Mesangial cells stimulated by immunoglobin A1 from IgA nephropathy upregulates transforming growth factor-beta1 synthesis in podocytes via renin-angiotensin system activation

State-of-Art Therapeutics in IgA Nephropathy

Immunoglobulin-A nephropathy (IgAN) is the most common primary glomerulonephritis in the world, with up to 40% of patients progressing to end-stage kidney disease (ESKD) within 30 years of diagnosis. IgAN is characterized by elevated serum levels of galactose-deficient IgA1 (Gd-IgA1), which leads to immune complex formation and deposition in the glomerular mesangium, causing kidney injury. A diverse disease course and the long-term follow-up required for clinically relevant endpoints (e.g., ESKD) have been barriers to the development of novel therapies in IgAN. Disease management has focused on supportive care with inhibitors of the renin-angiotensin system and, more recently, sodium-glucose transporter inhibitors to control proteinuria. The recent acceptance of proteinuria as a surrogate endpoint by regulatory bodies and a better understanding of disease pathology have helped to initiate the development of several novel treatments. Subsequently, a targeted-release formulation of budesonide and a dual endothelin/angiotensin inhibitor (sparsentan) have received accelerated approval for patients with IgAN. However, additional therapies are needed to target the different pathogenic mechanisms and individualize patient care. Several compounds currently under investigation target various effectors of pathology. There are promising clinical results from emerging compounds that target the generation of Gd-IgA1 by B cells, including inhibitors of A PRoliferation-Inducing Ligand (APRIL) and dual inhibitors of APRIL and B-cell activating factor (BAFF). Other investigational therapies target the complement cascade by inhibiting proteins of the lectin or alternative pathways. As the therapeutic landscape evolves, it will be important to revise treatment guidelines and develop updated standards of care.

Role of abnormal glycosylated IgA1 and interstitial transformation of glomerular endothelial cells in the development and progression of IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is a common primary renal disease in childhood.

METHODS

Twenty blood samples and renal tissue from patients with IgAN, 20 blood samples from healthy children and 10 normal renal tissue were collected. Serum Gd-IgA1 and renal Gd-IgA1, CD31, α-SMA and vimentin were measured.

RESULTS

The serum Gd-IgA1 concentration in the IgAN group was significantly higher. Gd-IgA1 was not expressed in normal kidneys, which was positive in the IgAN group. Gd-IgA1 levels in serum and renal tissue were not related. The expression of CD31 decreased significantly in IgAN group, while the expression of α-SMA and vimentin increased significantly. There was no significant correlation between the renal concentration of Gd-IgA1 and CD31, α-SMA and vimentin.

CONCLUSION

The increased Gd-IgA1 in the serum and kidney may promote the pathogenesis of IgAN. The serum Gd-IgA1 cannot predict the extent of its deposition in the kidney. Endothelial mesenchymal transition (EndMT) may be involved in the pathogenesis of renal fibrosis in IgAN.

The Role of Immune Modulation in Pathogenesis of IgA Nephropathy

IgA nephropathy (IgAN) is the most prevalent primary glomerulonephritis worldwide, with diverse clinical manifestations characterized by recurrent gross hematuria or microscopic hematuria, and pathological changes featuring poorly O-galactosylated IgA1 deposition in the glomerular mesangium. Pathogenesis has always been the focus of IgAN studies. After 50 years of research, most scholars agree that IgAN is a group of clinicopathological syndromes with certain common immunopathological characteristics, and multiple mechanisms are involved in its pathogenesis, including immunology, genetics, and environmental or nutritional factors. However, the precise pathogenetic mechanisms have not been fully determined. One hypothesis about the pathogenesis of IgAN suggests that immunological factors are engaged in all aspects of IgAN development and play a critical role. A variety of immune cells (e.g., dendritic cells, NK cells, macrophages, T-lymphocyte subsets, and B-lymphocytes, etc.) and molecules (e.g., IgA receptors, Toll-like receptors, complements, etc.) in innate and adaptive immunity are involved in the pathogenesis of IgAN. Moreover, the abnormality of mucosal immune regulation is the core of IgAN immunopathogenesis. The roles of tonsil immunity or intestinal mucosal immunity, which have received more attention in recent years, are supported by mounting evidence. In this review, we will explore the latest research insights on the role of immune modulation in the pathogenesis of IgAN. With a better understanding of immunopathogenesis of IgAN, emerging therapies will soon become realized.

[Correlation between TGF-B gene promoter-509C/T polymorphism and IgA nephropathy in core families in Guangxi Zhuang Autonomous Region and the therapeutic effect of dendrobium]

OBJECTIVE

To investigate the correlation between transformation growth factor (TGF- B) polymorphisms and IgA nephropathy and the therapeutic effect of dendrobium on IgA nephropathy.

METHODS

Polymerase chain reaction- restriction fragment length polymorphism (PCR- RFLP) and direct sequencing were used for analysis of 118 patients with IgA nephropathy from core families in Guangxi Zhuang Autonomous Region. The imbalanced transfer of TGF iso1-509 C/T in the affected offsprings was observed by transfer imbalance test and HRR analysis. The TGF-B genotype of the patients and the core family members were detected. The therapeutic effects of Dendrobium candidum combined with hormone and ACEI/ARB treatments were evaluated by observing the patient's urine protein (24 hUpr), serum albumin (ALB), creatinine (Scr) and urea nitrogen (BUN) levels.

RESULTS

In the 118 patients with IgA nephropathy, we identified TGF-B 1 promoter -509C/T genotype CC in 32 (27.1%) cases, CT in 58 (49.2%) cases, and TT in 28 (23.7%) cases. In the core family of the patients, CC genotype was found in 33 (28.0%) cases, CT in 55 (46.6%) cases, and TT in 30 (28.0%) cases. The treatments significantly lowered 24 hUpr, Scr, and BUN levels (P > 0.05) in patients with CC genotype, significantly lowered 24 hUpr and BUN levels in patients with CT genotype (P < 0.05), and significantly lowered 24 hUpr and BUN level and increased (P < 0.05) ALB level (P < 0.01) in patients with TT genotype.

CONCLUSIONS

There is no significant correlation between TGF-B promoter - 509C/T polymorphism and IgA nephropathy. The patients with CC genotype are sensitive to the treatments with hormone and ACEI/ ARB and show a stronger response to combined treatments with dendrobium.

Clinicopathological features and prognosis of membranoproliferative-like Henoch-Schönlein purpura nephritis in children

BACKGROUND

The aim of this retrospective study was to define the clinical manifestations, pathological features and prognosis of children with membranoproliferative-like Henoch-Schönlein purpura nephritis (HSPN), representing International Study of Kidney Disease in Children (ISKDC) grade VI.

METHODS

Among 245 patients with HSPN treated in our hospital between 2008 and 2010, nine patients (3.7%) were diagnosed with HSPN of ISKDC grade VI (males = 5, females = 4, age: 9.5 ± 2.03 years, mean ± SD). The clinical features, laboratory and pathological findings, treatment and outcome of the 9 patients were retrospectively analyzed.

RESULTS

Of the 9 patients, 7 (78%) presented with hematuria and nephrotic syndrome, and were treated with steroids (oral prednisone or intravenous methylprednisolone pulse therapy) and immunosuppressants (oral tripterygium glycosides or intravenous cyclophosphamide pulse therapy). One (11%) patient had hematuria and nephrotic range proteinuria (> 50 mg/kg per 24 hours) and was treated with oral prednisone and tripterygium glycosides. Another (11%) patient presented with hematuria and moderate proteinuria (25-50 mg/kg per 24 hours) and was treated with oral tripterygium glycoside only. Histopathological examination showed diffuse glomerular mesangial and endocapillary proliferation, mesangial interposition, double-contour formation, podocyte hypertrophy, shedding, and cytoplasmic absorption droplets. The percentages of glomeruli with small cellular crescents varied from 4%-25% in 6 of 9 patients. Follow-up for 2 to 4 years showed excellent recovery in all patients.

CONCLUSIONS

The main clinical feature of ISKDC grade VI HSPN in children is a nephrotic syndrome with hematuria. The excellent prognosis of the disease was probably related to early diagnosis and treatment with steroids and/or immunosuppressants, and mild degree of glomerulosclerosis and tubulointerstitial damage.

Henoch-Schönlein purpura nephritis in children

Henoch-Schönlein purpura (HSP) is the most common vasculitis in children, in whom prognosis is mostly dependent upon the severity of renal involvement. Nephritis is observed in about 30% of children with HSP. Renal damage eventually leads to chronic kidney disease in up to 20% of children with HSP nephritis in tertiary care centres, but in less than 5% of unselected patients with HSP, by 20 years after diagnosis. HSP nephritis and IgA nephropathy are related diseases resulting from glomerular deposition of aberrantly glycosylated IgA1. Although both nephritides present with similar histological findings and IgA abnormalities, they display pathophysiological differences with important therapeutic implications. HSP nephritis is mainly characterized by acute episodes of glomerular inflammation with endocapillary and mesangial proliferation, fibrin deposits and epithelial crescents that can heal spontaneously or lead to chronic lesions. By contrast, IgA nephropathy normally presents with slowly progressive mesangial lesions resulting from continuous low-grade deposition of macromolecular IgA1. This Review highlights the variable evolution of similar clinical and histological presentations among paediatric patients with HSP nephritis, which constitutes a challenge for their management, and discusses the treatment of these patients in light of current guidelines based on clinical evidence from adults with IgA nephropathy.

N-acetylgalactosamine exposure of serum IgA1 was associated with glomerulosclerosis and tubular atrophy/interstitial fibrosis of IgA nephropathy patients

AIM

Immunoglobulin A nephropathy (IgAN) is the most common glomerulonephritis with various histological and clinical phenotypes. N-acetylgalactosamine (GalNAc) exposure plays a pivotal role in the pathogenesis of IgAN. The aim of the current study is to investigate whether GalNAc exposure of serum IgA1 was associated with clinical and pathological manifestation of IgAN.

METHODS

Sera from 199 patients with biopsy proved IgAN were collected. Clinical and pathological manifestations were collected. Biotinylated Helix aspersa were used in ELISA to examine GalNAc exposure on IgA1 molecules. Patients were divided into two groups according to the GalNAc exposure rate less or more than 0.4.

RESULTS

Age, gender, and serum creatinine were comparable between the two groups. Univariate analysis showed that significantly higher urinary protein excretion rate but less severe glomerular sclerosis and tubularinterstitial fibrosis were observed in the lower GalNAc exposure group. Multivariate regression analysis demonstrated that adjusted by age and gender, the GalNAc exposure rate more than 0.4 was a risk factor of glomerular sclerosis and tubularinterstitial fibrosis, OR*(95% CI) were 2.76 (1.19-6.37) and 2.49 (1.18-5.25), respectively.

CONCLUSION

Immunoglobulin A nephropathy patients with lower proteinuria had higher GalNAc exposure rates. The GalNAc exposure rate more than 0.4 was a risk factor of severe chronic renal tissue change.

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.

Henoch-Schonlein purpura nephritis: pathophysiology, treatment, and future strategy

Henoch-Schönlein purpura nephritis is a rare kidney disease leading to chronic kidney disease in a non-negligible percentage of patients. Although retrospective studies suggest beneficial effects of some therapies, prospective randomized clinical trials proving treatment efficacy are still lacking. The dilemma of spontaneous recovery even in patients with severe clinical and histologic presentation and of late evolution to chronic kidney disease in patients with mild initial symptoms renders it difficult for clinicians to expose patients to treatment protocols that are not evidence-based. A better understanding of the pathophysiology of progression to chronic kidney disease in Henoch-Schönlein purpura patients could be achieved by designing prospective international multicenter studies looking at determinants of clinical and histopathological evolution as well as possible circulating and urinary markers of progression. Such studies should be supported by a database available on the web and a new histologic classification of kidney lesions. This paper reports clinical, pathologic, and experimental data to be used for this strategy and to assist clinicians and clinical trial designers to reach therapeutic decisions.