerular filtration barrier exerts a toxic effect on tubular cells which ultimately leads to fibrosis and end-stage kidney disease (ESKD. The aim of this study was to assess the levels of various tubular biomarkers in both serum and urine in patients with biopsied glomerular and proteinuric kidney diseases, and correlate them with renal histology and kidney outcomes. Method A retrospective study and observational study was conducted at a single center from January 2016 to December 2021. Serum and urine samples were collected on the same day of renal biopsy and were correlated with histological data from a cohort of 156 patients with proteinuric kidney diseases. Kidney outcomes were registered during a median follow-up period of 26 months and defined as a decrease in eGFR ≥ 40% from baseline or the development of end-stage kidney disease. The following urinary markers, adjusted to urine creatinine, were analyzed: β2-mcg (beta 2 microglobulin), α1-mcg (alpha 1 microglobulin), NGAL (Neutrophil Gelatinase-Associated Lipocalin), uKIM-1 (Kidney Injury Molecule-1), MCP-1 (Monocyte Chemoattractant Protein-1), uDKK-3 (urinary Dickkopf-3), and uUMOD (uromodulin). Serum markers sKIM-1 and uUMOD were also collected. Results Regarding the etiology of proteinuric kidney disease, the majority corresponded to glomerular disease (68.6%) followed by diabetic kidney disease (12.8%). Higher levels of proteinuria were associated with increased values of β2-mcg and α1-mcg levels and low levels of uUMOD and sUMOD. A significant correlation between the extent of interstitial fibrosis and specific biomarkers was observed: uDKK3 (rho = 0.804, p < 0.001), sKIM-1 (rho = 0.472, p < 0.001), sUMOD (rho = −0.370, p < 0.001), uUMOD (rho = −0.317, p < 0.001), MCP-1 (rho = 0.374, p < 0.001), uKIM-1 (rho = 0.368, p < 0.001), and β2-mcg (rho = 0.392, p < 0.001). Multivariate regression analysis identified uDKK3 as an independent predictor of interstitial fibrosis (Beta 0.728, p < 0.001) adjusted for age, serum creatinine and proteinuria. Elevated levels of MCP-1 and uKIM-1 were associated with a higher risk of significant cortical interstitial inflammation >10% in the logistic regression analysis adjusted for eGFR, proteinuria, and microhematuria: MCP-1 OR = 5.14, 95% CI (2.27−11.62), p < 0.001 and uKIM-1 OR = 1.64, 95% CI (1.05−2.58), p = 0.031. Patients with higher tertiles of β2mcg, MCP1, uDKK3, and KIM1s, and lower tertiles of uUMOD and sUMOD experienced a significantly reduced renal event-free survival in the analysis of Kaplan-Meier model (Fig.). Moreover, of all the evaluated markers, uDKK3 was identified as the best predictor of renal events [HR = 1.03, 95% CI (1.01−1.06), p = 0.008], independently of age, baseline eGFR, proteinuria, and the extent of interstitial fibrosis at the time of renal biopsy. Conclusion Tubular biomarkers may offer prognostic value in proteinuric kidney diseases, particularly uDKK3, exhibiting a notable correlation with interstitial fibrosis and serving as a potential predictor of CKD progression.

Differentiating between diabetic kidney disease (DKD) and non-diabetic kidney disease (NDKD) in patients with Type 2 diabetes mellitus (T2DM) is important due to implications on treatment and prognosis. Clinical methods to accurately distinguish DKD from NDKD are lacking. We aimed to develop and validate a novel nomogram to predict DKD in patients with T2DM and proteinuric kidney disease to guide decision for kidney biopsy. A hundred and two patients with Type 2 Diabetes Mellitus (T2DM) who underwent kidney biopsy from 1st January 2007 to 31st December 2016 were analysed. Univariate and multivariate analyses were performed to identify predictive variables and construct a nomogram. The discriminative ability of the nomogram was assessed by calculating the area under the receiver operating characteristic curve (AUROC), while calibration was assessed using the Hosmer-Lemeshow goodness-of-fit test and calibration plot. Internal validation of the nomogram was assessed using bootstrap resampling. Duration of T2DM, HbA1c, absence of hematuria, presence ofdiabetic retinopathy and absence ofpositive systemic biomarkers were found to be independent predictors of DKD in multivariate analysis and were represented as a nomogram. The nomogram showed excellent discrimination, with a bootstrap-corrected C statistic of 0.886 (95% CI 0.815-0.956). Both the calibration curve and the Hosmer-Lemeshow goodness-of-fit test (p = 0.242) showed high degree of agreement between the prediction and actual outcome, with the bootstrap bias-corrected curve similarly indicating excellent calibration. A novel nomogram incorporating 5 clinical parameters is useful in predicting DKD in type 2 diabetes mellitus patients with proteinuric kidney disease.

Hepatitis B surface antigenemia in North American children with membranous glomerulonephropathy

To determine whether breed, sex, country of origin, and age are associated with anatomic location of intrahepatic portosystemic shunts (IHPSS) in dogs. Multi-institutional retrospective case series. Dogs (n=125) with IHPSS from the veterinary teaching hospitals of the University of Florida (21), Sydney University (44), and the University of California-Davis (60). Dogs with surgical/necropsy confirmation of single IHPSS were identified. Data were analyzed using logistic regression for associations between age, breed, sex, and country with the anatomic location of IHPSS. Right (34%), left (34%), and central divisional IHPSS (32%) were prevalent with approximately equal frequency in Australia; in the United States, the prevalence of right (24%) and central divisional (26%) combined was similar to left divisional IHPSS (51%). Country (P=048), sex (P=.016), and Australian cattle dog ([ACD], P=.025) were significantly associated with IHPSS location. Dogs in Australia had 2.5-fold higher odds of having right versus left divisional IHPSS. Males and ACD had 2.8- and 5.6-fold higher odds of having right versus left divisional IHPSS. Australian dogs were significantly older than those in the United States (P<.0001) and ACD were significantly older than other breeds (P=.0067). Although country of origin, breed, and sex had significant associations with anatomic location of IHPSS, signalment does not appear to be a strong predictor of shunt location when used alone. For the common breeds in this report, signalment is only occasionally helpful in predicting likelihood of anatomic division in IHPSS. Australian cattle dogs and male dogs have a statistical association with right (versus left) divisional IHPSS. If advanced imaging techniques are not available, veterinary surgeons should be prepared to locate and address any anatomic configuration of IHPSS in a dog.

A randomized, prospective, comparative study of manual and automated renal biopsies

Introduction: Glomerulonephropathies (GNs) have high burden of morbidity and mortality worldwide. The distribution GNs varies significantly due to several factors. Materials and Methods: This retrospective clinico-pathological study estimates the biopsy-proven distribution of primary and secondary GNs and detect s the predominant patterns among adult patients who underwent renal biopsy at Nephrology Centre, King Abdul-Aziz Specialist Hospital, Taif City, Kingdom of Saudi Arabia (KSA) from 2008 to 2013 with comparing data to other KSA studies and to other countries. Analysis of possible contributing factors for variation is provided. Relevant patients’ data were collected from hospital records. Renal biopsies stained with H&E, Periodic Acid Schiff (PAS), Gomori Methenamine Silver (GMS), Masson Trichrome (MT) and immunofluorescence (IF) were examined and categorized according to the World Health Organization (WHO) classification of glomerular diseases. Comparisons to other studies were set. Results: Primary and secondary GNs comprised 59.4% and 40.6%. Focal segmental glomerulosclerosis (FSGS) was the commonest primary GN (29.3%), followed by minimal change disease (MCD, 22%) then membranous glomerulonephropathy (MGN, 19.5%). IgA nephropathy was the least frequent (IgAN, 2.4%). Lupus nephritis (LN) was the commonest secondary GN (75%), followed by diabetic and vascular nephropathies (DN, 17.9% ; VN, 7.1%). Spatial and temporal variations in GNs distribution existed locally and worldwide. Conclusion: Factors including selection criteria; biopsy rate and indications; local facilities; demographic distribution; racial, ethnic and genetic differences; and prevalence of etiological factors contribute to the variations of GNs distribution. National renal biopsy registry is recommended for obtaining correct distribution of GNs leading to proper prevention and treatment. Keywords: Distribution, Glomerulonephropathy, Renal biopsy, FSGS, Lupus nephritis.

37-Year-Old Woman With Bilateral Lower Extremity Edema, Proteinuria, and Microscopic Hematuria

Serum proteomics reveals reduced serpin family A member 1 (SERPINA1) in primary FSGS, distinguishing it from other proteinuric kidney diseases. Serpina1 knockdown in zebrafish causes proteinuria and edema, supporting its functional relevance in glomerular disease. SERPINA1 may exert compartment-specific functions, and its decrease may permit protease activity to contribute to podocyte injury in primary FSGS. Primary FSGS (pFSGS) is caused by circulating permeability factors. Despite extensive efforts, no single causative factor or biomarker signature has been identified that reliably predicts disease or therapeutic outcomes across all patients. By using liquid chromatography-mass spectrometry-based proteomics on serum samples from patients with pFSGS, compared with controls, we aimed to identify disease-specific protein signatures. Liquid chromatography-mass spectrometry-based proteomics analysis was performed on 103 serum samples from 36 patients with pFSGS, 33 patients with other proteinuric diseases, and 34 healthy controls. Selected proteins found to be dysregulated in pFSGS were tested in cell culture experiments in immortalized human podocytes. Knockdown experiments were performed in zebrafish larvae, which were screened for proteinuria, edema, and podocyte marker expression. Immunofluorescent staining on zebrafish sections and patients' kidney biopsies was used to confirm findings. Mass spectrometry of sera from patients revealed a set of 27 proteins specifically affected in pFSGS, including a dysbalance of proteases and protease inhibitors. A subset of younger pFSGS patients with frequent relapses showed a distinct serum protein profile based on 23 dysregulated proteins. From proteomics results, serpin family A member 1 (SERPINA1; α-1-antitrypsin) was selected for further investigations. Urinary SERPINA1 increased across nephrotic syndromes, whereas serum SERPINA1 reduction was specific to pFSGS, suggesting a distinct underlying pathophysiology involving immune modulation, increased protease activity, or systemic depletion. Glomerular SERPINA1 expression was selectively increased in sclerotic lesions, likely reflecting a local compensatory response to protease stress. Podocytes constitutively secreted SERPINA1, with limited adaptive response under protease stress. Finally, systemic Serpina1 knockdown in zebrafish induced edema, proteinuria, and loss of slit diaphragm markers. Our findings support a causal and compartment-specific role of SERPINA1 and suggest that reduced circulating protease inhibitors may shift the local protease-antiprotease balance, potentially facilitating podocyte injury in pFSGS.

Phosphoenolpyruvate carboxykinase 1 (PCK1 or PEPCK-C) is a cytosolic enzyme converting oxaloacetate to phosphoenolpyruvate, with a potential role in gluconeogenesis, ammoniagenesis, and cataplerosis in the liver. Kidney proximal tubule cells display high expression of this enzyme, whose importance is currently not well defined. We generated PCK1 kidney-specific knockout and knockin mice under the tubular cell-specific PAX8 promoter. We studied the effect of PCK1 deletion and overexpression at the renal level on tubular physiology under normal conditions and during metabolic acidosis and proteinuric renal disease. PCK1 deletion led to hyperchloremic metabolic acidosis characterized by reduced but not abolished ammoniagenesis. PCK1 deletion also resulted in glycosuria, lactaturia, and altered systemic glucose and lactate metabolism at baseline and during metabolic acidosis. Metabolic acidosis resulted in kidney injury in PCK1-deficient animals with decreased creatinine clearance and albuminuria. PCK1 further regulated energy production by the proximal tubule, and PCK1 deletion decreased ATP generation. In proteinuric chronic kidney disease, mitigation of PCK1 downregulation led to better renal function preservation. PCK1 is essential for kidney tubular cell acid-base control, mitochondrial function, and glucose/lactate homeostasis. Loss of PCK1 increases tubular injury during acidosis. Mitigating kidney tubular PCK1 downregulation during proteinuric renal disease improves renal function.NEW & NOTEWORTHY Phosphoenolpyruvate carboxykinase 1 (PCK1) is highly expressed in the proximal tubule. We show here that this enzyme is crucial for the maintenance of normal tubular physiology, lactate, and glucose homeostasis. PCK1 is a regulator of acid-base balance and ammoniagenesis. Preventing PCK1 downregulation during renal injury improves renal function, rendering it an important target during renal disease.

Renal involvement in hepatitis C infection: Cryoglobulinemic glomerulonephritis