金井 孝裕

AIM: The pathophysiology of idiopathic steroid-sensitive nephrotic syndrome (ISSNS) remains unclear. This study aimed to explore the pathophysiology by examining E-cadherin injury, observed in atopic dermatitis, and VE-cadherin injury, associated with systemic edema formation. METHODS: Twenty-one paediatric patients with ISSNS were enrolled. Serum E- and VE-cadherin levels were measured using ELISA and compared between the nephrotic and remission phases. Correlations between each serum E- and VE-cadherin level and urinary protein/creatinine (UP/UCr) ratios and serum albumin (Alb) levels were analysed. Additionally, a correlation between changes in serum VE-cadherin levels and in body weight between phases was analysed. RESULTS: Both serum E- and VE-cadherin levels were elevated in the nephrotic phase compared to the remission phase (p < 0.01 for both). Remission-phase E-cadherin levels remained higher than those in healthy children, while remission-phase VE-cadherin levels were similar to those in healthy children. Serum E-cadherin levels showed a significant correlation with UP/UCr ratios (p = 0.04), but not with serum Alb levels. Serum VE-cadherin levels did not correlate with either UP/UCr ratios or serum Alb levels. However, changes in VE-cadherin levels between the phases were significantly correlated with changes in body weight (p = 0.04). CONCLUSION: Elevated E- and VE-cadherin levels during the nephrotic phase suggest that injury to these adhesion molecules may be correlated with the disease status and could serve as biomarkers for paediatric ISSNS. Injury to E-cadherin may contribute to proteinuria while injury to VE-cadherin may lead to systemic edema. These findings provide new insights into paediatric ISSNS pathophysiology.

BACKGROUND: Fabry disease is a hereditary disorder caused by a deficiency of α-galactosidase A, leading to the accumulation of globotriaosylceramide (GL-3) in multiple cell types throughout the body. Terminally differentiated non-dividing cells, such as podocytes, are particularly susceptible to such accumulation and therefore require effective therapeutic intervention. Gene therapy is an ideal therapeutic intervention for replacing the deficient enzyme; however, one of the major challenges is maintaining long-term expression of episomal transgenes during cell division. In this regard, podocytes, as non-dividing cells, represent an ideal target for gene therapy in Fabry disease. Nevertheless, it has not been confirmed yet whether gene therapy vectors can transduce podocytes and reduce GL-3 accumulation especially in podocytes. METHODS: Male Fabry disease model mice (TgG3S/GLA knockout mice) received an intravenous injection of 2 × 1012 vector genomes of AAV9 encoding human GLA at 6 weeks of age. Kidney tissues were analyzed 8 weeks after administration by electron microscopy (EM) and immunogold EM. RESULTS: In AAV9/hGLA-treated mice, GL-3 accumulation was markedly reduced in most podocytes, endothelial cells, and tubular epithelial cells, whereas it was evident in untreated mice. Virus-like particles were detected only in treated mice. Furthermore, immunogold EM confirmed the presence of AAV9 particles in the podocytes of treated mice. CONCLUSIONS: AAV9/hGLA gene therapy may reduce podocyte GL-3 accumulation in a Fabry disease mouse model, potentially through AAV9 transduction of podocytes; however, given the technical limitations of our approach, the precise cellular mechanisms remain to be determined.

Background/Objectives: Therapeutic drug monitoring (TDM) of immunosuppressants is essential in treating pediatric kidney diseases; however, repeated venipuncture is burdensome in children. We evaluated whether minimally invasive fingerstick capillary sampling combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) provides results analytically comparable to those of conventional venous sampling. Methods: Capillary whole blood (2.8 µL) was collected via fingersticks from pediatric patients receiving mycophenolate mofetil, with or without tacrolimus (TAC) or cyclosporine A (CsA). Drug concentrations were quantified using a previously validated simultaneous LC-MS/MS method and compared with conventional venous sampling using linear regression and Bland-Altman analyses. Results: Seventy-four paired samples from 21 patients were analyzed. Strong correlations were observed between capillary and venous samples for mycophenolic acid (MPA), TAC, and CsA (R2 > 0.90). Hematocrit correction improved agreement for MPA. Bland-Altman analyses demonstrated acceptable bias across analytes. Conclusions: Fingerstick-based microvolume sampling combined with LC-MS/MS provides analytically reliable immunosuppressant quantification in pediatric patients. Although larger clinical validation is required, this minimally invasive approach may reduce procedural burden and may support future outpatient or home-based TDM strategies.

Idiopathic steroid-sensitive nephrotic syndrome (ISSNS) is the most common glomerular disease in children, yet its molecular mechanisms and lipid-mediated pathophysiology remain poorly understood. In this study, we performed comprehensive non-targeted metabolomic analysis of serum samples obtained from children with ISSNS during both the nephrotic and remission phases to identify metabolic alterations associated with disease status. Using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS), we profiled low-molecular-weight metabolites and identified significant alterations in several lipid classes, including sphingolipids, glycerophospholipids, and lysophospholipids. Several sphingomyelin and phosphatidylcholine species showed strong correlations with total cholesterol levels, reflecting lipid alterations consistent with the hyperlipidemic state that characterizes ISSNS. In contrast, oxidized phosphatidylcholines may more specifically reflect oxidative membrane injury and glomerular permeability changes associated with disease status. These findings highlight membrane lipid remodeling as a key feature of active disease and suggest potential lipid-based biomarkers for disease monitoring and therapeutic evaluation in pediatric ISSNS. This study provides a metabolomic framework for understanding lipid-driven mechanisms of ISSNS pathophysiology.

C1q nephropathy (C1qN) presenting with steroid-resistant nephrotic syndrome (SRNS) often demands immunosuppressants to maintain remission. Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is one of the immunosuppressants used. However, MMF increases susceptibility to infection, which can lead to severe complications in some cases. Therefore, the optimal blood concentration of MMF for C1qN remains undefined. A three-year-old boy presented with SRNS due to C1qN and was treated with prednisolone (PSL) and MMF at 720 mg/day, achieving remission. However, the patient developed BK virus viruria and experienced a relapse of nephrotic syndrome (NS) simultaneously. After the MMF dose was reduced to 600 mg/day, the patient entered sustained remission without recurrent infections. Ultimately, he was able to maintain remission with only 600 mg/day of MMF, without the need for steroids. During the second remission, the area under the MPA concentration-time curve from 0 to 12 hours (MPA-AUC0-12) was measured at 53.2 μg·h/mL, suggesting that this level may be sufficient to maintain remission while minimizing the risk of infection, and could serve as a reference point for determining the optimal blood concentration in C1qN treatment. To our knowledge, this is the first report to suggest a potentially optimal MPA-AUC0-12 for maintaining remission in C1qN without recurrent infection. Further studies of MPA-AUC0-12 for C1qN are warranted to confirm this result.