Epithelial-mesenchymal transition (EMT) in kidney fibrosis: fact or fantasy?

Maternal exposure to di-n-butyl phthalate promotes Snail1-mediated epithelial-mesenchymal transition of renal tubular epithelial cells via upregulation of TGF-β1 during renal fibrosis in rat offspring

We previously demonstrated that maternal exposure to di-n-butyl phthalate (DBP) resulted in renal fibrosis in male offspring; however, the underlying mechanism governing this effect has not been thoroughly elucidated to date. We hypothesized that DBP exposure induces TGF-β expression and abnormal activation of epithelial-mesenchymal transition (EMT) in fibrotic kidneys. Pregnant rats received DBP orally at a dose of 850 mg/kg BW/day during gestational days 14-18. In the DBP-exposed group, immunohistochemistry (IHC) staining showed increased expression of TGF-β1 and EMT markers. In rat kidney tubular epithelial cells (NRK52E), ROS production increased expression levels of TGF-β1 and subsequently contributed to the induction of Snail1-mediated EMT. Notably, DBP exposure also promoted autophagy that downregulated TGF-β1. Taken together, our findings suggest that maternal exposure to DBP promotes EMT in tubular epithelial cells via upregulation of TGF-β1.

Network-based integrated analysis of omics data reveal novel players of TGF-β1-induced EMT in human peritoneal mesothelial cells

Long-term peritoneal dialysis is associated with progressive fibrosis of the peritoneum. Epithelial-mesenchymal transition (EMT) of mesothelial cells is an important mechanism involved in peritoneal fibrosis, and TGF-β1 is considered central in this process. However, targeting currently known TGF-β1-associated pathways has not proven effective to date. Therefore, there are still gaps in understanding the mechanisms underlying TGF-β1-associated EMT and peritoneal fibrosis. We conducted network-based integrated analysis of transcriptomic and proteomic data to systemically characterize the molecular signature of TGF-β1-stimulated human peritoneal mesothelial cells (HPMCs). To increase the power of the data, multiple expression datasets of TGF-β1-stimulated human cells were employed, and extended based on a human functional gene network. Dense network sub-modules enriched with differentially expressed genes by TGF-β1 stimulation were prioritized and genes of interest were selected for functional analysis in HPMCs. Through integrated analysis, ECM constituents and oxidative stress-related genes were shown to be the top-ranked genes as expected. Among top-ranked sub-modules, TNFAIP6, ZC3H12A, and NNT were validated in HPMCs to be involved in regulation of E-cadherin, ZO-1, fibronectin, and αSMA expression. The present data shows the validity of network-based integrated analysis in discovery of novel players in TGF-β1-induced EMT in peritoneal mesothelial cells, which may serve as new prognostic markers and therapeutic targets for peritoneal dialysis patients.

Clinical and pathological factors of renal anaemia in patients with IgA nephropathy in Chinese adults: a cross-sectional study

OBJECTIVE

Few studies with large sample populations concerning renal anaemia and IgA nephropathy have been reported worldwide. The purpose of this cross-sectional study was to examine the clinical and pathological characteristics and influencing factors associated with renal anaemia in patients with IgA nephropathy, which is the most common aetiology of chronic kidney disease.

METHODS

A total of 462 hospitalised patients with IgA nephropathy confirmed by renal biopsy who met the inclusion criteria were consecutively recruited from January 2014 to January 2016. Their general information, routine blood test results, blood chemistries, estimated glomerular filtration rates (eGFRs) and renal pathologies were collected. The Oxford classification was used to characterise the renal pathologies. Univariable and multivariate logistic regression models were used to analyse the influencing factors of anaemia associated with IgA nephropathy.

RESULTS

The incidence of renal anaemia was 28.5% (132/462 patients) in our study (21.3% in males and 38.9% in females). The anaemia type was primarily normocytic and normochromic. The rate of anaemia in patients with eGFR values of 30-59 mL/min/1.73 m² was higher than that in patients with an eGFR >60 mL/min/1.73 m² (42.9% vs 17.8%, p<0.001). Notably, in the group with eGFR values <15 mL/min/1.73 m², the anaemia rate was 100%. Logistic regression analysis showed that factors affecting anaemia in patients with IgA nephropathy included being female (OR 3.02, 95% CI 1.76 to 5.17), low albumin levels (OR 0.87, 95% CI 0.82 to 0.93), reduced eGFR values (OR 0.98, 95% CI 0.97 to 0.99) and renal tubulointerstitial lesions >50% (OR 2.57, 95% CI 1.22 to 5.40).

CONCLUSIONS

The female sex, hypoalbuminaemia, reduced eGFR levels and severe renal tubulointerstitial lesions were correlated with renal anaemia in patients with IgA nephropathy. These results provide new insight into our understanding of anaemia in IgA nephropathy and may improve the management and treatment of clinical renal anaemia.

Pathogenesis of Chronic Allograft Dysfunction Progress to Renal Fibrosis

Kidney transplantation is a life-change measurement for the patients of end-stage renal disease (ESRD). However, the renal allograft cannot avoid initial acute kidney injury (AKI) and subsequent chronic allograft dysfunction (CAD), gradually develops fibrosis and eventually loses function. It is imperative to disclose the pathogenesis of AKI and CAD in order to facilitate interventions. We have studied the involvement of immunity, inflammation, and apoptosis in ischemia-reperfusion injury (IRI) and/or immunosuppressant induced AKI models, with associated chronic damage. Our research mainly focused on tubular epithelial cells (TECs) that are passive victims and also active participators in injury and mediate following repair or fibrosis. Targeting not only fibroblasts/myofibroblasts, but also TECs, might be a fundamental strategy to prevent and treat renal fibrosis. We have also evaluated the potential application of siRNA targeting caspase-3 and tissue protective erythropoietin derivatives, HBSP and CHBP, aiming to treat AKI and prevent CAD. Significant improvements have been obtained, but timely diagnosis and precise therapy of AKI and prevention of CAD progressing to ESRD are still very challenging. Modern technologies such as microarray and sequencing analysis have been used to identify biomarkers and potentially facilitate individual cell target treatment for transplant patients.

How Acute Kidney Injury Contributes to Renal Fibrosis

Acute kidney injury (AKI) is a widespread clinical syndrome directly associated with patient short-term and long-term morbidity and mortality. During the last decade, the incidence rate of AKI has been increasing, the repeated and severe episodes of AKI have been recognized as a major risk factor chronic kidney diseases (CKD) and end-stage kidney disease (ESRD) leading to global disease burden. Proposed pathological processes and risk factors that add to the transition of AKI to CKD and ESRD include severity and frequency of kidney injury, older age, gender, genetics and chronic health conditions like diabetes, hypertension, and obesity. Therefore, there is a great interest in learning about the mechanism of AKI leading to renal fibrosis, the ultimate renal lesions of CKD. Over the last several years, a significant attention has been given to the field of renal fibrosis with impressive progression in knowing the mechanism of renal fibrosis to detailed cellular characterization and molecular pathways implicated in tubulointerstitial fibrosis. Research and clinical trial are underway for emerging biomarkers detecting early kidney injury, predicting kidney disease progression and developing strategies to efficiently treat AKI and to minimize AKI progression to CKD and ESRD. Specific interventions to prevent renal fibrosis are still experimental. Potential therapeutic advances based on those molecular mechanisms will hopefully offer promising insights into the development of new therapeutic interventions for patients in the near future.

Bariatric Surgery Modulates Urinary Levels of MicroRNAs Involved in the Regulation of Renal Function

Background: Obesity and diabetes cause chronic kidney disease with a common pathophysiology that is characterized by the accumulation of collagen in the extracellular matrix. Recent evidence has implicated the epithelial-to-mesenchymal transition (EMT) as a key step in this pathology with regulation by microRNAs. Weight loss leads to improvements in renal function; therefore, this study hypothesized that bariatric-surgery aided weight loss would lead to changes in urinary microRNAs involved in the regulation of renal function. Materials and methods: Twenty-four bariatric patients undergoing Roux-en-Y gastric bypass and sleeve gastrectomy donated urine pre-operatively and at 2-6 months and 1-2 years post-operatively. Urine samples were also obtained from 10 healthy weight and 7 morbidly obese non-surgical controls. Expression levels of kidney microRNAs were assessed in urine and the function of microRNAs was assessed through the in vitro transfection of HK-2 cells, a kidney proximal tubule cell line. Results: Levels of miR 192, miR 200a, and miR 200b were upregulated in urine following bariatric surgery. This increase was consistent across surgical type and diabetes status and was maintained and enhanced with time. Bariatric surgery alters urinary miR 192 expression from levels seen in morbidly obese patients to levels seen in healthy weight control patients. In mechanistic studies, the transfection of miR 192 in HK-2 cells increased miR 200a expression and decreased ZEB2, a key transcriptional promoter of kidney fibrosis. Conclusions: Bariatric surgery increased miR 192 and miR 200 urinary levels, key anti-fibrotic microRNAs that could contribute to a renal-protective mechanism and may be of value as urinary biomarkers following surgery. These findings suggest that urinary microRNAs may represent potential novel biomarkers for obesity-associated renal function.

Nudel involvement in the high-glucose-induced epithelial-mesenchymal transition of tubular epithelial cells

Nudel is a newly discovered factor related to cell migration. The tubular epithelial-mesenchymal transition (EMT) includes four steps: the loss of the adhesive properties of epithelial cells, the acquisition of a mesenchymal cell phenotype, the destruction of the tubular basal membrane, and the migration into the renal interstitium. The purpose of this study was to investigate the role of Nudel in the high-glucose-induced EMT of tubular epithelial cells. Human renal proximal tubular epithelial cells (HKCs) were treated with Nudel shRNA to clarify the role and mechanism of Nudel in tubular EMT induced by high glucose. We found that Nudel was expressed at a high level in high-glucose-stimulated HKCs, and the expression of Nudel was associated with the activation of signal transducer and activator of transcription 3. After transfection with Nudel shRNA, we detected the expression levels of E-cadherin, α-smooth muscle actin (α-SMA), and the Wiskott-Aldrich syndrome family of proteins (including WASP, N-WASP, WAVE1, WAVE2, and WAVE3) via assay. Cell migration was analyzed by the scratching method. The results showed that high glucose downregulated E-cadherin expression, upregulated α-SMA expression, and promoted the migration of HKCs. The expression levels of N-WASP, WAVE1, and WAVE2 were also elevated in HKCs treated with high glucose. All changes induced by high glucose were ameliorated by Nudel depletion. We conclude that Nudel participates in the transition and the migration of tubular epithelial cells via the regulation of WASP family proteins.

MKP2 inhibits TGF-β1-induced epithelial-to-mesenchymal transition in renal tubular epithelial cells through a JNK-dependent pathway

Epithelial-to-mesenchymal transition (EMT) is a phenotypic conversion that plays a crucial role in renal fibrosis leading to chronic renal failure. Mitogen-activated protein kinase phosphatase 2 (MKP2) is a member of the dual-specificity MKPs that regulate the MAP kinase pathway involved in transforming growth factor-β1 (TGF-β1)-induced EMT. However, the function of MKP2 in the regulation of EMT and the underlying mechanisms are still largely unknown. In the present study, we detected the expression of MKP2 in an animal model of renal fibrosis and evaluated the potential role of MKP2 in tubular EMT induced by TGF-β1. We found that the expression of MKP2 was up-regulated in the tubular epithelial of unilateral ureter obstruction rats. Meanwhile, we also demonstrated that TGF-β1 up-regulated MKP2 expression in NRK-52E cells during their EMT phenotype acquisition. Importantly, overexpression of MKP2 inhibited c-Jun amino terminal kinase (JNK) signaling and partially reversed EMT induced by TGF-β1. Moreover, reducing MKP2 expression enhanced JNK phosphorylation, promoted the E-cadherin suppression and induced α-SMA expression and fibronectin secretion in response to TGF-β1, which could be rescued by a JNK inhibitor. These results provide the first evidence that MKP2 is a negative feedback molecule induced by TGF-β1, and MKP2 overexpression inhibits TGF-β1-induced EMT through the JNK signaling pathway. MKP2 could be a promising target to be used in gene therapy for renal fibrosis.

Modulation of NCAM/FGFR1 signaling suppresses EMT program in human proximal tubular epithelial cells

Neural cell adhesion molecule (NCAM) and fibroblast growth factor receptor 1 (FGFR1) cross-talk have been involved in epithelial-to-mesenchymal transition (EMT) process during carcinogenesis. Since EMT also contributes to maladaptive repair and parenchymal damage during renal fibrosis, we became encouraged to explore the role of NCAM/FGFR1 signaling as initiating or driving forces of EMT program in cultured human proximal tubular epithelial cells (TECs). TECs stimulated with TGF-β1 (10ng/mL) was used as an established in vitro EMT model. TGF-β1 downstream effectors were detected in vitro, as well as in 50 biopsies of different human kidney diseases to explore their in vivo correlation. NCAM/FGFR1 signaling and its modulation by FGFR1 inhibitor PD173074 (100nM) were analyzed by light microscopy, immunolabeling, qRT-PCR and scratch assays. Morphological changes associated with EMT appeared 48h after TGF-ß1 treatment and was clearly apparent after 72 hours, followed by loss of CDH1 (encoding E-Cadherin) and transcriptional induction of SNAI1 (SNAIL), SNAI2 (SLUG), TWIST1, MMP2, MMP9, CDH2 (N-Cadherin), ITGA5 (integrin-α5), ITGB1 (integrin-β1), ACTA2 (α-SMA) and S100A4 (FSP1). Moreover, at the early stage of EMT program (24 hours upon TGF-β1 exposure), transcriptional induction of several NCAM isoforms along with FGFR1 was observed, implicating a mechanistic link between NCAM/FGFR1 signaling and induction of EMT. These assumptions were further supported by the inhibition of the EMT program after specific blocking of FGFR1 signaling by PD173074. Finally, there was evidence for an in vivo TGF-β1 pathway activation in diseased human kidneys and correlation with impaired renal excretory functions. Collectively, NCAM/FGFR1 signaling appears to be involved in the initial phase of TGF-ß1 initiated EMT which can be effectively suppressed by application of FGFR inhibitor.

Comparison of renal lesions in cats and dogs using pathomorphological and ımmunohistochemical methods

We investigated the pathogenesis of chronic renal fibrosis in cats and dogs using immunohistochemistry. We used the avidin-biotin complex peroxidase (ABC-P) method with antibodies against transforming growth factor-β1, cytokeratin, E-cadherin, S100A4, alpha-smooth muscle actin, vimentin and nestin to determine whether tubule epithelial cells had undergone epithelial-mesenchymal transformation (EMT) that resulted in loss of epithelial cells and an increased number of mesenchymal cells. Although nephrosis was more common in dogs, nephritis was more common in cats; these pathologies developed in both kidneys. We found that EMT participated in the pathogenesis of renal fibrosis in both dogs and cats.

Lack of microRNA-155 ameliorates renal fibrosis by targeting PDE3A/TGF-β1/Smad signaling in mice with obstructive nephropathy

Although microRNA-155 (miR-155) is implicated in the pathogenesis of several fibrotic diseases, information regarding its functional role in renal fibrosis is limited. The current study aims to investigate the effects of miR-155 on renal fibrosis in unilateral ureteral occlusion (UUO) mice. MiR-155 level was significantly increased in renal tissues of UUO mice and TGF-β1-treated HK2 cells. Masson's trichrome staining showed that delivery of adeno-associated virus encoding miR-155 inhibitor led to a decrease in renal fibrosis induced by UUO. The increased expression of plasminogen activator inhibitor type 1, collagen III and collagen IV was also inhibited after miR-155 inhibition. In addition, miR-155 knockdown also prevented TGF-β1-induced epithelial-mesenchymal transition, concomitantly with a restoration of E-cadherin expression and a decrease of vimentin expression. Computational analysis revealed that miR-155 directly targets at 3'UTR of PDE3A. Overexpression of miR-155 suppressed the luciferase activity and protein expression of PDE3A, whereas inhibition of miR-155 increased PDE3A luciferase activity and expression. Furthermore, miR-155 inhibited TGF-β1-induced the increase of TGF-β1 expression and Smad-2/3 phosphorylation in HK2 cells. In contrast, knockdown of PDE3A reversed the effect of miR-155 inhibition on TGF-β1 expression. This study demonstrates that knockdown of miR-155 attenuates renal fibrosis via inhibiting TGF-β1/Smad signaling activation by targeting the upstream molecule PDE3A. This study suggests that miR-155 inhibition may be a novel therapeutic approach for preventing fibrotic kidney diseases.

The therapeutic potential of targeting the endothelial-to-mesenchymal transition

Endothelial cells (ECs) have been found to be capable of acquiring a mesenchymal phenotype through a process known as endothelial-to-mesenchymal transition (EndMT). First seen in the developing embryo, EndMT can be triggered postnatally under certain pathological conditions. During this process, ECs dedifferentiate into mesenchymal stem-like cells (MSCs) and subsequently give rise to cell types belonging to the mesoderm lineage. As EndMT contributes to a multitude of diseases, pharmacological modulation of the signaling pathways underlying EndMT may prove to be effective as a therapeutic treatment. Additionally, EndMT in ECs could also be exploited to acquire multipotent MSCs, which can be readily re-differentiated into various distinct cell types. In this review, we will consider current models of EndMT, how manipulation of this process might improve treatment of clinically important pathologies and how it could be harnessed to advance regenerative medicine and tissue engineering.

Testosterone and Mast Cell Interactions in the Development of Kidney Fibrosis after Unilateral Ureteral Obstruction in Rats

Mast cell and testosterone interactions involved in renal fibrosis in rats subjected to unilateral ureteral obstruction (UUO) were investigated. Orchiectomized (ORX) and nonorchiectomized Wistar rats were subjected to UUO, and a nonorchiectomized group was sham-operated (control: SO). Animals from the UUO group were treated with saline or sodium cromoglycate (CG). Some ORX rats from the saline or CG groups also received testosterone propionate replacement (TR). Kidneys and blood were collected 14 d after UUO or SO. Kidney sections were stained with toluidine blue to quantify mast cells, and picrosirius red was used for collagen analysis. Immunohistochemistry for α-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) expression was also performed. Plasma testosterone levels (PTLs) were measured. ORX decreased and TR normalized PTLs. UUO increased mast cell density in the kidney pelvis, but not in the kidney parenchyma. UUO increased mast cell degranulation, and CG or ORX inhibited this effect. TR partially reversed the effect of ORX on mast cell degranulation, and CG partially inhibited that effect of TR. UUO increased the collagen areas of the renal parenchyma, whereas CG or ORX abolished that alteration; TR reversed the effects of ORX, and CG partially inhibited that effect of TR. UUO increased tubulointerstitial α-SMA expression and PCNA-positive cells, and these changes were sensitive to ORX or CG to the same degree, while TR again reversed the effect of ORX. Renal fibrosis after UUO appears to be determined by interactions between testosterone and mast cells.

Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells

Reactivation of Notch signaling in kidneys of animal models and patients with chronic kidney disease (CKD) has been shown to contribute to epithelial injury and fibrosis development. Here, we investigated the mechanisms of Notch-induced injury in renal epithelial cells. We performed genome-wide transcriptome analysis to identify Notch target genes using an in vitro system of cultured tubular epithelial cells expressing the intracellular domain of Notch1. One of the top downregulated genes was Disabled-2 ( Dab2). With the use of Drosophila nephrocytes as a model system, we found that Dab (the Drosophila homolog of Dab2) knockdown resulted in a significant filtration defect, indicating that loss of Dab2 plays a functional role in kidney disease development. We showed that Dab2 expression in cultured tubular epithelial cells is involved in endocytic regulation and that it also protects cells from TGF-β-induced epithelial-to-mesenchymal transition. In vivo correlation studies indicated its additional role in renal ischemia-induced injury. Together, these data suggest that Dab2 plays a versatile role in the kidney and may impact on acute and CKDs.-Schütte-Nütgen, K., Edeling, M., Mendl, G., Krahn, M. P., Edemir, B., Weide, T., Kremerskothen, J., Michgehl, U., Pavenstädt, H. Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells.

7,12-Dimethylbenz[α]anthracene increases cell proliferation and invasion through induction of Wnt/β-catenin signaling and EMT process

7,12-Dimethylbenz[α]anthracene (DMBA) is a hazardous component present in polluted environments. DMBA has been used as an experimental tool for in vivo tumor formation owing to its carcinogenic effects, but the detailed molecular mechanism of DMBA has not been fully established. To comprehend the carcinogenic mechanism of DMBA, we explored its effects in the breast cancer cell lines, MCF-7 and MDA-MB-231, and the cervical cancer cell line, HeLa. Cell viability assay and measurement of a proliferation marker showed that DMBA markedly increased cancer cell proliferation. Furthermore, morphological observations and wound healing assays in nontumorigenic MCF-10A cells and trans-well invasion assays in cancer cells following DMBA treatment revealed that DMBA induced cell migration and invasion. To reveal the molecular mechanism of DMBA, we investigated the effects of DMBA on the epithelial-mesenchymal transition (EMT) process and Wnt/β-catenin signaling, a critical pathway for cell proliferation that was reported to correlate with the EMT process, by using quantitative RT-PCR (qPCR), western blot analysis, and confocal microscopy. Consequently, we found that DMBA increased cancer cell proliferation and invasion through the promotion of EMT-inducing factors and β-catenin. Especially, it was revealed in promoter activity assay using mutated luciferase vectors on transcription factor-binding sites that TWIST1 is promoted by DMBA through induction of STAT3-mediated promoter activation. To further elucidate the detailed mechanism of DMBA, we aimed to identify the key regulator of its carcinogenic action. DMBA was shown to significantly upregulate the expression of specificity protein 1 (Sp1), a transcription factor, and the carcinogenic effects of DMBA were blocked via the suppression or interruption of Sp1 activity. In conclusion, our data suggested that DMBA induced carcinogenic effects through activation of Wnt/β-catenin signaling and the EMT process by upregulating Sp1 activity.

Heterozygosity of mitogen-activated protein kinase organizer 1 ameliorates diabetic nephropathy and suppresses epithelial-to-mesenchymal transition-like changes in db/db mice

Background

Progressive diabetic nephropathy (DN) is characterized by tubulointerstitial fibrosis that is caused by accumulation of extracellular matrix. Induced by several factors, matrix-producing myofibroblasts may to some extent originate from tubular cells by epithelial-to-mesenchymal transition (EMT). Although previous data document that activation of hypoxia-inducible factor (HIF) signalling can be renoprotective in acute kidney disease, this issue remains controversial in chronic kidney injury. Here, we studied whether DN and EMT-like changes are ameliorated in a mouse model of type 2 diabetes mellitus with increased stability and activity of the HIF.

Methods

We used db/db mice that were crossed with transgenic mice expressing reduced levels of mitogen-activated protein kinase organizer 1 (MORG1), a scaffold protein interacting with prolyl hydroxylase domain 3 (PHD3), because of deletion of one MORG1 allele.

Results

We found significantly reduced nephropathy in diabetic MORG1+/- heterozygous mice compared with the diabetic wild-types (db/dbXMORG1+/+). Furthermore, we demonstrated that EMT-like changes in the tubulointerstitium of diabetic wild-type MORG1+/+ mice are present, whereas diabetic mice with reduced expression of MORG1 showed significantly fewer EMT-like changes.

Conclusions

These findings reveal that a deletion of one MORG1 allele inhibits the development of DN in db/db mice. The data suggest that the diminished interstitial fibrosis in these mice is a likely consequence of suppressed EMT-like changes.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

Suppression of Endothelial-to-Mesenchymal Transition by SIRT (Sirtuin) 3 Alleviated the Development of Hypertensive Renal Injury

Endothelial-to-mesenchymal transition (EndoMT) has recently emerged as a potentially important contributor in promoting fibrosis in chronic kidney disease. However, little is known about the role and molecular basis of its involvement in hypertensive renal injury. Here, we aim to determine the role of SIRT (sirtuin) 3 on EndoMT in hypertensive renal injury and to explore its underlying mechanisms. We found that SIRT3 expression was significantly reduced in Ang II (angiotensin II)-induced hypertensive model, accompanied with induction of EndoMT and increased reactive oxygen species and renal fibrosis. In SIRT3^-/- (SIRT3 knockout) mice subjected to Ang II infusion, renal dysfunction was aggravated with an increased EndoMT and reactive oxygen species level, whereas in SIRT3-Tg^EC (SIRT3 endothelial cell-specific transgenic) mice, the Ang II-induced renal fibrosis and EndoMT and oxidative stress were ameliorated. With primary mouse glomerular endothelial cells, we confirmed that Ang II treatment initiated EndoMT and decreased catalase expression, which were suppressed by SIRT3 overexpression. Using immunoprecipitation, luciferase, and chromatin immunoprecipitation assay, we demonstrated that SIRT3-mediated deacetylation and nuclear localization of Foxo3a (forkhead box O3a) resulted in activated Foxo3a-dependent catalase expression. Moreover, Foxo3a knockdown abolished SIRT3-mediated suppression of EndoMT. In conclusion, these results established the SIRT3-Foxo3a-catalase pathway as a critical factor in the maintenance of endothelial homeostasis and point to an important role of EndoMT in the vascular pathology of renal fibrosis, which may provide a new therapeutic target to impede the progression of hypertensive renal injury.

Endothelial Cells May Have Tissue-Specific Origins

Endothelial heterogeneity reflects many functions performed by endothelial cells (ECs) in various tissues. However, the origin of this heterogeneity is unclear. Here, we report that tissue-specific ECs in lungs, brain and liver co-expressed the lineage markers of their coordinating tissue-specific cells at very early stages. Specifically, we found that the pulmonary EC population was significantly suppressed after pulmonary epithelial-specific (Nkx2.1-Cre mediated) deletion of fetal liver kinase-1 (Flk1). Together, the results suggest that tissues-specific ECs may originate from the same progenitor cells as tissue-specific cells.

Downregulation of the S1P Transporter Spinster Homology Protein 2 (Spns2) Exerts an Anti-Fibrotic and Anti-Inflammatory Effect in Human Renal Proximal Tubular Epithelial Cells

Sphingosine kinase (SK) catalyses the formation of sphingosine 1-phosphate (S1P), which acts as a key regulator of inflammatory and fibrotic reactions, mainly via S1P receptor activation. Here, we show that in the human renal proximal tubular epithelial cell line HK2, the profibrotic mediator transforming growth factor β (TGFβ) induces SK-1 mRNA and protein expression, and in parallel, it also upregulates the expression of the fibrotic markers connective tissue growth factor (CTGF) and fibronectin. Stable downregulation of SK-1 by RNAi resulted in the increased expression of CTGF, suggesting a suppressive effect of SK-1-derived intracellular S1P in the fibrotic process, which is lost when SK-1 is downregulated. In a further approach, the S1P transporter Spns2, which is known to export S1P and thereby reduces intracellular S1P levels, was stably downregulated in HK2 cells by RNAi. This treatment decreased TGFβ-induced CTGF and fibronectin expression, and it abolished the strong induction of the monocyte chemotactic protein 1 (MCP-1) by the pro-inflammatory cytokines tumor necrosis factor (TNF)α and interleukin (IL)-1β. Moreover, it enhanced the expression of aquaporin 1, which is an important water channel that is expressed in the proximal tubules, and reverted aquaporin 1 downregulation induced by IL-1β/TNFα. On the other hand, overexpression of a Spns2-GFP construct increased S1P secretion and it resulted in enhanced TGFβ-induced CTGF expression. In summary, our data demonstrate that in human renal proximal tubular epithelial cells, SK-1 downregulation accelerates an inflammatory and fibrotic reaction, whereas Spns2 downregulation has an opposite effect. We conclude that Spns2 represents a promising new target for the treatment of tubulointerstitial inflammation and fibrosis.

Parabiosis and single-cell RNA sequencing reveal a limited contribution of monocytes to myofibroblasts in kidney fibrosis

Fibrosis is the common final pathway of virtually all chronic injury to the kidney. While it is well accepted that myofibroblasts are the scar-producing cells in the kidney, their cellular origin is still hotly debated. The relative contribution of proximal tubular epithelium and circulating cells, including mesenchymal stem cells, macrophages, and fibrocytes, to the myofibroblast pool remains highly controversial. Using inducible genetic fate tracing of proximal tubular epithelium, we confirm that the proximal tubule does not contribute to the myofibroblast pool. However, in parabiosis models in which one parabiont is genetically labeled and the other is unlabeled and undergoes kidney fibrosis, we demonstrate that a small fraction of genetically labeled renal myofibroblasts derive from the circulation. Single-cell RNA sequencing confirms this finding but indicates that these cells are circulating monocytes, express few extracellular matrix or other myofibroblast genes, and express many proinflammatory cytokines. We conclude that this small circulating myofibroblast progenitor population contributes to renal fibrosis by paracrine rather than direct mechanisms.

Placental growth factor promotes epithelial-mesenchymal transition-like changes in ARPE-19 cells under hypoxia

Purpose

To investigate the role of placental growth factor (PGF) in the epithelial-mesenchymal transition (EMT) of ARPE-19 cells under hypoxia, and whether the NF-κB signaling pathway is involved in this process.

Methods

ARPE-19 cells were treated in five groups: a control group, hypoxia group, PGF group, hypoxia+PGF group, and NF-κB-blocked group. A chemical hypoxia model was established in the ARPE-19 cells by adding CoCl₂ to the culture medium. The morphological changes after treatment were observed. The proliferation rates were measured with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The migration abilities were measured with scratch assay. The EMT biomarkers were measured with quantitative real-time PCR (qRT-PCR), western blotting, and immunofluorescence. The relative protein expression of components of the NF-κB signaling pathway was measured with western blotting and immunofluorescence.

Results

Cells treated with PGF under hypoxia exhibited morphological changes consistent with the transition from an epithelial to a mesenchymal phenotype. In the ARPE-19 cells, exogenous PGF under hypoxia increased the proliferation rate compared to the rate under hypoxia alone (p<0.05) and increased the migration rate (p<0.05). Treatment of hypoxia-exposed cells with PGF caused decreased expression of the epithelial biomarkers E-cadherin and ZO-1 (both p<0.05) and increased expression of the mesenchymal marker α-SMA (p<0.05) by enhancing the phosphorylation of NF-κB p65 of the total protein, promoting the translocation of p65 to the nucleus, and inducing the degradation of IκB-α (a negative regulator of the NF-κB pathway) in the ARPE-19 cells. Additionally, the effect of PGF-induced EMT in the ARPE-19 cells under hypoxia was counteracted with BAY 11-7082 (a selective NF-κB inhibitor).

Conclusions

Exogenous PGF promotes EMT-like changes in ARPE-19 cells under hypoxia by activating the NF-κB signaling pathway. The study results suggest that PGF may play a role in scar formation in neovascular age-related macular degeneration (AMD) and that the inhibition of PGF may be a promising target for the prevention and treatment of AMD.

Urinary RKIP/p-RKIP is a potential diagnostic and prognostic marker of clear cell renal cell carcinoma

Clear cell Renal Cell Carcinoma (ccRCC) causes over 13,000 deaths each year, and about 20,000 new cases/year in Europe. In most cases, the causes are unknown and, most importantly, there are no reliable biomarkers for the diagnosis and prognosis of this disease. The search for sensitive biomarkers for early diagnosis and prognosis of clear cell Renal Cell Carcinoma (ccRCC) is currently a fast growing field. We carried out proteomics analysis of 93 urinary samples of healthy subjects (HS) and patients affected by ccRCC, prostate cancer (PCa) and chronic kidney disease (CKD), that was able to successfully distinguish each group.

The most significant candidate biomarker was identified by mass spectrometry as Raf Kinase Inhibitor Protein (RKIP), a key regulator of cell signaling, already described in several cancer types as a metastasis suppressor. By combining ELISA, immunoblotting and tissue microarray, we demonstrated that, in ccRCC, urinary excretion of RKIP and its phosphorylated form (p-RKIP) reflected the tissue expression of these putative biomarkers. Baseline urinary RKIP, evaluated in an independent cohort of 56 ccRCC patients and 28 HS, successfully distinguished both groups and, most importantly, a cut-off value of 10 ng/mg/g Pr/uCr enabled a highly accurate prediction of Cancer-specific survival and Progression-free survival. Furthermore, p-RKIP was totally undetectable in both tissue and urine samples of ccRCC, showing a great potential for diagnostics purposes.

Our data indicate that urinary RKIP encompasses both the unphosphorylated and the phosphorylated form and that their combined evaluation can help in the diagnosis and prognosis of ccRCC.

Targeting renal fibrosis: Mechanisms and drug delivery systems

Renal fibrosis is the common outcome of many chronic kidney diseases (CKD) independent of the underlying etiology. Despite a host of promising experimental data, currently available strategies only ameliorate or delay the progression of CKD but do not reverse fibrosis. One of the major impediments of translating novel antifibrotic strategies from bench to bedside is due to the intricacies of the drug delivery process. In this review, we briefly describe mechanisms of renal fibrosis and methods of drug transfer into the kidney. Various tools used in gene therapy to administer nucleic acids in vivo are discussed. Furthermore, we review the modes of action of protein- or peptide-based drugs with target-specific antibodies and cytokines incorporated in hydrogels. Additionally, we assess an intriguing new method to deliver drugs specifically to tubular epithelial cells via conjugation with ligands binding to the megalin receptor. Finally, plant-derived compounds with antifibrotic properties are also summarized.

Progression of chronic kidney disease in children - role of glomerular hemodynamics and interstitial fibrosis

PURPOSE OF REVIEW

The aim of this review is to provide an overview of the current advances in the understanding of the mechanisms involved in the progression of chronic kidney disease (CKD) with emphasis on the role of glomerular hemodynamics and tubulointerstitial fibrosis.

RECENT FINDINGS

Despite the varied causes of CKD, the progressive destruction of renal tissue processes through a complex common pathway. Current studies have highlighted both the role of the abnormal intrarenal hemodynamics and of the activation of fibrogenic biochemical pathway in the replacement of normal renal structure by extracellular matrix and ultimately by fibrosis. Molecular markers with the potential to contribute to the detection of tubular cell damage and tubulointerstitial fibrosis in the kidney has been identified.

SUMMARY

There is a clear need to understand and elucidate the mechanisms of progression of CKD to develop efficient therapeutic strategies to halt decline of renal function in children.

Adenovirus-mediated P311 ameliorates renal fibrosis through inhibition of epithelial-mesenchymal transition via TGF-β1-Smad-ILK pathway in unilateral ureteral obstruction rats

Epithelial-mesenchymal transition (EMT) is a critical step and key factor during renal fibrosis. Preventing renal tubular EMT is important for delaying the progression of chronic kidney disease (CKD). P311, a highly conserved 8-kDa intracellular protein, has been indicated as an important factor in myofibroblast transformation and in the progression of fibrosis. However, the related studies on P311 on renal fibrosis are limited and the mechanisms of P311 in the progression of renal tubulointerstitial fibrosis remain largely unknown. In the present study, we examined the effect of P311 on transforming growth factor-β1 (TGF-β1)-mediated EMT in a rat model of unilateral ureteral occlusion (UUO) renal fibrosis. The recombinant adenovirus p311 (also called Ad-P311) was constructed and transferred it into UUO rats, the preventive effect and possible mechanism of P311 on TGF-β1-mediated EMT were explored. The UUO model was established successfully and Ad-P311 was administered into UUO rats each week for 4 weeks, then the serum levels of Cr, blood urea nitrogen (BUN) and albumin (ALB) were evaluated. H&E staining and Masson staining were performed to observe the pathological changes of kidneys. Immunohistochemical staining and western blot analysis were used to examine the EMT markers [E-cadherin and α-smooth muscle actin (α-SMA)], and signal transducers (p-Smad2/3 and Smad7). Integrin linked kinase (ILK) as a keyintracellular mediator that controls TGF-β1-mediated-EMT was also assayed by western blot analysis. The results showed that P311 could alleviate renal tubular damage and interstitial fibrosis improving Cr, BUN and ALB serum levels in UUO kidneys. Furthermore, P311 attenuated TGF-β1-mediated EMT through Smad-ILK signaling pathway with an increase in α-SMA, pSmad2/3 and ILK expression, and a decrease in E-cadherin and Smad7 expression in UUO kidneys. In conclusion, P311 may be involved in the pathogenesis of renal fibrosis by blocking TGF-β1-mediated EMT via TGF-β1-Smad-ILK pathway in UUO kidneys. P311 may be a novel target for the control of renal fibrosis and the progression of CKD.

Similar Characteristics of Endometrial and Endometriotic Epithelial Cells

Epithelial-mesenchymal transition (EMT) is characterized by the loss of epithelial and acquisition of mesenchymal cell characteristics. Our aim was to assess the epithelial phenotype in the pathogenesis of endometriosis with epithelial and mesenchymal markers. We used 2 structural (keratin-18, -19 [K18, K19]), 1 membrane-associated (mucin-1 [MUC1]), and 2 mesenchymal proteins (vimentin; zinc finger E-box-binding homeobox 1, [ZEB1]) to compare epithelial and mesenchymal characteristics in eutopic endometrium with the 3 endometriotic entities, peritoneal, ovarian, and deep infiltrating endometriosis (DIE). Quantitation showed no differences for K18, K19, and MUC1 between endometrium with and without endometriosis. Also, K18 was not different between endometrium and endometriotic lesions. In contrast, K19 and MUC1 were modestly but significantly decreased in the endometriotic lesions compared to endometrium. However, the maintained expression of epithelial markers in all investigated tissues, regardless of the pathological condition, clearly indicates no loss of the epithelial phenotype. This is further supported by the reduced presence of epithelial vimentin in endometriotic lesions which is in contrast to an increase in stromal vimentin in ectopic endometrium, especially in ovarian endometriosis. The ZEB1 increase in endometriotic lesions, especially in DIE, on the other hand suggests a role of partial EMT in the development of endometriotic lesions, possibly connected with the gain of invasive capabilities or stemness. Taken together, although we found some hints for at least a partial EMT, we did not observe a severe loss of the epithelial cell phenotype. Thus, we propose that EMT is not a main factor in the pathogenesis of endometriosis.

Sphingolipid signaling in renal fibrosis

Over the last decade, various sphingolipid subspecies have gained increasing attention as important signaling molecules that regulate a multitude of physiological and pathophysiological processes including inflammation and tissue remodeling. These mediators include ceramide, sphingosine 1-phosphate (S1P), the cerebroside glucosylceramide, lactosylceramide, and the gangliosides GM3 and Gb3. These lipids have been shown to accumulate in various chronic kidney diseases that typically end in renal fibrosis and ultimately renal failure. This review will summarize the effects and contributions of those enzymes that regulate the generation and interconversion of these lipids, notably the acid sphingomyelinase, the acid sphingomyelinase-like protein SMPDL3B, the sphingosine kinases, the S1P lyase, the glucosylceramide synthase, the GM3 synthase, and the α-galactosidase A, to renal fibrotic diseases. Strategies of manipulating these enzymes for therapeutic purposes and the impact of existing drugs on renal pathologies will be discussed.

Angiopoietin-1 deficiency increases renal capillary rarefaction and tubulointerstitial fibrosis in mice

Presence of tubulointerstitial fibrosis is predictive of progressive decline in kidney function, independent of its underlying cause. Injury to the renal microvasculature is a major factor in the progression of fibrosis and identification of factors that regulate endothelium in fibrosis is desirable as they might be candidate targets for treatment of kidney diseases. The current study investigates how loss of Angipoietin-1 (Angpt1), a ligand for endothelial tyrosine-kinase receptor Tek (also called Tie2), affects tubulointerstitial fibrosis and renal microvasculature. Inducible Angpt1 knockout mice were subjected to unilateral ureteral obstruction (UUO) to induce fibrosis, and kidneys were collected at different time points up to 10 days after obstruction. Staining for aSMA showed that Angpt1 deficient kidneys had significantly more fibrosis compared to wildtype mice 3, 6, and 10 days after UUO. Further investigation 3 days after UUO showed a significant increase of Col1a1 and vimentin in Angpt1 deficient mice, as well as increased gene expression of Tgfb1, Col1a1, Fn1, and CD44. Kidney injury molecule 1 (Kim1/Havcr1) was significantly more increased in Angpt1 deficient mice 1 and 3 days after UUO, suggesting a more severe injury early in the fibrotic process in Angpt1 deficient mice. Staining for endomucin showed that capillary rarefaction was evident 3 days after UUO and Angpt1 deficient mice had significantly less capillaries 6 and 10 days after UUO compared to UUO kidneys in wildtype mice. RNA sequencing revealed downregulation of several markers for endothelial cells 3 days after UUO, and that Angpt1 deficient mice had a further downregulation of Emcn, Plvap, Pecam1, Erg, and Tek. Our results suggest that loss of Angpt1 is central in capillary rarefaction and fibrogenesis and propose that manipulations to maintain Angpt1 levels may slow down fibrosis progression.

Involvement of epithelial-mesenchymal transition in liver fibrosis

Fibrosis of the liver is an inherent wound healing response to chronic liver injury. Regeneration of liver epithelium and restoration of normal liver structure were generally involved in this process. Although the liver has a striking capacity to adapt to damage through tissue repair, excessive accumulation of extracellular matrix during this process often leads to scar tissue formation and subsequent fibrosis. Epithelial to mesenchymal transition (EMT) enables a polarized epithelial cell to undergo multiple changes biochemically and to bear a mesenchymal cell phenotype. EMT plays a critical role in tissue and organ development and embryogenesis. In the liver, it is proposed that epithelial cells can acquire fibroblastic phonotype via EMT and contribute to fibrogenesis. This made EMT a potential target for antifibrotic strategies. Following an original passion, many investigators devote themselves to exploring this mechanism in liver fibrosis. However, as research continues, this hypothesis became highly controversial. The exact contribution of EMT to fibrogenesis was challenged due to the contradictory results from related studies. In this review, we summarized the recent advances regarding EMT in hepatic fibrosis and discussed the potentially involved liver cell types and pathways in order to reach rational and helpful conclusions.

Cryptotanshinone hinders renal fibrosis and epithelial transdifferentiation in obstructive nephropathy by inhibiting TGF-β1/Smad3/integrin β1 signal

Recent studies have reported that CTS can alleviate cardiac fibrosis. However, the effects of CTS on kidney fibrosis and EMT are still unknown. This study explored whether CTS could attenuate tubulointerstitial fibrosis as well as EMT, and investigated the potential underlying mechanisms. In this study, an in vivo UUO mouse model and an in vitro TGF-β1 stimulated normal renal tubular kidney epithelial cell model were established. In UUO model, administration of 50 mg kg-1 day-1 CTS markedly decreased the occurrence of kidney injury and the accumulation of fibronectin and collagen-1. In addition, CTS reduced the expression level of α-SMA but retained E-cadherin in obstructed kidneys. In vitro, CTS suppressed the expression of fibronectin, collagen-1 and α-SMA but retained that of E-cadherin. Furthermore, CTS selectively abolished the activation of Smad3 and suppressed the nuclear translocation of Smad2, Smad3 and Smad4. CTS could block the promoter activity of integrin β1 induced by Smad3. Furthermore, CTS inhibited Smad3 binding to integrin β1 promoter sequences. These data suggest that CTS can ameliorate kidney fibrosis and EMT, at least in part, by inhibiting the TGF-β1/Smad3/integrin β1 signaling pathway.

Epithelial Mesenchymal Transition in Embryonic Development, Tissue Repair and Cancer: A Comprehensive Overview

The epithelial mesenchymal transition (EMT) plays a central role in both normal physiological events (e.g., embryonic development) and abnormal pathological events (e.g., tumor formation and metastasis). The processes that occur in embryonic development are often reactivated under pathological conditions such as oncogenesis. Therefore, defining the regulatory networks (both gene and protein levels) involved in the EMT during embryonic development will be fundamental in understanding the regulatory networks involved in tumor development, as well as metastasis. There are many molecules, factors, mediators and signaling pathways that are involved in the EMT process. Although the EMT is a very old topic with numerous publications, recent new technologies and discoveries give this research area some new perspective and direction. It is now clear that these important processes are controlled by a network of transcriptional and translational regulators in addition to post-transcriptional and post-translational modifications that amplify the initial signals. In this review article, we will discuss some key concepts, historical findings, as well as some recent progresses in the EMT research field.

Immunologic and endocrine functions of adipose tissue: implications for kidney disease

Excess adiposity can induce adverse sequelae in multiple cell types and organ systems. The transition from the lean to the obese state is characterized by fundamental cellular changes at the level of the adipocyte. These changes affect the local microenvironment within the respective adipose tissue but can also affect nonadipose systems. Adipocytes within fat pads respond to chronic nutrient excess through hyperplasia or hypertrophy, which can differentially affect interorgan crosstalk between various adipose depots and other organs. This crosstalk is dependent on the unique ability of the adipocyte to coordinate metabolic adjustments throughout the body and to integrate responses to maintain metabolic homeostasis. These actions occur through the release of free fatty acids and metabolites during times of energy need - a process that is altered in the obese state. In addition, adipocytes release a wide array of signalling molecules, such as sphingolipids, as well as inflammatory and hormonal factors (adipokines) that are critical for interorgan crosstalk. The interactions of adipose tissue with the kidney - referred to as the adipo-renal axis - are important for normal kidney function as well as the response of the kidney to injury. Here, we discuss the mechanistic basis of this interorgan crosstalk, which clearly has great therapeutic potential given the increasing rates of chronic kidney disease secondary to obesity and type 2 diabetes mellitus.

Modulation of the TGF-β1-induced epithelial to mesenchymal transition (EMT) mediated by P1 and P2 purine receptors in MDCK cells

Epithelial to mesenchymal transition (EMT) occurs during embryogenesis or under pathological conditions such as hypoxia, injury, chronic inflammation, or tissue fibrosis. In renal tubular epithelial cells (MDCK), TGF-β1 induces EMT by reducing or increasing epithelial or mesenchymal marker expression, respectively. In this study, we confirmed that the cAMP analogues, 8-CPT-cAMP or N6-Ph-cAMP, inhibited the TGF-β1-driven overexpression of the mesenchymal markers ZEB-1, Slug, Fibronectin, and α-SMA. Furthermore, we showed that A1, A2A, P2Y1, P2Y11, and P2X7 purine receptor agonists modulated the TGF-β1-induced EMT through the involvement of PKA and/or MAPK/ERK signaling. The stimulation of A2A receptor reduced the overexpression of the EMT-related markers, mainly through the cAMP-dependent PKA pathway, as confirmed by cell pre-treatment with Myr-PKI. Both A1 and P2Y1 receptor stimulation exacerbated the TGF-β1-driven effects, which were reduced by cell pre-treatment with the MAPK inhibitor PD98059, according to the increased ERK1/2 phosphorylation upon receptor activation. The effects induced by P2Y11 receptor activation were oppositely modulated by PKA or MAPK inhibition, in line with the dual nature of the Gs- and Gq-coupled receptor. Differently, P2X7 receptor induced, per se, similar and not additive effects compared to TGF-β1, after prolonged cell exposure to BzATP. These results suggest a putative role of purine receptors as target for anti-fibrotic agents.

FHL2 promotes tubular epithelial-to-mesenchymal transition through modulating β-catenin signalling

β-Catenin signalling plays an important role in regulating tubular epithelial-to-mesenchymal transition (EMT), an indispensable programme for driving renal fibrosis. As an adapter protein, four and a half LIM domain protein 2 (FHL2) acts as a coregulator of β-catenin in several other cell types. To determine whether FHL2 affects β-catenin signalling and thus is involved in tubular EMT, we examined its expression and function in the process of TGF-β1-induced EMT. FHL2 mRNA and protein were induced by TGF-β1 in rat tubular epithelial cells (NRK-52E), an effect that intracellular Smad signalling was required. Ectopic expression of FHL2 inhibited E-cadherin and enhanced α-smooth muscle actin (α-SMA) and fibronectin expression, whereas knockdown of FHL2 partially restored E-cadherin and reduced α-SMA and fibronectin induction stimulated by TGF-β1. Overexpression of FHL2 increased β-catenin dephosphorylation (Ser37/Thr41), nuclear translocation and β-catenin-mediated transcription and up-regulated expression of β-catenin target, EMT-related genes, such as Snail, Twist, vimentin, plasminogen activator inhibitor-1 and matrix metalloproteinase-7. Conversely, knockdown of FHL2 increased β-catenin phosphorylation (Ser33/37/Thr41), decreased its nuclear translocation and inhibited β-catenin-mediated transcription and target genes expression. TGF-β1 induced a FHL2/β-catenin interaction in NRK-52E cells, especially in the nuclei. In a mouse model of obstructive nephropathy, FHL2 mRNA and protein were induced in a time-dependent fashion, and the extent and pattern of renal β-catenin activation were positively correlated with FHL2 induction. Collectively, this study suggests that FHL2, via modulating β-catenin signalling, may implicate in regulation of TGF-β1-mediated tubular EMT and could be a potential therapeutic target for fibrotic kidney disease.

Triptolide suppresses paraquat induced idiopathic pulmonary fibrosis by inhibiting TGFB1-dependent epithelial mesenchymal transition

Idiopathic pulmonary fibrosis (IPF) and tumor are highly similar to abnormal cell proliferation that damages the body. This malignant cell evolution in a stressful environment closely resembles that of epithelial-mesenchymal transition (EMT). As a popular EMT-inducing factor, TGFβ plays an important role in the progression of multiple diseases. However, the drugs that target TGFB1 are limited. In this study, we found that triptolide (TPL), a Chinese medicine extract, exerts an anti-lung fibrosis effect by inhibiting the EMT of lung epithelial cells. In addition, triptolide directly binds to TGFβ and subsequently increase E-cadherin expression and decrease vimentin expression. In in vivo studies, TPL improves the survival state and inhibits lung fibrosis in mice. In summary, this study revealed the potential therapeutic effect of paraquat induced TPL in lung fibrosis by regulating TGFβ-dependent EMT progression.

Hypoxia inducible factor-1α mediates the profibrotic effect of albumin in renal tubular cells

Proteinuria is closely associated with the progression of chronic kidney diseases (CKD) by producing renal tubulointerstitial fibrosis. Over-activation of hypoxia inducible factor (HIF)-1α has been implicated in the progression of CKD. The present study tested the hypothesis that HIF-1α mediates albumin-induced profibrotic effect in cultured renal proximal tubular cells. Incubation of the cells with albumin (40 μg/ml) for 72 hrs significantly increased the protein levels of HIF-1α, tissue inhibitor of metalloproteinase (TIMP)-1 and collagen-I, which were blocked by HIF-1α shRNA. Albumin also stimulated an epithelial-mesenchymal transition (EMT) as indicated by the decrease in epithelial marker E-cadherin, and the increase in mesenchymal markers α-smooth muscle actin and fibroblast-specific protein 1. HIF-1α shRNA blocked albumin-induced changes in these EMT markers as well. Furthermore, albumin reduced the level of hydroxylated HIF-1α, indicating an inhibition of the activity of prolyl-hydroxylases, enzymes promoting the degradation of HIF-1α. An anti-oxidant ascorbate reversed albumin-induced inhibition of prolyl-hydroxylase activity. Overexpression of prolyl-hydroxylase 2 (PHD2) transgene, a predominant isoform of PHDs in renal tubules, to reduce HIF-1α level significantly attenuated albumin-induced increases in TIMP-1 and collagen-I levels. These results suggest that albumin-induced oxidative stress inhibits PHD activity to accumulate HIF-1α, which mediates albumin-induced profibrotic effects in renal tubular cells.

Therapeutic pro-fibrogenic signaling pathways in fibroblasts

Myofibroblasts (MFs) play a critical role in the progression of chronic inflammatory and fibroproliferative diseases in different tissues/organs, whatever the etiology. Fibrosis is preceded and sustained by persistent injury and inflammatory response in a profibrogenic scenario involving mutual interactions, operated by several mediators and pathways, of MFs and related precursor cells with innate immunity cells and virtually any cell type in a defined tissue. These interactions, mediators and related signaling pathways are critical in initiating and perpetuating the differentiation of precursor cells into MFs that in different tissues share peculiar traits and phenotypic responses, including the ability to proliferate, produce ECM components, migrate and contribute to the modulation of inflammatory response and tissue angiogenesis. Literature studies related to liver, lung and kidney fibrosis have outlined a number of MF-related core regulatory fibrogenic signaling pathways conserved across these different organs and potentially targetable in order to develop effective antifibrotic therapeutic strategies.

TGF-β-Induced Endothelial-Mesenchymal Transition in Fibrotic Diseases

Fibrotic diseases are characterized by net accumulation of extracellular matrix proteins in affected organs leading to their dysfunction and ultimate failure. Myofibroblasts have been identified as the cells responsible for the progression of the fibrotic process, and they originate from several sources, including quiescent tissue fibroblasts, circulating CD34⁺ fibrocytes and the phenotypic conversion of various cell types into activated myofibroblasts. Several studies have demonstrated that endothelial cells can transdifferentiate into mesenchymal cells through a process termed endothelial- mesenchymal transition (EndMT) and that this can give rise to activated myofibroblasts involved in the development of fibrotic diseases. Transforming growth factor β (TGF-β) has a central role in fibrogenesis by modulating the fibroblast phenotype and function, inducing myofibroblast transdifferentiation and promoting matrix accumulation. In addition, TGF-β by inducing EndMT may further contribute to the development of fibrosis. Despite extensive investigation of the pathogenesis of fibrotic diseases, no effective treatment strategies are available. Delineation of the mechanisms responsible for initiation and progression of fibrotic diseases is crucial for the development of therapeutic strategies for the treatment of the disease. In this review, we summarize the role of the TGF-β signaling pathway and EndMT in the development of fibrotic diseases and discuss their therapeutic potential.

Eucalyptol ameliorates Snail1/β-catenin-dependent diabetic disjunction of renal tubular epithelial cells and tubulointerstitial fibrosis

Renal tubulointerstitial fibrosis is an important event in the pathogenesis of diabetic nephropathy. Under pathologic conditions, renal tubular epithelial cells undergo transition characterized by loss of cell-cell adhesion and increased cell migration. This study investigated that eucalyptol inhibited tubular epithelial cell disjunction and tubulointerstitial fibrosis stimulated by glucose. Human renal proximal tubular epithelial cells were incubated for up to 72 h in media containing 27.5 mM mannitol as osmotic controls or 33 mM glucose in the presence of 1-20 μM eucalyptol. Nontoxic eucalyptol inhibited glucose-induced expression of the mesenchymal markers of N-cadherin and α-smooth muscle actin, whereas the induction of E-cadherin was enhanced. Eucalyptol attenuated the induction of connective tissue growth factor and collagen IV by glucose, whereas the membrane type 1-matrix metalloproteinase expression was enhanced with reducing tissue inhibitor of metalloproteinase-2 expression. Oral administration of 10 mg/kg eucalyptol to db/db mice for 8 weeks blunted hyperglycemia and proteinuria. Eucalyptol reversed tissue levels of E-cadherin, N-cadherin and P-cadherin and the collagen fiber deposition in diabetic kidneys. Eucalyptol attenuated the induction of Snail1, β-catenin and integrin-linked kinase 1 (ILK1) in glucose-exposed tubular cells and diabetic kidneys, and the glycogen synthase kinase (GSK)-3β expression was reversely enhanced. Glucose prompted TGF-β1 production in tubular cells, leading to induction of Snail1, β-catenin and ILK1, which was dampened by eucalyptol. Furthermore, the Snail1 gene deletion encumbered the β-catenin induction in glucose/eucalyptol-treated tubular cells accompanying enhanced GSK-3β expression. Therefore, eucalyptol may antagonize hyperglycemia-induced tubular epithelial derangement and tubulointerstitial fibrosis through blocking ILK1-dependent transcriptional interaction of Snail1/β-catenin.

Human induced pluripotent stem cell-derived mesenchymal stem cells prevent adriamycin nephropathy in mice

Human induced pluripotent stem cell-derived mesenchymal stem cells (iPS-MSCs) are emerging as attractive options for use in cell replacement therapy, but their effect in kidney diseases remains unknown. Here, we showed that intravenous injection of iPS-MSCs protect against renal function loss in both short-term and long-term models of adriamycin nephropathy (AN). In the short-term AN model, iPS-MSCs conferred a substantial anti-apoptotic effect on tubular cells, associated with a downregulation of Bax and Bax/Bcl2 ratio and an upregulation of survivin expression. In vitro, conditioned medium from iPS-MSCs (iPSMSC-CM) significantly limited albumin-induced tubular apoptosis and enhanced tubular proliferation, accompanied by a reduced expression of tubular Bax and an elevated expression of Bcl2 and survivin. Oxidative stress was markedly attenuated by iPS-MSCs both in AN mice and in protein-overloaded tubular cells. In the long-term AN model, repeated injections of iPS-MSCs significantly inhibited tubulointerstitial fibrosis and reduced intrarenal deposition of collagen I, collagen IV and αSMA. Modulation of the hedgehog signaling pathway contributed to the anti-fibrotic effect of iPS-MSCs in chronic AN. Finally, we detected that most of the infused iPS-MSCs were entrapped in the lungs. In conclusion, our data support a beneficial role of iPS-MSCs in both acute and chronic AN.

Erhuang Formula ameliorates renal damage in adenine-induced chronic renal failure rats via inhibiting inflammatory and fibrotic responses

AIMS

The present study aimed to evaluate the protective effects of Erhuang Formula (EHF) and explore its pharmacological mechanisms on adenine-induced chronic renal failure (CRF).

MATERIALS AND METHODS

The compounds in EHF were analyzed by HPLC/MS. Adenine-induced CRF rats were administrated by EHF. The effects were evaluated by renal function examination and histology staining. Immunostaining of some proteins related cell adhesion was performedin renal tissues, including E-cadherin, β-catenin, fibronectin and laminin. The qRT-PCR was carried out determination of gene expression related inflammation and fibrosis including NF-κB, TNF-α, TGF-β1, α-SMA and osteopontin (OPN).

RESULTS

Ten compounds in EHF were identified including liquiritigenin, farnesene, vaccarin, pachymic acid, cycloastragenol, astilbin, 3,5,6,7,8,3',4'-heptemthoxyflavone, physcion, emodin and curzerene. Abnormal renal function and histology had significant improvements by EHF treatment. The protein expression of β-catenin, fibronectin and laminin were significantly increased and the protein expression of E-cadherin significantly decreased in CRF groups. However, these protein expressions were restored to normal levels in EHF group. Furthermore, low expression of PPARγ and high expression of NF-κB, TNF-α, TGF-β1, α-SMA and OPN were substantially restored by EHF treatment in a dose-dependent manner.

CONCLUSIONS

EHF ameliorated renal damage in adenine-induced CRF rats, and the mechanisms might involve in the inhibition of inflammatory and fibrotic responses and the regulation of PPARγ, NF-κB and TGF-β signaling pathways.

An Attempt to Establish a Common Animal Model for Hepatorenal Fibrosis in Rats

It is already a proven fact that there exists a relationship between CLD (chronic liver disease) and kidney disease but still there is no available combined animal model of liver and kidney fibrosis on the same animal. An animal model is one of the important research tools in the field of medical science because it is important to build a model that can simulate the disease condition so that the particular disease can be studied. Therefore, the aim of this study is to build a less expensive, less time consuming, and reproducible model of hepatorenal fibrosis on rats. We administered combined intraperitoneal injection of CCl₄ (Carbon Tetrachloride) and BSA (Bovine Serum Albumin) on a female Wistar rats. At the end, the liver and kidney tissues were examined under microscope to see whether we were successful in establishing the model or not. The results show that liver fibrosis was marked but the changes on the kidneys were mild. In this study, we were able to induce significant fibrosis in the liver and early stages of fibrosis in the kidneys. The result also demonstrated that the addition of BSA conferred a liver protective effect against CCl₄ induced hepatotoxicity, whereas combination of CCl₄ and BSA proved to be detrimental for kidneys.

Metformin ameliorates the Phenotype Transition of Peritoneal Mesothelial Cells and Peritoneal Fibrosis via a modulation of Oxidative Stress

Phenotype transition of peritoneum is an early mechanism of peritoneal fibrosis. Metformin, 5′-adenosine monophosphate-activated protein kinase (AMPK) activator, has recently received a new attention due to its preventive effect on organ fibrosis and cancer metastasis by inhibiting epithelial-to-mesenchymal transition (EMT). We investigated the effect of metformin on EMT of human peritoneal mesothelial cells (HPMC) and animal model of peritoneal dialysis (PD). TGF-β1-induced EMT in HPMC was ameliorated by metformin. Metformin alleviated NAPDH oxidase- and mitochondria-mediated ROS production with an increase in superoxide dismutase (SOD) activity and SOD2 expression. Metformin inhibited the activation of Smad2/3 and MAPK, GSK-3β phosphorylation, nuclear translocalization of β-catenin and Snail in HPMCs. Effect of metformin on TGF-β1-induced EMT was ameliorated by either AMPK inhibitor or AMPK gene silencing. Another AMPK agonist, 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide partially blocked TGF-β1-induced EMT. In animal model of PD, intraperitoneal metformin decreased the peritoneal thickness and EMT with an increase in ratio of reduced to oxidized glutathione and the expression of SOD whereas it decreased the expression of nitrotyrosine and 8-hydroxy-2′-deoxyguanosine. Therefore, a modulation of AMPK in peritoneum can be a novel tool to prevent peritoneal fibrosis by providing a favorable oxidant/anti-oxidant milieu in peritoneal cavity and ameliorating phenotype transition of peritoneal mesothelial cells.

TRAP1 ameliorates renal tubulointerstitial fibrosis in mice with unilateral ureteral obstruction by protecting renal tubular epithelial cell mitochondria

Mitochondrial dysfunction causes renal tubular epithelial cell injury and promotes cell apoptosis and renal tubulointerstitial fibrosis (TIF) progression. TNF receptor-associated protein 1 (TRAP1) is a molecular chaperone protein that is localized in mitochondria. It plays an important role in cell apoptosis; however, its functional mechanism in TIF remains unclear. In this study, we observed the effects of TRAP1 in renal tubular epithelial cell mitochondria in mice with unilateral ureteral obstruction and its function in cell apoptosis and TIF. Results show that TRAP1 could protect the mitochondrial structure in renal tubular epithelial cells; maintain the levels of mitochondrial membrane potential, ATP, and mitochondrial DNA copy number; inhibit reactive oxygen species production; stabilize the expression of the mitochondrial inner membrane protein mitofilin; reduce renal tubular epithelial cell apoptosis; and inhibit TIF. These results provide new theoretical foundations for additional understanding of the antifibrotic mechanism of TRAP1 in the kidney.-Chen, J.-F., Wu, Q.-S., Xie, Y.-X., Si, B.-L., Yang, P.-P., Wang, W.-Y., Hua, Q., He, Q. TRAP1 ameliorates renal tubulointerstitial fibrosis in mice with unilateral ureteral obstruction by protecting renal tubular epithelial cell mitochondria.

Defective CFTR leads to aberrant β-catenin activation and kidney fibrosis

Cystic fibrosis transmembrane conductance regulator (CFTR), known as a cAMP-activated Cl⁻ channel, is widely expressed at the apical membrane of epithelial cells in a wide variety of tissues. Of note, despite the abundant expression of CFTR in mammalian kidney, the role of CFTR in kidney disease development is unclear. Here, we report that CFTR expression is downregulated in the UUO (unilateral ureteral obstruction)-induced kidney fibrosis mouse model and human fibrotic kidneys. Dysfunction or downregulation of CFTR in renal epithelial cells leads to alteration of genes involved in Epithelial-Mesenchymal Transition (EMT) and kidney fibrosis. In addition, dysregulation of CFTR activates canonical Wnt/β-catenin signaling pathways, whereas the β-catenin inhibitor reverses the effects of CFTR downregulation on EMT marker. More interestingly, CFTR interacts with Dishevelled 2 (Dvl2), a key component of Wnt signaling, thereby suppressing the activation of β-catenin. Compared to wild type, deltaF508 mice with UUO treatment exhibit significantly higher β-catenin activity with aggregated kidney fibrogenesis, which is reduced by forced overexpression of CFTR. Taken together, our study reveals a novel mechanism by which CFTR regulates Wnt/β-catenin signaling pertinent to progression of kidney fibrosis and indicates a potential treatment target.