Yihui Zhai

Background.: Kidney transplantation is the optimal treatment for pediatric end-stage kidney disease, yet donor shortages have driven the use of pediatric donor kidneys through pediatric donor-to-pediatric recipient (PTP) kidney transplantation. This study aimed to investigate the effect of donor-recipient size on graft growth in PTP kidney transplantation. Methods.: This retrospective cohort study included kidney transplant recipients who underwent regular follow-ups between January 2016 and December 2023 at the Children’s Hospital of Fudan University. All donors were deceased and aged P < 0.01). The mean estimated glomerular filtration rate at the last follow-up was 84.1 ± 31.8 mL/min/1.73 m ² . Posttransplant estimated glomerular filtration rate showed a significant positive correlation with donor-recipient body weight ratio during the early posttransplant period (1, 3, and 6 mo; P < 0.01). Smaller grafts required approximately 6 mo to reach a normative size consistent with the recipients’ age. Conclusions.: Grafts showed stable growth patterns and favorable short-term follow-up outcomes. Additionally, PTP kidney transplantation demonstrated both clinical value and practical utility.

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute the most common underlying cause of chronic kidney disease in pediatric populations. Maternal hypovitaminosis D links to mesoderm-related birth defects, leading to our hypothesis that maternal vitamin D deficiency (VDD) impairs renal development (a mesoderm-derived process) and induces offspring CAKUT. To investigate whether a low-vitamin D level can cause CAKUT, we used vitamin D-free diets to induce a maternal vitamin D deficiency mice model. The maternal vitamin D deficiency (VDD) mice models and normal vitamin D status (CON) were successfully established by administering a vitamin D-free or vitamin D-sufficient diet for 4 weeks prior to pregnancy. The overall incidence of CAKUT was significantly increased in VDD neonatal mice (19.4% vs. 2.44%; p = 0.0006), with a higher incidence of early duplicated budding in E11.5. E11.5 ureteric bud tissue revealed significantly increased activity of Gdnf-Ret-p-Erk1/2 signaling in the VDD group. In vivo intervention with the p-Erk1/2 antagonist U0126 in the pregnant VDD mice model at E10.5 improved CAKUT occurrence in offspring with p-Erk1/2 expression decreasing toward normal levels. Early metanephric ureteric bud H3K4me3 CUT&TAG analysis at E12.5 revealed chromatin activation patterns, which revealed that the downregulation of Hnf1β promoter region peaks was accompanied by reduced Hnf1β expression, and Robo2 promoter region peak was upregulated with increased Robo2 expression in the VDD group. Maternal vitamin D deficiency in mice significantly increased offspring CAKUT incidence. This phenotype was mediated by enhanced Gdnf-Ret-p-Erk1/2 signaling and reversed by p-Erk1/2 inhibition, with VDD inducing epigenetic remodeling of Hnf1β and Robo2 promoters.

Patients with nephronophthisis caused by nephrocystin 3 (NPHP3) variants rapidly progress to end-stage kidney disease. However, existing Nphp3 mouse models fail to fully recapitulate the characteristics of this disease. We generated a renal tubule-specific Nphp3 knockout mouse model that more accurately mirrors the human disease course. The mouse model was first validated by confirming the loss of Nphp3 protein expression in renal tubules. Comprehensive phenotypic analyses were then performed to assess both renal and extrarenal manifestations. The origin of renal cysts was investigated, and the underlying mechanisms were further validated. We successfully generated a renal tubule-specific Nphp3 knockout mouse model (Cdh16-Cre; Nphp3^flox/flox). These mice exhibited a markedly shortened lifespan (5–8 weeks) and developed key features of infantile nephronophthisis, including early-onset renal cysts originating from distal tubules and collecting ducts, progressive interstitial fibrosis that was evident by postnatal week 2, a rapid decline in kidney function, and increased urinary protein levels. Importantly, treatment with the vasopressin V2 receptor antagonist tolvaptan or the mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor 2-(2-chloro-4-iodoanilino)-N-(cyclopropylmethoxy)-3,4-difluorobenzamide (CI-1040) significantly attenuated cyst growth and improved kidney morphology, confirming shared pathogenic pathways with other Nphp3 models. We established a renal tubule-specific Nphp3 knockout mouse model that accurately recapitulates the aggressive infantile form of nephronophthisis characterized by early cystogenesis, progressive fibrosis, and a shortened lifespan, and is ideal for evaluating novel interventions against this currently untreatable ciliopathy.

Background BK polyomavirus (BKV) infection is a critical complication hindering graft survival after kidney transplantation. We aimed to investigate the risk factors and outcome of BKV infection in pediatric kidney transplantation. Methods The clinical and follow-up data of pediatric kidney transplant recipients at the Children’s Hospital of Fudan University from Jan 2015 to June 2023 were retrospectively analyzed. Results A total of 217 patients were included in the study with mean follow-up time of 24.3 ± 19.9 months. The mean age at transplantation was 9.7 ± 4.2 years. The patient survival rate and graft survival rate were 98.2% and 96.8%, respectively. Twenty-nine patients (13.4%) developed BKV infection, which was detected at 5.8 ± 3.2 months after transplantation. Among these 29 patients with BKV infection, 8 patients (3.6%) developed BKV nephropathy (BKVN), which was diagnosed at 8.3 ± 2.9 months after transplantation, and 2 patients developed graft failure eventually. Compared with the non-BKV infection group (eGFR 76.7 ± 26.1 mL/min/1.73 m²) and BKV infection without BKVN group (eGFR 85.2 ± 23.8 mL/min/1.73 m²), BKVN group had lowest eGFR during follow-up (33.5 ± 11.0 ml/min/1.73 m², P < 0.001). Younger age at transplant (OR 0.850, 95%CI 0.762–0.948, P = 0.005), CAKUT disease of primary etiology (OR 2.890, 95%CI 1.200–6.961, P = 0.018), and CMV negative recipient serostatus before transplantation (OR 3.698, 95%CI 1.583–8.640, P = 0.003) were independent risk factors for BKV infection. Conclusions Incidence of BKV infection is quite high within 12 months after pediatric kidney transplantation and children with BKVN have poor graft function. Younger age at transplant, CAKUT disease, and CMV negative recipient serostatus before transplantation increase the risk of BKV infection after kidney transplantation. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information.

Angiopoietin-like-3 (Angptl3) knockout is known for its protective effects on podocyte injury and proteinuria in the early stage of adriamycin (ADR) nephropathy. The current study re-evaluated the renoprotective effect of Angptl3 knockout in chronic ADR nephropathy and attempted to explore the mechanism underlying the effect associated with Angptl3 knockout in glomerulosclerosis. B6; 129S5 mice were injected with ADR to induce nephropathy. Kidney structure and serum and urine parameters were observed during long-term follow-up. Cultured primary mouse podocytes were exposed to ADR and analyzed for the expression of some relative proteins. Podocyte loss was analyzed in both in vivo and in vitro experiments. Angptl3 knockout attenuated proteinuria and hypoproteinemia, protected renal structure and function, and improved the survival of mice over the whole process of ADR nephropathy. Furthermore, Angptl3 knockout reduced the numbers of the detached and apoptotic cells in the renal tissue and alleviated podocyte loss in mice with ADR chronic nephropathy, thereby, delaying the glomerulosclerosis formation. Additional results in vitro showed that Angptl3 knockout attenuated ADR-induced primary podocyte loss, including podocyte detachment and apoptosis. In addition to serving a renoprotective role in the early stage of ADR nephropathy, Angptl3 knockout contributed to disease amelioration throughout the ADR nephropathy process. Angptl3 knockout effectively delayed glomerulosclerosis formation by attenuating podocyte loss through rescuing podocytes from detachment and apoptosis. Angptl3 antagonists or inhibitors might have therapeutic potential in the occurrence and progression of nephropathy.

Congenital nephrotic syndrome (CNS) is characterised by increased proteinuria, hypoproteinemia, and edema beginning in the first 3 months of life. Recently, molecular genetic studies have identified several genes involved in the pathogenesis of CNS. A systematic investigation of the genes for CNS in China has never been performed; therefore, we conducted a mutational analysis in 12 children with CNS,with the children coming from 10 provinces and autonomous regions in China. Twelve children with CNS were enrolled from 2009 to 2016. A mutational analysis was performed in six children by Sanger sequencing in eight genes (NPHS1, NPHS2, PLCE1, WT1, LAMB2, LMXIB, COQ6 and COQ2) before 2014, and whole-exome sequencing was used from 2014 to 2016 in another six children. Significant variants that were detected by next generation sequencing were confirmed by conventional Sanger sequencing in the patients’ families. Of the 12 children, eight patients had a compound heterozygous NPHS1 mutation, one patient had a de novo mutation in the WT1 gene, and another patient with extrarenal symptoms had a homozygous mutation in the COQ6 gene. No mutations were detected in genes NPHS2, PLCE1, LAMB2, LMXIB, and COQ2 in the 12 patients. This study demonstrates that the majority of CNS cases (67%, 8/12 patients) are caused by genetic defects, and the NPHS1 mutation is the most common cause of CNS in Chinese patients. A mutational analysis of NPHS1 should be recommended in Chinese patients with CNS in all exons of NPHS1 and in the intron-exon boundaries.

Bicarbonate-based peritoneal dialysis (PD) fluids enhance the migratory capacity and damage-repair ability of human peritoneal mesothelial cells by upregulating AQP1. However, little is known about the underlying molecular mechanisms. Here we used HEK-293T cells to investigate the effect of pH on AQP1 gene transcription levels. We found that AQP1 mRNA levels increases with pH. Transfection of HEK-293T cells with luciferase reporter vectors containing different regions of the AQP1 promoter identified an upstream region in the AQP1 gene between − 2200 and – 2300 bp as an enhancer required for pH-mediated regulation of AQP1 expression. Site-directed mutagenesis of this specific promoter region revealed a critical region between − 2257 and − 2251 bp, and gene knock-down experiments and ChIP assays suggested that the Spi-B transcription factor SPIB is involved in pH-mediated regulation of AQP1 expression. We identified an upstream region in the AQP1 gene and the transcription factor SPIB that are critically involved in pH-mediated regulation of AQP1 expression. These findings provide the basis for further studies on the pH- and buffer-dependent effects of PD fluids on peritoneal membrane integrity and function.

Podocyte detachment and apoptosis are two risk factors causing podocyte loss, F-actin rearrangement is involved in detachment and apoptosis. However, the nature of events that promote detachment and apoptosis of podocytes and whether detachment occurred simultaneously with apoptosis are still unclear. Previously, it was found that angiopoietin-like3 (Angptl3) induces F-actin rearrangement in podocytes. In this study we investigate whether Angptl3 influences podocyte loss (detachment and apoptosis) and the process through which Angptl3 exactly influenced the podocyte loss. In conditionally immortalized mice podocytes, recombinant mice Angptl3 protein (rm-Angptl3) was used to mimic Angptl3 overexpression model and transfection with small interfering RNA (siRNA) to knockdown the expression of Angptl3. Both flow cytometry analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay were used to detect apoptosis. Rearrangement of F-actin was assessed using confocal microscopy. Western blot assay was used to measure levels of Angptl3, integrin α3β1, integrin-linked kinase (ILK), p53, caspase 3, and phosphorylation of integrin β1. In a puromycin aminonucleoside (PAN)-induced podocyte injury model, rm-Angptl3 accelerated the loss of podocytes, both detachment and apoptosis occurred, and F-actin rearrangement is involved in the process. However, knockdown of Angptl3 by siRNA markedly ameliorated these injuries. Observed effects were partially correlated with the altered integrin α3β1, ILK and p53, rather than caspase 3. Angptl3 is a novel factor involved in the PAN-induced podocyte loss by affecting detachment and apoptosis in vitro. This study helps to deepen the understanding of the mechanisms of podocyte loss and lays the foundation for developing a new successful therapy for podocyte injury via lower expression of Angptl3.