Suplatast Tosilate and Eicosapentaenoic Acid as a Possible Strategy for Maintaining Remission in Minimal Change Nephrotic Syndrome: A Case Report

We report a case of a sudden onset of minimal change nephrotic syndrome (MCNS) in a 33-year-old woman with type 1 diabetes mellitus (T1DM), stable microalbuminuria, and chronic thyroiditis. She was successfully treated with intravenous corticosteroids to finally attain a complete remission. Four years later, she also experienced a relapse of MCNS in the same season as the first onset. The chronological levels of serum immunoglobulin E (IgE) showed that extremely high serum IgE levels preceded the onset or the relapse of MCNS, which may suggest an allergic mechanism of MCNS. Eicosapentaenoic acid (EPA) was reported to be beneficial in treating allergic diseases. Suplatast tosilate is an anti-allergic medication that suppresses serum IgE and was reported to be beneficial in reducing corticosteroid dose in nephrotic syndrome in a pilot study. Therefore, during the tapering of corticosteroids to the relapse of MCNS, suplatast tosilate and EPA were administered, and the IgE levels were considerably controlled. The patient was able to maintain remission even after the cessation of corticosteroids. In conclusion, suppressing IgE levels using suplatast tosilate and EPA may be beneficial in maintaining complete remission without corticosteroids in T1DM.

Efficacy of comprehensive group-based education in lowering body weight, uric acid levels, and diuretic use in patients with chronic kidney disease: a retrospective study

BACKGROUND

Patient education for the management of chronic kidney disease (CKD) is attracting attention. Therefore, this study aimed to analyze changes in body weight, uric acid, and estimated-glomerular filtration rate (eGFR) in patients with CKD after a group-based education during admission.

METHODS

Overall, 157 patients with CKD, who were discharged from the nephrology department of our hospital between January 2015 and October 2019, received group-based education or individual-based education by nurses at admission. Deltas of body weight, uric acid, and eGFR, 6 months from baseline, were compared between group- and individual-based education using the Wilcoxon rank sum test.

RESULTS

In total, 60 patients receiving group-based education (G group, n =35) or individual-based education (I group, n =25) during admission were included in this retrospective study. The patient characteristics at baseline were as follows: age mean, 72 ± SD 9; 16 females and 44 males; body weight, 62 ± 17 kg; eGFR median, 21 (IQR: 14, 29) mL/min/1.73 m2; UA, 7 (6.1, 7.5) mg/dL; and estimated intake of salt 6.9 (6.2, 8.4) g/day. Delta eGFR (mL/min/1.73 m2) was -1 (-3, 3) for G group and -1 (-2.5, 2) for I group (p = 0.8039). Delta body weight (kg) was -0.4 (-1.6, 0) for G group and 0 (-0.45, 0.95) for I group (p = 0.0597). Delta uric acid (mg/dL) was -1.1 (-1.6, 0.1) for G group and -0.2 (-1.1, 0.5) for I group (p = 0.0567). In patients with higher sodium intake (≥ 117.4 mEq/day), delta body weight was significantly lower in the group-based education group than in the individual-based education group (p = 0.0398).

CONCLUSIONS

A comprehensive group-based education in patients with CKD may effectively suppress body weight and uric acid in 6 months along with less frequent diuretic use.

Alcohol Consumption and a Decline in Glomerular Filtration Rate: The Japan Specific Health Checkups Study

Previous studies have reported conflicting results on the clinical impact of alcohol consumption on the glomerular filtration rate (GFR). This retrospective cohort study aimed to assess the dose-dependent association between alcohol consumption and the slope of the estimated GFR (eGFR) in 304,929 participants aged 40-74 years who underwent annual health checkups in Japan between April 2008 and March 2011. The association between the baseline alcohol consumption and eGFR slope during the median observational period of 1.9 years was assessed using linear mixed-effects models with the random intercept and random slope of time adjusting for clinically relevant factors. In men, rare drinkers and daily drinkers with alcohol consumptions of ≥60 g/day had a significantly larger decline in eGFR than occasional drinkers (difference in multivariable-adjusted eGFR slope with 95% confidence interval (mL/min/1.73 m²/year) of rare, occasional, and daily drinkers with ≤19, 20-39, 40-59, and ≥60 g/day: -0.33 [-0.57, -0.09], 0.00 [reference], -0.06 [-0.39, 0.26], -0.16 [-0.43, 0.12], -0.08 [-0.47, 0.30], and -0.79 [-1.40, -0.17], respectively). In women, only rare drinkers were associated with lower eGFR slopes than occasional drinkers. In conclusion, alcohol consumption was associated with the eGFR slope in an inverse U-shaped fashion in men but not in women.

Severe leukocytopenia due to copper deficiency induced by zinc supplementation in a patient on peritoneal dialysis: a case report

Zinc deficiency is one cause of anemia. However, it has been reported that some patients who were treated with zinc supplementation to resolve this anemia subsequently experienced copper deficiency, which lead to continued anemia, as well as leukocytopenia and other symptoms. However, only two patients with copper deficiency induced by zinc supplementation undergoing peritoneal dialysis have been reported. Here, we report the case of a 59 year-old man with copper deficiency after zinc supplementation undergoing peritoneal dialysis (PD). He took meals only once a day and drank about 750 mL/day of wine every day. He had been receiving zinc supplementation for 4 months. He was diagnosed with severe leukocytopenia and worsening anemia at a planned outpatient visit; in addition, his copper levels had markedly decreased. Thus, zinc supplementation was discontinued, and the patient was instructed to take cocoa for copper supplementation. Because of severe leukocytopenia, he was admitted to our hospital, and granulocyte colony-stimulating factor was administered. Red blood cell transfusions were performed for anemia. After discontinuing zinc supplementation, his white blood cell count and hemoglobin levels improved.To avoid Cu deficiency, patients' dietary history should be checked in detail and Cu should be monitored carefully when Zn is supplemented in patients undergoing PD.

Tolvaptan Reduces Extracellular Fluid per Amount of Body Fluid Reduction Less Markedly than Conventional Diuretics

Objective Tolvaptan, a vasopressin V2 receptor antagonist, is a water diuretic, removing electrolyte-free water from the kidneys and affecting the water balance between the intracellular and extracellular fluid. We previously reported that tolvaptan efficiently reduced the intracellular fluid volume, suggesting its utility for treating cellular edema. Furthermore, tolvaptan is known for its low incidence of worsening the renal function, with conventional diuretics use associated with worsening of the renal function Methods In this retrospective observational study, five chronic kidney disease (CKD) patients with fluid retention were assessed by the bioelectrical impedance (BIA) method twice (before and after tolvaptan therapy). Tolvaptan was used with conventional diuretics. The post/pre ratio of extracellular water (ECW)/total body water (TBW) in the tolvaptan group was compared with that in 18 CKD patients undergoing body fluid reduction with conventional diuretics alone (conventional diuretics groups), taking the reduced amount of body fluid into consideration. Results Removing body fluid, either by tolvaptan or by conventional diuretics alone, decreased the ECW/TBW ratio. Of note, the reduction in extracellular fluid was milder in the tolvaptan group than in the conventional diuretics group. Conclusion Tolvaptan reduces the extracellular fluid per amount of body fluid reduction less markedly than conventional diuretics.

A Formula for the Estimation of 24-Hour Urinary Creatinine Excretion: A Derivation and Validation Study

OBJECTIVE

Twenty-four-hour urinary creatinine (Cr) excretion (24h-uCr) is the basis of Cr clearance and urinary protein-Cr ratio, and it is related to frailty, worsening kidney function, and mortality in patients with chronic kidney disease. Although subjects with lower estimated glomerular filtration rate (eGFR) tend to have lower 24h-uCr, previous formulae for the estimation of 24h-uCr did not include Cr as a predictor.

METHODS

This retrospective study included patients admitted to the Department of Nephrology at our hospital (derivation cohort and validation cohort: patients admitted between April 2016 and March 2020). The prediction formula of 24h-uCr was calculated using a multivariate linear regression model with the bootstrap method. Age, height, weight, sex, Cr, and cystatin C were used as predictors.

RESULTS

The derivation and validation cohorts included 187 and 63 patients, respectively. The characteristics of the derivation and validation cohorts were as follows: age 73 (61-79.5) years and 70 (58.5-79) years; males, 61.5% and 60.3%; eGFR_Cr 27.0 (13.7-48.6) mL/min/1.73 m² and 26.3 (14.0-51.5) mL/min/1.73 m²; and 24-hour urinary protein excretion 0.79 (0.17-2.12) g/day and 1.08 (0.26-2.55) g/day, respectively. Seven prediction formulae were derived. In all models, the Pearson's correlation coefficient was relatively high and statistically significant. However, previous models tended to overestimate the 24h-uCr. Furthermore, the predicted 24h-uCr calculated by the models that do not include Cr as a predictor fluctuates depending on the eGFR_Cr.

CONCLUSION

The best formula for predicting 24h-uCr (mg/day) in a wide range of eGFR populations is a Cr-containing formula: [-9.04 × age (years) + 8.03 × weight (kg) + 0.66 × height (cm) + 188.59 (if male) - 32.11 × Cr (mg/dL) + 779.14].

User of angiotensin-converting-enzyme inhibitor and/or angiotensin II receptor blocker might be associated with vascular calcification in predialysis chronic kidney disease patients: a retrospective single-center observational study : ACEI/ARB and vascular calcification

Background

Vascular calcification is a prominent feature in chronic kidney disease (CKD) and diabetes mellitus. A recent report suggests that angiotensin II is protective to vascular calcification. Therefore, we investigated the relationship between vascular calcification and use of angiotensin-converting-enzyme inhibitor (ACEI) and/or angiotensin II receptor blocker (ARB) from a cross-sectional view.

Methods

A total of 121 predialysis CKD patients (age 71 ± 12 y; male 72; estimated glomerular filtration rate (eGFR) 20.2 (11.8 - 40.3) mL/min/1.73 m²) who underwent thoracoabdominal plain computed tomography scan were included in this study. The total vascular calcification volume (Calc) was calculated with a three-dimensional imaging software and standardized by body surface area (BSA). The relevance between log [Calc/BSA] and ACEI/ARB use was investigated by multivariate linear regression analyses with or without a time-duration factor of ACEI/ARB use.

Results

The Calc/BSA was 5.62 (2.01 - 12.7) mL/m² in 121 patients. In multivariate analyses adjusted with age, sex, ACEI/ARB and log [eGFR], ACEI/ARB use is significantly and positively associated with log [Calc/BSA] (β = 0.2781, p = 0.0007). Even after the adjustment by age, sex, log [eGFR], phosphate, diabetes mellitus, systolic blood pressure, warfarin, hypertension, dyslipidemia, low-density lipoprotein cholesterol, diuretics and ACEI/ARB, ACEI/ARB use is significantly and positively associated with log [Calc/BSA] (β = 0.1677, p = 0.0487). When 90 patients whose time-duration of ACEI/ARB use was clear in medical records were studied, a multivariate analysis adjusted with age, sex, log [eGFR], and ACEI/ARB duration factors showed that the longer use of ACEI/ARB more than 2 years was significantly, independently and positively associated with log [Calc/BSA] (β = 0.2864, p = 0.0060).

Conclusions

ACEI/ARB user was associated with vascular calcification in predialysis patients with low eGFR. Prospective studies with larger numbers of patients or more in vitro studies are needed to confirm whether this phenomenon is due to the use of ACEI/ARB itself, the underlying disease condition or the prescription bias.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-020-02198-6.

Lactate predicts the 28-day survival rate in patients with septic shock treated with the combination of PMX-DHP and rTM

We have previously reported that combination therapy with polymyxin-B direct hemoperfusion (PMX-DHP) and recombinant thrombomodulin (rTM) is effective in patients with septic shock accompanied by disseminated intravascular coagulation (DIC). Two previous studies reporting the favorable effect of early initiation of PMX-DHP for septic shock did not focus on the combination therapy of PMX-DHP and rTM. This retrospective study included 47 consecutive patients who underwent the combination therapy of PMX-DHP and rTM for septic shock with DIC from August 2011 to August 2016. Main exposure was early or late initiation of PMX-DHP. PMX-DHP initiated within 12 hours after catecholamine administration was designated as early group (N = 25) and later than 12 hours as late group (N = 22). Main outcome was 28-day survival rate. The patient characteristics were age median 73 (IQR 68-78) years, 26 men (55%), APACHE II score 32.7 ± 7.7 and lactate 26.0 (18.0-41.0) mg/dL. The 28-day survival rate after PMX-DHP initiation was 76.6% and was not significantly different in the two groups. In the early group, APACHE II score was lower (P = .02), and lactate was higher (P = .005) than in the late group. Lactate was the only predictor of 28-day mortality [odds ratio (95%CI) per 1 mg/dL, 1.08 (1.03-1.19); P = .037] in multivariate logistic regression analysis adjusted with age, sex, APACHE II score, lactate and timing of PMX-DHP initiation. Late PMX-DHP initiation did not lead to statistically worse 28-day survival rate in this combination therapy. The combination therapy of PMX-DHP and rTM may improve the therapeutic effect of PMX-DHP and modify the effect of early PMX-DHP on the prognosis. Lactate may be an appropriate indicator rather than time after catecholamine administration if we discuss when to start PMX-DHP in this combination therapy.

Tolvaptan Efficiently Reduces Intracellular Fluid: Working Toward a Potential Treatment Option for Cellular Edema

Objective Tolvaptan is a class of diuretics that reduce body water through aquaresis. One of the most prominent characteristics of these agents is that worsening of the renal function is less likely to occur. We investigated the underlying mechanism concerning the change in the intracellular fluid (ICF) when the body fluid is reduced. Methods In this retrospective observational study, five overhydrated chronic kidney disease (CKD) patients with edema or pleural effusion treated with tolvaptan were assessed by the bioelectrical impedance method twice: once before and once after tolvaptan therapy. The changes in the ICF rate were compared with those in 11 hemodialysis patients undergoing body fluid reduction by hemodialysis. Results Removal of the body fluid either by tolvaptan or by hemodialysis increased the post/pre-ratio of ICW/total body water (TBW). Tolvaptan reduced the ICF more efficiently than hemodialysis. Conclusion Tolvaptan treatment lessens body fluid by the efficient reduction of the ICF.

Difference in IgA1 O-glycosylation between IgA deposition donors and IgA nephropathy recipients

IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis, and disease recurrence often occurs after transplantation. On the other hands, Asymptomatic IgA deposition (IgAD) is occasionally observed in donated kidney. It is recognized that IgAD does not progress to IgAN, but the mechanism has not demonstrated yet. In IgAN, aberrant IgA1 O-glycan structure in the hinge region (HR) of serum IgA is suggested as one of the most convincing key mediators. However, little is known about IgA1 O-glycan structure in IgAD patients. Herein, we investigated the prevalence of IgAD in living renal transplant donors in our cohort. IgAD was observed in 21(13.0%) among 161 renal transplant donors and have statistically significant blood relationship with IgAN recipients (28.6% in relatives vs. 9.8% in non-relatives, respectively; p = 0.0073). Next, we evaluated the IgA1 O-glycan structure of serum IgA from IgAN recipients (n = 26), IgAD donors (n = 17), and non-IgAD helthy donors (n = 27) using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The numbers of GalNAc and Gal and the Gal/GalNAc ratio in the HR of the IgAN recipients had significantly lower comparing to the IgAD and non-IgAD healthy donors. The decreased Gal/GalNAc ratio in IgAN recipients means the increased ratio of galactose-deficient IgA1. To the best of our knowledge, this is the first report to compare the O-glycan structures in IgAN recipients and IgAD donors using MALDI-TOF MS. We concluded that IgAD was more common in IgAN related donors. Overall, decreased GalNAc and Gal contents in HR could play a material pathogenic role in IgAN.

Tolvaptan promotes urinary excretion of sodium and urea: a retrospective cohort study

BACKGROUND

Tolvaptan (TLV) promotes aquaresis; however, little is known about its effect on solute excretion in chronic kidney disease (CKD).

METHODS

We retrospectively studied CKD patients with decompensated heart failure (HF) or those with autosomal dominant polycystic kidney disease (ADPKD) receiving TLV. Patients with an increased urine volume of more than twice of daily variance were defined as "responders" in HF. We compared the ability of the urinary osmolality (U-OSM) change and urinary creatinine concentration ([U-Cr]) change to discriminate "responders". The fractional excretion of sodium (FeNa) and urea nitrogen (FeUN), and blood urea nitrogen (BUN) were monitored.

RESULTS

In 30 responders among 53 HF patients, TLV increased FeUN significantly from 36.1 to 44.2% after starting TLV, but not FeNa. Since U-OSM is determined partially by urinary UN concentration, the decrease of [U-Cr] after treatment outperformed the U-OSM decrement to discriminate responders, as shown in receiver operating characteristic curve analysis and significantly higher net reclassification index. In 13 ADPKD patients, TLV increased FeUN (34.8, 47.3%, p = 0.02), and significant decrease of BUN by 2.3 (95% confidence interval 0.4-4.2) mg/dL was observed even 3 months after the intervention. Systolic blood pressure decreased significantly by 14.2 (95% confidence interval 4.0-24.4) mmHg along with the increase in FeNa, leading to reduced dosage of antihypertensives in 6 patients.

CONCLUSION

TLV promotes the excretion of sodium and urea. The change in [U-Cr] is useful for early discrimination of responders. Hypotension should be carefully monitored during high-dose TLV therapy.

Magnesium modifies the association between serum phosphate and the risk of progression to end-stage kidney disease in patients with non-diabetic chronic kidney disease

It is known that magnesium antagonizes phosphate-induced apoptosis of vascular smooth muscle cells and prevents vascular calcification. Here we tested whether magnesium can also counteract other pathological conditions where phosphate toxicity is involved, such as progression of chronic kidney disease (CKD). We explored how the link between the risk of CKD progression and hyperphosphatemia is modified by magnesium status. A post hoc analysis was run in 311 non-diabetic CKD patients who were divided into four groups according to the median values of serum magnesium and phosphate. During a median follow-up of 44 months, 135 patients developed end-stage kidney disease (ESKD). After adjustment for relevant clinical factors, patients in the lower magnesium-higher phosphate group were at a 2.07-fold (95% CI: 1.23-3.48) risk for incident ESKD and had a significantly faster decline in estimated glomerular filtration rate compared with those in the higher magnesium-higher phosphate group. There were no significant differences in the risk of these renal outcomes among the higher magnesium-higher phosphate group and both lower phosphate groups. Incubation of tubular epithelial cells in high phosphate and low magnesium medium in vitro increased apoptosis and the expression levels of profibrotic and proinflammatory cytokine; these changes were significantly suppressed by increasing magnesium concentration. Thus, magnesium may act protectively against phosphate-induced kidney injury.

Urine osmolarity predicts the body weight-reduction response to tolvaptan in chronic kidney disease patients: a retrospective, observational study

BACKGROUND/AIMS

Tolvaptan, a vasopressin V2 receptor antagonist, promotes the excretion of electrolyte-free water. Patients with heart failure or liver cirrhosis, whose urine osmolarity is high due to increased vasopressin, show a good response to tolvaptan; however, it remains dubious whether tolvaptan is also effective in patients with low urine osmolarity due to decreased renal function. The aim of this study was to investigate whether urine osmolarity predicts the effect of tolvaptan in patients with decreased renal function.

METHODS

In this retrospective, observational study, 17 overhydrated chronic kidney disease patients with heart failure or liver cirrhosis who were admitted to Osaka University Hospital were included. They were treated with sodium-excreting diuretics first, and then tolvaptan was added. The clinically relevant parameters were evaluated before and after the use of tolvaptan, and they, including urine osmolarity before use of tolvaptan, were compared between the responder group and the non-responder group. The definition of responder was based on the decrease of body weight by ≥5% in one week, which is a more rigorous indicator of the effectiveness of tolvaptan than the increase in urine output.

RESULTS

The parameter that showed a significant difference between the responder and non-responder groups was urine osmolarity before the use of tolvaptan. The cut-off point derived from the receiver operating characteristic (ROC) curve analysis was 279 mOsm/kg H2O, with sensitivity of 0.86 and specificity of 0.80.

CONCLUSIONS

In patients with decreased renal function, urine osmolarity before the use of tolvaptan predicted the effectiveness of diuretics in terms of body weight reduction.

Minimal Change Nephrotic Syndrome Which Was Most Likely Caused by Chronic Sinusitis

A 33-year-old Japanese man was admitted with severe edema, and a renal biopsy confirmed minimal change nephrotic syndrome (MCNS). CT revealed his severe chronic sinusitis, and he first received antimicrobial therapy, which resulted in decreased proteinuria. The surgical operation for sinusitis resulted in the complete disappearance of proteinuria without corticosteroid or immunosuppressant therapy within one week. MCNS may be triggered by infection, but there are no previously reported cases of MCNS that is completely remitted by infection control alone. Therefore, we herein report the first case of MCNS that attained complete remission following therapy for chronic sinusitis alone, which suggests a strong etiology of chronic sinusitis for MCNS.

Autophagic clearance of mitochondria in the kidney copes with metabolic acidosis

Metabolic acidosis, a common complication of CKD, causes mitochondrial stress by undefined mechanisms. Selective autophagy of impaired mitochondria, called mitophagy, contributes toward maintaining cellular homeostasis in various settings. We hypothesized that mitophagy is involved in proximal tubular cell adaptations to chronic metabolic acidosis. In transgenic mice expressing green fluorescent protein-tagged microtubule-associated protein 1 light chain 3 (GFP-LC3), NH4Cl loading increased the number of GFP puncta exclusively in the proximal tubule. In vitro, culture in acidic medium produced similar results in proximal tubular cell lines stably expressing GFP-LC3 and facilitated the degradation of SQSTM1/p62 in wild-type cells, indicating enhanced autophagic flux. Upon acid loading, proximal tubule-specific autophagy-deficient (Atg5-deficient) mice displayed significantly reduced ammonium production and severe metabolic acidosis compared with wild-type mice. In vitro and in vivo, acid loading caused Atg5-deficient proximal tubular cells to exhibit reduced mitochondrial respiratory chain activity, reduced mitochondrial membrane potential, and fragmented morphology with marked swelling in mitochondria. GFP-LC3-tagged autophagosomes colocalized with ubiquitinated mitochondria in proximal tubular cells cultured in acidic medium, suggesting that metabolic acidosis induces mitophagy. Furthermore, restoration of Atg5-intact nuclei in Atg5-deficient proximal tubular cells increased mitochondrial membrane potential and ammoniagenesis. In conclusion, metabolic acidosis induces autophagy in proximal tubular cells, which is indispensable for maintaining proper mitochondrial functions including ammoniagenesis, and thus for adapted urinary acid excretion. Our results provide a rationale for the beneficial effect of alkali supplementation in CKD, a condition in which autophagy may be reduced, and suggest a new therapeutic option for acidosis by modulating autophagy.

Periodontal disease bacteria specific to tonsil in IgA nephropathy patients predicts the remission by the treatment

Background

Immunoglobulin (Ig)A nephropathy (IgAN) is the most common form of primary glomerulonephritis in the world. Some bacteria were reported to be the candidate of the antigen or the pathogenesis of IgAN, but systematic analysis of bacterial flora in tonsil with IgAN has not been reported. Moreover, these bacteria specific to IgAN might be candidate for the indicator which can predict the remission of IgAN treated by the combination of tonsillectomy and steroid pulse.

Methods and Findings

We made a comprehensive analysis of tonsil flora in 68 IgAN patients and 28 control patients using Denaturing gradient gel electrophoresis methods. We also analyzed the relationship between several bacteria specific to the IgAN and the prognosis of the IgAN. Treponema sp. were identified in 24% IgAN patients, while in 7% control patients (P = 0.062). Haemophilus segnis were detected in 53% IgAN patients, while in 25% control patients (P = 0.012). Campylobacter rectus were identified in 49% IgAN patients, while in 14% control patients (P = 0.002). Multiple Cox proportional-hazards model revealed that Treponema sp. or Campylobactor rectus are significant for the remission of proteinuria (Hazard ratio 2.35, p = 0.019). There was significant difference in remission rates between IgAN patients with Treponema sp. and those without the bacterium (p = 0.046), and in remission rates between IgAN patients with Campylobacter rectus and those without the bacterium (p = 0.037) by Kaplan-Meier analysis. Those bacteria are well known to be related with the periodontal disease. Periodontal bacteria has known to cause immune reaction and many diseases, and also might cause IgA nephropathy.

Conclusion

This insight into IgAN might be useful for diagnosis of the IgAN patients and the decision of treatment of IgAN.

Retention of fetuin-A in renal tubular lumen protects the kidney from nephrocalcinosis in rats

The serum glycoprotein fetuin-A is an important inhibitor of extraosseous calcification. The importance of fetuin-A has been confirmed in fetuin-A null mice, which develop widespread extraosseous calcification including the kidney. However, the mechanism how fetuin-A protects kidneys from nephrocalcinosis remains uncertain. Here, we demonstrate that intratubular fetuin-A plays a role in the prevention of nephrocalcinosis in the proximal tubules. Although normal rat kidney did not express mRNA for fetuin-A, we found punctate immunohistochemical staining of fetuin-A mainly in the S1 segment of the proximal tubules. The staining pattern suggested that fetuin-A passed through the slit diaphragm, traveled in the proximal tubular lumen, and was introduced into proximal tubular cells by megalin-mediated endocytosis. To test this hypothesis, we inhibited the function of megalin by intravenous injection of histidine-tagged soluble receptor-associated protein (His-sRAP), a megalin inhibitor. His-sRAP injection diminished fetuin-A staining in the proximal tubules and led to urinary excretion of fetuin-A. We further analyzed the role of fetuin-A in nephrocalcinosis. Continuous injection of parathyroid hormone (PTH) 1-34 induced nephrocalcinosis mainly in the proximal tubules in rats. His-sRAP retained fetuin-A in renal tubular lumen and thereby protected the kidneys of PTH-treated rats from calcification. Our findings suggest that tubular luminal fetuin-A works as a natural inhibitor against calcification in the proximal tubules under PTH-loaded condition.

Deficiency of N-acetylgalactosamine in O-linked oligosaccharides of IgA is a novel biologic marker for Crohn's disease

BACKGROUND

Ideal biomarkers are required to be developed for the diagnosis and prediction of the treatment of inflammatory bowel disease (IBD). We have reported that alteration of N-linked oligosaccharides of immunoglobulin (Ig) G is a novel diagnostic marker of IBD. Oligosaccharide alterations of IgA, however, have not been investigated in IBD patients.

METHODS

N- and O-linked oligosaccharides of serum IgA purified from 32 patients with Crohn's disease (CD), 30 patients with ulcerative colitis (UC), and 30 healthy volunteers (HV) were analyzed with high-performance liquid chromatography and mass spectrometry. Enzymes related to oligosaccharide attachment were investigated.

RESULTS

N-linked oligosaccharides of IgA were not different between IBD and HV. In contrast, the number of N-acetylgalactosamines per hinge glycopeptide (GalNAc/HP) in the O-linked oligosaccharides of IgA was significantly decreased in patients with CD compared with UC and HV. GalNAc/HP had high sensitivity and specificity for discriminating between CD and HV based on receiver operating characteristic analysis. Lower GalNAc/HP was associated with more severe disease activity of CD. Changes in GalNAc/HP levels in 6 weeks after treatment with infliximab were associated with the clinical activity of CD at 30 weeks. GalNAc transferase expression of naïve B cells and extent of GalNAc attachment in IgA were significantly decreased by interleukin-21 in vitro.

CONCLUSIONS

The number of GalNAc attached in the IgA O-linked glycans of CD patients was significantly decreased, and strongly correlated with the clinical activity. Alterations of GalNAc attachment in IgA could be useful as a novel diagnostic and prognostic marker of CD.

Gene polymorphisms contributing to hypertension in immunoglobulin A nephropathy

BACKGROUND

Hypertension, which is affected by genetic and environmental factors, is one of the major risk factors for chronic kidney disease. Identification of the genetic factor contributing to hypertension in patients with chronic kidney disease may potentially refine a therapeutic strategy.

METHODS

In the present multicenter cross-sectional study, 240 patients were eligible (aged 15-50 years with urinary protein ≥0.25 g/day) out of 429 patients who were diagnosed as having immunoglobulin (Ig) A nephropathy (IgAN) by renal biopsy between 1990 and 2005 and enrolled in our previous study, PREDICT-IgAN. The outcome was hypertension defined as ≥140 and/or ≥90 mmHg of systolic and diastolic blood pressure and/or use of antihypertensives at renal biopsy. We assessed associations between hypertension and 28 polymorphisms with the frequency of minor genotype ≥10% among 100 atherosclerosis-related polymorphisms using the Chi-squared test in dominant and recessive models. We identified polymorphisms associated with hypertension in multivariate logistic regression models.

RESULTS

Baseline characteristics: hypertension 36.3%. Among 28 polymorphisms, the Chi-squared test revealed that CD14 (-159CC vs CT/TT, P = 0.03) and ACE (DD vs DI/II, P = 0.03) were significantly associated with hypertension after Bonferroni correction. Multivariate logistic regression models revealed that CD14 -159CC [vs CT/TT, odds ratio (OR) 3.58 (95% confidence interval (CI) 1.66-7.63)] and ACE DD [vs DI/II, OR 4.41 (95% CI 1.80-10.8), P = 0.001] were independently associated with hypertension.

CONCLUSIONS

CD14 C-159T and ACE I/D contributed to hypertension in patients with IgAN.

Self-reported sleep duration and prediction of proteinuria: a retrospective cohort study

BACKGROUND

Although multiple studies have shown that sleep duration is a predictor of cardiovascular diseases and mortality, few studies have reported an association between sleep duration and chronic kidney disease.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

6,834 employees of Osaka University aged 20-65 years who visited Osaka University Healthcare Center for their mandatory annual health examinations between April 2006 and March 2010 and did not have estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2), proteinuria, or treatment for self-reported kidney disease.

PREDICTOR

Self-reported questionnaires about life style, including sleep duration, and blood and urine testing at the first examinations during the study period. An association between sleep duration and outcome was assessed using multivariate Poisson regression models adjusting for clinically relevant factors.

OUTCOME

Time to the development of proteinuria defined as 1+ or higher by dipstick test.

RESULTS

Self-reported baseline sleep duration was 6.0 ± 0.9 hours, which reflected the mean sleep duration during a median of 2.5 (25th-75th percentile, 1.4-3.9) years of the observational period. Development of proteinuria was observed in 550 employees (8.0%). A multivariate Poisson regression model clarified that shorter sleep duration, especially 5 or fewer hours, was associated with the development of proteinuria in a stepwise fashion (vs 7 hours; incidence rate ratios of 1.07 [95% CI, 0.87-1.33; P = 0.5], 1.28 [95% CI, 1.00-1.62; P = 0.05], and 1.72 [95% CI, 1.16-2.53; P = 0.007] for 6, 5, and ≤4 hours, respectively), along with younger age, heavier current smoking, trace urinary protein by dipstick test, higher eGFR, higher serum hemoglobin A(1c) level, and current treatment for heart disease. A stepwise association between shorter sleep duration and the development of proteinuria also was verified in 4,061 employees who did not work the night shift.

LIMITATIONS

Self-reported sleep duration might be biased. Results in a single center should be confirmed in the larger cohort including different occupations.

CONCLUSION

Short sleep duration, especially 5 or fewer hours, was a predictor of proteinuria.

Microarray analysis of tonsils of IgA nephropathy patients

IgA nephropathy (IgAN) is the most common primary glomerulonephritis. Its close relation with the tonsils is well known because tonsillitis sometimes causes aggravation of urinary findings or macrohematuria. However, the genes specific to the tonsils of IgAN patients are not clarified. To clarify the specific gene expression in the tonsils of IgAN patients, we performed tonsillectomy and corticosteroid IV therapy as a treatment of IgAN, analyzed the gene expression in the tonsils by microarray and compared it with that in tonsils from chronic tonsillitis patients. The upregulated genes seem to be categorized into two groups: muscle-related genes and immunerelated genes. The downregulated genes include the polymeric Ig receptor (pIgR) which was reportedly involved in single nucleotide polymorphism (SNP) of Japanese IgAN patients.

Urinary type IV collagen in nondiabetic kidney disease

BACKGROUND

Type IV collagen is one of the major components of basement membrane. In diabetic nephropathy, it is already known that urinary excretion of type IV collagen increases with the disease progression. However, in nondiabetic kidney disease, urinary type IV collagen (u-IVc) levels have not been extensively investigated. The aim of this study was to evaluate u-IVc levels in various nephropathies except diabetic nephropathy.

METHODS

u-IVc levels were measured cross-sectionally from 527 biopsy-proven nondiabetic renal disease patients at tertiary care hospitals by one-step sandwich enzyme immunoassay.

RESULTS

On simple regression analyses, u-IVc levels had positive correlation with age, blood pressure, urinary protein (u-Prot), urinary β(2) microglobulin, urinary N-acetyl-β-D-glucosaminidase, HbA(1)c, and selectivity index (SI), while u-IVc had negative correlation with eGFR and serum albumin. Multiple regression analyses revealed that u-IVc was positively correlated with u-Prot, HbA(1)c and SI. Among biopsy-proven nondiabetic nephropathies, elevation of u-IVc was distinctively observed in membranous nephropathy and anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis.

CONCLUSION

u-IVc levels were elevated with the increase in u-Prot, HbA(1)c and SI. In addition, among nondiabetic kidney disease, elevation of u-IVc was observed in patients with membranous nephropathy and ANCA, which might reflect the thickening of basement membrane or severe kidney damage.

Cigarette smoking and progression of IgA nephropathy

BACKGROUND

Multiple community-based cohort studies of mainly middle-aged and elderly populations have shown that cigarette smoking is a risk factor for chronic kidney disease. However, little information is available about an effect of cigarette smoking on progression of primary kidney diseases, including immunoglobulin A (IgA) nephropathy.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

971 of 1,001 patients with a diagnosis of IgA nephropathy in 3 major nephrology centers in Osaka, Japan, between 1992 and 2005 who enrolled in the Study of Outcome and Practice Pattern of IgA Nephropathy (STOP-IgAN).

PREDICTORS

Smoking status and number of cigarettes smoked at the time of diagnosis using kidney biopsy. Dose-dependent associations between cigarette smoking and outcomes were assessed in multivariate Cox proportional hazards models. Significantly different clinical characteristics between non-/past and current smokers were controlled for using propensity score-based adjustment, stratification, and matching.

OUTCOMES

50% increase in serum creatinine level as primary outcome. A composite outcome of a 100% increase in serum creatinine level or end-stage renal disease (ESRD) and ESRD alone as secondary outcomes.

RESULTS

During the median 5.8 years (interquartile range, 2.6-10.2) of the observational period, 117 participants progressed to a 50% increase in serum creatinine level and 47 advanced to ESRD. Multivariate Cox proportional hazards models identified current smokers (HR, 2.03 [95% CI, 1.33-3.10] for primary outcome) and number of cigarettes at kidney biopsy (HR, 1.21 [95% CI, 1.06-1.39] per 10 cigarettes per day) as significant predictors of outcomes. Propensity score-based models confirmed these results. Tests for interaction showed that the association of current smoking with adverse outcomes was stronger in those with lower compared with higher estimated glomerular filtration rates.

LIMITATION

Baseline smoking status was not verified using biochemical tests. Smoking status during the observational period was unavailable.

CONCLUSIONS

Cigarette smoking, in a dose-dependent manner, was identified as a key prognostic factor in IgA nephropathy. Smoking cessation should be encouraged as part of the treatment for IgA nephropathy.

Kidney repair using stem cells: myth or reality as a therapeutic option?

The kidney has been considered a highly terminally differentiated organ of the body, and its proliferative potential is low, with the result that it has been thought of as a most unlikely organ for regeneration. From the structural point of view, the kidney is elaborately composed of many cell types that function as a tissue unit and not as individual cells, which also makes it more difficult to regenerate. However, in clinical settings, the kidney does have regenerative potential as seen in the recovery from acute kidney injury. The role of bone marrow-derived mesenchymal stromal cells may mainly be to produce humoral factors accelerating regeneration. The origin, localization and role of kidney stem cells are under investigation. We also discuss potential applications of embryonic stem cells and induced pluripotent stem cells in kidney regeneration.

Microarray analysis of tonsils in immunoglobulin A nephropathy patients

BACKGROUND

Recently, combination of tonsillectomy and steroid pulse therapy was reported to be effective as the treatment of the immunoglobulin A nephropathy (IgAN). However, the gene expression difference between the tonsils in patients with IgAN and those in control patients is not established.

METHODS

We performed tonsillectomy combined with steroid pulse as a treatment to IgAN, analyzed the gene expression in the tonsils (N=23) using microarray, compared with those with patients suffering from chronic tonsillitis (N=22). From some candidate genes related with IgAN, we confirmed the apolipoprotein B messenger RNA-editing enzyme catalytic polypeptides 2 (APOBEC2) gene expression in the tonsil and we also analyzed its expression levels and clinical features.

RESULTS

Up-regulated genes seem to be categorized into two groups. One group belongs to the muscle related genes which might be caused by structural differences. The other group includes the immune system-related genes, such as APOBEC2, CALB2, DUSP27, and CXCL11. APOBEC2 was positively stained in the epithelium and the peripheral region of the germinal center in both tonsils. APOBEC2 expression level was negatively related with serum igg level, but did not correlate with clinical course after tonsillectomy.

CONCLUSION

We confirmed gene expression differences related with immune system and muscle structure. The APOBEC2 was confirmed to be elevated in the tonsils with IgAN patients, and the gene expression level was negatively related with serum igg level in overall patients. These results might be helpful to reveal the mechanism of IgAN.

E-cadherin and claudin-4 expression has circadian rhythm in adult rat kidney

BACKGROUND

Urinary sodium excretion varies during the day. It is unknown whether expression levels of cell-cell junctions in the kidney are dynamic and associated with urinary sodium excretion.

METHODS

Adult Sprague Dawley rats were fed ad libitum or exclusively during the day, or kept under fasting condition. We measured expression levels of Per2, E-cadherin and claudin-4 as representative molecules of the peripheral circadian clock, adherens junctions and tight junctions, respectively. We also measured sodium concentration in urine. Effects of aldosterone on expression levels of Per2 and claudin-4 were also studied. To see proliferating cells in the kidney, rats were labeled with 5-bromo-2'-deoxyuridine.

RESULTS

In rats fed ad libitum, Per2, E-cadherin and claudin-4 mRNA showed robust circadian oscillation: the correlation coefficients (R values) of the cosinor fitting curves with a 24-hour cycle were 0.928, 0.999 and 0.983, respectively. Oscillation phases of these molecules shifted in response to restricted feeding (R=0.922, R=0.815 and R=0.821, respectively). E-cadherin and claudin-4 proteins also oscillated circadianly under ad libitum feeding (R=0.851 and R=0.999, respectively), which shifted in response to the restricted feeding (R=0.811 and R=0.985, respectively). Urinary sodium excretion was low when protein levels of E-cadherin and claudin-4 were high. Aldosterone or cell division did not account for mRNA oscillation of claudin-4 or E-cadherin in the kidney.

CONCLUSIONS

Expression of E-cadherin and claudin-4 has a circadian rhythm. The dynamic change in protein levels of E-cadherin and claudin-4 seems to coincide with that in the level of sodium excretion.

Early plasma exchange for progressive liver failure in recipients of adult-to-adult living-related liver transplants

BACKGROUND/AIMS

Little information is available concerning the effectiveness of plasma exchange for progressive liver failure in liver transplant recipients. The aims of the present study were to evaluate the effectiveness of plasma exchange and discuss its indication.

METHODS

Forty-six ABO-compatible recipients of living-related liver transplants operated on in Osaka University hospital were retrospectively studied.

RESULTS

Total bilirubin was identified as the most accurate predictor of the short-term prognosis of 46 recipients (optimal cut-off point: 13.3 mg/dl). Eleven patients received 14 plasma exchange sessions. Elevation of total bilirubin was significantly suppressed after plasma exchange in the patients with total bilirubin below the median (24 mg/dl), whereas total bilirubin significantly increased even after plasma exchange in those with total bilirubin above the median.

CONCLUSION

Plasma exchange improved liver function in recipients with progressive liver failure and appears to be indicated in patients with total bilirubin levels ranging between 13 and 24 mg/dl.

Assessment of coronary stenosis by a 16-slice MDCT scanner in asymptomatic diabetic patients starting dialysis therapy

BACKGROUND

The accuracy for the detection of coronary stenosis by multidetector row computed tomography (MDCT) has been getting more recognition. However, the usefulness of MDCT in patients with chronic kidney disease (CKD) has not been confirmed.

METHODS

Weanalyzed 19 consecutive patients with asymptomatic diabetic CKD who underwent both MDCT and coronary angiography (CAG) at the initiation of dialysis. The definition of stenosis in this study was lesions with > or =50% stenosis by CAG.

RESULTS

CAG revealed stenosis in 35 of 76 branches in 19 patients. Vessel diameter could not be evaluated by MDCT in 11 (14%) major vessels because of motion artifacts, pericardial effusion, pleural effusion, and severe calcification. Almost all of such lesions were located in the right coronary (4/11; 36%) or left circumflex (5/11; 45%) artery. The sensitivity, specificity, positive and negative predictive values of MDCT for a diagnosis of stenosis in the 65 evaluable major vessels were 86, 81, 78, and 88%, respectively. The severity of vessel calcification was increased in a stepwise manner with increments in the proportion of major vessels with > or =50% stenosis (p = 0.004 for trend).

CONCLUSION

MDCT seemed to be an effective non-invasive method of screening patients with diabetic CKD for CAD.

Integrated therapies including erythropoietin decrease the incidence of dialysis: lessons from mapping the incidence of end-stage renal disease in Japan

BACKGROUND

Erythropoietin (EPO) has been reported to slow the decline of renal function in predialysis chronic kidney disease (CKD) patients. On the contrary, in the recent large-scale randomized controlled trial (RCT), CREATE and CHOIR, which aimed to keep a higher haemoglobin (Hb) level than former trials, the renoprotective effect of EPO was not observed. Today, the renoprotective effect of EPO has become controversial. In order to test the hypothesis that the usage of EPO in predialysis CKD patients may ameliorate the progression of renal disease, we conducted a macro-level observational study dealing with all Japanese predialysis CKD patients.

METHODS

Annually since 1982, the Japanese Society for Dialysis Therapy reports the number of patients that have entered maintenance dialysis in each prefecture of Japan. Based on the 2002-2004 data, we calculated the annual incidence of end-stage renal disease (ESRD) in each of the 47 prefectures. The annual amounts paid for EPO by each prefecture, presumably corresponding to the amounts used, corrected for the estimated predialysis CKD patients, were calculated. We examined the relationship between the incidence of new dialysis and the usage of EPO in each prefecture. Furthermore, the usage of EPO was compared with that of antihypertensive agents including angiotensin converting enzyme inhibitor (ACE-I), and that of statin.

RESULTS

There were prefectural differences in the annual incidence of ESRD from 2002 to 2004. We also found prefectural differences in the usage of EPO for the three consecutive years. The usage of EPO in predialysis patients was negatively correlated with the incidence of ESRD on linear and multiple regression analyses. At the same time, the usage of EPO had strong positive correlations with the usage of antihypertensive agents including ACE-I and with that of statin.

CONCLUSION

Our nationwide epidemiologic study revealed that a higher use of EPO was associated with a decreased incidence of new dialysis in daily clinical practice. In addition, there were strong correlations among the usage of EPO, antihypertensive agents and statin. These data are supportive of, but do not prove, the hypothesis that EPO may be renoprotective, when used in combination with other strategies.

Exacerbation of albuminuria and renal fibrosis in subtotal renal ablation model of adiponectin-knockout mice

OBJECTIVE

Obesity is recognized increasingly as a major risk factor for kidney disease. We reported previously that plasma adiponectin levels were decreased in obesity, and that adiponectin had defensive properties against type 2 diabetes and hypertension. In this study, we investigated the role of adiponectin for kidney disease in a subtotal nephrectomized mouse model.

METHODS AND RESULTS

Subtotal (5/6) nephrectomy was performed in adiponectin-knockout (APN-KO) and wild-type (WT) mice. The procedure resulted in significant accumulation of adiponectin in glomeruli and interstitium in the remnant kidney. Urinary albumin excretion, glomerular hypertrophy, and tubulointerstitial fibrosis were significantly worse in APN-KO mice compared with WT mice. Intraglomerular macrophage infiltration and mRNA levels of vascular cell adhesion molecule (VCAM)-1, MCP-1, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, collagen type I/III, and NADPH oxidase components were significantly increased in KO mice compared with WT mice. Treatment of APN-KO mice with adenovirus-mediated adiponectin resulted in amelioration of albuminuria, glomerular hypertrophy, and tubulointerstitial fibrosis and reduced the elevated levels of VCAM-1, MCP-1, TNF-alpha, TGF-beta1, collagen type I/III, and NADPH oxidase components mRNAs to the same levels as those in WT mice.

CONCLUSIONS

Adiponectin accumulates to the injured kidney, and prevents glomerular and tubulointerstitial injury through modulating inflammation and oxidative stress.

Fetal cells in mother rats contribute to the remodeling of liver and kidney after injury

Fetal microchimerism indicates a mixture of cells of maternal and fetal origin seen in maternal tissues during and after pregnancy. Controversy exists about whether persistent fetal microchimerism is related with some autoimmune disorders occurring during and after pregnancy. In the current experiment, an animal model in which EGFP positive cells were taken as fetal-origin cells was designed to detect the fetal microchimerism in various maternal organs. Ethanol drinking and gentamicin injection were adopted to induce liver and kidney injury simultaneously. EGFP positive cells were engrafted not only in the maternal circulation and bone marrow, but also in the liver and kidney as hepatocytes and tubular cells, respectively. These results indicate that fetal cells are engrafted to maternal hematopoietic system without apparent injury and they also contribute to the repairing process of maternal liver and kidney.

Hematopoietic and nonhematopoietic potentials of Hoechst(low)/side population cells isolated from adult rat kidney

BACKGROUND

Although the regenerative stem cell is expected to exist in many adult tissues, the cell contributing to the regeneration of the kidney remains unknown in its type and origin.

METHODS

In this study, we isolated cells that show low stain with a DNA-binding dye Hoechst 33342 (Hoechst(low) cells) from adult rat kidney, and investigated their differentiation potentials.

RESULTS

Hoechst(low) cells, generally termed side population cells, existed at a frequency of 0.03% to 0.1% in the cell suspension of the digested kidney. Analysis of the kidney-derived Hoechst(low) cells after bone marrow transplantation indicated that some of the cells were derived from bone marrow. When enhanced green fluorescent protein (EGFP)-labeled kidney-derived Hoechst(low) cells were intravenously transplanted into wild-type adult rats, EGFP(+) cells were not detected in the kidney, but EGFP(+) skeletal muscle, EGFP(+) hepatocytes and EGFP(+) bone marrow cells were observed. Even after the induction of the experimental glomerulonephritis and gentamicin-induced nephropathy that promote the differentiation of bone marrow-derived cells into repopulating mesangial cells and tubular component cells, respectively, EGFP(+) mesangial or tubular cells were not observed. Neither with an in vitro system, which we established to produce mesangial-like cells from crude bone marrow culture, did Hoechst(low) cells yield mesangial-like cells.

CONCLUSION

These findings implicate that Hoechst(low) cells in the kidney may have potentials for hematopoietic and nonhematopoietic lineages, but are not stem cells for renal cells, especially mesangial and tubular cells.

A case of Wegener?s granulomatosis with pulmonary bleeding successfully treated with double filtration plasmapheresis (DFPP)

We report a case of a 41-year-old Japanese man who presented with rapidly progressive glomerulonephritis, chronic sinusitis, and positive cytoplasmic-antineutrophil cytoplasmic antibody (c-ANCA). Renal biopsy showed crescentic glomerulonephritis, and he was diagnosed as having Wegener's granulomatosis. During the clinical course, he suffered from pulmonary bleeding, and combination therapy of steroid, immunosuppressant, and double filtration plasmapheresis (DFPP) was started. He rapidly entered remission after assistance through DFPP, suggesting the potential efficacy of DFPP for Wegener's granulomatosis, especially with pulmonary bleeding.

Activation of the signal transducer and activator of transcription signaling pathway in renal proximal tubular cells by albumin

Renal proximal tubular cells activated by reabsorption of protein are thought to play significant roles in the progression of kidney diseases. It was hypothesized that the signal transducer and activator of transcription (STAT) proteins may be activated by proteinuria in proximal tubular cells. To test this hypothesis, murine proximal tubular cells were treated with albumin (30 mg/ml medium) for various lengths of time. The results showed that albumin could activate Stat1 and Stat5 within 15 min in proximal tubular cells. The activation of STATs was mediated mostly by Jak2 and required no protein synthesis. In addition, activation of Stat1 occurred even after neutralization of IFN-gamma. The activation of STATs was inhibited by N-acetyl-L-cysteine, a precursor of glutathione and a reactive oxygen species (ROS) scavenger, and fluorescence-activated cell sorter analysis showed upregulation of intracellular ROS after albumin overloading, suggesting that albumin per se could generate ROS in proximal tubular cells. The activation of STATs occurred by way of the ROS generating system, and especially through the membrane-bound NADPH oxidase system. Reduced activities of glutathione peroxidase and catalase could also be responsible for the accumulation of intracellular ROS. Hence, not only the ROS generating system, but also the ROS scavenging system may contribute to the induction of ROS by albumin. These findings support the hypothesis that proximal tubular cells are activated and generate ROS by reabsorption of abundant urinary proteins filtered through the glomerular capillaries, and as a consequence, various IFN-gamma-inducible proteins are synthesized through IFN-gamma-independent activation of STAT signaling.

Platelet-derived growth factor plays a critical role to convert bone marrow cells into glomerular mesangial-like cells

BACKGROUND

Despite increasing interest in bone marrow-derived stem cells, little is known about critical factors that determine their fates both in vitro and in vivo. Recently, we have reported that bone marrow is a reservoir for glomerular mesangial cells in rats. To find a key factor responsible for the differentiation of bone marrow-derived cells into mesangial cells, we established a new culture system of rat bone marrow, which is based on serial replating and differential attachment to collagen types I and IV.

METHODS

Bone marrow cells that did not adhere to collagen type I within 24 hours were transferred to collagen type IV-coated dishes. Then, the cells attached to collagen type IV in the following 24 hours were maintained in the presence of 2% horse serum, 200 ng/mL of platelet-derived growth factor (PDGF)-BB, and 1 micromol/L of all-trans retinoic acid. In vivo effect of PDGF-B was also examined by introducing human PDGF-B gene into glomeruli.

RESULTS

After cultivation under the above condition for 7 days, approximately 14% of cells expressed Thy-1 and desmin, both of which are markers for rat mesangial cells. Thy-1++/desmin+ cells were stellate-shaped, and contracted in response to angiotensin II. When human PDGF-B gene was overexpressed in the glomeruli of chimeric rats whose bone marrow was transplanted from enhanced green florescent protein (EGFP) transgenic rats, the number of EGFP+ mesangial cells increased. This effect was canceled by prior introduction of a neutralizing molecule that is composed of PDGF receptor-beta ligand binding site and IgG-Fc.

CONCLUSION

These results indicate that PDGF-B plays a critical role to direct bone marrow-derived cells toward mesangial-like cells both in vitro and in vivo.