BACKGROUND

Nephrotic syndrome can be caused by a subgroup of mitochondrial diseases classified as primary coenzyme Q10 (CoQ10) deficiency. Pathogenic COQ2 variants are a cause of primary CoQ10 deficiency and present with phenotypes ranging from isolated nephrotic syndrome to fatal multisystem disease.

UNASSIGNED

We report three pediatric patients with COQ2 variants presenting with nephrotic syndrome. Two of these patients had normal leukocyte CoQ10 levels prior to treatment. Pathologic findings varied from mesangial sclerosis to focal segmental glomerulosclerosis, with all patients having abnormal appearing mitochondria on kidney biopsy. In two of the three patients treated with CoQ10 supplementation, the nephrotic syndrome resolved; and at follow-up, both have normal renal function and stable proteinuria.

CONCLUSIONS

COQ2 nephropathy should be suspected in patients presenting with nephrotic syndrome, although less common than disease due to mutations in NPHS1, NPHS2, and WT1. The index of suspicion should remain high, and we suggest that providers consider genetic evaluation even in patients with normal leukocyte CoQ10 levels, as levels may be within normal range even with significant clinical disease. Early molecular diagnosis and specific treatment are essential in the management of this severe yet treatable condition.

Congenital nephrotic syndrome of the Finnish type, due to homozygous mutation of NPHS1, is the most common form of congenital nephrotic syndrome. Angiotensin converting enzyme (ACE) and prostaglandin synthesis inhibition along with supportive albumin infusion therapy, with or without unilateral nephrectomy, has allowed management of the disease without dialysis until transplantation in some cases of congenital nephrotic syndrome. Reported here is a case of heterozygous NPHS1 mutation, with normal NPHS2 gene structure, presenting during prenatal screening and developing nephrotic syndrome within days of birth. The patient has responded well to very low doses of ACE inhibitors and indomethacin alone. This case illustrates the importance of an initial trial of conservative medical therapy in milder presentations of the congenital nephrotic syndrome, especially given the current limitations of diagnostic testing and our inadequate knowledge of the complete spectrum of disorders of podocyte proteins.

Nephrotic syndrome is defined as the association of massive proteinuria, hypoalbuminaemia, edema, and hyperlipidemia. It is separated to steroid-sensitive or steroid-resistant (SRNS) forms in respect to the response to intensive steroid therapy. SRNS usually progresses to end-stage renal failure. According to the North American Pediatric Renal Trials and Collaborative Studies SRNS constitutes the second most frequent cause of ESRD in the first two decades of life. Unfortunately, there is no curative treatment for majority of patients. Majority of the SRNS patients have the histologic picture of focal segmental glomerulosclerosis. Interestingly, the risk of recurrence in the kidney graft in patients with hereditary SRNS is lower than in those who do not have genetic background. The etiology and pathogenesis of SRSN has remained enigma for decades. The discovery of 39 dominant or recessive SRNS genes enabled better understanding of the function of the glomerular podocytes and slit membrane. Hildebrandt's group has shown that 85% of the SRNS cases with onset by 3 months of age and 66% with onset by 1 year of age can be explained by recessive mutations in one of four genes only (NPHS1, NPHS2, LAMB2, or WT1). The same group used modern diagnostic techniques such as the next generation sequencing and tested a large international cohort of SRNS patients (n = 1783 families). The diagnostic panel included 21 genes with a recessive mode of inheritance and 6 genes with a dominant mode of inheritance. Single-gene cause was detected in 29.5% (526 of 1783) of the families with SRNS that manifested before 25 years of age. The identification of causative single-gene mutations may have important therapeutic consequences in some cases. This is very important for patients who carry mutations in a gene of coenzyme Q10 biosynthesis (COQ2, COQ6, ADCK4, or PDSS2). In these patients the treatment with coenzyme Q10 may be indicated. Also, patients with recessive mutations in PLCE1 may respond fully to the treatment with steroids or cyclosporine A. The patients with CUBN may benefit the treatment with vitamin B12. The detection of causative mutations may also be very important for familial genetic counseling and for prenatal diagnosis.

UNASSIGNED

Management of children with congenital nephrotic syndrome (CNS) is challenging. Bilateral nephrectomies followed by dialysis and transplantation are practiced in most centres, but conservative treatment may also be effective.

UNASSIGNED

We conducted a 6-year review across members of the European Society for Paediatric Nephrology Dialysis Working Group to compare management strategies and their outcomes in children with CNS.

UNASSIGNED

Eighty children (50% male) across 17 tertiary nephrology units in Europe were included (mutations in NPHS1, n = 55; NPHS2, n = 1; WT1, n = 9; others, n = 15). Excluding patients with mutations in WT1, antiproteinuric treatment was given in 42 (59%) with an increase in S-albumin in 70% by median 6 (interquartile range: 3-8) g/L (P < 0.001). Following unilateral nephrectomy, S-albumin increased by 4 (1-8) g/L (P = 0.03) with a reduction in albumin infusion dose by 5 (2-9) g/kg/week (P = 0.02). Median age at bilateral nephrectomies (n = 29) was 9 (7-16) months. Outcomes were compared between two groups of NPHS1 patients: those who underwent bilateral nephrectomies (n = 25) versus those on conservative management (n = 17). The number of septic or thrombotic episodes and growth were comparable between the groups. The response to antiproteinuric treatment, as well as renal and patient survival, was independent of NPHS1 mutation type. At final follow-up (median age 34 months) 20 (80%) children in the nephrectomy group were transplanted and 1 died. In the conservative group, 9 (53%) remained without dialysis, 4 (24%; P < 0.001) were transplanted and 2 died.

UNASSIGNED

An individualized, stepwise approach with prolonged conservative management may be a reasonable alternative to early bilateral nephrectomies and dialysis in children with CNS and NPHS1 mutations. Further prospective studies are needed to define indications for unilateral nephrectomy.

From January 1995 to June 2018, 14 patients with congenital nephrotic syndrome (CNS) were diagnosed in the Department of Pediatrics, Peking University First Hospital. The clinical data were retrospectively studied. Eight patients underwent genetic testing; 7 of them had NPHS1 mutations (primary CNS), and 1 did not have a mutation. Of the 7 patients with NPHS1 mutations, 6 died, and 1 had proteinuria. Of the 14 patients, 8 had cytomegalovirus (CMV) infection, and anti-CMV therapy was administered to 7 of them. The other patient was hospitalized in critically ill condition and died before anti-CMV therapy administration. Of the 7 patients who were administered anti-CMV therapy, proteinuria disappeared in 2 patients; 2 patients died; 2 patients were lost to follow up; and 1 patient still had 3+ proteinuria. Three patients had both NPHS1 mutations and CMV infection. After anti-CMV therapy, proteinuria was resolved in 1 patient but relapsed to 3+ proteinuria due to a new infection. The other 2 patients died. Of 14 patients, only 1 patient underwent renal biopsy, with results showing mesangial proliferative glomerulonephritis pathology, negative CMV inclusion body, and CMV-DNA. In this study, genetic defect could play a primary role in CNS, and CMV could play a secondary role. Primary CNS with NPHS1 mutations has a poor prognosis. Primary CNS might be accompanied by CMV infection that responds poorly to antiviral treatment. Secondary CNS caused by CMV infection may be cured with antiviral therapy. However, genetic analysis is necessary to exclude genetic defects.

Background: Chronic kidney disease (CKD) is a global public health problem. Cell therapy using pluripotent stem cells represents an attractive therapeutic approach for the treatment of CKD.

Methods: We transplanted mitomycin C (MMC)-treated human induced pluripotent stem cells (hiPSCs) and renal progenitor cells (RPCs) into a CKD rat model system. The RPC and hiPSC cells were characterized by immunofluorescence and qRT-PCR. Untreated 5/6 nephrectomized rats were compared to CKD animals receiving the same amount of MMC-treated hiPSCs or RPCs. Renal function, histology, and immunohistochemistry were evaluated 45 days post-surgery.

Results: We successfully generated hiPSCs from peripheral blood and differentiated them into RPCs expressing renal progenitor genes (PAX2, WT1, SIX2, and SALL1) and podocyte-related genes (SYNPO, NPHS1). RPCs also exhibited reduced OCT4 expression, confirming the loss of pluripotency. After cell transplantation into CKD rats, the body weight change was significantly increased in both hiPSC and RPC groups, in comparison with the control group. Creatinine clearance (CCr) was preserved only in the hiPSC group. Similarly, the number of macrophages in the kidneys of the hiPSC group reached a statistically significant reduction, when compared to control rats. Both treatments reduced positive staining for the marker α-smooth muscle actin. Histological features showed decreased tubulointerstitial damage (interstitial fibrosis and tubular atrophy) as well as a reduction in glomerulosclerosis in both iPSC and RPC groups.

Conclusions: In conclusion, we describe that both MMC-treated hiPSCs and RPCs exert beneficial effects in attenuating CKD progression. Both cell types were equally efficient to reduce histological damage and weight loss caused by CKD. hiPSCs seem to be more efficient than RPCs, possibly due to a paracrine effect triggered by hiPSCs. These results demonstrate that the use of MMC-treated hiPSCs and RPCs improves clinical and histological CKD parameters, avoided tumor formation, and therefore may be a promising cell therapy strategy for CKD.

Keywords: Cell- and tissue-based therapy; Chronic kidney disease; Pluripotent stem cells; Stem cells.

Steroid-resistant nephrotic syndrome (SRNS) is one of the major causes of end-stage renal disease (ESRD) in childhood and is mostly associated with focal segmental glomerulosclerosis (FSGS). More than 50 monogenic causes of SRNS or FSGS have been identified. Recently, the mutation detection rate in pediatric patients with SRNS has been reported to be approximately 30%. In this study, genotype-phenotype correlations in a cohort of 291 Korean pediatric patients with SRNS/FSGS were analyzed. The overall mutation detection rate was 43.6% (127 of 291 patients). WT1 was the most common causative gene (23.6%), followed by COQ6 (9.4%), NPHS1 (8.7%), NUP107 (7.1%), and COQ8B (6.3%). Mutations in COQ6, NUP107, and COQ8B were more frequently detected, and mutations in NPHS2 were less commonly detected in this cohort than in study cohorts from Western countries. The mutation detection rate was higher in patients with congenital onset, those who presented with proteinuria or chronic kidney disease/ESRD, and those who did not receive steroid treatment. Genetic diagnosis in patients with SRNS provides not only definitive diagnosis but also valuable information for decisions on treatment policy and prediction of prognosis. Therefore, further genotype-phenotype correlation studies are required.

Keywords: focal segmental glomerulosclerosis; genetic analysis; steroid-resistant nephrotic syndrome.

Podocytes are major kidney cells that help in glomerular filtration and any damage or loss is a major event in the progression of kidney diseases. Understanding podocytes development will help in designing therapeutic strategies against these renal diseases. Therefore, in vitro generation of podocytes from adult hematopoietic CD34+ stem cells is explored in the present study. Apheretically, isolated human HSCs from peripheral blood showed the presence of CD34 surface glycoprotein through immunocytochemistry (ICC) and flowcytometry. Initially, these HSCs were induced with activin-A (10 ng/ml), retinoic acid (RA) (10 ng/ml) and bone morphogenic protein (BMP-7) (2.5 ng/ml) for 5 days. Transdifferentiation of HSCs to podocytes through intermediate mesoderm was studied with positive selection of Osr1+ cells. Subsequently, thus-obtained Osr1+ cells were induced further with activin-A (10 ng/ml), RA (10 ng/ml), BMP-7 (2.5 ng/ml), EGF (30 ng/ml) and bFGF (30 ng/ml) for 9 days. Distinct cobblestone morphological changes were observed on staining with Leishman's stain. Consequently, differentiated cells were immunopositive for anti-podocin, anti-synaptopodin and anti-GLEPP1 monoclonal antibodies. These cells showed expression of early podocyte markers PAX2 and Wt1 at day 3 followed by day 6 and mature podocyte markers NPHS1, SULT1B1, NPHS2 and Synaptopodin at day 9. Interestingly, on day 9, diminished expression of PAX2 was noted. Differentiated cells showed high tyrosine kinase activity signifying that phosphorylation controls slit diaphragm proteins. Synaptopodin regulates the integrity of cytoskeleton and cell motility of podocytes and this phenomenon was confirmed through scratch assay using agarose molds that showed high cell mobility and migration. These findings establish HSCs as ideal candidates for regenerative therapies of damaged podocytes.

The congenital nephrotic syndrome (CNS) is an uncommon disorder with onset of the nephrotic syndrome usually in the first three months of life. Several different diseases may cause the syndrome. These may be inherited, sporadic, acquired or part of a general malformation syndrome. The clinical course is marked by failure to thrive, recurrent life threatening bacterial infections, and early death from sepsis and/or uremia. A characteristic phenotype may be seen in children with CNS. The majority of reported cases of CNS are of the Finnish type (CNF). Although the role of the glomerular basement membrane has been emphasized as the barrier for retaining plasma proteins, recent studies have clearly shown that the slit diaphragm is the structure most likely to be the barrier in the glomerular capillary wall. The gene (NPHS1) was shown to encode a novel protein that was termed nephrin, due to its specific location in the kidney filter barrier, where it seems to form a highly organized filter structure. Nephrin is a transmembrane protein that probably forms the main building block of an isoporous zipper-like slit diaphragm filter structure. Defects in nephrin lead to the abnormal or absent slit diaphragm resulting in massive proteinuria and renal failure.

Often the cause of refractory lupus nephritis (RLN) remains unclear. We performed next-generation sequencing for podocyte genes in an RLN patient and identified compound heterozygosity for APOL1 risk alleles G1 and G2 and a novel homozygous c.[1049C>T]+[1049C>T] NPHS1 gene variant of unknown significance. To test for causality renal progenitor cells isolated from urine of this patient were differentiated into podocytes in vitro. Podocytes revealed aberrant nephrin trafficking, cytoskeletal structure and lysosomal leakage, and increased detachment as compared with podocytes isolated from controls. Thus, lupus podocytopathy can be confirmed as a cause of RLN by functional genetics on patient-derived podocytes.

The nephrin gene NPHS1 was cloned in 1998. Studies in families with congenital nephrotic syndrome led to the identification of this critical component of the glomerular slit diaphragm. Studies such as the new one by Santín et al. are expanding our understanding of the spectrum of disease associated with NPHS1 mutations.

OBJECTIVE

To explore the correlation between Chinese medicine (CM) syndromes and the NPHS1 gene and NPHS2 gene polymorphism as well as corticosteroid sensitivity in patients with minimal change disease (MCD).

METHODS

A total of 94 MCD patients were recruited, including 58 steroid-sensitive nephritic syndrome (SSNS) patients and 36 steroid-resistant nephritic syndrome (SRNS) patients. Genomic DNA was obtained from peripheral blood lymphocytes and sequence analysis of single nucleotide polymorphisms (SNPs) in the genes was performed.

RESULTS

(1) The SNPs of G349A-3 in NPHS1 gene was found in MCD, but the SNPs of G686A-5 and C695T-5 in NPHS2 gene were not discovered in MCD. (2) When comparing the frequency of genotype AA and allele A in NPHS1 gene (G349A-3), genotype AA and allele A were higher in the SRNS group than in the SSNS group (P < 0.05). (3) When compared with the SRNS group, qi yang deficiency syndrome had a higher incidence in the SSNS group, and yin deficiency syndrome and qi-yin deficiency syndrome had a less incidence in the SSNS, but with no statistical difference (P>> 0.05). The rheumatism syndrome had a higher incidence in the SSNS group (P < 0.05). The blood stasis syndrome had a lower incidence in the SSNS with statistical difference (P < 0.05). (4) There was no statistical difference in the correlation between GG, AA, GA and CM syndromes (P>> 0.05).

CONCLUSIONS

Homozygous mutations of AA and allele A in NPHS1 gene were correlated to SRNS patients of MCD. Rheumatism syndrome patients were prone to be sensitive to corticosteroids, while patients of blood stasis syndrome were prone to be insensitive to corticosteroids. We didn't discover the correlation between NPHS1 gene polymorphism and CM syndrome distribution.

BACKGROUND

Congenital nephrotic syndrome may be caused by mutations in NPHS1 and NPHS2, which encode nephrin and podocin, respectively. Since the identification of the NPHS2 gene, various investigators have demonstrated that its mutation is an important cause of steroid-resistant nephrotic syndrome. We aimed to evaluate frequency and spectrum of podocin mutations in the Iranian children with steroid-resistant nephritic syndrome.

METHODS

We examined 20 children with steroid-resistant nephritic syndrome referred to Ali Asghar Children's Hospital, in Tehran, Iran. Mutations in the 5th and 7th exons of NPHS2 were assessed. The mutational analysis of NPHS2 was performed by DNA sequencing.

RESULTS

The mean age at the onset of proteinuria was 6.4 +/- 3.6 years. None of the children had mutations in the exons 5 or 7.

CONCLUSIONS

Our study suggests that NPHS2 mutations in exons 5 and 7 are not seen in our children. Therefore, we cannot recommend NPHS2 (exons 5 and 7) mutation for screening in Iranian children with steroid-resistant nephritic syndrome. Other exons of podocin or other podocyte proteins in Iranian children may play a role in pathogenesis of steroid-resistant nephritic syndrome.

BACKGROUND

Congenital nephrotic syndrome of Finnish type (NPHS1) is an autosomal recessive disorder characterized by severe proteinuria of intrauterine onset. Ninety-four percent of the Finnish NPHS1 chromosomes have been reported to carry either a 2-bp deletion in exon 2 (Fin(Major)) or a nonsense mutation in exon 26 (Fin(Minor)) of the NPHS1 gene. The high prevalence of only two mutations in the Finnish population enables the use of molecular techniques in the diagnosis of NPHS1 and for carrier screening.

RESULTS

We describe two different molecular methods for the detection of the NPHS1 mutations: a PCR-restriction fragment length polymorphism (PCR-RFLP) and a dual-color oligonucleotide ligation assay (OLA). The dual-color OLA, which enables simultaneous detection of the NPHS1 Fin(Major) and Fin(Minor) mutations, can be used for rapid analysis of large sets of samples. The analysis of 2004 Finnish blood samples revealed 34 carriers of the Fin(Major) mutation and 1 carrier of the Fin(Minor) mutation, indicating a carrier frequency of 1:59 (95% confidence interval, 1:89-1:44) for the NPHS1 Fin(Major) mutation and 1:2004 (95% confidence interval, 0 to 1:677) for the NPHS1 Fin(Minor) mutation, respectively.

CONCLUSIONS

PCR-RFLP and dual-color OLA are suitable for molecular diagnosis and carrier screening of the major mutations that cause NPHS1.

Congenital nephrotic syndrome (CNS) is a rare disease inherited as an autosomally recessive trait and defined as proteinuria manifesting at birth or in the first 3 months of life. The classical form is the Finnish type of CNS (CNF), which is caused by mutations in the nephrin gene (NPHS1). The classical findings include prematurity, large placenta and massive proteinuria. Minor cardiac findings have been reported as a minor functional disorder but CNS with major cardiac malformation is rare. Here we report the case of a Turkish child with CNS with small indel mutation (c.614_621delCACCCCGGinsTT) in exon 6 of NPHS1 and also major cardiac malformation who did not develop end-stage renal disease until the age of 5 years.