Positive renal familial history in IgA nephropathy is associated with worse renal outcomes: a single-center longitudinal study.

BACKGROUND: IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Although most IgAN cases are sporadic, few show a familial aggregation. However, the prevalence and prognosis of IgAN individuals with positive familial history (FH) of renal disorders remains uncertain. To address these issues, we conducted a longitudinal observational study on a single-institution cohort of patients with biopsy-proven IgAN. METHODS: A total of 467 IgAN patients who underwent renal biopsy during 1994 to 2019 were ascertained to have positive- or negative-FH by history taking and were followed for an average of 8.9 years. We compared the clinical and pathological features of the two subgroups. The primary outcome, a composite of a hard endpoint (end-stage renal disease [ESRD]) and surrogate endpoint (a 50% or more reduction in the estimated glomerular filtration rate [eGFR] from baseline), was evaluated. To estimate the risk for progression to ESRD, a Cox proportional hazards analysis was performed for a subset of patients who underwent follow-up for > 2 years and had an eGFR > 30 mL/min/1.73 m2 at baseline (n = 389; observation, 8.7 years). RESULTS: Positive-FH subtype accounted for 11.6% (n = 54) of all IgAN patients. At baseline, there were no significant differences between the positive- and negative-FH subgroups regarding age, sex, comorbid disease, MEST-C score, observation period, and therapeutic interventions. However, the eGFR value at baselines was significantly lower in the positive-FH subgroup than in the negative-FH subgroup (P < 0.01). On multivariate analysis, positive-FH emerged an independent determinant of poorer renal outcomes (odds ratio, 2.31; 95% confidence interval, 1.10-4.85; P = 0.03), after adjusting for confounding factors. eGFR at follow-up was significantly lower in the positive-FH subgroup than in the negative-FH subgroup after adjustment for age and observation period. CONCLUSIONS: Positive-FH was found in 11.6% of all IgAN patients, consistent with the incidence seen in previous literature. A significantly lower eGFR at baseline and last follow-up and unfavorable renal outcomes in the positive-FH subgroup suggest that certain genetic risk factors predisposing to renal failure may exist in a fraction of our IgAN cohort. (331 words).

A mutation in transcription factor MAFB causes Focal Segmental Glomerulosclerosis with Duane Retraction Syndrome.

Focal segmental glomerulosclerosis (FSGS) is a leading cause of end-stage renal disease in children and adults. Genetic factors significantly contribute to early-onset FSGS, but the etiologies of most adult cases remain unknown. Genetic studies of monogenic syndromic FSGS exhibiting extra-renal manifestations have uncovered an unexpected biological role for genes in the development of both podocytes and other cellular lineages. To help define these roles, we studied two unrelated families with FSGS associated with Duane Retraction Syndrome, characterized by impaired horizontal eye movement due to cranial nerve malformation. All four affected individuals developed FSGS and Duane Retraction Syndrome in their first to second decade of life, manifested as restricted abduction together with globe retraction and narrowed palpebral fissure on attempted adduction. Hypoplasia of the abducens nerves and hearing impairment occurred in severely affected individuals. Genetic analyses revealed that affected individuals harbor a rare heterozygous substitution (p.Leu239Pro) in MAFB, a leucine zipper transcription factor. Luciferase assays with cultured monocytes indicated that the substitution significantly reduced transactivation of the F4/80 promoter, the known MAFB recognition element. Additionally, immunohistochemistry indicated reduced MAFB expression in the podocytes of patients. Structural modeling suggested that the p.Leu239Pro substitution in the DNA-binding domain possibly interferes with the stability of the adjacent zinc finger. Lastly, podocytes in neonatal mice with p.Leu239Pro displayed impaired differentiation. Thus, MAFB mutations impair development and/or maintenance of podocytes, abducens neurons and the inner ear. The interactions between MAFB and regulatory elements in these developing organs are likely highly specific based on spatiotemporal requirements.

Impact of the new risk stratification in the 2011 Japanese Society of Nephrology clinical guidelines for IgA nephropathy on incidence of early clinical remission with tonsillectomy plus steroid pulse therapy.

BACKGROUND: In 2011, the Japanese Society of Nephrology (JSN) published new clinical guidelines for IgA nephropathy (IgAN) with a new risk stratification based on clinical and histological severity. For classification, patients are divided into four groups (low, medium, high, and very high risk). However, differences in responsiveness to each treatment among different groups remain unclear. We evaluate the responsiveness of tonsillectomy plus steroid pulse (TSP) therapy using the new risk stratification. METHODS: We retrospectively reviewed 111 IgAN patients with TSP therapy between January 2003 and January 2013. Study patients were divided into three groups [low- (n = 40), medium- (n = 43) and high-/very high-risk group (n = 28)]. The primary outcome was clinical remission (CR). The observation period was 1 year following tonsillectomy. RESULTS: 57 out of 111 patients (51.4 %) reached CR. The CR incidence was 70.0, 41.9 and 39.3 % (the low-, the medium- and the high-/very high-risk group, respectively). The incidence of CR was significantly higher in the low-risk group (P = 0.013). In a multivariate logistic regression analysis, both the medium- and the high-/very high-risk group showed significantly lower incidence of inducing CR than the low-risk group [(odds ratio 0.324; 95 % confidence interval 0.106-0.939, P = 0.041) (odds ratio 0.239; 95 % confidence interval 0.058-0.910, P = 0.040), respectively]. CONCLUSIONS: The new risk stratification in the 2011 JSN clinical guidelines for IgAN had a positive impact on early CR of TSP therapy.

Comparison of Renal Outcome among Japanese Patients with or without Microangiopathic Hemolysis in Malignant Phase Hypertension: A Single-Center Retrospective Study.

BACKGROUND/AIMS: Although microangiopathic hemolysis (MAH) is a well-known complication of malignant phase hypertension (MPH), only less data on whether MAH in MPH predicts renal outcome exist. Therefore, we evaluated whether MAH was associated with the renal outcome in patients with MPH. METHODS: We conducted a single-center, retrospective, cohort study. Data from 35 patients diagnosed with MPH between October 1998 and January 2015 were analyzed. MPH was defined as the presence of a diastolic blood pressure of ≥120 mm Hg and grades III/IV hypertensive retinopathy according to the Keith-Wagener-Barker classification. MAH was defined as the presence of a low platelet count (<150 × 109/L) together with either an elevated level of lactate dehydrogenase (LDH; >220 U/L), or the presence of schistocytes, or both and the normalization of platelet and LDH level or schistocyte levels after adequate blood pressure control was achieved. The primary outcome was dialysis induction. RESULTS: Fifteen patients had MAH. Those with MAH had significantly severe renal dysfunction at the onset of MPH. The length of follow-up (median, interquartile range) of patients with MAH and those without MAH were 30 (16-94) and 48 (25-115) months, respectively. Dialysis was induced in 9 of 15 patients with MAH and in 6 of 20 patients without MAH. Renal survival in patients with MAH was worse than that in those without, but this was not statistically significant (p = 0.08). By multivariate Cox regression analysis, MAH was not shown to contribute to dialysis induction. CONCLUSION: MAH did not predict renal outcome in MPH.

Collagenofibrotic glomerulopathy with a widespread expression of type-V collagen.

Collagenofibrotic glomerulopathy is considered as a form of glomerulopathy in which organized collagen type III progressively deposits. We report a case of this disease with widespread expression of collagen type V. A 65-year-old woman was admitted to our hospital for further evaluation of nephrotic-range proteinuria. The patient had had anemia and hypertension for 9 years, and proteinuria for 3 years. A renal biopsy specimen showed a remarkable mesangial expansion with Congo red-negative and periodic acid-Schiff-positive deposits. At the ultrastructural level, two forms of bundling fibers were found in the mesangium and subendothelial side of the glomerular basement membranes (GBM). The GBM itself appeared normal. Immunohistochemical investigation showed that the glomerular lesions were strongly reactive with both anti-collagen type-III and -V antibodies. Immunoelectron microscopy demonstrated collagen type V in both forms of bundling fibers. Despite therapy, her renal function declined. The clinical course and renal pathology of this case were in accordance with collagenofibrotic glomerulopathy except for the widespread expression of collagen type V. Collagen type V is a fibrillar collagen capable of forming banding fibrils. This report poses the question whether collagen type V accumulates only in this particular case or whether it is a normal component in collagenofibrotic glomerulopathy.

Aldosterone mediates glomerular inflammation in experimental mesangial proliferative glomerulonephritis.

BACKGROUND: The renoprotection of the mineralocorticoid receptor antagonist (MRA) is considered to be mainly via its antifibrotic activity, and the possibility that it may also have antiinflammatory effects has not been studied. We tested the hypothesis that MRA might influence the inflammatory changes that accompany experimental glomerular injury. METHODS: Administration of vehicle (control) or a selective MRA, eplerenone (50 mg/kg x 2 times/day) was started 7 days (-7d) before induction of anti-Thy-1.1 glomerulonephritis. Kidney samples were evaluated serially over a 12-day period for the presence of cell proliferation, macrophage infiltration, mesangial cell phenotypic activation and expression of the chemokine monocyte chemoattractant protein-1 (MCP-1). RESULTS: MRA did not prevent the mesangiolysis associated with anti-Thy-1 antibody. However, MRA significantly inhibited MCP-1 expression, glomerular macrophage infiltration and mesangial phenotypic activation (alpha-smooth muscle actin expression). CONCLUSION: MRA alters glomerular inflammation and mesangial cell activation in experimental glomerular injury. MRA may be a novel way to treat acute glomerular diseases.

Losartan preserves glomerular basement membrane anionic charge sites in a rat model of nephropathy.

BACKGROUND: Disruption of the size and charge selectivity of the glomerular basement membrane (GBM) leads to proteinuria. Blood pressure medications suppress proteinuria by preserving GBM function. We investigated the mechanism of losartan, an angiotensin II receptor blocker (ARB), in a rat model of nephropathy. METHODS: Male Wistar rats were given 25 mg/kg per day of losartan or the same volume of saline (control) from 5 days before, to 14 days after, induction of nephropathy by injection of puromycin aminonucleoside (PAN). Serum blood urea nitrogen (BUN) and creatinine, blood pressure, urinary protein, glomerular morphology and the number of GBM anionic sites were measured in the 2 groups on days 0, 7 and 14. RESULTS: The losartan group had significantly lower urinary protein on days 7 and 14, and higher BUN on day 14, but there were no significant differences between the losartan and control groups in serum creatinine or blood pressure. Light microscopy indicated reduced mesangial cell proliferation and expansion of the mesangial area in the losartan group relative to controls. There were more GBM anionic sites in the losartan group on days 7 and 14. In addition, all anionic sites on the surface of foot processes of epithelial cells disappeared in the control group but remained in the losartan group. CONCLUSIONS: A rat model of nephropathy indicates that losartan reduces urinary protein and preserves the number of anionic sites on the GBM, but has no apparent effect on hemodynamics.

Actin -related protein 3 (Arp3) is mutated in proteinuric BUF/Mna rats.

The BUF/Mna strain of rat is a model of focal and segmental glomerulosclerosis (FSGS) in which a quantitative trait locus (QTL) for proteinuria, Pur1, has been identified. The aim of the present study was to identify candidates for the Pur1 gene. To narrow the Pur1 QTL, we performed fine QTL mapping and single nucleotide polymorphism (SNP) genotyping. To identify candidate genes, sequencing and gene-expression analyses of all genes contained in the narrowed locus were conducted. The narrowed Pur1 region contained 25 genes. Among these genes, only the Arp3 gene was mutated in the BUF/Mna strain; it contained a missense mutation that caused an (L)111(F) substitution. This leucine is conserved across species. Gene-expression analysis failed to identify any other candidate genes for Pur1. Arp3-mediated actin assembly abnormalities were visible in immunohistochemical and electron microscopic examinations of podocytes in old BUF/Mna rats. Taken together, these data suggest that Arp3 is a candidate for the Pur1 gene. This observation is consistent with our growing recognition that abnormal signaling-induced assembly of actin in podocytes leads to the development of FSGS.

Heparan sulfate of perlecan is involved in glomerular filtration.

Perlecan is a heparan sulfate proteoglycan and a major component of the glomerular basement membrane. To understand the role of heparan sulfate chains of perlecan in glomerular filtration, detailed analyses were performed of the kidneys of Hspg2(Delta)(3/)(Delta)(3) mice, whose perlecan lacks heparan sulfate attachment sites in N-terminal domain I. Macroscopic, histologic, and electron microscopic observations, as well as immunohistochemical and immunoelectron microscopic analyses using specific antibodies against perlecan and agrin core proteins, revealed no significant abnormalities in these mice under physiologic conditions. Polyethyleneimine staining demonstrated no significant changes in charge density in the glomerular basement membrane. Transcripts of other heparan sulfate proteoglycans, agrin, and collagen type XVIII, as well as perlecan, were expressed at similar levels to those in the wild-type littermates. Approximately 40% of the perlecan synthesized by Hspg2(Delta)(3/)(Delta)(3) fibroblasts was substituted with heparin sulfate and 60% was substituted with chondroitin sulfate. All of the perlecan synthesized by wild-type fibroblasts contained heparin sulfate, indicating an altered substitution of glycosaminoglycans on Hspg2(Delta)(3/)(Delta)(3) perlecan. Immunostaining indicated that the level of chondroitin sulfate was actually increased in the Hspg2(Delta)(3/)(Delta)(3) glomerular basement membrane. When administered intraperitoneally with BSA, Hspg2(Delta)(3/)(Delta)(3) mice exhibited remarkable proteinuria. These findings suggest that heparan sulfate chains of perlecan play an important role in glomerular filtration, especially of a large amount of protein.

Smooth-muscle calponin in mesangial cells: regulation of expression and a role in suppressing glomerulonephritis.

The basic or h1 calponin gene, which encodes an actin-binding protein involved in the regulation of smooth-muscle shortening velocity, is known to be a smooth-muscle differentiation-specific gene. It was found that basic calponin was expressed by cultured mesangial cells and localized along the actin filaments. Among the growth factors involved in the mesangial cell pathophysiology, including platelet-derived growth factor-BB (PDGF-BB), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta1 (TGF-beta1), TNF-alpha potently downregulates basic calponin expression in both the mRNA and protein levels, whereas TGF-beta1 upregulates the calponin expression. PDGF-BB also reduced its mRNA expression. The half-life of basic calponin mRNA was determined to be similar between TNF-alpha-treated and -untreated mesangial cells, whereas cell transfection assays that used a luciferase reporter gene construct containing the functional basic calponin promoter showed that TNF-alpha and PDGF-BB reduced the transcriptional activity. Because stimulation with TNF-alpha and PDGF-BB was associated with mesangial cell proliferation, basic calponin may play a role in the suppression of mesangial cell proliferation. Treatment with anti-glomerular basement membrane antibody in calponin knockout mice induced more severe nephritis than in wild type mice, as judged from an increase in the urinary protein excretion, glomerular cellularity, and number of proliferating cell nuclear antigen-positive cells in glomerulus. These results suggest that basic calponin expression may serve as one of the intrinsic regulators of glomerular nephritis. Elucidation of the molecular mechanisms for regulation of the basic calponin expression in mesangial cells may improve the understanding of the molecular basis and pathogenesis of the glomerular response to injury.