Evaluation of three scoring systems for predicting renal prognosis in antineutrophil cytoplasmic antibody-associated glomerulonephritis

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is characterized by rapidly progressive glomerulonephritis, and timely initiation of treatment and evaluation is critical to prevent the progression of renal disease to end-stage renal disease (ESRD). The aim of this study was to evaluate predictive value of the renal risk score (RRS), Birmingham vasculitis activity score (BVAS), and renal vascular lesions (RVLs) score for renal prognosis in AAGN.

METHODS

A retrospective analysis of ninety-four patients diagnosed with AAGN after renal biopsy was performed. The RRS, BVAS, and RVLs score were evaluated in relation to clinicopathologic features and renal prognosis. A receiver operating characteristic curve (ROC) was used to evaluate their renal prognostic value.

RESULTS

The median follow-up time was 36 months. Thirty-eight patients progressed to ESRD. Survival analysis showed that renal prognosis worsened in the RRS group in order of low, medium, and high RRS (P < 0.05). Within the RVLs group, the renal prognosis of the groups with severe and moderate RVLs was worse than that of the group without RVLs (P = 0.012, P < 0.001), and the group with mild RVLs was close to that of the group without RVLs. ROC analysis showed that the AUC of RRS, BVAS, RVLs score, RVLs score combined with RRS (RVLs score & RRS, RR), RVLs score, and RRS combined with BVAS (RVLs score & RRS & BVAS, RRB) were 0.865, 0.624, 0.763, 0.910, and 0.942, respectively. The predictive power of RRB and RR was comparable and significantly better than the RRS, BVAS, and RVLs score. Based on simplicity and validity, RR was selected as the best predictor, and the relationship between RRS, RVLs score, and RR was calculated using a linear fit, resulting in the linear equation RR = -0.4766 + 0.1231 × RVLs score + 0.395 × RRS (P < 0.001).

CONCLUSIONS

In AAGN, the predictive power of RR for renal prognosis was superior to that of RRS, BVAS, and RVLs score. RR may serve as a new predictor of renal prognosis in AAGN.

The molecular mechanisms of inflammation and scarring in the kidneys of immunoglobulin A nephropathy : Gene involvement in the mechanisms of inflammation and scarring in kidney biopsy of IgAN patients

Kidney biopsy is the cornerstone for the diagnosis of immunoglobulin A nephropathy (IgAN). The immunofluorescence technique evidences the IgA deposits in the glomeruli; the routine histology shows degree of active and chronic renal lesions. The spectrum of renal lesions is highly variable, ranging from minor or no detectable lesions to diffuse proliferative or crescentic lesions. Over the past three decades, renal transcriptomic studies have been performed on fresh or frozen renal tissue, and formalin-fixed paraffin-embedded kidney tissue specimens obtained from archival histological repositories. This paper aims to describe (1) the transcriptomic profiles of the kidney biopsy and (2) the potential urinary biomarkers that can be used to monitor the follow-up of IgAN patients. The use of quantitative Real-Time Polymerase Chain Reaction (qRT-PCR), microarrays and RNA-sequencing (RNA-seq) techniques on renal tissue and separated compartments of the nephron such as glomeruli and tubule-interstitium has clarified many aspects of the renal damage in IgAN. Recently, the introduction of the single-cell RNA-seq techniques has overcome the limitations of the previous methods, making that it is possible to study the whole renal tissue without the dissection of the nephron segments; it also allows better analysis of the cell-specific gene expression involved in cell differentiation. These gene products could represent effective candidates for urinary biomarkers for clinical decision making. Finally, some of these molecules may be the targets of old drugs, such as corticosteroids, renin-angiotensin-aldosterone blockers, and new drugs such as monoclonal antibodies. In the era of personalized medicine and precision therapy, high-throughput technologies may better characterize different renal patterns of IgAN and deliver targeted treatments to individual patients.

Genomic approaches in the search for molecular biomarkers in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is recognised as a global public health problem, more prevalent in older persons and associated with multiple co-morbidities. Diabetes mellitus and hypertension are common aetiologies for CKD, but IgA glomerulonephritis, membranous glomerulonephritis, lupus nephritis and autosomal dominant polycystic kidney disease are also common causes of CKD.

MAIN BODY

Conventional biomarkers for CKD involving the use of estimated glomerular filtration rate (eGFR) derived from four variables (serum creatinine, age, gender and ethnicity) are recommended by clinical guidelines for the evaluation, classification, and stratification of CKD. However, these clinical biomarkers present some limitations, especially for early stages of CKD, elderly individuals, extreme body mass index values (serum creatinine), or are influenced by inflammation, steroid treatment and thyroid dysfunction (serum cystatin C). There is therefore a need to identify additional non-invasive biomarkers that are useful in clinical practice to help improve CKD diagnosis, inform prognosis and guide therapeutic management.

CONCLUSION

CKD is a multifactorial disease with associated genetic and environmental risk factors. Hence, many studies have employed genetic, epigenetic and transcriptomic approaches to identify biomarkers for kidney disease. In this review, we have summarised the most important studies in humans investigating genomic biomarkers for CKD in the last decade. Several genes, including UMOD, SHROOM3 and ELMO1 have been strongly associated with renal diseases, and some of their traits, such as eGFR and serum creatinine. The role of epigenetic and transcriptomic biomarkers in CKD and related diseases is still unclear. The combination of multiple biomarkers into classifiers, including genomic, and/or epigenomic, may give a more complete picture of kidney diseases.

NLRP3 Localizes to the Tubular Epithelium in Human Kidney and Correlates With Outcome in IgA Nephropathy

Nod-like receptor pyrin domain-containing-3 (NLRP3) has been implicated in the pathogenesis of experimental renal injury, yet its characterization in human kidney disease remains largely unexplored. NLRP3 expression was evaluated in human kidney biopsies, primary renal tubular cells (HPTC) and correlated to disease outcomes in patients with IgA nephropathy (IgAN). NLRP3 localized to renal tubules in normal human kidney tissue and to mitochondria within HPTC by immunohistochemistry and immunofluorescence microscopy. Compared to control kidneys, NLRP3 gene expression was increased in biopsies of patients with IgAN. While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment. In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-β1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation. Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN. Taken together, these data show that NLRP3 is primarily a kidney tubule-expressed protein that decreases in abundance in progressive IgAN.

Significance of vasculopathy in IgA nephropathy patients with regard to Oxford classification and immunostaining findings: a single center experience

Introduction: immunoglobulin A nephropathy is the most common primary glomerulonephritis around the world. It remains poorly understood whether vascular pathology plays an important role in the progression of IgAN.

Objectives: Since very few studies regarding vascular disorders in IgAN are published, we aimed to evaluate the role of vascular disease in a group of IgAN patients, especially with regard to Oxford classification, immunostaining findings and various laboratory and clinical data.Patients and Methods: The study was conducted from July 2009 to March 2013. All kidney biopsies were prepared for light and immunofluorescence microscopy.

Results: Of the 136 patients, 94 (69%) were male. Of the 136 kidney biopsies, 37 patients had crescents, 2 had lesions of thrombotic microangiopathy (TMA), 10 had fibrinoid necrosis and one patient had morphologic lesions of small vessel vasculitis (with negative ANCA). In this study, there was no significant difference in scores of arteriolosclerosis and intimal fibrosis between males and females. There was a significant correlation between scores of arteriolosclerosis with serum creatinine. This correlation for scores of intimal fibrosis of interlobular artery was also significantly positive. The correlation of arteriolosclerosis with amount of proteinuria was significantly positive too.

Conclusion: The association of vasculopathy with serum creatinine and amount of proteinuria further support the role of vasculopathy in aggravation of IgAN. We also had different results with regard to the prevalence of TMA in previous published studies, which needs further investigation in larger series of IgAN patients.

Advanced IgA nephropathy with impaired renal function benefits from losartan treatment in rats

BACKGROUND

Treatment with angiotensin receptor blockers (ARBs) is successful in mitigating IgA nephropathy (IgAN), independent of blood pressure changes, but the therapeutic role of ARB in advanced IgAN with impaired renal function is to be ascertained. The present study was performed to investigate the effect of losartan on advanced IgAN induced by staphylococcal enterotoxin B (SEB) combined with 5/6 nephrectomy in rats.

METHODS

Fifty-four male SD rats were randomly divided into three group: Rats in the model group were treated with SEB plus 5/6 nephrectomy, and those in the losartan group were gavaged with losartan (33.3 mg kg(-1 )d(-1)) besides the treatment with SEB plus 5/6 nephrectomy. The urine and blood biochemical changes of rats were tested. IgA, IgG, IgM and C3 depositions were studied dynamically with immunofluorescence. The renal tissue structures were observed under light microscopy. The expressions of TGF-β1, FN, alpha-SMA and FGF-1 in rat renal tissues were determined with immunohistochemical methods and real-time PCR.

RESULTS

At 12 weeks, rats with SEB treatment plus 5/6 nephrectomy showed gradually increased urinary red blood cell (URBC) with a gradual elevation of the 24 h urinary protein, serum BUN and Scr, but losartan treatment lowered the levels of 24 h urinary protein, serum BUN and Scr. A large number of IgA depositions in the mesangial area, glomerulosclerosis and tubulointerstitial fibrosis were found in the model group, and the losartan group showed relieved injury. The expressions of TGF-β1, FN, alpha-SMA and FGF-1 were significantly elevated in the model. Losartan lessened their expressions.

CONCLUSION

Losartan treatment can delay the progression of advanced IgA nephropathy with impaired renal function.

Association of urinary laminin G-like 3 and free K light chains with disease activity and histological injury in IgA nephropathy

BACKGROUND AND OBJECTIVES

IgA nephropathy has variable clinical presentation and progression. Its definitive diagnosis and prognosis require renal biopsy. The identification of new biomarkers allowing noninvasive diagnosis and monitoring of disease activity would be advantageous. This study analyzed the urine proteome of IgA nephropathy patients at an early stage of disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine from 49 IgA nephropathy patients, 42 CKD patients, and 40 healthy individuals was analyzed by surface-enhanced laser desorption/ionization time of flight/mass spectrometry. Differentially excreted proteins were identified by matrix-enhanced laser desorption/ionization time of flight/mass spectrometry, confirmed by immunologic methods, and validated in an independent set of patients (14 IgA nephropathy and 24 CKD). All patients were recruited at the Division of Nephrology of the University of Foggia from January of 2005 to March of 2007.

RESULTS

Two proteins, with 21,598 and 23,458 m/z, were significantly decreased in IgA nephropathy and identified as Perlecan laminin G-like 3 peptide and Ig κ light chains, respectively. Western blot analysis confirmed the lower urinary excretion of laminin G-like 3 in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunonephelometry analysis confirmed the lower urinary excretion of free κ light chains in IgA nephropathy patients compared with CKD patients and healthy individuals. Immunohistochemistry analysis justified the urinary excretion profile of such proteins in IgA nephropathy. Finally, urinary free κ light chains and laminin G-like 3 concentration inversely correlated with severity of clinical and histologic features of our IgA nephropathy cohort.

CONCLUSIONS

Laminin G-like 3 and free κ light chains can contribute to the noninvasive assessment of IgA nephropathy disease activity.

The retrospective analysis of 343 Czech patients with IgA nephropathy--one centre experience

BACKGROUND

The aim of our study was to retrospectively analyse the clinical data and the histological findings of 343 patients (pts) followed up with IgA nephropathy (IgAN) in our department of nephrology. We have assessed the main demographic, clinical and histological data, and the medical treatment of IgAN pts.

METHODS

Multivariate analysis was used to evaluate the effect of different variables on ≥50% increase of plasma creatinine level from baseline during a median follow-up of 4 years.

RESULTS

In our group of IgAN pts, the male gender (68%) predominated over female gender (32%). At the time of renal biopsy, the median age of IgAN pts was 32.3 (18-90) years, the median level of serum creatinine was 119 μmol/L and the median level of proteinuria was 1.8 g/day. Most of the pts were found to have arterial hypertension (56.7%). The majority of the pts with arterial hypertension were treated with inhibitors of angiotensin-converting enzyme (80.4%) and the remaining pts (42.6%) were treated with angiotensin II receptor blockers. Fifty per cent of the pts (170 pts) were treated of corticosteroids, 21% of the pts (71 pts) used a combined immunosuppressive treatment of corticosteroids and cyclophosphamide, 8% of the pts (27 pts) took azathioprine, 1.5% of the pts (5 pts) took cyclosporine and 1.5% of the pts (5 pts) were given mycophenolate mofetil. Hypertension at presentation, fibrointimal proliferation of arterial vessels, interstitial fibrosis and interstitial inflammation were shown to be associated with ≥50% increase of plasma creatinine level from baseline in univariate analysis (P<0.05 for hypertension and fibrointimal proliferation; P<0.01 for interstitial fibrosis and inflammation). Using stepwise logistic regression presenting proteinuria>2 g/day [odds ratio (OR)=2.24, P<0.01], tubular atrophy (OR=4.97, P<0.01) and damage of tubular epithelium (OR=1.78, P<0.05) were found as risk factors for ≥50% increase of plasma creatinine level from baseline.

CONCLUSION

Our retrospective analysis found valuable information not only about the clinical, laboratory and histological findings in IgAN pts but also information about the risk factors influencing the progression of renal insufficiency.