The miR-143/145 cluster induced by TGF-ß1 suppresses Wilms' tumor 1 expression in cultured human podocytes.

Transforming growth factor (TGF)-ß1 contributes to podocyte injury in various glomerular diseases, including diabetic kidney disease, probably at least in part by attenuating the expression of Wilms' tumor 1 (WT1). However, the precise mechanisms remain to be defined. We performed miRNA microarray analysis in a human podocyte cell line cultured with TGF-ß1 to examine the roles of miRNAs in podocyte damage. The microarray analysis identified miR-143-3p as the miRNA with the greatest increase following exposure to TGF-ß1. Quantitative RT-PCR confirmed a significant increase in the miR-143-3p/145-5p cluster in TGF-ß1-supplemented cultured podocytes and demonstrated upregulation of miR-143-3p in the glomeruli of mice with type 2 diabetes. Ectopic expression of miR-143-3p and miR-145-5p suppressed WT1 expression in cultured podocytes. Furthermore, inhibition of Smad or mammalian target of rapamycin signaling each partially reversed the TGF-ß1-induced increase in miR-143-3p/145-5p and decrease in WT1. In conclusion, TGF-ß1 induces expression of miR-143-3p/145-5p in part through Smad and mammalian target of rapamycin pathways, and miR-143-3p/145-5p reduces expression of WT1 in cultured human podocytes. miR-143-3p/145-5p may contribute to TGF-ß1-induced podocyte injury.NEW & NOTEWORTHY This study by miRNA microarray analysis demonstrated that miR-143-3p expression was upregulated in cultured human podocytes following exposure to transforming growth factor (TGF)-ß1. Furthermore, we report that the miR-143/145 cluster contributes to decreased expression of Wilms' tumor 1, which represents a possible mechanism for podocyte injury induced by TGF-ß1. This study is important because it presents a novel mechanism for TGF-ß-associated glomerular diseases, including diabetic kidney disease (DKD), and suggests potential therapeutic strategies targeting miR-143-3p/145-5p.

Clinical differences among patients with myeloperoxidase-antineutrophil cytoplasmic antibody-positive interstitial lung disease.

INTRODUCTION: Patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis and idiopathic interstitial lung diseases (IIPs) are positive for myeloperoxidase (MPO)-ANCA. MPO-ANCA-positive vasculitis mainly comprises microscopic polyangiitis (MPA) and unclassifiable vasculitis. These diseases are frequently complicated by interstitial lung disease (ILD). Few studies have reported the clinical differences between the subtypes of MPO-ANCA-positive ILD. Therefore, this study aimed to examine the clinical findings and courses of MPO-ANCA-positive ILD. METHOD: This retrospective study enrolled 100 patients with MPO-ANCA-positive ILD who were categorized into three groups: MPA (n = 44), unclassifiable vasculitis (n = 29), and IIP (n = 27). Our study compared the clinical findings and prognosis of these patients and analyzed the poor prognostic factors. Furthermore, we assessed the association between the patients with and without acute exacerbation of ILD (AE-ILD). RESULTS: Our study found clinical differences in serum markers, clinical symptoms, and treatment regimens among the three groups. ILD complications, as the main cause of death, differed among the three groups (P = 0.04). Patients with unclassifiable vasculitis showed higher survival rates than those with IIP (P = 0.046). Patients with AE-ILD showed fewer general symptoms (P = 0.02) and lower survival rates (P < 0.01) than those without AE-ILD. In multivariate analysis, AE-ILD development was a strong poor prognostic factor for MPO-ANCA-positive ILD. CONCLUSIONS: The subtypes of MPO-ANCA-positive ILD have different clinical features and prognoses. Patients who develop AE-ILD require careful evaluation of clinical courses. Key Points • In myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA)-positive interstitial lung disease (ILD), patients with unclassifiable vasculitis showed a better prognosis than those with idiopathic ILD.. • Development of acute exacerbation in ILD was a strong poor prognostic factor in patients with MPO-ANCA-positive ILD..

Influence of obesity in interstitial lung disease associated with anti-aminoacyl-tRNA synthetase antibodies.

BACKGROUND: Obesity is a major risk factor for developing various respiratory diseases. Patients with anti-aminoacyl tRNA synthetase (ARS) antibodies often have interstitial lung disease (ILD). The present study was conducted to evaluate the association between obesity and outcomes of anti-ARS antibody-related ILD (ARS-ILD). METHODS: We retrospectively investigated 58 patients with ARS-ILD and compared the clinical characteristics, treatment, and prognoses between obese (body mass index [BMI] ≥25 kg/m2) and nonobese (BMI <25 kg/m2) patients. Chest fat was quantified via computed tomography (CT). Thoracic subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were measured at diagnosis and first relapse of ILD. RESULTS: Sixteen patients were obese. Obese patients had lower percentages of predicted diffusing capacity of the lungs for carbon monoxide and higher high-resolution CT scores and SAT and VAT indexes than did nonobese patients. The ILD relapse rate was higher in obese patients (P < 0.01), especially among those with high SAT indexes (P < 0.01). The SAT and VAT indexes increased significantly from diagnosis until first relapse. Among clinical parameters at first relapse, SAT and VAT indexes were correlated with serum Krebs von den Lungen-6 levels (r = 0.720, P = 0.008) and total ground-glass attenuation scores (r = 0.620, P = 0.024), respectively. CONCLUSIONS: Obesity and high SAT indexes are risk factors for ILD relapse in patients positive for anti-ARS antibodies. Evaluating and quantifying patients' chest fat on CT is important for predicting ILD relapse.

Quantitative CT analysis of interstitial pneumonia in anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis: a single center, retrospective study.

INTRODUCTION: This study aimed to assess the utility of quantitative high-resolution computed tomography (HRCT) for determining the clinical course of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis-associated interstitial lung disease (MDA5+ ILD). METHOD: This study retrospectively analyzed the data of 34 patients with MDA5+ ILD to determine the association between the clinical findings and extent of ILD via quantitative CT analysis at baseline and short-term follow-up. Quantified HRCT scores were evaluated as the lung severity score (LSS), percentage of opacity, and percentage of high opacity. RESULTS: Thirty-four patients underwent follow-up CT scans 35 (range: 14-78) days after diagnosis. Patients who died of rapidly progressive ILD had higher LSS (p < 0.01), percentage of opacity (p < 0.01), percentage of high opacity (p = 0.01), total ground-glass opacity score (p = 0.01), serum C-reactive protein (CRP) (p = 0.03), and alveolar-arterial oxygen difference (Aa-DO2) (p = 0.01) at follow-up than those who survived. Quantified HRCT scores correlated with serum CRP and Aa-DO2 levels at follow-up. LSS at follow-up (AUC = 0.844, p < 0.01) was the best predictor of death in MDA5+ ILD patients. Patients with an LSS of > 6.5 at follow-up had higher mortality than those with an LSS of ≤ 6.5, especially when receiving triple therapy. In multivariate analysis, an LSS of > 6.5 at follow-up was significantly associated with a poor outcome. CONCLUSIONS: Quantitative CT analysis of MDA5+ ILD is useful for the objective assessment of respiratory status and disease activity. Short-term HRCT evaluation, particularly LSS, is most important in predicting its clinical course during triple therapy. Key Points • Quantitative CT analysis plays an important role in evaluating the clinical course of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis-associated interstitial lung disease (MDA5+ ILD). • Quantified HRCT scores, particularly lung severity score, at short-term intervals from diagnosis can help to predict prognosis after triple therapy in MDA5+ ILD.

Primary central nervous system lymphoma in a patient with neuropsychiatric systemic lupus erythematosus receiving mycophenolate mofetil: A case report and literature review.

A 41-year-old woman with a 14-month history of systemic lupus erythematosus (SLE) presented with headache, aphasia, and agraphia. A laboratory examination revealed mild proteinuria, hypocomplementemia, and elevated anti-double-stranded DNA antibody levels. A cerebrospinal fluid analysis demonstrated elevated protein and interleukin-6 levels. Magnetic resonance imaging (MRI) of the brain identified multiple lesions suggestive of brain edemas and small haemorrhages. She was diagnosed as having neuropsychiatric lupus and lupus nephritis and received remission induction therapy with high-dose corticosteroid and intravenous cyclophosphamide. She achieved a complete remission, and treatment with mycophenolate mofetil (MMF) was initiated 3 months thereafter for remission maintenance. At 13 months after the exacerbation of SLE, she complained of headache and nausea. A gadolinium-enhanced MRI of the brain revealed a low-signal-intensity tumour with marginal ring enhancement of 50 mm in the left frontal lobe. The tumour was excised, and the histological diagnosis was diffuse large B-cell lymphoma with positive Epstein-Barr virus (EBV). MMF was discontinued. Remission induction therapy with rituximab, high-dose methotrexate, procarbazine, and vincristine was administered, and she achieved remission. Previous reports suggest that use of MMF is associated with primary central nervous system (CNS) lymphoma (PCNSL) in patients with lupus nephritis or other autoimmune diseases or in post-transplant patients. Our observation that PCNSL occurred after CNS involvement of SLE suggests that EBV and CNS inflammation arising from SLE might have contributed to the development of PCNSL.

Otitis media with ANCA-associated vasculitis: A retrospective study of 30 patients.

OBJECTIVES: Otitis media with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (OMAAV) is a new category of otitis media in which cases of otitis media due to ANCA-associated vasculitis (AAV) are classified, regardless of ANCA variant or ANCA serotype. We aimed to describe the clinical features and course of patients with OMAAV and identify factors associated with hearing outcomes. METHODS: We retrospectively analysed 30 patients with OMAAV, classified based on the criteria proposed by the Japan Otological Society in 2016. RESULTS: Single-positive myeloperoxidase-ANCA, single-positive proteinase 3-ANCA, double-positive ANCA, and double-negative ANCA were identified in 47%, 33%, 7%, and 13% of the patients, respectively. All patients subjected to audiometry showed hearing impairments, and 85% were affected bilaterally. Mixed- and sensorineural-type hearing impairments were identified in 80% and 20% of impaired ears, respectively. Hypertrophic pachymeningitis (HPM) was identified in 37% of the patients. Immunosuppressive therapy was administered to 93% of patients, and the median air conduction hearing levels at pre- and post-treatment were 66.1 dB and 43.4 dB, respectively, indicating significant hearing improvements. HPM and a long interval between disease onset and treatment initiation were significantly correlated with poor hearing prognosis. CONCLUSIONS: OMAAV develops under any type of ANCA-serology and typically causes mixed or sensorineural bilateral hearing loss. The early initiation of immunosuppressive therapy and the absence of HPM were associated with good hearing outcomes.

Pregnancy outcomes in patients with systemic lupus erythematosus with or without a history of lupus nephritis.

BACKGROUND: Pregnancy is an important issue for many women with systemic lupus erythematosus (SLE). This study examined maternal and fetal outcomes among SLE women with or without a history of lupus nephritis (LN). METHODS: We retrospectively analyzed 98 pregnancies in 57 women previously diagnosed with SLE who gave birth at our hospital. RESULTS: There were 44 pregnancies in women with a history of LN and 54 pregnancies in those without. Fetal loss was observed in 16.1% of SLE pregnancies when excluding induced abortion, and preeclampsia and SLE flare were observed in 12.2 and 6.1% of SLE pregnancies, respectively. No significant differences were evident between women with or without LN in rate of fetal loss, preeclampsia or SLE flare. Women with a history of LN exhibited a significantly shorter duration of gestation (37.0 weeks vs. 38.4 weeks, P = 0.006) and lower birth weight (2484 g vs. 2746 g, P = 0.007) than those without LN. Multivariate analysis revealed glucocorticoid dose but not history of LN, as an independent risk factor for preterm delivery and low birth weight. CONCLUSION: This study was unable to conclude that a history of LN predicted pregnancy outcomes among SLE women. Instead, a higher dose of glucocorticoid at conception was unexpectedly associated with preterm delivery and low birth weight. Further studies are awaited to verify the relationship.

Interstitial lung disease with myeloperoxidase-antineutrophil cytoplasmic antibody-associated vasculitis in elderly patients.

Anti-neutrophil cytoplasmic antibodies-associated vasculitis (AAV) occurs in elderly people, and patients with anti-myeloperoxidase autoantibodies (MPO-ANCA)-positive AAV are often complicated with interstitial lung disease (ILD). This study aimed to evaluate the age-related clinical features of elderly patients with MPO-ANCA-positive AAV-ILD. This study retrospectively investigated 63 patients with MPO-ANCA-positive AAV-ILD, all of whom were 65 years or older at diagnosis. Clinical characteristics, causes of death and survival rates among three groups stratified by age (65-74 years, n = 29; 75-79 years, n = 18; over 80 years, n = 16) were compared. This study also examined the association with severe infections in these patients. Among the three age groups, there were significant differences in sex (P = 0.032), serum Krebs von den Lungen-6 (P < 0.01), and total ground-glass opacity score (P = 0.011). The causes of death were mainly severe infections and complications of ILD. Kaplan-Meier curve analysis showed a significantly lower 5-year survival rate in the oldest group (P < 0.01). Regarding severe infections in these patients, the 5-year cumulative incidence of severe infections was higher in the patients receiving steroid pulse therapy (P = 0.034). The clinical characteristics of MPO-ANCA-positive AAV-ILD differ with age in elderly patients, with age being an important poor prognostic factor in these patients. The administration of steroid pulse therapy is a significant risk factor of severe infection in MPO-ANCA-positive elderly patients with AAV-ILD.

Clinical features of dermatomyositis associated with anti-MDA5 antibodies by age.

OBJECTIVES: Anti-melanoma differentiation-associated gene 5 (MDA5) autoantibody-positive and age at onset ≥60 years are poor prognosis factors in polymyositis (PM) and dermatomyositis (DM) associated with interstitial lung disease (ILD) among Japanese patients. However, the influence of age on the clinical features of anti-MDA5 autoantibody-positive patients with DM remains unclear. METHODS: We retrospectively examined 40 patients with DM and anti-MDA5 autoantibodies according to age. We compared patients aged <60 and ≥60 years with respect to clinical features including laboratory test findings, high-resolution lung computed tomography data, treatment content, and complications such as infections and prognosis. We also examined clinical features between surviving and deceased patients in the older patient group. RESULTS: Of 40 enrolled patients, 13 were classified as old and 27 as young. Older patients had significantly fewer clinical symptoms including arthralgia/arthritis (p < .01), skin ulceration (p = .02), and higher mortality than younger patients (p = .02) complicated with rapidly progressive ILD (RP-ILD), combination immunosuppressive therapy, and strictly controlled infections. CONCLUSION: Clinical features and mortality of anti-MDA5 autoantibody-positive DM patients were influenced by age. Patients aged ≥60 years had a worse prognosis, and combination immunosuppressive therapy was often ineffective for RP-ILD in older patients.

A case of long-term dasatinib-induced proteinuria and glomerular injury.

A 52-year-old woman was diagnosed with chronic myeloid leukemia. Treatment with dasatinib, a second-generation Bcr-Abl tyrosine kinase inhibitor, was initiated, and complete cytogenetic remission was achieved. Two years later, proteinuria occurred, and the urinary protein level increased gradually in the next 3 years. Moreover, the serum creatinine level increased mildly during this period. The urinary protein level reached 2.18 g/gCr; hence, a renal biopsy was conducted. Light microscopy revealed mild proliferation of mesangial cells, and immunofluorescence analysis revealed IgG and C3 depositions in the mesangial area. Electron microscopy revealed electron-dense deposition in the paramesangial area, partial podocyte foot process effacement, and segmental endothelial cell swelling with a slight expansion of the subendothelial space. Dasatinib was discontinued, and within 3 weeks, the proteinuria disappeared, with improvements in her renal function. After switching to bosutinib, a new second-generation of tyrosine kinase inhibitor, the proteinuria remained negative. The rapid cessation of proteinuria following dasatinib discontinuation indicated that proteinuria was induced by the long-term administration of dasatinib. Proteinuria and renal function should be regularly monitored during dasatinib therapy.

Attenuation of renal fibrosis after unilateral ureteral obstruction in mice lacking the N-type calcium channel.

The N-type Ca2+ channel (Cav2.2) is distributed in sympathetic nerves that innervate the tubules, the vessels, and the juxtaglomerular granular cells of the kidney. However, the role of N-type Ca2+ channels in renal disease remains unknown. To address this issue, Cav2.2 knockout mice were utilized. Immunoreactive Cav2.2 was undetectable in normal kidneys of C57BL/6N mice, but it became positive in the interstitial S100-positive nerve fibers after unilateral ureteral obstruction (UUO). There were no significant differences in mean blood pressure, heart rate, and renal function between wild-type littermates and Cav2.2-knockout mice at baseline, as well as after UUO. Cav2.2 deficiency significantly reduced the EVG-positive fibrotic area, alpha-SMA expression, the production of type I collagen, and the hypoxic area in the obstructed kidneys. The expression of tyrosine hydroxylase, a marker for sympathetic neurons, was significantly increased in the obstructed kidneys of wild-type mice, but not in Cav2.2-knockout mice. These data suggest that increased Cav2.2 is implicated in renal nerve activation leading to the progression of renal fibrosis. Blockade of Cav2.2 might be a novel therapeutic approach for preventing renal fibrosis.

Urinary Activin A is a novel biomarker reflecting renal inflammation and tubular damage in ANCA-associated vasculitis.

Activin A, a member of the transforming growth factor-beta superfamily, is a critical modulator of inflammation and plays a key role in controlling the cytokine cascade that drives the inflammatory response. However, the role of activin A in inflammatory kidney diseases remains unknown. To address this issue, we examined here whether activin A can be detected in the kidney and/or urine from patients with antineutrophil cytoplasmic antibody (ANCA) -associated vasculitis (AAV). Fifty-one patients who had been diagnosed with AAV and were treated in our department between November 2011 to March 2018 were included in this study. Forty-one patients had renal complications (renal AAV). Serum and urinary activin A levels were measured by enzyme-linked immunosorbent assay. Correlation of urinary activin A concentration with clinical parameters was analyzed. Urinary activin A was undetectable in healthy volunteers. In contrast, urinary activin A concentration was significantly increased in patients with renal AAV but not in those with non-renal AAV. Urinary activin A concentration decreased rapidly after immunosuppressive treatment. There was a significant correlation of urinary activin A level with urinary protein, L-FABP, and NAG. Histologic evaluation revealed that urinary activin A levels were significantly higher in patients with cellular crescentic glomeruli than in those lacking this damage. In situ hybridization demonstrated that the mRNA encoding the activin A ßA subunit was undetectable in normal kidneys but accumulated in the proximal tubules and crescentic glomeruli of the kidneys of patients with renal AAV. Immunostaining showed that activin A protein also was present in the proximal tubules, crescentic glomeruli, and macrophages infiltrating into the interstitium in the kidneys of patients with renal AAV. These data suggested that urinary activin A concentration reflects renal inflammation and tubular damage in AAV and may be a useful biomarker for monitoring renal AAV.

Clinical features of patients with anti-melanoma differentiation-associated gene-5 antibody-positive dermatomyositis complicated by spontaneous pneumomediastinum.

BACKGROUND: Dermatomyositis (DM) with autoantibody against melanoma differentiation-associated gene-5 (MDA5) is characterized by elevated risk of rapidly progressive interstitial lung disease (RP-ILD) with a potentially fatal course. Pneumomediastinum (PNM) is a common pulmonary manifestation which accompanies ILD. However, the clinical features of the patients with anti-MDA5 antibody-positive DM who develop PNM remain unclear. METHODS: We retrospectively examined 31 patients with DM having anti-MDA5 antibody and compared the clinical features between patients with PNM (PMN(+)) (n = 11) and those without (PNM(-) (n = 20). In addition, we evaluated the treatment-related prognoses in PNM(+) group. RESULTS: CT score (total ground-glass opacity (GGO) score, P = 0.02; total fibrosis score, P = 0.02) before treatment, and mortality (P = 0.04) were significantly higher in PNM(+) group. The cumulative survival rate as assessed by Kaplan-Meier method was significantly lower for the PNM(+) group (P = 0.02). Among 11 PMN(+) patients, 9 patients (9/11, 81.8%) underwent intensive immunosuppression therapy for RP-ILD, and 5 patients (5/11, 45.5%) did not respond to it and died from the respiratory failure. At the time of diagnosis of PNM, nonsurvivors had worse liver function (ALT, P = 0.03; LDH, P = 0.01), worse respiratory status (A-aDO2, P = 0.01), and worse CT score (total GGO score, P < 0.01). CONCLUSIONS: A subgroup of patients with DM having anti-MDA5 antibody complicated by PNM as well as RP-ILD did respond to intensive immunosuppression therapy. Initial aggressive immunosuppressive therapy should be considered for these patients.Key Points• This study clearly demonstrate the presence of PNM was associated with elevated risk of death due to respiratory failure from RP-ILD among patients with DM having circulating anti-MDA5-antibody.•This study demonstrate evaluation of CT image may be helpful to find patients with better response to the intense immunosuppression therapy for the patients with DM having circulating anti-MDA5-antibody and PNM.

Enhancement of HGF-induced tubulogenesis by endothelial cell-derived GDNF.

Tubulogenesis, the organization of epithelial cells into tubular structures, is an essential step during renal organogenesis as well as during the regeneration process of renal tubules after injury. In the present study, endothelial cell-derived factors that modulate tubule formation were examined using an in vitro human tubulogenesis system. When human renal proximal tubular epithelial cells (RPTECs) were cultured in gels, tubular structures with lumens were induced in the presence of hepatocyte growth factor (HGF). Aquaporin 1 was localized in the apical membrane of these tubular structures, suggesting that these structures are morphologically equivalent to renal tubules in vivo. HGF-induced tubule formation was significantly enhanced when co-cultured with human umbilical vein endothelial cells (HUVECs) or in the presence of HUVEC-conditioned medium (HUVEC-CM). Co-culture with HUVECs did not induce tubular structures in the absence of HGF. A phospho-receptor tyrosine kinase array revealed that HUVEC-CM markedly enhanced phosphorylation of Ret, glial cell-derived neurotrophic factor (GDNF) receptor, in HGF-induced tubular structures compared to those without HUVEC-CM. HUVECs produced GDNF, and RPTECs expressed both Ret and GDNF family receptor alpha1 (co-receptor). HGF-induced tubule formation was significantly enhanced by addition of GDNF. Interestingly, not only HGF but also GDNF significantly induced phosphorylation of the HGF receptor, Met. These data indicate that endothelial cell-derived GDNF potentiates the tubulogenic properties of HGF and may play a critical role in the epithelial-endothelial crosstalk during renal tubulogenesis as well as tubular regeneration after injury.

Hepatitis E during Tocilizumab Therapy in a Patient with Rheumatoid Arthritis: Case Report and Literature Review.

Hepatitis E is an acute self-limiting disease caused by hepatitis E virus (HEV). Recent reports show that HEV can induce chronic hepatitis or be reactivated in immunocompromised hosts. We report a 63-year-old woman with rheumatoid arthritis (RA) who developed hepatitis E during treatment with tocilizumab. Analysis of serially stocked serum samples confirmed that hepatitis was caused by primary infection with HEV and not by viral reactivation. Her liver function improved after discontinuing tocilizumab and remained within the normal range without reactivation of HEV for >5 years after restarting tocilizumab. We also reviewed the published cases of hepatitis E that developed during RA treatment.

The Analysis of Renal Infiltrating Cells in Acute Tubulointerstitial Nephritis Induced by Anti-PD-1 Antibodies: A Case Report and Review of the Literature.

Nivolumab is an anti-programmed cell death-1 (PD-1) antibody that is utilized as an immune checkpoint inhibitor (ICI) for cancer therapy. We herein present the case of a 57-year-old man who developed acute kidney injury during treatment with nivolumab for lung cancer. A renal biopsy revealed acute tubulointerstitial nephritis. Immunohistochemical staining demonstrated marked infiltration of macrophages and T cells together with mild B cell infiltration. Of note, strong CD163+ M2 macrophage infiltration was observed. The cessation of nivolumab and high-dose prednisolone therapy improved the renal function of the patient. Further, we review the pertinent literature on renal-infiltrating cells in ICI-induced tubulointerstitial nephritis.

Identification of Urinary Activin A as a Novel Biomarker Reflecting the Severity of Acute Kidney Injury.

Acute kidney injury (AKI) is a common but complex condition that is associated with increased morbidity and mortality. In the present study, we examined whether urinary activin A, a member of the TGF-beta superfamily, is present in mice with ischemia-reperfusion injury and in humans with AKI, as well as its potential as a biomarker for AKI. Expression of activin A was markedly increased in ischemic mouse kidneys. In situ hybridization demonstrated that activin mRNA was expressed in tubular cells of ischemic kidneys but not of normal kidneys. Immunoreactive activin A, which was absent in normal kidneys, was detected in the cytoplasm of proximal tubular cells in ischemic kidneys. Activin A was undetectable in the urine of normal mice. In contrast, activin A was significantly increased in the urine of ischemic mice at 3 h after reperfusion. Urinary activin A levels increased according to the period of ischemia. In humans, urinary activin A was almost undetectable in healthy volunteers and in patients with pre-renal AKI, but was significantly increased in patients with renal AKI. There was no significant correlation between urinary activin A and serum activin A. Collectively, urinary activin A might be a useful biomarker reflecting the severity of AKI.

Novel approach for the detection of tubular cell migration into the interstitium during renal fibrosis in rats.

BACKGROUND: The process of epithelial-mesenchymal transition (EMT), which is generally defined by phenotypic changes of injured tubules such as loss of epithelial markers or acquisition of mesenchymal markers, implies various activating steps, including proliferation, migration, and ability to produce extracellular matrix proteins. We established here a novel approach for the detection of tubular cell migration into the interstitium during renal fibrosis in vivo. RESULTS: Using an osmotic pump, bromodeoxyuridine (BrdU) was continuously given to 7-week-old Wistar rats for 4 weeks, and BrdU-positive cells were detected by immunostaining. BrdU-positive cells were present in aquaporin-1-positive proximal tubules, but not in the interstitium of BrdU-treated rat kidneys. After unilateral ureteral obstruction (UUO), some BrdU-positive tubular cells protruded from the basement membrane and migrated into the interstitium. Interstitial BrdU-positive cells were co-localized with alpha-smooth muscle actin, fibroblast specific protein-1, vimentin, and type I collagen, but not with CD68 or CD3. No BrdU-positive cells were observed in the interstitium of sham-operated kidneys. The number of BrdU-positive cells migrating into the interstitium significantly increased and peaked at 8 days after UUO. CONCLUSIONS: Long-term BrdU labeling marked some of the proximal tubular cells and enabled us to detect tubular cell migration into the interstitium after UUO. This simple method might be useful to detect EMT in vivo.

Diverse Cell Populations Involved in Regeneration of Renal Tubular Epithelium following Acute Kidney Injury.

Renal tubular epithelium has the capacity to regenerate, repair, and reepithelialize in response to a variety of insults. Previous studies with several kidney injury models demonstrated that various growth factors, transcription factors, and extracellular matrices are involved in this process. Surviving tubular cells actively proliferate, migrate, and differentiate in the kidney regeneration process after injury, and some cells express putative stem cell markers or possess stem cell properties. Using fate mapping techniques, bone marrow-derived cells and endothelial progenitor cells have been shown to transdifferentiate into tubular components in vivo or ex vivo. Similarly, it has been demonstrated that, during tubular cell regeneration, several inflammatory cell populations migrate, assemble around tubular cells, and interact with tubular cells during the repair of tubular epithelium. In this review, we describe recent advances in understanding the regeneration mechanisms of renal tubules, particularly the characteristics of various cell populations contributing to tubular regeneration, and highlight the targets for the development of regenerative medicine for treating kidney diseases in humans.

Follistatin, an activin antagonist, ameliorates renal interstitial fibrosis in a rat model of unilateral ureteral obstruction.

Activin, a member of the TGF-ß superfamily, regulates cell growth and differentiation in various cell types. Activin A acts as a negative regulator of renal development as well as tubular regeneration after renal injury. However, it remains unknown whether activin A is involved in renal fibrosis. To clarify this issue, we utilized a rat model of unilateral ureteral obstruction (UUO). The expression of activin A was significantly increased in the UUO kidneys compared to that in contralateral kidneys. Activin A was detected in glomerular mesangial cells and interstitial fibroblasts in normal kidneys. In UUO kidneys, activin A was abundantly expressed by interstitial α-SMA-positive myofibroblasts. Administration of recombinant follistatin, an activin antagonist, reduced the fibrotic area in the UUO kidneys. The number of proliferating cells in the interstitium, but not in the tubules, was significantly lower in the follistatin-treated kidneys. Expression of α-SMA, deposition of type I collagen and fibronectin, and CD68-positive macrophage infiltration were significantly suppressed in the follistatin-treated kidneys. These data suggest that activin A produced by interstitial fibroblasts acts as a potent profibrotic factor during renal fibrosis. Blockade of activin A action may be a novel approach for the prevention of renal fibrosis progression.