Points of view in nephrology: personalized management of IgA nephropathy, beyond KDIGO

IgA nephropathy is the most common primary glomerulonephritis worldwide, and an important cause of kidney failure, as 20-40% of patients progress to renal replacement therapy 20-30 years after diagnosis. Its clinical presentation ranges from isolated microscopic hematuria to nephrotic syndrome, and even to a rapidly progressive course. Ethnicity and epigenetics play a key role in its clinical aggressiveness. Selection of patients at risk needing immunosuppressive treatment is a challenge for the nephrologist. Some active and chronic kidney lesions detected on kidney biopsy have been demonstrated to have prognostic value according to the Oxford Classification of IgA nephropathy, later validated by numerous studies. However, KDIGO 2021 guidelines still consider persistent proteinuria > 1 g/24 h to be the most relevant risk factor for the progression of IgA nephropathy and the only one requiring immunosuppressive treatment. KDIGO guidelines have proposed a therapeutic algorithm, but many patients present peculiar characteristics that are not addressed by the current guidelines, pointing to the need for alternative approaches. In these cases, a tailored approach to each patient should be followed in which clinical, histological, laboratory, social and ethical aspects must be considered. In this manuscript we present three cases of IgA nephropathy from different countries, highlighting many of the aspects encountered in clinical practice that illustrate an individualized approach to the treatment of these patients.

IgA nephropathy in children with minimal proteinuria: to biopsy or not to biopsy?

BACKGROUND

Tubulointerstitial lesions and glomerular inflammation severity have been shown to correlate with proteinuria in children with IgA nephropathy (cIgAN). However, there is a lack of data regarding severity of histopathologic findings in cIgAN in patients with minimal to absent proteinuria since kidney biopsy indications are not well defined in these cases.

METHODS

Twenty-eight cIgAN patients with kidney biopsy from 4 different centers in Paris (France) and Montreal (Canada) with a urine protein/creatinine ratio (UPCr) ≤ 0.03 g/mmol and a normal estimated glomerular filtration rate (eGFR > 90 ml/min/1.73 m2) on the day of kidney biopsy prior to treatment were included.

RESULTS

Median age was 11.82 (9.32-13.45) years, and median follow-up was 4 years (2.87-6.53). At time of biopsy, median eGFR was 116 (102.3-139.7) ml/min/1.73 m2, and median UPCr was 0.02 (0.011-0.03) g/mmol. Microscopic or macroscopic hematuria was present in 35.7% and 64.3% of cases, respectively. Kidney biopsy microscopy analysis showed mesangial (M1), endocapillary (E1), or extracapillary (C1) hypercellularity in 53.5%, 32.1%, and 7.1% of patients, respectively. Chronic histological lesions were also present: glomerulosclerosis (S1) in 42.8% and tubular atrophy/interstitial fibrosis in 7.1%. Podocytopathic features were detected in 21.4%. An ACE inhibitor or immunosuppressive therapy (IS) was prescribed in 42.8% and 21.4% of these patients respectively. One-third (35.7%) received no treatment. At last follow-up, median eGFR was 111.9 (90.47-136.1) ml/min/1.73 m2, and median UPCr was 0.028 (0.01-0.03) g/mmol.

CONCLUSION

cIgAN with minimal proteinuria at time of biopsy might be linked with acute and chronic glomerular lesions.

Advances in the treatment of IgA nephropathy with biological agents

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerular disease, and the "four-hit" theory represents its currently accepted pathogenic mechanism. Mucosal immunity triggered by infections in the respiratory tract, intestines, or other areas leads to antigen presentation, T cell stimulation, B cell maturation, and the production of IgA-producing plasma cells. The proteins B-lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) are involved in this process, and alternative complement and lectin pathway activation are also part of the pathogenic mechanism. Kidney Disease Improving Global Outcomes guidelines indicate that a specific effective treatment for IgAN is lacking, with renin-angiotensin-aldosterone system inhibitors being the primary therapy. Recent research shows that biological agents can significantly reduce proteinuria, stabilize the estimated glomerular filtration rate, and reverse some pathological changes, such as endocapillary proliferation and crescent formation. There are four main categories of biological agents used to treat IgA nephropathy, specifically anti-CD20 monoclonal antibodies, anti-BLyS or APRIL monoclonal antibodies, monoclonal antibodies targeting both BLyS and APRIL (telitacicept and atacicept), and monoclonal antibodies inhibiting complement system activation (narsoplimab and eculizumab). However, further research on the dosages, treatment duration, long-term efficacy, and safety of these biological agents is required.

Podocyte-specific proteins in urinary extracellular vesicles of patients with IgA nephropathy: Vasorin and ceruloplasmin

Introduction

Urinary extracellular vesicles (uEVs) can be considered biomarkers of kidney diseases. EVs derived from podocytes may reflect podocyte damage in different glomerular diseases. IgA nephropathy (IgAN) is one of the most common forms of glomerulonephritis (GN) characterized by proteinuria and hematuria. This study aimed to analyze the uEVs of IgAN patients to understand the pathophysiological processes of the disease at the protein level.

Methods

Patients with GN [biopsy-proven IgAN (n = 16) and membranous glomerulonephritis (MGN, n = 16)], and healthy controls (n = 16) were included in this study. The uEVs were extracted, characterized, and analyzed to evaluate the protein levels of candidate markers of IgAN, including vasorin precursor, aminopeptidase N, and ceruloplasmin by western-blot analysis.

Results

Higher levels of both podocytes and EVs-related proteins were observed in the pooled urine samples of GN patients compared to the healthy controls. In IgAN patients, uEV-protein levels of vasorin were statistically lower while levels of ceruloplasmin were significantly higher compared to MGN (P = 0.002, P = 0.06) and healthy controls, respectively (P = 0.020, P= 0.001).

Conclusion

Different levels of the studied proteins in uEVs may indicate podocyte injury and represent a direct association with the pathology of IgAN and MGN.

Comparative proteomic analysis of glomerular proteins in IgA nephropathy and IgA vasculitis with nephritis

BACKGROUND

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN) are related glomerular diseases characterized by marked similarities in immunological and histological findings. We herein performed a comparative proteomic analysis of glomerular proteins in IgAN and IgAVN.

METHODS

We used renal biopsy specimens from 6 IgAN patients without nephrotic syndrome (NS) (IgAN-I subgroup), 6 IgAN patients with NS (IgAN-II subgroup), 6 IgAVN patients with 0-8.0% of glomeruli with crescent formation (IgAVN-I subgroup), 6 IgAVN patients with 21.2-44.8% of glomeruli with crescent formation (IgAVN-II subgroup), 9 IgAVN patients without NS (IgAVN-III subgroup), 3 IgAVN patients with NS (IgAN-IV subgroup), and 5 control cases. Proteins were extracted from laser microdissected glomeruli and analyzed using mass spectrometry. The relative abundance of proteins was compared between groups. An immunohistochemical validation study was also performed.

RESULTS

More than 850 proteins with high confidence were identified. A principal component analysis revealed a clear separation between IgAN and IgAVN patients and control cases. In further analyses, 546 proteins that were matched with ≥ 2 peptides were selected. The levels of immunoglobulins (IgA, IgG, and IgM), complements (C3, C4A, C5, and C9), complement factor H-related proteins (CFHR) 1 and 5, vitronectin, fibrinogen chains, and transforming growth factor-β inducible gene-h3 were higher (> 2.6 fold) in the IgAN and IgAVN subgroups than in the control group, whereas hornerin levels were lower (< 0.3 fold). Furthermore, C9 and CFHR1 levels were significantly higher in the IgAN group than in the IgAVN group. The abundance of some podocyte-associated proteins and glomerular basement membrane (GBM) proteins was significantly less in the IgAN-II subgroup than in the IgAN-I subgroup as well as in the IgAVN-IV subgroup than in the IgAVN-III subgroup. Among the IgAN and IgAVN subgroups, talin 1 was not detected in the IgAN-II subgroup. This result was supported by immunohistochemical findings.

CONCLUSIONS

The present results suggest shared molecular mechanisms for glomerular injury in IgAN and IgAVN, except for enhanced glomerular complement activation in IgAN. Differences in the protein abundance of podocyte-associated and GBM proteins between IgAN and IgAVN patients with and without NS may be associated with the severity of proteinuria.

DNA-damaged podocyte-CD8 T cell crosstalk exacerbates kidney injury by altering DNA methylation

Recent epigenome-wide studies suggest an association between blood DNA methylation and kidney function. However, the pathological importance remains unclear. Here, we show that the homing endonuclease I-PpoI-induced DNA double-strand breaks in kidney glomerular podocytes cause proteinuria, glomerulosclerosis, and tubulointerstitial fibrosis with DNA methylation changes in blood cells as well as in podocytes. Single-cell RNA-sequencing analysis reveals an increase in cytotoxic CD8+ T cells with the activating/costimulatory receptor NKG2D in the kidneys, which exhibit a memory precursor effector cell phenotype, and the CD44high memory CD8+ T cells are also increased in the peripheral circulation. NKG2D blockade attenuates the renal phenotype caused by podocyte DNA damage. Blood methylome shows increased DNA methylation in binding sites for STAT1, a transcription factor contributing to CD8+ T cell homeostasis. Collectively, podocyte DNA damage alters the blood methylome, leading to changes in CD8+ T cells, which contribute to sustained renal injury in chronic kidney disease.

Association between glomerular C4d deposition, proteinuria, and disease severity in children with IgA nephropathy

BACKGROUND

C4d may be used as a marker to evaluate the condition and prognosis of adults with IgA nephropathy, but there have been few studies of children with IgA nephropathy.

METHODS

C4d immunohistochemical staining was performed on samples from children with IgA nephropathy with C1q-negative immunofluorescence. The clinical and pathological treatment and prognostic characteristics of children in the C4d-positive and -negative groups were compared.

RESULTS

A total of sixty-five children with IgA nephropathy were included in the study and were followed up for an average of 37 months. C4d was mainly deposited along the capillary loops. The urinary protein-to-creatinine ratio (UPCR) in the C4d-positive group was significantly higher than that in the C4d-negative group (3.97 vs. 0.81, P < 0.001), and the average integrated optical density value of each child was positively correlated with the UPCR (r = 0.441, P < 0.001). There was a significant difference in the proportions of children with mesangial hypercellularity (M1) (68.97% vs. 44.44%, P = 0.048) and segmental glomerulosclerosis (S1) (65.52% vs. 33.33%, P = 0.010) between the C4d-positive group and the C4d-negative group. The proportion of children who received immunosuppressants in the C4d-positive group was higher than that in the C4d-negative group (86.21% vs. 36.11%, P < 0.001). There was no significant difference in the proportion of children developing kidney failure between the two groups.

CONCLUSION

C4d was found to be associated with proteinuria, segmental lesions, and immunosuppressant treatment. Activation of the lectin pathway may reflect the severity of clinical and pathological manifestations of IgA nephropathy in children. A higher resolution version of the Graphical abstract is available as Supplementary information.

Renal function in aged C57BL/6J mice is impaired by deposition of age-related apolipoprotein A-II amyloid independent of kidney aging

Spontaneous and age-related amyloidosis has been reported in C57BL/6J mice; however, the biochemical characteristics of age-related amyloidosis remain unclear. Therefore, we herein investigated the age-related prevalence of amyloidosis, the types of amyloid fibril proteins, and the effects of amyloid deposition on renal function in C57BL/6J mice. The results obtained revealed a high incidence of amyloidosis in C57BL/6J mice originating from the Jackson laboratory as well as the deposition of large amounts of amyloid in the glomeruli of aged mice. We identified the amyloid fibril protein in C57BL/6J mice as wild-type apolipoprotein A-II. We induced renal amyloid deposition in 40-week-old mice, equivalent to that of spontaneous development in 80-week-old mice, to rule out the effects of aging, and revealed subsequent damage to kidney function by amyloid deposits. Furthermore, amyloid deposition in the mesangial region decreased podocyte density, compromised foot processes, and led to the accumulation of fibroblast growth factor 2 (FGF2) in glomeruli. Collectively, these results suggest that AApoAII deposition is a general pathology in aged C57BL/6J mice and is dependent on supplier colonies. Therefore, the effects of age-related amyloid deposition need to be considered in research on aging in mice.

Podocytopathy Associated with IgA Nephropathy in Pregnancy: A Challenging Association

IgA nephropathy is the most common form of primary glomerulonephritis. While associations of IgA and other glomerular diseases have been described, the association of IgA nephropathy with "primary" podocytopathy is rare and has not been reported in pregnancy, due in part to the infrequent use of kidney biopsy during pregnancy, and a frequent overlap with preeclampsia. We report the case of a 33-year-old woman with normal kidney function, referred in the 14th gestational week of her second pregnancy, due to nephrotic proteinuria and macroscopic hematuria. The baby's growth was normal. The patient reported episodes of macrohematuria one year previously. A kidney biopsy performed at 18 gestational weeks confirmed IgA nephropathy, associated with extensive podocyte damage. Treatment with steroids and tacrolimus led to remission of proteinuria and a healthy baby, adequate for gestational age, was delivered at 34 gestational weeks and 6 days (premature rupture of membranes). Six months after delivery, proteinuria was about 500 mg per day, with normal blood pressure and kidney function. This case highlights the importance of timely diagnosis in pregnancy and underlines that good maternal and fetal outcomes can be achieved with appropriate treatment, even in complex or severe cases.

Molecular insight in intrarenal inflammation affecting four main types of cells in nephrons in IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis and the leading cause of kidney failure in the world. The current widely accepted framework for its pathogenesis is the "multi-hit hypothesis." In this review, we mainly discussed the intrarenal inflammation in IgAN, which is initiated by immune complex deposition with complement molecule activation, by focusing on four main types of cells in nephrons including mesangial cells, endothelial cells, podocytes, and tubular epithelial cells (TECs). Galactose-deficient IgA1 (Gd-IgA1)-containing immune complexes deposit in the mesangium and activate complement molecules and mesangial cells. Activation of mesangial cells by Gd-IgA1 deposition with enhanced cellular proliferation, extracellular matrix (ECM) expansion, and inflammatory response plays a central role in the pathogenesis of IgAN. Regional immune complex deposition and mesangial-endothelial crosstalk result in hyperpermeability of endothelium with loss of endothelial cells and infiltration barrier proteins, and recruitment of inflammatory cells. Podocyte damage is mainly derived from mesangial-podocyte crosstalk, in which tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), renin-angiotensin-aldosterone system (RAAS), and micro-RNAs are the major players in podocyte apoptosis and disorganization of slit diaphragm (SD) related to proteinuria in patients with IgAN. In addition to filtrated proteins into tubulointerstitium and mesangial-tubular crosstalk involved in the injury of TECs, retinoic acid has been discovered innovatively participating in TEC injury.

B7-1 mediates podocyte injury and glomerulosclerosis through communication with Hsp90ab1-LRP5-β-catenin pathway

Podocyte injury is a hallmark of glomerular diseases; however, the underlying mechanisms remain unclear. B7-1 is increased in injured podocytes, but its intrinsic role is controversial. The clinical data here revealed the intimate correlation of urinary B7-1 with severity of glomerular injury. Through transcriptomic and biological assays in B7-1 transgenic and adriamycin nephropathy models, we identified B7-1 is a key mediator in podocyte injury and glomerulosclerosis through a series of signal transmission to β-catenin. Using LC-MS/MS, Hsp90ab1, a conserved molecular chaperone, was distinguished to be an anchor for transmitting signals from B7-1 to β-catenin. Molecular docking and subsequent mutant analysis further identified the residue K69 in the N terminal domain of Hsp90ab1 was the key binding site for B7-1 to activate LRP5/β-catenin pathway. The interaction and biological functions of B7-1-Hsp90ab1-LRP5 complex were further demonstrated in vitro and in vivo. We also found B7-1 is a novel downstream target of β-catenin. Our results indicate an intercrossed network of B7-1, which collectively induces podocyte injury and glomerulosclerosis. Our study provides an important clue to improve the therapeutic strategies to target B7-1.

Mesangial Cell–Derived Exosomal miR-4455 Induces Podocyte Injury in IgA Nephropathy by Targeting ULK2

Growing evidence suggests that mesangial cells (MCs) play a crucial role in the pathogenesis of IgA nephropathy (IgAN) by secreting aIgA1. However, the mechanism by which MCs regulate podocyte injury remains unknown. This study demonstrated that MC-derived exosomes treated with aIgA1 induced podocyte injury in IgA nephropathy. miR-4455, which was significantly upregulated in aIgA1 treatment MC-derived exosomes, can be transferred from MCs to podocytes via exosomes. MC-derived exosomal miR-4455 induced podocyte injury. Mechanistically, exosomal miR-4455 directly targeted ULK2 to regulate LC3II/I and P62 levels, which mediates autophagy homeostasis. This study revealed that MC-derived exosomal miR-4455 is a key factor affecting podocyte injury and provides a series of potential therapeutic targets for treating IgA nephropathy.

Tissue Factor, Thrombosis, and Chronic Kidney Disease

Coagulation abnormalities are common in chronic kidney disease (CKD). Tissue factor (TF, factor III) is a master regulator of the extrinsic coagulation system, activating downstream coagulation proteases, such as factor Xa and thrombin, and promoting fibrin formation. TF and coagulation proteases also activate protease-activated receptors (PARs) and are implicated in various organ injuries. Recent studies have shown the mechanisms by which thrombotic tendency is increased under CKD-specific conditions. Uremic toxins, such as indoxyl sulfate and kynurenine, are accumulated in CKD and activate TF and coagulation; in addition, the TF-coagulation protease-PAR pathway enhances inflammation and fibrosis, thereby exacerbating renal injury. Herein, we review the recent research studies to understand the role of TF in increasing the thrombotic risk and CKD progression.

Sirtuins as novel pharmacological targets in podocyte injury and related glomerular diseases

Podocyte injury is a major cause of proteinuria in kidney diseases, and persistent loss of podocytes leads to rapid irreversible progression of kidney disease. Sirtuins, a class of nicotinamide adenine dinucleotide-dependent deacetylases, can promote DNA repair, modify transcription factors, and regulate the cell cycle. Additionally, sirtuins play a critical role in renoprotection, particularly against podocyte injury. They also have pleiotropic protective effects on podocyte injury-related glomerular diseases, such as improving the immune inflammatory status and oxidative stress levels, maintaining mitochondrial homeostasis, enhancing autophagy, and regulating lipid metabolism. Sirtuins deficiency causes podocyte injury in different glomerular diseases. Studies using podocyte sirtuin-specific knockout and transgenic models corroborate this conclusion. Of note, sirtuin activators have protective effects in different podocyte injury-related glomerular diseases, including diabetic kidney disease, focal segmental glomerulosclerosis, membranous nephropathy, IgA nephropathy, and lupus nephritis. These findings suggest that sirtuins are promising therapeutic targets for preventing podocyte injury. This review provides an overview of recent advances in the role of sirtuins in kidney diseases, especially their role in podocyte injury, and summarizes the possible rationale for sirtuins as targets for pharmacological intervention in podocyte injury-related glomerular diseases.

Liuwei Dihuang Pills Inhibit Podocyte Injury and Alleviate IgA Nephropathy by Directly Altering Mesangial Cell-Derived Exosome Function and Secretion

Background: Immunoglobulin A nephropathy (IgAN) is the most common glomerular disease worldwide. Its pathological features include IgA immune complex deposition, accompanied by mesangial cell proliferation and mesangial matrix expansion. This study was conducted to investigate the effects of Liuwei Dihuang pills (LWDHW) on IgAN in mice and human podocytes, as well as to determine their underlying mechanisms of action.

Methods: For in vitro experiments, podocytes were exposed to the human mesangial cell culture medium supernatant of glomerular cells treated with aggregated IgA1 (aIgA1) and LWDHW-containing serum. Cell viability and the proportion of positive cells were evaluated using CCK-8 and flow apoptosis kits, respectively. The cells were collected for western blot analysis. Twenty-four mice with IgAN induced by oral bovine serum albumin administration combined with tail vein injection of staphylococcal enterotoxin B were randomly divided into four groups of six mice each: untreated model group, model + LWDHW group, model + rapamycin group, and model + LWDHW + rapamycin group. The normal control group contained six mice. The red blood cell count in the urine, urine protein, blood urea nitrogen, serum creatinine, and IgA deposition were determined, and TUNEL and western blotting were performed in the mouse kidney tissues.

Results:In vitro experiments showed that LWDHW promoted autophagy by regulating the PI3K/Akt/mTOR signalling pathway and improved the damage to podocytes caused by the aIgA1-treated mesangial cell supernatant. This study demonstrates the effectiveness of LWDHW for treating IgAN. In the animal experiments, LWDHW significantly reduced the urine red blood cell count, serum creatinine and urea nitrogen contents, and 24 h urinary protein function and improved IgA deposition in the kidney tissues, glomerular volume, glomerular cell proliferation and polysaccharide deposition, and glomerular cell apoptosis. The pills also reversed the changes in the LC3II/I ratio and p62 content in the kidney tissues. The combination of LWDHW and rapamycin showed stronger inhibitory effects compared to those of LWDHW or rapamycin alone.

Conclusion: LWDHW may improve regulation of the PI3K-Akt-mTOR pathway and inhibit autophagy in podocytes, as well as alleviate IgA nephropathy by directly altering mesangial cell exosomes.

Modulation of IL-6 Expression by KLF4-Mediated Transactivation and PCAF-Mediated Acetylation in Sublytic C5b-9-Induced Rat Glomerular Mesangial Cells

Interleukin-6 (IL-6) overproduction has been considered to contribute to inflammatory damage of glomerular mesangial cells (GMCs) in human mesangial proliferative glomerulonephritis (MsPGN) and its rat model called Thy-1 nephritis (Thy-1N). However, the regulatory mechanisms of IL-6 expression in GMCs upon sublytic C5b-9 timulation remain poorly understood. We found that Krüppel-like factor 4 (KLF4) bound to the IL-6 promoter (−618 to −126 nt) and activated IL-6 gene transcription. Furthermore, lysine residue 224 of KLF4 was acetylated by p300/CBP-associated factor (PCAF), which was important for KLF4-mediated transactivation. Moreover, lysine residue 5 on histone H2B and lysine residue 9 on histone H3 at the IL-6 promoter were also acetylated by PCAF, which resulted in an increase in IL-6 transcription. Besides, NF-κB activation promoted IL-6 expression by elevating the expression of PCAF. Overall, these findings suggest that sublytic C5b-9-induced the expression of IL-6 involves KLF4-mediated transactivation, PCAF-mediated acetylation of KLF4 and histones, and NF-κB activation in GMCs.

Immunological drivers of IgA nephropathy: Exploring the mucosa-kidney link

IgA nephropathy (IgAN) is the most common pattern of primary glomerular disease reported worldwide. Up to 40% of those with IgAN progress to end-stage kidney disease within 20 years of diagnosis, with no currently available disease-specific treatment. This is likely to change rapidly, with evolving insights into the mechanisms driving this disease. IgAN is an immune-complex-mediated disease, and its pathophysiology has been framed by the 'four-hit hypothesis', which necessitates four events to occur for clinically significant disease to develop. However, this hypothesis does not explain the wide variability observed in its presentation or clinical progression. Recently, there has been great interest in exploring the role of the mucosal immune system in IgAN, especially given the well-established link between mucosal infections and disease flares. Knowledge of antigen-mucosal interactions is now being successfully leveraged for therapeutic purposes; the gut-directed drug Nefecon (targeted release formulation-budesonide) is on track to become the first medication to be approved specifically for the treatment of IgAN. In this review, we examine established immunological paradigms in IgAN, explore how antigen-mucosal immune responses drive disease, and discuss how this knowledge is being used to develop new treatments.

Nephroprotective effect of naringin in methotrexate induced renal toxicity in male rats

The current work aims to study the nephroprotective potential of naringin (NG), a flavanone derived from citrus fruits, in methotrexate (MTX)-induced renal toxicity. Thirty male rats were divided into five groups; control group (IP saline), MTX group (IP single dose, 20 mg/kg), and three groups co-treated with MTX and naringin (IP daily dose; 20, 40, and 80 mg/kg, respectively). Kidney tissues were used to investigate renal function, oxidative stress, lipid peroxidation, and caspase-3 activity. Biochemical cytokine analysis was performed in addition to ultrastructural examinations of kidney tissue. When compared to the MTX-treated rats, MTX+NG significantly reduced the levels of urea, creatinine, MDA, NO, TNFα, IL-6, and caspase-3 activity. A significant increase in the levels of the antioxidant enzymes and GSH were also noted. Additionally, naringin ameliorated the apparent ultrastructural changes observed in the glomeruli and renal tubules of MTX-intoxicated rats. Noticeable structural improvements of glomerular lesions, proximal, and distal convoluted tubular epithelium were observed in MTX+NG treated animals, including podocytes with regular foot processes, perfectly organized filtration barrier, no signs of GBM thickening, organized brush border, and normal architecture of microvilli. Naringin (80 mg/kg) had the maximum amelioration effect. To the best of our knowledge, this is the first study to investigate the ultrastructural manifestations of naringin and/or MTX on the kidney of rats. Taken all, naringin has a potent therapeutic effect and can be used in adjuvant therapy to prevent MTX-induced nephrotoxicity. Nevertheless, the molecular mechanism underlying the nephroprotective capacity of naringin needs further investigation.

Podocyte-derived microparticles in IgA nephropathy

Microparticles are a general term for different types of cell plasma membrane-originated vesicles that are released into the extracellular environment. The paracrine action of these nano-sized vesicles is crucial for intercellular communications through the transfer of diverse lipids, cytosolic proteins, RNA as well as microRNAs. The progression of different diseases influences the composition, occurrence, and functions of these cell-derived particles. Podocyte injury has been shown to have an important role in the pathophysiology of many glomerular diseases including IgA nephropathy (IgAN). This review would focus on the possible potential of podocyte-derived microparticles detected in urine to be used as a diagnostic tool in IgAN.

New therapeutic perspectives for IgA nephropathy in children

Childhood IgA nephropathy (cIgAN) differs from the adult by having an abrupt clinical onset, often presenting as an acute attack that can progress to a chronic phase. No treatment guidelines have been established for the treatment of cIgAN. Given the severity of acute attack in children, and the number of life-years at stake, pediatricians prescribe immunosuppression in addition to renin-angiotensin system blockade. Non-specific immunosuppressors, such as corticosteroids, have systemic toxic effects, and given recent therapeutic advances in adult glomerulonephritis, new tailored strategies should be expected for children. The mucosal immune system has been highlighted as a key player in IgAN pathogenesis, and several biomarkers have been identified with a direct role in pathogenesis. In this review, we discuss current studies of conventional and novel therapeutic approaches for cIgAN.

Glomerular filtrate affects the dynamics of podocyte detachment in a model of diffuse toxic podocytopathy

Podocyte injury and subsequent detachment are hallmarks of progressive glomerulosclerosis. In addition to cell injury, unknown mechanical forces on the injured podocyte may promote detachment. To identify the nature of these mechanical forces, we studied the dynamics of podocyte detachment using sequential ultrastructural geometry analysis by transmission electron microscopy in NEP25, a mouse model of podocytopathy induced by anti-Tac(Fv)-PE38 (LMB2), a fusion protein attached to Pseudomonas exotoxin A, targeting CD25 on podocytes. After LMB2 injection, foot process effacement occurred on day three but detachment commenced on day eight and extended to day ten, reaching toward the urinary pole in clusters. Podocyte detachment was associated with foot process effacement covering over 60% of the glomerular basement membrane length. However, approximately 25% of glomeruli with diffuse (over 80%) foot process effacement showed no detachment. Blocking glomerular filtration via unilateral ureteral obstruction resulted in diffuse foot process effacement but no pseudocysts or detachment, whereas uninephrectomy increased pseudocysts and accelerated detachment, indicating that glomerular filtrate drives podocyte detachment via pseudocyst formation as a forerunner. Additionally, more detachment was observed in juxtamedullary glomeruli than in superficial glomeruli. Thus, glomerular filtrate drives the dynamics of podocyte detachment in this model of podocytopathy. Hence, foot process effacement may be a prerequisite allowing filtrate to generate local mechanical forces that expand the subpodocyte space forming pseudocysts, promote podocyte detachment and subsequent segmental sclerosis.

The Role of Glomerular Epithelial Injury in Kidney Function Decline in Patients With Diabetic Kidney Disease in the TRIDENT Cohort

Introduction

Although diabetic kidney disease (DKD) is responsible for more than half of all chronic and end-stage kidney disease (ESKD), the association of light (LM) and electron microscopic (EM) structural changes with clinical parameters and prognosis in DKD is incompletely understood.

Methods

This is an interim analysis of 62 patients diagnosed with biopsy-confirmed DKD from the multicenter TRIDENT (Transformative Research in Diabetic Nephropathy) study. Twelve LM and 8 EM descriptors, representing changes in glomeruli, tubulointerstitium, and vasculature were analyzed for their relationship with clinical measures of renal function. Patients were followed every 6 months.

Results

Multivariable linear regression analysis revealed that estimated glomerular filtration rate (eGFR) upon enrollment correlated the best with interstitial fibrosis. On the other hand, the rate of kidney function decline (eGFR slope) correlated the most with glomerular lesions including global glomerulosclerosis and mesangiolysis. Unbiased clustering analysis based on histopathologic data identified 3 subgroups. The first cluster, encompassing subjects with the mildest histologic lesions, had the most preserved kidney function. The second and third clusters had similar degrees of kidney dysfunction and structural damage, but differed in the degree of glomerular epithelial cell and podocyte injury (podocytopathy DKD subtype). Cox proportional hazard analysis showed that subjects in cluster 2 had the highest risk to reach ESKD (hazard ratio: 17.89; 95% confidence interval: 2.13–149.79). Glomerular epithelial hyperplasia and interstitial fibrosis were significant predictors of ESKD in the multivariate model.

Conclusion

The study highlights the association between fibrosis and kidney function and identifies the role of glomerular epithelial changes and kidney function decline.

Effect of probiotics on oxidative stress and inflammatory status in diabetic nephropathy: A systematic review and meta-analysis of clinical trials

This systematic review and meta-analysis was performed to evaluate the effect of probiotics on serum high sensitivity-C reactive protein (hs-CRP) and oxidative stress biomarkers among patients with Diabetic Nephropathy (DN). Electronic databases were searched through May 10, 2020. Seven trials that included 340 patients were identified for analysis. Meta-analysis indicated that probiotics significantly reduced hs-CRP (WMD = -1.53 mg/L; 95% CI = -2.38, -0.69; P < 0.001) and Malondialdehyde (MDA) (WMD = -0.62 ɥmol/L; 95% CI = -1.18, -0.06; P = 0.030) levels in DN patients, whereas they increased Glutathione (GSH) (WMD = 73.84 ɥmol/L; 95% CI = 24.3, 123.29; P = 0.003) and Total Antioxidant Capacity (TAC) (WMD = 26.54 mmol/L; 95% CI = 6.23, 46.85; P = 0.010). Therefore, probiotics may improve hs-CRP and oxidative stress biomarkers in DN population.

Visualized podocyte-targeting and focused ultrasound responsive glucocorticoid nano-delivery system against immune-associated nephropathy without glucocorticoid side effect

Glucocorticoids are widely used in the treatment of nephritis, however, its dose-dependent side effects, such as the increased risk of infection and metabolic disturbances, hamper its clinical use. This study reports a visualized podocyte-targeting and focused ultrasound responsive glucocorticoid nano-delivery system (named as Dex/PFP@LIPs-BMS-α), which specific delivers dexamethasone (Dex) to podocyte targets and reduces systemic side effects.

Methods: The glucocorticoid nano-delivery system was synthesized by a lipid thin film and a simple facile acoustic-emulsification method. This glucocorticoid nano-delivery system used BMS-470539 (BMS-α), a synthetic compound, as a “navigator” to specifically identify and target the melanocortin-1 receptor (MC-1R) on podocytes. The loaded perfluoropentane (PFP) realizes the directed "explosion effect" through ultrasound-targeted microbubble destruction (UTMD) technology under the coordination of low intensity focused ultrasound (LIFU) to completely release Dex.

Results: Both in vitro and in vivo experiments have demonstrated that Dex/PFP@LIPs-BMs-α accurately gathered to podocyte targets and improved podocyte morphology. Moreover, in vivo, proteinuria and serum creatinine levels were significantly reduced in the group treated with Dex/PFP@LIPs-BMS-α, and no severe side effects were detected. Furthermore, Dex/PFP@LIPs-BMS-α, with capabilities of ultrasound, photoacoustic and fluorescence imaging, provided individualized visual guidance and the monitoring of treatment.

Conclusion: This study provides a promising strategy of Dex/PFP@LIPs-BMS-α as effective and safe against immune-associated nephropathy.

The implications of focal segmental glomerulosclerosis in children with IgA nephropathy

Focal segmental glomerular sclerotic lesions in IgA nephropathy (IgAN), considered for years a chronic histologic feature related to proteinuria in remnant nephrons without any active role in the pathogenesis and progression of glomerular damage of IgAN, have been recently reconsidered. The Oxford classification of IgAN reported it as the "S" score and found it to be an independent risk factor for progression of IgAN. Its prognostic value was confirmed also in children. The identification of some histologic subvariants of the S lesion has produced interesting insights into different pathogenetic mechanisms of glomerular damage in IgAN. Tip lesion and podocyte hypertrophy are considered secondary to active podocytopathy and are correlated with higher levels of proteinuria and a faster decline in glomerular filtration rate. Moreover, endocapillary and mesangial hypercellularity might contribute in children with IgAN to formation and progression of S lesions. Considering the pathophysiology of these processes, children with some S features may benefit not only from nephroprotective measures but also from immunosuppression.

Clinical and histological differences between adults and children in new onset IgA nephropathy

BACKGROUND

Previous reports suggest initial presentation of IgA nephropathy (IgAN) in children is different from adults. No systematic comparison of clinical, biological, and histological childhood- and adult-onset IgAN is currently available.

METHODS

We compared pediatric and adult clinical and histological characteristics at IgAN diagnosis. Data on 211 consecutive patients from two different centers in Paris (82 children, 129 adults) were reviewed. Kidney biopsies were scored for Oxford classification and podocytopathic (P1) features.

RESULTS

We report higher eGFR at diagnosis in children compared to adults (89.5 vs. 64 ml/min/1.73 m²; p = 0.0001) but no difference in proteinuria. Histological analysis of kidney biopsy found higher proportions of mesangial (M1) and endocapillary (E1) hypercellularity in children compared with adults (M1 [80.7% vs. 27.9%, p = 0.0001]; E1 [71.3% vs. 30%, p = 0.0001]). Focal glomerulosclerosis (S1), tubular atrophy/interstitial fibrosis ≥ 25% (T1), and P1 were more frequent in adults (S1 [81.5% vs. 61.3%, p = 0.0012], T1 [49.5% vs. 1.35%, p = 0.0001], P1 [33.8% vs. 16.4%, p = 0.008). Proteinuria associated with M1, E1, and C1 in children (M1, p = 0.0001; E1, p = 0.0005; C1, p = 0.0014) but S1, P1, and T1 in adults (S1, p = 0.0001; P1, p = 0.0001; T1, p = 0.001). After steroid treatment (41 children and 28 adults), proteinuria decreased in children (p < 0.001, follow-up 38 months) and adults (p < 0.001, follow-up 76.9 months), whereas eGFR remained stable in adults but increased significantly in children (90.6 to 110 ml/min/1.73m²).

CONCLUSION

Proteinuria in children with IgAN is a marker of glomerular proliferative lesions whereas its presence in adults often reflects the presence of chronic lesions. This suggests the need for histological assessment.

A Personalized Update on IgA Nephropathy: A New Vision and New Future Challenges

IgA nephropathy (IgAN) is the most common primary glomerulonephritis in the world among patients undergoing renal biopsy. Approximately 30% of patients with IgAN develop end-stage kidney disease 20 years after renal biopsy. It is a glomerulopathy with a very broad clinical presentation, making it difficult to stratify and treat. IgAN is characterized by dysregulation of the immune system, which causes an abnormal synthesis of IgA1 that is deglycosylated causing its mesangial deposition. IgAN pathogenesis is incompletely understood; the current multi-hit hypothesis of IgAN pathogenesis does not explain the range of glomerular inflammation and renal injury associated with mesangial IgA deposition. Although associations between IgAN and glomerular and circulating markers of complement activation are established, the mechanism of complement activation and contribution to glomerular inflammation and injury are not defined. On the other hand, the renal-gut connection can also play an important role in the pathogenesis of IgAN with possible therapeutic implications. In order to standardize the histological findings, the Oxford Classification has allowed clarifying renal lesions that confer potential risk of progression. Currently, except for the blockade of the renin-angiotensin-aldosterone system, no other therapies are available in clinical setting for the treatment of IgAN, although the range of new drugs under investigation is extensive. The incorporation in the next trials of clinical parameters such as the amount of hematuria and histological lesions may allow more personalized therapeutic approaches. To summarize, in recent years, several important efforts have taken place in the understanding of IgAN, but still, further studies are warranted to elucidate the best therapeutic strategies according to the risk to improve the prognosis of this entity.

Evaluation of the Oxford classification in immunoglobulin A vasculitis with nephritis: a cohort study and meta-analysis

Background

Similarities in clinicopathological presentations in immunoglobulin A (IgA) nephropathy and IgA vasculitis with nephritis (IgAVN) raise the question of the utility of the Oxford classification in the latter. The aim of this study was to evaluate the Oxford classification in IgAVN.

Methods

We conducted a retrospective cohort study and meta-analysis following systematic searching of the MEDLINE and Excerpta Medica Database (EMBASE) databases between January 2009 and September 2019. We modeled the association of 30 and 50% decline in estimated glomerular filtration rate or end-stage renal disease with pathologic lesions of the Oxford classification including mesangial hypercellularity (M), endocapillary hypercellularity (E), segmental glomerulosclerosis (S), interstitial fibrosis/tubular atrophy (T) and crescents (C). Results were pooled using random-effects meta-analysis.

Results

The cohort study included 132 patients, and only T lesion was an independently risk factor in IgAVN. The meta-analysis yielded six retrospective studies with 721 patients and 139 endpoints. In multivariate model, T lesion was significantly associated with renal outcome (hazard ratio = 2.45, P = 0.007). M and C lesions could not predict renal outcome without evidence of heterogeneity. E and S lesions could not predict renal outcome with evidence of heterogeneity (I ² = 66.6%; P = 0.01, and I ² = 65.8%; P = 0.03, respectively). Subgroup analysis showed that the possible reasons to the heterogeneity were from usage of immunosuppressant, sample size and follow-up time.

Conclusions

The study suggests that the Oxford classification could not be fully validated in IgAVN. Higher portion of immunosuppressant especially before renal biopsy might be the main confounder for the predictive value of Oxford classification in IgAVN.

MicroRNA-27a-3p directly targets FosB to regulate cell proliferation, apoptosis, and inflammation responses in immunoglobulin a nephropathy

Immunoglobulin A nephropathy (IgAN) constitutes the most common primary glomerulonephritis worldwide; however, the exact pathogenesis of IgAN is unknown. Previous genome-wide analysis of microRNA (miRNA) expression in the kidney has confirmed that miRNAs are closely related to the pathological changes of IgAN. Accordingly, in this study we found that miR-27a-3p is upregulated in IgAN kidney tissues in addition to human podocytes and tubule epithelial HK2 but not mesangial cells. Methylthiazolyldiphenyl-tetrazolium bromide (MTT), flow cytometry, real-time polymerase chain reaction, western blot, and enzyme-linked immunosorbent assays were used to verify the regulatory effects of miR-27a-3p and its inhibition on cell proliferation, apoptosis, and release of inflammatory factors in podocytes and HK2 cells. The target genes of miR-27a-3p were predicted using bioinformatics software; the identity of FosB as a target gene of miR-27a-3p was confirmed by luciferase report assay and western blot. Overall, our findings demonstrated that miR-27a-3p regulates cell apoptosis, cell proliferation, and the release of inflammatory cytokines of human podocytes and HK2 cells by directly targeting FosB. Our results therefore suggested that miR-27a-3p might be associated with the pathophysiology of IgAN and may represent a potential target for further studies related to IgAN mechanism or therapeutics.

A case presentation of an IgA nephropathy patient with Vogt-Koyanagi-Harada syndrome

Background

Vogt-Koyanagi-Harada syndrome is a rare disease characterized by skin and eyelash bleaching, chronic granulomatous iridocyclitis and exudative retinal detachment, and aseptic meningitis and encephalopathy. IgA nephropathy complicated by Vogt-Koyanagi-Harada syndrome is very rare, even though they might have similar pathogeneses. Ocular lesions often are not examined when patients are diagnosed with IgA nephropathy, which affects the prognosis.

Case presentation

We describe a 55-year-old male IgA nephropathy patient who was admitted with high fever and hematuria. Physical examination revealed impaired binocular vision with blurred vision, impaired hearing, and a congestive rash on the chest and back. Renal ultrasound examination showed no abnormalities. Laboratory examination showed that glomerulonephritis was complicated by infection, and anti-infection therapy was ineffective. Bilateral fluorescein angiography showed Vogt-Koyanagi-Harada syndrome. Further renal biopsy confirmed IgA nephropathy. Hormone shock therapy and cyclophosphamide adjuvant therapy were administered, and the patient’s symptoms improved.

Conclusion

For the first time, we reported the case of simultaneous onset of IgA nephropathy and Vogt-Koyanagi-Harada syndrome, which is very rare. The onset of Vogt-Koyanagi-Harada syndrome is rapid and serious, while that of IgA nephropathy is relatively milder, making it easy for specialized doctors to neglect this condition. Doctors should be highly alert to the clinical concomitant occurrence of the two diseases with similar mechanisms, especially in the case of neurological defects and ocular symptoms in IgA nephropathy patients, since timely immunosuppressive treatment may improve the outcome of ocular diseases.

The correlation analysis between the Oxford classification of Chinese IgA nephropathy children and renal outcome - a retrospective cohort study

BACKGROUND

The 2016 Oxford Classification's MEST-C scoring system predicts outcomes in adults with IgA nephropathy (IgAN), but it lacks tremendous cohort validation in children with IgAN in China. We sought to verify whether the Oxford classification could be used to predict the renal outcome of children with IgAN.

METHODS

In this retrospective cohort study, 1243 Chinese IgAN children who underwent renal biopsy in Jinling Hospital were enregistered from 2000 to 2017. The combined endpoint was defined as either a ≥ 50% reduction in estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD). We probed into the relevance betwixt the Oxford classification and renal prognosis.

RESULTS

There were 29% of children with mesangial proliferation(M1), 35% with endocapillary proliferation (E1), 37% with segmental sclerosis/adhesion lesion (S1), 23% with moderate tubular atrophy/interstitial fibrosis (T1 25-50% of cortical area involved), 4.3% with severe tubular atrophy/interstitial fibrosis (T2 > 50% of cortical area involved), 44% with crescent in< 25% of glomeruli(C1), and 4.6% with crescent in> 25% of glomeruli (C2). All children were followed for a medial of 7.2 (4.6-11.7) years, 171 children (14%) arrived at the combined endpoint. The multivariate COX regression model revealed that the presence of lesions S (HR2.7,95%CI 1.8 ~ 4.2, P<0.001) and T (HR6.6,95%CI 3.9 ~ 11.3, P<0.001) may be the reason for poorer prognosis in the whole cohort. In contrast, C lesion showed a significant association with the outcome only in children received no immunosuppressive treatment.

CONCLUSIONS

This study revealed that S and T lesions were useful as the long-term renal prognostic factors among Chinese IgAN children.

Mechanisms of Podocyte Detachment, Podocyturia, and Risk of Progression of Glomerulopathies

Background

Glomerulopathies are the main cause of ESRD. Primary or secondary causes of glomerular diseases comprise more than 70% of cases that end up in renal replacement therapies.

Summary

The total glomerular mass that each individual contains is key to maintaining normal kidney function. Diabetes, hypertension, and any primary or secondary glomerulopathy may threaten the normal glomerular function. In fact, any glomerular insult may alter the glomerular filtration barrier, which in turn is composed by the podocyte, the glomerular basement membrane, and the capillary endothelial cell. Deposition of immune complexes, antibodies, or complement components at the subepithelial, intramembranous, or subendothelial space, and mutations in podocyte, slit diaphragm, or glomerular basement membrane proteins or enzymes are the main etiologies of glomerular alterations. Podocytes are glomerular cells that do not divide under normal circumstances. In this respect, maintenance of the absolute podocyte number per glomer-ulus is critical for normal glomerular function. As the insult progresses, podocytes start to detach from the glomerular basement membrane. When the podocyte loss is over 40% in a glomerulus, glomerulosclerosis develops, and obliteration of the glomerulus is the rule. In clinical grounds, this phenomenon is diagnosed mainly by proteinuria and a decline in glomerular filtration rate.

Key messages

In this review article, the impact of podocyturia in glomerular diseases and the main mechanisms of podocyte detachment are discussed. Finally, potential targets of therapeutic approach are suggested.

Renal progenitor cells modulated by angiotensin II receptor blocker (ARB) medication and differentiation towards podocytes in anti-thy1.1 nephritis

Background

Mesangial proliferative glomerulonephritis (MsPGN) is an epidemic disease with increasing occurrence. As important as mesangial cells, podocytes are key innate cells for MsPGN prognosis and recovery. Renal progenitor cells, located at the urinary pole (UP) of Bowman’s capsule (BC), could alleviate kidney injury through their capacity to differentiate into podocytes.

Methods

Seventy-two male rats were categorized randomly into the sham (n=24), untreated Thy-1 (n=24) and losartan-treated (n=24) groups. We administered vehicle or losartan (50 mg/kg by gavage) daily to treat rats with anti-thy1.1 nephritis, an ideal model to simulate human MsPGN. Two weeks after the intravenous injection of antibody, urinary protein and blood samples were analyzed, pathological changes were examined, the number of podocytes was determined, and renal progenitor cells were studied.

Results

Anti-thy1.1 nephritis was significantly alleviated after losartan treatment, as reported previously and as expected. Compared with the untreated Thy-1 group, the number of podocytes in the losartan group increased, and the area of renal progenitor cells significantly increased. The protein expression of components of the p-ERK pathway was determined during the development of renal progenitor cells differentiating into podocytes.

Conclusions

The data in this paper show the direct glomerular cell action of angiotensin II receptor blocker (ARB) treatment in improving outcomes in anti-thy1.1 nephritis. The positive effects of ARB medication on anti-thy1.1 nephritis were due to an increase in the number of renal epithelial progenitor cells (defined as PECs that expressed only stem cell markers without podocyte proteins).

Association of glomerular DNA damage and DNA methylation with one-year eGFR decline in IgA nephropathy

Accumulation of DNA double-strand breaks (DSBs) is linked to aging and age-related diseases. We recently reported the possible association of DNA DSBs with altered DNA methylation in murine models of kidney disease. However, DSBs and DNA methylation in human kidneys was not adequately investigated. This study was a cross-sectional observational study to evaluate the glomerular DNA DSB marker γH2AX and phosphorylated Ataxia Telangiectasia Mutated (pATM), and the DNA methylation marker 5-methyl cytosine (5mC) by immunostaining, and investigated the association with pathological features and clinical parameters in 29 patients with IgA nephropathy. To evaluate podocyte DSBs, quantitative long-distance PCR of the nephrin gene using laser-microdissected glomerular samples and immunofluorescent double-staining with WT1 and γH2AX were performed. Glomerular γH2AX level was associated with glomerular DNA methylation level in IgA nephropathy. Podocytopathic features were associated with increased number of WT1(+)γH2AX(+) cells and reduced amount of PCR product of the nephrin gene, which indicate podocyte DNA DSBs. Glomerular γH2AX and 5mC levels were significantly associated with the slope of eGFR decline over one year in IgA nephropathy patients using multiple regression analysis adjusted for age, baseline eGFR, amount of proteinuria at biopsy and immunosuppressive therapy after biopsy. Glomerular γH2AX level was associated with DNA methylation level, both of which may be a good predictor of renal outcome in IgA nephropathy.

The role of complement in IgA nephropathy

IgA nephropathy (IgAN) is common and often progresses to end stage renal disease. IgAN encompasses a wide range of histology and clinical features. IgAN pathogenesis is incompletely understood; the current multi-hit hypothesis of IgAN pathogenesis does not explain the range of glomerular inflammation and renal injury associated with mesangial IgA deposition. Although associations between IgAN and glomerular and circulating markers of complement activation are established, the mechanism of complement activation and contribution to glomerular inflammation and injury are not defined. Recent identification of specific complement pathways and proteins in severe IgAN cases had advanced our understanding of complement in IgAN pathogenesis. In particular, a growing body of evidence implicates the complement factor H related proteins 1 and 5 and lectin pathway as pathogenic in a subset of patients with severe disease. These data suggest complement deregulation and activity may be dominant drivers of renal injury in IgAN. Thereby, markers of complement activation may identify IgAN patients likely to progress to significant renal impairment and complement inhibition may emerge as an effective method of preventing and reducing glomerular injury in IgAN.