Epithelial to mesenchymal transition during late deterioration of human kidney transplants: the role of tubular cells in fibrogenesis

Epithelial-mesenchymal transition in tissue repair and degeneration

Epithelial-mesenchymal transitions (EMTs) are the epitome of cell plasticity in embryonic development and cancer; during EMT, epithelial cells undergo dramatic phenotypic changes and become able to migrate to form different tissues or give rise to metastases, respectively. The importance of EMTs in other contexts, such as tissue repair and fibrosis in the adult, has become increasingly recognized and studied. In this Review, we discuss the function of EMT in the adult after tissue damage and compare features of embryonic and adult EMT. Whereas sustained EMT leads to adult tissue degeneration, fibrosis and organ failure, its transient activation, which confers phenotypic and functional plasticity on somatic cells, promotes tissue repair after damage. Understanding the mechanisms and temporal regulation of different EMTs provides insight into how some tissues heal and has the potential to open new therapeutic avenues to promote repair or regeneration of tissue damage that is currently irreversible. We also discuss therapeutic strategies that modulate EMT that hold clinical promise in ameliorating fibrosis, and how precise EMT activation could be harnessed to enhance tissue repair.

Beclin-1 dependent autophagy improves renal outcomes following Unilateral Ureteral Obstruction (UUO) injury

Background

Interstitial Fibrosis and Tubular Atrophy (IFTA) is the most common cause of long-term graft failure following renal transplant. One of the hallmarks of IFTA is the development of interstitial fibrosis and loss of normal renal architecture. In this study, we evaluated the role of autophagy initiation factor Beclin-1 in protecting against post-renal injury fibrosis.

Methods

Adult male wild type (WT) C57BL/6 mice were subjected to Unilateral Ureteral Obstruction (UUO), and kidney tissue samples were harvested at 72-hour, 1- and 3-week post-injury. The UUO-injured and uninjured kidney samples were examined histologically for fibrosis, autophagy flux, inflammation as well activation of the Integrated Stress Response (ISR). We compared WT mice with mice carrying a forced expression of constitutively active mutant form of Beclin-1, Becn1F121A/F121A .

Results

In all experiments, UUO injury induces a progressive development of fibrosis and inflammation. These pathological signs were diminished in Becn1F121A/F121A mice. In WT animals, UUO caused a strong blockage of autophagy flux, indicated by continuously increases in LC3II accompanied by an over 3-fold accumulation of p62 1-week post injury. However, increases in LC3II and unaffected p62 level by UUO were observed in Becn1F121A/F121A mice, suggesting an alleviation of disrupted autophagy. Beclin-1 F121A mutation causes a significant decrease in phosphorylation of inflammatory STING signal and limited production of IL6 and IFNγ, but had little effect on TNF-α, in response to UUO. Furthermore, activation of ISR signal cascade was detected in UUO-injured in kidneys, namely the phosphorylation signals of elF2S1 and PERK in addition to the stimulated expression of ISR effector ATF4. However, Becn1F121A/F121A mice did not reveal signs of elF2S1 and PERK activation under the same condition and had a dramatically reduced ATF level at 3-week post injury.

Conclusions

The results suggest that UUO causes a insufficient, maladaptive renal autophagy, which triggered downstream activation of inflammatory STING pathway, production of cytokines, and pathological activation of ISR, eventually leading to the development of fibrosis. Enhancing autophagy via Beclin-1 improved renal outcomes with diminished fibrosis, via underlying mechanisms of differential regulation of inflammatory mediators and control of maladaptive ISR.

Renal Cell-Targeted Drug Delivery Strategy for Acute Kidney Injury and Chronic Kidney Disease: A Mini-Review

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), have become a global public health concern associated with high morbidity, mortality, and healthcare costs. However, at present, very few effective and specific drug therapies are available, owing to the poor therapeutic efficacy and systemic side effects. Kidney-targeted drug delivery, as a potential strategy for solving these problems, has received great attention in the fields of AKI and CKD in recent years. Here, we review the literature on renal targeted, more specifically, renal cell-targeted formulations of AKI and CKD that offered biodistribution data. First, we provide a broad overview of the unique structural characteristics and injured cells of acute and chronic injured kidneys. We then separately summarize literature examples of renal targeted formulations according to the difference of target cells and elaborate on the appropriate formulation design criteria for AKI and CKD. Finally, we propose a hypothetic strategy to improve the renal accumulation of glomerular cell-targeted formulation by escaping the uptake of the reticuloendothelial system and provide some perspectives for future studies.

Cellular senescence inhibits renal regeneration after injury in mice, with senolytic treatment promoting repair

The ability of the kidney to regenerate successfully after injury is lost with advancing age, chronic kidney disease, and after irradiation. The factors responsible for this reduced regenerative capacity remain incompletely understood, with increasing interest in a potential role for cellular senescence in determining outcomes after injury. Here, we demonstrated correlations between senescent cell load and functional loss in human aging and chronic kidney diseases including radiation nephropathy. We dissected the causative role of senescence in the augmented fibrosis occurring after injury in aged and irradiated murine kidneys. In vitro studies on human proximal tubular epithelial cells and in vivo mouse studies demonstrated that senescent renal epithelial cells produced multiple components of the senescence-associated secretory phenotype including transforming growth factor β1, induced fibrosis, and inhibited tubular proliferative capacity after injury. Treatment of aged and irradiated mice with the B cell lymphoma 2/w/xL inhibitor ABT-263 reduced senescent cell numbers and restored a regenerative phenotype in the kidneys with increased tubular proliferation, improved function, and reduced fibrosis after subsequent ischemia-reperfusion injury. Senescent cells are key determinants of renal regenerative capacity in mice and represent emerging treatment targets to protect aging and vulnerable kidneys in man.

Inhibition of α1-adrenoceptor reduces TGF-β1-induced epithelial-to-mesenchymal transition and attenuates UUO-induced renal fibrosis in mice

Renal fibrosis is a common pathological hallmark of chronic kidney disease (CKD). Renal sympathetic nerve activity is elevated in patients and experimental animals with CKD and contributes to renal interstitial fibrosis in obstructive nephropathy. However, the mechanisms underlying sympathetic overactivation in renal fibrosis remain unknown. Norepinephrine (NE), the main sympathetic neurotransmitter, was found to promote TGF-β1-induced epithelial-mesenchymal transition (EMT) and fibrotic gene expression in the human renal proximal epithelial cell line HK-2. Using both genetic and pharmacological approaches, we identified that NE binds Gαq-coupled α1-adrenoceptor (α1-AR) to enhance EMT of HK-2 cells by activating p38/Smad3 signaling. Inhibition of p38 diminished the NE-exaggerated EMT process and increased the fibrotic gene expression in TGF-β1-treated HK-2 cells. Moreover, the pharmacological blockade of α1-AR reduced the kidney injury and renal fibrosis in a unilateral ureteral obstruction mouse model by suppressing EMT in the kidneys. Thus, sympathetic overactivation facilitates EMT of renal epithelial cells and fibrosis via the α1-AR/p38/Smad3 signaling pathway, and α1-AR inhibition may be a promising approach toward treating renal fibrosis.

[Morphological and immunohistochemical predictors of renal response to therapy patients with myeloma cast nephropathy and dialysis-dependent acute kidney injury]

AIM

Reveal morphological and immunohistochemical predictors of reversibility of dialysis-dependent acute kidney injury (AKI) in patients with myeloma cast nephropathy (MCN) based on the study of kidney biopsy.

MATERIALS AND METHODS

Renal pathological findings were studied in 36 patients with MCN and dialysis-dependent stage 3 AKI (AKIN, 2012). The study of biopsy samples was performed by a semi-quantitative and quantitative analysis using computer morphometry. The expression of E-cadherin, vimentin and-smooth muscle actin was determined immunohistochemically in the tubular cells and interstitium. Induction therapy for 26 patients was carried out to bortezomib-based programs; in 10 patients other schemes were used. A comparative analysis of morphological changes in nephrobiopathy depending on the renal response was performed in patients with achieved hematologic remission.

RESULTS

Improved renal function was observed only in patients with hematologic response to therapy. There were no differences in the number of sclerotic glomeruli, protein casts, the area of inflammatory interstitial infiltration, and the degree of acute tubular damage in patients with and without renal response. In patients with renal response compared with patients without improving renal function, the area of interstitial fibrosis was less (24.9% and 45.9%, respectively;p=0.001), and the area of E-cadherin expression was larger (15.9% and 7.1%, respectively;p=0.006). Interstitial fibrosis of 40% or more and/or the area of expression of E-cadherin less than 10% of the area of tubulo-interstitium have an unfavorable prognostic value in achieving a renal response in MCN.

CONCLUSION

If the interstitial fibrosis area is 40% or more and the expression area of E-cadherin is less than 10%, the probability of the absence of a renal response is 93.3% (OR=24.5) even when a hematological response to induction therapy is achieved. The number of protein casts, the prevalence of acute tubular damage and inflammatory interstitial infiltration have not prognostic value.

Blocking thrombospondin-1 signaling via CD47 mitigates renal interstitial fibrosis

Acute kidney injury triggers a complex cascade of molecular responses that can culminate in maladaptive repair and fibrosis. We have previously reported that the matrix protein thrombospondin-1 (TSP1), binding its high affinity its receptor CD47, promotes acute kidney injury. However, the role of this pathway in promoting fibrosis is less clear. Hypothesizing that limiting TSP1-CD47 signaling is protective against fibrosis, we interrogated this pathway in a mouse model of chronic ischemic kidney injury. Plasma and renal parenchymal expression of TSP1 in patients with chronic kidney disease was also assessed. We found that CD47^-/- mice or wild-type mice treated with a CD47 blocking antibody showed clear amelioration of fibrotic histological changes compared to control animals. Wild-type mice showed upregulated TSP1 and pro-fibrotic markers which were significantly abrogated in CD47^-/- and antibody-treated cohorts. Renal tubular epithelial cells isolated from WT mice showed robust upregulation of pro-fibrotic markers following hypoxic stress or exogenous TSP1, which was mitigated in CD47^-/- cells. Patient sera showed a proportionate correlation between TSP1 levels and worsening glomerular filtration rate. Immunohistochemistry of human kidney tissue demonstrated tubular and glomerular matrix localization of TSP1 expression in patients with CKD. These data suggest that renal tubular epithelial cells contribute to fibrosis by activating TSP1-CD47 signaling, and point to CD47 as a potential target to limit fibrosis following ischemic injury.

Submucosal Fibrotic Bands in Oral Lichen Planus: A Clinico-Pathological Investigation of a Newly Described Phenomenon

Fibrosis is a recognized complication of chronic inflammatory conditions, which has not yet been described in oral lichen planus. To describe characteristics of submucosal fibrotic bands in oral lichen planus. Prospective study. Patients with biopsy confirmed lichen planus were included. Clinical examination recorded fibrotic bands, mouth opening, vestibular depth loss, gingival recessions adjacent to band, lichen subtypes, areas of affected mucosa, extra-oral manifestations. Patients completed the Chronic Oral Mucosal Disease Questionnaire, with additional questions regarding stiffness, restricted opening, symptom frequency, time from diagnosis of lichen, co-existing medical conditions. 73 patients were included, 14 M, 59 F, age 28-84 (mean 61) years. Buccal fibrous bands were palpated in 22 (30.1%), 13 (59%) were bilateral. Self-reported restricted opening/stiffness were significantly associated with fibrous bands (36% Vs. 11% in controls, p = 0.02). Mouth opening less than 40 mm was recorded in only 2 (9%) with bands, none in controls. Reduced vestibular depth was significantly associated with bands (11 (50%) Vs 3 (6%) in controls, p = 0.0001).Gingival recessions adjacent to bands were recorded in 3 (13.6%). No association was demonstrated between fibrous bands and erosive lesions, extra oral involvement, smoking, age, visual analogue scale, quality of life questionaire and disease duration. Histological evaluation of one case each with and without band and control showed increased mean width of connective tissue. Submucous fibrous band is first described in the present study. It is common in oral lichen planus, may lead to feeling restricted mouth opening, stiffness, loss of vestibular depth and adjacent gingival recession.

Epithelial to mesenchymal transition in endomyocardial biopsies from orthotopic heart transplant recipients

Epithelial to mesenchymal transition (EMT) occurs when cells lose morphological features of epithelial cells, such as cell-to-cell adhesion, and gain features of mesenchymal cells, including elongation and flattening. These cells also lose expression of epithelial immunohistochemical markers. In this report, we present a 55-year-old Caucasian male patient who underwent orthotopic heart transplant and immunosuppressant therapy with tacrolimus and mycophenolic acid. Seven and a half months later, an endomyocardial biopsy revealed a hypercellular, atypical lesion. Evaluation was negative for acute cellular rejection and post-transplant lymphoproliferative disorder. Histopathologic features and immunohistochemical stains were consistent with EMT. We subsequently identified four additional cases of EMT in patients who underwent orthotopic heart transplantation and received a similar immune suppression regimen. EMTs have been reported to occur in lung and kidney allografts; however, this is the first known report describing this entity in a heart transplant recipient.

Fenofibrate Improved Interstitial Fibrosis of Renal Allograft through Inhibited Epithelial-Mesenchymal Transition Induced by Oxidative Stress

The best treatment for end-stage renal disease is renal transplantation. However, it is often difficult to maintain a renal allograft healthy for a long time following transplantation. Interstitial fibrosis and tubular atrophy (IF/TA) are significant histopathologic characteristics of a compromised renal allograft. There is no effective therapy to improve renal allograft function once IF/TA sets in. Although there are many underlying factors that can induce IF/TA, the pathogenesis of IF/TA has not been fully elucidated. It has been found that epithelial-mesenchymal transition (EMT) significantly contributes to the development of IF/TA. Oxidative stress is one of the main causes that induce EMT in renal allografts. In this study, we have used H₂O₂ to induce oxidative stress in renal tubular epithelial cells (NRK-52e) of rats. We also pretreated NRK-52e cells with an antioxidant (N-acetyl L-cysteine (NAC)) 1 h prior to the treatment with H₂O₂. Furthermore, we used fenofibrate (a peroxisome proliferator-activated receptor α agonist) to treat NRK-52e cells and a renal transplant rat model. Our results reveal that oxidative stress induces EMT in NRK-52e cells, and pretreatment with NAC can suppress EMT in these cells. Moreover, fenofibrate suppresses fibrosis by ameliorating oxidative stress-induced EMT in a rat model. Thus, fenofibrate may effectively prevent the development of fibrosis in renal allograft and improve the outcome.

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.

Simultaneous activation of innate and adaptive immunity participates in the development of renal injury in a model of heavy proteinuria

Protein overload of proximal tubular cells (PTCs) can promote interstitial injury by unclear mechanisms that may involve activation of innate immunity. We investigated whether prolonged exposure of tubular cells to high protein concentrations stimulates innate immunity, triggering progressive interstitial inflammation and renal injury, and whether specific inhibition of innate or adaptive immunity would provide renoprotection in an established model of massive proteinuria, adriamycin nephropathy (ADR). Adult male Munich-Wistar rats received a single dose of ADR (5 mg/kg, iv), being followed for 2, 4, or 20 weeks. Massive albuminuria was associated with early activation of both the NF-κB and NLRP3 innate immunity pathways, whose intensity correlated strongly with the density of lymphocyte infiltration. In addition, ADR rats exhibited clear signs of renal oxidative stress. Twenty weeks after ADR administration, marked interstitial fibrosis, glomerulosclerosis, and renal functional loss were observed. Administration of mycophenolate mofetil (MMF), 10 mg/kg/day, prevented activation of both innate and adaptive immunity, as well as renal oxidative stress and renal fibrosis. Moreover, MMF treatment was associated with shifting of M from the M1 to the M2 phenotype. In cultivated NRK52-E cells, excess albumin increased the protein content of Toll-like receptor (TLR) 4 (TLR4), NLRP3, MCP-1, IL6, IL-1β, Caspase-1, α-actin, and collagen-1. Silencing of TLR4 and/or NLRP3 mRNA abrogated this proinflammatory/profibrotic behavior. Simultaneous activation of innate and adaptive immunity may be key to the development of renal injury in heavy proteinuric disease. Inhibition of specific components of innate and/or adaptive immunity may be the basis for future strategies to prevent chronic kidney disease (CKD) in this setting.

Urinary transcriptomics reveals patterns associated with subclinical injury of the renal allograft

AIM

Subclinical pathological features in renal allograft biopsies predict poor outcomes, and noninvasive biomarkers are wanted. RNA quantification in urine predicts overt rejection. We hypothesized that a whole transcriptome analysis would be informative, even for discrete injury.

PATIENTS & METHODS

We performed an mRNA microarray with an optimized normalization method on 26 urinary cell pellets to study renal partial epithelial to mesenchymal transition (pEMT) in stable kidney allografts.

RESULTS & CONCLUSION

Unbiased pathway analysis revealed immune response as the main underlying biological process. In a subgroup of pristine biopsies, isolated pEMT was associated with reduced metabolic functions. Thus, pEMT translates into specific urinary mRNA patterns, in other words, increased inflammation and decreased metabolic functions. Deposited in Gene Expression Omnibus (GSE89652).

Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice

Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-β to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of β-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in β-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering β-catenin localization and downstream signaling.

Urinary mRNA analysis of biomarkers to epithelial mesenchymal transition of renal allograft

Renal allograft loss is most often a chronic process, irrespective of the mechanism at stake. In this prospective study, we studied the expression of epithelial to mesenchymal transition (EMT) markers vimentin and β-catenin by immunohistochemistry in the surveillance biopsy and measured the mRNA encoding vimentin (VIM), CD45, GAPDH and uroplakin 1a (UPK) by quantitative PCR in urinary cells in 75 renal transplant patients. The aim is to establish a simple screening test for chronic renal allograft dysfunction. We found that the value of the mRNA of vimentin and CD45 relative to the uroplakin 1a (UPK) mRNA is correlated with the score in vimentin immunostaining in routine biopsies. These biomarkers could be used as a noninvasive tool to monitor the renal graft fibrogenesis. This test could be used for early detection of fibrotic diseases of the kidney transplant.

S100A4 amplifies TGF-β-induced epithelial-mesenchymal transition in a pleural mesothelial cell line

Pleural fibrosis can dramatically lower the quality of life. Numerous studies have reported that epithelial–mesenchymal transition (EMT) regulated by transforming growth factor-β (TGF-β) is involved in fibrosis. However, the molecular mechanism is inadequately understood. Fibroblast-specific protein-1 (S100A4) is a target of TGF-β signaling. In our previous study, we have reported that S100A4 is highly expressed in pleural fibrosis. Thus, we suggest that S100A4 took part in the TGF-β-induced EMT in pleural fibrosis. In this study, we determined the expression of S100A4 and EMT-related markers in Met-5A cells (pleural mesothelial cells) treated with TGF-β or TGF-β inhibitor by real-time PCR and western blot. In order to explore the role of S100A4, we used siRNA to knock down the expression of S100A4 in cell model. We found that the expression of epithelial cell marker was decreased and the mesenchymal cell marker increased with S100A4 upregulation after treatment with TGF-β. Moreover, the changes of EMT-related event were restricted when the expression of S100A4 was knocked down. Conversely, S100A4 can partially rescue the EMT-related expression changes induced by TGF-β inhibitor. These findings suggest that S100A4 expression is induced by the TGF-β pathway, and silencing S100A4 expression can inhibit the process of TGF-β-induced EMT.

In vitro evidences of epithelial to mesenchymal transition in low cell-density cultured human fetal hepatocytes

Culturing fetal hepatocytes in high cell-density allowed stabilization of the hepatocyte phenotype up to 8 weeks, including the maintenance of liver-specific functions. On the other hand, when cultured at low cell-density, fetal hepatocytes underwent morphological modifications and acquired fibroblastic morphology. Since a switch from E-cadherin to vimentin expression accompanied these changes, we hypothesized the occurrence of epithelial-to-mesenchymal transition when fetal hepatocytes were cultured at low cell-density. Changes in gene expressionsuch as up-regulation of fibrosis-related geneswere also observed, suggesting that the low cell-density culture system promoted the acquisition of a profibrotic phenotype in cultured hepatocytes. The origin of fibrogenic cells in the liver is not well known, and the role of hepatocytes as a source of fibrogenic cells is controversial. Therefore, we hypothesized that hepatocytes undergoing epithelial-to-mesenchymal transition could have a central role in liver fibrosis as a source of fibrogenic cells. To conclude, the high cell-density culture system could be a useful model for in vitro studies requiring long-term cultures of hepatocytes, such as the development of pharmaceutical drugs and mechanisms of viral infections. The low cell-density culture system may provide additional insights into the origin of fibrogenic cells in the liver, thus contributing to the development of novel therapeutic approaches.

A choroid plexus cyst in the fourth ventricle of a Sprague-Dawley rat

Choroid plexus cysts are rare lesions in the brain and are reported in humans and dogs. Herein, we report a choroid plexus cyst found in a 10-week-old female Sprague-Dawley rat. Histologically, a cyst measuring approximately 600 μm in diameter was found in the fourth ventricle of the brain. The cyst was lined with a single layer of flattened cells and was present in the connective tissue of the choroid plexus. Next to the cyst, a dilated tube was found with a similar morphology to the epithelium of the choroid plexus. Immunohistochemistry revealed that flattened cells lining the cyst were positive for cytokeratin and vimentin, and negative for GFAP and S-100, which is the same as in the normal choroid plexus, excluding vimentin. We diagnosed the present cyst as a spontaneously occurring choroid plexus cyst that was considered to be undergoing the epithelial-mesenchymal transition.

The barrier hypothesis and Oncostatin M: Restoration of epithelial barrier function as a novel therapeutic strategy for the treatment of type 2 inflammatory disease

Mucosal epithelium maintains tissue homeostasis through many processes, including epithelial barrier function, which separates the environment from the tissue. The barrier hypothesis of type 2 inflammatory disease postulates that epithelial and epidermal barrier dysfunction, which cause inappropriate exposure to the environment, can result in allergic sensitization and development of type 2 inflammatory disease. The restoration of barrier dysfunction once it's lost, or the prevention of barrier dysfunction, have the potential to be exciting new therapeutic strategies for the treatment of type 2 inflammatory disease. Neutrophil-derived Oncostatin M has been shown to be a potent disrupter of epithelial barrier function through the induction of epithelial-mesenchymal transition (EMT). This review will discuss these events and outline several points along this axis at which therapeutic intervention could be beneficial for the treatment of type 2 inflammatory diseases.

Association Studies of Bone Morphogenetic Protein 2 Gene Polymorphisms With Acute Rejection in Kidney Transplantation Recipients

OBJECTIVE

Bone morphogenetic proteins (BMP) belong to the transforming growth factor beta superfamily of proteins. This study was performed to evaluate the association of BMP gene polymorphisms with acute renal allograft rejection (AR) and graft dysfunction (GD) in Koreans.

METHODS

Three hundred thirty-one patients who had kidney transplantation procedures were recruited. Transplantation outcomes were determined in terms of AR and GD criteria. We selected six single nucleotide polymorphisms (SNPs): rs1979855 (5' near gene), rs1049007 (Ser87Ser), rs235767 (intron), rs1005464 (intron), rs235768 (Arg190Ser), and rs3178250 (3; untranslated region).

RESULTS

Among the six SNPs tested, the rs235767, rs1005464, and rs3178250 SNPs were significantly associated with AR (P < .05). The rs1049007 and rs235768 SNPs also showed an association with GD (P < .05).

CONCLUSIONS

In conclusion, these results suggest that the BMP2 gene polymorphism may be related to the development of AR and GD in kidney transplant recipients.

miR-204 regulates epithelial-mesenchymal transition by targeting SP1 in the tubular epithelial cells after acute kidney injury induced by ischemia-reperfusion

Acute kidney injury (AKI) is a disease where kidney function is lost almost instantaneously; it can develop very rapidly over few hours to maximum of few days. Despite the advent of technology, the clinical management against this disease is very poor, and most of the time it is life-threatening. AKI has been actively regulated by extracellular matrix proteins (ECM), however, its underlying mechanism of regulation during AKI progression is very poorly understood. In this study, we explored the integrated network of mRNA and microRNAs (miRNAs) that maintains the progression of ECM after induction of AKI by lethal ischemia. To identify key regulators of ECM, we screened large number of transcriptomes using laser capture microdissection (LCM) technique in addition to microarray and RT-qPCR. Our result clearly showed that 9 miRNAs including miR-21, miR-483, miR-5115, miR-204e, miR-128, miR-181c, miR-203, miR-204 and miR-204c were highly regulated, out of which miR-204 expression change (decrease) was most drastic during ischemia/reperfusion. Detail mechanistic study utilizing combined experimental and computational approach revealed that TGF-β signaling pathway was potentially modulated by deregulated miRNA-204 through SP1, where the TGF-β signaling pathway plays a vital role in ECM regulation. Apart from targeting SP1 and antagonizing epithelial-mesenchymal transition (EMT) signaling our result also showed that miR-204 protects interstitial tissue of renal tubules from chronic fibrotic change. Altogether our study provides sufficient details of how miRNA mediated ECM regulation occur during AKI, which can be effectively utilized in future for better AKI management and diagnosis.

Use of Contrast-Enhanced Ultrasonography to Evaluate Chronic Allograft Nephropathy in Rats and Correlations between Time-Intensity Curve Parameters and Allograft Fibrosis

This study quantitatively analyzed changes in the hemodynamic characteristics of renal allografts at different stages in a rat chronic allograft nephropathy (CAN) model as well as the relationship between hemodynamic parameters and renal allograft fibrosis using contrast-enhanced ultrasonography (CEUS). The experimental group used a CAN rat model (n = 30), and the control group used an orthotopic syngeneic renal transplant model (n = 30). After surgery, creatinine clearance rates were regularly monitored every 2 wk. The checking times were set at 4, 12 and 24 wk after surgery, which represent early, middle and late stage of CAN, respectively. At different stages of CAN, eight rats from each group were randomly selected for CEUS examination. Time-intensity curve (TIC) parameters, including rise time, peak intensity, mean transit time, area under the curve, wash-in slope, time-to-peak and α-smooth muscle actin (α-SMA) expression; Vimentin expression; and chronic allograft damage index scores were evaluated by linear correlation analysis. Before the creatinine clearance rate showed significant abnormalities, the renal allografts in the experimental group had already presented pathologic changes associated with CAN. In the early stage after surgery, compared to the TIC curve of the control group, the experimental group showed increased rise time, mean transit time, area under the curve and time-to-peak, and decreased wash-in slope (p < 0.05). Chronic allograft damage index scores and the expression levels of α-SMA and Vimentin proteins in renal allografts were correlated with TIC parameters (p < 0.05). Compared to creatinine clearance rate, CEUS can detect CAN at earlier stages. The correlations between TIC-related parameters and the expression levels of α-SMA and Vimentin in renal allografts indicate that CEUS is a feasible way to assess the degree of renal allograft fibrosis quantitatively.

Keratins are novel markers of renal epithelial cell injury

Keratins, the intermediate filaments of the epithelial cell cytoskeleton, are up-regulated and post-translationally modified in stress situations. Renal tubular epithelial cell stress is a common finding in progressive kidney diseases, but little is known about keratin expression and phosphorylation. Here, we comprehensively describe keratin expression in healthy and diseased kidneys. In healthy mice, the major renal keratins, K7, K8, K18, and K19, were expressed in the collecting ducts and K8, K18 in the glomerular parietal epithelial cells. Tubular expression of all 4 keratins increased by 20- to 40-fold in 5 different models of renal tubular injury as assessed by immunohistochemistry, Western blot, and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). The up-regulation became significant early after disease induction, increased with disease progression, was found de novo in distal tubules and was accompanied by altered subcellular localization. Phosphorylation of K8 and K18 increased under stress. In humans, injured tubules also exhibited increased keratin expression. Urinary K18 was only detected in mice and patients with tubular cell injury. Keratins labeled glomerular parietal epithelial cells forming crescents in patients and animals. Thus, all 4 major renal keratins are significantly, early, and progressively up-regulated upon tubular injury regardless of the underlying disease and may be novel sensitive markers of renal tubular cell stress.

Epithelial-mesenchymal transition: An emerging target in tissue fibrosis

Epithelial-mesenchymal transition (EMT) is involved in a variety of tissue fibroses. Fibroblasts/myofibroblasts derived from epithelial cells contribute to the excessive accumulation of fibrous connective tissue in damaged tissue, which can lead to permanent scarring or organ malfunction. Therefore, EMT-related fibrosis cannot be neglected. This review highlights the findings that demonstrate the EMT to be a direct contributor to the fibroblast/myofibroblast population in the development of tissue fibrosis and helps to elucidate EMT-related anti-fibrotic strategies, which may enable the development of therapeutic interventions to suppress EMT and potentially reverse organ fibrosis.

Shear Stress-Induced Alteration of Epithelial Organization in Human Renal Tubular Cells

Tubular epithelial cells in the kidney are continuously exposed to urinary fluid shear stress (FSS) generated by urine movement and recent in vitro studies suggest that changes of FSS could contribute to kidney injury. However it is unclear whether FSS alters the epithelial characteristics of the renal tubule. Here, we evaluated in vitro and in vivo the influence of FSS on epithelial characteristics of renal proximal tubular cells taking the organization of junctional complexes and the presence of the primary cilium as markers of epithelial phenotype. Human tubular cells (HK-2) were subjected to FSS (0.5 Pa) for 48h. Control cells were maintained under static conditions. Markers of tight junctions (Claudin-2, ZO-1), Par polarity complex (Pard6), adherens junctions (E-Cadherin, β-Catenin) and the primary cilium (α-acetylated Tubulin) were analysed by quantitative PCR, Western blot or immunocytochemistry. In response to FSS, Claudin-2 disappeared and ZO-1 displayed punctuated and discontinuous staining in the plasma membrane. Expression of Pard6 was also decreased. Moreover, E-Cadherin abundance was decreased, while its major repressors Snail1 and Snail2 were overexpressed, and β-Catenin staining was disrupted along the cell periphery. Finally, FSS subjected-cells exhibited disappeared primary cilium. Results were confirmed in vivo in a uninephrectomy (8 months) mouse model where increased FSS induced by adaptive hyperfiltration in remnant kidney was accompanied by both decreased epithelial gene expression including ZO-1, E-cadherin and β-Catenin and disappearance of tubular cilia. In conclusion, these results show that proximal tubular cells lose an important number of their epithelial characteristics after long term exposure to FSS both in vitro and in vivo. Thus, the changes in urinary FSS associated with nephropathies should be considered as potential insults for tubular cells leading to disorganization of the tubular epithelium.

[The epithelial-mesenchymal transition and fibrosis of the renal transplant]

Epithelial-mesenchymal transition (EMT) is a process by which differentiated epithelial cells undergo a phenotypic conversion and acquire a mesenchymal phenotype, including elongated morphology, enhanced migratory and invasion capacity, and greatly increased production of extracellular matrix (ECM) components. This phenomenon plays a pivotal role in embryonic development, wound healing and tissue regeneration. It has also been involved in organ fibrosis. Some studies suggest that following injury, renal tubular epithelial cells undergo reprograming in mesenchymal cells, and thus constitute an important source of de novo myofibroblasts invading the renal interstitium and contributing to fibrosis. However, an increasing number of studies raise doubts about the existence of this process in vivo. The role of EMT in the development of renal fibrosis remains a matter of intense debate and may depend on the model studied. In this review, we describe the role of EMT in the development of fibrosis of renal graft, and then we propose approaches for detecting and treating renal fibrogenesis by targeting TEM.

Cardiac allograft vasculopathy: a donor or recipient induced pathology?

Cardiac allograft vasculopathy (CAV) is one of the main causes of late-stage heart failure after heart transplantation. CAV is characterized by concentric luminal narrowing of the coronary arteries, but the exact pathogenesis of CAV is still not unraveled. Many researchers show evidence of an allogeneic immune response of the recipient, whereas others show contrasting results in which donor-derived cells induce an immune response against the graft. In addition, fibrosis of the neo-intima can be induced by recipient-derived circulating cells or donor-derived cells. In this review, both donor and recipient sides of the story are described to obtain better insight in the pathogenesis of CAV. Dual outcomes were found regarding the contribution of donor and recipient cells in the initiation of the immune response and the development of fibrosis during CAV. Future research could focus more on the potential synergistic interaction of donor and recipient cells leading to CAV.

Diverse origins of the myofibroblast—implications for kidney fibrosis

Fibrosis is the common end point of chronic kidney disease. The persistent production of inflammatory cytokines and growth factors leads to an ongoing process of extracellular matrix production that eventually disrupts the normal functioning of the organ. During fibrosis, the myofibroblast is commonly regarded as the predominant effector cell. Accumulating evidence has demonstrated a diverse origin of myofibroblasts in kidney fibrosis. Proposed major contributors of myofibroblasts include bone marrow-derived fibroblasts, tubular epithelial cells, endothelial cells, pericytes and interstitial fibroblasts; the published data, however, have not yet clearly defined the relative contribution of these different cellular sources. Myofibroblasts have been reported to originate from various sources, irrespective of the nature of the initial damage responsible for the induction of kidney fibrosis. Here, we review the possible relevance of the diversity of myofibroblast progenitors in kidney fibrosis and the implications for the development of novel therapeutic approaches. Specifically, we discuss the current status of preclinical and clinical antifibrotic therapy and describe targeting strategies that might help support resident and circulating cells to maintain or regain their original functional differentiation state. Such strategies might help these cells resist their transition to a myofibroblast phenotype to prevent, or even reverse, the fibrotic state.

Donor ABCB1 genetic polymorphisms influence epithelial-to-mesenchyme transition in tacrolimus-treated kidney recipients

Aim: The contribution of epithelial–mesenchymal transition (EMT) has been suggested in renal transplant recipients receiving calcineurin inhibitors and developing nephrotoxicity. Materials & methods: We assessed whether interindividual variability in tacrolimus pharmacokinetics is associated with the occurrence in tubular cells of two EMT markers (vimentin, β-catenin) detected at 3‐month in 140 allograft biopsies. We investigated whether genetic polymorphisms affecting CYP3A5 and ABCB1 influence EMT and kidney fibrosis. Results: In univariate analysis, the donor CYP3A5*1 allele was significantly associated with a lower vimentin expression. In multivariate analysis, grafts carrying ABCB1 3435T allele(s) developed significantly less EMT and less interstitial fibrosis. Conclusion: Donor SNPs significantly influence the epithelial program in the context of kidney transplantation, and the epithelial metabolism of tacrolimus is one key to understand graft fibrogenesis.

The role of macrophages in the development of human renal allograft fibrosis in the first year after transplantation

The aim of this study was to investigate the role of infiltrating macrophages in renal allograft fibrosis. Forty-six protocol renal allograft biopsies obtained 1 year after transplantation were stained with Sirius red to quantify fibrosis and double stained with CD68 and CD206 to identify the proportion of alternatively activated (M2) macrophages. Biopsies were analyzed for gene expression by microarray, which was correlated with macrophage infiltration and the severity of fibrosis. The number of infiltrating CD68+ cells strongly correlated with the percentage of interstitial fibrosis (r = 0.73, p < 0.0001). Macrophage infiltration at 1 year correlated with renal dysfunction at 1, 12 and 36 months posttransplant (estimated GFR low vs. high: 1 month 78 ± 26 vs. 54 ± 19 mL/min, p < 0.01; 12 months 87 ± 29 vs. 64 ± 19 mL/min, p < 0.05; 36 months 88 ± 33 vs. 60 ± 24 mL/min, p < 0.05). Ninety-two percent of infiltrating macrophages exhibited an M2 phenotype with CD68+ CD206+ dual staining. Gene microarrays demonstrated an alloimmune response with up-regulation of interferon-γ-response genes despite the lack of rejection or inflammatory infiltrate. Consistent with this was the presence of CXCL10 in proximal tubular cells at 3 months. This suggests that M2 macrophage proliferation, or infiltration, was associated with subclinical alloimmune inflammation, tubular injury and progression of fibrosis.

MicroRNA-328 inhibits renal tubular cell epithelial-to-mesenchymal transition by targeting the CD44 in pressure-induced renal fibrosis

Epithelial-mesenchymal transition (EMT) occurs in stressed tubular epithelial cells, contributing to renal fibrosis. Initial mechanisms promoting EMT are unknown. Pressure force is an important mechanism contributing to the induction and progression of renal fibrogenesis in ureteric obstruction. In our study of cultured rat renal tubular cells (NRK-52E) under 60 mmHg of pressure, we found that the epithelial marker E-cadherin decreased and mesenchymal markers, e.g., α-smooth muscle actin, fibronectin and Snail, increased. Pressure also induced the expression of connective tissue growth factor and transforming growth factor-β. MicroRNA array assays showed that pressure reduced miR-328 at the initial stage of pressurization. We identified a potential target sequence of miR-328 in rat CD44 3′-untranslated regions. In contrast with the miR-328 expression, CD44 expression was up-regulated at the initial pressurization stage. We also found that miR-328 expression decreased and CD44 increased in ureteric obstruction kidneys in the animal study. CD44 siRNA transfection significantly increased E-cadherin expression and inhibited pressure-induced EMT. Both hyaluronan binding peptide pep-1 and osteopontin neutralizing antibody inhibited pressure-induced EMT. Our results suggest that miR-328-mediated CD44 transient upregulation is an important trigger of the pressure-induced EMT in renal fibrosis.

Histopathology and biomarkers in prediction of renal function in children after kidney transplantation

BACKGROUND

Early detection of chronic allograft injury is a major challenge after kidney transplantation (RTx) in adults and children. We correlated the expression of four immunohistochemical biomarkers, P-selectin glycoprotein ligand-1 (PSGL-1), vimentin, α-smooth muscle actin (α-SMA) and collagen IV, to the kidney graft histology and function in pediatric RTx patients.

METHODS

We analyzed the histopathology and immunohistochemical stainings of 165 biopsies from 56 patients. Histopathology was scored according to Banff '05 classification and biomarker expression semiquantitatively. Glomerular filtration rate (GFR) was measured annually by (51)Cr-EDTA clearance.

RESULTS

In protocol biopsies, the expression of all four biomarkers correlated with the interstitial fibrosis and tubular atrophy (IF/TA) changes, which increased during the first 36months after RTx. At the time of 18month biopsy, we observed the deterioration of GFR in patients with high (≥2) IF/TA score (50 vs. 68ml/min/1.73m(2), p=0.004) or collagen IV expression (45 vs. 65ml/min/1.73m(2), p=0.016). Intense stainings of IF/TA, collagen IV and vimentin are also associated with poor GFR at 36 and 48months, however, the biomarker scores revealed no additional predictive value for concomitant or late GFR compared to IF/TA score. Patients with high and low biomarker expressions showed no significant differences in annual deterioration of GFR, which declined on average 2.2ml/min/1.73m(2)/year over the 7years follow-up.

CONCLUSIONS

Overall, the results suggest that traditional histopathology is a sufficient predictor for graft function, and the routine use of these histochemical markers as surrogates for graft function deterioration is questioned.

Endothelin-1 mediated high glucose-induced epithelial-mesenchymal transition in renal tubular cells

OBJECTIVE

The pathogenesis of interstitial fibrosis in diabetic nephropathy (DN) is an intractable problem without good therapy. Emerging evidence suggests that epithelial-mesenchymal transition (EMT) is an important mechanism for tubular epithelial cells undergoing profibrotic change in DN. Endothelin-1 (ET-1) is an important cytokine which can cause fibrogenesis and is reportedly involved in DN. However, the role of ET-1 in EMT in DN is unknown. The present study was designed to investigate the role of ET-1 in high glucose-induced EMT and the signaling pathway mediating the effect of ET-1 in renal tubular cells.

METHOD

Tubular epithelial cells (NRK52E) were treated with normal glucose (d-glucose 5.6mmol/L, NG), high glucose (30mmol/L, HG), high osmotic (d-glucose 5.6mmol/L+d-mannitol 24.4mmol/L), HG+ETA antagonist BQ123 (2μg/ml), ET-1, ET-1+ hypoxia inducible factor (HIF)-1α siRNA, CoCl2 (100μmol/L), CoCl2+HIF-1α siRNA or CoCl2+BQ123. The supernatant level of ET-1 was measured by ELISA and the expression of vimentin, E-cadherin and HIF-1α was detected by RT-PCR and western blot.

RESULT

The ET-1 level increased markedly in the supernatant of NRK52E incubated with HG. In NRK52E induced with HG or ET-1, the expression of vimentin was upregulated, whereas the expression of E-cadherin was downregulated. BQ123 attenuated HG- and CoCl2-induced EMT while HIF-1α siRNA did not affect ET-1 induced EMT.

CONCLUSIONS

High glucose induced ET-1 production that mediated the EMT induced by high glucose in renal tubular epithelial cells, and HIF-1α acted as the upstream signal to regulate ET-1.

Progression of pulse pressure in kidney recipients durably exposed to CsA is a risk factor for epithelial phenotypic changes: an ancillary study of the CONCEPT trial

In this ancillary study of the CONCEPT trial, we studied the role of CsA withdrawal at 3 months (3M) post-transplant on the intensity of epithelial phenotypic changes (EPC, an early marker for kidney fibrogenesis) on the 12 M surveillance biopsy. Although conversion from CsA to sirolimus (SRL) at 3M was reported to have improved mean graft function at 12 M, it did not reduce the score of EPC (1.73 ± 1.15 in the SRL group vs. 1.87 ± 1 in the CsA group, P = 0.61). Acute rejection, which had occurred twice more frequently in SRL-converted patients included here, was associated with 12 M EPC. Interestingly, we observed that the patients durably exposed to CsA and who developed 12 M EPC had a significant progression of blood pulse pressure (pp) from 1 to 6M post-transplantation (Δpp = +12.3 mmHg, P = 0.0035). Pulse pressure at 4, 6, and 9 M and pp progression from 1 to 6M were significantly associated with the development of EPC at 12 M in renal grafts. Logistic regression analysis revealed that a high 6M pp (≥ 60 mmHg) was an independent risk factor for 12 M EPC with an odds ratio of 2.25 per additional 10 mmHg pp (95%CI: 1.14-4.4, P = 0.02) after adjustment with recipient's and donor's age, acute rejection incidence and immunosuppressive regimen. A post hoc analysis of the data collected in the whole population CONCEPT study revealed that pp was significantly higher at 6 months in patients maintained on CsA and that at this time point pp correlated negatively with GFR at 1 year.

A novel model of surgical injury in adult rat kidney: a "pouch model"

Regenerative mechanisms after surgical injury have been studied in many organs but not in the kidney. Studying surgical injury may provide new insights into mechanisms of kidney regeneration. In rodent models, extrarenal tissues adhere to surgical kidney wound and interfere with healing. We hypothesized that this can be prevented by wrapping injured kidney in a plastic pouch. Adult rats tolerated 5/6 nephrectomy with pouch application well. Histological analysis demonstrates that application of the pouch effectively prevented formation of adhesions and induced characteristic wound healing manifested by formation of granulation tissue. Additionally, selected tubules of the wounded kidney extended into the granulation tissue forming branching tubular epithelial outgrowths (TEOs) without terminal differentiation. Tubular regeneration outside of renal parenchyma was not previously observed, and suggests previously unrecognized capacity for regeneration. Our model provides a novel approach to study kidney wound healing.

Pulmonary vein stenosis and the pathophysiology of "upstream" pulmonary veins

BACKGROUND

Surgical and catheter-based interventions on pulmonary veins are associated with pulmonary vein stenosis (PVS), which can progress diffusely through the "upstream" pulmonary veins. The mechanism has been rarely studied. We used a porcine model of PVS to assess disease progression with emphasis on the potential role of endothelial-mesenchymal transition (EndMT).

METHODS

Neonatal piglets underwent bilateral pulmonary vein banding (banded, n = 6) or sham operations (sham, n = 6). Additional piglets underwent identical banding and stent implantation in a single-banded pulmonary vein 3 weeks postbanding (stented, n = 6). At 7 weeks postbanding, hemodynamics and upstream PV pathology were assessed.

RESULTS

Banded piglets developed pulmonary hypertension. The upstream pulmonary veins exhibited intimal thickening associated with features of EndMT, including increased transforming growth factor (TGF)-β1 and Smad expression, loss of endothelial and gain of mesenchymal marker expression, and coexpression of endothelial and mesenchymal markers in banded pulmonary vein intimal cells. These immunopathologic changes and a prominent myofibroblast phenotype in the remodeled pulmonary veins were consistently identified in specimens from patients with PVS, in vitro TGF-β1-stimulated cells isolated from piglet and human pulmonary veins, and human umbilical vein endothelial cells. After stent implantation, decompression of a pulmonary vein was associated with reappearance of endothelial marker expression, suggesting the potential for plasticity in the observed pathologic changes, followed by rapid in-stent restenosis.

CONCLUSIONS

Neonatal pulmonary vein banding in piglets recapitulates critical aspects of clinical PVS and highlights a pathologic profile consistent with EndMT, supporting the rationale for evaluating therapeutic strategies designed to exploit reversibility of upstream pulmonary vein pathology.

Distribution and expression of fibroblast-specific protein chemokine CCL21 and chemokine receptor CCR7 in renal allografts

We aimed to characterize the expression and distribution of the fibroblast surface protein (FSP), the chemokine CC-ligand 21 (CCL21) secondary lymphoid tissue chemokine CC-chemokine receptor 7 (CCR7) in renal allograft biopsy specimens obtained from patients after transplantation. We recruited 165 patients who received renal transplants at our center for this study. Histological examination of the renal allograft biopsy specimens was performed using hematoxylin-eosin, periodic acid-Schiff, and Masson's trichrome staining. Distribution and expression of FSP, CCL21, and CCR7 were determined using immunohistochemistry staining. Serum creatinine levels were evaluated using an enzymatic sarcosine oxidase method. FSP was mainly localized in the cytoplasm and nucleus of renal interstitial fibroblasts and tubular epithelial cells. Compared with the normal group, an elevated number of FSP-positive fibroblasts were observed in patients with acute/active cellular rejection and chronic/sclerosing allograft nephropathy (P < .05). Patients with chronic/sclerosing allograft nephropathy also showed increased total fibroblasts as compared with borderline changes (P < .05). In a multiple regression analysis, CCR7-positive expression was a strong protective factor for acute/active cellular rejection and recurrent nephropathy (odds ratio [OR] = 0.12, P = .034, and OR = 0.08; P = .036, respectively). In contrast, CCL21-positive expression led to a high susceptibility to recurrent nephropathy among renal transplant patients (OR = 10.41, P = .029). Moreover, FSP and CCL21, or CCL21 and CCR7 were localized in the interstitial fibroblasts and renal tubular epithelium cells. In addition, FSP and CCL21 expression positively correlated with serum creatinine levels. Our results suggested that the CCL21/CCR7 signaling pathway is involved in renal fibrosis in kidney transplant patients. An increased number of FSP-positive fibroblasts may be a risk factor for acute/active cellular rejection and chronic/sclerosing allograft nephropathy after renal transplantation. These findings may help understanding of renal allograft fibrosis.

Reduction of osteopontin in vivo inhibits tubular epithelial to mesenchymal transition in rats with chronic allograft nephropathy

OBJECTIVE

Chronic allograft nephropathy (CAN) is an important etiological factor causing graft loss. However, the mechanism of CAN is unclear. Osteopontin (OPN), a proinflammatory and profibrosis molecule, plays a key role in late stages of renal diseases. We investigated the potential role of OPN in the pathogenesis of CAN.

METHODS

Using a F344 to Lewis rat CAN model, we injected short hairpin RNA (shRNA) constructs targeting OPN or negative control plasmids through the renal vein following electroporation. At 12 weeks after the transplantation, we determined interstitial fibrosis (IF) and tubular atrophy (TA) of the tubular epithelial cells (TECs). OPN expression was examined using Western blots and immunohistochemistry (IHC). Molecules involved in epithelial to mesenchymal transition (EMT) of TECs were examined using IHC and Western blots.

RESULTS

OPN expression in kidney grafts was decreased by the RNA interference (RNAi) group. Histology observations showed IF and TA to be mild with stable renal function in the RNAi-treated group. EMT of TECs was significantly lessened after reducing OPN.

CONCLUSION

Reduction of OPN in vivo inhibited progression of CAN. OPN may be of therapeutic value in transplantation settings.

Hypoxia Induces Mesenchymal Gene Expression in Renal Tubular Epithelial Cells: An in vitro Model of Kidney Transplant Fibrosis

BACKGROUND

The development of interstitial fibrosis and tubular atrophy is a common complication after kidney transplantation and is associated with reduced long-term outcome. The hallmark of tubulointerstitial fibrosis is an increase in extracellular matrix resulting from exaggerated activation of fibroblasts/myofibroblasts, and tubular atrophy is characterized by a decrease in tubular diameter and loss of function. Atrophic epithelial cells may undergo epithelial-to-mesenchymal transition (EMT) with potential differentiation into interstitial fibroblasts. One potential driver of EMT in developing interstitial fibrosis and tubular atrophy is chronic hypoxia.

METHODS

The expression of 46 EMT-related genes was analyzed in an in vitro hypoxia model in renal proximal tubular epithelial cells (RPTEC). Furthermore, the expression of 342 microRNAs (miR) was evaluated in hypoxic culture conditions.

RESULTS

Hypoxic RPTEC expressed markers of a more mesenchymal phenotype and showed an increased expression of matrix metalloproteinase-2 (MMP2). MMP2 expression in RPTEC correlated inversely with a decreased expression of miR-124, which was found to have a putative binding site for the MMP2 transcript. Overexpression of miR-124 inhibited MMP2 protein translation. Hypoxia was associated with increased migration/proliferation of RPTEC which was reversed by miR-124.

CONCLUSIONS

These results indicate that hypoxia promotes a mesenchymal and migratory phenotype in renal epithelial cells, which is associated with increased MMP2 expression. Hypoxia-dependent MMP2 expression is regulated via a reduced transcription of miR-124. Overexpression of miR-124 antagonizes hypoxia-induced cell migration. Further research is needed to elucidate the functional role of miR-124 and MMP2 in the development of fibrosis in renal transplant degeneration.

EMT-MET in renal disease: should we curb our enthusiasm?

Renal epithelial cells arise during embryogenesis by mesenchymal to epithelial transition (MET). In the context of renal diseases, these cells can switch back to a mesenchymal phenotype, in a process thus reminiscent of an epithelial-to-mesenchymal transition (EMT) in which we referred to as "Epithelial Phenotypic Changes" (EPC). The pathophysiological consequence of EPC is controversial: in particular, to what extent EPC contribute to the pool of disease-associated renal fibroblasts is very uncertain. However, there is strong evidence that EPC correlate with a poor renal outcome. EPC indeed reflect an exposure to a profibrotic environment, at an early and potentially reversible stage. Detecting EPC has potential therapeutic implications for patients prone to renal fibrosis, both as a marker of efficacy or more directly as a target. In opposition to the EMT occurring during embryogenesis, EMT in fibrosis as well as in cancer is an anarchic cellular process actually developing at the expense of the whole organ(ism).

Amygdalin inhibits renal fibrosis in chronic kidney disease

Renal interstitial fibrosis is a common outcome of chronic renal diseases. Amygdalin is one of a number of nitrilosides, the natural cyanide‑containing substances abundant in the seeds of plants of the prunasin family that are used to treat cancer and relieve pain. However, whether amygdalin inhibits the progression of renal fibrosis or not remains unknown. The present study aimed to assess the therapeutic potential of amygdalin by investigating its effect and potential mechanism on the activation of renal interstitial fibroblast cells and renal fibrosis in rat unilateral ureteral obstruction (UUO). Treatment of the cultured renal interstitial fibroblasts with amygdalin inhibited their proliferation and the production of transforming growth factor (TGF)‑β1. In the rat model of obstructive nephropathy, following ureteral obstruction, the administration of amygdalin immediately eliminated the extracellular matrix accumulation and alleviated the renal injury on the 21st day. Collectively, amygdalin attenuated kidney fibroblast (KFB) activation and rat renal interstitial fibrosis. These results indicate that amygdalin is a potent antifibrotic agent that may have therapeutic potential for patients with fibrotic kidney diseases.

Smad mediated regulation of inhibitor of DNA binding 2 and its role in phenotypic maintenance of human renal proximal tubule epithelial cells

The basic-Helix-Loop-Helix family (bHLH) of transcriptional factors plays a major role in regulating cellular proliferation, differentiation and phenotype maintenance. The downregulation of one of the members of bHLH family protein, inhibitor of DNA binding 2 (Id2) has been shown to induce de-differentiation of epithelial cells. Opposing regulators of epithelial/mesenchymal phenotype in renal proximal tubule epithelial cells (PTEC), TGFβ1 and BMP7 also have counter-regulatory effects in models of renal fibrosis. We investigated the regulation of Id2 by these growth factors in human PTECs and its implication in the expression of markers of epithelial versus myofibroblastic phenotype. Cellular Id2 levels were reduced by TGFβ1 treatment; this was prevented by co-incubation with BMP7. BMP7 alone increased cellular levels of Id2. TGFβ1 and BMP7 regulated Id2 through Smad2/3 and Smad1/5 dependent mechanisms respectively. TGFβ1 mediated Id2 suppression was essential for α-SMA induction in PTECs. Although Id2 over-expression prevented α-SMA induction, it did not prevent E-cadherin loss under the influence of TGFβ1. This suggests that the loss of gate keeper function of E-cadherin alone may not necessarily result in complete EMT and further transcriptional re-programming is essential to attain mesenchymal phenotype. Although BMP7 abolished TGFβ1 mediated α-SMA expression by restoring Id2 levels, the loss of Id2 was not sufficient to induce α-SMA expression even in the context of reduced E-cadherin expression. Hence, a reduction in Id2 is critical for TGFβ1-induced α-SMA expression in this model of human PTECs but is not sufficient in it self to induce α-SMA even in the context of reduced E-cadherin.

Expression of hypoxia-inducible factor-1α (HIF-1α) in infiltrating inflammatory cells is associated with chronic allograft dysfunction and predicts long-term graft survival

BACKGROUND

In chronic kidney failure, a hypoxic state, infiltrating inflammatory cells play a crucial role in the progression to end-stage renal disease. No studies have evaluated the influence of hypoxia and infiltrating inflammatory cells on chronic allograft dysfunction.

METHODS

Renal transplant recipients who underwent renal allograft biopsy with interstitial fibrosis/tubular atrophy (IF/TA) were enrolled and renal allograft tissue sections were processed for immunohistochemical staining including hypoxia-inducible factor-1α (HIF-1α), nitrotyrosine, α-smooth muscle actin and e-cadherin. Patients with total renal tissue HIF score ≥1 were defined as positive for HIF-1α. To assess the phenotype of the infiltrating cells, dual staining of HIF-1α with CD45, CD68 and CD3 was performed. The correlation between HIF-1α score and Banff's score was analysed. Clinical parameters including renal survival among patients with or without an expression of HIF-1α were compared.

RESULTS

Out of 55 patients enrolled, 23 patients (41.8%) had an HIF-1α score ≥1 (Group B). Compared with Group A (total renal HIF score <1), Group B had a significantly higher Banff score of interstitial infiltrates (i) (P = 0.029), vascular fibrous intimal thickening (cv) (P = 0.007) and arteriolar hyaline thickening (ah) (P = 0.026). Clinically, patients with an HIF-1α score were associated with a poor graft survival. Significantly inferior allograft survival was noted in Group B. HIF scores had an adjusted hazard ratio of 3.25 (95% confidence inteval: 1.71-6.16, P = 0.0003) in allograft failure.

CONCLUSIONS

We first demonstrated the expression of HIF-1α protein among infiltrating inflammatory cells in areas with IF/TA in patients with chronic allograft dysfunction.

Epithelial-mesenchymal crosstalk alteration in kidney fibrosis

The incidence of chronic kidney diseases (CKD) is constantly rising, reaching epidemic proportions in the western world and leading to an enormous threat, even to modern health-care systems, in industrialized countries. Therapies of CKD have greatly improved following the introduction of drugs targeting the renin-angiotensin system (RAAS) but even this refined pharmacological approach has failed to stop progression to end-stage renal disease (ESRD) in many individuals. In vitro historical data and recent new findings have suggested that progression of renal fibrosis might occur as a result of an altered tubulo-interstitial microenvironment and, more specifically, as a result of an altered epithelial-mesenchymal crosstalk. Here we the review biological findings that support the hypothesis of an altered cellular crosstalk in an injured local tubulo-interstitial microenvironment leading to renal disease progression. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.