Minimal change disease as a modifiable podocyte paracrine disorder

Sulfatase 2 Is Associated with Steroid Resistance in Childhood Nephrotic Syndrome

Glucocorticoid (GC) resistance complicates the treatment of ~10-20% of children with nephrotic syndrome (NS), yet the molecular basis for resistance remains unclear. We used RNAseq analysis and in silico algorithm-based approaches on peripheral blood leukocytes from 12 children both at initial NS presentation and after ~7 weeks of GC therapy to identify a 12-gene panel able to differentiate steroid resistant NS (SRNS) from steroid-sensitive NS (SSNS). Among this panel, subsequent validation and analyses of one biologically relevant candidate, sulfatase 2 (SULF2), in up to a total of 66 children, revealed that both SULF2 leukocyte expression and plasma arylsulfatase activity Post/Pre therapy ratios were greater in SSNS vs. SRNS. However, neither plasma SULF2 endosulfatase activity (measured by VEGF binding activity) nor plasma VEGF levels, distinguished SSNS from SRNS, despite VEGF's reported role as a downstream mediator of SULF2's effects in glomeruli. Experimental studies of NS-related injury in both rat glomeruli and cultured podocytes also revealed decreased SULF2 expression, which were partially reversible by GC treatment of podocytes. These findings together suggest that SULF2 levels and activity are associated with GC resistance in NS, and that SULF2 may play a protective role in NS via the modulation of downstream mediators distinct from VEGF.

Tacrolimus Monotherapy after Intravenous Methylprednisolone in Adults with Minimal Change Nephrotic Syndrome

Glucocorticoid treatment is the first choice therapy for adults with minimal change nephrotic syndrome; however, this therapy associates with many adverse effects. Tacrolimus may be an alternative to conventional glucocorticoid therapy. To investigate this possibility, we conducted a prospective, randomized, controlled trial (WHO International Clinical Trials Registry Platform: ChiCTR-TRC-11001454) in eight renal units across China. We randomized enrolled patients with adult-onset minimal change nephrotic syndrome (n=119) to receive glucocorticoid therapy or tacrolimus after intravenous methylprednisolone (0.8 mg/kg per day) for 10 days. Patients received a conventional glucocorticoid regimen or tacrolimus monotherapy, starting with 0.05 mg/kg per day (target trough whole-blood level of 4-8 ng/ml) for 16-20 weeks and subsequently tapering over approximately 18 weeks. Remission occurred in 51 of 53 (96.2%; all complete remission) glucocorticoid-treated patients and 55 of 56 (98.3%; 52 complete and three partial remission) tacrolimus-treated patients (P=0.61 for remission; P=0.68 for complete remission). The groups had similar mean time to remission (P=0.55). Relapse occurred in 49.0% and 45.5% of the glucocorticoid- and tacrolimus-treated patients, respectively (P=0.71), with similar time to relapse (P=0.86). Seven (13.7%) glucocorticoid-treated and four (7.3%) tacrolimus-treated patients suffered frequent relapse (P=0.28); five glucocorticoid-treated and two tacrolimus-treated patients became drug dependent (P=0.26). Adverse events occurred more frequently in the glucocorticoid group (128 versus 81 in the tacrolimus group). Seven adverse events in the glucocorticoid group and two adverse events in the tacrolimus group were serious. Consequently, tacrolimus monotherapy after short-term intravenous methylprednisolone is noninferior to conventional glucocorticoid treatment for adult-onset minimal change nephrotic syndrome in this cohort.

Protective effects of low-dose rapamycin combined with valsartan on podocytes of diabetic rats

The aim of this study was to study the impacts and the mechanisms of low-dose rapamycin combined with valsartan on the renal functions of diabetic nephropathy (DN) rats. 50 SD rats were randomly divided into the normal control group (group A, n=10) and the DN model group (n=40), the DN model group was intraperitoneally injected streptozocin (STZ) for the modeling, which were then equally divided into the DN group (group B), the rapamycin group (group C, orally administrated rapamycin 1 mg/kg/d), the valsartan group (group D, orally administrated valsartan 30 mg/kg/d) and the combined therapy group (group E, orally administrated rapamycin 1 mg/kg/d + valsartan 30 mg/kg/d). Group A and group B were orally administrated the same amount of 0.5% carboxymethylcellulose. After 8-week treatment, the rats of each group were killed for the renal functional and pathological detection, as well as the expression detection of nephrin and podocin of kidney tissues. Compared with group A, the renal functions of the DN model groups were all decreased, and the pathological changes were significant. Meanwhile, the expressions of nephrin/podocin were reduced (P<0.05); among which group B exhibited the most serious changes, while the situations of group E were improved after the combined treatment, the expressions of nephrin/podocin were increased. Low-dose rapamycin and valsartan could enhance the expressions of nephrin and podocin, reduce kidney damages, thus achieving the protective effects towards the kidneys, and the effects of the combined therapy were superior to those of monotherapy.

Morphological Study of Progressive Glomerulonephropathy in Common Marmosets (Callithrix jacchus)

Spontaneous progressive glomerulonephropathy often occurs in common marmosets. However, there are few detailed reports concerning the age-related progressive process of glomerular changes. We discuss the glomerular changes in the early stage and the progressive changes in the advanced stage of nephropathy. We investigated the kidneys of common marmosets (2–11 years old; 9 males and 12 females) using hematoxylin and eosin, periodic acid–Schiff, periodic acid–methenamine-silver, and Masson’s trichrome (MT) stains and a transmission electron microscope. There was no remarkable change in urine cytology, hematology, or blood chemistry. In the early stage of nephropathy, effacement of podocyte foot processes was observed ultrastructurally even though there were no marked glomerular lesions in the light microscopy. Subsequently, mesangial proliferation occurred from the hilar to peripheral side along the tuft. In the middle stage, red deposits were visible at the glomerular basement membrane (GBM) and the mesangial region directly under the GBM (paramesangial area) with the MT stain. Electron dense deposits were seen at the same area. In the advanced stage, the irregularity became prominent with or without dense deposits. It is necessary to investigate in detail whether the change of podocyte in the early stage was immuno-mediated or due to podocyte failure.

Proteinuria predicts relapse in adolescent and adult minimal change disease

OBJECTIVE

This study sought to outline the clinical and laboratory characteristics of minimal change disease in adolescents and adults and establish the clinical and laboratory characteristics of relapsing and non-relapsing patients.

METHODS

We retrospectively evaluated patients with confirmed diagnoses of minimal change disease by renal biopsy from 1979 to 2009; the patients were aged >13 years and had minimum 1-year follow-ups.

RESULTS

Sixty-three patients with a median age (at diagnosis) of 34 (23-49) years were studied, including 23 males and 40 females. At diagnosis, eight (12.7%) patients presented with microscopic hematuria, 17 (27%) with hypertension and 17 (27%) with acute kidney injury. After the initial treatment, 55 (87.3%) patients showed complete remission, six (9.5%) showed partial remission and two (3.1%) were nonresponders. Disease relapse was observed in 34 (54%) patients who were initial responders (n = 61). In a comparison between the relapsing patients (n = 34) and the non-relapsing patients (n = 27), only proteinuria at diagnosis showed any significant difference (8.8 (7.1-12.0) vs. 6.0 (3.6-7.3) g/day, respectively, p = 0.001). Proteinuria greater than 7 g/day at the initial screening was associated with relapsing disease.

CONCLUSIONS

In conclusion, minimal change disease in adults may sometimes present concurrently with hematuria, hypertension, and acute kidney injury. The relapsing pattern in our patients was associated with basal proteinuria over 7 g/day.

The glomerular filtration barrier: components and crosstalk

The glomerular filtration barrier is a highly specialized blood filtration interface that displays a high conductance to small and midsized solutes in plasma but retains relative impermeability to macromolecules. Its integrity is maintained by physicochemical and signalling interplay among its three core constituents-the glomerular endothelial cell, the basement membrane and visceral epithelial cell (podocyte). Understanding the pathomechanisms of inherited and acquired human diseases as well as experimental injury models of this barrier have helped to unravel this interdependence. Key among the consequences of interference with the integrity of the glomerular filtration barrier is the appearance of significant amounts of proteins in the urine. Proteinuria correlates with kidney disease progression and cardiovascular mortality. With specific reference to proteinuria in human and animal disease phenotypes, the following review explores the roles of the endothelial cell, glomerular basement membrane, and the podocyte and attempts to highlight examples of essential crosstalk within this barrier.

The glomerular filtration barrier: components and crosstalk

The glomerular filtration barrier is a highly specialized blood filtration interface that displays a high conductance to small and midsized solutes in plasma but retains relative impermeability to macromolecules. Its integrity is maintained by physicochemical and signalling interplay among its three core constituents—the glomerular endothelial cell, the basement membrane and visceral epithelial cell (podocyte). Understanding the pathomechanisms of inherited and acquired human diseases as well as experimental injury models of this barrier have helped to unravel this interdependence. Key among the consequences of interference with the integrity of the glomerular filtration barrier is the appearance of significant amounts of proteins in the urine. Proteinuria correlates with kidney disease progression and cardiovascular mortality. With specific reference to proteinuria in human and animal disease phenotypes, the following review explores the roles of the endothelial cell, glomerular basement membrane, and the podocyte and attempts to highlight examples of essential crosstalk within this barrier.

Our experience with rituximab therapy for adult-onset primary glomerulonephritis and review of literature

BACKGROUND

B cell-targeted immunosuppression with rituximab as primary treatment or when conventional therapy is contraindicated or unsuccessful can induce remission in idiopathic membranous nephropathy (IMN). We explored the efficacy and safety of rituximab therapy in an adult population with IMN and other primary glomerulonephritides.

METHOD

This study is a single-centre retrospective case review of 24 adult patients who received rituximab (RTX) for IMN (n = 11), minimal change disease (MCD, n = 7), focal segmental glomerulosclerosis (FSGS, n = 4), and membranoproliferative glomerulonephritis (MPGN, n = 2). Outcomes included the proportion of patients with complete and partial remission, frequency of relapse, the amount of post-RTX immunosuppression, and toxicity.

RESULTS

The median follow-up for all patients was 31.5 months (IQR: 15.0-44.0). Rituximab therapy induced remission in 19/24 (79.2 %) patients (IMN: 63.6 %, MCD: 100 %, FSGS: 75 %, and MPGN: 100 %). Disease recurrence in patients with ≥ 3 relapses pre-RTX therapy (MCD, n = 6 and FSGS, n = 1) decreased from 37.0 to 19.6 events per 1,000 patient-months. All patients with steroid maintenance, discontinued or achieved at least a 50 % dose reduction at 3.0 months (IQR: 1.5-8.0) post-treatment. One patient ceased CSA in addition to a 50 % steroid dose reduction 13 months post-RTX. Rituximab was well tolerated with a single serious infection (4.2 %) responsive to treatment.

CONCLUSIONS

Rituximab induced remission in IMN comparable with published reports but had an additional benefit in inducing remission in other common glomerulonephritides. Additional randomized studies are needed to confirm its potential therapeutic benefit and optimal dosing for adult-onset primary glomerulonephritis.

Angiotensin II induces nephrin dephosphorylation and podocyte injury: role of caveolin-1

Nephrin, an important structural and signal molecule of podocyte slit-diaphragm (SD), has been suggested to contribute to the angiotensin II (Ang II)-induced podocyte injury. Caveolin-1 has been demonstrated to play a crucial role in signaling transduction. In the present study, we evaluated the role of caveolin-1 in Ang II-induced nephrin phosphorylation in podocytes. Wistar rats-receiving either Ang II (400 ng/kg/min) or normal saline (via subcutaneous osmotic mini-pumps, control) were administered either vehicle or telmisartan (3 mg/kg/min) for 14 or 28 days. Blood pressure, 24-hour urinary albumin and serum biochemical profile were measured at the end of the experimental period. Renal histomorphology was evaluated through light and electron microscopy. In vitro, cultured murine podocytes were exposed to Ang II (10(-6)M) pretreated with or without losartan (10(-5) M) for variable time periods. Nephrin and caveolin-1 expression and their phosphorylation were analyzed by Western-blotting and immunofluorescence. Caveolar membrane fractions were isolated by sucrose density gradient centrifugation, and then the distribution and interactions between Ang II type 1 receptor (AT1), nephrin, C-terminal Src kinase (Csk) and caveolin-1 were evaluated using Western-blotting and co-immunoprecipitation. Podocyte apoptosis was evaluated by cell nucleus staining with Hoechst-33342. Ang II-receiving rats displayed diminished phosphorylation of nephrin but enhanced glomerular/podocyte injury and proteinuria when compared to control rats. Under control conditions, podocyte displayed expression of caveolin-1 in abundance but only a low level of phospho moiety. Nonetheless, Ang II stimulated caveolin-1 phosphorylation without any change in total protein expression. Nephrin and caveolin-1 were co-localized in caveolae fractions. AT1 receptors and Csk were moved to caveolae fractions and had an interaction with caveolin-1 after the stimulation with Ang II. Transfection of caveolin-1 plasmid (pEGFPC3-cav-1) significantly increased Ang II-induced nephrin dephosphorylation and podocyte apoptosis. Furthermore, knockdown of caveolin-1 expression (using siRNA) inhibited nephrin dephosphorylation and prevented Ang II-induced podocyte apoptosis. These findings indicate that Ang II induces nephrin dephosphorylation and podocyte injury through a caveolin-1-dependent mechanism.