Nephroprotective Effects of Curcumin in Murine Models of Focal and Segmental Glomerulosclerosis

Bradykinin receptor 1 activation exacerbates experimental focal and segmental glomerulosclerosis

FSGS: Forme Pleine or Forme Fruste

BackgroundThis study aimed to investigate the effect of the Phellinus linteus (Mesima) decoction on podocyte injury in a rat model of focal and segmental glomerulosclerosis (FSGS) and evaluate the potential mechanisms.MethodsFSGS resembling primary FSGS in humans was established in rats by uninephrectomy and the repeated injection of doxorubicin. The FSGS rats were randomly divided into the model group, low-dose group of P. linteus decoction (PLD-LD), medium-dose group of P. linteus decoction (PLD-MD), and high-dose group of P. linteus decoction (PLD-HD). Blood and urine analysis were performed after 12 weeks and the molecular indicators of renal function and the renal pathological changes were examined.ResultsFSGS developed within 12 weeks in the test group and showed progressive proteinuria and segmental glomerular scarring. Urinary protein, serum creatinine, urea nitrogen, triglycerides and cholesterol were significantly reduced following the 12-week intervention with P.linteus decoction, especially in the PLD-LD group. Renal nephrin and podocin were markedly increased. Moreover, the pathological damage in the renal tissue was alleviated by the PLD-LD intervention.ConclusionThe P. linteus decoction alleviated the podocyte injury in the FSGS rat model, thus minimizing the progression of glomerular sclerosis and improving renal function.

Objective: To comparatively investigate the ameliorative effect of Phellinus igniarius (P. igniarius) on renal aging in a rat model of focal and segmental glomerulosclerosis (FSGS). Methods: The FSGS model was established in rats by uninephrectomy combined with tail vein injection of doxorubicin. The FSGS rats were randomly divided into the model group, the P. igniarius decoction group, the P. igniarius polysaccharides group, and the P. igniarius polyphenols group. Molecular indicators of cell senescence, renal function indexes, and podocyte injury markers were tested after ten weeks of intragastric administration. Besides, the pathological renal lesions and the ultrastructural changes were observed. Results: FSGS developed in the model group within ten weeks and showed segmental glomerular scarring and renal aging. Following the 10-week intervention, 24 h proteinuria, serum creatinine, blood urea nitrogen, P16INK4α, thrombospondin-1, and transforming growth factor-β1 were decreased in each treatment group, whereas albumin, erythropoietin, nephrin, and podocin were increased; the pathological renal injury was alleviated, and the number of senescent cells was reduced, especially in rats treated with P. igniarius decoction. Conclusions: P. igniarius ameliorates renal aging and renal injury in the FSGS rat model. Compared with the effective constituents (polysaccharides and polyphenols), P. igniarius decoction has a better curative effect, which is expected to provide a new therapeutic idea for FSGS.

ABSTRACTBackground/Aim: Effacement of the epithelial cell foot processes of glomerular podocytes are thought to be diffuse in the primary form of focal and segmental glomerulosclerosis (FSGS). In contrast, effacements that occur in the secondary form of FSGS are thought to be focal. To evaluate this theory, the extent of epithelial cell foot process effacement was analyzed and compared in podocytes from cases of primary and secondary FSGS.Methods: Consecutive cases of adult primary and secondary FSGS that were diagnosed between January 1997 and December 2010 were retrospectively retrieved and analyzed. The electron microscopy materials of all specimens were reviewed. Glomerular podocytes from each sample were counted, recorded and analyzed for the percentage of diffuse versus focal epithelial foot process effacement.Results: Seventeen primary and 16 secondary FSGS specimens were reviewed. In the 17 primary FSGS cases, 35.1% of the podocytes were focally fused, and 64.9% were diffusely fused. In the 16 secondary FSGS cases, 72.1% of the podocytes were focally fused. There were significantly more focally fused podocytes in secondary FSGS than in primary FSGS. In contrast, significantly more diffusely fused podocytes were observed in primary FSGS than in secondary FSGS.Conclusion: This is the first study to perform a quantitative analysis of the extent of epithelial cell foot process effacement in podocytes in primary and secondary FSGS. This study also confirms that the electron microscopic characteristics of the podocyte effacement process can be used to facilitate the diagnosis of primary versus secondary FSGS.

Focal and segmental glomerulosclerosis (FSGS) is a histopathological entity that identifies a group of glomerular kidney disorders, which manifest by a certain pattern of sclerosis that involves parts of some glomeruli (focal segmental) on light microscopy. In most cases of FSGS, in particular the primary or idiopathic FSGS, the first site of the damage is the podocyte, which marks the beginning of this disease. However, FSGS can be a secondary process to another injury in the glomeruli, giving the definition of secondary FSGS. A large number of pathogenic factors have been identified, which lead to podocyte injury and, thereafter, to FSGS. Several genetic predispositions and mutations have been confirmed, especially in young patients, causing an early onset of primary FSGS. Acquired causes of FSGS constitute a large list of factors that may directly or indirectly injure the podocyte cells. Identifying these factors in the cases of primary or idiopathic FSGS has been the focus of extensive research investigations. For many decades, researchers speculated the presence of circulating factors to be the pathogenic causes of primary FSGS. These factors are thought to be the cause of FSGS recurrence post-kidney transplantation as well. However, not until recently, these factors are being identified. In 2011, soluble urokinase plasminogen activator receptor (suPAR) was suggested to be a circulating factor leading to primary FSGS and post-transplantation FSGS recurrence.

The renal biopsy specimens obtained from 15 adults with focal and segmental glomerulosclerosis (FSGS) and 15 adults with minimal change nephrotic syndrome (MCNS) were morphometrically analyzed using light and electron microscopy. Moreover, initial biopsy specimens obtained from 10 adults who were diagnosed as MCNS and developed FSGS, based on repeat biopsy findings (‘MCNS’-FSGS), were also analyzed using electron microscopy. After comparing the actual values between the groups of FSGS and MCNS, the mean glomerular volume, the capillary volume per a glomerulus, the capillary filtration surface per a glomerulus, and the capillary diameter (Cap-D) were all larger in the FSGS group than in the MCNS group. In regard to the morphological values in the ‘MCNS’-FSGS group, both values of the surface density of the capillary filtering surface and the capillary diameter at the first biopsy specimens as well as those in the FSGS group were higher than those in the MCNS group. When analyzing the structural parameters, in the FSGS series, we found a high association of the percentage of obsolescent glomeruli (%SG) with the mean glomerular volume, the capillary volume per a glomerulus, the capillary filtering surface per a glomerulus and the capillary length per a glomerulus, however we failed to demonstrate the correlation between the %SG and the Cap-D. Thus, the glomerular structure in the ‘MCNS’-FSGS patients, even at the first renal biopsy, resembled that in FSGS, suggesting FSGS to be a distinct entity from MCNS. These data indicate that the enlargement of the capillary volume, resulting from the widening of the capillaries, was the initial structural event for adults with FSGS, while the elongation of the capillaries appeared to reflect some compensatory process for the decrease in the functioning nephron.

The denomination ‘idiopathic nephrotic syndrome’ (INS) is progressively replacing the time-honoured term ‘nephrosis’ to define a disease comprising: (a) nephrotic syndrome; (b) on renal biopsy, absence of any lesions by light microscopy and immunofluorescence (minimal change disease, MCD), or with lesions of focal and segmental glomerulosclerosis (FSG); and (c) absence of concomitant identified disease. Of note, this last element can be assessed only after sufficient follow-up, as some rare cases of MCD may herald lymphoma [1] or discovery of a solid tumour [2]. Similarly, FSG cannot be considered ‘idiopathic’ before a host of conditions have been ruled out [3]. That MCD and FSG represent the same entity has never been definitely proven [4]. FSG can be overlooked on renal biopsy [5, 6], and a transition from MCD to FSG is common in corticosteroid-resistant forms [7]. This is why paediatricians, who rarely carry out renal biopsy at first contact with a nephrotic child, consider that the sole point of interest in INS (or nephrosis — I shall use both terms) is its mode of response to corticosteroid treatment. In fact, FSG differs from MCD in many ways. Even when the glomerular tuft appears normal by standard microscopy, the glomerular size is larger in FSG than in cases which remain MCD over time [8]. Proteinuria selectivity index [9] is poor in FSG and to some extent helps predict a poor response to therapy. Finally, FSG usually develops along with tubulointerstitial damage, interstitial fibrosis and vascular lesions, in which the part played by massive proteinuria [10, 11] and by the offending substance responsible for the podocyte changes of FSG [12], remains an open question.

Focal and Segmental Glomerulosclerosis and Plasma Cell Proliferative Disorders

Secondary Focal and Segmental Glomerulosclerosis Associated With Single-Nucleotide Polymorphisms in the Genes Encoding Complement Factor H and C3

Background and Aims The hormone FGF23 is a biomarker associated with morbidity and mortality in individuals with and without kidney disease, but the role of FGF23 excess as a pathogenic factor is incompletely understood. Here, we investigated renal FGF23 signaling in kidney disease models. Method This study used three independent disease models: i) Male C57BL/6 mice (n = 16) were treated with Freud's adjuvant and nephrotoxic serum (NTS) to induce anti-glomerular basement membrane (anti-GBM) disease. ii) Female BALB/c mice (n = 8) were treated with adriamycin (doxorubicin) 10.5 mg/kg to induce focal and segmental glomerulosclerosis (FSGS). iii) Male DBA/2J mice (n = 20) were fed a diet containing adenine 0.2%. Control mice of the respective same strain and sex received vehicle injections. Mice of the anti-GBM and FSGS models and controls received intravenous injections of recombinant FGF23 1 µg or vehicle for six consecutive days (anti-GBM) or once (FSGS), with dissection 24 h after the last injection. Mice of the adenine model were dissected after 15 weeks. Following dissection, ex vivo precision-cut kidney slices (PCKS) were obtained from n = 4 mice and maintained for 24 at 37°C, 95% O2 and 5% CO2, followed by a 1 h treatment with recombinant FGF23 200 ng/ml or vehicle. Glomerular filtration rate (GFR) or renal retention parameters in serum and albuminuria were assessed. Kidneys underwent histological assessment using hematoxylin & eosin or Masson's trichrome. Renal RNA was isolated for bulk RNAseq. Differential gene expression was assessed to determine the effect of FGF23 treatment in disease-free controls, in each disease model, and the interaction between FGF23 X disease effect for the anti-GBM and FSGS groups. Gene set enrichment analysis was performed with a focus on the immune system. Results Anti-GBM mice showed a 45 ± 27% GFR decline (mean ± SD) compared to baseline, whereas controls showed an GFR increase of 11 ± 36% (p < 0.01). Kidney histology revealed an interstitial infiltrate. The FSGS model showed elevated serum creatinine and albuminuria, and hypercellularity in some glomeruli. Mice of the adenine model showed progressively increased blood urea nitrogen concentrations starting after 2 weeks, up to a 3-fold increase at week 14. Histology revealed interstitial fibrosis and tubular atrophy. Bulk RNAseq revealed proinflammatory transcriptional signatures after FGF23 treatment in all disease models, regardless of which timepoint or model: In the anti-GBM model, Hallmark gene sets of inflammatory response, interferon-α response, interferon-β response and allograft rejection were significantly increased after 6 days of FGF23 treatment, whereas disease-free controls showed no significantly changed immune gene sets after 6 days of FGF23. In FSGS mice, none of the Hallmark gene sets were changed after 1 FGF23 injection, but top individual gene expression affected by 1 FGF23 injection were an increased proinflammatory transcription factor Cebpb and an increased DNA damage transcript Dclre1b. Finally, the PCKS of adenine model revealed no significant Hallmark gene sets, but the two genes with differential expression were a proinflammatory macrophage/fibroblast chemokine Ccl4 (increased) and an immunoglobulin heavy variable Ighv2-2 (decreased). Conclusion FGF23-driven patterns of proinflammatory gene expression were observed in three experimental models of kidney disease, both in vivo and ex vivo assessment of FGF23 signaling, thus excluding effects of FGF23 on other organs. As these findings were limited to transcriptional analyses, the present data warrant further confirmation and exploration of FGF23 as a pathogenic agent in kidney disease.

There are controversies whether Minimal Change Disease (MCD) and Focal and Segmental Glomerulosclerosis (FSGS) are distinct glomerular lesions or different manifestations within the same spectrum of diseases. The uPAR (urokinase-type plasminogen activator receptor) and some slit diaphragm proteins may be altered in FSGS glomeruli and may function as biomarkers of the disease in renal biopsies. Thus, this study aims to evaluate the diagnostic potential of uPAR and glomerular proteins for differentiation between MCD and FSGS in renal pediatric biopsy. Renal biopsies from 50 children between 2 and 18 years old were selected, with diagnosis of MCD (n = 29) and FSGS (n = 21). Control group consisted of pediatric autopsies (n = 15) from patients younger than 18 years old, with no evidences of renal dysfunction. In situ expressions of WT1, nephrin, podocin and uPAR were evaluated by immunoperoxidase technique. Renal biopsy of patients with MCD and FSGS expressed fewer WT1 (p≤0.0001, F = 19.35) and nephrin (p<0.0001; H = 21.54) than patients in the control group. FSGS patients expressed fewer podocin than control (p<0.0359, H = 6.655). FSGS cases expressed more uPAR than each of control and MCD (p = 0.0019; H = 12.57) and there was a positive and significant correlation between nephrin and podocin (p = 0.0026, rS = 0.6502) in these cases. Podocin had sensitivity of 73.3% and specificity of 86.7% (p = 0.0068) and uPAR had sensitivity of 78.9% and specificity of 73.3% (p = 0.0040) for diagnosis of FSGS patients. The main limitation of the study is the limited number of cases due to the difficulty in performing biopsy in pediatric patients. Podocin and uPAR are good markers for FSGS and differentiate these cases from MCD, reinforcing the theory of distinct glomerular diseases. These findings suggest that podocin and uPAR can be used as biomarkers in the routine analysis of renal biopsies in cases of podocytopathies when the lesion (sclerosis) is not sampled.

Mutations in the INF2 gene account for a significant proportion of familial but not sporadic focal and segmental glomerulosclerosis

Focal and Segmental Glomerulosclerosis (FSGS) is a severe glomerulopathy that frequently leads to end stage renal disease. Only a subset of patients responds to current therapies, making it important to identify alternative therapeutic options. The interleukin (IL)-1 receptor antagonist anakinra is beneficial in several diseases with renal involvement. Here, we evaluated the potential of anakinra for FSGS treatment. Molecular process models obtained from scientific literature data were used to build FSGS pathology and anakinra mechanism of action models by exploiting information on protein interactions. These molecular models were compared by statistical interference analysis and expert based molecular signature matching. Experimental validation was performed in Adriamycin- and lipopolysaccharide (LPS)-induced nephropathy mouse models. Interference analysis (containing 225 protein coding genes and 8 molecular process segments) of the FSGS molecular pathophysiology model with the drug mechanism of action of anakinra identified a statistically significant overlap with 43 shared molecular features that were enriched in pathways relevant in FSGS, such as plasminogen activating cascade, inflammation and apoptosis. Expert adjudication of molecular signature matching, focusing on molecular process segments did not suggest a high therapeutic potential of anakinra in FSGS. In line with this, experimental validation did not result in altered proteinuria or significant changes in expression of the FSGS-relevant genes COL1A1 and NPHS1. In summary, an integrated bioinformatic and experimental workflow showed that FSGS relevant molecular processes can be significantly affected by anakinra beyond the direct drug target IL-1 receptor type 1 (IL1R1) context but might not counteract central pathophysiology processes in FSGS. Anakinra is therefore not suggested for extended preclinical trials.

Influence of Vimentin and E-cadherin on the development of interstitial fibrosis in focal and segmental glomerulosclerosis - FSGS.