Nephrotic syndrome with focal segmental glomerular lesions unclassified by Columbia classification; Pathology and clinical implication

Advances in the pathophysiology and treatment of focal segmental glomerulosclerosis: The importance of a timely and tailored approach

Focal segmental glomerulosclerosis (FSGS) is a histological pattern of glomerular damage that significantly contributes to chronic kidney disease and end-stage renal disease. Its incidence is rising globally, necessitating timely and personalized management strategies. This paper aims to provide an updated overview of the pathophysiology, diagnosis, and therapeutic strategies for FSGS, emphasizing the importance of early interventions and tailored treatments. This editorial synthesizes key findings from recent literature to highlight advancements in understanding and managing FSGS. Emerging evidence supports the role of targeted therapies and personalized approaches in improving outcomes for FSGS patients. Advances include novel biomarkers, genetic testing, and innovative therapeutics such as transient receptor potential ion channel blockers and antisense oligonucleotides for apolipoprotein 1-related FSGS. Effective management of FSGS requires a combination of timely diagnosis, evidence-based therapeutic strategies, and ongoing research to optimize patient outcomes and address gaps in the current understanding of the disease.

Nonlinear association between proteinuria levels and the risk of cardiovascular disease events and all-cause mortality among chronic kidney disease patients

BACKGROUND

The association between proteinuria levels and cardiovascular disease (CVD) development and all-cause mortality in chronic kidney disease (CKD) patients remains controversial.

METHODS

In this investigation, we conducted a retrospective analysis involving 1138 patients who were registered in the CKD-Research of Outcomes in Treatment and Epidemiology (ROUTE) study. The primary outcome of this study was the composite of cardiovascular events or all-cause death. Cox proportional hazards regression, smooth curve fitting, piecewise linear regression, and subgroup analyses were used.

RESULTS

The mean age of the included individuals was 67.3 ± 13.6 years old. Adjusted hazard ratios (HRs) for UPCR in middle and high groups, compared to the low group, were 1.93 (95% CI: 1.28-2.91) and 4.12 (95% CI: 2.87-5.92), respectively, after multivariable adjustment. Further adjustments maintained significant associations; HRs for middle and high groups were 1.71 (95% CI: 1.12-2.61) and 3.07 (95% CI: 2.08-4.54). A nonlinear UPCR-primary outcome relationship was observed, with an inflection point at 3.93 g/gCr.

CONCLUSION

Among non-dialyzed patients with stage G2-G5 CKD, a nonlinear association between UPCR and the primary outcome was observed. A higher UPCR (when UPCR < 3.93 g/gCr) was an independent predictor of the primary outcome. Importantly, our study predates SGLT2 inhibitor use, showcasing outcomes achievable without these medications. Future research considerations will involve factors like SGLT-2 inhibitor utilization.

Analyzing three pedigrees in X-linked Alport syndrome with the presentation of nephrotic syndrome

Background

Alport syndrome (AS) is a common cause of end-stage renal disease (ESRD) with various clinical symptoms and incomplete manifestation. Patients with AS and other renal disorders are often misdiagnosed. This study reported three X-linked dominant Alport syndrome (XLAS) pedigrees with nephrotic syndrome (NS) as the predominant phenotype and analyzed COL4A5 gene alterations.

Methods

Three Han Chinese XLAS pedigrees were recruited, and clinical phenotypes were obtained. The pre-certified individuals' peripheral blood DNA was taken, and whole-genome next-generation sequencing (NGS) was performed for candidate genes and mutation screening, followed by NGS or Sanger sequencing of suspected mutant types in participating family members.

Results

Both probands A and B were diagnosed with NS through biochemical tests, and X-linked Alport syndrome-associated renal injury was diagnosed by renal biopsy. The biopsy revealed focal foamy cells in the renal interstitium, tearing and delamination changes in the glomerular basement membrane, and negative α3 and α5 chains of type IV collagen. Proband C, who was earlier diagnosed with NS, has now advanced to ESRD, along with his mother and proband A's mother. Genetic sequencing of all three pedigrees identified three mutations, namely, c.5020C>T, c.4435_4445del, and c.1584_1587+6del in the X-linked dominant gene COL4A5 (NM_000495.5). These mutations lead to the production of shortened proteins, potentially impacting the function of COL4A5 and causing pathogenic effects.

Conclusion

The novel c.4435_4445del and c.1584_1587+6del mutations not only enrich the spectrum of mutations in the COL4A5 gene but also indicate that carriers of both mutation sites and those with mutation c.5020C>T may present NS as their primary clinical manifestation.

Clinicopathological features and medium-term outcomes of histologic variants of primary focal segmental glomerulosclerosis in adults: A retrospective study

BACKGROUND

The Columbia classification identified five histological variants of focal segmental glomerulosclerosis (FSGS). The prognostic significance of these variants remains controversial.

AIM

To evaluate the relative frequency, clinicopathologic characteristics, and medium-term outcomes of FSGS variants at a single center in Pakistan.

METHODS

This retrospective study was conducted at the Department of Nephrology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan on all consecutive adults (≥ 16 years) with biopsy-proven primary FSGS from January 1995 to December 2017. Studied subjects were treated with steroids as a first-line therapy. The response rates, doubling of serum creatinine, and kidney failure (KF) with replacement therapy were compared between histological variants using ANOVA or Kruskal Wallis, and Chi-square tests as appropriate. Data were analyzed by SPSS version 22.0. P-value ≤ 0.05 was considered significant.

RESULTS

A total of 401 patients were diagnosed with primary FSGS during the study period. Among these, 352 (87.7%) had a designated histological variant. The not otherwise specified (NOS) variant was the commonest, being found in 185 (53.9%) patients, followed by the tip variant in 100 (29.1%) patients. Collapsing (COL), cellular (CEL), and perihilar (PHI) variants were seen in 58 (16.9%), 6 (1.5%), and 3 (0.7%) patients, respectively. CEL and PHI variants were excluded from further analysis due to small patient numbers. The mean follow-up period was 36.5 ± 29.2 months. Regarding response rates of variants, patients with TIP lesions achieved remission more frequently (59.5%) than patients with NOS (41.8%) and COL (24.52%) variants (P < 0.001). The hazard ratio of complete response among patients with the COL variant was 0.163 [95% confidence interval (CI): 0.039-0.67] as compared to patients with NOS. The TIP variant showed a hazard ratio of 2.5 (95%CI: 1.61-3.89) for complete remission compared to the NOS variant. Overall, progressive KF was observed more frequently in patients with the COL variant, 43.4% (P < 0.001). Among these, 24.53% of patients required kidney replacement therapy (P < 0.001). The hazard ratio of doubling of serum creatinine among patients with the COL variant was 14.57 (95%CI: 1.87-113.49) as compared to patients with the TIP variant.

CONCLUSION

In conclusion, histological variants of FSGS are predictive of response to treatment with immunosuppressants and progressive KF in adults in our setup.

Evaluation of glomerular sirtuin-1 and claudin-1 in the pathophysiology of nondiabetic focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is the leading cause of nephrotic syndrome, which is characterized by podocyte injury. Given that the pathophysiology of nondiabetic glomerulosclerosis is poorly understood and targeted therapies to prevent glomerular disease are lacking, we decided to investigate the tight junction protein claudin-1 and the histone deacetylase sirtuin-1 (SIRT1), which are known to be involved in podocyte injury. For this purpose, we first examined SIRT1, claudin-1 and podocin expression in kidney biopsies from patients diagnosed with nondiabetic FSGS and found that upregulation of glomerular claudin-1 accompanies a significant reduction in glomerular SIRT1 and podocin levels. From this, we investigated whether a small molecule activator of SIRT1, SRT1720, could delay the onset of FSGS in an animal model of adriamycin (ADR)-induced nephropathy; 14 days of treatment with SRT1720 attenuated glomerulosclerosis progression and albuminuria, prevented transcription factor Wilms tumor 1 (WT1) downregulation and increased glomerular claudin-1 in the ADR + SRT1720 group. Thus, we evaluated the effect of ADR and/or SRT1720 in cultured mouse podocytes. The results showed that ADR [1 µM] triggered an increase in claudin-1 expression after 30 min, and this effect was attenuated by pretreatment of podocytes with SRT1720 [5 µM]. ADR [1 µM] also led to changes in the localization of SIRT1 and claudin-1 in these cells, which could be associated with podocyte injury. Although the use of specific agonists such as SRT1720 presents some benefits in glomerular function, their underlying mechanisms still need to be further explored for therapeutic use. Taken together, our data indicate that SIRT1 and claudin-1 are relevant for the pathophysiology of nondiabetic FSGS.

Clinical Course of Adult FSGS and Minimal Change Disease in North American and Japanese Cohorts

Key Points

Data from different geographical regions highlighted the differences in clinical manifestations and treatment response of adult FSGS/minimal change disease. There were shared factors that were associated with treatment response across the cohorts: FSGS, higher BP, and lower eGFR. Recognizing geographical difference allows us better understanding of disease biology, risk prediction, and design of future clinical trials.

Background

Regional differences in presentation and clinical course of nephrotic syndrome (NS) have not been studied well because few studies directly compared the data from different intercontinental regions.

Methods

We included adult nephrotic patients with FSGS and minimal change disease (MCD) who received immunosuppressive therapy (IST) in a North American (Nephrotic Syndrome Study Network [NEPTUNE], N =89) or Japanese (Nagoya Kidney Disease Registry [N-KDR], N =288) cohort. Baseline characteristics and rates of complete remission (CR) were compared. Factors associated with time to CR were evaluated by Cox regression models.

Results

NEPTUNE participants had more FSGS (53.9 versus 17.0%) and family history of kidney disease (35.2 versus 3.2%). N-KDR participants were older (median 56 versus 43 years) and demonstrated greater levels of urine protein creatinine ratio (7.73 versus 6.65) and hypoalbuminemia (1.6 versus 2.2 mg/dl). N-KDR participants showed higher proportion of CR (overall: 89.2 versus 62.9%; FSGS: 67.3 versus 43.7%; MCD: 93.7 versus 85.4%). A multivariable model showed that FSGS (versus MCD: hazard ratio [HR], 0.28; 95% confidence interval [CI], 0.20 to 0.41), systolic BP (per 10 mm Hg: HR, 0.93; 95% CI, 0.86 to 0.99), and eGFR (per 10 ml/min per 1.73 m2: HR, 1.16; 95% CI, 1.09 to 1.24) were associated with time to CR. There were significant interactions in patient age (P = 0.004) and eGFR (P = 0.001) between the cohorts.

Conclusions

The North American cohort had more FSGS and more frequent family history. Japanese patients showed more severe NS with better response to IST. FSGS, hypertension, and lower eGFR were shared predictors of poor treatment response. Identifying shared and unique features across geographically diverse populations may help uncover biologically relevant subgroups, improve prediction of disease course, and better design future multinational clinical trials.