Evidence for genetic factors in the development and progression of IgA nephropathy

Global trends and hotspots in IgA nephropathy: a bibliometric analysis and knowledge map visualization from 2012 to 2023

OBJECTIVES

This study aimed to investigate the distribution patterns and research frontiers of international literature and thus present a holistic bibliometric evaluation of the studies on IgA nephropathy.

METHODS

The Web of Science Core Collection database was searched for studies of IgA nephropathy from January 2012 to March 2023. The keywords and references are analyzed by CiteSpace, while the countries and institutions are analyzed by VOSviewer.

RESULTS

A total of 2987 publications on IgA nephropathy were included. The country with the most publications was China (n = 1299), and the institution with the most publications was Peking University (n = 139). The most frequent keywords were IgA nephropathy (n = 2013), Oxford classification (n = 482), and diseases (n = 433). The keywords that continue to burst out at high intensity are multicenter study and gut microbiota. Moreover, the top five references for burst strength were also listed.

CONCLUSIONS

IgA nephropathy has attracted widespread research interest, particularly in high-prevalence areas. From 2012 to 2023, publications on IgA nephropathy show a linear increase. China is the country with the highest number of publications and Peking University is the institution with the highest number of publications. Current research hotspots and frontiers are mainly multicenter studies related to IgA nephropathy and its exploration with gut microbiota. Overall, we have provided a comprehensive scientometric analysis of IgA nephropathy that will inform researchers and healthcare practitioners.

Current Understanding of Complement Proteins as Therapeutic Targets for the Treatment of Immunoglobulin A Nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide and a frequent cause of kidney failure. Currently, the diagnosis necessitates a kidney biopsy, with routine immunofluorescence microscopy revealing IgA as the dominant or co-dominant immunoglobulin in the glomerular immuno-deposits, often with IgG and sometimes IgM or both. Complement protein C3 is observed in most cases. IgAN leads to kidney failure in 20-40% of patients within 20 years of diagnosis and reduces average life expectancy by about 10 years. There is increasing clinical, biochemical, and genetic evidence that the complement system plays a paramount role in the pathogenesis of IgAN. The presence of C3 in the kidney immuno-deposits differentiates the diagnosis of IgAN from subclinical glomerular mesangial IgA deposition. Markers of complement activation via the lectin and alternative pathways in kidney-biopsy specimens are associated with disease activity and are predictive of poor outcome. Levels of select complement proteins in the circulation have also been assessed in patients with IgAN and found to be of prognostic value. Ongoing genetic studies have identified at least 30 loci associated with IgAN. Genes within some of these loci encode complement-system regulating proteins that can interact with immune complexes. The growing appreciation for the central role of complement components in IgAN pathogenesis highlighted these pathways as potential treatment targets and sparked great interest in pharmacological agents targeting the complement cascade for the treatment of IgAN, as evidenced by the plethora of ongoing clinical trials.

Tale of two nephropathies; co-occurring Alport syndrome and IgA nephropathy, a case report

Background

Alport Syndrome and IgA Nephropathy (IgAN) are both disorders that can cause hematuria. Alport syndrome is most commonly an X-linked disease, caused by COL4A5 mutation. Mutations of COL4A3 and COL4A4 on chromosome two are also common causes of Alport syndrome. IgAN is the most common glomerulonephritis worldwide. Though IgAN is usually sporadic, an estimated 15% of cases have an inheritable component. These cases of Familal IgA Nephropathy (FIgAN) can have mutations on genes which are known to cause Alport Syndrome.

Case presentation

We report a case of a 27-year-old man with strong family history of renal disease, who presented with hematuria and new non-nephrotic range proteinuria. Physical exam showed no abnormalities. His creatinine remained persistently elevated, and renal ultrasound exhibited bilaterally increased echogenicity consistent with Chronic Kidney Disease. Twenty-four-hour urinary collection revealed non-nephrotic range proteinuria of 1.4 g, with otherwise negative workup. On biopsy, he had IgA positive immunofluorescent staining as well as moderate interstitial fibrosis and tubular atrophy. Electron microscopy showed a basket-weave pattern of thickening and splitting of the lamina densa-consistent with Alport Syndrome, as well as mesangial expansion with electron-dense deposits -consistent with IgAN.

Conclusions

Mutations of COL4A5 on the X chromosome, as well as mutations of COL4A3 and COL4A4 on chromosome 2, can cause both Alport Syndrome and FIgAN. Genome wide association studies identified certain Angiotensin Converting Enzyme gene polymorphisms as independent risk factors for progression of IgAN. Our Presentation with this co-occurring pathology suggests a new paradigm where Alport Syndrome and FIgAN may represent manifestations of a single disease spectrum rather than two disparate pathologies. Appreciating hematuria through this framework has implications for treatments and genetic counseling. Further genome wide association studies will likely increase our understanding of Alport Syndrome, FIgAN, and other causes of hematuria.

The efficacy and safety of immunosuppressive therapies in the treatment of IgA nephropathy: A network meta-analysis

Immunoglobulin A nephropathy (IgAN) is a common autoimmune glomerulonephritis that can result in end-stage renal disease (ESRD). Whether immunosuppressants are superior or equivalent to supportive care is still controversial. A network meta-analysis was conducted to compare the efficacy and safety of immunosuppressive treatment for IgAN. Medline, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, and EMBASE were searched on December 30, 2018. We used a random-effects model with a Bayesian approach to appraise both renal outcomes and serious adverse effects. Relative risks (RRs) with 95% confidence intervals (CIs) were calculated to present the relative effects. The ranking probabilities were calculated by the surface under the cumulative ranking curve (SUCRA). In total, 24 RCTs comprising 6 interventions were analyzed. Steroids significantly delayed the progression of renal deterioration with acceptable serious adverse effects, compared with supportive care (RR = 0.28, 95% CI = 0.13–0.51, SUCRA = 48.7%). AZA combined with steroids might be an alternative immunosuppressive therapy. Tacrolimus might decrease the proteinuria level (RR = 3.1, 95% CI = 1.2–9.4, SUCRA = 66.5%) but cannot improve renal function, and the side effects of tacrolimus should not be neglected. MMF and CYC showed no superiority in the treatment of IgAN. In summary, steroids might be recommended as the first-line immunosuppressive therapy for IgAN.

A New Vision of IgA Nephropathy: The Missing Link

IgA Nephropathy (IgAN) is a primary glomerulonephritis problem worldwide that develops mainly in the 2nd and 3rd decade of life and reaches end-stage kidney disease after 20 years from the biopsy-proven diagnosis, implying a great socio-economic burden. IgAN may occur in a sporadic or familial form. Studies on familial IgAN have shown that 66% of asymptomatic relatives carry immunological defects such as high IgA serum levels, abnormal spontaneous in vitro production of IgA from peripheral blood mononuclear cells (PBMCs), high serum levels of aberrantly glycosylated IgA1, and an altered PBMC cytokine production profile. Recent findings led us to focus our attention on a new perspective to study the pathogenesis of this disease, and new studies showed the involvement of factors driven by environment, lifestyle or diet that could affect the disease. In this review, we describe the results of studies carried out in IgAN patients derived from genomic and epigenomic studies. Moreover, we discuss the role of the microbiome in the disease. Finally, we suggest a new vision to consider IgA Nephropathy as a disease that is not disconnected from the environment in which we live but influenced, in addition to the genetic background, also by other environmental and behavioral factors that could be useful for developing precision nephrology and personalized therapy.

Association between the <b><i>ACYP2</i></b> Polymorphisms and IgAN Risk in the Chinese Han Population

<b><i>Background/Aims:</i></b> The association between <i>ACYP2</i>(Acylphosphatase 2) polymorphisms and immunoglobulin A nephropathy (IgAN) risk in the Chinese Han population remains unclear. We aimed to evaluate the association between <i>ACYP2</i> polymorphisms and IgAN risk by performing a case-control study. <b><i>Methods:</i></b> Eleven <i>ACYP2</i> single nucleotide polymorphisms (SNPs) from 416 IgAN patients and 495 healthy controls were genotyped using the Sequenom MassARRAY platform. Odds ratio (OR) and 95% confidence interval (CI) were calculated to evaluate the association of <i>ACYP2</i> polymorphisms with IgAN risk. <b><i>Results:</i></b> We observed that rs843720 was significantly associated with an increased risk of IgAN (allele G: OR = 1.23, 95% CI: 1.01–1.49, <i>p</i> = 0.036; dominant model: OR = 1.55, 95% CI: 1.01–2.37, <i>p =</i>0.044; log-additive model: OR = 1.43, 95% CI: 1.04–1.95, <i>p</i> = 0.026) before Bonferroni correction. The SNP rs12615793 was also significantly associated with an increased IgAN risk in the recessive model (OR = 3.33, 95% CI: 1.05–10.51, <i>p</i> = 0.042) before Bonferroni correction. <b><i>Conclusion:</i></b> These findings suggested that polymorphisms (rs843720 and rs12615793) of <i>ACYP2</i> may be pivotal in the development of IgAN. However, more functional and association studies with larger sample sizes should be performed to further validate our results in the future.

The influence of environmental factors on clinical pathological changes of patients with immunoglobulin A nephropathy from different areas of China

OBJECTIVES

The effects of regional characteristics of IgAN patients in different areas of China were investigated.

METHODS

Patients who were identified to have primary IgAN by renal biopsy diagnosis were recruited both from Shaanxi province hospital of traditional Chinese medicine and Guangdong province hospital of traditional Chinese medicine. Besides renal histopathology data, a number of clinical and laboratory data were collected.

RESULTS

It was shown that the frequency of the patients with no mucosal infection in the urinary tract was higher in the Guangzhou group, while the frequencies of upper respiratory tract and biliary infections were lower when compared with those in the Xi'an group. Serum uric acid, alexin C3, creatinine and serum cholesterol concentrations were increased in the Guangzhou group, while triglyceride, glomerular filtration rate, and urine red blood cell count level decreased. IgA + IgM + C3 and IgA + IgG + IgM + C3 were found in most patients of the Xi'an group, whereas IgA + C3, IgA + IgM + C3 and IgA were more frequent in the Guangzhou group.

CONCLUSION

It was found that differential environment, life habits and patterns in the two investigated areas obviously may influence the variable characteristics of IgAN patients.

Genetic polymorphisms in HLA-DP and STAT4 are associated with IgA nephropathy in a Southwest Chinese population

IgA nephropathy (IgAN) is the most common chronic glomerular disease worldwide. Genetic factors are thought to be crucial in the pathogenesis of IgAN. However, few data are available on the relationship between human leucocyte antigen (HLA) and signal transducer and activator of transcription 4 (STAT4) polymorphisms and IgAN susceptibility in the Chinese population. Therefore, we examined HLA-DP/DQ and STAT4 polymorphisms (rs3077, rs9277535, rs7453920 and rs7574865) in a total of 630 subjects including 140 IgAN and 490 healthy controls in Chinese. There were significant associations between IgAN patients and healthy controls in the allele frequency of rs3077, rs9277535 and rs7574865. In addition, the genotypes of rs3077, rs9277535 and rs7574865 were also significantly associated with IgAN under recessive models. Moreover, the haplotypes block AAG, AGG, GAG and GGA in the HLA gene significantly correlated with the risk of IgAN. This is the first study demonstrating the significant associations of SNP rs3077, rs9277535 and rs7574865 and the haplotypes in the HLA gene with the risk of IgAN in a Southwest Chinese population. This research provides a new insight into the significant relationship between HLA-DP and STAT4 polymorphisms and the susceptibility to IgAN.

Determination of IL-1B (rs16944) and IL-6 (rs1800796) genetic polymorphisms in IgA nephropathy in a northwest Chinese Han population

IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis worldwide, but etiology and pathogenesis continue to be poorly understood. Polymorphisms in the cytokine genes may play a role in the etiology and pathogenesis of IgAN. The incidence of different between diverse ethnic groups suggested important genetic influences on its pathogenesis.

We genotype 10 single nucleotide polymorphisms (SNPs) in IL-1B and IL-6 gene using Sequenom Mass-ARRAY technology from 417 IgAN patients and 463 healthy controls of the Chinese Han population. We evaluated these SNPs associated with IgAN utilising the chi-square tests and genetic model analysis.

We identified that the minor alleles of rs16944 (“A”), rs1800796 (“G”) in IL-1B, IL-6 were involved in an increasingly risk of IgAN in allelic model analysis, respectively. The rs16944 in IL-1B and rs1800796 in IL-6 were associated with 1.23-fold (95% CI, 1.02-1.48, P = 0.031) and 1.33-fold (95% CI, 1.11-1.66, P = 0.003) increases in the risk of developing IgAN, respectively. There was only rs1800796 still correlated with IgAN in the allelic model after adjustment by age and gender and the Bonferroni correction. In addition, Haplotype G_rs1800796A _rs2069837G _rs2069840 (P = 0.037) and G _rs1800796A _rs2069837C _rs2069840 (P = 0.042) in IL-6were considered to be associated with increased IgAN risk.

This study verified the IL-6, IL-1B genetic variants polymorphisms contributed to IgAN susceptibility in a Chinese Han population. Although we identified SNPs susceptibility, however, replication studies and functional research are required to confirm the genetic contribution in IgAN.

Association of genetic polymorphisms in IL-1R1 and IL-1R2 genes with IgA nephropathy in the Han Chinese population

Aim

IgA nephropathy (IgAN) is the major cause of end-stage renal disease(ESRD) in Asia and its pathogenesis is influenced by both genetic and environmental factors. Single nucleotide polymorphisms (SNPs) in IL1R1 and IL-1R2 may be associated with susceptibility to IgAN. In this study, we study the association between genetic variants of IL-1R1 and IL-1R2 and IgA nephropathy risk in the Chinese Han population.

Result

In the allelic model analysis, the rs10490571 and rs3917225 were associated with a 1.40-fold, and 1.31-fold increased risk of IgA nephropathy, respectively. In the genetic model analysis, the rs10490571 in IL1R1 was associated with a 1.46-fold increased risk of IgAN in the dominant model and 1.36-fold increased risk in the Log-additive model, respectively. However, the rs3218977 in IL1R2 was associated with a 0.71-fold decrease risk of IgAN in the dominant model and a 0.71–fold decrease risk in the over-dominant model, respectively. We found four SNPs (rs11674595, rs4851521, rs719250, and rs3218896) constructed four haplotypes in the IL1R2 gene and none of the haplotype was significantly associated with risk of IgAN.

Materials and Methods

A case-control study was conducted including 426 nephropathy patients and 463 healthy controls. Chi-squared tests and genetic model were used to evaluate associations.

>Conclusions

These findings suggested that IL-1R1 and IL-1R2 polymorphisms may contribute to the development of IgAN.

A functional variant in NEPH3 gene confers high risk of renal failure in primary hematuric glomerulopathies. Evidence for predisposition to microalbuminuria in the general population

Background

Recent data emphasize that thin basement membrane nephropathy (TBMN) should not be viewed as a form of benign familial hematuria since chronic renal failure (CRF) and even end-stage renal disease (ESRD), is a possible development for a subset of patients on long-term follow-up, through the onset of focal and segmental glomerulosclerosis (FSGS). We hypothesize that genetic modifiers may explain this variability of symptoms.

Methods

We looked in silico for potentially deleterious functional SNPs, using very strict criteria, in all the genes significantly expressed in the slit diaphragm (SD). Two variants were genotyped in a cohort of well-studied adult TBMN patients from 19 Greek-Cypriot families, with a homogeneous genetic background. Patients were categorized as “Severe” or “Mild”, based on the presence or not of proteinuria, CRF and ESRD. A larger pooled cohort (HEMATURIA) of 524 patients, including IgA nephropathy patients, was used for verification. Additionally, three large general population cohorts [Framingham Heart Study (FHS), KORAF4 and SAPHIR] were used to investigate if the NEPH3-V353M variant has any renal effect in the general population.

Results and conclusions

Genotyping for two high-scored variants in 103 TBMN adult patients with founder mutations who were classified as mildly or severely affected, pointed to an association with variant NEPH3-V353M (filtrin). This promising result prompted testing in the larger pooled cohort (HEMATURIA), indicating an association of the 353M variant with disease severity under the dominant model (p = 3.0x10^-3, OR = 6.64 adjusting for gender/age; allelic association: p = 4.2x10^-3 adjusting for patients’ kinships). Subsequently, genotyping 6,531 subjects of the Framingham Heart Study (FHS) revealed an association of the homozygous 353M/M genotype with microalbuminuria (p = 1.0x10^-3). Two further general population cohorts, KORAF4 and SAPHIR confirmed the association, and a meta-analysis of all three cohorts (11,258 individuals) was highly significant (p = 1.3x10^-5, OR = 7.46). Functional studies showed that Neph3 homodimerization and Neph3-Nephrin heterodimerization are disturbed by variant 353M. Additionally, 353M was associated with differential activation of the unfolded protein response pathway, when overexpressed in stressed cultured undifferentiated podocyte cells, thus attesting to its functional significance. Genetics and functional studies support a “rare variant-strong effect” role for NEPH3-V353M, by exerting a negative modifier effect on primary glomerular hematuria. Additionally, genetics studies provide evidence for a role in predisposing homozygous subjects of the general population to micro-albuminuria.

Epidemiology of biopsy-proven glomerulonephritis in Queensland adults

AIM

There is a paucity of data pertaining to the incidence of biopsy-proven glomerulonephritis (GN) in Australia. This retrospective study aims to review the data from all adult native renal biopsies performed in the state of Queensland from 2002 to 2011--comparing results with centres from across the world.

METHODS

Pathology reports of 3697 adult native kidney biopsies were reviewed, of which 2048 had GN diagnoses. Age, gender, clinical indication and histopathology findings were compared.

RESULTS

The average age at biopsy was 48 ± 17 years. Male preponderance was noted overall (∼60%), with lupus nephritis being the only individual GN with female predilection. The average rate of biopsy was 12.04 per hundred thousand people per year (php/yr). Nephrotic and nephritic syndromes comprised approximately 75% of all clinical indications that lead to GN diagnoses. IgA nephropathy (1.41 php/yr) was the most common primary GN followed by focal segmental glomerulosclerosis (1.02 php/yr) and crescentic GN (0.73 php/yr). Diabetic nephropathy (0.84 php/yr), lupus nephritis (0.69 php/yr) and amyloidosis (0.19 php/yr) were the most commonly identified secondary GN.

CONCLUSION

IgA nephropathy is the predominant primary GN in Queensland, and nephrotic syndrome the most common indication for a renal biopsy. While crescentic GN incidence has significantly increased with time, focal segmental glomerulosclerosis incidence has not shown any trend. Incidence of GN overall appears to increase with age. The annual rate of biopsy in this study appears lower than previously published in an Australian population.

Low α-defensin gene copy number increases the risk for IgA nephropathy and renal dysfunction

Although a major source of genetic variation, copy number variations (CNVs) and their involvement in disease development have not been well studied. Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. We performed association analysis of the DEFA1A3 CNV locus in two independent IgAN cohorts of southern Chinese Han (total of 1189 cases and 1187 controls). We discovered three independent copy number associations within the locus: DEFA1A3 [P = 3.99 × 10−9; odds ratio (OR), 0.88], DEFA3 (P = 6.55 × 10−5; OR, 0.82), and a noncoding deletion variant (211bp) (P = 3.50 × 10−16; OR, 0.75) (OR per copy, fixed-effects meta-analysis). While showing strong association with an increased risk for IgAN (P = 9.56 × 10−20), low total copy numbers of the three variants also showed significant association with renal dysfunction in patients with IgAN (P = 0.03; hazards ratio, 3.69; after controlling for the effects of known prognostic factors) and also with increased serum IgA1 (P = 0.02) and galactose-deficient IgA1 (P = 0.03). For replication, we confirmed the associations of DEFA1A3 (P = 4.42 × 10−4; OR, 0.82) and DEFA3 copy numbers (P = 4.30 × 10−3; OR, 0.74) with IgAN in a Caucasian cohort (531 cases and 198 controls) and found the 211bp variant to be much rarer in Caucasians. We also observed an association of the 211bp copy number with membranous nephropathy (P = 1.11 × 10−7; OR, 0.74; in 493 Chinese cases and 500 matched controls), but not with diabetic kidney disease (in 806 Chinese cases and 786 matched controls). By explaining 4.96% of disease risk and influencing renal dysfunction in patients with IgAN, the DEFA1A3 CNV locus may be a potential therapeutic target for developing treatments for this disease.

Genome-wide association study of IgA nephropathy using 23 465 microsatellite markers in a Japanese population

Immunoglobulin A nephropathy (IgAN) is the most common form of primary glomerulonephritis in many parts of the world. Although previous genome-wide association studies (GWAS) identified the major susceptibility loci for IgAN, the causal genes currently remain unknown. We performed a GWAS using 23 465 microsatellite (MS) markers to identify genes related to IgAN in a Japanese population. A pooled sample analysis was conducted in three-stage screenings of three independent case-control populations, and after the final step of individual typing, 11 markers survived. Of these, we focused on two regions on 6p21 and 12q21 because they (i) showed the strongest relationship with IgAN, and (ii) appeared to be highly relevant to IgAN in view of several previous studies. These regions contained the HLA, TSPAN8 and PTPRR genes. This study on GWAS, using >20 000 MS markers, provides a new approach regarding susceptible genes for IgAN for investigators seeking new tools for the prevention and treatment of IgAN.

The Genetics of IgA Nephropathy: An Overview from Western Countries

BACKGROUND

IgA nephropathy (IgAN) is the commonest primary glomerulonephritis worldwide and a significant cause of chronic kidney disease and end-stage renal disease. It is widely accepted that genetic factors play a role in the pathogenesis of IgAN. However, the identity of these genetic factors remains uncertain.

SUMMARY

Critical to all genetic studies is a precise phenotypic definition of the disease. It is well recognised that IgAN displays striking phenotypic variation, raising the possibility that it may not be a single disease and it may not be the same disease in different parts of the world. In this review, we discuss the challenges that this phenotypic variation poses to interpreting genetic data and the current evidence for specific gene involvement in IgAN, focusing particularly on data from European IgAN cohorts.

KEY MESSAGE

With advances in genetic techniques, in particular next-generation sequencing, and an increased understanding of the importance of copy number variations, epigenetics and transcriptomics, it is likely that we will gain a greater understanding of the genetic basis for IgAN. However, due to the lack of consistency in epidemiological clinicopathological studies both within and between continents, this will only be achieved if we are able to more precisely phenotype IgAN populations.

FACTS FROM EAST AND WEST

The reported prevalence of IgAN is higher in Asia than in Europe and North America. However, differences in use of biopsy for the diagnosis of IgAN should be taken into account in analysing data from both East and West. In Europe, IgAN affects men more frequently than women; this is not the case in Asia. Familial IgAN has been more frequently reported in Europe than in Asia. Within Europe, familial IgAN is more evident in southern than in northern populations. Changes in the pattern of serum IgA1 O-glycosylation is a common finding in IgAN patients in the East and West. SNPs within the gene coding for the enzyme C1GALT1 have been reported in Chinese and European patients. However, there is no evidence for a role of gene polymorphism of the C1GALT1 chaperone cosmc in Europeans. Genetic variants in the HLA gene family have been observed in populations from the East and West. Associations between IgAN and variants of the TAP1/PSMB and DEFA genes were observed in Asian but not in Western patients. Association with the angiotensin-converting enzyme gene was seen only in Asian patients.

Variants in Complement Factor H and Complement Factor H-Related Protein Genes, CFHR3 and CFHR1, Affect Complement Activation in IgA Nephropathy

Complement activation is common in patients with IgA nephropathy (IgAN) and associated with disease severity. Our recent genome-wide association study of IgAN identified susceptibility loci on 1q32 containing the complement regulatory protein-encoding genes CFH and CFHR1-5, with rs6677604 in CFH as the top single-nucleotide polymorphism and CFHR3-1 deletion (CFHR3-1∆) as the top signal for copy number variation. In this study, to explore the clinical effects of variation in CFH, CFHR3, and CFHR1 on IgAN susceptibility and progression, we enrolled two populations. Group 1 included 1178 subjects with IgAN and available genome-wide association study data. Group 2 included 365 subjects with IgAN and available clinical follow-up data. In group 1, rs6677604 was associated with mesangial C3 deposition by genotype-phenotype correlation analysis. In group 2, we detected a linkage between the rs6677604-A allele and CFHR3-1∆ and found that the rs6677604-A allele was associated with higher serum levels of CFH and lower levels of the complement activation split product C3a. Furthermore, CFH levels were positively associated with circulating C3 levels and negatively associated with mesangial C3 deposition. Moreover, serum levels of the pathogenic galactose-deficient glycoform of IgA1 were also associated with the degree of mesangial C3 deposition in patients with IgAN. Our findings suggest that genetic variants in CFH, CFHR3, and CFHR1 affect complement activation and thereby, predispose patients to develop IgAN.

Cumulative effects of variants identified by genome-wide association studies in IgA nephropathy

The effect of genetic markers associated with IgA nephropathy on risk of disease in sub-phenotype and progression is uncertain. Data from 2096 Chinese patients were used to create both un-weighted (uw) and weighted (w) genetic risk score (GRS). The association between GRS with disease susceptibility and clinical parameters were assessed. All nine selected single nucleotide polymorphisms (SNPs) were associated with susceptibility to IgAN. uwGRS and wGRS showed a similar fit in disease associations. With every 1-unit increase in the uwGRS, the disease risk increased by approximately 20%; whereas every one standard deviation increase in the wGRS, disease risk increased by approximately 40% ~ 60%. Association between rs3803800 and serum IgA was replicated, and risk groups in GRSs were associated with increased IgA/IgA1 levels. uwGRS9 ≥ 16 was an independent predictor for end stage renal disease (ESRD) in IgAN, with a relative risk of 2.52 (p = 6.68 × 10⁻³). In conclusion, we observed that GRSs comprising nine SNPs identified in a GWAS of IgAN were strongly associated with susceptibility to IgAN. The high risk GRS9 group had a high risk of ESRD in follow-up.

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.

HLA polymorphism and susceptibility to end-stage renal disease in Cantonese patients awaiting kidney transplantation

Background

End-Stage Renal Disease (ESRD) is a worldwide public health problem. Currently, many genome-wide association studies have suggested a potential association between human leukocyte antigen (HLA) and ESRD by uncovering a causal relationship between HLA and glomerulonephritis. However, previous studies, which investigated the HLA polymorphism and its association with ESRD, were performed with the modest data sets and thus might be limited. On the other hand, few researches were conducted to tackle the Chinese population with ESRD. Therefore, this study aims to detect the susceptibilities of HLA polymorphism to ESRD within the Cantonese community, a representative southern population of China.

Methods

From the same region, 4541 ESRD patients who were waiting for kidney transplantation and 3744 healthy volunteer bone marrow donors (controls) were randomly chosen for this study. Polymerase chain reaction-sequence specific primer method was used to analyze the HLA polymorphisms (including HLA-A, HLA-B and HLA-DRB1 loci) in both ESRD patients and controls. The frequencies of alleles at these loci and haplotypes were compared between ESRD patients and controls.

Results

A total of 88 distinct HLA alleles and 1361 HLA A-B-DRB1 haplotypes were detected. The frequencies of five alleles, HLA-A*24, HLA-B*55, HLA-B*54, HLA-B*40(60), HLA-DRB1*04, and one haplotype (HLA-A*11-B*27-DRB1*04) in ESRD patients are significantly higher than those in the controls, respectively.

Conclusions

Five HLA alleles and one haplotype at the HLA-A, HLA-B and HLA-DRB1 loci appear to be associated with ESRD within the Cantonese population.

Urinary prognostic biomarkers and classification of IgA nephropathy by high resolution mass spectrometry coupled with liquid chromatography

IgA nephropathy is the most common cause of primary glomerulonephritis. There are different pathologic biopsy-based scoring systems in use, but there is no consensus among nephrologists yet regarding the best classification method. Our aim was to test urine proteomics as a non-invasive method for classification of IgA nephropathy. This aim was pursued by discovering novel prognostic protein biomarkers in urine, and linking them to pathogenesis of the disease through known signaling and metabolic pathways. 13 urine samples of the patients with biopsy-proven IgA nephropathy were analyzed via two proteomics approaches: nanoflow LC-MS/MS and GeLC-MS/MS. The results of label-free quantification were subjected to multivariate statistical analysis, which could classify patients into two groups, broadly corresponding to the primary and advance stages. The proteome classification correlated well with biopsy-based scoring systems, especially endocapillary hypercellularity score of the Oxford’s classification. Differentially excreted candidate proteins were found as potential prognostic biomarkers: afamin, leucine-rich alpha-2-glycoprotein, ceruloplasmin, alpha-1-microgolbulin, hemopexin, apolipoprotein A-I, complement C3, vitamin D-binding protein, beta-2-microglobulin, and retinol-binding protein 4. Pathway analysis suggested impairment of Extra Cellular Matrix (ECM)-Receptor Interaction pathways as well as activation of complement and coagulation pathway in progression of IgA nephropathy.

Distribution of human leukocyte antigen alleles in systemic lupus erythematosus patients with angiotensin converting enzyme insertion/deletion polymorphism

Systemic Lupus Erythematosus is one of the classic examples of autoimmune diseases among human beings and is a rare disease in Pakistani population. Clinically it is a quite diverse and complicated autoimmune disease in a sense that it involves multiple organs of the body and mimics with other diseases as well. This study focused on the distribution of HLA alleles in SLE patients with ACE I/D Polymorphism. A total of 122 individuals were enrolled in this study, 61 were the SLE patients who fulfilled revised ACR criteria and 61 were the healthy controls. Mean age of SLE patients at diagnosis was 30.35 ± 1.687 years (Range: 12-68 years). ACE gene I/D polymorphism was performed by nested PCR and DNA based HLA typing technique was used. ACE gene I/D polymorphism of Intron16 was studied and found to be involved in the activity of SLE. There is high frequency of HLA-A*01, HLA-B*40, HLA-DRB1*01 alleles in SLE patients with ACE DD genotype. The distribution of HLA-A, -B, -DRB1 alleles was analyzed in SLE patients with various disease phenotypes. HLA-A*01 and HLA-B*40 was the most common allele found in SLE patients with the involvement of skin. HLA-A*01, -A*03, HLA-B*13 and -B*46 were common in SLE patients with arthritis while HLA-A*26 and -A*69 were commonly found in Lupus nephritis cases. SLE patients involving both skin and kidney had an allele HLA-DRB1*01 common in them.

Impact of gene polymorphisms of interleukin-18, transforming growth factor-β, and vascular endothelial growth factor on development of IgA nephropathy and thin glomerular basement membrane disease

Background

We investigated the effects of gene polymorphisms on the development of IgA nephropathy and thin glomerular basement membrane (GBM) disease by analyzing polymorphisms in the interleukin (IL)-18, transforming growth factor (TGF)-β, and vascular endothelial growth factor (VEGF) genes in Korean patients.

Methods

This study included 146 normal individuals and 69 biopsy-proven IgA nephropathy and 44 thin GBM disease patients. The gene polymorphisms −607 A/C and −137 G/C in IL-18, −509C/T and T869C in TGF-β, and −2578C/A and 405C/G in VEGF were investigated in DNA extracted from peripheral blood.

Results

The frequencies of the IL-18 −607CC genotype (43.5% vs. 21.2%, P=0.002, P corrected=0.012) and the VEGF 405 GG genotype (37.7% vs. 21.2%, P=0.002, P corrected=0.012) were significantly increased in the IgA nephropathy group compared with the control group, whereas no significant differences in genotype frequency were observed between the thin GBM disease and control groups. However, there were no significant differences in genotype and allele frequencies between the IgA nephropathy and thin GBM disease groups.

Conclusion

This study did not show any statistically significant differences of six selected gene polymorphisms of the IL-18, TGF-β, and VEGF genes between IgA nephropathy and thin GBM disease. Additional extensive studies are required to clarify the potential role of gene polymorphism to discriminate IgA nephropathy and thin GBM disease without renal biopsy.

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.

The genetic variants at the HLA-DRB1 gene are associated with primary IgA nephropathy in Han Chinese

Background

Immunoglobulin A nephropathy (IgAN), an immune-complex-mediated glomerulonephritis defined immunohistologically by the presence of glomerular IgA deposits, is the most common primary glomerular disease worldwide and a significant cause of end-stage renal disease. Familial clustering of patients with IgAN suggests a genetic predisposition.

Methods

In this study, 192 patients with IgAN and 192 normal controls in the Sichuan cohort and 935 patients with IgAN and 2,103 normal controls in the Beijing cohort were investigated. HLA-DRB1*01–DRB1*10 specificities were genotyped by the PCR–SSP technique in both cohorts. Based on the HLA-DRB1*04-positive results, the subtypes of HLA-DRB1*04 were analyzed using sequencing-based typing (SBT) in 291 IgAN cases and 420 matched controls.

Results

The frequency of HLA-DRB1*04 in the IgAN group was significantly higher than that in the control group (0.129 vs. 0.092, P = 8.29 × 10^-5, odds ratio (OR) =1.381, 95% confidence interval (CI) 1.178–1.619). Other alleles at the HLA-DRB1 locus were observed with no significant differences between the case and control groups. The dominant alleles of the HLA-DRB1*04 subtypes were DRB1*0405 in both cohorts. The frequencies of HLA-DRB1*0405 and 0403 were significantly increased in the patients compared to healthy subjects.

Conclusion

HLA-DRB1*04 was significantly associated with primary IgAN in Chinese population. This result implies that HLA-DRB1 gene plays a major role in primary IgAN.

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.

Search for genetic association between IgA nephropathy and candidate genes selected by function or by gene mapping at loci IGAN2 and IGAN3

BACKGROUND

IgA nephropathy (IgAN) is not generally considered a hereditary disease, even though extensive evidence suggests an undefined genetic influence. Linkage analysis identified a number of genome regions that could contain variations linked to IgAN.

METHODS

In this case-control association study, genes possibly involved in the development of IgAN were investigated. DNA samples from 460 North Italian patients with IgAN and 444 controls were collected. Candidate genes were selected based on their possible functional involvement (6 genes) or because of their location within linkage-identified genomic regions IGAN2 and IGAN3 (5 and 13 genes within chromosome 4q26-31 and 17q12-22, respectively). One hundred and ninety-two tag and functional single-nucleotide polymorphisms (SNPs) were typed with Veracode GoldenGate technology (Illumina).

RESULTS

C1GALT1 showed an association with IgAN (rs1008898: P = 0.0019 and rs7790522: P = 0.0049). Associations were found when the population was stratified by gender (C1GALT1, CD300LG, GRN, ITGA2B, ITGB3 in males and C1GALT1, TRPC3, B4GALNT2 in females) and by age (TLR4, ITGB3 in patients aged <27 years). Furthermore, rs7873784 in TLR4 showed an association with proteinuria (G allele: P = 0.0091; GG genotype: P = 0.0077).

CONCLUSIONS

Age and gender are likely to evidence distinct immunological and inflammatory reactions leading to individual susceptibility to IgAN. Overall, a genetic predisposition to sporadic IgAN was found. We might hypothesize that C1GALT1 and TLR4 polymorphisms influence the risk to develop IgAN and proteinuria, respectively.

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.

Soluble interleukin-2 receptor alfa predicts renal outcome in IgA nephropathy

BACKGROUND

Both systemic and mucosal IgA production are controlled by T lymphocytes and infiltrating T lymphocytes are involved in the progression of interstitial fibrosis in chronic kidney disease (CKD). Since the concentration of soluble interleukin-2 receptor alfa (sIL-2Ra) reflects the degree of T cell activation over time, we studied the impact of interleukin-2 receptor alfa levels on disease progression in patients with biopsy-proven IgA nephropathy (IgAN), a disease in which 20-30% of the patients progress to end-stage renal failure.

METHODS

sIL-2Ra plasma levels were measured in 194 patients (median age 39 years, 70% men) and 84 matched controls. One hundred and seventy-nine of the patients, with an estimated glomerular filtration rate (GFR) of ≥15 mL/min/1.73m(2) at baseline (CKD Stages 1-4), were followed for up to 15 years (median 52 months; range 12-188). sIL-2Ra was evaluated as a risk marker for severe renal progression, here defined by the development of CKD Stage 5 (GFR <15 mL/min/1.73m(2)), a 50% decline in GFR during the follow-up period or a 30% GFR decline within 5 years of follow-up. In 51 patients, upon whom a renal biopsy had been performed within 2 years of IL2-Ra measurement, the biopsies were scored according to the Oxford classification. The correlations between the histopathological findings and the sIL-2Ra levels were examined.

RESULTS

sIL2-Ra levels were significantly higher in patients than in controls (P < 0.001). sIL-2Ra levels in the upper third tertile predicted a severe renal outcome, even after adjustment for the main clinical risk factors: time average albuminuria and GFR at baseline (Relative risk 5.35, P < 0.001). sIL-2Ra levels also correlated significantly to the yearly GFR slope (β = -0.24, P = 0.01). According to the Oxford classification, the presence of >25% tubular atrophy/interstitial fibrosis (T1-2) was associated with higher sIL-2Ra levels, after adjustment for serum creatinine levels, if analysed within 4 months [n = 24, odds ratio (OR) 1.0, P = 0.044] or within 2 years from the kidney biopsy (n = 51, OR 1.0, P = 0.017).

CONCLUSIONS

The plasma levels of sIL-2Ra were predictive of long-term renal disease progression in a large cohort of patients with biopsy-proven IgAN. Further studies are warranted to evaluate if sIL-2Ra levels can feasibly contribute in the monitoring of effects of treatment, aimed to prevent the progression of interstitial fibrosis and progressive glomerulosclerosis in IgAN.

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.

Establishment of a mouse IgA nephropathy model with the MBP-20-peptide fusion protein

Here, we aimed to determine whether immunoglobulin-A nephropathy (IgAN) could be induced in Balb/c mice by immunizing them with a fusion protein (MBP-20 peptide) comprising the maltose-binding protein (MBP) and a 20-amino-acid peptide derived from Staphylococcus aureus. A recombinant plasmid encoding the fusion protein was constructed and expressed in bacterial cells. The synthetic 20-peptide was used to prepare the monoclonal antibody. Balb/c mice were immunized with the MBP-20-peptide fusion protein over a 21-week course before renal histology was examined at the light and electron microscopic levels. Direct immunofluorescence staining with the anti-20-peptide monoclonal antibody was also performed using renal biopsy tissue from human IgAN patients as a comparison. IgA and IgG specific for the 20-peptide in human and mice serum were detected. The IgAN experimental mice developed a clinical and pathological profile that closely resembled that of human IgAN patients, including the induction of hematuria and numerous histopathological features. Levels of IgA and IgG specific for the 20-peptide were significantly increased in serum from the IgAN experimental mice and IgAN patients compared with control mice and non-IgAN patients. In IgAN model mice, the anti-20-peptide antibody labeled glomeruli, while the antibody strongly labeled glomeruli and weakly labeled tubular epithelial cells in renal tissue from human IgAN patients. In conclusion, immunization with an MBP-20-peptide fusion protein is able to induce clinical and pathological features closely resembling IgAN in Balb/c mice, indicating a potentially useful role for the model in the study of IgAN and related diseases.

In vitro enhanced chemotaxis of CD25+ mononuclear cells in patients with familial IgAN through glomerulotubular interactions

Tubulointerstitial infiltration of immunocompetent cells is often associated with a more rapid progression in IgA nephropathy (IgAN). Using an in vitro Transwell coculture system, we examined the chemotactic response of peripheral blood mononuclear cells to proximal tubular epithelial cells (PTEC) following activation by conditioned medium prepared from mesangial cells cultured with macromolecular IgA1 from 60 patients with multiplex familial IgAN (MpIgAN) and 91 of their asymptomatic relatives; 43 patients with sporadic IgAN (SpIgAN) and 90 of their asymptomatic relatives; and 43 healthy subjects. Compared with SpIgAN patients, PTEC activated by conditioned medium from patients with MpIgAN had elevated gene expression of a spectrum of C-C, C-X-C chemokines and proinflammatory cytokines, with prominent expressions of interleukin-6, interleukin-8, and tumor necrosis factor-α. In response to conditioned medium from patients with familial IgAN, there was a significant increase in chemotaxis of CD45+ cells, CD3+, CD4+, CD8+, CD20+ lymphocytes, and monocytes with CD25 expression. Our findings suggest that compared with SpIgAN patients, macromolecular IgA1 taken from MpIgAN patients is more pathogenic to cultured PTEC through a glomerulotubular interaction. A long-term follow-up is needed to better define the prognostic course for familial IgAN and to clarify the risk of developing IgAN in initially asymptomatic relatives from a multiplex IgAN family.

Comprehensive analysis of short peptides in sera from patients with IgA nephropathy

We analyzed serum short peptides comprehensively to know whether they were useful to characterize IgA nephropathy (IgAN). Serum samples from 26 patients with untreated IgAN and 25 healthy donors were tested. Short peptides with molecular weights of approximately 7 kDa, purified from the serum samples by magnetic-beads-based weak cation exchange, were detected by mass spectrometry. Then the peptide peaks detected were subjected to the multivariate data analysis by SIMCA-P+ containing principal component analysis (PCA) and orthogonal partial-least-squares-discriminate analysis (OPLS-DA). A total of 92 peptide peaks were detected in the tested serum samples. The OPLS-DA analysis revealed that the profile of all the peptide peak intensities discriminated the IgAN group and the healthy group completely with a high R2 value (0.919) and a high Q2 value (0.861). Further, the profile of only five peptide peaks was found to discriminate the two groups. By tandem mass spectrometry and database searching, three of the five peptides which increased in the IgAN group were identified as fragments of fibrinogen alpha chain, and the two peptides which increased in the healthy group were identified as fragments of complement C3f and kininogen-1 light chain. Taken together, the profile of the serum short peptides would be useful to discriminate IgAN and healthy conditions. Further, the five peptides may be candidate serum markers for IgAN and may be related to pathogenesis of IgA.

Do the mutations of C1GALT1C1 gene play important roles in the genetic susceptibility to Chinese IgA nephropathy?

Background

The deficiency of β1,3 galactose in hinge region of IgA1 molecule played a pivotal role in pathogenesis of IgA nephropathy (IgAN). Cosmc, encoded by C1GALT1C1 gene, was indispensable to β1,3 galactosylation of IgA1. We designed a serial study to investigate the relationship between the mutations of C1GALT1C1 gene and the genetic susceptibility to IgAN.

Methods

Nine hundred and thirty-eight subjects, including 661 patients with IgAN and 277 healthy controls were enrolled in the study. Firstly, single nucleotide polymorphisms (SNPs) in the promoter region of C1GALT1C1 gene were screened. Then the c.-347-190G>A was analyzed by PCR-restriction fragment length polymorphism (PCR-RFLP) for further case-control association analysis. Secondly the somatic mutations of DNAs from peripheral blood B lymphocytes were detected in 15 patients and 7 normal controls.

Results

No significant association was observed between the different alleles or genotypes of c.-347-190G>A and IgAN. The patients with different genotypes of C1GALT1C1 gene did not significantly associate with clinical manifestations, including hematuria, proteinuria, and serum creatinine of patients with IgAN. There was no somatic mutation detected in total 202 clones of 22 individuals.

Conclusion

The c.-347-190G>A polymorphism and the somatic mutation of encoding region of C1GALT1C1 gene were not significantly related to the genetic susceptibility to IgAN in Northern Chinese population.

Pathological predictors of prognosis in immunoglobulin A nephropathy: a review

PURPOSE OF REVIEW

To provide a review and discussion of histological prognostic indicators in immunoglobulin A (IgA) nephropathy (IgAN).

RECENT FINDINGS

A variety of histological parameters and classifications have been used to attempt to predict prognosis in patients with IgAN. Grading systems used thus far do not consistently provide a useful adjunct to clinical prognostic parameters. This may be due to the variety of grading systems used, to inconsistent patient recruitment processes, and to the use of actuarial renal survival as an end point. This has led to the development of a new IgAN classification proposal by the International IgA Nephropathy Network in conjunction with the Renal Pathological Society. Additional potential markers of disease progression currently under investigation include glomerular parameters such as number and size, markers of podocyte function and of complement activation, inflammatory infiltrates and mediators of tubulointerstitial fibrosis.

SUMMARY

There is a need for an internationally accepted, reproducible and clinically meaningful pathological classification of IgAN. Such a classification is currently being developed. By using only reproducible, single parameters and validating them on a large group of cases from all over the world, it is hoped that a useful clinically predictive tool will be developed.

Aberrant galactosylation of IgA1 is involved in the genetic susceptibility of Chinese patients with IgA nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is associated with genetic and environmental factors, and undergalactosylation of IgA1 in the serum is considered to be a contributor to pathogenesis of IgAN. The present study was conducted to detect the galactose- (Gal) deficient IgA1 level in Chinese IgAN patients and their family members.

METHODS

Sixty-three IgAN patients were enrolled, where 32 first-degree relatives of 19 patients and 44 spouses of 44 patients were recruited. Healthy blood donors (n = 39) were used as normal controls. Biotinylated HAA (Helix aspersa) was utilized to detect the Gal-deficient IgA1 in enzyme-linked immunosorbent assay (ELISA). All the results were corrected by serum IgA1 concentration.

RESULTS

Compared with normal controls, the sera IgA1 of patients and their first-degree relatives demonstrated increased Gal-deficient IgAl level (0.17 +/- 0.09 versus 0.10 +/- 0.04, P = 0.001; 0.14 +/- 0.07 versus 0.10 +/- 0.04, P = 0.028); no significant difference between patients and their first-degree relatives was detected (0.17 +/- 0.09 versus 0.14 +/- 0.07, P = 0.127). In contrast, serum Gal-deficient IgA1 level of IgAN patients was higher than their counterpart spouses and normal controls (0.18 +/- 0.13 versus 0.14 +/- 0.09, P = 0.009; 0.18 +/- 0.13 versus 0.10 +/- 0.04, P = 0.001), while that of patients' spouses was comparable with normal controls (0.14 +/- 0.09 versus 0.10 +/- 0.04, P = 0.075). There was no correlation between clinicopathological data and serum Gal-deficient IgA1 level.

CONCLUSION

The patients with IgAN and their first relatives showed significant higher Gal-deficient IgA1 level than healthy controls, whereas patients' spouses were the same as healthy controls. It can be suggested that the Gal-deficient IgA1 might be inherited in Chinese patients with IgAN.

TRAC variants associate with IgA nephropathy

The T cell receptor alpha constant gene (TRAC) encodes the constant region of the alpha chain for the T cell receptor, and the association of its gene variants with IgA nephropathy remains controversial. The authors resequenced the gene in 100 patients with IgA nephropathy and 100 controls, tested its linkage disequilibrium pattern, constructed haplotypes, and performed association and functional studies. First, the association between TRAC variants and IgA nephropathy was tested in 704 patients and 704 controls. Next, these 704 patients were divided into two independent datasets--310 with family member(s) and 394 single patients--to test the association separately. Results showed that the gene is located in a recombination hot spot, with nine linkage disequilibrium blocks within a 6.9-kb region. There is a hypervariable region with six single-nucleotide polymorphisms (SNPs) in an 85-bp stretch in intron 1. We identified multiple SNPs and two haplotypes that associate with IgA nephropathy (P = 0.0000013-0.0096 by logistic regression for SNPs; P = 0.0003 and P = 0.0398 for haplotype associations). The family-based study replicated both haplotype findings, and the 394 single-patient case-control study replicated the association with haplotype 1 (P = 0.0033). The overtransmitted/observed haplotypes demonstrated reduced transcription activity compared with the undertransmitted/observed haplotypes. In conclusion, this study suggests an association between TRAC variants and susceptibility to IgA nephropathy.

A candidate gene approach to genetic prognostic factors of IgA nephropathy--a result of Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgA Nephropathy (PREDICT-IgAN)

BACKGROUND

Renal prognosis of IgA nephropathy (IgAN) is affected by environmental and genetic factors. Other studies demonstrated that some atherosclerotic disease-related genes were significantly associated with renal prognosis.

METHODS

The Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgAN (PREDICT-IgAN) was a multicentre retrospective observational study to investigate associations between progression of IgAN (a 50% increase of serum creatinine level and slope of eGFR) and a hundred atherosclerotic disease-related gene polymorphisms, mainly single nucleotide polymorphisms (SNPs) in 320 IgAN patients who had more than a normal range of urinary protein (> or =0.25 g/day) at diagnosis.

RESULTS

During 8.3 +/- 4.2 years of a follow-up period, 83 patients (25.9%) developed progression. In log-rank tests, glycoprotein Ia GPIa C807T and G873A and intercellular adhesion molecule-1 ICAM-1 A1548G (K469E) were found to be significantly associated with progression even after adjustment for multiple comparisons by the method of Bonferroni (adjusted P = 0.0174, 0.0176 and 0.0430, respectively). In a multivariate Cox proportional-hazards model, GPIa 807TT (873CC) [versus 807TT, adjusted hazard ratio 2.05 (95% confidence interval 1.13-3.71)] and ICAM-1 1548GG [versus 1548AA, 2.55 (1.40-4.65)] were identified as independent genetic predictors of progression, along with conventional clinical prognostic factors such as eGFR, urinary protein and use of antihypertensives at diagnosis.

CONCLUSIONS

PREDICT-IgAN distinguished GPIa C807T/ G873A and ICAM-1 A1548G from multiple athero- sclerotic disease-related gene polymorphisms by their predictive indicator for progression of IgAN.

Continental variations in IgA nephropathy among Asians

BACKGROUND/AIMS

Local variations in patient demographics and medical practice can contribute to differences in renal outcomes in patients with IgA nephropathy. We report the experiences of two groups of Asians with IgA nephropathy across continents.

MATERIALS AND METHODS

We retrospectively examined two cohorts of Asian patients with IgA nephropathy from The King Chulalongkorn Memorial Hospital registry, Thailand (1994 - 2005), and The Metropolitan Toronto Glomerulonephritis registry, Canada (1975 - 2006), and compared their baseline characteristics. Slope of estimated glomerular filtration rate (eGFR) in each group was approximated using separate repeated measures regression models for each country.

RESULTS

There were 152 Canadian and 76 Thai patients. At the time of first presentation, Thai patients were more likely to be female (63.2 vs. 44.1%, p = 0.01), have less baseline proteinuria (1.2 vs. 1.7 g/d, p = 0.08) and more likely to receive angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin receptor blockers (ARB) (64.0 vs. 15.2%, p < 0.01), or prednisone (41.3 vs. 4.6%, p < 0.01). The annual change in estimated glomerular filtration rate (eGFR) for the Thai and Canadian groups were -0.82 ml/min/1.73 m2/year and -3.35 ml/min/1.73 m2/year, respectively, after adjustment for age, sex, mean arterial pressure (MAP), proteinuria, body mass index, Haas histological grade, chronicity scores and baseline medications.

CONCLUSIONS

Although disease severity was similar among IgA nephropathy patients in Canada and Thailand, more Thai patients were on ACE-I/ARB or prednisone therapy at baseline. Further prospective research is needed to explore international differences in demographic and environmental factors, health resources, and disease management to determine how they may impact long-term outcomes in Asians with IgA nephropathy.

Association of angiotensin II type 2 receptor gene A1818T polymorphism with progression of immunoglobulin A nephropathy in Korean patients

We determined the relationship between the progression of immunoglobulin A nephropathy (IgAN) and the A1818T polymorphism in intron 2 of Angiotensin II type 2 receptor (AT2R) gene, which might play protective roles in the pathogenesis of IgAN. Patients with biopsy-proven IgAN were recruited from the registry of the Progressive REnal disease and Medical Informatics and gEnomics Research (PREMIER) which was sponsored by the Korean Society of Nephrology. A1818T polymorphism of AT2R gene was analyzed with PCR-RFLP method and the association with the progression of IgAN, which was defined as over 50% increase in baseline serum creatinine level, was analyzed with survival analysis. Among the 480 patients followed for more than 10 months, the group without T allele had significantly higher rates of progression of IgAN than the group with T allele (11.4% vs. 3.9%, p=0.024), although there were no significant differences in the baseline variables such as initial serum creatinine level, the degree of proteinuria, and blood pressure. In the Cox's proportional hazard model, the hazard ratio of disease progression in the patients with T allele was 0.221 (95% confidence interval for Exp(B): 0.052-0.940, p=0.041) compared to that of without T allele. In conclusion, A1818T polymorphism of AT2R gene was associated with the progression of IgAN.