The actin cytoskeleton of kidney podocytes is a direct target of the antiproteinuric effect of cyclosporine A

Spectrum of Alport syndrome in an Indian cohort

BACKGROUND

Next-generation sequencing has enabled non-invasive diagnosis of type IV collagen disease in clinical settings other than the typical presentation of Alport syndrome (AS).

METHODS

We reviewed the clinical and histological records of children diagnosed with Alport syndrome based on next-generation sequencing. Variants on clinical exome sequencing were categorized using ACMG 2015 criteria.

RESULTS

During 2015-2023, we found 43 patients (34 boys) with 39 variants in COL4A5 (n = 27), COL4A4 (n = 7), and COL4A3 (n = 5). Thirty, 8, and 5 patients had X-linked, autosomal recessive, and autosomal dominant disease, respectively. The median (IQR) age and eGFR at diagnosis were 10 (7-13) years and 100.1 (59-140) ml/min/1.73 m2, respectively. Fifteen patients were initially diagnosed with steroid-resistant nephrotic syndrome. Alport syndrome was suspected in these patients due to persistent microscopic hematuria, eGFR < 90 ml/min/1.73 m2, characteristic histology, and/or non-response to immunosuppression. Of 26 patients who underwent kidney biopsy, light microscopy revealed focal segmental glomerulosclerosis, minimal change disease, and mesangial proliferative glomerulonephritis in 9, 9, and 8 patients, respectively. Electron microscopy (n = 18) showed characteristic glomerular basement membrane changes and/or foot process effacement in 12 and 16 cases, respectively. Twenty-one patients (48.8%) had high-frequency sensorineural hearing loss, while two had lenticonus. Twelve patients progressed to chronic kidney disease stages 4-5. Median survival (IQR) with eGFR > 30 ml/min/1.73 m2 was 15.6 (13-18) years.

CONCLUSIONS

The phenotype of Alport syndrome varies from asymptomatic urinary abnormalities to hematuria, proteinuria and/or low eGFR, and steroid-resistant nephrotic syndrome. Adverse outcomes are common, especially in boys with X-linked disease.

Advancing the clinical assessment of glomerular podocyte pathology in kidney biopsies via super-resolution microscopy and angiopoietin-like 4 staining

Rationale: The tertiary structure of normal podocytes prevents protein from leaking into the urine. However, observing the complexity of podocytes is challenging because of the scale differences in their three-dimensional structure and the close proximity between neighboring cells in space. In this study, we explored podocyte-secreted angiopoietin-like 4 (ANGPTL4) as a potential morphological marker via super-resolution microscopy (SRM). Methods and Results: Specimens from patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and membranous nephropathy (MN), along with normal controls, were analyzed via immunofluorescence and immunohistochemistry to determine the expression and localization of ANGPTL4, confirming its extensive presence in podocytes across both healthy and diseased conditions. Immunoelectron microscopy revealed that ANGPTL4 is distributed throughout the podocyte cell body, primary processes, and foot processes. Compared with conventional podocyte markers such as nephrin and synaptopodin, ANGPTL4 excels in depicting the three-dimensional structure of podocytes via SRM imaging. We then refined a protocol using tyramide signal amplification staining and confocal microscopy to uniformly enhance podocyte fluorescence, facilitating the clinical assessment of biopsies. In patients diagnosed with MCD and FSGS, measurements of slit diaphragm density, primary process width, and foot process width were taken after further co-staining with nephrin to identify patterns of podocyte morphological alterations. Distinctive patterns of foot process effacement were identified in MCD and FSGS patients, with FSGS patients showing more pronounced podocyte injury. Conclusions: ANGPTL4 serves as a reliable morphological marker for podocyte analysis, offering enhanced visualization of their three-dimensional structure and facilitating the identification of distinct pathological changes in nephrotic syndrome patients.

Traditional, alternative, and emerging therapeutics for focal segmental glomerulosclerosis

INTRODUCTION

Segmental focal glomerulosclerosis is a histological lesion characterized by podocyte damage. It may be a primary disease linked to an unknown circulating factor, secondary to viral infections, drug toxicity, or a disadaptive response to the loss of nephrons, or it may depend on gene mutations or have an indeterminate cause. The treatment of the primary form involves immunosuppressors. Additional pharmacotherapies for residual proteinuria are used, and emerging therapies are being studied to target other pathological pathways.

AREAS COVERED

This paper covers the treatment of FSGS, focusing on traditional and emerging therapeutic strategies. It is based on the KDIGO 2021 guidelines and supplemented by a literature search conducted on PubMed.

EXPERT OPINION

Treating FSGS is challenging due to its heterogeneity. Immunosuppression is adequate for primary FSGS but harmful in genetic or secondary forms. Key strategies include targeting the underlying cause and using agents that affect renal hemodynamics. Antifibrotic drugs can help slow kidney damage by addressing chronic inflammation and fibrosis. Alongside pharmacological treatments, managing blood pressure and restricting dietary salt are crucial. Finally, personalized treatment requires stratifying patients based on clinical, genetic, and histological data to improve clinical trial design and outcomes.

The Role of Podocytes in Lupus Pathology

PURPOSE OF REVIEW

Kidney injury due to lupus nephritis (LN) is a severe and sometimes life-threatening sequela of systemic lupus erythematosus. Autoimmune injury to podocytes has been increasingly demonstrated to be a key driver of LN-related kidney injury because these cells play key roles in glomerular filtration barrier homeostasis. Irreparable podocyte injury impairs these processes and can lead to proteinuria, which is an indicator of poor prognosis in LN. This review highlights recent advances in our understanding of the involvement of podocytes in the pathogenesis of LN and discusses new podocyte-targeted therapeutic strategies.

RECENT FINDINGS

Podocytes play a key role in glomerular filtration barrier homeostasis, both by helping to secrete and organize the glomerular basement membrane and by the formation of a glomerular slit diaphragm between adjacent cells. Recent studies revealed the involvement of abnormal calcium signaling, dysregulation of actin-related proteins, and mitotic catastrophe in LN progression. In addition, podocytes express many molecules related to the innate and adaptive immune responses. IgG from patients with LN induces direct injury of podocytes, inflammasome, and interactions with immune cells which have been shown to promote the development of LN. Our understanding of the role of podocytes in the pathogenesis of LN has been improved. Recent studies have shed light on potential therapeutic strategies targeting podocytes to control kidney injury.

Tacrolimus to belatacept conversion in proteinuric kidney transplant recipients

Background

Proteinuria is associated with worse allograft outcomes in kidney transplant recipients (KTRs) and treatment strategies are limited. We examined the outcomes of calcineurin inhibitor (CNI) to belatacept conversion in proteinuric KTRs.

Methods

In a pilot phase II single-arm multicenter prospective trial, we recruited adult KTRs >6 months post-kidney transplantation with an estimated glomerular filtration rate (eGFR) ≥30 ml/min/1.73m2 and proteinuria >1 g/day. Patients were converted from CNI to belatacept. The primary outcome was a 25% reduction in proteinuria at 12 months.

Results

A total of 15 KTRs were recruited who had pre-conversion median (interquartile range) proteinuria of 1.8 (IQR 1.4 - 3.5) g/g and estimated glomerular filtration rate (eGFR) of 48 (IQR 32 - 52.5) ml/min/1.73m2. At 12 months post-conversion, median proteinuria was 1.4 (IQR 0.4 - 2.2) g/g (P = 0.068) and eGFR was maintained at 43 (34 - 54.5) ml/min/1.73m2. The primary outcome of at least a 25% reduction in proteinuria occurred in 53% (8/15) at 12 months. Abbreviated IBOX scores predicting 7-year graft survival were also stable at 1-year post-conversion compared to baseline. At extended follow-up at 5 years, both proteinuria and eGFR remained stable at 0.69 (0.24 - 2.15) g/g and 39 (31 - 57) ml/min/1.73m2, respectively.

Conclusions

CNI to belatacept conversion was associated with preserved allograft function in KTRs with significant proteinuria. These findings need to be confirmed in a larger randomized clinical trial.

Clinical trial registration

https://clinicaltrials.gov/, identifier NCT0232740.

Effect of tacrolimus with mycophenolate mofetil or cyclophosphamide on the renal response in systemic lupus erythematosus patients

OBJECTIVE

This study aimed to determine the therapeutic efficacy of tacrolimus (TAC) with mycophenolate mofetil (MMF) or cyclophosphamide (CYC) on the renal response in systemic lupus erythematosus (SLE) patients.

METHODS

A retrospective cohort study based on medical data was conducted among SLE patients who took at least one of the following medicines in 2010-2021: TAC, MMF and CYC. The odds ratio (OR) and 95% confidence interval (CI) were calculated, and the synergistic interaction was estimated using logistic regression models.

RESULTS

Among 793 SLE patients, 27.9% patients (221 cases) achieved CR after at least 3 months. The TAC use was positively associated with CR with an adjusted OR (95% CI) of 2.82 (1.89, 4.22) overall and in subgroups of SLE patients with SLEDAI scores > 12, moderate or severe urinary protein and comorbidities. The dose-response effect on CR was also observed at TAC doses greater than 4 mg/d and more than 180 days, with adjusted ORs (95% CIs) of 5.65 (2.35, 13.55) and 3.60 (2.02, 6.41), respectively. Moreover, the combined effect of TAC with MMF or CYC was better than that of monotherapy, there was significant synergistic interactions with adjusted ORs (95% CIs) of 2.43 (1.20, 4.92) and 3.14 (1.49, 6.64), respectively, and similar results were observed for the combination of different doses of TAC with MMF or CYC.

CONCLUSION

TAC can effectively alleviate the condition of patients with SLE and may interact with MMF or CYC, which suggests that the combination therapy of TAC with MMF or CYC may produce greater benefits for patients with SLE.

TRIAL REGISTRATION

This is a purely observational study that does not require registration.

A multicenter study investigating the genetic analysis of childhood steroid-resistant nephrotic syndrome: Variants in COL4A5 may not be coincidental

This study aimed to discuss the pathogenic hereditary factors of children with steroid-resistant nephrotic syndrome (SRNS) in Guangxi, China. We recruited 89 patients with SRNS or infantile NS from five major pediatric nephrology centers in Guangxi, and conducted a retrospective analysis of clinical data. Whole-exome sequencing analysis was also performed on all patients. The risk of progression to chronic kidney disease (CKD) was assessed using the Kaplan-Meier method and Cox proportional hazards model. The study included 69 male and 20 female participants from 86 distinct families, with the median age of disease onset being 48 months (interquartile range: 24-93). Overall, 24.7% had a family history of SRNS, whereas 13.5% exhibited extra-kidney manifestations. We identified disease-causing variants in 24.7% (22/89) of patients across eight screened genes. The most frequently detected variant was found in COL4A5, followed by NPHS2 (5.6%), NPHS1 (2.2%), PAX2 (2.2%), WT1 (1.1%), LMX1B (1.1%), NUP105 (1.1%), and COL4A6 (1.1%). Twelve of the 26 pathogenic variants were determined to be de novo. Based on gene detection results, pathogenic variants were categorized into two groups: identified and unidentified variants. The identified variant group demonstrated a significant association with positive family history, steroid resistant-style, and response to immune therapy (P<0.001). Patients with the identified genetic variant were approximately ten times more likely to develop CKD (P<0.001) than those in the unidentified group at the last follow-up. Kidney biopsy was performed on 66 patients, and minimal change disease was the most prevalent histopathological diagnosis (29 cases; 32.6%). These findings suggest that children diagnosed with SRNS exhibit a diverse range of genetic alterations. We identified the COL4A5 variant as the predominant genetic abnormality and a low frequency of NPHS1 gene involvement in these children. Gene variants may serve as an independent predictor for SRNS progression to CKD.

Detailed Pathophysiology of Minimal Change Disease: Insights into Podocyte Dysfunction, Immune Dysregulation, and Genetic Susceptibility

Minimal Change Disease (MCD) is a predominant cause of idiopathic nephrotic syndrome in the pediatric population, yet presents significant clinical challenges due to its frequent relapses and steroid resistance. Despite its relatively benign histological appearance, MCD is characterized by severe proteinuria, hypoalbuminemia, and edema, which may affect patient outcomes. Current treatment strategies primarily rely on corticosteroids, which are effective in inducing remission but are associated with high relapse rates, steroid resistance, and numerous long-term side effects, underscoring the need for more targeted and effective therapeutic approaches. This narrative review synthesizes current knowledge on the pathophysiological mechanisms underlying MCD, focusing on the following three critical areas: podocyte dysfunction, immune dysregulation, and genetic susceptibility. Podocyte dysfunction, particularly involving alterations in nephrin, plays a central role in the breakdown of the glomerular filtration barrier, leading to the characteristic proteinuria observed in MCD. Immune dysregulation, including the presence of autoantibodies against nephrin and other podocyte components, exacerbates podocyte injury and contributes to disease progression, suggesting an autoimmune component to the disease. Genetic factors, particularly mutations in the NPHS1 and NPHS2 genes, have been identified as significant contributors to disease susceptibility, influencing the variability in treatment response and overall disease severity. Understanding these mechanisms is crucial for developing targeted therapies that address the underlying causes of MCD rather than merely managing its symptoms. This review highlights the need for further research into these pathophysiological processes to pave the way for more personalized and effective treatment strategies, ultimately improving patient outcomes and reducing reliance on corticosteroids.

The association between serum complement 4 and relapse of primary membranous nephropathy: a multicenter retrospective cohort study

Background

Relapse after initial remission reduces renal survival in patients with primary membranous nephropathy (PMN). In this study, we aim to identify risk factors of relapse in PMN and construct a model to identify patients at high risk of relapse early.

Methods

We conducted a multi-center retrospective study using the China Renal Data System database, which includes data from 24 urban academic centers across China. A prediction model based on the Cox proportional hazards model was derived in the derivation group and validated in the validation group.

Result

515 patients with biopsy-proven PMN achieving initial remission were enrolled. 32.62% of patients subsequently relapsed during a median of 6.08 months. Lower serum albumin (Alb) (per 1 g/L decrease, hazard ratio [HR] =1.48, 95% confidence interval [CI] 1.29-1.78, p < 0.001), lower estimated glomerular filtration rate (eGFR) (per 10 mL/min/1.73m2 decrease, HR =1.14, 95% CI 0.97-1.49, p < 0.001), higher serum complement 4 (C4) (per 0.1 g/L increase, HR =1.89, 95% CI 1.32-3.22, p = 0.012), partial remission (PR) (HR =2.28, 95%CI 1.74-4.04, p < 0.001), and treatment with calcineurin inhibitors (CINs) (HR =1.33, 95%CI 1.04-1.64, p < 0.001) at the time of remission were risk factors for relapse. C-statistic, time-dependent areas under the receiver operating characteristic curve, and calibration plots confirmed that the model had excellent discrimination and calibration in predicting PMN relapse. The anti-phospholipase A2 receptor antibody (aPLA2Rab) titers and pathologic features did not substantially improve the model.

Conclusion

Our study confirms the well-known low Alb and eGFR, PR, and treatment of CNIs at the time of remission as risk factors for PMN relapse, but aPLA2Rab and pathologic features may not predict relapse. In addition, it is the first study to show serum C4 is associated with PMN relapse. We suggest that complement-targeted therapies may be a potential therapy to prevent PMN relapse.

Comparison of a voclosporin-based triple immunosuppressive therapy to high-dose glucocorticoid-based immunosuppressive therapy: a propensity analysis of the AURA-LV and AURORA 1 studies and ALMS

INTRODUCTION

High-dose glucocorticoid (GC)-based dual immunosuppressive treatment regimens are still frequently used in active lupus nephritis (LN) despite their known association with dose-dependent toxicities and incomplete efficacy. We hypothesised that the addition of voclosporin to low-dose GCs and mycophenolate mofetil (MMF) would reduce exposure to the toxicities of high-dose GC-based dual immunosuppressive therapy regimens, resulting in an improved safety profile without compromising efficacy.

METHODS

Propensity score matching generated two groups of matched participants from the voclosporin arms (in combination with MMF (2 g/day) and low-dose GCs) of the Phase 2 AURA-LV and Phase 3 AURORA 1 studies and the MMF (3 g/day) and intravenous cyclophosphamide (IVC) arms (both in combination with high-dose GCs) of the Aspreva Lupus Management Study (ALMS) induction study. Safety and efficacy outcomes were assessed over 6 months.

RESULTS

There were 179 matched participants identified between the AURA-LV/AURORA 1 studies and ALMS. The overall incidence of adverse events (AEs) was higher in IVC- and MMF-treated participants of ALMS; more voclosporin-treated participants reported AEs by preferred term of glomerular filtration rate decreased, hypertension and anaemia. The incidence of serious AEs was similar across treatments. There were four (2.2%) deaths in IVC- and MMF-treated participants of ALMS compared with seven (3.9%) deaths in voclosporin-treated participants. Significantly more voclosporin-treated participants achieved a ≥25% reduction in urine protein creatinine ratio (UPCR) from baseline at 3 months and ≥50% reduction in UPCR from baseline at 6 months.

CONCLUSIONS

Compared with the high-dose GC-based regimens used in ALMS, voclosporin-based triple immunosuppressive therapy resulted in fewer AEs overall and greater and earlier reductions in proteinuria over the first 6 months of treatment. These data reinforce the feasibility of using low doses of GCs and MMF to treat LN when combined with voclosporin as a third agent.

Synaptopodin: a key regulator of Hebbian plasticity

Synaptopodin, an actin-associated protein found in a subset of dendritic spines in telencephalic neurons, has been described to influence both functional and morphological plasticity under various plasticity paradigms. Synaptopodin is necessary and sufficient for the formation of the spine apparatus, stacks of smooth endoplasmic reticulum cisternae. The spine apparatus is a calcium store that locally regulates calcium dynamics in response to different patterns of activity and is also thought to be a site for local protein synthesis. Synaptopodin is present in ~30% of telencephalic large dendritic spines in vivo and in vitro highlighting the heterogeneous microanatomy and molecular architecture of dendritic spines, an important but not well understood aspect of neuroplasticity. In recent years, it has become increasingly clear that synaptopodin is a formidable regulator of multiple mechanisms essential for learning and memory. In fact, synaptopodin appears to be the decisive factor that determines whether plasticity can occur, acting as a key regulator for synaptic changes. In this review, we summarize the current understanding of synaptopodin's role in various forms of Hebbian synaptic plasticity.

Mechanisms of podocyte injury in genetic kidney disease

Glomerular diseases are a leading cause of chronic kidney disease worldwide. Both acquired and hereditary glomerulopathies frequently share a common final disease mechanism: disruption of the glomerular filtration barrier, podocyte injury, and ultimately podocyte death and detachment. Over 70 monogenic causes of proteinuric kidney disease have been identified, and most of these genes are highly expressed in podocytes, regulating key processes such as maintenance of the slit diaphragm, regulation of actin cytoskeleton remodeling, and modulation of downstream transcriptional pathways. Collectively, these are increasingly being referred to as hereditary "podocytopathies," in which podocyte injury is the central feature driving proteinuria and kidney dysfunction. In this review, we provide an overview of the monogenic podocytopathies and discuss the molecular mechanisms by which single-gene defects lead to podocyte injury and ultimately glomerulosclerosis. We review how advances in genomic technology and a better understanding of the cell biological basis of disease have led to the development of more targeted and personalized therapeutic strategies, including an overview of small molecule and gene therapy approaches.

Effects of immunosuppressive therapy on renal prognosis in primary membranous nephropathy

BACKGROUND

Immunosuppressive therapy plays a crucial role in treating membranous nephropathy, with previous studies highlighting its benefits for patients with primary membranous nephropathy (PMN). Guidelines suggest that the management of membranous nephropathy should be tailored to individual risk levels. However, there is a lack of real-world studies examining the effects of immunosuppressive therapy on renal outcomes in PMN patients. This study aimed to investigate the relationship between immunosuppressive therapy and renal prognosis in PMN patients.

METHODS

This was a real-world retrospective study including patients diagnosed with PMN in Shenzhen Second People's Hospital and Hechi People's Hospital. Univariate and multivariate Cox regression analysis and Kaplan-Meier survival analysis were used.

RESULTS

After propensity score-matching, 464 PMN patients were included and they were assigned to conservative and immunosuppressive group in a 1:1 ratio. Immunosuppressive therapy was the protective factor of renal composite outcome (HR = 0.65, p < 0.01). Separately, the effect was significant in moderate- and high-risk but not in low-risk patients. Key influencing factors including age, blood pressure, albumin and total cholesterol levels, with slight differences among patients at different risk.

CONCLUSIONS

This study demonstrates the efficacy of immunosuppressive therapy in non-low-risk PMN patients. The key factors affecting renal prognosis in patients with different risk levels are emphasized to help provide individualized treatment.

Effect of QingreHuoxue formula on Th17 cells and Tregs in mice with idiopathic membranous nephropathy

OBJECTIVES

This study aimed to evaluate the therapeutic effect of the QingreHuoxue formula on mice with Idiopathic Membranous Nephropathy (IMN) and its impact on Th17 cells and Tregs.

METHODS

A mouse model of IMN was established, and the mice were treated with traditional Chinese medicine, western medicine, or a combination of both. The efficacy and immunomodulatory effects of the QingreHuoxue formula were evaluated by examining renal pathology, urinary protein levels, peripheral blood Th17 and Treg cell counts, and comparing the expression levels of IL-17 and transforming growth factor-β1 in renal tissues.

RESULTS

Compared to the untreated IMN model group, the IMN mice treated with TCM, western medicine, or the combination showed significant improvements in proteinuria, renal pathology, peripheral T lymphocyte counts, and IL-17 expression in renal tissues. Notably, the group treated with a combination of Chinese and western medicine exhibited better outcomes than the group treated with western medicine alone.

CONCLUSIONS

The QingreHuoxue formula was effective in reducing proteinuria, modulating T cell immune function, and protecting renal tissue in mice with IMN.

Podocyte-targeted therapies - progress and future directions

Podocytes are the key target cells for injury across the spectrum of primary and secondary proteinuric kidney disorders, which account for up to 90% of cases of kidney failure worldwide. Seminal experimental and clinical studies have established a causative link between podocyte depletion and the magnitude of proteinuria in progressive glomerular disease. However, no substantial advances have been made in glomerular disease therapies, and the standard of care for podocytopathies relies on repurposed immunosuppressive drugs. The past two decades have seen a remarkable expansion in understanding of the mechanistic basis of podocyte injury, with prospects increasing for precision-based treatment approaches. Dozens of disease-causing genes with roles in the pathogenesis of clinical podocytopathies have been identified, as well as a number of putative glomerular permeability factors. These achievements, together with the identification of novel targets of podocyte injury, the development of potential approaches to harness the endogenous podocyte regenerative potential of progenitor cell populations, ongoing clinical trials of podocyte-specific pharmacological agents and the development of podocyte-directed drug delivery systems, contribute to an optimistic outlook for the future of glomerular disease therapy.

Immunology and targeted therapy in Castleman disease

INTRODUCTION

Castleman disease (CD) is a benign lymphoproliferative disease causing severe systemic inflammation. Interleukin-6 (IL-6) is a major pathogenesis of multicentric CD (MCD), but only 30-60% of patients respond to IL-6 inhibitors. Novel agents for IL-6 inhibitor-refractory cases are needed. Clinical data and samples are being collected on a large scale and the clinical, pathological, and pathogenetic aspects are being elucidated.

AREAS COVERED

The pathological and clinical classification of CD is outlined. Focusing on idiopathic MCD (iMCD), this review identifies therapeutic targets and summarizes currently recommended drugs and promising therapeutic candidates.

EXPERT OPINION

The pathogenesis of MCD has been implicated in the activation of the Janus kinase (JAK)-transcriptional signaling activator (STAT) 3 pathway and the phosphatidylinositol 3-kinase (PI3K)/Akt/mechanical target of rapamycin (mTOR) signaling pathway. iMCD-TAFRO (thrombocytopenia, anasarca, fever/elevated CRP, reticulin myelofibrosis/renal dysfunction, organ enlargement) is resistant to IL-6 inhibitors, and cyclosporine and mTOR inhibitors are sometimes effective. JAK inhibitors and mTOR inhibitors may be therapeutic agents for iMCD. Recently, we have shown that peripheral helper T (Tph) cell abnormalities are at the core of iMCD pathogenesis. Therapies targeting chemokine (C-X-C motif) ligand 13 (CXCL13) produced by Tph cells and blocking the Tph-CXCL13-B cell pathway may satisfy unmet need in refractory cases.

Calcineurin is an adaptor required for assembly of the TCR signaling complex

The serine/threonine phosphatase calcineurin is a component of the T cell receptor (TCR) signalosome, where it promotes T cell activation by dephosphorylating LckS59. Using small interfering RNA (siRNA)-mediated knockdown and CRISPR-Cas9-targeted genetic disruption of the calcineurin A chain α and β isoforms, we find that calcineurin also functions as an adaptor in TCR-signaled human T cells. Unlike inhibition of its phosphatase activity, in the absence of calcineurin A, TCR signaling results in attenuated actin rearrangement, markedly reduced TCR-Lck microcluster formation and recruitment of the adaptor RhoH, and diminished phosphorylation of critical targets downstream of Lck such as TCRζ and ZAP-70. Reconstitution of deficient T cells with either calcineurin Aα or Aβ restores TCR microcluster formation and signaling, as does reconstitution with a phosphatase-inactive Aα chain. These results assign a non-enzymatic adaptor function to calcineurin in the formation and stabilization of a functional TCR signaling complex.

Urine-derived podocytes from steroid resistant nephrotic syndrome patients as a model for renal-progenitor derived extracellular vesicles effect and drug screening

BACKGROUND

Personalized disease models are crucial for evaluating how diseased cells respond to treatments, especially in case of innovative biological therapeutics. Extracellular vesicles (EVs), nanosized vesicles released by cells for intercellular communication, have gained therapeutic interest due to their ability to reprogram target cells. We here utilized urinary podocytes obtained from children affected by steroid-resistant nephrotic syndrome with characterized genetic mutations as a model to test the therapeutic potential of EVs derived from kidney progenitor cells (nKPCs).

METHODS

EVs were isolated from nKPCs derived from the urine of a preterm neonate. Three lines of urinary podocytes obtained from nephrotic patients' urine and a line of Alport syndrome patient podocytes were characterized and used to assess albumin permeability in response to nKPC-EVs or various drugs. RNA sequencing was conducted to identify commonly modulated pathways after nKPC-EV treatment. siRNA transfection was used to demonstrate the involvement of SUMO1 and SENP2 in the modulation of permeability.

RESULTS

Treatment with the nKPC-EVs significantly reduced permeability across all the steroid-resistant patients-derived and Alport syndrome-derived podocytes. At variance, podocytes appeared unresponsive to standard pharmacological treatments, with the exception of one line, in alignment with the patient's clinical response at 48 months. By RNA sequencing, only two genes were commonly upregulated in nKPC-EV-treated genetically altered podocytes: small ubiquitin-related modifier 1 (SUMO1) and Sentrin-specific protease 2 (SENP2). SUMO1 and SENP2 downregulation increased podocyte permeability confirming the role of the SUMOylation pathway.

CONCLUSIONS

nKPCs emerge as a promising non-invasive source of EVs with potential therapeutic effects on podocytes with genetic dysfunction, through modulation of SUMOylation, an important pathway for the stability of podocyte slit diaphragm proteins. Our findings also suggest the feasibility of developing a non-invasive in vitro model for screening regenerative compounds on patient-derived podocytes.

Novel mutation patterns in children with steroid-resistant nephrotic syndrome

Background

Idiopathic nephrotic syndrome (NS) in children poses treatment challenges, with a subset developing steroid-resistant nephrotic syndrome (SRNS). Genetic factors play a role, yet data on paediatric SRNS genetics in India are scarce. We conducted a prospective study using whole-exome sequencing to explore genetic variants and their clinical correlations.

Methods

A single-centre prospective study (October 2018-April 2023) enrolled children with SRNS, undergoing renal biopsy and genetic testing per institutional protocol. Clinical, histological, and genetic data were recorded. DNA isolation and next-generation sequencing were conducted for genetic analysis. Data collection included demographics, clinical parameters, and kidney biopsy findings. Syndromic features were evaluated, with second-line immunosuppressive therapy administered. Patient and renal outcomes are presented for patients with and without genetic variants.

Results

A total of 680 paediatric NS patients were analysed, with 121 (17.8%) having SRNS and 96 consent to genetic analysis. 69 (71.9%) had early SRNS, 27 (28.1%) late. Among participants, 62 (64.58%) had reportable genetic variants. The most common were in COL4A genes, with 20 (31.7%) positive. Renal biopsy showed focal segmental glomerulosclerosis in 31/42 (74%) with variants, 16/28 (57.1%) without variants. Second-line immunosuppressions varied, with CNIs the most common. Outcomes varied, with partial or complete remission achieved in some while others progressed to ESRD.

Conclusion

The study underscores the importance of genetic analysis in paediatric SRNS, revealing variants in 65.7% of cases. COL4A variants were predominant. Variants correlated with varied renal outcomes, highlighting potential prognostic implications. These findings emphasize the value of personalized approaches and further research in managing paediatric SRNS.

Proteomic profiling of laser capture microdissection kidneys from diabetic nephropathy patients

Diabetic nephropathy (DN) remains the primary cause of end-stage renal disease (ESRD), warranting equal attention and separate analysis of glomerular, tubular, and interstitial lesions in its diagnosis and intervention. This study aims to identify the specific proteomics characteristics of DN, and assess changes in the biological processes associated with DN. 5 patients with DN and 5 healthy kidney transplant donor control individuals were selected for analysis. The proteomic characteristics of glomeruli, renal tubules, and renal interstitial tissue obtained through laser capture microscopy (LCM) were studied using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Significantly, the expression of multiple heat shock proteins (HSPs), tubulins, and heterogeneous nuclear ribonucleoproteins (hnRNPs) in glomeruli and tubules was significantly reduced. Differentially expressed proteins (DEPs) in the glomerulus showed significant enrichment in pathways related to cell junctions and cell movement, including the regulation of actin cytoskeleton and tight junction. DEPs in renal tubules were significantly enriched in glucose metabolism-related pathways, such as glucose metabolism, glycolysis/gluconeogenesis, and the citric acid cycle. Moreover, the glycolysis/gluconeogenesis pathway was a co-enrichment pathway in both DN glomeruli and tubules. Notably, ACTB emerged as the most crucial protein in the protein-protein interaction (PPI) analysis of DEPs in both glomeruli and renal tubules. In this study, we delve into the unique proteomic characteristics of each sub-region of renal tissue. This enhances our understanding of the potential pathophysiological changes in DN, particularly the potential involvement of glycolysis metabolic disorder, glomerular cytoskeleton and cell junctions. These insights are crucial for further research into the identification of disease biomarkers and the pathogenesis of DN.

The Immunosuppressive Drug LF15-0195 Acts Also on Glomerular Lesions, by a Change in Cytoskeleton Distribution in Podocyte

INTRODUCTION

Buffalo/Mna rats spontaneously develop nephrotic syndrome (NS) which recurs after renal transplantation. The immunosuppressive drug LF15-0195 can promote regression of the initial and post-transplantation nephropathy via induction of regulatory T cells. We investigate if this drug has an additional effect on the expression and localization of podocyte specific proteins.

METHODS

Buffalo/Mna kidney samples were collected before and after the occurrence of proteinuria, and after the remission of proteinuria induced by LF15-0195 treatment and compared by quantitative RT-PCR, Western blot, electron, and confocal microscopy to kidney samples of age-matched healthy rats. Cytoskeleton changes were assessed in culture by stress fibers induction by TNFα.

RESULTS

We observed, by electron microscopy, a restoration of foot process architecture in the LF15-0195-treated Buff/Mna kidneys, consistent with proteinuria remission. Nephrin, podocin, CD2AP, and α-actinin-4 mRNA levels remained low during the active disease in the Buff/Mna, in comparison with healthy rats which increase, while podocalyxin and synaptopodin transcripts were elevated before the occurrence of the disease but did not differ from healthy animals after. No difference in the mRNA and protein expression between the untreated and the LF15-0195-treated proteinuric Buff/Mna were seen for these 6 proteins. No changes were observed by confocal microscopy in the protein distribution at a cellular level, but a more homogenous distribution similar to healthy rats, was observed within the glomeruli of LF15-0195-treated rats. In addition, LF15-0195 could partially restore actin cytoskeleton of endothelial cells in TNFα-induced-cell stress experiment.

CONCLUSION

The effect of LF15-0195 treatment appears to be mediated by 2 mechanisms: an immunomodulatory effect via regulatory T cells induction, described in our previous work and which can act on immune cell involved in the disease pathogenesis, and an effect on the restoration of podocyte cytoskeleton, independent of expression levels of the proteins involved in the slit diaphragm and podocyte function, showed in this article.

Nephrotic Syndrome in a Child With NPHS2 Mutation

Steroid resistant nephrotic syndrome (SRNS) accounts for 30% of all cases of nephrotic syndrome (NS) in children and frequently leads to end stage kidney disease (ESKD). About 30% of children with SRNS demonstrate causative mutations in podocyte- associated genes. Early identification of genetic forms of SRNS is critical to avoid potentially harmful immunosuppressive therapy. A 2-year-old male patient with NS and no family history of renal disease did not respond to 4-week steroid treatment. Kidney biopsy demonstrated mesangial proliferative glomerulopathy with basement membrane dysmorphism. Tacrolimus and Lisinopril were added to therapy pending results of genetic testing. Kidney Gene panel showed a NPHS2 c.413G>A (p.Arg138Gln) homozygous pathogenic variant. This missense variant is considered a common pathogenic founder mutation in European populations. A diagnosis of autosomal-recessive form of nonsyndromic SRNS due to NPHS2 causative variant was made. Immunosuppresive therapy was stopped, Lizinopril dose was increased and weekly infusions of Albumin/furosemide were initiated to manage edema. This case demonstrates that early genetic testing in children with SRNS avoids prolonged potentially harmful immunosuppressive therapy, allows for timely genetic family counseling, and allows earlier consideration for future living related donor kidney transplantation.

Membranous nephropathy: pathogenesis and treatments

Membranous nephropathy (MN), an autoimmune disease, can manifest at any age and is among the most common causes of nephrotic syndrome in adults. In 80% of cases, the specific etiology of MN remains unknown, while the remaining cases are linked to drug use or underlying conditions like systemic lupus erythematosus, hepatitis B virus, or malignancy. Although about one-third of patients may achieve spontaneous complete or partial remission with conservative management, another third face an elevated risk of disease progression, potentially leading to end-stage renal disease within 10 years. The identification of phospholipase A2 receptor as the primary target antigen in MN has brought about a significant shift in disease management and monitoring. This review explores recent advancements in the pathophysiology of MN, encompassing pathogenesis, clinical presentations, diagnostic criteria, treatment options, and prognosis, with a focus on emerging developments in pathogenesis and therapeutic strategies aimed at halting disease progression. By synthesizing the latest research findings and clinical insights, this review seeks to contribute to the ongoing efforts to enhance our understanding and management of this challenging autoimmune disorder.

Chiral Supramolecular Nanofibers Regulated Tumor-Derived Exosomes Secretion for Constructing an Anti-Tumor Extracellular Microenvironment

Tumor-derived exosomes (TDEs) induced extracellular microenvironment has recently been validated to be critical for tumor progression and metastasis, however, remodeling it for oncotherapy still remains a major challenge due to difficulty in regulation of TDEs secretion. Herein, the supramolecular chiral nanofibers, composed of L/D-phenylalanine derivates (L/D-Phe) and linear hyaluronic acid (HA), are successfully employed to construct TDEs induced anti-tumor extracellular microenvironment. The left-handed L-Phe @HA nanofibers significantly inhibit TDEs secretion into extracellular microenvironment, which results in suppression of tumor proliferation and metastasis in vitro and vivo. Biological assays and theoretical modeling reveal that these results are mainly attributed to strong adsorption of the key exosomes transporters (Ras-related protein Rab-27A and synaptosome-associated protein 23) on left-handed L-Phe @HA nanofibers via enhanced stereoselective interaction, leading to degradation and phosphorylated dropping of exosomes transporters. Subsequently, transfer function of exosomes transporters is limited, which causes remarkable inhibition of TDEs secretion. These findings provide a promising novel insight of chiral functional materials to establish an anti-tumor extracellular microenvironment via regulation of TDEs secretion.

Inhibition of the glucocorticoid receptor attenuates proteinuric kidney diseases in multiple species

BACKGROUND

Glucocorticoids are the treatment of choice for proteinuric patients with minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS). Immunosuppressive as well as direct effects on podocytes are believed to mediate their actions. In this study, we analyzed the anti-proteinuric effects of inhibition of the glucocorticoid receptor (GR) in glomerular epithelial cells, including podocytes.

METHODS

We employed genetic and pharmacological approaches to inhibit the GR. Genetically, we used Pax8-Cre/GRfl/fl mice to specifically inactivate the GR in kidney epithelial cells. Pharmacologically, we utilized a glucocorticoid antagonist called mifepristone.

RESULTS

Genetic inactivation of GR, specifically in kidney epithelial cells, using Pax8-Cre/GRfl/fl mice, ameliorated proteinuria following protein overload. We further tested the effects of pharmacological GR inhibition in three models and species: the puromycin aminonucleoside-induced nephrosis model in rats, the protein overload model in mice and the inducible transgenic NTR/MTZ zebrafish larvae with specific and reversible podocyte injury. In all three models, both pharmacological GR activation and inhibition consistently and significantly ameliorated proteinuria. Additionally, we translated our findings to humans, where three nephrotic adult patients with MCD or primary FSGS with contraindications or insufficient responses to corticosteroids were treated with mifepristone. This treatment resulted in a clinically relevant reduction of proteinuria.

CONCLUSIONS

Thus, across multiple species and proteinuria models, both genetic and pharmacological GR inhibition was at least as effective as pronounced GR activation. While the mechanism remains perplexing, GR inhibition may be a novel and targeted therapeutic approach to treat glomerular proteinuria potentially bypassing adverse actions of steroids.

Role of the β2-adrenergic receptor in podocyte injury and recovery

BACKGROUND

Podocytes have a remarkable ability to recover from injury; however, little is known about the recovery mechanisms involved in this process. We recently showed that formoterol, a long-acting β2-adrenergic receptor (β2-AR) agonist, induced mitochondrial biogenesis (MB) in podocytes and led to renoprotection in mice. However, it is not clear whether this effect was mediated by formoterol acting through the β2-AR or if it occurred through "off-target" effects.

METHODS

We genetically deleted the β2-AR specifically in murine podocytes and used these mice to determine whether formoterol acting through the podocyte β2-AR alone is sufficient for recovery of renal filtration function following injury. The podocyte-specific β2-AR knockout mice (β2-ARfl/fl/PodCre) were generated by crossing β2-AR floxed mice with podocin Cre (B6.Cg-Tg(NPHS2-cre)295Lbh/J) mice. These mice were then subjected to both acute and chronic glomerular injury using nephrotoxic serum (NTS) and adriamycin (ADR), respectively. The extent of injury was evaluated by measuring albuminuria and histological and immunostaining analysis of the murine kidney sections.

RESULTS

A similar level of injury was observed in β2-AR knockout and control mice; however, the β2-ARfl/fl/PodCre mice failed to recover in response to formoterol. Functional evaluation of the β2-ARfl/fl/PodCre mice following injury plus formoterol showed similar albuminuria and glomerular injury to control mice that were not treated with formoterol.

CONCLUSIONS

These results indicate that the podocyte β2-AR is a critical component of the recovery mechanism and may serve as a novel therapeutic target for treating podocytopathies.

A Comprehensive and Practical Approach to the Management of Lupus Nephritis in the Current Era

Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) and is one of the leading causes of morbidity and mortality in patients with SLE. It is estimated that up to 60% of individuals with SLE will develop LN, which can manifest at any stage of a patient's life; however, it commonly emerges early in the course of SLE and tends to exhibit a more aggressive phenotype in men compared to women. Black and Hispanic patients are more likely to progress to kidney failure than white patients. LN is characterized by kidney inflammation and chronic parenchymal damage, leading to impaired kidney function and potential progression to kidney failure. This article provides a comprehensive overview of the epidemiology, pathogenesis, clinical presentation, diagnosis, and management of LN, highlighting the importance of early recognition and treatment of LN to prevent progressive, irreversible kidney damage and improve patient outcomes. Additionally, the article discusses current and emerging therapies for LN, including traditional immunosuppressive agents, biological agents, and novel therapies targeting specific pathways involved in LN pathogenesis, to provide a practical guide for clinicians in properly diagnosing LN and determining a patient-centered treatment plan.

C5a-C5aR1 axis controls mitochondrial fission to promote podocyte injury in lupus nephritis

Podocytes are essential to maintaining the integrity of the glomerular filtration barrier, but they are frequently affected in lupus nephritis (LN). Here, we show that the significant upregulation of Drp1S616 phosphorylation in podocytes promotes mitochondrial fission, leading to mitochondrial dysfunction and podocyte injury in LN. Inhibition or knockdown of Drp1 promotes mitochondrial fusion and protects podocytes from injury induced by LN serum. In vivo, pharmacological inhibition of Drp1 reduces the phosphorylation of Drp1S616 in podocytes in lupus-prone mice. Podocyte injury is reversed when Drp1 is inhibited, resulting in the alleviation of proteinuria. Mechanistically, complement component C5a (C5a) upregulates the phosphorylation of Drp1S616 and promotes mitochondrial fission in podocytes. Moreover, the expression of C5a receptor 1 (C5aR1) is notably upregulated in podocytes in LN. C5a-C5aR1 axis-controlled phosphorylation of Drp1S616 and mitochondrial fission are substantially suppressed when C5aR1 is knocked down by siRNA. Moreover, lupus-prone mice treated with C5aR inhibitor show reduced phosphorylation of Drp1S616 in podocytes, resulting in significantly less podocyte damage. Together, this study uncovers a novel mechanism by which the C5a-C5aR1 axis promotes podocyte injury by enhancing Drp1-mediated mitochondrial fission, which could have significant implications for the treatment of LN.

Proteomics-Based Identification of Potential Therapeutic Targets of Artesunate in a Lupus Nephritis MRL/lpr Mouse Model

This study aimed to identify potential therapeutic targets of artesunate in an MRL/lpr lupus nephritis mouse model by quantitative proteomics. We detected serum autoimmune markers and proteinuria in 40 female mice that were divided into 4 groups (n = 10): normal C57BL/6 control group; untreated MRL/lpr lupus; 9 mg/kg/day prednisone positive control MRL/lpr lupus; and 15 mg/kg/day artesunate-treated MRL/lpr lupus groups. Renal pathology in the untreated MRL/lpr lupus and artesunate groups was examined by Periodic acid-Schiff (PAS) staining. Artesunate treatment in lupus mice decreased serum autoantibody levels and proteinuria while alleviating lupus nephritis pathology. Through tandem mass tag-tandem mass spectrometry (TMT-MS/MS) analyses, differentially expressed proteins were identified in the artesunate group, and subsequent functional prediction suggested associations with antigen presentation, apoptosis, and immune regulation. Data are available via ProteomeXchange with the identifier PXD046815. Parallel reaction monitoring (PRM) analysis of the top 19 selected proteins confirmed the TMT-MS/MS results. Immunohistochemistry, immunofluorescence, and Western blotting of an enriched protein from PRM analysis, cathepsin S, linked to antigen presentation, highlighted its upregulation in the untreated MRL/lpr lupus group and downregulation following artesunate treatment. This study suggests that artesunate holds potential as a therapeutic agent for lupus nephritis, with cathepsin S identified as a potential target.

The Critical Role of the Shroom Family Proteins in Morphogenesis, Organogenesis and Disease

The Shroom (Shrm) family of actin-binding proteins has a unique and highly conserved Apx/Shrm Domain 2 (ASD2) motif. Shroom protein directs the subcellular localization of Rho-associated kinase (ROCK), which remodels the actomyosin cytoskeleton and changes cellular morphology via its ability to phosphorylate and activate non-muscle myosin II. Therefore, the Shrm-ROCK complex is critical for the cellular shape and the development of many tissues, including the neural tube, eye, intestines, heart, and vasculature system. Importantly, the structure and expression of Shrm proteins are also associated with neural tube defects, chronic kidney disease, metastasis of carcinoma, and X-link mental retardation. Therefore, a better understanding of Shrm-mediated signaling transduction pathways is essential for the development of new therapeutic strategies to minimize damage resulting in abnormal Shrm proteins. This paper provides a comprehensive overview of the various Shrm proteins and their roles in morphogenesis and disease.

Urine-derived podocytes from steroid resistant nephrotic syndrome patients as a model for renal-progenitor derived extracellular vesicles effect and drug screening

Background

Personalized disease models are crucial for assessing the specific response of diseased cells to drugs, particularly novel biological therapeutics. Extracellular vesicles (EVs), nanosized vesicles released by cells for intercellular communication, have gained therapeutic interest due to their ability to reprogram target cells. We here utilized urinary podocytes obtained from children affected by steroid-resistant nephrotic syndrome with characterized genetic mutations as a model to test the therapeutic potential of EVs derived from kidney progenitor cells.

Methods

EVs were isolated from kidney progenitor cells (nKPCs) derived from the urine of a preterm neonate. Three lines of urinary podocytes obtained from nephrotic patients' urine and a line of Alport patient podocytes were characterized and used to assess albumin permeability in response to various drugs or to nKPC-EVs. RNA sequencing was conducted to identify commonly modulated pathways.

Results

Podocytes appeared unresponsive to pharmacological treatments, except for a podocyte line demonstrating responsiveness, in alignment with the patient's clinical response at 48 months. At variance, treatment with the nKPC-EVs was able to significantly reduce permeability in all the steroid-resistant patients-derived podocytes as well as in the line of Alport-derived podocytes. RNA sequencing of nKPC-EV-treated podocytes revealed the common upregulation of two genes (small ubiquitin-related modifier 1 (SUMO1) and Sentrin-specific protease 2 (SENP2)) involved in the SUMOylation pathway, a process recently demonstrated to play a role in slit diaphragm stabilization. Gene ontology analysis on podocyte expression profile highlighted cell-to-cell adhesion as the primary upregulated biological activity in treated podocytes.

Conclusions

nKPCs emerge as a promising non-invasive source of EVs with potential therapeutic effects on podocyte dysfunction. Furthermore, our findings suggest the possibility of establishing a non-invasive in vitro model for screening regenerative compounds on patient-derived podocytes.

Klotho Stabilizes the Podocyte Actin Cytoskeleton in Idiopathic Membranous Nephropathy through Regulating the TRPC6/CatL Pathway

INTRODUCTION

The aim of this study was to explore the renoprotective effects of Klotho on podocyte injury mediated by complement activation and autoantibodies in idiopathic membranous nephropathy (IMN).

METHODS

Rat passive Heymann nephritis (PHN) was induced as an IMN model. Urine protein levels, serum biochemistry, kidney histology, and podocyte marker levels were assessed. In vitro, sublytic podocyte injury was induced by C5b-9. The expression of Klotho, transient receptor potential channel 6 (TRPC6), and cathepsin L (CatL); its substrate synaptopodin; and the intracellular Ca2+ concentration were detected via immunofluorescence. RhoA/ROCK pathway activity was measured by an activity quantitative detection kit, and the protein expression of phosphorylated-LIMK1 (p-LIMK1) and p-cofilin in podocytes was detected via Western blotting. Klotho knockdown and overexpression were performed to evaluate its role in regulating the TRPC6/CatL pathway.

RESULTS

PHN rats exhibited proteinuria, podocyte foot process effacement, decreased Klotho and Synaptopodin levels, and increased TRPC6 and CatL expression. The RhoA/ROCK pathway was activated by the increased phosphorylation of LIMK1 and cofilin. Similar changes were observed in C5b-9-injured podocytes. Klotho knockdown exacerbated podocyte injury, while Klotho overexpression partially ameliorated podocyte injury.

CONCLUSION

Klotho may protect against podocyte injury in IMN patients by inhibiting the TRPC6/CatL pathway. Klotho is a potential target for reducing proteinuria in IMN patients.

Modeled microgravity unravels the roles of mechanical forces in renal progenitor cell physiology

BACKGROUND

The glomerulus is a highly complex system, composed of different interdependent cell types that are subjected to various mechanical stimuli. These stimuli regulate multiple cellular functions, and changes in these functions may contribute to tissue damage and disease progression. To date, our understanding of the mechanobiology of glomerular cells is limited, with most research focused on the adaptive response of podocytes. However, it is crucial to recognize the interdependence between podocytes and parietal epithelial cells, in particular with the progenitor subset, as it plays a critical role in various manifestations of glomerular diseases. This highlights the necessity to implement the analysis of the effects of mechanical stress on renal progenitor cells.

METHODS

Microgravity, modeled by Rotary Cell Culture System, has been employed as a system to investigate how renal progenitor cells respond to alterations in the mechanical cues within their microenvironment. Changes in cell phenotype, cytoskeleton organization, cell proliferation, cell adhesion and cell capacity for differentiation into podocytes were analyzed.

RESULTS

In modeled microgravity conditions, renal progenitor cells showed altered cytoskeleton and focal adhesion organization associated with a reduction in cell proliferation, cell adhesion and spreading capacity. Moreover, mechanical forces appeared to be essential for renal progenitor differentiation into podocytes. Indeed, when renal progenitors were exposed to a differentiative agent in modeled microgravity conditions, it impaired the acquisition of a complex podocyte-like F-actin cytoskeleton and the expression of specific podocyte markers, such as nephrin and nestin. Importantly, the stabilization of the cytoskeleton with a calcineurin inhibitor, cyclosporine A, rescued the differentiation of renal progenitor cells into podocytes in modeled microgravity conditions.

CONCLUSIONS

Alterations in the organization of the renal progenitor cytoskeleton due to unloading conditions negatively affect the regenerative capacity of these cells. These findings strengthen the concept that changes in mechanical cues can initiate a pathophysiological process in the glomerulus, not only altering podocyte actin cytoskeleton, but also extending the detrimental effect to the renal progenitor population. This underscores the significance of the cytoskeleton as a druggable target for kidney diseases.

Understanding the podocyte immune responses in proteinuric kidney diseases: from pathogenesis to therapy

The glomerular filtration barrier, comprising the inner layer of capillary fenestrated endothelial cells, outermost podocytes, and the glomerular basement membrane between them, plays a pivotal role in kidney function. Podocytes, terminally differentiated epithelial cells, are challenging to regenerate once injured. They are essential for maintaining the integrity of the glomerular filtration barrier. Damage to podocytes, resulting from intrinsic or extrinsic factors, leads to proteinuria in the early stages and eventually progresses to chronic kidney disease (CKD). Immune-mediated podocyte injury is a primary pathogenic mechanism in proteinuric glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and lupus nephritis with podocyte involvement. An extensive body of evidence indicates that podocytes not only contribute significantly to the maintenance of the glomerular filtration barrier and serve as targets of immune responses but also exhibit immune cell-like characteristics, participating in both innate and adaptive immunity. They play a pivotal role in mediating glomerular injury and represent potential therapeutic targets for CKD. This review aims to systematically elucidate the mechanisms of podocyte immune injury in various podocyte lesions and provide an overview of recent advances in podocyte immunotherapy. It offers valuable insights for a deeper understanding of the role of podocytes in proteinuric glomerular diseases, and the identification of new therapeutic targets, and has significant implications for the future clinical diagnosis and treatment of podocyte-related disorders.

Cytoskeleton Rearrangement in Podocytopathies: An Update

Podocyte injury can disrupt the glomerular filtration barrier (GFB), leading to podocytopathies that emphasize podocytes as the glomerulus's key organizer. The coordinated cytoskeleton is essential for supporting the elegant structure and complete functions of podocytes. Therefore, cytoskeleton rearrangement is closely related to the pathogenesis of podocytopathies. In podocytopathies, the rearrangement of the cytoskeleton refers to significant alterations in a string of slit diaphragm (SD) and focal adhesion proteins such as the signaling node nephrin, calcium influx via transient receptor potential channel 6 (TRPC6), and regulation of the Rho family, eventually leading to the disorganization of the original cytoskeletal architecture. Thus, it is imperative to focus on these proteins and signaling pathways to probe the cytoskeleton rearrangement in podocytopathies. In this review, we describe podocytopathies and the podocyte cytoskeleton, then discuss the molecular mechanisms involved in cytoskeleton rearrangement in podocytopathies and summarize the effects of currently existing drugs on regulating the podocyte cytoskeleton.

The mechanism of the NFAT transcription factor family involved in oxidative stress response

As a transcriptional activator widely expressed in various tissues, nuclear factor of activated T cells (NFAT) is involved in the regulation of the immune system, the development of the heart and brain systems, and classically mediating pathological processes such as cardiac hypertrophy. Oxidative stress is an imbalance of intracellular redox status, characterized by excessive generation of reactive oxygen species, accompanied by mitochondrial dysfunction, calcium overload, and subsequent lipid peroxidation, inflammation, and apoptosis. Oxidative stress occurs during various pathological processes, such as chronic hypoxia, vascular smooth muscle cell phenotype switching, ischemia-reperfusion, and cardiac remodeling. Calcium overload leads to an increase in intracellular calcium concentration, while NFAT can be activated through calcium-calcineurin, which is also the main regulatory mode of NFAT factors. This review focuses on the effects of NFAT transcription factors on reactive oxygen species production, calcium overload, mitochondrial dysfunction, redox reactions, lipid peroxidation, inflammation, and apoptosis in response to oxidative stress. We hope to provide a reference for the functions and characteristics of NFAT involved in various stages of oxidative stress as well as related potential targets.

Comparison of Dosage of Glucocorticoid in Idiopathic Membranous Nephropathy: A Systematic Review and Network Meta-Analysis

PURPOSE

Idiopathic membranous nephropathy (IMN) with moderate risk or above was recommended to receive immunosuppressive therapy. We attempted to evaluate the optimal dose of glucocorticoid when combined with evidence-proven effective immunosuppressants by network meta-analysis.

METHODS

A systematic review of the literature was conducted in PubMed, Embase, Cochrane Library, and ClinicalTrials.gov from inception until January 2022. Randomized controlled trials (RCTs) in IMN limited to supportive care, glucocorticoids, cyclophosphamide, chlorambucil, calcineurin inhibitors (CNIs), and rituximab were screened.

RESULTS

Twenty-eight RCTs of 1,830 patients were included. Therapeutic regimens were divided as follows: moderate- to high-dose glucocorticoids plus CNIs (HMSCn), moderate- to high-dose glucocorticoids plus cyclophosphamide (HMSCt), moderate- to high-dose glucocorticoids plus chlorambucil (HMSCh), zero- to low-dose glucocorticoids plus CNIs (LNSCn), zero- to low-dose glucocorticoids plus cyclophosphamide (LNSCt), rituximab alone (R), glucocorticoids alone (SE), and supportive care alone (SP). Compared with SP, HMSCh (risk ratio [RR]: 1.77, 95% confidence interval [CI]: 1, 3.18), HMSCn (RR: 2.5, 95%CI: 1.25, 5.11), HMSCt (RR: 2.15, 95%CI: 1.29, 3.64), LNSCn (RR: 2.16, 95%CI: 1.25, 3.95), and R (RR: 2.07, 95%CI: 1, 4.39) had a higher probability of total remission rate, while HMSCn represented the highest probability depending on the surface under the cumulative ranking area (SUCRA) ranking values. Regarding infection, no significant difference was found between different doses of glucocorticoids plus the same immunosuppressant. HMSCn and HMSCt showed superiority in reducing 24-hour urine total protein compared with HMSCh, LNSCn, SE, and SP, while HMSCn seemed to be the most effective regimen through the ranking of SUCRA value.

CONCLUSION

Moderate- to high-dose glucocorticoids showed superiority in proteinuria remission when combined with CNIs in IMN, with no increasing risk of infection.

The Good and the Bad of SHROOM3 in Kidney Development and Disease: A Narrative Review

Purpose of review

Multiple large-scale genome-wide association meta-analyses studies have reliably identified an association between genetic variants within the SHROOM3 gene and chronic kidney disease. This association extends to alterations in known markers of kidney disease including baseline estimated glomerular filtration rate, urinary albumin-to-creatinine ratio, and blood urea nitrogen. Yet, an understanding of the molecular mechanisms behind the association of SHROOM3 and kidney disease remains poorly communicated. We conducted a narrative review to summarize the current state of literature regarding the genetic and molecular relationships between SHROOM3 and kidney development and disease.

Sources of information

PubMed, PubMed Central, SCOPUS, and Web of Science databases, as well as review of references from relevant studies and independent Google Scholar searches to fill gaps in knowledge.

Methods

A comprehensive narrative review was conducted to explore the molecular mechanisms underlying SHROOM3 and kidney development, function, and disease.

Key findings

SHROOM3 is a unique protein, as it is the only member of the SHROOM group of proteins that regulates actin dynamics through apical constriction and apicobasal cell elongation. It holds a dichotomous role in the kidney, as subtle alterations in SHROOM3 expression and function can be both pathological and protective toward kidney disease. Genome-wide association studies have identified genetic variants near the transcription start site of the SHROOM3 gene associated with chronic kidney disease. SHROOM3 also appears to protect the glomerular structure and function in conditions such as focal segmental glomerulosclerosis. However, little is known about the exact mechanisms by which this protection occurs, which is why SHROOM3 binding partners remain an opportunity for further investigation.

Limitations

Our search was limited to English articles. No structured assessment of study quality was performed, and selection bias of included articles may have occurred. As we discuss future directions and opportunities, this narrative review reflects the academic views of the authors.

The Importance of Sphingomyelin Phosphodiesterase Acid-Like 3b (SMPDL-3b) Levels in Kidney Biopsy Specimens of Children With Nephrotic Syndrome

OBJECTIVE

It remains unclear whether the low amount of SMPDL-3b required for rituximab binding is the cause of treatment resistance in patients with treatment-resistant nephrotic syndrome with advanced podocyte injury. Given the limited number of studies on the relationship between rituximab and SMPDL-3b, this study was conducted to assess whether SMPDL-3b levels in pretreatment renal biopsy specimens can be used to predict the clinical effectiveness of immunosuppressive drugs, especially rituximab, in children with nephrotic syndrome.

METHODS

Kidney biopsy specimens from 44 patients diagnosed with idiopatic nephrotic syndrome were analyzed using immunohistochemical staining with an anti-SMPDL-3b antibody and real-time polymerase chain reaction (PCR) for SMPDL-3b mRNA expression.

RESULTS

We showed that SMPDL-3b mRNA expression and anti-SMPDL-3b antibody staining did not differ significantly between the patient groups with different responses to immunosuppressive therapies.

CONCLUSION

Our results suggest that SMPDL-3b may actually be an indicator of disease progression rather than a marker for predicting response to a particular immunosuppressive agent.

Kidney involvement in systemic lupus erythematosus: From the patient assessment to a tailored treatment

In the last few years, several studies have provided new evidence for the diagnosis, management, and follow-up of patients with lupus nephritis. Evidence showing dissociation between clinical and histological findings has prompted reevaluation of the role of the kidney biopsy as a tool for diagnosis and follow-up. In therapeutics, four immunosuppressive schemes now have supporting evidence for use as initial therapy. Current challenges include individualized selection of the best immunosuppressive regimen, an unmet need for non-invasive biomarkers of disease activity to inform treatment responses and guide subsequent therapy, holistic patient management in this complex, multisystem disease, and ultimately the development of more targeted therapies directed at specific effector pathways driving glomerular inflammation and damage in order to improve treatment response. In this communication, we review the diagnostic and therapeutic approach to lupus nephritis, as well as evaluation of response to therapy and disease control.

Levamisole Modulation of Podocytes' Actin Cytoskeleton in Nephrotic Syndrome

Podocytes play a central role in glomerular diseases such as (idiopathic) nephrotic syndrome (iNS). Glucocorticoids are the gold standard therapy for iNS. Nevertheless, frequent relapses are common. In children with iNS, steroid-sparing agents are used to avoid prolonged steroid use and reduce steroid toxicity. Levamisole is one of these steroid-sparing drugs and although clinical effectiveness has been demonstrated, the molecular mechanisms of how levamisole exerts its beneficial effects remains poorly studied. Apart from immunomodulatory capacities, nonimmunological effects of levamisole on podocytes have also been suggested. We aimed to elaborate on the effects of levamisole on human podocytes in iNS. RNA sequencing data from a human podocyte cell line treated with levamisole showed that levamisole modulates the expression of various genes involved in actin cytoskeleton stabilization and remodeling. Functional experiments showed that podocytes exposed to puromycin aminonucleoside (PAN), lipopolysaccharides (LPS), and NS patient plasma resulted in significant actin cytoskeleton derangement, reduced cell motility, and impaired cellular adhesion when compared to controls, effects that could be restored by levamisole. Mechanistic studies revealed that levamisole exerts its beneficial effects on podocytes by signaling through the glucocorticoid receptor and by regulating the activity of Rho GTPases. In summary, our data show that levamisole exerts beneficial effects on podocytes by stabilizing the actin cytoskeleton in a glucocorticoid receptor-dependent manner.

Mannan-binding lectin ameliorates renal fibrosis by suppressing macrophage-to-myofibroblast transition

Mannan-binding lectin (MBL) is a pattern-recognition molecule that plays a crucial role in innate immunity. MBL deficiency correlates with an increased risk of chronic kidney disease (CKD). However, the molecular mechanisms are not fully defined. Here, we established a CKD model in wild-type (WT) and MBL-deficient (MBL-/-) mice via unilateral ureteral obstruction (UUO). The result showed that MBL deficiency aggravated the pathogenesis of renal fibrosis in CKD mice. Strikingly, the in vivo macrophage depletion investigation revealed that macrophages play an essential role in the MBL-mediated suppression of renal fibrosis. We found that MBL limited the progression of macrophage-to-myofibroblast transition (MMT) in kidney tissues of UUO mice. Further in vitro study showed that MBL-/- macrophages exhibited significantly increased levels of fibrotic-related molecules compared with WT cells upon transforming growth factor beta (TGF-β) stimulation. We demonstrated that MBL inhibited the MMT process by suppressing the production of matrix metalloproteinase 9 (MMP-9) and activation of Akt signaling. In summary, our study revealed an expected role of MBL on macrophage transition during renal fibrosis, thus offering new insight into the potential of MBL as a therapeutic target for CKD.

Nephrotic syndrome: pathophysiology and consequences

In patients with kidney disease, nephrotic syndrome can lead to several complications including progressive kidney dysfunction. Proteinuria may lead to the formation of cellular or fibrous crescents with reciprocal development of rapidly progressive glomerulonephritis or focal glomerulosclerosis. Proteinuria may also cause overload and dysfunction of tubular epithelial cells, eventually resulting in tubular atrophy and interstitial fibrosis. Hypoalbuminemia is usually associated with increased risk of mortality and kidney dysfunction. Dyslipidemia may increase the risk of atherosclerotic complications, cause podocyte dysfunction and contribute to vascular thrombosis. Urinary loss of anticoagulants and overproduction of coagulation factors may facilitate a hypercoagulable state. Edema, hypogammaglobulinemia, loss of complement factors, and immunosuppressive therapy can favor infection. Treatment of these complications may reduce their impact on the severity of NS. Nephrotic syndrome is a kidney disorder that can worsen the quality of life and increase the risk of kidney disease progression.

Efficacy and safety of immunosuppressive agents for adults with lupus nephritis: a systematic review and network meta-analysis

Introduction

Various immunosuppressive regimens have been developed for the treatment of lupus nephritis (LN). This study aimed to compare the efficacy and safety of immunosuppressive regimens in adults with LN.

Methods

We systematically searched the PubMed, Embase, and Cochrane Central Register of Controlled Trials databases, including conference proceedings, trial registries, and reference lists, from inception until July 10, 2022. The effects of treatment were compared and ranked using the surface under the cumulative ranking curve (SUCRA). The primary endpoint was total remission. The secondary endpoints were complete remission, systemic lupus erythematosus disease activity index (SLEDAI), relapse, all-cause mortality, end-stage renal disease (ESRD), infection, herpes zoster, ovarian failure, myelosuppression, and cancer.

Results

Sixty-two trials reported in 172 studies involving 6,936 patients were included in the network meta-analysis. The combination of tacrolimus (TAC), mycophenolate mofetil (MMF), and glucocorticoid (GC) provided the best result for the total remission rate (SUCRA, 86.63%) and SLEDAI (SUCRA, 91.00%), while the combination of voclosporin (VCS) , MMF and GC gave the best improvement in the complete remission rate (SUCRA, 90.71%). The combination of cyclophosphamide (CYC), MMF and GC was associated with the lowest risk of relapse (SUCRA, 85.57%) and cancer (SUCRA, 85.14%), while the combination of obinutuzumab (OTB), MMF and GC was associated with the lowest risk of all-cause mortality (SUCRA, 84.07%). Rituximab (RTX) plus MMF plus GC was associated with the lowest risk of ESRD (SUCRA, 83.11%), while the risk of infection was lowest in patients treated with azathioprine (AZA) plus CYC plus GC (SUCRA, 68.59%). TAC plus GC was associated with the lowest risk of herpes zoster (SUCRA, 87.67%) and ovarian failure (SUCRA, 73.60%). Cyclosporine (CsA) plus GC was associated with the lowest risk of myelosuppression (SUCRA, 79.50%), while AZA plus GC was associated with the highest risk of myelosuppression (SUCRA, 16.25%).

Discussion

This study showed that a combination of TAC, MMF and GC was the best regimen for improving the total remission rate. The optimal regimen for specific outcomes should be highlighted for high-risk patients.

Deletion of protein tyrosine phosphatase SHP-1 restores SUMOylation of podocin and reverses the progression of diabetic kidney disease

Both clinical and experimental data suggest that podocyte injury is involved in the onset and progression of diabetic kidney disease (DKD). Although the mechanisms underlying the development of podocyte loss are not completely understood, critical structural proteins such as podocin play a major role in podocyte survival and function. We have reported that the protein tyrosine phosphatase SHP-1 expression increased in podocytes of diabetic mice and glomeruli of patients with diabetes. However, the in vivo contribution of SHP-1 in podocytes is unknown. Conditional podocyte-specific SHP-1-deficient mice (Podo-SHP-1-/-) were generated to evaluate the impact of SHP-1 deletion at four weeks of age (early) prior to the onset of diabetes and after 20 weeks (late) of diabetes (DM; Ins2+/C96Y) on kidney function (albuminuria and glomerular filtration rate) and kidney pathology. Ablation of the SHP-1 gene specifically in podocytes prevented and even reversed the elevated albumin/creatinine ratio, glomerular filtration rate progression, mesangial cell expansion, glomerular hypertrophy, glomerular basement membrane thickening and podocyte foot process effacement induced by diabetes. Moreover, podocyte-specific deletion of SHP-1 at an early and late stage prevented diabetes-induced expression of collagen IV, fibronectin, transforming growth factor-β, transforming protein RhoA, and serine/threonine kinase ROCK1, whereas it restored nephrin, podocin and cation channel TRPC6 expression. Mass spectrometry analysis revealed that SHP-1 reduced SUMO2 post-translational modification of podocin while podocyte-specific deletion of SHP-1 preserved slit diaphragm protein complexes in the diabetic context. Thus, our data uncovered a new role of SHP-1 in the regulation of cytoskeleton dynamics and slit diaphragm protein expression/stability, and its inhibition preserved podocyte function preventing DKD progression.

14-3-3 Proteins stabilize actin and vimentin filaments to maintain processes in renal glomerular podocyte

14-3-3 proteins are a ubiquitously expressed family of adaptor proteins. Despite exhibiting high sequence homology, several 14-3-3 isoforms have isoform-specific binding partners and roles. We reported that 14-3-3β interacts with FKBP12 and synaptopodin to maintain the structure of actin fibers in podocytes. However, the precise localization and differential role of 14-3-3 isoforms in kidneys are unclear. Herein, we showed that 14-3-3β in glomeruli was restricted in podocytes, and 14-3-3σ in glomeruli was expressed in podocytes and mesangial cells. Although 14-3-3β was dominantly co-localized with FKBP12 in the foot processes, a part of 14-3-3β was co-localized with Par3 at the slit diaphragm. 14-3-3β interacted with Par3, and FKBP12 bound to 14-3-3β competitively with Par3. Deletion of 14-3-3β enhanced the interaction of Par3 with Par6 in podocytes. Gene silencing for 14-3-3β altered the structure of actin fibers and process formation. 14-3-3β and synaptopodin expression was decreased in podocyte injury models. In contrast, 14-3-3σ in podocytes was expressed in the primary processes. 14-3-3σ interacted with vimentin but not with the actin-associated proteins FKBP12 and synaptopodin. Gene silencing for 14-3-3σ altered the structure of vimentin fibers and process formation. 14-3-3σ and vimentin expression was increased in the early phase of podocyte injury models but was decreased in the late stage. Together, the localization of 14-3-3β at actin cytoskeleton plays a role in maintaining the foot processes and the Par complex in podocytes. In contrast, 14-3-3σ at vimentin cytoskeleton is essential for maintaining primary processes.

Management of Lupus Nephritis: New Treatments and Updated Guidelines

Management of lupus nephritis has evolved considerably over the past years. Here, we provide a comprehensive review of clinical trials that form the basis for the Kidney Disease: Improving Global Outcomes and EULAR/ERA-EDTA updated guidelines and present day trials that will change the landscape of lupus nephritis therapy in years to come. In addition, we highlight the issues related to cost of therapy, resistant disease, and downstream adverse effects of specific therapies.

The effect of mycophenolate mofetil on podocytes in nephrotoxic serum nephritis

Mycophenolate mofetil (MMF) is applied in proteinuric kidney diseases, but the exact mechanism of its effect on podocytes is still unknown. Our previous in vitro experiments suggested that MMF can ameliorate podocyte damage via restoration of the Ca2+-actin cytoskeleton axis. The goal of this study was to characterize podocyte biology during MMF treatment in nephrotoxic serum (NTS) nephritis (NTN). NTN was induced in three-week old wild-type mice. On day 3, half of the mice were treated with MMF (100 mg/kgBW/d p.o.) for one week. On day 10, we performed proteomic analysis of glomeruli as well as super-resolution imaging of the slit diaphragm. For multiphoton imaging of Ca2+ concentration ([Ca2+]i), the experimental design was repeated in mice expressing podocyte-specific Ca2+ sensor. MMF ameliorated the proteinuria and crescent formation induced by NTS. We identified significant changes in the abundance of proteins involved in Ca2+ signaling and actin cytoskeleton regulation, which was further confirmed by direct [Ca2+]i imaging in podocytes showing decreased Ca2+ levels after MMF treatment. This was associated with a tendency to restoration of podocyte foot process structure. Here, we provide evidence that MPA has a substantial direct effect on podocytes. MMF contributes to improvement of [Ca2+]i and amelioration of the disorganized actin cytoskeleton in podocytes. These data extend the knowledge of direct effects of immunosuppressants on podocytes that may contribute to a more effective treatment of proteinuric glomerulopathies with the least possible side effects.

Anti-phospholipase A2 receptor-associated membranous nephropathy with human immunodeficiency virus infection treated with telitacicept: A case report

BACKGROUND

The co-occurrence of Anti-phospholipase A2 receptor-associated membranous nephropathy (anti-PLA2R-MN) and human immunodeficiency virus (HIV) infection is a rare clinical scenario, presenting significant challenges in terms of management and treatment.

CASE SUMMARY

A 32-year-old Chinese male diagnosed with HIV infection presented with a clinical history of proteinuria persisting for over two years. A kidney biopsy demonstrated subepithelial immune complex deposition and a thickened glomerular basement membrane, indicative of stage I-II membranous nephropathy. Immunofluorescence staining revealed granular deposition of PLA2R (3+) along the glomerular capillary loops, corroborated by a strongly positive anti-PLA2R antibody test (1:320). Initial treatment involving losartan potassium, rivaroxaban, tacrolimus, and rituximab was discontinued due to either poor effectiveness or the occurrence of adverse events. Following a regimen of weekly subcutaneous injections of telitacicept (160 mg), a marked decline in the 24 h urine protein was observed within a three-month period, accompanied by a rise in serum albumin level. No significant reductions in peripheral blood CD3+CD4+T and CD3+CD8+T cell counts were detected. The patient's physical and psychological conditions showed significant improvements, with no adverse events reported during the treatment course.

CONCLUSION

Telitacicept might offer a potential therapeutic avenue for patients diagnosed with anti-PLA2R-MN concomitant with HIV infection.