Primary IgA nephropathy: new insights into pathogenesis

The Association of Low Hemoglobin Levels with IgA Nephropathy Progression: A Two-Center Cohort Study of 1,828 Cases

AIM

To investigate the relationship between hemoglobin levels and the progression of IgA nephropathy (IgAN).

METHODS

In a two-center cohort of 1,828 cases with biopsy-proven IgAN, we examined the association of hemoglobin levels with the primary outcome of a composite of all-cause mortality or kidney failure defined as a 40% decline in eGFR, or ESKD (defined as eGFR <15 mL/min/1.73 m2 or need for kidney replacement therapy including hemodialysis, peritoneal dialysis, or kidney transplantation), or the outcome of kidney failure, assessed using Cox and logistic regression models, respectively, with adjustment for confounders.

RESULTS

At baseline, mean age, eGFR, and hemoglobin levels were 33.75 ± 11.03 years, 99.70 ± 30.40 mL/min/1.73 m2, and 123.47 ± 18.36 g/L, respectively. During a median of approximately 7-year follow-up, 183 cases reached the composite outcome. After adjustment for demographic and IgAN-specific covariates and treatments, a lower quartile of hemoglobin was nonlinearly associated with an increased risk of the primary outcome or kidney failure in the Cox proportional hazards models (primary outcome: HR for quartile 3 vs. 4, 1.37; 95% CI, 0.83-2.25; HR for quartile 2 vs. 4, 1.18; 95% CI, 0.68-2.07; HR for quartile 1 vs. 4, 1.91; 95% CI, 1.15-3.17; kidney failure: HR for quartile 3 vs. 4, 1.39; 95% CI, 0.84-2.31; HR for quartile 2 vs. 4, 1.20; 95% CI, 0.68-2.11; HR for quartile 1 vs. 4, 1.83; 95% CI, 1.09-3.07) in the fully adjusted model. Then, hemoglobin levels were transformed to a binary variable for fitting the model according to the criteria for anemia of 110 g/L in the women and 120 g/L in men in China. The participants in the anemia group had an increased risk of developing outcomes compared with the nonanemia group in both genders (primary outcome: male: HR, 1.64; 95% CI, 1.01-2.68; female: HR, 1.68; 95% CI, 1.02-2.76; kidney failure: male: HR, 1.60; 95% CI, 0.97-2.64; female: HR, 1.58; 95% CI, 0.95-2.61) in the fully adjusted model.

CONCLUSIONS

A low level of hemoglobin was nonlinearly associated with IgAN progression. The anemic IgAN patients presented a higher risk of developing poor outcomes compared with the nonanemic patients.

Renal miR-148b is associated with megalin down-regulation in IgA nephropathy

Megalin is essential for proximal tubule reabsorption of filtered proteins, hormones, and vitamins, and its dysfunction has been reported in IgA nephropathy (IgAN). miR-148b has been shown to regulate renal megalin expression in vitro and in animal models of kidney disease. We examined a potential role of miR-148b and other miRNAs in regulating megalin expression in IgAN by analyzing the association between megalin and miR-148b, miR-21, miR-146a, and miR-192 expression. Quantitative PCR (qPCR) analysis identified a marked increase in renal levels of several miRNAs, including miR-148b, miR-21, miR-146a, and a significant decrease in megalin mRNA levels in IgAN patients when compared with normal controls. By multiple linear regression analysis, however, only renal miR-148b was independently associated with megalin mRNA levels in IgAN. Proximal tubule megalin expression was further evaluated by immunofluorescence labeling of biopsies from the patients. The megalin expression was significantly lower in patients with highest levels of renal miR-148b compared with patients with lowest levels. To examine the direct effects of the miRNAs on megalin and other membrane proteins expression, proximal tubule LLC-PK1 cells were transfected with miR-148b, miR-21, miR-146a, or miR-192 mimics. Transfection with miR-148b mimic, but not the other three miRNA mimics inhibited endogenous megalin mRNA expression. No significant effect of any of the four miRNA mimics was observed on cubilin or aquaporin 1 (AQP1) mRNA expression. The findings suggest that miR-148b negatively regulates megalin expression in IgAN, which may affect renal uptake and metabolism of essential substances.

The mTOR/p70S6K1 signaling pathway in renal fibrosis of children with immunoglobulin A nephropathy

Aim:

The purpose of this study was to explore whether mTOR/p70S6K1 signaling is activated in renal fibrosis of immunoglobulin A nephropathy.

Methods:

Seventy-two children with immunoglobulin A nephropathy were divided into three groups according to their clinical features and pathological grades. Six normal renal specimens were included in the control group. The expression levels of angiotensin II, mTOR, p70S6K1, E-cadherin, and α-smooth muscle actin in renal tissues were determined by immunohistochemistry method, the potential correlations of these indexes and relationship between these indexes and the clinicopathological indexes were analyzed.

Results:

Compared to the control group, the expression levels of angiotensin II, mTOR, p70S6K1, and α-smooth muscle actin were significantly higher and the expression levels of E-cadherin were lower both in glomeruli and tubulointerstitium of immunoglobulin A nephropathy children. And the most significant differences were found in the nephrotic syndrome group and pathological grade IV group. In immunoglobulin A nephropathy renal tissues, the expression levels of angiotensin II in glomeruli and tubulointerstitium were both positively correlated with the expression levels of mTOR and α- smooth muscle actin, and negatively correlated with the expression levels of E-cadherin.

Conclusion:

The mTOR/p70S6K1 signaling was activated in renal tissues of children with immunoglobulin A nephropathy, and future studies will need to address the mechanism of mTOR/p70S6K1 signaling in the progress of renal fibrosis in immunoglobulin A nephropathy.

Should we really STOP treating patients with IgA nephropathy with steroids?

IgA nephropathy (IgAN) is the most common primary glomerulonephritis all over the world. Once considered as a benign disease, today the scientific community is aware that a significant percentage of patients eventually progress to end-stage kidney disease (ESKD). The rate of progression is often very slow. Since 1980s, several therapeutic attempts have been made with steroids. Despite different molecules, doses, and lengths of treatment, the majority of uncontrolled and controlled studies found benefits in terms of proteinuria reduction and reduction of the risk of ESKD. This was obtained with reasonable safety and tolerability, especially when steroids are given at relatively low dose and for a period not exceeding 6 months. Recently, two randomized controlled trials have questioned the efficacy and safety of steroid therapy in IgAN. However, these trials have many drawbacks that are to be considered when interpreting the findings.

The features in IgA-dominant infection-related glomerulonephritis distinct from IgA nephropathy: a single-center study

BACKGROUND

IgA-dominant infection-related glomerulonephritis (IgA-IRGN) is a unique form of IRGN, which needs to be distinguished from IgA nephropathy (IgAN).

METHODS

Thirteen patients with IgA-IRGN (IgA-IRGN group) and 122 with IgAN (IgAN group) were selected from 1788 patients who underwent kidney biopsy between 2000 and 2015 in Kitano Hospital. Data selected included clinical and serological parameters; light and electron microscope findings; immunofluorescence findings; and prognostic parameters like renal and overall survival and creatinine increase by > 50%. In addition, a 26-patient IgAN cohort (matching-IgAN), matching with IgA-IRGN group with respect to age, sex, estimated glomerular filtration rate (eGFR), and proteinuria was segregated for comparison.

RESULTS

Compared to IgAN group, IgA-IRGN group were older, had lower hemoglobin, higher CRP, lower eGFR, heavier proteinuria, lower serum albumin, and higher serum IgG and IgA levels (p < 0.05). Endocapillary hypercellularity, deposition of immune complexes along the glomerular capillary wall, and subendothelial and subepithelial electron dense deposits were more frequently observed (p < 0.05); and they were more susceptible to renal dysfunction and poorer prognosis. After propensity score-matching, serum albumin was significantly lower in the IgA-IRGN group. Significantly subendothelial and subepithelial deposits were frequently observed in this group. Matching-IgAN group showed relatively advanced sclerotic lesions with more global sclerosis and fibrous crescent.

CONCLUSION

Local inflammation involved glomerular capillary wall in IgA-IRGN, in contrast to relatively chronic and sclerotic renal lesion in IgAN, might result in poorer prognosis in former, even under indistinguishable condition of deteriorated renal function and proteinuria.

Increased Abundance of Plasmacytoid Dendritic Cells and Interferon-Alpha Induces Plasma Cell Differentiation in Patients of IgA Nephropathy

The roles of pDC and IFN-α have not been well defined in IgA nephropathy (IgAN). In this study, we investigated the abundance of pDCs and IFN-α in IgAN patients and the response of peripheral blood mononuclear cells (PBMCs) after stimulation of the pDC-preferred TLR9 ligand CpG2216. The effects of IFN-α on plasma cell differentiation and leukocyte migration were also investigated. Here, we found that the percentages of pDCs were increased in PBMCs of IgAN patients, than in those of healthy controls. Plasma levels of IFN-α proteins and abundance of plasma cells were higher in IgAN patients than in healthy donors. Plasma IFN-α levels were positively associated with proteinuria, renal IgM deposition, and renal tubular atrophy/interstitial fibrosis grade in IgAN patients. Ex vivo activation of TLR9 on pDCs resulted in increased IFN-α production and enhanced plasma cell differentiation in IgAN patients as compared with healthy donors. IFN-α treatment led to increased plasma cell differentiation in vitro. IFN-α also significantly promoted expression of chemokines IP-10 and MCP-1 in human mesangial cells, which subsequently facilitated the transendothelial migration of human CD4⁺ and CD14⁺ cells. In conclusion, pDC and its secreted cytokine IFN-α may play important roles in pathological changes of IgA nephropathy.

Immunoglobulin a nephropathy: Pathological markers of renal survival in paediatric patients

IgA nephropathy (IgAN) is one of the leading causes of glomerulonephritis characterized by the findings of IgA and IgG immune deposits in the mesangium of kidney biopsies from patients with persistent microscopic haematuria. IgAN is frequently detected among adolescents and young adults. IgAN presents a highly variable course that includes a spectrum from a very mild disease to end-stage renal disease (ESRD). There are several clinical and histological factors that strongly determined the final outcome of patients with IgAN. Pathological variables associated with unfavorable outcomes are mesangial hypercellularity, segmental glomerulosclerosis, endocapillary hypercellularity and interstitial fibrosis/tubular atrophy, according to the Oxford classification. Moreover, some studies also suggest a role for complement activation in the pathogenesis of IgAN. In this regard, staining for C4d may be an independent risk factor for the development of ESRD in IgAN. Despite the growing number of studies assessing IgAN risk factors, this kind of investigation in paediatric patients is still very limited. The aim of this article is to revise pathological markers related to deterioration of renal function in paediatric patients with IgAN, particularly those that can independently affect renal survival.

Expression profile of BAFF in peripheral blood from patients of IgA nephropathy: Correlation with clinical features and Streptococcus pyogenes infection

B cells are critically important for the pathogenesis of IgA nephropathy (IgAN). The present study aimed to investigate the abundance of B cell activating factor (BAFF), which belongs to the tumor necrosis factor superfamily, in the peripheral blood of patients with IgAN. The different forms of BAFF in peripheral blood and its association with clinical features and immunological factors were analyzed. mRNA levels of BAFF and other associated genes in the peripheral blood mononuclear cells (PBMCs) of patients with IgAN and controls were analyzed by quantitative polymerase chain reaction. Cellular BAFF proteins in PBMCs and plasma soluble BAFF proteins were measured by western blot analysis and ELISA, respectively. PBMCs from patients were stimulated with Streptococcus pyogenes (S. pyogenes) ex vivo for the BAFF secretion assay. The data demonstrated that, although mRNA levels of BAFF in PBMC were not significantly increased in patients with IgAN, they were positively associated with those of a proliferation inducing ligand (APRIL), Toll‑like receptor (TLR)2, TLR4 and TLR7. The cellular BAFF protein in PBMCs was not upregulated. Plasma BAFF protein levels in patients with IgAN (n=76) were significantly decreased compared with controls. However, plasma BAFF levels were positively associated with serum creatinine, proteinuria, uric acid and group A Streptococcus infection index in patients with IgAN. In patients with IgAN, plasma BAFF concentrations were markedly higher in those with more severe renal tubular atrophy/interstitial fibrosis and global glomerulosclerosis. Furthermore, BAFF production in PBMCs of patients with IgAN was increased following S. pyogenes stimulation ex vivo. In conclusion, plasma BAFF levels in patients with IgAN were associated with renal function and disease activity. S. pyogenes infection was closely associated with BAFF production in patients with IgAN.

Emerging therapies in immunoglobulin A nephropathy

Despite advances in our understanding of immunoglobulin A nephropathy (IgAN) over the past decade, there are currently no specific therapies capable of targeting key pathways involved in the pathogenesis of the disease. Recent studies have, however, provided new insights into important molecular pathways that are likely to be amenable to therapeutic manipulation in the future. Specifically, a deeper understanding of the role of mucosal immunity, B-cell activation and mesangial cell activation in IgAN has provided the impetus for a number of exciting phase II/III clinical trials in IgAN. In this review, we examine some of these on-going studies, first examining studies that clarify the role of traditional immunosuppression in IgAN, then focusing on novel therapies in early clinical studies, looking closely at the rationale for these agents in relation to our current understanding of the pathogenesis of IgAN. Finally, we examine emerging pathways and therapeutic agents that have the potential to be developed as novel therapies in the coming years. It is hoped that as we continue to develop a greater understanding of IgAN, emerging therapies will soon become a reality in the day-to-day treatment of patients with IgAN.

Biologics for the treatment of autoimmune renal diseases

Biological therapeutics (biologics) that target autoimmune responses and inflammatory injury pathways have a marked beneficial impact on the management of many chronic diseases, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, and ankylosing spondylitis. Accumulating data suggest that a growing number of renal diseases result from autoimmune injury - including lupus nephritis, IgA nephropathy, anti-neutrophil cytoplasmic antibody-associated glomerulonephritis, autoimmune (formerly idiopathic) membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and C3 nephropathy - and one can speculate that biologics might also be applicable to these diseases. As many autoimmune renal diseases are relatively uncommon, with long natural histories and diverse outcomes, clinical trials that aim to validate potentially useful biologics are difficult to design and/or perform. Some excellent consortia are undertaking cohort studies and clinical trials, but more multicentre international collaborations are needed to advance the introduction of new biologics to patients with autoimmune renal disorders. This Review discusses the key molecules that direct injurious inflammation and the biologics that are available to modulate them. The opportunities and challenges for the introduction of relevant biologics into treatment protocols for autoimmune renal diseases are also discussed.

IgA nephropathy in Brazil: apropos of 600 cases

IgA nephropathy (IgAN) is th e commonest primary glomerular disease worldwide. Studies on its prevalence in Brazil are however scarce. Databases and clinical records from 10 reference centres were retrospectively reviewed. Clinical and laboratory features at the moment of the biopsy were retrieved (age, gender, presence of hematuria, serum creatinine [mg/dL], proteinuria [g/24 h]). Renal biopsy findings were classified according to Haas single grade classification scheme and the Oxford Classification of IgAN. 600 cases of IgAN were identified, of which 568 (94.7 %) were on native kidneys. Male to female ratio was 1.24:1. Patients averaged 32.76 ± 15.12 years old (range 4–89, median 32). Proteinuria and hematuria were observed, respectively in 56.63 and 72.29 % of patients. The association of both these findings occurred in 37.95 % of the cases. Serum creatinine averaged 1.65 ± 0.67 mg/dL (median 1.5 mg/dL) at diagnosis. Segmental sclerosis and mesangial hypercellularity were the main glomerular findings (47.6 and 46.2 %) The commonest combination by Oxford Classification of IgAN, was M0 E0 S0 T0 (22.4 %). Chronic tubulo-interstitial lesions with an extension wider than 25 % of the renal cortex could be identified in 32.2 % of the cases. Tubular atrophy and interstitial fibrosis were more strongly associated with higher 24-h proteinuria and serum creatinine levels. Segmental sclerosis (S1) showed a stronger tendency of association with the presence of tubulo-interstitial lesions (T1 and T2) than other glomerular variables. To the best of our knowledge this is the largest series of IgAN in Brazil. It depicts the main biopsy findings and their possible clinical correlates. Our set of data is comparable to previous reports.

Update on immunoglobulin A nephropathy, Part I: Pathophysiology

Immunoglobulin A (IgA) nephropathy is one of the most common glomerulonephritis and its frequency is probably underestimated because in most patients the disease has an indolent course and the kidney biopsy is essential for the diagnosis. In the last years its pathogenesis has been better identified even if still now several questions remain to be answered. The genetic wide association studies have allowed to identifying the relevance of genetics and several putative genes have been identified. The genetics has also allowed explaining why some ancestral groups are affected with higher frequency. To date is clear that IgA nephropathy is related to auto antibodies against immunoglobulin A1 (IgA1) with poor O-glycosylation. The role of mucosal infections is confirmed, but which are the pathogens involved and which is the role of Toll-like receptor polymorphism is less clear. Similarly to date whether the disease is due to the circulating immunocomplexes deposition on the mesangium or whether the antigen is already present on the mesangial cell as a “lanthanic” deposition remains to be clarified. Finally also the link between the mesangial and the podocyte injury and the tubulointerstitial scarring, as well as the mechanisms involved need to be better clarified.

Extracapillary proliferation in IgA nephropathy; recent findings and new ideas

Context: IgA nephropathy (IgAN) is an autoimmune disorder and is the most common form of primary glomerulonephritis (GN) worldwide.

Evidence Acquisitions: Directory of Open Access Journals (DOAJ), Google Scholar, PubMed (NLM), LISTA (EBSCO) and Web of Science have been searched.

Results: It is a slowly progressing disorder that leads to end-stage renal disease (ESRD) in up to 50% of the patients within 25 years of the onset of the disease. IgAN is defined by predominant IgA deposition in the mesangial area on immunofluorescence (IF) microscopy. Its histology varies from mild focal segmental proliferation of mesangial cells to severe diffuse global proliferation with extracapillary proliferation (crescent formation). The Oxford classification, designed in 2009, is a new classification for the evaluation of morphologic lesions of IgAN. This classification, containing four pathology variables, was found to have prognostic implications. The variables included are mesangial hypercellularity (M), endocapillary proliferation (E), segmental glomerulosclerosis (S) and the proportion of interstitial fibrosis and tubular atrophy (T). However, crescents were not included in the Oxford classification.

Conclusions: In this mini-review, we describe the recent publications about the significance of extracapillary proliferation in IgAN and we conclude that, there is much controversy about the role of extracapillary proliferation as a significant prognostic factor in IgAN. Hence, it is important to re-consider crescents in IgAN patients. Therefore, we suggest further investigations on this aspect of IgAN disease.

Significance of urinary full-length megalin in patients with IgA nephropathy

Background and Objectives

Megalin is highly expressed at the apical membranes of proximal tubular epithelial cells. A urinary full-length megalin (C-megalin) assay is linked to the severity of diabetic nephropathy in type 2 diabetes. This study examined the relationship between levels of urinary C-megalin and histological findings in adult patients with IgA nephropathy (IgAN).

Design, Setting, Participants, & Measurements

Urine samples voided in the morning on the day of renal biopsy were obtained from 73 patients with IgAN (29 men and 44 women; mean age, 33 years) and 5 patients with membranous nephropathy (MN). Renal pathologic variables were analyzed using the Oxford classification of IgAN, the Shigematsu classification and the Clinical Guidelines of IgAN in Japan. The levels of urinary C-megalin were measured by sandwich ELISA.

Results

Histological analysis based on the Oxford classification revealed that the levels of urinary C-megalin were correlated with mesangial hypercellularity in IgAN patients (OR = 1.76, 95% CI: 1.04–3.27, P<0.05). There was a significant correlation between the levels of urinary C-megalin and the severity of chronic extracapillary abnormalities according to the Shigematsu classification in IgAN patients (β = 0.33, P = 0.008). The levels of urinary C-megalin were significantly higher in all risk levels of IgAN patients requiring dialysis using the Clinical Guidelines of IgAN in Japan than in the control group. The levels of urinary C-megalin were significantly higher in the high risk and very high risk grades than in the low risk grade (P<0.05). The levels of urinary C-megalin were significantly higher in MN patients compared to the control group.

Conclusions

The levels of urinary C-megalin are associated with histological abnormalities in adult IgAN patients. There is a possibility that urinary C-megalin is an independent predictor of disease progression of IgAN. In addition, our results suggest that urinary C-megalin is a marker of glomerular abnormalities in various glomerular diseases as well as IgAN.

Effect of tonsillectomy and its timing on renal outcomes in Caucasian IgA nephropathy patients

PURPOSE

The role of tonsillectomy in the treatment of IgA nephropathy in Caucasian patients is controversial.

METHODS

A retrospective cohort study was conducted in 264 patients with biopsy-proven primary IgA nephropathy to examine the association between tonsillectomy and long-term renal survival, defined as the incidence of estimated glomerular filtration rates (eGFRs) of ≤30 ml/min/1.73 m(2) or end-stage renal disease (the composite of initiation of dialysis treatment or renal transplantation). The association of tonsillectomy with renal end-points was examined using the Kaplan-Meier method and Cox models.

RESULTS

One-hundred and sixty-six patients did not undergo tonsillectomy (Group I, follow-up 130 ± 101 months) and 98 patients underwent tonsillectomy (Group II, follow-up 170 ± 124 months). The mean renal survival time was significantly longer for both end-points between those patients who underwent tonsillectomy (Group II) versus patients without tonsillectomy (Group I) (p < 0.001 and p = 0.005). The mean renal survival time was significantly longer for both end-points between those patients who had macrohaematuric episodes versus patients who had no macrohaematuric episodes (p = 0.035 and p = 0.019). Tonsillectomy, baseline eGFR and 24-h proteinuria were independent risk factors for both renal end-points.

CONCLUSION

Tonsillectomy may delay the progression of IgA nephropathy mainly in IgA nephropathy patients with macrohaematuria. Prospective investigation of the protective role of tonsillectomy in Caucasian patients is needed.

Association of FOS-like antigen 1 promoter polymorphism with podocyte foot process effacement in immunoglobulin A nephropathy patients

BACKGROUND

FOS has been implicated in the progression of renal disease including IgAN. In this study, we investigated whether polymorphisms of FOS family genes [FOS, FOSB, FOS-like antigen 1 (FOSL1), and FOSL2] were associated with immunoglobulin A nephropathy (IgAN) and the clinical phenotypes of IgAN patients.

METHODS

We genotyped single nucleotide polymorphisms (SNPs) of FOS family genes (rs2239615 and rs7101 for FOS, rs12373539 and rs2282695 for FOSB, rs637571 for FOSL1, and rs925255 for FOSL2) using direct sequencing in 198 IgAN patients and 290 control subjects.

RESULTS

No SNPs were associated with IgAN; however, in the analysis of clinical phenotypes, we found that rs637571 of FOSL1 was associated with podocyte foot process effacement of IgAN in additive (CT vs. TT vs. CC, P = 0.0031, OR = 2.08, 95% CI = 1.27-3.40) and dominant models (CT/TT vs. CC, P = 0.0034, OR = 2.50, 95% CI = 1.35-4.64). The frequency of genotypes containing the T allele was increased in IgAN patients with podocyte foot process effacement, compared to those without podocyte foot process effacement.

CONCLUSION

These results suggest that FOSL1 may be related to IgAN severity.

Urinary uromodulin excretion predicts progression of chronic kidney disease resulting from IgA nephropathy

BACKGROUND

Uromodulin, or Tamm-Horsfall protein, is the most abundant urinary protein in healthy individuals. Recent studies have suggested that uromodulin may play a role in chronic kidney diseases. We examined an IgA nephropathy cohort to determine whether uromodulin plays a role in the progression of IgA nephropathy.

METHODS

A total of 344 IgA nephropathy patients were involved in this study. Morphological changes were evaluated with the Oxford classification of IgA nephropathy. Enzyme Linked Immunosorbent Assay (ELISA) measured the urinary uromodulin level on the renal biopsy day. Follow up was done regularly on 185 patients. Time-average blood pressure, time-average proteinuria, estimated glomerular filtration rate (eGFR) and eGFR decline rate were caculated. Association between the urinary uromodulin level and the eGFR decline rate was analyzed with SPSS 13.0.

RESULTS

We found that lower baseline urinary uromodulin levels (P = 0.03) and higher time-average proteinuria (P = 0.04) were risk factors for rapid eGFR decline in a follow-up subgroup of the IgA nephropathy cohort. Urinary uromodulin level was correlated with tubulointerstitial lesions (P = 0.016). Patients that had more tubular atrophy/interstitial fibrosis on the surface had lower urinary uromodulin levels (P = 0.02).

CONCLUSIONS

Urinary uromodulin level is associated with interstitial fibrosis/tubular atrophy and contributes to eGFR decline in IgA nephropathy.

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

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

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

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

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

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

BACKGROUND AND OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Validation of the Oxford classification of IgA nephropathy for pediatric patients from China

Background

The Oxford classification of IgA nephropathy (IgAN) provides a useful tool for prediction of renal prognosis. However, the application of this classification in children with IgAN needs validation in different patient populations.

Methods

A total of 218 children with IgAN from 7 renal centers in China were enrolled. The inclusion criteria was similar to the original Oxford study.

Results

There were 98 patients (45%) with mesangial proliferation (M1), 51 patients (23%) with endocapillary proliferation (E1), 136 patients (62%) with segmental sclerosis/adhesion lesion (S1), 13 patients (6%) with moderate tubulointerstitial fibrosis (T1 26-50% of cortex scarred), and only 2 patients (1%) with severe tubulointerstitial fibrosis (T2, >50% of cortex scarred). During a median follow-up duration of 56 months, 24 children (12.4%) developed ESRD or 50% decline in renal function. In univariate COX analysis, we found that tubular atrophy/interstitial fibrosis (HR 4.3, 95%CI 1.8-10.5, P < 0.001) and segmental glomerulosclerosis (HR 9.2 1.2-68.6, P = 0.03) were significant predictors of renal outcome. However, mesangial hypercellularity, endocapillary proliferation, crescents, and necrosis were not associated with renal prognosis. In the multivariate COX regression model, none of these pathologic lesions were shown to be independent risk factors of unfavorable renal outcome except for tubular atrophy/interstitial fibrosis (HR 2.9, 95%CI 1.0-7.9 P = 0.04).

Conclusions

We confirmed tubular atrophy/interstitial fibrosis was the only feature independently associated with renal outcomes in Chinese children with IgAN.