IgA nephropathy

Mortality of IgA nephropathy patients: a single center experience over 30 years

Research on the prognosis of IgA nephropathy (IgAN) has focused on renal survival, with little information being available on patient survival. Hence, this investigation aimed to explore long-term patient outcome in IgAN patients. Clinical and pathological characteristics at the time of renal biopsy were reviewed in 1,364 IgAN patients from 1979 to 2008. The outcomes were patient death and end stage renal disease (ESRD) progression. Overall, 71 deaths (5.3%) and 277 cases of ESRD (20.6%) occurred during 13,916 person-years. Ten-, 20-, and 30-year patient survival rates were 96.3%, 91.8%, and 82.7%, respectively. More than 50% patient deaths occurred without ESRD progression. Overall mortality was elevated by 43% from an age/sex-matched general population (GP) (standardized mortality ratio [SMR], 1.43; 95% confidence interval [CI], 1.04–1.92). Men had comparable mortality to GP (SMR, 1.22; 95% CI, 0.82–1.75), but, in women, the mortality rate was double (SMR, 2.17; 95% CI, 1.21–3.57). Patients with renal risk factors such as initial renal dysfunction (estimated glomerular filgration rate <60 ml/min per 1.73m²; SMR, 1.70; 95% CI, 1.13–2.46), systolic blood pressure ≥140 mmHg (SMR, 1.88; 95% CI, 1.19–2.82) or proteinuria ≥1 g/day (SMR, 1.66; 95% CI, 1.16–2.29) had an elevated mortality rate. Patients with preserved renal function, normotension, and proteinuria <1 g/day, however, had a similar mortality rate to GP. When risk stratification was performed by counting the number of major risk factors present at diagnosis, low-risk IgAN patients had a mortality rate equal to that of GP, whereas high-risk patients had a mortality rate higher than that of GP. This investigation demonstrated that overall mortality in IgAN patients was higher than that of GP. Women and patients with renal risk factors had a higher mortality than that of GP, Therefore, strategies optimized to alleviate major renal risk factors are warranted to reduce patient mortality.

Bilateral scleritis and sclerokeratitis associated with IgA nephropathy

PURPOSE

The purpose of this study is to report a case of bilateral nodular scleritis in a patient with final diagnosis of IgA nephropathy.

METHODS

This is an observational case report.

RESULTS

A male patient, 42 years old, presented with a bilateral nodular scleritis and OD sclerokeratitis. He had a previous history of acute otitis media and developed posterior renal failure and arterial hypertension. Clinical and systemic findings suggest Wegener's granulomatosis. A kidney biopsy was performed, and immunoflourescence findings demonstrated granular deposits of IgA in a mesangial pattern confirming the diagnosis of IgA nephropathy

CONCLUSIONS

IgA nephropathy should be a differential diagnosis in patients with scleritis and nephropathy.

The association of Klotho polymorphism with disease progression and mortality in IgA nephropathy

BACKGROUNDS

IgA nephropathy (IgAN) is the most common primary glomerulonephritis causing end stage renal disease (ESRD), and vasculopathy is known to involve disease progression. Klotho, a gene related to aging, has been reported to play a role in atherosclerosis and endothelial dysfunction. We investigated whether klotho gene polymorphism affect clinical course of IgAN.

METHODS

The data registered for PREMIER study which enrolled the patients with biopsy proven IgAN were analyzed. Two single nucleotide polymorphisms for klotho gene, G395A of promoter region and C1818T of exon 4, were examined, and investigated the association klotho genotypes with the progression of IgAN and patient survival.

RESULTS

Clinical data from 973 patients confirmed about survival were analyzed. The allele frequency was 0.830 and 0.170 for allele G and A, and 0.816 and 0.184 for allele C and T, which were complied with Hardy-Weinberg equilibrium (p=0.996 and 0.531 respectively). Death was observed more frequently in A-allele carriers of G395A polymorphism (0.7 vs. 2.6 %, GG vs. GA+AA, p=0.022). Renal survival in Kaplan-Meier survival curve was also worse in same group (p=0.04).

CONCLUSION

Klotho gene polymorphism was associated with patient survival and disease progression of IgAN.

Pathogenesis of immunoglobulin A nephropathy: recent insight from genetic studies

Recent genome-wide association studies (GWAS) have identified multiple susceptibility loci for immunoglobulin A nephropathy (IgAN), the most common form of glomerulonephritis, implicating independent defects in adaptive immunity (three loci on chromosome 6p21 in the MHC region), innate immunity (8p23 DEFA locus, 17p23 TNFSF13 locus, 22q12 HORMAD2 locus), and the alternative complement pathway (1q32 CFH/CFHR locus). In geospatial analysis of 85 populations, a genetic risk score based on the replicated GWAS loci is highest in Asians, intermediate in Europeans, and lowest in Africans, capturing the known difference in prevalence among world populations. The genetic risk score also uncovered a previously unsuspected increased prevalence of IgAN-attributable kidney failure in Northern Europe. The IgAN risk alleles have opposing effects on many immune-mediated diseases, suggesting that selection has contributed to variation in risk allele frequencies among different populations. Incorporating genetic, immunologic, and biochemical data, we present a multistep pathogenesis model that provides testable hypotheses for dissecting the mechanisms of disease.

The level of galactose-deficient IgA1 in the sera of patients with IgA nephropathy is associated with disease progression

Although high serum levels of galactose-deficient IgA1 (an important biomarker of IgA nephropathy (IgAN)) are found in most patients with IgAN, their relationship to disease severity and progression remains unclear. To help clarify this we prospectively enrolled 275 patients with IgAN and followed them for a median of 47 months (range 12-96 months). Serum galactose-deficient IgA1 was measured at the time of diagnosis using a lectin-based ELISA, and renal survival was modeled using the Cox proportional hazards method. The serum levels of galactose-deficient IgA1 were higher in patients with IgAN compared to those in healthy controls. Importantly, in adjusted analysis, higher levels of galactose-deficient IgA1 were independently associated with a greater risk of deterioration in renal function with a hazard ratio of 1.44 per standard deviation of the natural log-transformed galactose-deficient IgA1 concentration. In reference to the first quartile, the risk of kidney failure increased such that the hazard ratio for the second quartile was 2.47, 3.86 for the third, and 4.76 for the fourth quartile of the galactose-deficient IgA1 concentration. Hence, elevated serum levels of galactose-deficient IgA1 are associated with a poor prognosis in IgAN.

Urinary mannose-binding lectin is a biomarker for predicting the progression of immunoglobulin (Ig)A nephropathy

Complement system activation is associated with immunoglobulin A nephropathy (IgAN) activity and progression. The aim of the present study was to investigate the importance of urinary mannose-binding lectin (MBL), at the time of renal biopsy, for evaluating disease severity and predicting the progression of IgAN. A total of 162 patients with biopsy-proven IgAN were enrolled and 50 healthy individuals were selected as normal controls. Urinary MBL was measured by sandwich enzyme-linked immunosorbent assay (ELISA) and normalized for urinary creatinine concentration. Urinary MBL was significantly higher in IgAN patients than that in normal controls, and elevated as histopathological phenotypes upgraded. Urinary MBL was correlated significantly with the well-known clinical predictors for the prognosis of IgAN; that is, renal function (represented by serum creatinine and estimated glomerular filtration rate), proteinuria and arterial hypertension. Urinary MBL was demonstrated to be correlated with the histopathological parameters which have independent value in predicting renal outcome of IgAN according to the Oxford classification; that is, mesangial hypercellularity, segmental glomerulosclerosis, endocapillary hypercellularity and tubular atrophy/interstitial fibrosis. More importantly, non-remission patients at the end of follow-up had significantly higher levels of urinary MBL compared with patients in remission. In conclusion, urinary MBL can be a reliable non-invasive biomarker for evaluating disease severity and predicting the prognosis of IgAN. This is the first report on this issue. However, our conclusions should be verified further in large-scale studies with long-term follow-up.

Comparison of effective impact among tonsillectomy alone, tonsillectomy combined with oral steroid and with steroid pulse therapy on long-term outcome of immunoglobulin A nephropathy

Background

To clarify the therapeutic impact of tonsillectomy and combined therapies of tonsillectomy plus steroid on the long-term prognosis of immunoglobulin A nephropathy (IgAN).

Methods

A retrospective study was conducted on 208 patients with IgAN between 1986 and 2009. According to the strategies for treatments, patients were divided into four groups: tonsillectomy and steroid pulse (TSP, n = 47), tonsillectomy and oral steroid (TOS, n = 33), tonsillectomy alone (T, n = 56), and N group (no particular therapy, n = 72). Multivariate analysis based on the Cox’s regression model was used to assess the relative risk of reaching the outcome of doubling creatinine based on the influence of baseline prognostic factors.

Results

The mean observation periods were 53.8 months in the TSP group, 122.0 months in the TOS group, 102.9 months in the T group, and 84.6 months in the N group. During an observation period, serum creatinine levels doubled as follows: one in the TSP group (2.1 %), two in the TOS group (6.1 %), five in the T group (8.9 %), histological severity, and 22 in the N group (30.6 %). The Cox’s regression proportional hazard model showed that gender, age, histological activity, dialysis induction risk and therapy were associated with doubling creatinine levels. Hazard ratios (95 % CI) and (P value) in T, TOS, and TSP groups versus N were 0.314 (0.11–0.93, P = 0.037), 0.213 (0.04–1.10, P = 0.065), and 0.032 (0.00–0.28, P = 0.002), respectively.

Conclusion

A combination therapy of tonsillectomy and steroid pulse had the most significant therapeutic impact compared to other therapies.

Clinical significance of IgG deposition in the glomerular mesangial area in patients with IgA nephropathy

Background

Immunoglobulin (Ig) A nephropathy (IgAN) is characterized by mesangial deposits of IgA1 and C3, often with co-deposits of IgG. We attempted to clarify the clinical significance of mesangial IgG deposition in patients with IgAN.

Methods

We retrospectively reviewed 57 patients who were diagnosed with IgAN on the basis of pathological examination of renal biopsy specimens obtained between October 2006 and December 2010. Subjects were divided into two groups: IgA+IgG deposition (IgA-IgG) group (n = 29) and IgA deposition alone (IgA) group (n = 28). The study outcome was complete remission (CR), defined as negative proteinuria by dipstick urinalysis and urinary erythrocytes of less than 1–4/high-power field.

Results

Proteinuria was greater in the IgA-IgG group than the IgA group (1.1 ± 0.8 vs. 0.7 ± 0.6 g/day, Mann–Whitney U test, P = 0.042). Capillary wall IgA deposits were noted more frequently in the IgA-IgG group than the IgA group (59 vs. 11 %, Fisher’s exact test, P = 0.014). During the median follow-up period of 33.3 months (range 6–55 months) in the 57 patients, we observed CR in 24 cases (42.1 %). After the start of treatment, urinary abnormalities disappeared earlier in the IgA group than in the IgA-IgG group (log rank test, P = 0.012). Cox’s regression model showed that IgG deposition reduced the hazard ratio for CR (hazard ratio 0.35; 95 % confidence interval 0.14–0.82, P = 0.014). Therefore, IgG deposition is a risk factor for persistent urinary abnormalities.

Conclusion

Mesangial IgG deposition is associated with more severe clinical features in patients with IgAN.

Kidneys in chronic liver diseases

Acute kidney injury (AKI), defined as an abrupt increase in the serum creatinine level by at least 0.3 mg/dL, occurs in about 20% of patients hospitalized for decompensating liver cirrhosis. Patients with cirrhosis are susceptible to developing AKI because of the progressive vasodilatory state, reduced effective blood volume and stimulation of vasoconstrictor hormones. The most common causes of AKI in cirrhosis are pre-renal azotemia, hepatorenal syndrome and acute tubular necrosis. Differential diagnosis is based on analysis of circumstances of AKI development, natriuresis, urine osmolality, response to withdrawal of diuretics and volume repletion, and rarely on renal biopsy. Chronic glomerulonephritis and obstructive uropathy are rare causes of azotemia in cirrhotic patients. AKI is one of the last events in the natural history of chronic liver disease, therefore, such patients should have an expedited referral for liver transplantation. Hepatorenal syndrome (HRS) is initiated by progressive portal hypertension, and may be prematurely triggered by bacterial infections, nonbacterial systemic inflammatory reactions, excessive diuresis, gastrointestinal hemorrhage, diarrhea or nephrotoxic agents. Each type of renal disease has a specific treatment approach ranging from repletion of the vascular system to renal replacement therapy. The treatment of choice in type 1 hepatorenal syndrome is a combination of vasoconstrictor with albumin infusion, which is effective in about 50% of patients. The second-line treatment of HRS involves a transjugular intrahepatic portosystemic shunt, renal vasoprotection or systems of artificial liver support.

Predicting progression of IgA nephropathy: new clinical progression risk score

IgA nephropathy (IgAN) is a common cause of end-stage renal disease (ESRD) in Asia. In this study, based on a large cohort of Chinese patients with IgAN, we aim to identify independent predictive factors associated with disease progression to ESRD. We collected retrospective clinical data and renal outcomes on 619 biopsy-diagnosed IgAN patients with a mean follow-up time of 41.3 months. In total, 67 individuals reached the study endpoint defined by occurrence of ESRD necessitating renal replacement therapy. In the fully adjusted Cox proportional hazards model, there were four baseline variables with a significant independent effect on the risk of ESRD. These included: eGFR [HR = 0.96(0.95-0.97)], serum albumin [HR = 0.47(0.32-0.68)], hemoglobin [HR = 0.79(0.72-0.88)], and SBP [HR = 1.02(1.00-1.03)]. Based on these observations, we developed a 4-variable equation of a clinical risk score for disease progression. Our risk score explained nearly 22% of the total variance in the primary outcome. Survival ROC curves revealed that the risk score provided improved prediction of ESRD at 24th, 60th and 120th month of follow-up compared to the three previously proposed risk scores. In summary, our data indicate that IgAN patients with higher systolic blood pressure, lower eGFR, hemoglobin, and albumin levels at baseline are at a greatest risk of progression to ESRD. The new progression risk score calculated based on these four baseline variables offers a simple clinical tool for risk stratification.

Unexpected Death from Hemorrhagic Pericarditis Complicating IgA Nephropathy

IgA nephropathy is the most common cause of glomerulonephritis in the developed world; however, it is usually an indolent or slowly progressive disease presenting initially as self-limited hematuria, typically following a viral or bacterial infection. We report a case of previously undiagnosed IgA nephropathy manifesting with end stage renal disease, fibrinous pericarditis, and hemorrhagic pericardial effusion in a 26-year-old white male. Clinical manifestations of IgA nephropathy, the presumed pathogenesis, and complications are reviewed. This case highlights the importance of interdisciplinary collaborations with other specialized pathology services—in this case renal pathology, including direct immunofluorescence and electron microscopy—that may not be routinely available or used in forensic pathology practices. In this instance, such collaboration provided the etiologically specific diagnosis for an unusual presentation of a common disease.

Complete remission within 2 years predicts a good prognosis after methylprednisolone pulse therapy in patients with IgA nephropathy

BACKGROUND

Pozzi et al. reported the effectiveness of steroid pulse therapy (Pozzi's regimen) in IgA nephropathy (IgAN). The present study was performed to clarify the predictive factors for IgAN patients treated with Pozzi's regimen.

METHODS

One hundred nine IgAN patients treated by Pozzi's regimen were observed for up to 112.6 (median 39.7) months, and remission of proteinuria (PR) and disappearance of urinary abnormalities [complete remission (CR)] after Pozzi's regimen were analyzed. Predictive factors for the glomerular filtration rate (GFR) slopes for up to 5 years were analyzed among 81 patients who were observed for at least 2 years. The outcome of a 50 % increase in sCr was compared between the CR and non-CR groups within 2 years.

RESULTS

Cumulative PR and CR rates increased rapidly until 2 years (54.5 and 46.8 % at 2 years), and then slowly but steadily up to 6 years (72.8 and 66.4 % at 6 years). Baseline characteristics of the CR and non-CR groups within 2 years were similar except for proteinuria. GFR slope was steeper in the non-CR group than in the CR group (-2.44 ± 5.12 vs. -0.32 ± 3.34 ml/min/1.73 m(2)/year). On multivariate analysis, sex and CR within 2 years were associated with GFR slope. Kaplan-Meier analysis demonstrated a better survival rate in CR group patients without a 50 % increase in sCr (p = 0.024).

CONCLUSIONS

Among IgAN patients treated with Pozzi's regimen, CR within 2 years predicts a good prognosis.

Urinary protein markers predict the severity of renal histological lesions in children with mesangial proliferative glomerulonephritis

BACKGROUND

Several renal histopathological features, including mesangial hypercellularity, glomerulosclerosis, tubular atrophy and interstitial fibrosis, are considered to be independent predictors of end-stage renal failure in patients with glomerular diseases. Mesangial proliferative glomerulonephritis (MesPGN) is characterized by proliferations of mesangial cells with increase in mesangial matrix and/or deposits in mesangial region. The purpose of this study is to determine the association between urinary protein markers measured at the same time as renal biopsy and the severity of renal histological lesions in children with MesPGN, and to evaluate whether these markers could serve as predictors of severe renal histological lesions in this population.

METHODS

Ninety-eight children with MesPGN (40 with IgA nephropathy, 37 with IgM nephropathy, and 21 with MesPGN without IgA/IgM deposition) were enrolled. Urinary level of IgG, albumin, transferrin, α1-microglobulin, β2-microglobulin and N-acetyl-β-glucosaminidase from a morning sample before biopsy was measured.The scores of mesangial hypercellularity, glomerulosclerosis, and tubule-interstitial damage were used to semi-quantitatively evaluate renal histological lesions.

RESULTS

The urine proteins, as independent factors associated with severe mesangial cellularity (> 5 mesangial cells/ mesangial area) were transferrin, albumin, α1-microglobulin, IgG and 24-hour total protein, with severe glomerulosclerosis (≥ 10 % glomeruli showing segmental adhesions or sclerosis) were transferrin and 24-hour total protein, and with severe tubule-interstitial damage (focal or diffuse tubular and interstitial lesions) were transferrin and N-acetyl-β-glucosaminidase. Urinary transferrin achieved the area under-the-receiver-operating-characteristic curve (AUC) of 0.86 and 0.82, respectively, for predicting severe mesangial cellularity and glomerulosclerosis. Urinary N-acetyl-β-glucosaminidase achieved the highest AUC of 0.82 for predicting severe tubule-interstitial damage. The combination of urinary protein markers, however, did not improve the predictability for renal histological lesions.

CONCLUSIONS

Urinary protein markers are useful to predict the severity of renal histological lesions in children with MesPGN, which suggests that urinary proteins might be useful to predict the development and progression of renal histological lesions, and assist in evaluating the outcome and prognosis in children with MesPGN as non-invasive and easily repeatable indicators on the follow-up examination.

Immunotherapy in renal diseases

Immunotherapy has been used for the treatment of renal diseases for a long time, and there has been significant progress in such treatment. This review focuses on the use of immunotherapy for the treatment of glomerular diseases. The use of immunosuppression in the treatment of minimal change disease, membranous nephropathy, primary focal segmental glomerulosclerosis, lupus nephritis, immunoglobulin-A nephropathy, antineutrophil cytoplasmic antibody-associated disease, and anti-glomerular basement membrane disease is discussed.

Validity of the Oxford classification of IgA nephropathy in children

BACKGROUND

In 2009, the Oxford classification of IgA nephropathy was published. However, its validity has not been fully examined in children. This study aimed to assess this system in an independent large-scale cohort of children.

METHODS

We analyzed 161 consecutive children with newly diagnosed IgA nephropathy from 1977 to 1989 retrospectively. We examined the ability of each variable in the Oxford classification as a predictor of renal outcome defined as ≥ stage III chronic kidney disease (CKD) (estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2)) using Cox regression analysis.

RESULTS

The mean mesangial score, and ratios of segmental glomerulosclerosis, endocapillary hypercellularity, tubular atrophy, and crescents were 0.49, 0.8%, 13.1%, 3.3%, and 9.2% respectively. Seven cases reached ≥ stage III CKD. In univariate analyses, mesangial hypercellularity score, endocapillary hypercellularity, tubular atrophy, and crescents were significant predictors of renal outcome. In a multivariate analysis, only mesangial hypercellularity score, tubular atrophy, and crescents were significant though, depending on models. Segmental glomerulosclerosis was not a significant predictor of renal outcome. Although the significance of crescents was not addressed in the Oxford classification, crescents were important predictors of outcome.

CONCLUSIONS

The Oxford classification appears to be valid for predicting renal outcome in children.

Corticosteroid therapy in IgA nephropathy

The benefits and risks of steroids for the treatment of IgA nephropathy remain uncertain. We systematically searched MEDLINE, EMBASE, and the Cochrane Library for randomized, controlled trials of corticosteroid therapy for IgA nephropathy published between 1966 and March 2011. We identified nine relevant trials that included 536 patients who had urinary protein excretion >1 g/d and normal renal function. Forty-six (8.6%) of these patients developed a kidney failure event, defined as doubling of the serum creatinine/halving of the GFR or ESRD. Overall, steroid therapy was associated with a lower risk for kidney failure (relative risk, 0.32 [95% confidence interval [CI], 0.15-0.67]; P=0.002) and a reduction in proteinuria (weighted mean difference, -0.46 g/d [95% CI, -0.63 to -0.29 g/d]), with no evidence of heterogeneity in these outcomes. Subgroup analysis suggested that the dose modifies the effect of steroids for renal protection (P for heterogeneity=0.030): Relatively high-dose and short-term therapy (prednisone >30 mg/d or high-dose pulse intravenous methylprednisolone with duration ≤1 year) produced significant renal protection, whereas low-dose, long-term steroid use did not. Steroid therapy was associated with a 55% higher risk for adverse events. The quality of included studies was low, however, limiting the generalizability of the results. In conclusion, steroids appear to provide renal protection in patients with IgA nephropathy but increase the risk for adverse events. Reliably defining the efficacy and safety of steroids in IgA nephropathy requires a high-quality trial with a large sample size.

The intrinsic prostaglandin E2-EP4 system of the renal tubular epithelium limits the development of tubulointerstitial fibrosis in mice

Inflammatory responses in the kidney lead to tubulointerstitial fibrosis, a common feature of chronic kidney diseases. Here we examined the role of prostaglandin E(2) (PGE(2)) in the development of tubulointerstitial fibrosis. In the kidneys of wild-type mice, unilateral ureteral obstruction leads to progressive tubulointerstitial fibrosis with macrophage infiltration and myofibroblast proliferation. This was accompanied by an upregulation of COX-2 and PGE(2) receptor subtype EP(4) mRNAs. In the kidneys of EP(4) gene knockout mice, however, obstruction-induced histological alterations were significantly augmented. In contrast, an EP(4)-specific agonist significantly attenuated these alterations in the kidneys of wild-type mice. The mRNAs for macrophage chemokines and profibrotic growth factors were upregulated in the kidneys of wild-type mice after ureteral obstruction. This was significantly augmented in the kidneys of EP(4)-knockout mice and suppressed by the EP(4) agonist but only in the kidneys of wild-type mice. Notably, COX-2 and MCP-1 proteins, as well as EP(4) mRNA, were localized in renal tubular epithelial cells after ureteral obstruction. In cultured renal fibroblasts, another EP(4)-specific agonist significantly inhibited PDGF-induced proliferation and profibrotic connective tissue growth factor production. Hence, an endogenous PGE(2)-EP(4) system in the tubular epithelium limits the development of tubulointerstitial fibrosis by suppressing inflammatory responses.

Risk stratification of patients with IgA nephropathy

In this review, we summarize recent advances in the risk stratification of patients with immunoglobulin A (IgA) nephropathy. Several clinical variables have consistent and independent associations with worse kidney prognosis, including blood pressure, proteinuria, and baseline kidney function. Although one-time cross-sectional assessments of blood pressure and proteinuria are important, a more thorough understanding of risk can be achieved when these variables are considered over a follow-up period. IgA nephropathy is unique compared with other glomerular diseases in that a much lower threshold of proteinuria (protein excretion, 1 g/d) is associated with glomerular filtration rate (GFR) loss. Controlling proteinuria and blood pressure over time is important to reduce the risk of future loss of kidney function. The recently described Oxford classification has helped standardize the pathologic characterization of IgA nephropathy using a scoring system that is readily reproducible and associated with increased risk of GFR loss independent of clinical variables. We suggest an approach to risk stratification in IgA nephropathy when considering potential treatment with immunosuppression. Despite our current understanding of risk stratification in IgA nephropathy, the ability to accurately predict individual patient-level risk currently is limited, and further research into additional biomarkers or risk prediction tools is needed to improve the care of patients with IgA nephropathy.

Pathological scenario with the mannose-binding lectin in patients with IgA nephropathy

A deeper understanding of the mechanism of complement activation may help to elucidate the pathogenesis of IgA nephropathy (IgAN). Traditionally, the activation of an alternative pathway (AP) has been recognized as an enhancer mechanism of glomerular damage. This paper documents contemporary information concerning the possible pathological mechanisms of the lectin pathway (LP) in the circulation and in the glomerulus. The circulating initiator of LP activation is not fully understood. However, ligands for mannose-binding lectin (MBL) which are among the starter molecules of the LP are aberrant glycosylated molecules-containing immune complex. Recent reports have focused on N-glycans on secretory IgA as a candidate ligand. Mesangial deposits of MBL are seen in 25% of patients with IgAN. Mesangial deposits of MBL and C4 and/or C4 breakdown products are implicated as markers for disease progression of IgAN. On the other hand, patients with MBL deficiency tend to show better clinical presentation and lower levels of urinary protein and serum creatinine than MBL-sufficient patients. It is now recognized that involvement of AP and LP constitutes an additional mechanism for explaining the progression of IgAN.

Immunoglobulin A nephropathy associated with Plasmodium falciparum malaria

Glomerulonephritis occurs as a rare form of renal manifestation in Plasmodium falciparum malaria. Herein, we report a case of falciparum malaria-associated IgA nephropathy for the first time. A 49-yr old male who had been to East Africa was diagnosed with Plasmodium falciparum malaria. Microhematuria and proteinuria along with acute kidney injury developed during the course of the disease. Kidney biopsy showed mesangial proliferation and IgA deposits with tubulointerstitial inflammation. Laboratory tests after recovery from malaria showed disappearance of urinary abnormalities and normalization of kidney function. Our findings suggest that malaria infection might be associated with IgA nephropathy.

Transglutaminase is essential for IgA nephropathy development acting through IgA receptors

Transglutaminase 2 is required for the development of IgA nephropathy.

IgA nephropathy (IgAN) is a common cause of renal failure worldwide. Treatment is limited because of a complex pathogenesis, including unknown factors favoring IgA1 deposition in the glomerular mesangium. IgA receptor abnormalities are implicated, including circulating IgA–soluble CD89 (sCD89) complexes and overexpression of the mesangial IgA1 receptor, TfR1 (transferrin receptor 1). Herein, we show that although mice expressing both human IgA1 and CD89 displayed circulating and mesangial deposits of IgA1–sCD89 complexes resulting in kidney inflammation, hematuria, and proteinuria, mice expressing IgA1 only displayed endocapillary IgA1 deposition but neither mesangial injury nor kidney dysfunction. sCD89 injection into IgA1-expressing mouse recipients induced mesangial IgA1 deposits. sCD89 was also detected in patient and mouse mesangium. IgA1 deposition involved a direct binding of sCD89 to mesangial TfR1 resulting in TfR1 up-regulation. sCD89–TfR1 interaction induced mesangial surface expression of TGase2 (transglutaminase 2), which in turn up-regulated TfR1 expression. In the absence of TGase2, IgA1–sCD89 deposits were dramatically impaired. These data reveal a cooperation between IgA1, sCD89, TfR1, and TGase2 on mesangial cells needed for disease development. They demonstrate that TGase2 is responsible for a pathogenic amplification loop facilitating IgA1–sCD89 deposition and mesangial cell activation, thus identifying TGase2 as a target for therapeutic intervention in this disease.

Imbalance of regulatory T cells to Th17 cells in IgA nephropathy

BACKGROUND

Dysregulation of CD4 (+) T cell subsets participates in the pathogenesis of IgA nephropathy (IgAN). FoxP3 (+) regulatory T cells (Treg) and Th17 cells are two novel subsets of CD4 (+) T cells. This study aims to investigate Treg/Th17 balance in IgAN patients.

METHODS

Peripheral frequencies of Th17 and Treg functional subsets - CD45RA (+) FoxP3(low) resting Treg (rTreg) and CD45RA(-)FoxP3(high) activated Treg (aTreg) were assessed in 63 adult IgAN patients. Expression of transcription factors (FoxP3 and RORγt) and related cytokines of Treg and Th17 were analysed. Renal expression of FoxP3 and IL-17A were detected by immunohistochemistry.

RESULTS

Compared with normal controls, IgAN patients had decreased frequency of CD45RA(-)FoxP3(high) aTreg subset (p < 0.05), increased frequency of Th17 (p < 0.05) and decreased ratio of Treg/Th17 (p < 0.05). Frequency of aTreg subset correlated with SBP(r = - 0.57, p < 0.05), DBP (r = - 0.50, p < 0.05), eGFR (r = 0.68, p < 0.05) and 24 h proteinuria (r = - 0.58, p < 0.05). RORγtmRNA/FoxP3mRNA ratio increased in IgAN (p < 0.05). Serum IL-17A, IL-21, IL-23, IL-1β and IL-6 elevated while IL-10 decreased in IgAN (p < 0.05), and serum IL-17A correlated with 24 h proteinuria (r = 0.35, p < 0.05). Serum TGF-β1 wasn't different between the two groups. Renal interstitial infiltration of FoxP3 (+) mononuclear cells were observed in IgAN patients, particularly prominent in those with > 25% tubular atrophy/interstitial fibrosis. Tubular IL-17A expression was found in 34 out of 63 IgAN patients. Compared with 29 patients without IL-17A expression, these patients had lower renal function, greater proteinuria, and more severe tubulointerstitial damage.

CONCLUSIONS

Imbalance of Treg/Th17 found in IgAN may play a role in disease pathogenesis and progression.

Clinical features and outcomes of IgA nephropathy with nephrotic syndrome

BACKGROUND AND OBJECTIVES

Nephrotic syndrome (NS) is a rare manifestation of IgA nephropathy (IgAN). Clinical characteristics and long-term outcomes of this condition have not yet been explored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A multicenter observational study was conducted between January 2000 and September 2010 in 1076 patients with biopsy-proven IgAN from four medical centers in Korea. The primary outcome was a doubling of the baseline serum creatinine concentration.

RESULTS

Of the 1076 patients, 100 (10.2%) presented with NS; complete remission (CR), partial remission (PR), and no response (NR) occurred in 48 (48%), 32 (32%), and 20 (20%) patients, respectively. During the median follow-up of 45.2 months, 24 patients (24%) in the NS group reached the primary endpoint compared with 63 (7.1%) in the non-NS group (P<0.001). The risk of reaching the primary endpoint was significantly higher in the PR (P=0.04) and NR groups (P<0.001) than in the CR group. Among patients with NS, 24 (24%) underwent spontaneous remission (SR). SR occurred more frequently in female patients and in patients with serum creatinine levels ≤1.2 mg/dl and a >50% decrease in proteinuria within 3 months after NS onset. None of the patients with SR reached the primary endpoint and they had fewer relapses during follow-up.

CONCLUSIONS

This study demonstrated that the prognosis of NS in IgAN was not favorable unless PR or CR was achieved. In addition, SR was more common than expected, particularly in patients with preserved kidney function and spontaneous decrease in proteinuria shortly after NS onset.

High serum thioredoxin levels are reduced after tonsillectomy in patients with IgA nephropathy

OBJECTIVE

The role of oxidative stress in IgA nephropathy (IgAN), the most common type of primary glomerulonephritis, is unknown. We evaluated the clinical significance of serum levels of oxidative stress markers, thioredoxin (TRX) and manganese superoxide dismutase (MnSOD), in patients with IgAN.

METHODS

Forty-eight patients with histologically confirmed IgAN and 14 healthy subjects were enrolled in this study. Serum samples from 14 IgAN patients were obtained after tonsillectomy, a procedure hypothesized to be an effective treatment for IgAN.

RESULTS

Serum TRX levels were significantly higher in patients with IgAN than in healthy subjects (mean [ng/mL]; 49.5 vs.14.4, p<0.001). Serum TRX levels are positively correlated with blood urea nitrogen, serum uric acid and proteinuria, and negatively with estimated glomerular filtration rate (eGFR). In addition, serum TRX levels gradually increased as the severity of renal histology increased. High levels of serum TRX were significantly decreased after tonsillectomy in patients with IgAN (mean [ng/mL]; 55.5 to 41.1, p=0.02). In contrast, serum MnSOD levels did not differ between IgAN patients and healthy subjects, and these levels did not change after tonsillectomy in IgAN patients.

CONCLUSION

Serum TRX is associated with IgAN, and tonsillectomy may decrease oxidative stress in IgAN patients, leading to clinical improvement.

A genome-wide association study in Han Chinese identifies multiple susceptibility loci for IgA nephropathy

We performed a two-stage genome-wide association study of IgA nephropathy (IgAN) in Han Chinese, with 1,434 affected individuals (cases) and 4,270 controls in the discovery phase and follow-up of the top 61 SNPs in an additional 2,703 cases and 3,464 controls. We identified associations at 17p13 (rs3803800, P = 9.40 × 10(-11), OR = 1.21; rs4227, P = 4.31 × 10(-10), OR = 1.23) and 8p23 (rs2738048, P = 3.18 × 10(-14), OR = 0.79) that implicated the genes encoding tumor necrosis factor (TNFSF13) and α-defensin (DEFA) as susceptibility genes. In addition, we found multiple associations in the major histocompatibility complex (MHC) region (rs660895, P = 4.13 × 10(-20), OR = 1.34; rs1794275, P = 3.43 × 10(-13), OR = 1.30; rs2523946, P = 1.74 × 10(-11), OR = 1.21) and confirmed a previously reported association at 22q12 (rs12537, P = 1.17 × 10(-11), OR = 0.78). We also found that rs660895 was associated with clinical subtypes of IgAN (P = 0.003), proteinuria (P = 0.025) and IgA levels (P = 0.047). Our findings show that IgAN is associated with variants near genes involved in innate immunity and inflammation.

O-glycosylated IgA rheumatoid factor induces IgA deposits and glomerulonephritis

Structural aberrations of O-linked glycans present in the IgA1 hinge region are associated with IgA nephropathy, but their contribution to its pathogenesis remains incompletely understood. In this study, mice implanted with hybridoma secreting 6-19 IgA anti-IgG2a rheumatoid factor, but not 46-42 IgA rheumatoid factor bearing the same IgA allotype, developed mesangial deposits consisting of IgA, IgG2a, and C3. Studies in immunoglobulin- and C3-deficient mice revealed that the development of these glomerular lesions required the formation of IgA-IgG2a immune complexes and subsequent activation of complement. The proportion of polymeric and monomeric forms, the IgG2a-binding affinity, and the serum levels of IgA-IgG2a immune complexes were similar between 6-19 IgA- and 46-42 IgA-injected mice. In contrast, the analysis of oligosaccharide structures revealed highly galactosylated O-linked glycans in the hinge region of 6-19 IgA and poorly O-glycosylated in the hinge region of 46-42 IgA. Furthermore, the structure of N-linked glycans in the CH1 domain was the complex type in 6-19 IgA and the hybrid type in 46-42 IgA. In summary, this study demonstrates the presence of O-linked glycans in the hinge region of mouse IgA and suggests that 6-19 IgA rheumatoid factor-induced GN could serve as an experimental model for IgA nephropathy.

Mechanism of onset and exacerbation of chronic glomerulonephritis and its treatment

Immunoglobulin A nephropathy (IgAN) is one of the most common causes of chronic glomerulonephritis (CGN) in the world. The proliferative and crescentic forms of IgA are found in up to 30% of cases and are associated with nephritic-range proteinuria, accelerated hypertension, and accelerated decline toward end-stage renal disease. On the other hand, Henoch-Schönlein purpura (HSP) is a systemic disorder characterized by leukocytoclastic vasculitis involving the capillaries and the deposition of IgA immune complexes. Renal involvement is the principal cause of morbidity and mortality in children with HSP. Two entity diseases are important as renal diseases in childhood. We herein review the mechanism of the onset and exacerbation of IgAN and HSP nephritis (HSPN) and its treatment. As to the pathogenesis, we found that CB4 provoked exacerbation of renal pathologic findings in hyper IgA mice via endothelial injury, γ-interferon production, and dysfunction of the mesangial pathway and could possibly become one of the factors involved in the mechanism of the onset or evolution of human IgAN. As to the treatment of IgAN and HSPN, we evaluated the efficacy of multidrug combination therapy (prednisolone, warfarin, and dipyridamole, including mizoribine) for diffuse IgAN and the efficacy of methylprednisolone and urokinase pulse therapy plus immunosuppressive drugs for severe HSPN in children. These therapies were effective in ameliorating the proteinuria and histologic severity of patients with IgAN or HSPN. In future, detailed investigations into the pathogenesis of CGN and double-blind randomized control studies on children with IgAN or HSPN will be necessary.

IgA nephropathy in a tertiary care center from south India

IgA nephropathy is being recognized as the commonest glomerular disease worldwide. The prevalence and clinical picture varies from region to region. A retrospective analysis of 400 native renal biopsies performed over a period of 3 years at our center was done to know the prevalence and clinicopathological profile of patients with IgA nephropathy. All the biopsies were processed for both light microscopy and immunofluorescence studies. Patients with predominant IgA deposits were labeled as IgA nephropathy and further classified histopathologically into five subclasses according to the Haas classification. We noted a prevalence of 7.8% (31 cases) of IgA nephropathy. Nephrotic syndrome and chronic renal failure were the most common mode of presentation. Majority of cases fell into subclass III (focal segmental glomerular sclerosis) with 35.5% followed by subclasses IV (diffuse proliferative glomerular sclerosis) and V (global sclerosis) with 25.8% and 22.6% prevalence, respectively. As about 50% cases presented with varying degree of renal insufficiency, many ending with ESRD, IgA nephropathy can be considered as a serious problem in India.

A clinicopathologic study of thrombotic microangiopathy in IgA nephropathy

Thrombotic microangiopathy (TMA) occurs in IgA nephropathy, but its clinical significance is not well described. We retrospectively examined a series of 128 patients diagnosed with IgA nephropathy between 2002 and 2008 who had a mean follow-up of 44±27 months. In our series, 53% presented with lesions of TMA, acute or organized, in arteries and/or arterioles. Among patients with TMA, 4% were normotensive, 25% had controlled hypertension, and 71% had uncontrolled hypertension. Of those with uncontrolled hypertension, 26% had malignant hypertension. Histologically, the group with TMA had a significantly greater percentage of sclerotic glomeruli and worse tubulointerstitial fibrosis than those of the group without TMA. However, a significant minority of patients had near-normal histology, with minimal tubular atrophy (20%) and/or <20% interstitial fibrosis (24%). TMA rarely occurred in the absence of significant proteinuria. During follow-up, a doubling of serum creatinine or ESRD occurred in all patients with laboratory evidence of TMA, in 42% of those with morphologic evidence but no laboratory evidence of TMA, and in 11% of those without TMA. In summary, lesions of TMA are frequent in IgA nephropathy and may occur in normotensive patients with near-normal renal histology. Although the pathophysiologic mechanisms involved remain undetermined, the current study rules out severe hypertension or advanced renal disease as sole causes.

Treatment of IgA nephropathy: an update

OBJECTIVE

To review current literature regarding treatment options for immunoglobulin A nephropathy (IgAN).

DATA SOURCES

A MEDLINE search was performed using the terms IgA nephropathy, Berger's disease, immunoglobulin A nephropathy, angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, fish oil, omega-3 fatty acids, statins, hydroxymethylglutaryl-CoA reductase inhibitors, immunosuppressive therapy, corticosteroids, mycophenolate mofetil, cyclophosphamide, cyclosporine, azathioprine, leflunomide, antiplatelets, anticoagulants, vitamin E, infliximab, calcitriol, and intravenous immunoglobulins. A date limit was not set; however, focus was on publications from 1999 to June 2011 to review recent literature and therapeutic recommendations.

STUDY SELECTION AND DATA EXTRACTION

All articles in English, including studies conducted in humans, meta-analyses, review articles, guidelines, statements, and reference citations, were identified and evaluated.

DATA SYNTHESIS

IgAN is the most common primary glomerulonephritis worldwide, leading to end-stage renal disease in 20-30% of patients. Evidence guiding management of IgAN has been sparse and clinical trials have not conclusively demonstrated effective treatments, largely due to suboptimal methodologies. Treatment strategies have included management of blood pressure and lipids, improvement or stabilization of kidney function, and reduction of proteinuria. This review of IgAN provides an update regarding standard and nonconventional treatment options based on recently published literature.

CONCLUSIONS

Supportive therapies, including angiotensin blockade, should be considered as first-line therapy for patients with urine protein >0.5 g/day and/or blood pressure >140/90 mm Hg. Corticosteroids could be considered as add-on or monotherapy for patients with urine protein >1 g/day with preserved renal function. Conclusive data are lacking for general treatment recommendations for the use of other therapies for IgAN.

Significance of the duration of nephropathy for achieving clinical remission in patients with IgA nephropathy treated by tonsillectomy and steroid pulse therapy

BACKGROUND

Because of the well-established annual urinalysis screening system in Japan, the duration of nephropathy (DN) can be estimated in more than half of all patients with IgA nephropathy (IgAN). Treatment using a combination of tonsillectomy and steroid pulse (TSP) therapy has been reported as an effective method for obtaining clinical remission (CR), defined as negative hematuria and proteinuria, in IgAN patients. The present study aims to identify the correlation between DN and CR rate in IgAN patients treated by TSP therapy.

METHODS

We retrospectively investigated 830 IgAN patients who were followed up for 81.6 months after TSP therapy. DN could be estimated in 495 of the 830 patients.

RESULTS

The CR rate among patients with DN ≤36 months was 87.3% (295/338 patients). The CR rate among patients with DN of 37-84 months was 73.3% (63/86 patients), while that among patients with DN ≥85 months was 42.3% (30/71 patients). The CR rate among the remaining 335 patients in whom DN could not be estimated because of missing annual urinalysis results was 43.6% (146/335 patients). A multivariate Cox regression model using data from the former group of 495 patients showed that DN ≤36 months was a significant predictor of CR (hazard ratio 1.839; 95% confidence interval 1.410-2.398; P < 0.001).

CONCLUSION

Shorter DN is associated with higher likelihood of clinical remission in IgAN patients treated by TSP therapy.

Genetics of kidney failure and the evolving story of APOL1

Chronic kidney disease (CKD) results from a wide array of processes that impair the kidney's ability to perform its major functions. As many as 20 million Americans suffer from CKD and nearly a half million from end-stage renal disease, but there are also examples of centenarians with adequate renal function. Family-based and genome-wide studies suggest that genetic differences substantially influence an individual's lifetime risk for kidney disease. One emerging theme is that evolution of genes related to host defense against pathogens may limit kidney longevity. The identification of these genetic factors will be critical for expanding our understanding of renal development and function as well as for the design of novel therapeutics for kidney disease.

Long-term risk of ESRD in IgAN; validation of Japanese prognostic model in a Norwegian cohort

BACKGROUND

Recently, a Japanese model used to predict 10-year risk of end-stage renal disease (ESRD) in IgA nephropathy (IgAN) patients was published. We tested the applicability of the Japanese model in predicting 10- to 20-year risk of ESRD and all-cause mortality in a cohort of Norwegian IgAN patients.

METHODS

A cohort of IgAN patients (1988-2004) were identified in the Norwegian Kidney Biopsy Registry (NKBR) and ESRD or death during follow-up through 2008 was identified through record linkage with the Norwegian Renal Registry (ESRD) and the Norwegian Population Registry (deaths). Data from the NKBR were used to classify patients into nine different prognostic groups (0-1, 1-5, 5-10, 10-20, 20-30, 30-50, 50-70, 70-90 and >90% risk of ESRD) according to the Japanese prognostic model. The predicted risk was compared to the measured risk of ESRD in the different prognostic groups.

RESULTS

In eight of the nine risk groups, representing 597/633 (94%) of the patients in our cohort, the observed 10-year risk was within or close to the expected 10-year risk of ESRD. ESRD occurring after >10 years of observation was most frequent in the groups with 5-30% expected risk at 10 years of follow-up. A close association between risk of ESRD and risk of death prior to ESRD was observed.

CONCLUSIONS

The Japanese prognostic model is applicable to predict 10-year risk of ESRD in Norwegian IgAN patients. A new finding in the present study is that the model can also be used to predict which patients have the highest risk of developing ESRD after 10-20 years of follow-up as well as all-cause mortality risk.

Behcet's disease and IgA nephropathy

Although Behçet's disease (BD) is a kind of systemic disease, renal involvement is rare, especially IgA nephropathy (IgAN). Renal manifestations in BD range from mild urinary abnormalities to glomerulonephritis with persistent renal failure, which includes minimal change disease, proliferative glomerulonephritis, rapidly crescentic glomerulonephritis, renal amyloidosis and IgA nephropathy. Amyloidosis seems to be the most common type of renal lesion in BD, and several cases of nephrotic syndrome secondary to amyloidosis have been documented. Co-occurrence of BD and IgA nephropathy has only been reported in only few cases. We describe two patients with the rare association of BD and IgAN. We suggested that it is important to periodically perform renal function assessment in patients with BD, through urinalysis and measurement of serum creatinine for detecting any abnormality and providing an early adequate treatment.

A candidate gene approach to genetic contributors to the development of IgA nephropathy

BACKGROUND

Genetic factors contributing to the development of IgA nephropathy remain to be elucidated.

METHODS

The present multicenter cross-sectional case-control study measured genotype frequencies of 65 atherosclerotic disease-related gene polymorphisms in 230 Japanese patients with IgA nephropathy and 262 apparently healthy volunteers with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m(2) and negative or trace proteinuria and hematuria by dipstick test [non-chronic kidney disease (CKD) participants]. Clinical characteristics at kidney biopsy of patients with IgA nephropathy and those at the study recruitment of non-CKD participants were included as covariates in multivariate logistic regression models.

RESULTS

Among 31 gene polymorphisms with ≥5% of minor genotype in non-CKD participants, methionine synthase MTR A2756G (D919G) was significantly associated with IgA nephropathy using χ(2) test even after controlling for family-wise error rate by the method of Bonferroni (P = 0.044). A multivariate nonconditional logistic regression model identified MTR A2756G as a significant contributor of IgA nephropathy [2756AG and GG versus AA, odds ratio 0.42 (95% confidence interval 0.25-0.69) and 0.21 (95% confidence interval 0.06-0.68), P(trend) < 0.001]. After each patient with IgA nephropathy was randomly matched to a non-CKD participant on age (±5 years), gender, mean arterial pressure (±5 mmHg) and eGFR (±5 mL/min/1.73 m(2)), a multivariate conditional logistic regression model also verified their significant association [odds ratio 0.42 (95% confidence interval 0.18-1.00) and odds ratio 0.09 (95% confidence interval 0.01-0.73), P(trend) = 0.004]. MTR A2756G was not associated with slope of eGFR (mL/min/1.73 m(2)/year) in 230 patients with IgA nephropathy.

CONCLUSION

MTR A2756G was associated with the development, but not progression, of IgA nephropathy.

Aliskiren combined with losartan in immunoglobulin A nephropathy: an open-labeled pilot study

BACKGROUND

Aliskiren is a relatively new oral direct renin inhibitor (DRI) that has been increasingly used for the treatment of diabetic nephropathy and hypertension. Its potential efficacy in nondiabetic chronic kidney diseases that are driven by renin-angiotensin system activation remains to be explored.

METHODS

From a teaching and regional hospital in Hong Kong between July 2009 and March 2010, patients with biopsy-proven immunoglobulin A nephropathy (IgAN) in whom the ratio of protein to creatinine, as measured in early morning urine samples, remained >113 mg/mmol (1000 mg/g), despite receiving the maximum recommended dose of losartan (100 mg daily) were recruited to receive additional DRI treatment. They were followed prospectively for 12 months with changes in proteinuria as the main outcome measure.

RESULTS

Twenty-five consecutive patients were enrolled. Treatment with aliskiren for 12 months reduced the mean urinary protein-to-creatinine ratio by 26.3% (95% confidence interval, 20.1-43.6; P = 0.001 versus baseline), with a reduction of ≥ 50% in 24% of patients. There were significant reductions in plasma renin activity (P < 0.0001) and serum interleukin-6 (P < 0.05) and transforming growth factor-β (P = 0.01) levels, compared with baseline. Two patients (8%) developed mild allergic reactions and six (24%) had transient hyperkalemia (K >5.5 mmol/L) during the study.

CONCLUSION

Aliskiren confers an antiproteinuric effect in IgAN patients with significant residual proteinuria, despite receiving the recommended renoprotective treatment. Further prospective randomized trials are warranted to examine its long-term renoprotective potential. This trial is registered with the ClinicalTrials.gov number NCT00922311.

Proteomic analysis of urinary exosomes from patients of early IgA nephropathy and thin basement membrane nephropathy

To identify biomarker candidates associated with early IgA nephropathy (IgAN) and thin basement membrane nephropathy (TBMN), the most common causes presenting isolated hematuria in childhood, a proteomic approach of urinary exosomes from early IgAN and TBMN patients was introduced. The proteomic results from the patients were compared with a normal group to understand the pathophysiological processes associated with these diseases at the protein level. The urinary exosomes, which reflect pathophysiological processes, collected from three groups of young adults (early IgAN, TBMN, and normal) were trypsin-digested using a gel-assisted protocol, and quantified by label-free LC-MS/MS, using an MS(E) mode. A total of 1877 urinary exosome proteins, including cytoplasmic, membrane, and vesicle trafficking proteins, were identified. Among the differentially expressed proteins, four proteins (aminopeptidase N, vasorin precursor, α-1-antitrypsin, and ceruloplasmin) were selected as biomarker candidates to differentiate early IgAN from TBMN. We confirmed the protein levels of the four biomarker candidates by semi-quantitative immunoblot analysis in urinary exosomes independently prepared from other patients, including older adult groups. Further clinical studies are needed to investigate the diagnostic and prognostic value of these urinary markers for early IgAN and TBMN. Taken together, this study showed the possibility of identifying biomarker candidates for human urinary diseases using urinary exosomes and might help to understand the pathophysiology of early IgAN and TBMN at the protein level.

CD248+ stromal cells are associated with progressive chronic kidney disease

Stromal fibroblasts are the primary cells of the kidney that produce fibrotic matrix. CD248 is a stromal marker expressed on fibroblasts and pericytes within the human kidney. Here, we tested whether CD248 expression in the kidney colocalizes with fibrosis and if it is associated with known determinants of chronic kidney disease (CKD). CD248 expression was located and quantified in situ by immunohistochemistry in kidney biopsies from 93 patients with IgA nephropathy and compared with 22 archived biopsies encompassing normal kidney tissue as control. In normal kidney tissue, CD248 was expressed by resident pericytes, stromal fibroblasts, and was upregulated in human CKD. The expression was linked to known determinants of renal progression. This relationship was maintained in a multivariate analysis with CD248 expression linked to renal survival. CD248 was expressed by a population of α-smooth muscle actin (SMA)(+) myofibroblasts and α-SMA(-) stromal cells but not expressed on CD45(+) leukocytes. Thus, CD248 defines a subset of stromal cells, including but not limited to some myofibroblasts, linked to albuminuria and tubulointerstitial damage during tissue remodeling in CKD.

Role of glomerular proteoglycans in IgA nephropathy

Mesangial matrix expansion is a prominent feature of the most common form of glomerulonephritis, IgA nephropathy (IgAN). To find molecular markers and improve the understanding of the disease, the gene and protein expression of proteoglycans were investigated in biopsies from IgAN patients and correlated to clinical and morphological data. We collected and microdissected renal biopsies from IgAN patients (n = 19) and from healthy kidney donors (n = 14). Patients were followed for an average time of 4 years and blood pressure was according to target guidelines. Distinct patterns of gene expression were seen in glomerular and tubulo-interstitial cells. Three of the proteoglycans investigated were found to be of special interest and upregulated in glomeruli: perlecan, decorin and biglycan. Perlecan gene expression negatively correlated to albumin excretion and progress of the disease. Abundant decorin protein expression was found in sclerotic glomeruli, but not in unaffected glomeruli from IgAN patients or in controls. Transforming growth factor beta (TGF-β), known to interact with perlecan, decorin and biglycan, were upregulated both on gene and protein level in the glomeruli. This study provides further insight into the molecular mechanisms involved in mesangial matrix expansion in IgAN. We conclude that perlecan is a possible prognostic marker for patients with IgAN. In addition, the up-regulation of biglycan and decorin, as well as TGF-β itself, indicate that regulation of TGF-β, and other profibrotic markers plays a role in IgAN pathology.

In vivo activity of epoxide hydrolase according to sequence variation affects the progression of human IgA nephropathy

Epoxyeicosatrienoic acid (EET) regulates the functional integrity of the endothelium. It is hypothesized that the activity of epoxide hydrolase (EPHX2), which determines EET concentration through hydrolysis, may affect the progression of glomerulonephritis. Here, we evaluated the relationship between genetic variations, the in vivo activity of EPHX2, and progression of IgA nephropathy (IgAN). Three single-nucleotide polymorphisms (SNPs) [rs41507953 (K55R), rs751141 (R287Q), and rs1042032] were traced in 401 IgAN patients and 402 normal healthy controls. The in vivo activity of EPHX2 was assessed by measuring substrates/metabolites of the enzyme. None of the polymorphism frequencies differed significantly between patients and controls. However, patients carrying the variant allele (A) of rs751141 possessed better kidney survival than those with the wild-type allele (G; P < 0.001). This association remained significant after adjustment for several risk factors (hazard ratio 1.83, 95% confidence interval 1.13-2.96, P = 0.014). Vascular damage was more prominent in kidney biopsies from patients carrying the G allele of rs751141. The in vivo activity of EPHX2, assessed by the epoxyoctadecenoic acid/dihydroxyoctadecenoic acid ratio using liquid chromatography/mass spectrometry analysis, was elevated in patients with the G allele. The expression of EPHX2 in the human kidney was independent of the sequence variation of the rs751141 allele. Variant rs41507953 was not present in this cohort, and rs1042032 was not associated with progression. Thus the specific measures which regulate EPHX2 activity should be designed for potential therapeutics.