Recurrence of idiopathic nephrotic syndrome after renal transplantation

Past and future in vitro and in vivo approaches toward circulating factors and biomarkers in idiopathic nephrotic syndrome

Predicting the risks of progression to chronic kidney disease (CKD) stage 5 in idiopathic nephrotic syndrome (NS) and recurrence of the disease (rNS) following kidney transplantation (KT) is a key assessment to provide essential management information. NS has been categorized etiologically as genetic and immune-based. A genetic cause can be identified in ~ 30% of children with steroid-resistant NS (SRNS), a finding associated with a very low risk of rNS following KT. In immune-based NS, clinical overlap is observed among steroid-sensitive NS, secondary-resistant NS, and SRNS not associated with disease-causing genetic variants (non-monogenic SRNS). While ~ 50% of SRNS patients with no identified monogenic disease respond to intensified immunosuppressive treatments, the ones that do not respond to this therapy have a high risk of progression to CKD stage 5 and post-KT rNS. Secondary-resistant patients who progress to CKD stage 5 display the highest risk of post-KT rNS. The proposed shared underlying mechanism of the immune-based NS associated with post-KT rNS is based on a systemic circulating factor (CF) that affects glomerular permeability by inducing foot process effacement and focal segmental glomerulosclerosis. However, identifying patients without a detected genetic form who will recur post-KT is a major challenge. Extensive efforts, therefore, have been made to identify CFs and biomarkers potentially capable of predicting the risk of progression to CKD stage 5 and post-KT rNS. This review discusses the in vitro and in vivo approaches employed to date to identify and characterize potential CFs and CF-induced biomarkers of recurrent NS and offers an assessment of their potential to improve outcomes of KT in this patient population.

The Pathogenesis of Nephrotic Syndrome: A Perspective from B Cells

Background

Nephrotic syndrome is a special type of chronic kidney disease, the specific pathogenesis of which remains unclear. An increasing number of studies have suggested that B cells play an important role in the pathogenesis of nephrotic syndrome.

Summary

Idiopathic nephrotic syndrome is a common kidney disease in children. While previously believed to be primarily caused by T-cell disorders, recent research has shifted its focus to B cells. Studies have shown that B cells play a significant role in the pathogenesis of NS, potentially even more so than T cells. This article provides a comprehensive review of the involvement of B cells in the development of idiopathic nephrotic syndrome.

Key Messages

B cells are involved in the pathogenesis of nephrotic syndrome by producing autoantibodies and various cytokines.

Anti-nephrin autoantibodies: novel predictors of post-transplant recurrence of focal segmental glomerular sclerosis

Post-transplant recurrence of focal segmental glomerular sclerosis (FSGS) is a major challenge in the field of kidney transplantation. Currently, the most reliable predictor of FSGS recurrence is disease recurrence in a previous allograft. Recent studies suggest a possible causal role of anti-nephrin autoantibodies in the primary disease (primary FSGS and minimal change disease), as well as post-transplant recurrence of FSGS. In this issue of Kidney International, Batal et al. evaluate pretransplant anti-nephrin autoantibodies as a specific predictor of FSGS recurrence and demonstrate colocalization of nephrin and punctate IgG in anti-nephrin-positive patients with disease recurrence.

Potential biomarkers of recurrent FSGS: a review

Focal segmental glomerulosclerosis (FSGS), a clinicopathological condition characterized by nephrotic-range proteinuria, has a high risk of progression to end-stage renal disease (ESRD). Meanwhile, the recurrence of FSGS after renal transplantation is one of the main causes of graft loss. The diagnosis of recurrent FSGS is mainly based on renal puncture biopsy transplants, an approach not widely consented by patients with early mild disease. Therefore, there is an urgent need to find definitive diagnostic markers that can act as a target for early diagnosis and intervention in the treatment of patients. In this review, we summarize the domestic and international studies on the pathophysiology, pathogenesis and earliest screening methods of FSGS and describe the functions and roles of specific circulating factors in the progression of early FSGS, in order to provide a new theoretical basis for early diagnosis of FSGS recurrence, as well as aid the exploration of therapeutic targets.

Post-transplant recurrence of focal segmental glomerular sclerosis: consensus statements

Focal segmental glomerular sclerosis (FSGS) is 1 of the primary causes of nephrotic syndrome in both pediatric and adult patients, which can lead to end-stage kidney disease. Recurrence of FSGS after kidney transplantation significantly increases allograft loss, leading to morbidity and mortality. Currently, there are no consensus guidelines for identifying those patients who are at risk for recurrence or for the management of recurrent FSGS. Our work group performed a literature search on PubMed/Medline, Embase, and Cochrane, and recommendations were proposed and graded for strength of evidence. Of the 614 initially identified studies, 221 were found suitable to formulate consensus guidelines for recurrent FSGS. These guidelines focus on the definition, epidemiology, risk factors, pathogenesis, and management of recurrent FSGS. We conclude that additional studies are required to strengthen the recommendations proposed in this review.

Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis

The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.

Identification of Novel Genetic Risk Factors for Focal Segmental Glomerulosclerosis in Children: Results From the Chronic Kidney Disease in Children (CKiD) Cohort

RATIONALE & OBJECTIVE

Focal segmental glomerulosclerosis (FSGS) is a major cause of pediatric nephrotic syndrome, and African Americans exhibit an increased risk for developing FSGS compared with other populations. Predisposing genetic factors have previously been described in adults. Here we performed genomic screening of primary FSGS in a pediatric African American population.

STUDY DESIGN

Prospective cohort with case-control genetic association study design.

SETTING & PARTICIPANTS

140 African American children with chronic kidney disease from the Chronic Kidney Disease in Children (CKiD) cohort, including 32 cases with FSGS.

PREDICTORS

Over 680,000 common single-nucleotide polymorphisms (SNPs) were tested for association. We also ran a pathway enrichment analysis and a human leucocyte antigen (HLA)-focused association study.

OUTCOME

Primary biopsy-proven pediatric FSGS.

ANALYTICAL APPROACH

Multivariate logistic regression models.

RESULTS

The genome-wide association study revealed 169 SNPs from 14 independent loci significantly associated with FSGS (false discovery rate [FDR]<5%). We observed notable signals for genetic variants within the APOL1 (P=8.6×10^-7; OR, 25.8 [95% CI, 7.1-94.0]), ALMS1 (P=1.3×10^-7; 13.0% in FSGS cases vs 0% in controls), and FGFR4 (P=4.3×10^-6; OR, 24.8 [95% CI, 6.3-97.7]) genes, all of which had previously been associated with adult FSGS, kidney function, or chronic kidney disease. We also highlighted novel, functionally relevant genes, including GRB2 (which encodes a slit diaphragm protein promoting podocyte structure through actin polymerization) and ITGB1 (which is linked to renal injuries). Our results suggest a major role for immune responses and antigen presentation in pediatric FSGS through (1) associations with SNPs in PTPRJ (or CD148, P=3.5×10^-7), which plays a role in T-cell receptor signaling, (2) HLA-DRB1∗11:01 association (P=6.1×10^-3; OR, 4.5 [95% CI, 1.5-13.0]), and (3) signaling pathway enrichment (P=1.3×10^-6).

LIMITATIONS

Sample size and no independent replication cohort with genomic data readily available.

CONCLUSIONS

Our genetic study has identified functionally relevant risk factors and the importance of immune regulation for pediatric primary FSGS, which contributes to a better description of its molecular pathophysiological mechanisms.

Urinary CD80 and Serum suPAR as Biomarkers of Glomerular Disease among Adults in Brazil

INTRODUCTION

Urinary CD80 has been shown to have good specificity for minimal change disease (MCD) in children. However, the investigation of circulating factors such as soluble urokinase plasminogen activator receptor (suPAR) as biomarkers of focal segmental glomerulosclerosis (FSGS) is quite controversial. The objective of this study was to determine whether urinary CD80 and serum suPAR can be used for the diagnosis of MCD and FSGS, respectively, in the adult population of Brazil. We also attempted to determine whether those biomarkers assess the response to immunosuppressive treatment.

METHODS

This was a prospective study in which urine and blood samples were collected for analysis of CD80 and suPAR, respectively, only in the moment of renal biopsy, from patients undergoing to diagnostic renal biopsy. At and six months after biopsy, we analyzed serum creatinine, serum albumin, and proteinuria in order to evaluate the use of the CD80 and suPAR collected in diagnosis as markers of response to immunosuppressive treatment. In healthy controls were collected urinary CD80 and proteinuria, serum suPAR, and creatinine.

RESULTS

The results of 70 renal biopsies were grouped, by diagnosis, as follows: FSGS (n = 18); membranous nephropathy (n = 14); MCD (n = 5); and other glomerulopathies (n = 33). There was no significant difference among the groups in terms of the urinary CD80 levels, and serum suPAR was not significantly higher in the FSGS group, as would have been expected. Urinary CD80 correlated positively with nephrotic syndrome, regardless of the type of glomerular disease. Neither biomarker correlated with proteinuria at six months after biopsy.

CONCLUSION

In adults, urinary CD80 can serve as a marker of nephrotic syndrome but is not specific for MCD, whereas serum suPAR does not appear to be useful as a diagnostic or treatment response marker.

Ion channels and channelopathies in glomeruli

An essential step in renal function entails the formation of an ultrafiltrate that is delivered to the renal tubules for subsequent processing. This process, known as glomerular filtration, is controlled by intrinsic regulatory systems and by paracrine, neuronal, and endocrine signals that converge onto glomerular cells. In addition, the characteristics of glomerular fluid flow, such as the glomerular filtration rate and the glomerular filtration fraction, play an important role in determining blood flow to the rest of the kidney. Consequently, disease processes that initially affect glomeruli are the most likely to lead to end-stage kidney failure. The cells that comprise the glomerular filter, especially podocytes and mesangial cells, express many different types of ion channels that regulate intrinsic aspects of cell function and cellular responses to the local environment, such as changes in glomerular capillary pressure. Dysregulation of glomerular ion channels, such as changes in TRPC6, can lead to devastating glomerular diseases, and a number of channels, including TRPC6, TRPC5, and various ionotropic receptors, are promising targets for drug development. This review discusses glomerular structure and glomerular disease processes. It also describes the types of plasma membrane ion channels that have been identified in glomerular cells, the physiological and pathophysiological contexts in which they operate, and the pathways by which they are regulated and dysregulated. The contributions of these channels to glomerular disease processes, such as focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy, as well as the development of drugs that target these channels are also discussed.

Study on the relationship between nephrotic syndrome and atopic diseases in childhood

OBJECTIVE

The present study aimed to explore the relationship between nephrotic syndrome and atopic diseases in childhood.

METHODS

From 2018 to 2019, 234 children with first-onset primary nephrotic syndrome (PNS) were selected for observation and long-term follow-up, and the clinical and laboratory data. To compare the levels of total serum IgE, histamine and bradykinin of the same children at the time of first onset, remission and relapse of PNS. The extent of podocyte foot process effacement was compared between the urinary protein negative-conversion group and the proteinuric group with the NS range. The correlation between the urine protein quantification and the extent of foot process effacement was also observed.

RESULTS

(1) The mean age of 234 children with first-onset PNS was 4.82 ± 3.63 years, with a male to female ratio of 162/72. (2) There were 109 cases (46.58%) with concomitant atopic diseases (AD) and 151 cases (64.53%) with elevated levels of total serum IgE. There were 136 cases with recurrence during the follow-up, of which recurrence due to allergy-related factors was greater than that due to infection-related factors. (3) The total IgE and bradykinin serum levels were significantly higher in children with first-onset PNS and recurrent PNS compared with those in remission, and the differences were statistically significant (P < 0.05). The level of histamine in children with first-onset PNS was higher than that in children with remission (P < 0.05), and there was no significant difference in the level of histamine between children in the recurrence group and those in the remission group (P > 0.05). (4) There was no significant difference in the extent of foot process effacement between the urinary protein negative-conversion group and the proteinuric group with the NS range. There was no significant correlation between the proteinuria quantification and the extent of foot process effacement.

CONCLUSION

There existed a high co-morbidity with AD in children with PNS, and allergy-related factors might be an important recurrence factor in children with PNS. The injury to the filtration barrier in MCD might not only be correlated with podocyte lesions but also with some serum permeability factors. Serum IgE, histamine, and bradykinin might be the plasma permeability factors in children with PNS.

The role of the immune system in idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome (INS) in children is characterized by massive proteinuria and hypoalbuminemia and usually responds well to steroids. However, relapses are frequent, which can require multi-drug therapy with deleterious long-term side effects. In the last decades, different hypotheses on molecular mechanisms underlying INS have been proposed and several lines of evidences strongly indicate a crucial role of the immune system in the pathogenesis of non-genetic INS. INS is traditionally considered a T-cell-mediated disorder triggered by a circulating factor, which causes the impairment of the glomerular filtration barrier and subsequent proteinuria. Additionally, the imbalance between Th17/Tregs as well as Th2/Th1 has been implicated in the pathomechanism of INS. Interestingly, B-cells have gained attention, since rituximab, an anti-CD20 antibody demonstrated a good therapeutic response in the treatment of INS. Finally, recent findings indicate that even podocytes can act as antigen-presenting cells under inflammatory stimuli and play a direct role in activating cellular pathways that cause proteinuria. Even though our knowledge on the underlying mechanisms of INS is still incomplete, it became clear that instead of a traditionally implicated cell subset or one particular molecule as a causative factor for INS, a multi-step control system including soluble factors, immune cells, and podocytes is necessary to prevent the occurrence of INS. This present review aims to provide an overview of the current knowledge on this topic, since advances in our understanding of the immunopathogenesis of INS may help drive new tailored therapeutic approaches forward.

Immunopathogenesis of idiopathic nephrotic syndrome in children: two sides of the coin

BACKGROUND

Idiopathic nephrotic syndrome is a common form of glomerular nephropathy in children, with an incidence rate of 1.15-16.9/100,000 depending on different nationalities and ethnicities. The etiological factors and mechanisms of childhood idiopathic nephrotic syndrome have not yet been fully elucidated. This review summarizes the progress of the immunopathogenesis of idiopathic nephrotic syndrome in children.

DATA SOURCES

We review the literature on the immunopathogenesis of idiopathic nephrotic syndrome in children. Databases including Medline, Scopus, and Web of Science were searched for studies published in any language with the terms "children", "idiopathic nephrotic syndrome", "immunopathogenesis", "T cells", "circulating permeability factors", and "B cells".

RESULTS

Dysfunction in T lymphocytes and pathogenic circulatory factors were indicated to play key roles in the pathogenesis of idiopathic nephrotic syndrome. Recently, some studies have shown that cellular immune dysfunction may also be involved in the pathogenesis of idiopathic nephrotic syndrome.

CONCLUSIONS

Both T- and B-cell dysfunction may play significant roles in the pathogenesis of idiopathic nephrotic syndrome, like two sides of one coin, but the role of B cell seems more important than T cells.

Cyclophosphamide as a Treatment for Focal Segmental Glomerular Sclerosis Recurrence in a Kidney Transplant Patient

Patient: Female, 24-year-old

Final Diagnosis: Focal segmental glomerulosclerosis

Symptoms: Facia • lower extremity edema

Medication: —

Clinical Procedure: —

Specialty: Nephrology

Autoimmunity in Focal Segmental Glomerulosclerosis: A Long-Standing Yet Elusive Association

Focal segmental glomerulosclerosis (FSGS) is a histological term that describes a pathologic renal entity affecting both adults and children, with a wide array of possible underlying etiologies. Podocyte damage with scarring, the hallmark of this condition, leads to altered permeability of the glomerular barrier, which may result in massive proteinuria and relentless renal function deterioration. A definite cause of focal segmental glomerulosclerosis can be confirmed in a minority of cases, while most forms have been traditionally labeled as primary or idiopathic. Despite this definition, increasing evidence indicates that primary forms are a heterogenous group rather than a single disease entity: several circulating factors that may affect glomerular permeability have been proposed as potential culprits, and both humoral and cellular immunity have been implicated in the pathogenesis of the disease. Consistently, immunosuppressive drugs are considered as the cornerstone of treatment for primary focal segmental glomerulosclerosis, but response to these agents and long-term outcomes are highly variable. In this review we provide a summary of historical and recent advances on the pathogenesis of primary focal segmental glomerulosclerosis, focusing on implications for its differential diagnosis and treatment.

Different effects of rituximab on a native kidney and a post-transplant kidney with recurrence of focal segmental glomerulosclerosis

We present the case of a 29-year-old woman with focal segmental glomerulosclerosis (FSGS) who was treated with rituximab administration under different conditions for refractory nephrotic syndrome and posttransplant FSGS recurrence. At the age of 13 years, she developed FSGS, which followed a refractory clinical course, and eventually necessitated her to undergo plasmapheresis and receive rituximab at the age of 25 years. However, both therapies were ineffective, and she subsequently had progressive renal failure, for which dialysis was initiated at the age of 26 years. At the age of 28 years, she received a renal transplant from a living donor. However, nearly 1 year after the transplantation, nephrotic-range proteinuria was observed and FSGS recurrence was confirmed via biopsy of the transplanted kidney. Plasmapheresis resulted in complete remission, which was maintained by rituximab administration, and the patient followed a favorable course. To date, there have been no reports on the effect of rituximab on both the native kidney and post-transplant FSGS recurrence in the same patient. Interestingly, this case showed different responses to rituximab administration.

Idiopathic nephrotic syndrome and serum permeability factors: a molecular jigsaw puzzle

Nephrotic syndrome is traditionally defined using the triad of edema, hypoalbuminemia, and proteinuria, but this syndrome is very heterogeneous and difficult to clarify. Its idiopathic form (INS) is probably the most harmful and essentially comprises two entities: minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). We will consider some hypotheses regarding the mechanisms underlying INS: (i) the presence of several glomerular permeability factors in the sera of patients that alter the morphology and function of podocytes leading to proteinuria, (ii) the putative role of immune cells. Thanks to recent data, our understanding of these disorders is evolving towards a more multifactorial origin. In this context, circulating factors may be associated according to sequential kinetic mechanisms or micro-environmental changes that need to be determined. In addition, the resulting proteinuria may trigger more proteinuria enhancing the glomerular destabilization.

[Idiopathic nephrotic syndrome: une Arlésienne?]

The renal filtration is ensured by the kidney glomeruli selective for filtering the blood. The main actor of the glomerular filter is the podocyte whose interlaced pedicels bear protein complexes (nephrin, podocin, etc.) creating a molecular sieve (slit diaphragm) to achieve the filtration. Alterations of these podocytes lead to massive proteinuria, which characterizes the nephrotic syndrome. The idiopathic form is one of the most malignant and essentially comprises two entities: minimal change disease and focal segmental glomerulosclerosis. Many observations indicated that (1) immune cells are involved and that (2) there are several permeability factors in the blood that affect the morphology and function of podocytes (slit diaphragm with fractional foot processes fusion/effacement). Evidence for a permeability factor was chiefly derived from remission of proteinuria observed after implantation of a kidney with FSGS in healthy recipients or with other kidney diseases. Today, we are moving towards a multifactorial conception of the nephrotic syndrome where all these barely known factors could be associated according to a sequential kinetic mechanism that needs to be determined.

Disease Recurrence-The Sword of Damocles in Kidney Transplantation for Primary Focal Segmental Glomerulosclerosis

A major obstacle in kidney transplantation for primary focal segmental glomerulosclerosis (FSGS) is the risk of disease recurrence. Recurrent FSGS affects up to 60% of first kidney grafts and exceeds 80% in patients who have lost their first graft due to recurrent FSGS. Clinical and experimental evidence support the hypothesis that a circulating permeability factor is the mediator in the pathogenesis of primary and recurrent disease. Despite all efforts, the causing agent has not yet been identified. Several treatment options for the management of recurrent FSGS have been proposed. In addition to plasma exchange, B-cell depleting antibodies are effective in recurrent FSGS. This indicates, that the secretion and/or activity of the postulated circulating permeability factor(s) may be B-cell related. This review summarizes the current knowledge on permeability factor(s) possibly related to the disease and discusses strategies for the management of recurrent FSGS. These include profound B-cell depletion prior to transplantation, as well as the salvage of an allograft affected by recurrent FSGS by transfer into a second recipient.

European Society of Pediatric Nephrology survey on current practice regarding recurrent focal segmental glomerulosclerosis after pediatric kidney transplantation

INTRODUCTION

Primary FSGS is an important cause of ESRD in children. FSGS recurrence after kidney transplantation is associated with early graft loss. No guidelines for treatment of FSGS recurrence exist. We conducted a survey to gain insight into variation of treatment between centers.

METHODS

A survey was sent to all members of the ESPN on behalf of the "Renal Transplantation" and "Idiopathic Nephrotic Syndrome" working groups.

RESULTS

Fifty-nine nephrologists from 31 countries responded, reporting 807 FSGS patients, with 241 (30%) FSGS recurrences after transplantation. Recurrence varied from 0% to 100% between respondents. Native nephrectomy before or during transplantation was performed, respectively, always (37%), never (39%), or on clinical indication (17%). Half of the respondents started preventive treatment before transplantation, using PF (n = 10); R (n = 4); PF or IA, plus R (n = 9); cyclosporine (n = 2); or unknown (n = 4). Immunosuppressive therapy for patients without known mutations consisted of a combination of steroids, tacrolimus/cyclosporine, and MMF, with or without IL-2R-blockade in, respectively, 61% and 86% of the respondents. Sixty-three percent applied a similar regimen to patients with known mutations. FSGS recurrence was treated with PF or IA, plus R by 66% of respondents; 54% observed no response. Complete remission in >50% of patients was reported by 41% of the respondents.

DISCUSSION

FSGS recurrence after transplantation is common, but varies greatly between centers. We found great variability in preventive and therapeutic treatment regimens. Future research should focus on predisposing factors, including biopsy findings and genetic mutations, and standardized treatment.

TRPC channels: Regulation, dysregulation and contributions to chronic kidney disease

Mutations in the gene encoding canonical transient receptor potential-6 (TRPC6) channels result in severe nephrotic syndromes that typically lead to end-stage renal disease. Many but not all of these mutations result in a gain in the function of the resulting channel protein. Since those observations were first made, substantial work has supported the hypothesis that TRPC6 channels can also contribute to progression of acquired (non-genetic) glomerular diseases, including primary and secondary FSGS, glomerulosclerosis during autoimmune glomerulonephritis, and possibly in type-1 diabetes. Their regulation has been extensively studied, especially in podocytes, but also in mesangial cells and other cell types present in the kidney. More recent evidence has implicated TRPC6 in renal fibrosis and tubulointerstitial disease caused by urinary obstruction. Consequently TRPC6 is being extensively investigated as a target for drug discovery. Other TRPC family members are present in kidney. TRPC6 can form a functional heteromultimer with TRPC3, and it has been suggested that TRPC5 may also play a role in glomerular disease progression, although the evidence on this is contradictory. Here we review literature on the expression and regulation of TRPC6, TRPC3 and TRPC5 in various cell types of the vertebrate kidney, the evidence that these channels are dysregulated in disease models, and research showing that knock-out or pharmacological inhibition of these channels can reduce the severity of kidney disease. We also summarize several areas that remain controversial, and some of the large gaps of knowledge concerning the fundamental role of these proteins in regulation of renal function.

The incessant search for renal biomarkers: is it really justified?

PURPOSE OF REVIEW

This review summarizes the most recent and relevant findings in the search for novel biomarkers for the most common renal diseases.

RECENT FINDINGS

Unprecedented, fast-paced technical advances in biomedical research have offered an opportunity to identify novel and more specific renal biomarkers in several clinical settings. However, despite the huge efforts made, the molecules identified so far have generally failed to provide relevant information beyond what has already been generated by established biomarkers, such as serum creatinine and proteinuria, whereas the complexity and costs of these technology platforms hamper their widespread implementation.

SUMMARY

No novel renal biomarkers have added clear-cut additional value in clinical decision-making. The only exception is anti-phospholipase A2 receptor antibodies, which have been implemented successfully as a diagnostic and prognostic biomarker of membranous nephropathy. This achievement, along with the large number of ongoing collaborative projects worldwide, should lead the renal community to be quite confident regarding the successful qualification of novel and effective diagnostic, prognostic and therapeutic response biomarkers for kidney diseases, hopefully in the next few years.

Recurrence of nephrotic syndrome following kidney transplantation is associated with initial native kidney biopsy findings

BACKGROUND AND OBJECTIVES

Steroid-resistant nephrotic syndrome (SRNS) due to focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) is a leading cause of end-stage kidney disease in children. Recurrence of primary disease following transplantation is a major cause of allograft loss. The clinical determinants of disease recurrence are not completely known. Our objectives were to determine risk factors for recurrence of FSGS/MCD following kidney transplantation and factors that predict response to immunosuppression following recurrence.

METHODS

Multicenter study of pediatric patients with kidney transplants performed for ESKD due to SRNS between 1/2006 and 12/2015. Demographics, clinical course, and biopsy data were collected. Patients with primary-SRNS (PSRNS) were defined as those initially resistant to corticosteroid therapy at diagnosis, and patients with late-SRNS (LSRNS) as those initially responsive to steroids who subsequently developed steroid resistance. We performed logistic regression to determine risk factors associated with nephrotic syndrome (NS) recurrence.

RESULTS

We analyzed 158 patients; 64 (41%) had recurrence of NS in their renal allograft. Disease recurrence occurred in 78% of patients with LSRNS compared to 39% of those with PSRNS. Patients with MCD on initial native kidney biopsy had a 76% recurrence rate compared with a 40% recurrence rate in those with FSGS. Multivariable analysis showed that MCD histology (OR; 95% CI 5.6; 1.3-23.7) compared to FSGS predicted disease recurrence.

CONCLUSIONS

Pediatric patients with MCD and LSRNS are at higher risk of disease recurrence following kidney transplantation. These findings may be useful for designing studies to test strategies for preventing recurrence.

[Current insights about recurrence of glomerular diseases after renal transplantation]

Recurrence of glomerular disease after renal transplantation is a frequent cause of graft loss. Incidence, risk factors and outcome of recurrence are widely due to the underlying glomerular disease. Graft biopsy analysis is required to confirm the definitive diagnosis of recurrence and to start an appropriate therapy that, in some cases, remains challenging to prevent graft failure. Increased use of protocol biopsy and recent advances in our understanding of the pathogenesis of some glomerular diseases with the identification of some relevant biomarkers provide a unique opportunity to initiate kidney-protective therapy at early stages of recurrence on the graft. This review summarizes our current knowledge on the management of many recurrent primary and secondary glomerulonephritis after kidney transplantation.

Molecular Mechanisms of Proteinuria in Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular disease resulting in end-stage renal disease in the USA and is increasing in prevalence worldwide. It is a diverse clinical entity with idiopathic, genetic, metabolic, infectious, and other causes that culminate in a characteristic histologic pattern of injury. Proteinuria is a hallmark of FSGS as well as other primary and secondary glomerular disorders. The magnitude of proteinuria at disease onset and during treatment has prognostic implications for renal survival as well as associated cardiovascular morbidity and mortality. Significant advances over the last two decades have shed light on the molecular architecture of the glomerular filtration barrier. The podocyte is the target cell for injury in FSGS. A growing list of disease-causing gene mutations encoding proteins that regulate podocyte survival and homeostasis has been identified in FSGS patients. Several pathogenic and regulatory pathways have been uncovered that result in proteinuria in rodent models and human FSGS. The recurrence of proteinuria and FSGS after kidney transplantation is supporting evidence for the role of a circulating permeability factor in disease pathogenesis. These advances reviewed herein have significant implications for disease classification and therapeutic drug development for FSGS.

Immunology of idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (INS) is as yet unknown, but several lines of evidence indicate that the immune system may play a crucial pathogenic role in non-genetic INS. The most important of these are, first, the effectiveness of therapy based on immunosuppression and, second, a vast body of data derived both from experimental models and from patient studies that implicate T cells and more recently B cells as major players in INS pathogenesis. However, recent findings also suggest a direct role of podocytes as drivers of the disease process, and the interplay between the glomerulus and the immune system is still being elucidated. In this review we provide an overview of current knowledge on the role of different components of the immune system in determining disease. Advances in our understanding of the pathogenesis of INS may help drive new, more tailored therapeutic approaches.

Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome

BACKGROUND

Familial steroid-sensitive nephrotic syndrome (SSNS) is a rare condition. The disease pathophysiology remains elusive. However, bi-allelic mutations in the EMP2 gene were identified, and specific variations in HLA-DQA1 were linked to a high risk of developing the disease.

METHODS

Clinical data were analyzed in 59 SSNS families. EMP2 gene was sequenced in families with a potential autosomal recessive (AR) inheritance. Exome sequencing was performed in a subset of 13 families with potential AR inheritance. Two variations in HLA-DQA1 were genotyped in the whole cohort.

RESULTS

Transmission was compatible with an AR (n = 33) or autosomal dominant (AD, n = 26) inheritance, assuming that familial SSNS is a monogenic trait. Clinical features did not differ between AR and AD groups. All patients, including primary (n = 7) and secondary steroid resistant nephrotic syndrone (SRNS), (n = 13) were sensitive to additional immunosuppressive therapy. Both HLA-DQA1 variations were found to be highly linked to the disease (OR = 4.34 and OR = 4.89; p < 0.001). Exome sequencing did not reveal any pathogenic mutation, neither did EMP2 sequencing.

CONCLUSIONS

Taken together, these results highlight the clinical and genetic heterogeneity in familial SSNS. Clinical findings sustain an immune origin in all patients, whatever the initial steroid-sensitivity. The absence of a variant shared by two families and the HLA-DQA1 variation enrichments suggest a complex mode of inheritance.

Changes in podocyte TRPC channels evoked by plasma and sera from patients with recurrent FSGS and by putative glomerular permeability factors

Primary forms of focal and segmental glomerulosclerosis (FSGS) are driven by circulating factors that cause dysfunction or loss podocytes. Rare genetic forms of FSGS can be caused by mutations in TRPC6, which encodes a Ca2+-permeable cationic channel expressed in mesangial cells and podocytes; and NPHS2, which encodes podocin, a TRPC6-binding protein expressed in podocyte slit diaphragm domains. Here we observed that exposing immortalized mouse podocytes to serum or plasma from recurrent FSGS patients for 24h increased the steady-state cell-surface abundance of TRPC6, accompanied by an increase in currents through endogenous TRPC6 channels evoked by a hypoosmotic stretch stimulus. These effects were mimicked by the soluble urokinase receptor (suPAR) and by tumor necrosis factor (TNF), circulating factors implicated in nephrotic syndromes. Most but not all of the recurrent FSGS plasma samples that we examined also caused a loss of podocin over a period of several hours. The loss of podocin was also seen following exposure to suPAR but not TNF. However, TNF increased the effects of suPAR on TRPC6 and podocin, and TNF and suPAR are required for the full effects of one of the recurrent FSGS plasma samples. The actions of FSGS plasma, suPAR and TNF on surface abundance of TRPC6 were blocked by cilengitide, an inhibitor of αvβ3-integrin signaling. These data suggest that primary FSGS is a heterogeneous condition mediated by multiple circulating factors, and support TRPC6 and αvβ3-integrin as potential therapeutic targets.

Optimal management of primary focal segmental glomerulosclerosis in adults

Focal segmental glomerulosclerosis (FSGS) is a frequent glomerular kidney disease that is revealed by proteinuria or even nephrotic syndrome. A diagnosis can be established from a kidney biopsy that shows focal and segmental glomerulosclerosis. This histopathological lesion may be caused by a primary podocyte injury (idiopathic FSGS) but is also associated with other pathologies (secondary FSGS). The first-line treatment for idiopathic FSGS with nephrotic syndrome is a prolonged course of corticosteroids. However, steroid resistance or steroid dependence is frequent, and despite intensified immunosuppressive treatment, FSGS can lead to end-stage renal failure. In addition, in some cases, FSGS can recur on a graft after kidney transplantation: an unidentified circulating factor may be implicated. Understanding of its physiopathology is unclear, and it remains an important challenge for the scientific community to identify a specific diagnostic biomarker and to develop specific therapeutics. This study reviews the treatment of primary FSGS and the recurrence of FSGS after kidney transplantation in adults.

Idiopathic nephrotic syndrome: the EBV hypothesis

Steroid sensitive nephrotic syndrome is marked by a massive proteinuria and loss of podocytes foot processes. The mechanism of the disease remains debated but recent publications suggest a primary role of Epstein-Barr Virus (EBV). EBV replication in the peripheral blood is found in 50% of patients during the first flare of the disease. The genetic locus of steroid sensitive nephrotic syndrome was also identified as influencing antibodies directed against EBNA1. EBV is able to establish, latent benign infection in memory B cells that display phenotypes similar to antigen-selected memory B cells. Consistently, memory B cells reconstitution after rituximab infusion is a predictor of the relapse of proteinuria. We suggest that a specific anti-EBNA1 antibody internalized in the podocytes via the neonatal Fc receptor might cross-react with a major protein present in the same cell trafficking compartment. The diversion of this major podocyte protein in the urinary space and the subsequent depletion is supposed to result in podocyte damages with loss of foot processes and massive proteinuria. Immunosuppression of B cells and subsequent clearance of anti-EBNA1 antibodies would lead to a restoration of the normal level of the protein allowing recovery of proteinuria and of normal podocyte morphology.

Recent advances in our understanding of recurrent primary glomerulonephritis after kidney transplantation

Recurrent glomerulonephritis (GN) is an important cause of kidney allograft failure, particularly in younger recipients. Approximately 15% of death-censored graft failures are due to recurrent GN, but this incidence is likely an underestimation of the magnitude of the problem. Overall, 18% to 22% of kidney allografts are lost due to GN, either recurrent or presumed de novo. The impact of recurrent GN on allograft survival was recognized from the earliest times in kidney transplantation. However, progress in this area has been slow, and our understanding of GN recurrence remains limited, in large part due to incomplete understanding of the pathogenesis of these diseases. This review focuses on recent advances in our general understanding of the pathophysiology of primary GN, the risk of recurrence in the allograft, and the consequences for kidney graft survival. We focus specifically on the most common forms of primary GN, including focal segmental glomerulosclerosis, membranous nephropathy, membranoproliferative glomerulonephritis, and IgA nephropathy. New understanding of the pathogenesis of these diseases has had direct clinical implications for transplantation, allowing better identification of candidates at high risk of recurrence and earlier diagnoses, and it is expected to lead to significance improvements in the therapy and perhaps even prevention of GN recurrence. More than ever, it is essential to fully characterize GN before transplantation as this information will direct our management posttransplantation. Further, the relative rarity of recurrent GN dictates the need for multicenter studies in order to evaluate, test, and validate recent advances and therapies.

Soluble Urokinase Receptors in Focal Segmental Glomerulosclerosis: A Review on the Scientific Point of View

Focal segmental glomerulosclerosis (FSGS) is one of the primary glomerular disorders in both children and adults which can progress to end-stage renal failure. Although there are genetic and secondary causes, circulating factors have also been regarded as an important factor in the pathogenesis of FSGS, because about 40% of the patients with FSGS have recurrence after renal transplantation. Soluble urokinase-type plasminogen activator receptor (suPAR) is a soluble form of uPAR, which is a membrane-bound protein linked to GPI in various immunologically active cells, including podocytes. It has recently been suggested as a potential circulating factor in FSGS by in vitro podocyte experiments, in vivo mice models, and human studies. However, there have also been controversies on this issue, because subsequent studies showed conflicting results. suPAR levels were also increased in patients with other glomerular diseases and were inversely correlated with estimated glomerular filtration rate. Nevertheless, there has been no balanced review on this issue. In this review, we compare the conflicting data on the involvement of suPAR in the pathogenesis of FSGS and shed light on interpretation by taking into account many points and the potential variables and confounders influencing serum suPAR levels.

FSGS Recurrence in Adults after Renal Transplantation

Recurrence of focal segmental glomerulosclerosis (FSGS) in the allograft occurs in 30–50% of patients, and it is associated with poor renal allograft survival. Major risk factors for recurrence are younger age at diagnosis, rapid progression to end-stage renal disease, white race, and the loss of previous allografts due to recurrence. Recent data support the hypothesis that circulating permeability factors play a crucial role in podocyte injury and progression of FSGS. Due to lack of controlled trials, the management of recurrent FSGS is inconsistent and highly empirical. Prophylactic and perioperative treatment with plasmapheresis and high-dose (intravenous) cyclosporine represent the main cornerstones of immunosuppressive therapy. In recent years, therapy with rituximab has shown promising results. Despite evidence of activation of the renin-angiotensin system (RAS) in recurrent FSGS and its association with progression, only limited data exist on the renoprotective role of RAS blockade in this setting. Further well designed studies are needed on pathogenesis risk factors and therapeutical options in FSGS and its recurrence after transplantation.

Plasma Exchange for the Recurrence of Primary Focal Segmental Glomerulosclerosis in Adult Renal Transplant Recipients: A Meta-Analysis

Background. Posttransplant recurrence of primary focal segmental glomerulosclerosis (rFSGS) in the form of massive proteinuria is not uncommon and has detrimental consequences on renal allograft survival. A putative circulating permeability factor has been implicated in the pathogenesis leading to widespread use of plasma exchange (PLEX). We reviewed published studies to assess the role of PLEX on treatment of rFSGS in adults. Methods. Eligible manuscripts compared PLEX or variants with conventional care for inducing proteinuria remission (PR) in rFSGS and were identified through MEDLINE and reference lists. Data were abstracted in parallel by two reviewers. Results. We detected 6 nonrandomized studies with 117 cases enrolled. In a random effects model, the pooled risk ratio for the composite endpoint of partial or complete PR was 0,38 in favour of PLEX (95% CI: 0,23–0,61). No statistical heterogeneity was observed among included studies (I² = 0%, p = 0,42). On average, 9–26 PLEX sessions were performed to achieve PR. Renal allograft loss due to recurrence was lower (range: 0%–67%) in patients treated with PLEX. Conclusion. Notwithstanding the inherent limitations of small, observational trials, PLEX appears to be effective for PR in rFSGS. Additional research is needed to further elucidate its optimal use and impact on long-term allograft survival.

Renal and Hematological Effects of CLCF-1, a B-Cell-Stimulating Cytokine of the IL-6 Family

CLCF-1 is a cytokine known for B-cell stimulation and for neurotrophic properties. We have identified CLCF-1 as a potential injurious factor in the human renal disease focal segmental glomerulosclerosis (FSGS). We investigated its effects on renal cells and renal function in in vitro and in vivo studies. Methods include measurement of the effect of CLCF-1 on phosphorylation of target molecules of the JAK/STAT pathway, on cytoskeleton and cell morphology in cultured podocytes, on albumin permeability of isolated rat glomeruli, and on tissue phosphorylation and urine albumin after acute or chronic CLCF-1 injection. In addition, cell sorting was performed to determine the presence of cells expressing CLCF-1 in spleen and bone marrow of normal mice and the effect of CLCF-1 infusion on splenic B-cell populations. CLCF-1 increased phosphorylation of STAT3 in multiple cell types, activated podocytes leading to formation of lamellipodia and decrease in basal stress fibers, increased glomerular albumin permeability, and increased STAT3 phosphorylation of peripheral blood cells and renal cortex. CLCF-1 increased urine albumin/creatinine ratio in mice and increased B-cell expression of IgG in mouse spleen. We conclude that CLCF-1 has potentially important systemic effects, alters podocyte function, and may contribute to renal dysfunction and albuminuria.

Permeability factors in idiopathic nephrotic syndrome: historical perspectives and lessons for the future

The term idiopathic nephrotic syndrome (iNS) traditionally covers minimal change disease and primary focal segmental glomerulosclerosis (FSGS), now thought to be separate disease entities. Clinical and experimental evidence suggest that circulating permeability factors are involved in their pathogenesis. In the past four decades, many investigators have searched for the responsible factors, thus far with little success. The recent report of the soluble urokinase plasminogen activator receptor as a causative factor in FSGS has received much attention, but again the initially promising findings were not confirmed. We describe the history of the search for permeability factors, discuss the pitfalls that are likely responsible for the lack of success and propose criteria that should be used in future studies when evaluating candidate permeability factors.

Understanding podocytopathy and its relevance to clinical nephrology

Podocytopathies are the most common group of glomerular disorder leading to proteinuria. On the basis of pathophysiology, light microscopic and ultrastructural evaluation, the podocytopathies include minimal change disease, diffuse mesangial sclerosis, focal segmental glomerulosclerosis and collapsing glomerulopathy. The present review summarizes the basic etiopathogenesis of podocytopthies, highlights the common genetic and acquired factors in its causation, puts forth various diagnostic modalities and discusses the role of emerging agents or treatment.

Focal and segmental glomerulosclerosis: clinical and kidney biopsy correlations

Background

Primary focal segmental glomerulosclerosis (FSGS) is a common glomerular disease in adults and ranks among the top causes of a primary glomerular disease causing end-stage renal disease (ESRD). Primary FSGS is, however, a diagnosis of exclusion and distinction between primary versus secondary FSGS is not always obvious, resulting in a number of patients with secondary FSGS undergoing unnecessary immunosuppressive therapy.

Methods

We reviewed the Mayo Clinic Renal Pathology Database for patients with a diagnosis of FSGS on native renal biopsy and divided the patients into nephrotic syndrome-associated (NS-associated) and non-nephrotic syndrome-associated (NNS-associated) FSGS as a first approximation followed by dividing the lesion according to the degree of foot process effacement (FPE) on electron microscopy (EM) examination.

Results

A total of 41 patients with FSGS with complete evaluation were identified. Of these, 18 were classified as having NS and 23 were classified as having NNS. Baseline characteristics (age, gender, body mass index, serum creatinine and hematuria) were not different between the groups. All of the patients with NS showed diffuse FPE ranging from 80 to 100% (mean 96%). On the other hand, of the 23 patients in the NNS group, 22 had segmental FPE and showed patchy effacement, with all cases showing 20–60% FPE (mean of 48%).

Conclusion

Adult patients presenting with NS, an FSGS lesion on LM, extensive FPE (≥80%) on EM examination and no risk factors associated with secondary FSGS are likely to have primary FSGS. Conversely, the absence of NS in a patient with segmental FPE on EM strongly suggests a secondary FSGS. Dividing FSGS into the presence or absence of NS together with the degree of FPE on EM examination is more helpful as it provides a more practical way to separate patients into cases of primary versus secondary FSGS.

Rituximab in idiopathic nephrotic syndrome: does it make sense?

Idiopathic nephrotic syndrome (INS) includes three different entities: minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and mesangial proliferative glomerulonephritis. Historically, this condition has been attributed to a T-cell disorder resulting in the secretion of a circulating factor that increases glomerular permeability to plasma proteins. The therapeutic approach to control the proteinuria of INS remains the use of drugs that have been considered to suppress the production of the "circulating factor" secreted by T cells. Recently, rituximab (RTX), a chimeric monoclonal antibody directed against the CD20 cell surface receptor expressed on B cells, has emerged as potential therapeutic agent. The number of publications reporting clinical experience with RTX in the treatment of nephrotic syndrome has greatly increased in the last few years. However, there is currently no good evidence from clinical or experimental studies that support a role of RTX in the treatment of MCD and FSGS proteinuria. In summary, there is the need for a better understanding of the pathogenesis of the proteinuria in INS and the potential role of RTX in this condition.

Recurrence of idiopathic focal segmental glomerulosclerosis after kidney transplantation: experience of a Korean tertiary center

FSGS is the second most common cause of idiopathic NS in children. It often progresses to ESRD and commonly recurs after KT. To investigate the risk factors and the prognosis of recurrence in pediatric idiopathic FSGS in Korea, retrospective review of 43 KT in 38 children with idiopathic FSGS of last two decades was conducted. The patients presented at the median age of 5.1 yr (range 1.1-13.8 yr) and received KT 5.7 yr later (range 1.3-17.6 yr). FSGS recurred in 20 allografts immediately after transplantation, only in those who presented with NS but not in those who presented with AUA. The risk factors for recurrence were age of onset >5 yr and progression to ESRD within six yr but not sooner than 18 months. CR was achieved in 13 patients with FSGS recurrence and sustained in nine without subsequent relapse over a median of six and a half yr (0.6-20.7 yr). Pediatric idiopathic FSGS presenting with NS recurred in more than half of patients after transplantation. Interestingly, more rapid progression within less than 18 months did not predict recurrence. To identify high-risk patients of recurrence, an international cooperative study would be necessary.

Administration of recombinant soluble urokinase receptor per se is not sufficient to induce podocyte alterations and proteinuria in mice

Circulating levels of soluble forms of urokinase-type plasminogen activator receptor (suPAR) are generally elevated in sera from children and adults with FSGS compared with levels in healthy persons or those with other types of kidney disease. In mice lacking the gene encoding uPAR, forced increases in suPAR concentration result in FSGS-like glomerular lesions and proteinuria. However, whether overexpression of suPAR, per se, contributes to the pathogenesis of FSGS in humans remains controversial. We conducted an independent set of animal experiments in which two different and well characterized forms of recombinant suPAR produced by eukaryotic cells were administered over the short or long term to wild-type (WT) mice. In accordance with the previous study, the delivered suPARs are deposited in the glomeruli. However, such deposition of either form of suPAR in the kidney did not result in increased glomerular proteinuria or altered podocyte architecture. Our findings suggest that glomerular deposits of suPAR caused by elevated plasma levels are not sufficient to engender albuminuria.

Allogenic Aortic Graft as a Surgical Treatment of Aspergillus Aneurysm: A Case Report in a Kidney Transplant Recipient

Diagnosis and treatment of mycotic aneurysms in renal transplant recipients are extremely challenging. Choice of vascular prostheses, surgical techniques, diagnostic procedures, and medical treatment are still disputable. In this case report we present a recipient who developed an abdominal aortic aneurysm, infected with Aspergillus fumigatus, involving the major visceral arteries. In order to replace the aneurysmatic aorta and reconstruct the visceral arteries, the aneurysm was replaced surgically with a fresh AB0 compatible donor aortic graft together with donor iliac arteries. In addition to surgical treatment, this case highlights the diagnostic difficulties, modern anti-mycotic treatment, and underlying causes of this condition.

Focal segmental glomerulosclerosis: towards a better understanding for the practicing nephrologist

Focal and segmental glomerulosclerosis (FSGS) is a common histopathological lesion that can represent a primary podocytopathy, or occur as an adaptive phenomenon consequent to nephron mass reduction, a scar from a healing vasculitic lesion, direct drug toxicity or viral infection among other secondary causes. Thus, the presence of an FSGS lesion in a renal biopsy does not confer a disease diagnosis, but rather represents the beginning of an exploratory process, hopefully leading ultimately to identification of a specific etiology and its appropriate treatment. We define primary FSGS as a 'primary' podocytopathy characterized clinically by the presence of nephrotic syndrome in a patient with an FSGS lesion on light microscopy and widespread foot process effacement on electron microscopy (EM). Secondary FSGS is commonly characterized by the absence of nephrotic syndrome and the presence of segmental foot process effacement on EM. Failure to accurately differentiate between the primary and secondary forms of FSGS has resulted in many patients undergoing unnecessary immunosuppressive treatment. Here, we review some key points that may assist the practicing nephrologist to distinguish between primary and secondary FSGS.

Immunopathogenesis of idiopathic nephrotic syndrome with relapse

Idiopathic change nephrotic syndrome (INS), the most frequent glomerular disease in children and young adults, is characterized by heavy proteinuria and a relapsing remitting course. Although the mechanisms underlying the pathophysiology of proteinuria remain unclear, clinical and experimental observations suggest that lymphocyte and podocyte disturbances are two sides of the disease. The current hypothesis suggests that immune cells release a putative factor, which alters podocyte function resulting in nephrotic proteinuria. Besides T-cell abnormalities, recent evidence of B-cell depletion efficacy in sustained remissions added a new challenge in understanding the immunological mechanisms of INS. In this review, we discuss recent insights related to podocyte disorders occurring in INS and their relevance in human diseases.

Issues in solid-organ transplantation in children: translational research from bench to bedside

In this review, we identify important challenges facing physicians responsible for renal and cardiac transplantation in children based on a review of the contemporary medical literature. Regarding pediatric renal transplantation, we discuss the challenge of antibody-mediated rejection, focusing on both acute and chronic antibody-mediated rejection. We review new diagnostic approaches to antibody-mediated rejection, such as panel-reactive antibodies, donor-specific cross-matching, antibody assays, risk assessment and diagnosis of antibody-mediated rejection, the pathology of antibody-mediated rejection, the issue of ABO incompatibility in renal transplantation, new therapies for antibody-mediated rejection, inhibiting of residual antibodies, the suppression or depletion of B-cells, genetic approaches to treating acute antibody-mediated rejection, and identifying future translational research directions in kidney transplantation in children. Regarding pediatric cardiac transplantation, we discuss the mechanisms of cardiac transplant rejection, including the role of endomyocardial biopsy in detecting graft rejection and the role of biomarkers in detecting cardiac graft rejection, including biomarkers of inflammation, cardiomyocyte injury, or stress. We review cardiac allograft vasculopathy. We also address the role of genetic analyses, including genome-wide association studies, gene expression profiling using entities such as AlloMap®, and adenosine triphosphate release as a measure of immune function using the Cylex® ImmuKnow™ cell function assay. Finally, we identify future translational research directions in heart transplantation in children.