IgA nephropathy

Increased Non-switched Memory B Cells are Associated with Plasmablasts, Serum IL-6 Levels and Renal Functional Impairments in IgAN Patients

Background: Circulating B cells are crucial for the pathogenesis of IgA nephropathy (IgAN). This study aimed at investigating the relationship between frequency of different subsets of circulating B cells and clinical measures in IgAN patients.Methods: The percentages of different subsets of circulating B cells in 23 IgAN patients and 14 healthy controls (HC) were determined by flow cytometry. Their serum IL-6 levels were measured by Cytometric Bead Array (CBA). Clinical parameters in five patients were measured before and after treatment for 8-12 weeks. The potential relationship between variants was analyzed.Results: In comparison with the HC, the frequency of CD3-CD19+ CD27+ IgD+IgM+ non-switched memory B cells (P = .0038) and CD3-CD19+ CD27hiCD38hi plasmablasts (P = .0467) and serum IL-6 (P = .0392) levels significantly increased in IgAN patients. The percentages of non-switched memory B cells were positively correlated with plasmablasts (R = 0.5781, P = .0039) and serum IL-6 levels (R = 0.6663, P = .0005) in the patients. The percentages of non-switched memory B cells (R = 0.8399, P < .0001), plasmablasts (R = 0.4486, P = .0318) and the levels of serum IL-6 (R = 0.5461, P = .0070) were positively correlated with the values of 24-h urine proteins in IgAN patients. The serum levels of IL-6 were negatively correlated with the eGFR values. Following standard treatment, the frequency of non-switched memory B cells and plasmablasts and the levels of 24-h urine proteins (P = .0317, P = .0079, P < .05) significantly decreased in IgAN patients.Conclusions: Abnormally higher frequency of non-switched memory B cells and plasmablasts may contribute to the pathogenesis of IgAN and be potential biomarkers for IgAN.

Clinical and pathological features of immunoglobulin A nephropathy patients with nephrotic syndrome

IgA nephropathy (IgAN) is the most common glomerulonephritis worldwide. The classic manifestation of IgAN is episodic hematuria and proteinuria. Nephrotic syndrome (NS) is not very common in IgAN, reported to occur in only 5-10% of IgAN patients. However, the clinical and pathological characteristics and long-term outcomes of patients with NS-IgAN at onset remain unknown. A retrospective study was conducted, enrolling 1165 patients with biopsy-proven IgAN from West China Hospital in 2008-2015. Patients with renal biopsy of minimal change disease with mesangial IgA deposits were excluded. The renal endpoint was defined as 50% decrease in eGFR or progressing into end-stage renal disease (ESRD). A total of 1165 patients were enrolled with average age of 34.58, and 171 (14.7%) patients were presented with NS. Comparing NS and non-NS groups, significance differences were shown in hypertension (HTN), 24-h urine protein, serum albumin, serum creatine, eGFR and uric acid. NS group had severe pathological changes such as endocapillary hypercellularity, tubular atrophy or interstitial fibrosis and crescent, but less segmental glomerulosclerosis or adhesion and global sclerosis. During the average follow-up of 44.27 months, 29.8% (51/171) NS patients and 15.8% (157/994) non-NS patients progressed to the renal endpoint. 5-year renal survival rates were 73.1% and 87.8% (P < 0.001) in NS and non-NS groups, respectively. This study demonstrated that IgAN patients with NS had higher serum creatine, lower eGFR, lower uric acid, more acute lesions and poor prognosis. NS was an independent risk factor for progression to the renal endpoint.

Efficacy and safety of leflunomide in IgA nephropathy: a systematic review and meta-analysis

BACKGROUND

The optimal therapy for immunoglobulin A nephropathy (IgAN) remains uncertain. Leflunomide (LEF) is an immunosuppressive drug which may reduce deposition of glomerular autoantibodies and immune complexes. Several clinical trials were designed to evaluate the efficacy of LEF, but their results were controversial.

METHODS

Ovid Medline, Embase, the Cochrane Library, PubMed, and CNKI were systematically searched. Search terms included ("glomerulonephritis" OR "nephritis") AND ("immunoglobulin A" OR "IgA") AND "leflunomide". Studies in which patients were diagnosed with IgAN based on renal biopsy were included. Studies needed to report clinical outcomes via either short- or long-term clinical examination, remission rate, or complication rate.

RESULTS

Forty-four studies encompassing 1802 patients were included, of which 35 were randomized controlled trials. Results of 24 h post-treatment urine protein tests and serum creatinine tests were significantly lower in patients treat with LEF and corticosteroids (CS) or valsartan (ACEI) (CS + LEF or CS + ACEI) compared with patients treated with CS or ACEI alone (P < 0.05). More patients treated with CS + LEF (31.2%) achieved complete remission (CR) than patients treated with CS alone (22.2%) (RR = 0.71, 95% CI 0.59-0.85, P < 0.05). Although there was no significant difference in CR between patients treated with cyclophosphamide and CS (CS + CTX) and those treated with CS + LEF, the complication rate in the former group was higher (28.4%) than in the latter one (11.4%) (RR = 2.46, 95% CI 1.47-4.13, P < 0.005).

CONCLUSION

LEF appears to improve renal function while decreasing loss of urine protein. Combination regimens including LEF were better and safer compared with CS or ACEI alone or combinations including CTX.

Noninvasive Urinary Monitoring of Progression in IgA Nephropathy

Standard methods for detecting and monitoring of IgA nephropathy (IgAN) have conventionally required kidney biopsies or suffer from poor sensitivity and specificity. The Kidney Injury Test (KIT) Assay of urinary biomarkers has previously been shown to distinguish between various kidney pathologies, including chronic kidney disease, nephrolithiasis, and transplant rejection. This validation study uses the KIT Assay to investigate the clinical utility of the non-invasive detection of IgAN and predicting the progression of renal damage over time. The study design benefits from longitudinally collected urine samples from an investigator-initiated, multicenter, prospective study, evaluating the efficacy of corticosteroids versus Rituximab for preventing progressive IgAN. A total of 131 urine samples were processed for this study; 64 urine samples were collected from 34 IgAN patients, and urine samples from 64 demographically matched healthy controls were also collected; multiple urinary biomarkers consisting of cell-free DNA, methylated cell-free DNA, DMAIMO, MAMIMO, total protein, clusterin, creatinine, and CXCL10 were measured by the microwell-based KIT Assay. An IgA risk score (KIT-IgA) was significantly higher in IgAN patients as compared to healthy control (87.76 vs. 14.03, p < 0.0001) and performed better than proteinuria in discriminating between the two groups. The KIT Assay biomarkers, measured on a spot random urine sample at study entry could distinguish patients likely to have progressive renal dysfunction a year later. These data support the pursuit of larger prospective studies to evaluate the predictive performance of the KIT-IgA score in both screening for non-invasive diagnosis of IgAN, and for predicting risk of progressive renal disease from IgA and utilizing the KIT score for potentially evaluating the efficacy of IgAN-targeted therapies.

Attenuated Macrophage Infiltration in Glomeruli of Aged Mice Resulting in Ameliorated Kidney Injury in Nephrotoxic Serum Nephritis

Senescent cells have deleterious effects on the tissue microenvironment through proinflammatory senescence-associated secretory phenotypes; meanwhile, the onset of glomerulonephritis is predominant in younger adults. To clarify the influence of aging on the onset and development of glomerulonephritis, we used a murine model of antibody-mediated nephritis. Sheep nephrotoxic serum was administered in C57BL/6J mice at 12 weeks (adult) or 18 months old (aged) after pre-immunization with sheep IgG. Depositions of sheep IgG and autologous mouse IgG along the glomerular basement membrane and the serum titer of anti-sheep IgG-specific mouse IgG were similar between adult and aged mice. However, kidney injury was depressed in aged mice, accompanied by reduced macrophage infiltration in the glomeruli. The mRNA expression of most chemokines involved in monocyte/macrophage chemotaxis was not different between adult and aged mice, but the cell surface expression of C-C chemokine receptor (CCR) 1 and CCR2 was down-regulated in the monocyte/macrophage lineage cells infiltrating the kidneys of aged nephritic mice. Furthermore, expression of all four isotypes of the Fcγ receptor (FcγR) was reduced in these cells. Both CCR and FcγR expression were down-regulated in monocyte/macrophage lineage cells, resulting in attenuated glomerular infiltration of these cells and impaired glomerular injury in aged mice.

Changes in the clinical presentation of immunoglobulin A nephropathy: data from the Spanish Registry of Glomerulonephritis

Background

Immunoglobulin A nephropathy (IgAN) is the most common glomerulonephritis in the world, but there is little epidemiological data about possible changes in its presentation over the years. Available information about the influence of age on the form of clinical presentation is also scarce.

Methods

The aim of the study was to analyse all renal biopsies performed between 1994 and 2013 and recorded in the Spanish Registry of Glomerulonephritis with a histological diagnosis of IgAN. The study was divided into five 4-year periods (1994-97, 1998-2001, 2002-05, 2006-09 and 2010-13) and patients were divided into four age groups: ≤16, 17-44, 45-64 and ≥65 years.

Results

From 20.974 renal biopsies recorded, 2961 (14.1%) corresponded to IgAN. The prevalence of IgAN remained stable, but a significant increase in age [from 37.6 (SD 17.7) in 1994-97 to 44.9 (SD 16.8) years in 2010-13; P = 0.001] and worse renal function at presentation [from serum creatinine (SCr) 1.9 (SD 1.9) in 1994-97 to 2.3 (SD 2.1) mg/dL in 2010-13; P = 0.001] were observed over the years. Nephrotic-range proteinuria and acute kidney injury (AKI) as forms of presentation were significantly more common among patients ≥65 years (17.7% and 43.2%, respectively) as compared with the other age groups [≤16 (11.4% and 13.1%, respectively), 17-44 (13.1% and 13%, respectively) and 45-64 (12.1% and 21.3%, respectively)]. Blood pressure, SCr and proteinuria were also significantly higher at presentation among elderly patients.

Conclusions

Although the prevalence of IgAN in Spain has remained stable over the years, patients are significantly older and present with significantly worse renal function in the last years. The incidence of nephrotic-range proteinuria (17.7%) and AKI (43.2%) as forms of presentation is remarkable among patients ≥65 years of age.

M2a and M2b macrophages predominate in kidney tissues and M2 subpopulations were associated with the severity of disease of IgAN patients

M2 macrophages play important roles during the injury and repair phases in kidney. Our aims are to investigate the distribution of M2 subpopulations and the correlation with clinicopathological features of IgA nephropathy (IgAN) patients. In this study, renal samples from 49 IgAN patients were detected by immunofluorescence. The markers of M2 macrophages, including M2a (CD206+/CD68+), M2b (CD86+/CD68+) and M2c (CD163+/CD68+) were identified. We found M2a and M2b macrophages were the predominant subpopulations in kidney tissues of IgAN. M2a macrophages were mainly distributed in tubulointerstitium with renal lesions like segmental glomerulosclerosis and tubular atrophy/interstitial fibrosis. However, there were larger numbers of M2c in glomeruli with minor lesions. Moreover, M2a and M2c macrophages were inversely correlated with the clinical and pathologic features, respectively. These results suggest M2 subpopulations were involved in the progression of IgAN, and M2a and M2c macrophages might show different properties to participate in the pathogenesis of IgAN.

Identification of primary genes in glomeruli compartment of immunoglobulin A nephropathy by bioinformatic analysis

The current study is aimed to explore the specific genes which are responsible for the manifestation of Immunoglobulin A nephropathy (IgAN). Gene expression profiles GSE37460, GSE93798 and GSE104948 were analyzed using biological informatics methods to identify differentially expressed genes (DEGs) in IgAN glomeruli samples which were then compared to normal control samples. Subsequently, the DEGs were overlapped to explore genes with significant expression in at least two profiles. Finally, the enrichment analysis was conducted and the protein-protein interaction (PPI) network was constructed for the overlapping DEGs. A total of 28 genes were up-regulated and 10 genes were down-regulated. The up-regulated genes including CD44 and FN1 were chiefly involved in extracellular matrix receptors interaction pathway. In addition, CX3CR1 and CCL4 were associated with chemokine signaling pathway. ITGB2, PTPRC, FN1, and FCER1G were hub genes with a high degree of interaction in the PPI network. Therefore, this study identified many significant genes associated with extracellular matrix expansion and inflammatory mechanism which may be the novel biomarker and target candidates in IgAN.

Evaluating a New International Risk-Prediction Tool in IgA Nephropathy

IMPORTANCE

Although IgA nephropathy (IgAN) is the most common glomerulonephritis in the world, there is no validated tool to predict disease progression. This limits patient-specific risk stratification and treatment decisions, clinical trial recruitment, and biomarker validation.

OBJECTIVE

To derive and externally validate a prediction model for disease progression in IgAN that can be applied at the time of kidney biopsy in multiple ethnic groups worldwide.

DESIGN, SETTING, AND PARTICIPANTS

We derived and externally validated a prediction model using clinical and histologic risk factors that are readily available in clinical practice. Large, multi-ethnic cohorts of adults with biopsy-proven IgAN were included from Europe, North America, China, and Japan.

MAIN OUTCOMES AND MEASURES

Cox proportional hazards models were used to analyze the risk of a 50% decline in estimated glomerular filtration rate (eGFR) or end-stage kidney disease, and were evaluated using the R2D measure, Akaike information criterion (AIC), C statistic, continuous net reclassification improvement (NRI), integrated discrimination improvement (IDI), and calibration plots.

RESULTS

The study included 3927 patients; mean age, 35.4 (interquartile range, 28.0-45.4) years; and 2173 (55.3%) were men. The following prediction models were created in a derivation cohort of 2781 patients: a clinical model that included eGFR, blood pressure, and proteinuria at biopsy; and 2 full models that also contained the MEST histologic score, age, medication use, and either racial/ethnic characteristics (white, Japanese, or Chinese) or no racial/ethnic characteristics, to allow application in other ethnic groups. Compared with the clinical model, the full models with and without race/ethnicity had better R2D (26.3% and 25.3%, respectively, vs 20.3%) and AIC (6338 and 6379, respectively, vs 6485), significant increases in C statistic from 0.78 to 0.82 and 0.81, respectively (ΔC, 0.04; 95% CI, 0.03-0.04 and ΔC, 0.03; 95% CI, 0.02-0.03, respectively), and significant improvement in reclassification as assessed by the NRI (0.18; 95% CI, 0.07-0.29 and 0.51; 95% CI, 0.39-0.62, respectively) and IDI (0.07; 95% CI, 0.06-0.08 and 0.06; 95% CI, 0.05-0.06, respectively). External validation was performed in a cohort of 1146 patients. For both full models, the C statistics (0.82; 95% CI, 0.81-0.83 with race/ethnicity; 0.81; 95% CI, 0.80-0.82 without race/ethnicity) and R2D (both 35.3%) were similar or better than in the validation cohort, with excellent calibration.

CONCLUSIONS AND RELEVANCE

In this study, the 2 full prediction models were shown to be accurate and validated methods for predicting disease progression and patient risk stratification in IgAN in multi-ethnic cohorts, with additional applications to clinical trial design and biomarker research.

Immunoglobulin A Nephropathy. Recurrence After Renal Transplantation

IgA nephropathy (IgAN) is the most common primary glomerular disease worldwide. The disease generally runs an indolent course but may lead to ESRD in 20-30% of patients in 20 years or more after diagnosis. Patients with IgA nephropathy are ideal candidates for renal transplant because they are generally relatively young and with few comorbidities. Their graft survival is better or comparable to that of controls at 10 years, though few data are available after 10 years of follow-up. Recurrence of the original disease in the graft is a well-known complication of transplant in IgAN and is a significant cause of deterioration of graft function. Recurrent IgAN rarely manifests clinically before 3 years post transplantation. Recurrence rate is estimated to be around 30% with considerable differences among different series. Despite these factors there is no certain recurrence predictor, young age at renal transplant, rapid progression of the original disease and higher levels of circulating galactose-deficient IgA1 and IgA-IgG immune complexes are all associated with a higher rate of recurrence. Which pathogenetic mechanisms are responsible for the progression of the recurrence to graft function deterioration, and what therapy can prevent or slow down the progression of the disease in the graft, are open questions. The aim of this review is to describe the clinical outcome of renal transplantation in IgA patients with attention to the rate and the predictors of recurrence and to discuss the available therapeutic options for the management of recurrence.

Osteopontin Gene Polymorphism and Urinary OPN Excretion in Patients with Immunoglobulin A Nephropathy

Osteopontin (OPN) is a glycoprotein involved in the pathogenesis of multiple autoimmune and inflammatory conditions. However, the association of variants of secreted phosphoprotein 1 gene (SPP1), which encodes OPN, with immunoglobulin A nephropathy (IgAN) has not been examined up to date. Moreover, the role of OPN in disease pathogenesis and clinical manifestations is not fully known. Therefore, the aim of the study was to determine the frequency of four single nucleotide polymorphisms (SNiPs) of SPP1 gene, as well as the urinary OPN excretion in IgAN patients and healthy controls. In total, 58 Caucasian patients with biopsy-proven IgAN and 184 gender-, age-, and ethnically-matched healthy controls were genotyped for rs1126616, rs1126772, rs9138, and rs7687316/rs3841116 polymorphisms by real time polymerase chain reaction (RT-PCR). Urinary OPN concentration was determined by enzyme-linked immunosorbent assay (ELISA) in 58 IgAN patients and 19 controls. SPP1 SNiPs, as well as urinary OPN excretion, were analyzed in relation to their possible associations with the clinicopathological parameters. The frequency of the minor TT/CT genotypes of rs1126616 was significantly higher in IgAN patients compared to controls (P = 0.0217). Similarly, the minor (CC/AC) genotypes and the C allele of rs9138 were more frequent in IgAN patients (P = 0.0425 and P = 0.0112, respectively). Moreover, these two SNiPs were associated with the higher urinary OPN excretion (P < 0.05). These findings suggest that rs1126616, as well as rs9138, may be associated with IgAN development, however future studies in this field are required.

Lisinopril versus lisinopril and losartan for mild childhood IgA nephropathy: a randomized controlled trial (JSKDC01 study)

BACKGROUND

Persistent proteinuria seems to be a risk factor for progression of renal disease. Its reduction by angiotensin-converting inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) is renoprotective. Our previous pilot study showed that 2-year lisinopril therapy is effective and safe for children with mild IgA nephropathy. When combined with ACEI and ARB, reported results are of greater decrease in proteinuria than monotherapy in chronic glomerulonephritis, including IgA nephropathy. To date, however, there have been no randomized controlled trials in children.

METHODS

This is an open-label, multicenter, prospective, and randomized phase II controlled trial of 63 children with biopsy-proven proteinuric mild IgA nephropathy. We compared efficacy and safety between patients undergoing lisinopril monotherapy and patients undergoing combination therapy of lisinopril and losartan to determine better treatment for childhood proteinuric mild IgA nephropathy.

RESULTS

There was no difference in proteinuria disappearance rate (primary endpoint) between the two groups (cumulative disappearance rate of proteinuria at 24 months: 89.3% vs 89% [combination vs monotherapy]). Moreover, there were no significant differences in side effects between the two groups.

CONCLUSIONS

We propose lisinopril monotherapy as treatment for childhood proteinuric mild IgA nephropathy as there are no advantages of combination therapy.

CLINICAL TRIAL REGISTRATION

Clinical trial registry, UMIN ID C000000006, https://www.umin.ac.jp .

Urinary microRNA in kidney disease: utility and roles

MicroRNAs (miRNAs) are small, noncoding single-stranded RNA oligonucleotides that modulate physiological and pathological processes by modulating target gene expression. Many miRNAs display tissue-specific expression patterns, the dysregulation of which has been associated with various disease states, including kidney disease. Mounting evidence implicates miRNAs in various biological processes, such as cell proliferation and differentiation and cancer. Because miRNAs are relatively stable in tissue and biological fluids, particularly when carried by extracellular vesicles, changes in their levels may reflect the development of human disease. Urinary miRNAs originate from primary kidney and urinary tract cells, cells infiltrating the renal tissue and shed in the urine, or the systemic circulation. Although their validity as biomarkers for kidney disease has not been fully established, studies have been applying analysis of miRNAs in the urine in an attempt to detect and monitor acute and chronic renal diseases. Because appreciation of the significance of miRNAs in the renal field is on the rise, an understanding of miRNA pathways that regulate renal physiology and pathophysiology is becoming critically important. This review aims to summarize new data obtained in this field of research. It is hoped that new developments in the use of miRNAs as biomarkers and/or therapy will help manage and contain kidney disease in affected subjects.

Role of Mesangial-Podocytic-Tubular Cross-Talk in IgA Nephropathy

IgA nephropathy (IgAN), a common primary glomerulonephritis worldwide, is associated with a substantial risk of progression to end-stage renal failure. The disease runs a highly variable clinical course with frequent involvement of tubulointerstitial damage. A subgroup of IgAN with proximal tubular epithelial cells (PTECs) and tubulointerstitial damage often is associated with rapid progression to end-stage renal failure. Human mesangial cell-derived mediators lead to podocyte and tubulointerstitial injury via mesangial-podocytic-tubular cross-talk. Although mesangial-podocytic communication plays a pathogenic role in podocytic injury, the implication of a podocyte-PTEC cross-talk pathway in the progression of tubulointerstitial injury in IgAN should not be underscored. We review the role of mesangial-podocytic-tubular cross-talk in the progression of IgAN. We discuss how podocytopathy in IgAN promotes subsequent PTEC dysfunction and whether tubulointerstitial injury affects the propagation of podocytic injury in IgAN. A thorough understanding of the cross-talk mechanisms among mesangial cells, podocytes, and PTECs may lead to better design of potential therapeutic options for IgAN.

Mortality in IgA Nephropathy: A Nationwide Population-Based Cohort Study

BACKGROUND

The clinical course of IgA nephropathy (IgAN) varies from asymptomatic nonprogressive to aggressive disease, with up to one in four patients manifesting ESRD within 20 years of diagnosis. Although some studies have suggested that mortality appears to be increased in IgAN, such studies lacked matched controls and did not report absolute risk.

METHODS

We conducted a population-based cohort study in Sweden, involving patients with biopsy-verified IgAN diagnosed in 1974-2011; main outcome measures were death and ESRD. Using data from three national registers, we linked 3622 patients with IgAN with 18,041 matched controls; we also conducted a sibling analysis using 2773 patients with IgAN with 6210 siblings and a spousal analysis that included 2234 pairs.

RESULTS

During a median follow-up of 13.6 years, 577 (1.1%) patients with IgAN died (10.67 per 1000 person-years) compared with 2066 deaths (0.7%) in the reference population during a median follow-up of 14.1 years (7.45 per 1000 person-years). This corresponded to a 1.53-fold increased risk and an absolute excess mortality of 3.23 per 1000 person-years (equaling one extra death per 310 person-years) and a 6-year reduction in median life expectancy. Similar increases in risk were seen in comparisons with siblings and spouses. IgAN was associated with one extra case of ESRD per 54 person-years. Mortality preceding ESRD was not significantly increased compared with controls, spouses, or siblings. Overall mortality did not differ significantly between patients with IgAN-associated ESRD and patients with ESRD from other causes.

CONCLUSIONS

Patients with IgAN have an increased mortality compared with matched controls, with one extra death per 310 person-years and a 6-year reduction in life expectancy.

Urinary angiostatin: a novel biomarker of kidney disease associated with disease severity and progression

Background

This study aimed to evaluate the value of urinary angiostatin levels for assessing disease severity and progression of IgA nephropathy (IgAN).

Methods

Urinary angiostatin was identified as one of the distinct proteins in samples of patients with IgAN analyzed by Raybiotech protein array, and further confirmed by enzyme-linked immunosorbent assay (ELISA).

Results

Urinary angiostatin levels were significantly higher in IgAN patients than that in healthy controls (HC) subjects and lower than in disease controls (DC) patients. The concentrations of angiostatin in urine normalized to urinary creatinine (angiostatin/Cr) were positively associated with proteinuria level. With advancing chronic kidney disease (CKD) stage, urinary angiostatin/Cr levels were gradually increased. Urinary angiostatin/Cr levels in patients with Lee’s grade IV–V were significantly higher than those in Lee’s grade I–II and III. We further compared urinary angiostatin/Cr levels by using Oxford classification and found the expression in patients with mesangial proliferative score 1(M1) was significantly higher than that in M0 (P < 0.001). In addition, the levels of urinary angiostatin/Cr in patients with tubular atrophy/interstitial fibrosis score 1(T1) and T2 were significantly higher than those in T0 (P < 0.01, P < 0.001, respectively). After follow-up, renal survival was significantly worse in patients with higher levels of urinary angiostatin (P < 0.05).

Conclusions

Urinary angiostatin may be a useful novel noninvasive biomarker to evaluate disease severity and progression of IgAN.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1305-2) contains supplementary material, which is available to authorized users.

Serum C3/C4 ratio is a novel predictor of renal prognosis in patients with IgA nephropathy: a retrospective study

IgA nephropathy (IgAN) is an autoimmune disease associated with complement activation. It is unclear whether the ratio of serum C3 and C4 concentrations (C3/C4 ratio) can predict renal outcomes in IgAN patients. A total of 1503 patients diagnosed with IgAN via renal biopsy were recorded in this study. Poor renal outcomes were defined as > 50% decrease in the baseline estimated glomerular filtration rate (eGFR) or development of end-stage renal disease (ESRD) during follow-up. In total, 712 patients meeting the exclusion/inclusion criteria were selected, and the mean follow-up period was 40.6 (12.34) months. Patients with decreased C3/C4 ratios displayed significantly more severe clinical characteristics and renal pathological features and a higher proportion of poor renal outcomes and ESRD. The optimal multivariate Cox regression models identified the C3/C4 ratio (hazard ratio (HR) 0.63, 95% CI 0.5-0.9), serum uric acid (HR 1.58, 95% CI 1.2-2.2), serum creatinine (HR 1.3, 95% CI 1.1-1.6), systolic blood pressure (HR 1.57, 95% CI 1.2-2.0) and T score (relative to T0, T1: HR 1.96, 95% CI 1.1-3.7, T2: HR 3.03, 95% CI 1.6-5.9) as strong predictors of poor renal outcomes. Subgroup analysis showed that patients with low C3/C4 ratios benefited from glucocorticoids or other immunosuppressive agents (hazard ratio 0.30 and 0.18, 95% CI 0.13-0.72 and 0.07-0.46, respectively). Serum C3/C4 ratios may be an independent novel predictor of renal outcomes in IgAN patients. Decreased C3/C4 ratios suggest poor renal outcomes and the potential to benefit from aggressive immunosuppressive therapies.

Clinical impact of endocapillary proliferation with modified cutoff points in IgA nephropathy patients

Predictive values of mesangial proliferation (M), endocapillary proliferation (E), segmental glomerulosclerosis (S), and crescents (C) among 19 validation studies of the Oxford Classification of IgA nephropathy (IgAN) were discrepant, especially in Asian patients. These validation studies indicate that cutoffs of MESC score in the Oxford Classification may not be generalizable. Thus, we aimed to improve the clinical value of MESC scores by modifying the cutoff points. A total of 104 patients with IgAN were diagnosed from 2001 to 2012 vai renal biopsy and retrospectively evaluated at Nagoya University Hospital. The cutoff point for modified (M´E´S´C´) was determined using the receiver operating characteristic curve in association with renal outcome in the training cohort. Clinical values of the Oxford MESTC vs M´E´S´C´ cutoff points were analyzed using Kaplan-Meier and Cox regression in association with poor renal outcome in the validation and the entire cohort. Of 104 patients, 12.5% reached poor renal outcome over a median of 6.25 [4.16–9.61] years of follow-up. The modified cutoffs were defined as ≥40%, ≥10%, ≥20%, and ≥5% in the glomeruli for M´E´S´, and C´ respectively. In univariate analysis, E´, S ´, and T were significantly associated with poor renal outcome, whereas Oxford MESC, M´, and C´ in the training and validation cohort were not associated with poor renal outcome. Using multivariate analysis in the presence of estimated glomerular filtration rate (eGFR), only E´ was a significant predictive factor for poor renal outcome. The E´ with modified cutoff point of 10% significantly improved predictive value for poor renal outcome in IgAN. Therefore, the clinical value of modified cutoff points for M´E´S´C´ scores should be validated with various cohort studies in different regions.

Efficacy and safety of glucocorticoids for patients with IgA nephropathy: a meta-analysis

BACKGROUND

The efficacy and safety of glucocorticoids for the treatment of patients with IgA nephropathy (IgAN) remains controversial. The aim of the study is to perform a metaanalysis of randomized controlled trials to evaluate the efficacy and safety of glucocorticoids for patients with IgAN.

METHODS

We searched PubMed, EMBASE and the Cochrane Library and article reference lists of Controlled Trials, and Clinical Trial Registries for randomized controlled trials comparing glucocorticoids with other non-immunosuppressive agents in patients with IgAN.

RESULTS

The present meta-analysis, including 10 RCTs and 791 patients from 12 published studies, showed that using glucocorticoids agents relatively preserves kidney function(RR 0.06, 95% CI 0.14-0.61) and plays an effective role on reducing the proteinuria(SMD, - 0.69; 95% CI 0.85 to - 0.53, p < 0.00001; heterogeneity I2 = 0%; p = 0.09) compared with a control group. Moreover, adverse events cannot be neglected, especially gastrointestinal tract (RR 3.10, 95% CI 1.37-6.98, p = 0.006; heterogeneity I2 = 0%, p = 0.86), and corticosteroid regimens in IgAN should be reviewed with regard to safety.

CONCLUSIONS

Glucocorticoids were wildly used to treat various diseases including IgAN. Meanwhile, adverse events cannot be neglected, such as gastrointestinal adverse events, infection and so on. Corticosteroid should be used with reserve, especially in those patients with hypertension and impaired renal function or older patients.

Urinary miRNA profile for the diagnosis of IgA nephropathy

Background

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Urinary micro-RNA (miRNA) level is increasingly reported to as non-invasive markers of various kidney diseases. We aim to identify urinary miRNA targets for the diagnosis of IgAN.

Methods

In the development cohort, we performed complete miRNA profiling of urinary sediment in 22 patients with IgAN and 11 healthy controls (CTL). Potential miRNA targets were quantified by a separate validation cohort of 33 IgAN patients and 9 healthy controls.

Results

In the development cohort, we identified 39 miRNA targets that have significantly different expression between IgAN and CTL (14 up-regulated, and 25 down-regulated). Among the 8 miRNA targets chosen for validation study, urinary miR-204, miR-431 and miR-555 remained significantly reduced, and urinary miR-150 level was significantly increased in the IgAN as compared to CTL. The area-under-curve of the receiver operating characteristic (ROC) curve for urinary mi-204 level for the diagnosis of IgAN was 0.976, and the diagnostic performance of combining additional miRNA targets was not further improved. At the cut-off 1.70 unit, the sensitivity and specificity of urinary miR-204 was 100 and 55.5%, respectively, for diagnosing IgAN.

Conclusions

Urinary miR-150, miR-204, miR-431 and miR-555 levels are significantly different between IgAN and healthy controls; urinary miR-204 level alone has the best diagnostic accuracy.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1267-4) contains supplementary material, which is available to authorized users.

Clinical Significance of Crescent Formation in IgA Nephropathy – a Multicenter Validation Study

Background/Aims: Additional validation study was warranted to confirm the clinical significance of C score, which was recently added to the Oxford classification for immunoglobulin A nephropathy (IgAN). Methods: We performed a multicenter retrospective cohort study in four hospitals in Korea. Patients who had biopsied glomeruli less than eight or inadequate follow-up information were excluded. Clinicopathologic parameters, including the degree of cellular or fibrocellular crescents, were collected and included in multivariable models for Cox regression analysis. The main outcome was a composite renal outcome, defined as a merge of progression to end-stage renal disease (ESRD) and halving of estimated glomerular filtration rate (eGFR) from baseline. Results: Among included 3,380 biopsy-confirmed IgAN patients, there were 664 (19.6%) patients with C1 and 60 (1.8%) patients with C2 scores in the study population. Although C0 and C1 patients shared similar baseline characteristics, C2 patients frequently had more clinicopathologic risk factors for poor prognosis of IgAN. Both C1 [adjusted HR 1.33 (1.11-1.58), P=0.002] and C2 [adjusted HR 2.24 (1.46-3.43), P< 0.001] scores were associated with an increased risk of the composite outcome. C2 was a strong predictive parameter associated with both progression to ESRD and halving of eGFR, whereas C1 was mainly associated with the increased risk of halving of eGFR. Notably, the proportion of crescent showed a linear association with the risk of adverse renal outcome. Conclusion: The C score in the Oxford classification is a valid predictive parameter for IgAN prognosis. Additional clinical attention is necessary for IgAN patients with identified cellular or fibrocellular crescents.

Significance of subepithelial deposits in patients diagnosed with IgA nephropathy

Subepithelial deposits are observed in rare adult IgA nephropathy (IgAN) cases and are a key diagnostic finding in IgA-dominant infection-related glomerulonephritis (IgA-IRGN). Sometimes, it is difficult to distinguish IgA-IRGN from IgAN without a precise clinical history. We hypothesized that some IgA-IRGN cases might be diagnosed as IgAN with subepithelial deposits (IgAN-SD) and aimed to clarify the significance of subepithelial deposits in patients diagnosed with IgAN. We examined 464 patients diagnosed with IgAN at Nagasaki University Hospital and affiliated hospitals between 1996 and 2013. The differences in clinicopathological findings between IgAN-SD and IgAN with no subepithelial deposits (IgAN-NSD) were investigated. In addition to clinical data and typical IgAN pathological features, we analyzed complement levels, immunoglobulin localization, light chain staining patterns, and intramembranous deposits. There were 214 men and 250 women with a mean age of 38.8 ± 18.3 years. Subepithelial deposition was observed in 51 patients (11%). Compared to patients with IgAN-NSD, those with IgAN-SD had significantly lower mean serum protein (6.4 g/dL vs. 6.7 g/dL; p = 0.02), albumin (3.7 g/dL vs. 3.9 g/dL; p = 0.02), and complement (C3) (94 mg/dL vs. 103 mg/dL; p = 0.02) levels. Diffuse mesangial hypercellularity (M) (65% vs. 45%; p<0.01), endocapillary hypercellularity: (E) (43% vs. 28%; p = 0.03), and IgA staining in the glomerular capillary wall (22% vs. 8%; p<0.01) were more common in patients with IgAN-SD. The incidence of light chain lambda predominance was lower in patients with IgAN-SD (47% vs. 63%; p = 0.03). Hump-shaped subepithelial deposits and intramembranous deposits were observed in nine and 17 patients with IgAN-SD, respectively. Patients with IgAN-SD tended to have the characteristics of IgA-IRGN rather than IgAN-NSD. Since the therapeutic strategies for IgA-IRGN differ from those for IgAN, we should review the clinical history and pay careful attention to the clinical course in cases with atypical findings, such as subepithelial deposits.

Immunoglobulin A nephropathy secondary to Wilson's disease: a case report and literature review

Immunoglobulin A nephropathy is the most common primary glomerulonephritis worldwide, and it can be associated with liver disease. However, cases of Immunoglobulin A nephropathy secondary to Wilson's disease are very rare. A 20-year-old Japanese man presented with microscopic hematuria, proteinuria, and renal dysfunction. A renal biopsy showed mesangial cell proliferation, immunoglobulin A deposition, and electron-dense deposit in the mesangial areas, all of which are consistent with Immunoglobulin A nephropathy. Computed tomography of the abdomen showed liver atrophy and splenomegaly, and the diagnosis of Wilson's disease was confirmed with decreased serum ceruloplasmin levels, increased urinary copper excretion, Kayser-Fleischer rings and copper deposition in the liver biopsy. The patient was treated successfully with trientine hydrochloride and zinc acetate and showed improvement in renal manifestations. Wilson's disease is a rare cause of secondary Immunoglobulin A nephropathy. We recommend that Wilson's disease should be considered the cause of secondary Immunoglobulin A nephropathy in juvenile patients with hematuria, proteinuria, and splenomegaly and suggest measuring the serum ceruloplasmin concentrations, urinary copper excretion, and evaluating Kayser-Fleischer rings in these patients.

IgA nephropathy with diffuse alveolar haemorrhage

Immunoglobulin (Ig)A nephropathy is the most common cause of primary glomerulonephritis worldwide. While IgA nephropathy has been associated with a variety of other diseases, pulmonary complications are extremely rare. A 58-year-old man presented with a 2-week history of fever and exertional dyspnoea. A chest imaging revealed bilateral consolidation predominantly in upper lungs. Laboratory findings showed elevated serum creatinine with proteinuria and haematuria. Flexible bronchoscopy revealed diffuse alveolar haemorrhage, and IgA nephropathy was confirmed on a renal biopsy. He received prednisone with good effect. This case highlights the need to consider IgA nephropathy in the differential diagnosis of pulmonary renal syndrome.

Analysis of the differential urinary protein profile in IgA nephropathy patients of Uygur ethnicity

Background

IgA nephropathy (IgAN) is one of the most common forms of idiopathic glomerular diseases and might lead to end-stage kidney disease. Accurate and non-invasive biomarkers for early diagnosis are required for early intervention and consequent therapy for IgAN patients. Because variance in the disease incidence and predisposing genes of IgAN has been detected among different ethnicities, the ethnicity factor should be considered in IgAN biomarker discovery. The differences in the protein profiles and pathological mechanisms of IgAN in patients of Uygur ethnicity need to be clearly illustrated.

Methods

In this study, we used urinary proteomics to discover candidate biomarkers of IgAN in patients of Uygur ethnicity. The urinary proteins from Uygur normal control and Uygur IgAN patients were extracted and analyzed using 2D-LC-MS/MS and isobaric tags for relative and absolute quantitation (iTRAQ) analysis.

Results

A total of 277 proteins were found to be differentially represented in Uygur IgAN compared with the respective normal controls. The bioinformatics analysis revealed that the immune response, cell survival, and complement system were activated in Uygur IgAN. Many differentially expressed proteins were found to be related to nephropathy and kidney injuries. Four candidate biomarkers were validated by Western blot, and these results were consistent with the iTRAQ results. ICAM1, TIMP1, SERPINC1 and ADIPOQ were upregulated in Uygur IgAN. Bioinformatic analysis revealed that the increase of ICAM1 and TIMP1 might be caused by IgAN, but the increase of SERPINC1 and ADIPOQ might be caused by proteinuria. SERPINC1 and ICAM1 were identified as the candidate biomarkers with excellent area-under-the-curve (AUC) values (0.84) for distinguishing Uygur IgAN from normal controls.

Conclusions

Using urinary proteomic analysis, we identified several candidate biomarkers for IgAN in patients of Uygur ethnicity. These results will prove helpful for exploring the pathological mechanism of IgAN in patients of Uygur ethnicity and for developing better treatments for these patients.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1139-3) contains supplementary material, which is available to authorized users.

Interleukin 18 -607 A/C Gene Polymorphism is Associated With Susceptibility to IgA Nephropathy in a Chinese Han Population

The association between a single-nucleotide polymorphism (SNP; -607A/C) in the promoter region of the IL-18 gene with IL-18 promoter transcription activity and the level of IL-18 protein production has been observed repeatedly. However, the association between the IL-18-607A/C (rs1946518) promoter polymorphism and IgA nephropathy (IgAN) in a Chinese Han population is still unclear. A total of 166 patients with renal biopsy-proven IgAN and 198 healthy controls were recruited for this study. The SNP was genotyped by the polymerase chain reaction and the high-resolution melting method. Clinical characteristics and pathology grading of patients with IgAN were recorded at the time of the kidney biopsy. There was a significant difference in the distribution between the AA genotype and the AC/CC genotype [P=0.007, OR (95% CI)=1.885 (1.183-3.003)]. However, no significant differences were observed between the rs1946518 SNP and quantitative traits (all P>0.05) or different pathology grades (Lee's grading system and tubular atrophy/interstitial fibrosis according to the Oxford classification) (P=0.769 and P=0.7) of the patients. We first demonstrated that the AA genotype of the IL-18-607A/C was associated with an increased susceptibility to IgAN in this population.

Serum levels of tumor necrosis factor alpha in patients with IgA nephropathy are closely associated with disease severity

Background

Tumor necrosis factor alpha (TNF-α) is considered to play an important role in the pathogenesis in IgA nephropathy (IgAN). The correlations between serum TNF-α and disease severity in patients with IgAN remain controversial.

Methods

Concentrations of serum TNF-α of 147 patients with IgAN and 126 healthy subjects were measured by chemiluminescence immunoassay. Correlations with clinicopathological features of patients with IgAN were evaluated.

Results

Serum levels of TNF-α [9.20 (7.70–10.60) pg/mL vs. 6.04 (5.11–7.23) pg/mL, P < 0.0001] were higher in patients with IgAN than that in healthy subjects. Receiver operating characteristic curve analysis revealed that TNF-α had better discrimination between patients with IgAN and healthy controls than estimated glomerular filtration rate [TNF-α: (AUC, 0.87; 95% CI, 0.83–0.91; P < 0.0001) vs. estimated glomerular filtration rate: (AUC, 0.76; 95% CI, 0.71–0.82; P < 0.0001), P = 0.007]. Multivariate linear regression analyses showed that serum levels of TNF-α were positively correlated with 24-h urine protein excretion (r = 0.33, P = 0.04), urinary protein to serum creatinine ratio (r = 0.33, P = 0.03), serum creatinine (r = 0.46, P < 0.0001) and Cystatin C (r = 0.59, P < 0.0001) in IgAN and negatively correlated with estimated glomerular filtration rate (r = − 0.49, P < 0.0001) after adjustment for sex, systolic blood pressure and diastolic blood pressure. Patients with higher mesangial hypercellularity or tubular atrophy/interstitial fibrosis score according to Oxford classification showed higher serum levels of TNF-α.

Conclusions

Our data showed that serum levels of TNF-α detected by chemiluminescence immunoassay was a potential biomarker for evaluating the disease severity in IgAN.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1069-0) contains supplementary material, which is available to authorized users.

Assessment of active tubulointerstitial nephritis in non-scarred renal cortex improves prediction of renal outcomes in patients with IgA nephropathy

Background

The addition of tubulointerstitial inflammation to the existing pathological classification of IgA nephropathy (IgAN) is appealing but was previously precluded due to reportedly wide inter-observer variability. We report a novel method to score percentage of non-atrophic renal cortex containing active tubulointerstitial inflammation (ATIN) in patients with IgAN and assess its utility to predict clinical outcomes.

Methods

All adult patients with a native renal biopsy diagnosis of IgAN between 2010 and 2015 in a unit serving 1.5 million people were identified. Baseline characteristics, biopsy reports and outcome data were collected. ATIN was calculated by subtracting the percentage of atrophic cortex from the percentage of total cortex with tubulointerstitial inflammation, with ≥10% representing significant ATIN. The primary outcome was a composite of requiring renal replacement therapy or doubling of serum creatinine.

Results

In total 153 new cases of IgAN were identified, of which 111 were eligible for inclusion. Of these, 76 (68%) were male and 54 (49%) had ATIN on biopsy. During a median follow-up of 2.3 years, 34 (31%) reached the primary outcome. On univariable Cox regression analysis, ATIN was associated with a five-fold increase in the primary outcome [hazard ratio (HR) (95% confidence interval) 4.9 (95% confidence interval (CI) 2.1–11.3)]. On multivariable analysis, mesangial hypercellularity, tubular atrophy and interstitial fibrosis and ATIN independently associated with renal outcome (P = 0.02 for ATIN). Inter-observer reproducibility revealed fair agreement in the diagnosis of ATIN (κ=0.43, P = 0.05).

Conclusions

Within our centre, ATIN was significantly associated with renal outcome in patients with IgAN, independently of established histological features and baseline clinical characteristics.

Clinical significance of mesangial IgM deposition in patients with IgA nephropathy

BACKGROUND

Glomerular immunoglobulin G deposition in patients with immunoglobulin A nephropathy (IgAN) has been shown to be associated with adverse renal outcomes. Clinical significance of mesangial immunoglobulin M (IgM) deposition in these patients remains to be proven.

METHODS

One hundred patients who had a diagnosis of IgAN between 2001 and 2017 were enrolled. Patients were divided into two groups based on mesangial IgM deposition status. Groups were compared for demographic, clinical, and pathologic variables at baseline and in follow-up. Cox regression analysis was performed to evaluate the effect of mesangial IgM positivity on renal survival.

RESULTS

IgM-positive group included 51% of participants. Baseline demographic and clinical parameters were not significantly different between groups. Mesangial IgM deposition was significantly associated with a higher segmental sclerosis score (p = 0.008). At last visit, median serum creatinine was higher (p = 0.021) and eGFR was lower (p = 0.006) in IgM-positive group. Nineteen (19%) of all patients reached the combined primary outcome which includes doubling in serum creatinine or evolution to ESRD. Cumulative renal survival was lower (p = 0.001) and resistant disease was more frequent in IgM-positive group (p = 0.026). Renal survival at 15 years was 94.2% and 59.7% in IgM-negative and IgM-positive groups, respectively (p = 0.006). Time-averaged proteinuria (HR 2.9; 95% CI 1.9-4.5; p < 0.001) and mesangial IgM deposition (HR, 13.2; 95% CI 1.9-93.1; p = 0.01) were found to be independent predictors of unfavorable renal outcomes.

CONCLUSIONS

In conclusion, we demonstrated that mesangial IgM deposition independently associated with worse renal outcomes in patients with IgA nephropathy.

A comparison of the effectiveness of cyclophosphamide, leflunomide, corticosteroids, or conservative management alone in patients with IgA nephropathy: a retrospective observational study

To compare the long-term efficacy of corticosteroids (P) alone or in combination with cyclophosphamide (CTX), leflunomide (LEF), or Angiotensin-convertase inhibitors or angiotensin II receptor blockers (ACEI/ARB) in treatment for IgA nephropathy (IgAN), 311 patients with IgAN were identified. Therapeutic effectiveness (including progression, partial remission, complete remission) and combined renal endpoint (defined as 30% reduction in eGFR or ESRD) were compared based on different therapies. After immunosuppressive and ACEI/ARB treatment, the levels of eGFR, proteinuria and albumin were significantly improved at the last follow-up, the extent of improvement of eGFR, proteinuria, and albumin was more notable in P + CTX group and P + LEF group. 41%, 52.2%, 55.3% and 55.2% in P + CTX, P + LEF, P and ACEI/ARB group achieved complete remission, respectively. Multivariate regression analysis indicated that only proteinuria (Relative risk (RR) 0.82(0.72-0.94), P = 0.004) and tubular atrophy/interstitial fibrosis (RR 0.26(0.13-0.57), P = 0.001) were predictors for complete remission. The optimal cutoffs of eGFR was 47.085 ml/min/1.73 m2 predicting renal function recovery in P + CTX therapy. In conclusion, tubular atrophy/interstitial fibrosis and massive proteinuria were poor predictors for complete remission in IgAN, it appears as though patients may have benefited from immunosuppressive treatment but that comparison to a well-matched contemporary control group or, ideally, a randomized controlled clinical trial, would be required to show this.

U6 can be used as a housekeeping gene for urinary sediment miRNA studies of IgA nephropathy

Recent studies have indicated that urinary sediment miRNAs not only are able to serve as non-invasive diagnostic biomarkers for IgA nephropathy (IgAN) but may also be closely related to several clinical and pathological indicators. However, the lack of a suitable internal reference miRNA has hampered research into urinary sediment miRNAs. To date, U6 has been used as a reference gene in urinary sediment miRNA studies mostly based on the results from studies using tissue samples and cell lines. In a total of 330 IgAN patients, 164 disease control patients and 130 normal control patients, there was no significant difference in U6 levels. We also compared the U6 levels in different types of primary glomerular disease groups (IgA nephropathy, membranous nephropathy, minimal change nephrosis and focal segmental glomerular sclerosis). The results confirmed that there was no significant difference in the expression of U6 in different primary glomerular disease groups. Moreover, treatment had no significant effect on the expression levels of U6 in IgA nephropathy. Therefore, U6 is an excellent housekeeping gene for urinary sediment miRNA studies of IgA nephropathy.

Atypical Presentation of IgA Nephropathy Mimicking Acute Pyelonephritis

Background

IgA glomerulonephritis may present with hematuria, flank pain, and fever. This clinical presentation may be easily confused with acute pyelonephritis.

Case Report

We present the case of a 25-year-old female with a typical clinical presentation for acute pyelonephritis (high fever, left flank pain, left costovertebral angle tenderness, hematuria, elevated inflammatory markers, and a hypoenhancing region in the left kidney on contrast-enhanced computed tomography). However, urine and blood cultures were both negative, the serum creatinine was elevated, and the urinalysis revealed significant proteinuria and dysmorphic red blood cells. A kidney biopsy confirmed a diagnosis of IgA nephropathy. She was treated with a combination of lisinopril and methylprednisolone, with good response.

Conclusion

Gross hematuria, especially in the absence of pyuria or bacteriuria, should raise the suspicion for underlying IgA nephropathy, even if the rest of the clinical presentation is typical for a urinary tract infection. The presence of significant proteinuria, red blood cell casts, and dysmorphic red blood cells are useful clues suggesting glomerular disease.

IgA nephropathy in African Americans: uncommon but possible

Though IgA nephropathy is relatively uncommon in African Americans, our case serves as a reminder that it needs to be considered in the differentials when these patients present with proliferative glomerulonephritis.

Biomarkers for IgA nephropathy on the basis of multi-hit pathogenesis

IgA nephropathy (IgAN) is the most prevalent glomerular disease worldwide and is associated with a poor prognosis. Development of curative treatment strategies and approaches for early diagnosis is necessary. Renal biopsy is the gold standard for the diagnosis and assessment of disease activity. However, reliable biomarkers are needed for the noninvasive diagnosis of this disease and to more fully delineate the risk of progression. With regard to the pathogenesis of IgAN, the multi-hit hypothesis, including production of galactose-deficient IgA1 (Gd-IgA1; Hit 1), IgG or IgA autoantibodies that recognize Gd-IgA1 (Hit 2), and their subsequent immune complexes formation (Hit 3) and glomerular deposition (Hit 4), has been widely supported by many studies. Although the prognostic values of several biomarkers have been discussed, we recently developed a highly sensitive and specific diagnostic method by measuring serum levels of Gd-IgA1 and Gd-IgA1-containing immune complexes. In addition, urinary Gd-IgA1 may represent a disease-specific biomarker for IgAN. We also confirmed that there is a significant correlation between serum levels of these effector molecules and disease activity, suggesting that each can be considered a practical surrogate marker of therapeutic response. Thus, these disease-oriented specific serum and urine biomarkers may be useful for screening of potential IgAN with isolated hematuria, earlier diagnosis, disease activity, and eventually, response to treatment. In this review, we discuss these concepts, with a focus on potential clinical applications of these biomarkers.

Association of TNFSF13 polymorphisms with IgA nephropathy in a Chinese Han population

BACKGROUND

Our previous genome-wide association study of IgA nephropathy (IgAN) in a Chinese Han population suggested that the TNFSF13 gene may be a novel susceptibility gene for IgAN. In the present study, we aimed to further evaluate the associations of single-nucleotide polymorphisms (SNPs) and expression level of the TNFSF13 gene with the risk and clinical parameters of IgAN.

METHODS

Six candidate SNPs were selected for genotyping by Sequenom MassARRAY iPLEX in 1000 IgAN cases and 1000 controls. Unconditional logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) with adjustment for age and sex. Serum APRIL (encoded by the TNFSF13 gene) level was detected by an enzyme-linked immunosorbent assay.

RESULTS

We found that rs3803800 was significantly associated with the susceptibility of IgAN after Bonferroni correction [p_additive  = 0.0009, OR (95% CI) = 1.25 (1.09-1.42); p_recessive  = 0.0006, OR (95% CI) = 1.54 (1.20-1.96)]; however, the association remained only in women after further sex-stratified analysis. Genotype-phenotype correlation analysis showed significant associations of rs3803800 with severe clinicopathological manifestations in IgAN patients after adjusting for age and sex, as well as the other two SNPs (rs4246413 and rs4968210) that were also associated with specific clinical phenotypes. Compared with healthy controls, serum APRIL levels were significantly higher in IgAN patients (p = 0.0001) and associated with severity of disease.

CONCLUSIONS

The results of the present study indicate that the genetic variations and gene expression level of TNFSF13 are associated with the susceptibility and severity of IgAN in a Han Chinese population.

Defective activation of the MAPK/ERK pathway, leading to PARP1 and DNMT1 dysregulation, is a common defect in IgA nephropathy and Henoch-Schönlein purpura

Studies on IgA nephropathy (IgAN) have identified, through GWAS, linkage analysis, and pathway scanning, molecular defects in familial and sporadic IgAN patients. In our previous study, we identified a novel variant in the SPRY2 gene that segregates with the disease in one large family. The functional characterization of this variant led us to discover that the MAPK/ERK pathway was defective not only in this family, but also in two sporadic IgAN patients wild type for SPRY2. In the present study, we have deepened the molecular analysis of the MAPK/ERK pathway and extended our evaluation to a larger cohort of sporadic patients and to one additional family. We found that the ERK pathway is defective in IgAN patients and in patients affected by another IgA-mediated disorder, Henoch-Schönlein purpura (HSP). Furthermore, we found that two other proteins, PARP1 and DNMT1, respectively involved in DNA repair and in antibody class switching and methylation maintenance duties, were critically downregulated in IgAN and HSP patients. This study opens up the possibility that defective ERK activation, in some patients, leads to PARP1 and DNMT1 downregulation suggesting that IgAN could be the consequence of a dysregulated epigenetic maintenance leading to the upregulation of several genes. In particular, PARP1 could be used as a potential biomarker for the disease.

Campylobacter rectus in the Oral Cavity Correlates with Proteinuria in Immunoglobulin A Nephropathy Patients

BACKGROUND

Periodontitis-related pathogens, such as Campylobacter or Treponema species, have recently been shown to be associated with immunoglobulin A nephropathy (IgAN). Some strains of Streptococcus mutans, a major pathogen of dental caries, harbour the cnm gene that encodes a collagen-binding protein (Cnm). This has also been demonstrated to be associated with urinary protein levels in IgAN patients.

OBJECTIVES

The purpose of the present study was to analyse the association of IgAN with C. rectus, Treponema denticola and cnm-positive S. mutans in the oral cavity of humans.

METHODS

The presence of C. rectus, T. denticola and cnm-positive S. mutans strains in saliva samples of 117 IgAN patients and 56 healthy controls was evaluated by PCR, and the subjects' clinical parameters were analysed.

RESULTS

C. rectus was significantly more prevalent in the IgAN group than in the control group (p < 0.05). The C. rectus-positive group was significantly associated with proteinuria in the IgAN group (p < 0.05). In addition, the C. rectus-positive and cnm-positive S. mutans group was shown to be more closely associated with urinary protein levels than the other groups (p < 0.0083).

CONCLUSION

Our results suggest that harbouring C. rectus in the oral cavity could be associated with proteinuria in IgAN patients.

Gender-related differences in clinicopathological characteristics and renal outcomes of Chinese patients with IgA nephropathy

Background

The prognostic effect of gender on immunoglobulin A nephropathy (IgAN) is not clear. We explored gender-related differences in clinicopathological features and renal outcomes in IgAN.

Methods

This was a single-centre retrospective study. Patients were divided into two groups according to gender. The clinicopathological features at biopsy and renal outcomes during the follow-up were collected and analysed. Renal outcomes were defined as the doubling of baseline serum creatinine and end-stage renal disease (ESRD) (estimated glomerular filtration rate < 15 mL/min/1.73 m², dialysis, or renal transplantation). The prognostic effects of gender were evaluated by Cox regression models.

Results

A total of 988 eligible IgAN patients were enrolled, and the ratio of males to females was 1:1.4. Compared with female patients, male patients had worse renal function, greater proteinuria, a higher prevalence of hypertension, hypertriglyceridaemia and hyperuricaemia, and more severe segmental sclerosis and tubular atrophy/interstitial fibrosis. However, haematuria occurred more frequently in female patients. During a median follow-up time of 48.6 (34.7, 62.7) months, no differences in renal survival rates were noted between the male and female groups. Multivariable Cox regression analyses revealed that gender was not a significant risk factor for renal outcomes after frequency matching of baseline eGFR and serum uric acid (SUA) levels. In addition, male and female patients shared similar risk factors, including a low eGFR and increased proteinuria and segmental sclerosis. In males, however, an elevated proportion of global glomerulosclerosis was also a poor prognostic factor for renal survival.

Conclusions

Male IgAN patients presented with worse clinicopathologic features than female patients, but no significant differences were observed in long-term renal survival between male and female patients by eGFR- and SUA level-matching.

TREM-1 Contributes to Inflammation in IgA Nephropathy

Background

Circulating IgA1-containing immune complexes (cIgA1) were shown to play important roles in IgA nephropathy (IgAN). They could induce the release of multiple inflammatory factors, including MCP-1 and IL-6, and elevated urinary inflammatory factors were also reported in patients with IgAN, which suggested that inflammation is a major contributor to kidney injury in IgAN. After the previous identification of the upregulated release of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) by mesangial cells under cIgA1 challenge using cytokine array, in the present study, we further explored the role of TREM-1, an amplifier of inflammation, in cIgA1-induced kidney injury.

Methods

In total, 35 patients with IgAN and 17 healthy controls were enrolled. The cIgA1 was isolated from plasma and used to treat cultured mesangial cells. The mRNA expression of TREM-1 as well as levels of sTREM-1, MCP-1, and IL-6 in the mesangial cell supernatant and urine samples were detected.

Results

We found that cIgA1 from patients with IgAN could significantly upregulate the expression of TREM-1 in mesangial cells compared to healthy controls. The levels of ΔsTREM-1 were positively correlated with MCP-1 levels in the mesangial supernatant. Similarly, higher urinary levels of sTREM-1 were also observed in patients with IgAN compared to healthy controls. Moreover, IgAN patients with detectable urinary sTREM-1 presented with severe clinical and pathological manifestations, including higher IgA and lower eGFR levels, compared to patients whose urinary sTREM-1 levels were below the limit of quantification.

Conclusion

Our present study suggested that TREM-1 in cIgA1 induced inflammatory kidney injury in IgAN.

Elevated serum fibrinogen level is an independent risk factor for IgA nephropathy

Background

IgA nephropathy is a primary cause of renal failure, and inflammation and renal fibrosis are the main mechanisms leading to kidney damage. The serum fibrinogen level is closely related to inflammatory states, but its relationship to the prognosis of IgA nephropathy (IgAN) is unclear.

Materials and Methods

1053 patients diagnosed with IgAN after renal biopsy were enrolled from two Nephrology Departments. Demographic and clinical data and histopathological features were collected. The patients were divided into four groups (Q1–Q4) according to the serum fibrinogen levels at the time of renal biopsy, and the relationships of serum fibrinogen levels with other risk factors and the prognosis of IgAN were investigated.

Results

672 patients with proven primary IgAN were included in this study, which included a median follow-up of 36 months. Patients with higher serum fibrinogen levels had elevated serum creatinine levels, 24-hour urinary protein, and blood pressure compared with patients with the lowest levels of serum fibrinogen as well as severe renal damage at the time of renal biopsy. Univariate and multivariate Cox regression analyses confirmed that the serum fibrinogen level at the time of renal biopsy was significantly related to the prognosis of patients with IgAN.

Conclusions

In patients with IgAN, an elevated serum fibrinogen level at the time of renal biopsy is associated with poor renal outcomes, which suggests the need for more aggressive early interventions. Greater benefits of aggressive treatments were observed in patients with higher serum fibrinogen levels.

Comparative proteomic analysis of urine and laser microdissected glomeruli in IgA nephropathy

The purpose of the present study was to identify the differential proteins that synchronously change in urine and glomeruli and could be used to monitor glomerular lesions of IgA nephropathy (IgAN). The proteomes of urine and glomeruli from four IgAN patients who were graded III/IV according to the grading system of Lee et al. were compared to the urine proteomes of four healthy volunteers and the glomeruli proteomes of adjacent normal tissue from four patients with renal tumors, respectively. Western blot, enzyme-linked immunosorbent assay and immunofluorescence assay were applied to verify the results of the proteomic analysis. In the proteomic analysis of urine from IgAN patients and healthy volunteers, 714 proteins were identified, with 246 proteins identified as differential proteins. In the proteomic analysis of glomeruli from renal biopsy tissue of IgAN patients and from adjacent normal tissue of patients with renal tumors, 161 proteins were identified altogether, and 20 proteins of these were recognized as differential proteins. After comparatively analyzing the differential proteins identified in the urine and glomeruli, five synchronously changed differential proteins were found: complement C9, Ig kappa chain C region and three cytoskeleton proteins. In summary, our findings indicate that certain immunological indices in urine appear to be associated with glomerular lesions of IgAN.

Pathogenic role of glycan-specific IgG antibodies in IgA nephropathy

Background

Accumulating evidences proved the important roles of circulating IgA1-containing immune complexes (cIgA1) in IgA nephropathy (IgAN). Galactose-deficient IgA1 (Gd-IgA1) and glycan-specific IgG antibody have been identified as major components in cIgA1. Before, Gd-IgA1 was reported as a vital factor in IgAN, partly via of its pathogenic role to induce mesangial cells activation. However, we still lack direct evidences to clarify the biological effect of glycan-specific IgG antibody in IgAN.

Methods

In the present study, we enrolled 35 IgAN patients and 17 age- and sex-matched healthy controls. Using uniform aberrant glycosylated IgA1 molecules, and IgG from different individuals, we in vitro prepared IgG-ddIgA1 complexes, and compared the biological differences among these immune complexes regarding their proliferative and inflammatory effects on mesangial cells.

Results

IgG-ddIgA1 complexes from both patients with IgA nephropathy (IgAN-IgG-dd-IgA1) and healthy controls (HC-IgG-dd-IgA1) could induce the proliferation of mesangial cells and up-regulate expression of MCP-1, IL-6 and CXCL1. The levels of mesangial cells proliferation induced by IgAN-IgG-dd-IgA1 were significantly higher than those induced by HC-IgG-dd-IgA1 (1.10 ± 0.05 vs. 1.03 ± 0.03; p < 0.001). However, the levels of secreted MCP-1, IL-6 and CXCL1 from mesangial cells challenged by IgAN-IgG-dd-IgA1 and HC-IgG-dd-IgA1 were comparable.

Conclusions

We found that glycan-specific IgG antibodies derived from patients with IgAN had the biological effect to induce mesangial cells proliferation. Moreover, in the present study we also established a method for in vitro preparation of pathogenic IgG-ddIgA1 complexes, which could be applied in future studies exploring IgAN pathogenesis.