Pathogenesis of tubulointerstitial fibrosis in chronic allograft dysfunction

Cyclophilin A/CD147 signaling induces the epithelial-to-mesenchymal transition and renal fibrosis in chronic allograft dysfunction by regulating p38 MAPK signaling

Objective

Our study was designed to explore the role of Cyclophilin A (CyPA)/CD147 signaling in renal allograft fibrosis and chronic allograft dysfunction (CAD).

Materials and methods

A rat renal transplant model with significant CAD was successfully achieved. Renal allograft tissues and blood samples were collected. Hematoxylin and eosin, Masson’s, and immunohistochemistry staining were performed. Since CD147 is mainly expressed in the renal tubular epithelial cells, human HK-2 cells were used and intervened by specific concentrations of CyPA, and the total protein and mRNA were extracted. Western blot assay and polymerase chain reaction were performed to explore the protein and mRNA expression of CyPA, CD147, and epithelial-to-mesenchymal transition (EMT)-related biomarkers. SiRNA-CD147 and specific inhibitors of p38 MAPK were used to explore the cellular mechanisms involved in the process.

Results

We have successfully established and validated a 20-week renal transplant CAD model. We observed significant distributed and expressed CyPA and CD147 in the renal allograft fibrotic tissues. We also found a significant expression of CD147 and EMT-related markers in the HK-2 cells stimulated by CyPA. The CD147 siRNA confirmed the previous in vitro results. The selective inhibition of MAPK suggested the notable role of p38 MAPK signaling pathway in the CyP/CD147 signaling involved in renal allograft fibrosis.

Conclusions

Our study reported the positive relationship of CyPA-CD147 signaling with renal allograft dysfunction. The in vitro study suggested that CyPA-CD147 signaling induce the development of the EMT process by p38 MAPK signaling, thus contributing to renal allograft fibrosis and CAD.

Urinary Cell mRNA Profiles Predictive of Human Kidney Allograft Status

Immune monitoring of kidney allograft recipients and personalized therapeutics may help reach the aspirational goal of "one transplant for life." The invasive kidney biopsy procedure, the diagnostic tool of choice, has become safer and the biopsy classification more refined. Nevertheless, biopsy-associated complications, interobserver variability in biopsy specimen scoring, and costs continue to be significant concerns. The dynamics of the immune repertoire make frequent assessments of allograft status necessary, but repeat biopsies of the kidney are neither practical nor safe. To address the existing challenges, we developed urinary cell mRNA profiling and investigated the diagnostic, prognostic, and predictive accuracy of absolute levels of a hypothesis-based panel of mRNAs encoding immunoregulatory proteins. Enabled by our refinements of the PCR assay and by investigating mechanistic hypotheses, our single-center studies identified urinary cell mRNAs associated with T cell-mediated rejection, antibody-mediated rejection, interstitial fibrosis and tubular atrophy, and BK virus nephropathy. In the multicenter National Institutes of Health Clinical Trials in Organ Transplantation-04, we discovered and validated a urinary cell three-gene signature of T-cell CD3 ε chain mRNA, interferon gamma inducible protein 10 (IP-10) mRNA, and 18s ribosomal RNA that is diagnostic of subclinical acute cellular rejection and acute cellular rejection and prognostic of acute cellular rejection and graft function. The trajectory of the signature score remained flat and below the diagnostic threshold for acute cellular rejection in the patients with no rejection biopsy specimens, whereas a sharp rise was observed during the weeks before the biopsy specimen that showed acute cellular rejection. Our RNA sequencing and bioinformatics identified kidney allograft biopsy specimen gene signatures of acute rejection to be enriched in urinary cells matched to acute rejection biopsy specimens. The urinary cellular landscape was more diverse and more enriched for immune cell types compared with kidney allograft biopsy specimens. Urinary cell mRNA profile-guided clinical trials are needed to evaluate their value compared with current standard of care.

Bioenergetic maladaptation and release of HMGB1 in calcineurin inhibitor-mediated nephrotoxicity

Calcineurin inhibitors (CNIs) are potent immunosuppressive agents, universally used following solid organ transplantation to prevent rejection. Although effective, the long-term use of CNIs is associated with nephrotoxicity. The etiology of this adverse effect is complex, and effective therapeutic interventions remain to be determined. Using a combination of in vitro techniques and a mouse model of CNI-mediated nephrotoxicity, we found that the CNIs, cyclosporine A (CsA), and tacrolimus (TAC) share a similar mechanism of tubular epithelial kidney cell injury, including mitochondrial dysfunction and release of High-Mobility Group Box I (HMGB1). CNIs promote bioenergetic reprogramming due to mitochondrial dysfunction and a shift toward glycolytic metabolism. These events were accompanied by diminished cell-to-cell adhesion, loss of the epithelial cell phenotype, and release of HMGB1. Notably, Erk1/2 inhibitors effectively diminished HMGB1 release, and similar inhibitor was observed on inclusion of pan-caspase inhibitor zVAD-FMK. In vivo, while CNIs activate tissue proremodeling signaling pathways, MAPK/Erk1/2 inhibitor prevented nephrotoxicity, including diminished HMGB1 release from kidney epithelial cells and accumulation in urine. In summary, HMGB1 is an early indicator and marker of progressive nephrotoxicity induced by CNIs. We suggest that proremodeling signaling pathway and loss of mitochondrial redox/bioenergetics homeostasis are crucial therapeutic targets to ameliorate CNI-mediated nephrotoxicity.

Cholangiocyte Epithelial to Mesenchymal Transition (EMT) is a potential molecular mechanism driving ischemic cholangiopathy in liver transplantation

Donation after circulatory death (DCD) has expanded the donor pool for liver transplantation. However, ischemic cholangiopathy (IC) after DCD liver transplantation causes inferior outcomes. The molecular mechanisms of IC are currently unknown but may depend on ischemia-induced genetic reprograming of the biliary epithelium to mesenchymal-like cells. The main objective of this study was to determine if cholangiocytes undergo epithelial to mesenchymal transition (EMT) after exposure to DCD conditions and if this causally contributes to the phenotype of IC. Human cholangiocyte cultures were exposed to periods of warm and cold ischemia to mimic DCD liver donation. EMT was tested by assays of cell migration, cell morphology, and differential gene expression. Transplantation of syngeneic rat livers recovered under DCD conditions were evaluated for EMT changes by immunohistochemistry. Human cholangiocytes exposed to DCD conditions displayed migratory behavior and gene expression patterns consistent with EMT. E-cadherin and CK-7 expressions fell while N-cadherin, vimentin, TGFβ, and SNAIL rose, starting 24 hours and peaking 1-3 weeks after exposure. Cholangiocyte morphology changed from cuboidal (epithelial) before to spindle shaped (mesenchymal) a week after ischemia. These changes were blocked by pretreating cells with the Transforming Growth Factor beta (TGFβ) receptor antagonist Galunisertib (1 μM). Finally, rats with liver isografts cold stored for 20 hours in UW solution and exposed to warm ischemia (30 minutes) at recovery had elevated plasma bilirubin 1 week after transplantation and the liver tissue showed immunohistochemical evidence of early cholangiocyte EMT. Our findings show EMT occurs after exposure of human cholangiocytes to DCD conditions, which may be initiated by upstream signaling from autocrine derived TGFβ to cause mesenchymal specific morphological and migratory changes.

Attenuating Effects of Dieckol on Hypertensive Nephropathy in Spontaneously Hypertensive Rats

Hypertension induces renal fibrosis or tubular interstitial fibrosis, which eventually results in end-stage renal disease. Epithelial-to-mesenchymal transition (EMT) is one of the underlying mechanisms of renal fibrosis. Though previous studies showed that Ecklonia cava extracts (ECE) and dieckol (DK) had inhibitory action on angiotensin (Ang) I-converting enzyme, which converts Ang I to Ang II. It is known that Ang II is involved in renal fibrosis; however, it was not evaluated whether ECE or DK attenuated hypertensive nephropathy by decreasing EMT. In this study, the effect of ECE and DK on decreasing Ang II and its down signal pathway of angiotensin type 1 receptor (AT1R)/TGFβ/SMAD, which is related with the EMT and restoring renal function in spontaneously hypertensive rats (SHRs), was investigated. Either ECE or DK significantly decreased the serum level of Ang II in the SHRs. Moreover, the renal expression of AT1R/TGFβ/SMAD was decreased by the administration of either ECE or DK. The mesenchymal cell markers in the kidney of SHRs was significantly decreased by ECE or DK. The fibrotic tissue of the kidney of SHRs was also significantly decreased by ECE or DK. The ratio of urine albumin/creatinine of SHRs was significantly decreased by ECE or DK. Overall, the results of this study indicate that ECE and DK decreased the serum levels of Ang II and expression of AT1R/TGFβ/SMAD, and then decreased the EMT and renal fibrosis in SHRs. Furthermore, the decrease in EMT and renal fibrosis could lead to the restoration of renal function. It seems that ECE or DK could be beneficial for decreasing hypertensive nephropathy by decreasing EMT and renal fibrosis.

Use of intravoxel incoherent motion imaging to monitor a rat kidney chronic allograft damage model

BACKGROUND

Chronic allograft damage (CAD) is the leading cause of long-term graft dysfunction. A noninvasive method that can diagnose CAD early and monitor its development is needed.

METHODS

Kidneys from Fisher rats were transplanted into Lewis rats to establish a CAD model (n = 20). The control group underwent syngeneic kidney transplantation (n = 20). The serum creatinine of the rats was monitored. At 4, 12, and 20 weeks after modeling, a magnetic resonance imaging (MRI) examination was performed. The apparent diffusion coefficient (ADC), pseudo diffusion coefficient (D*), true diffusion coefficient (D) and perfusion fraction (f) of the two groups were analyzed. Chronic allograft damage index (CADI) scoring was used to evaluate the transplanted kidney specimens. Immunohistochemistry was used to detect the expression of fibrosis markers in the transplanted kidney tissues and to analyze their correlations with all MRI parameters.

RESULTS

The transplanted kidneys in the experimental group developed CAD changes before the appearance of elevated creatinine. The MRI parameters in the experimental group [ADC (1.460 ± 0.109 VS 2.095 ± 0.319, P < 0.001), D (1.435 ± 0.102 VS 1.969 ± 0.305, P < 0.001), and f (26.532 ± 2.136 VS 32.255 ± 4.013, P < 0.001)] decreased, and D* (20.950 ± 2.273 VS 21.415 ± 1.598, P = 0.131) was not significantly different from those in the control group. ADC, D and f were negatively correlated with the CADI and the α-SMA and vimentin expression levels.

CONCLUSION

Intravoxel incoherent motion (IVIM) imaging could detect CAD earlier than creatinine and reflect the degree of fibrosis in grafts quantitatively.

Oxidative stress - chronic kidney disease - cardiovascular disease: A vicious circle

Chronic kidney disease patient's progression to end-stage renal disease as well as their high mortality are linked to cardiovascular disease. However, the high incidence rate of cardiovascular morbidity and mortality in these patients is not fully accounted for by traditional cardiovascular risk factors such as diabetes, hypertension and obesity. Renal disease and CVD are associated with endothelial dysfunction, inflammation and oxidative stress and in this review we will examine what is known regarding their similar roles in both CVD and chronic kidney disease, specifically focusing on the interconnections between oxidative stress, inflammation and endothelial dysfunction. These interconnections are best visualized as a vicious circle wherein these entities coexist and communicate with each other, thereby exacerbating the processes underpinning these different entities with the end result of the high morbidity and mortality that characterize CKD patients. By exploring this vicious circle i.e. the mode and extent of the interrelationships as well as some of the underlying mechanisms involved, this review aims at outlining our current understanding as well as highlighting future avenues for research and potential targets for therapeutic intervention.

Hypertensive nephropathy. Moving from classic to emerging pathogenetic mechanisms

Hypertensive kidney disease classically entails nephroangiosclerosis and hyalinosis with glomerular damage. However, in recent years, several evidences showed that high blood pressure also injures tubular cells, inducing epithelial-to-mesenchymal transition and tubulointerstitial fibrosis. Recently investigated mechanisms are also podocyte effacement and loss, which lead to denudation of the glomerular basement membrane and focal adhesion of the tufts to the Bowman's capsule, with reduced filtration and scars. Starting from the classic concept of nephroangiosclerosis, this review examines the recently emerged knowledge of new biochemical and molecular mechanisms underlying the kidney damage in hypertension and discusses how viable podocytes or podocyte-deriving proteins are promising tools for early diagnosis of renal remodelling in hypertension.

Application of Ultrasound Elastography for Chronic Allograft Dysfunction in Kidney Transplantation

Interstitial fibrosis is the main characteristic of chronic allograft dysfunction, which remains the key factor affecting long-term allograft survival after kidney transplantation. Ultrasound elastography (UE), including real-time elastography, transient elastography, and acoustic radiation force impulse, has been applied widely in breast, thyroid, and liver diseases, especially in the assessment of liver fibrosis. Recently, numerous studies have reported the efficacy of UE methods in evaluating renal allograft fibrosis. This review aims to investigate the clinical applications, limitations, and future roles of UE in current clinical practice in light of changing management paradigms. In current clinical practice, UE methods, especially transient elastographic measurement, appear to be useful for ruling out fibrosis but do not have sufficient accuracy to distinguish between various stages of allograft fibrosis. Moreover, there remain considerable issues to be solved for the application of UE in kidney transplantation. Thus, UE methods cannot replace the crucial role of renal allograft biopsy in the diagnosis and evaluation of allograft fibrosis in kidney transplantation. Perhaps UE methods could be of more importance in the long-term observation and evaluation of allograft fibrosis during follow-up.

Myofibroblast repair mechanisms post-inflammatory response: a fibrotic perspective

INTRODUCTION

Fibrosis is a complex chronic disease characterized by a persistent repair response. Its pathogenesis is poorly understood but it is typically the result of chronic inflammation and maintained with the required activity of transforming growth factor-β (TGFβ) and extracellular matrix (ECM) tension, both of which drive fibroblasts to transition into a myofibroblast phenotype.

FINDINGS

As the effector cells of repair, myofibroblasts migrate to the site of injury to deposit excessive amounts of matrix proteins and stimulate high levels of contraction. Myofibroblast activity is a decisive factor in whether a tissue is properly repaired by controlled wound healing or rendered fibrotic by deregulated repair. Extensive studies have documented the various contributing factors to an abrogated repair response. Though these fibrotic factors are known, very little is understood about the opposing antifibrotic molecules that assist in a successful repair, such as prostaglandin E2 (PGE₂) and ECM retraction. The following review will discuss the general development of fibrosis through the transformation of myofibroblasts, focusing primarily on the prominent profibrotic pathways of TGFβ and ECM tension and antifibrotic pathways of PGE₂ and ECM retraction.

CONCLUSIONS

The idea is to understand the ways in which the cell, after an injury and inflammatory response, normally controls its repair mechanisms through its homeostatic regulators so as to mimic them therapeutically to control abnormal pathways.

Endothelin-1 Drives Epithelial-Mesenchymal Transition in Hypertensive Nephroangiosclerosis

BACKGROUND

Tubulointerstitial fibrosis, the final outcome of most kidney diseases, involves activation of epithelial mesenchymal transition (EMT). Endothelin-1 (ET-1) activates EMT in cancer cells, but it is not known whether it drives EMT in the kidney. We therefore tested the hypothesis that tubulointerstitial fibrosis involves EMT driven by ET-1.

METHODS AND RESULTS

Transgenic TG[mRen2]27 (TGRen2) rats developing fulminant angiotensin II-dependent hypertension with prominent cardiovascular and renal damage were submitted to drug treatments targeted to ET-1 and/or angiotensin II receptor or left untreated (controls). Expressional changes of E-cadherin and α-smooth muscle actin (αSMA) were examined as markers of renal EMT. In human kidney HK-2 proximal tubular cells expressing the ETB receptor subtype, the effects of ET-1 with or without ET-1 antagonists were also investigated. The occurrence of renal fibrosis was associated with EMT in control TGRen2 rats, as evidenced by decreased E-cadherin and increased αSMA expression. Irbesartan and the mixed ET-1 receptor antagonist bosentan prevented these changes in a blood pressure-independent fashion (P < 0.001 for both versus controls). In HK-2 cells ET-1 blunted E-cadherin expression, increased αSMA expression (both P < 0.01), collagen synthesis, and metalloproteinase activity (P < 0.005, all versus untreated cells). All changes were prevented by the selective ETB receptor antagonist BQ-788. Evidence for involvement of the Rho-kinase signaling pathway and dephosphorylation of Yes-associated protein in EMT was also found.

CONCLUSIONS

In angiotensin II-dependent hypertension, ET-1 acting via ETB receptors and the Rho-kinase and Yes-associated protein induces EMT and thereby renal fibrosis.

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.

Fas/Fas Ligand pathways gene polymorphisms in pediatric renal allograft rejection

BACKGROUND

An essential milestone in pediatric transplantation is to find noninvasive biomarkers to monitor acute rejection (AR). In this retrospective (Case-control) study, we examined the role of Fas -670A/G and Fas Ligand (FasL) -843C/T gene polymorphisms in allograft nephropathy in pediatric renal transplant recipients.

METHODS

In 47 pediatric kidney transplant recipients and 20 healthy controls, Fas -670A/G and FasL -843C/T gene polymorphisms as well as serum soluble Fas Ligand level (sFasL) were measured.

RESULTS

Serum sFasL levels were significantly higher in transplant recipients children than that in controls (548.25±298.64pg/ml vs 143.17±44.55pg/ml, p=0.0001). There was no significant difference between patients with AR and those without AR in regards to serum sFasL levels (567.70±279.87pg/ml vs 507.85±342.80pg/ml, p=0.56). Fas -670A/G genotypes or alleles were not significantly different between controls and transplant recipients and among transplant recipients with and without AR. (P>0.05 for all). FasL -843C/T genotypes were not different between transplant recipients and controls and among transplant recipients with and without AR (P>0.05 for all). However, Frequency of C allele in transplant patients was significantly higher than that in the control group (44.68% vs 25%, P=0.03). FasL -843C/T alleles were significantly different between patients with and without AR (P=0.03). The percentages of C allele were higher in children with AR (58.82% vs 36.67%). We found that serum FasL and serum creatinine were variables that were independently associated with AR.

CONCLUSION

This study suggests that FasL gene polymorphisms in peripheral blood might be accurate in detecting cellular AR.

siRNA technology in kidney transplantation: current status and future potential

Kidney transplantation is one of the most common transplantation operations in the world, accounting for up to 50 % of all transplantation surgeries. To curtail the damage to transplanted organs that is caused by ischemia-reperfusion injury and the recipient's immune system, small interfering RNA (siRNA) technology is being explored. Importantly, the kidney as a whole is a preferential site for non-specific systemic delivery of siRNA. To date, most attempts at siRNA-based therapy for transplantation-related conditions have remained at the in vitro stage, with only a few of them being advanced into animal models. Hydrodynamic intravenous injection of naked or carrier-bound siRNAs is currently the most common route for delivery of therapeutic constructs. To our knowledge, no systematic screens for siRNA targets most relevant for kidney transplantation have been attempted so far. A majority of researchers have arrived at one or another target of interest by analyzing current literature that dissects pathological processes taking place in transplanted organs. A majority of the genes that make up the list of 53 siRNA targets that have been tested in transplantation-related models so far belong to either apoptosis- or immune rejection-centered networks. There is an opportunity for therapeutic siRNA combinations that may be delivered within the same delivery vector or injected at the same time and, by targeting more than one pathway, or by hitting the same pathways within two different key points, will augment the effects of each other.

Effect of erythropoietin on the expression of dynamin-related protein-1 in rat renal interstitial fibrosis

This study aimed to observe the expression of dynamin-related protein-1 (Drp-1) in the renal interstitium in a rat model of renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO). In addition, the renoprotective effect of erythropoietin in this model was investigated. A total of 81 rats were randomly assigned to sham surgery, UUO model and treatment groups. Following surgery, the rats in the treatment group were subcutaneously administered erythropoietin at a dose of 3,000 IU/kg once a week until the time of sacrifice. Rats in the sham surgery and UUO model groups were administered an identical volume of normal saline. In each group, nine rats were chosen randomly for sacrifice on days 7, 14 and 21 after surgery for histological examination of renal tissue. Renal tissue specimens were examined by hematoxylin and eosin and Masson's trichrome staining. Immunohistochemical analysis was performed to determine the expression of Drp-1 in the renal interstitium. Renal function damage, as evaluated by the measurement of serum creatinine (Cr) and blood urea nitrogen (BUN) levels, was less severe in the treatment group compared with that in the model group at day 21 (P<0.01). Compared with the UUO model group, the renal interstitial injury score and fibrotic area of the treatment group were decreased markedly at the three time points (P<0.05). The expression level of Drp-1 in the treatment group was decreased markedly at the three time points compared with that in the model group (P<0.05). In conclusion, the expression of Drp-1 is increased in rat renal interstitial fibrosis, and erythropoietin may alleviate the degree of renal interstitial fibrosis by downregulating the expression of Drp-1.

Increased plasma tissue inhibitors of metalloproteinase concentrations as negative predictors associated with deterioration of kidney allograft function upon long-term observation

Chronic allograft injury (CAI) is the most frequent cause of progressive kidney allograft impairment and eventual loss, which is due to interstitial fibrosis and tubular atrophy (IF/TA). Mechanisms of CAI are not fully understood. Chemokines, cytokines, metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs) play roles in fibrosis development. The aims of this study were to evaluate plasma and urine TIMPs (TIMP-1 and TIMP-2), MMPs (MMP-2 and MMP-9), proinflammatory interleukin-6 (IL-6), chemokine (C-C motif) ligand 2 (CCL2 chemokines previously known as monocyte chemoattractant protein-1 [MCP-1]) among 150 recipients beyond 1 year post-renal transplantations and to explore the usefulness of these potential biomarkers of ongoing allograft injury. Renal transplant recipients compared with healthy volunteers (control group) showed significantly increased plasma and urine IL-6, MMP-9, TIMP-1, and TIMP-2, as well as lower plasma MMP-2 and urine CCL2 concentrations. Compared with recipients showing good function those with impairments displayed higher plasma TIMP-1 (P < .001) and TIMP-2 (P = .003) concentrations. The recipient estimated glomerular filtration rate (eGFR) values negatively correlated with plasma TIMP-1 and TIMP-2 levels (r = -0.43; P < .0001 and rs = -0.42; P < .0001, respectively) and with urine IL-6 excretion (rs = -0.33; P < .0001). Multivariate and receiver operating characteristic (ROC) analyses showed TIMP-1 plasma level assessments to be useful estimates of allograft injury.

Genomic meta-analysis of growth factor and integrin pathways in chronic kidney transplant injury

BACKGROUND

Chronic Allograft Nephropathy (CAN) is a clinical entity of progressive kidney transplant injury. The defining histology is tubular atrophy with interstitial fibrosis (IFTA). Using a meta-analysis of microarrays from 84 kidney transplant biopsies, we revealed growth factor and integrin adhesion molecule pathways differentially expressed and correlated with histological progression. A bioinformatics approach mining independent datasets leverages new and existing data to identify correlative changes in integrin and growth factor signaling pathways.

RESULTS

Analysis of CAN/IFTA Banff grades showed that hepatocyte growth factor (HGF), and epidermal growth factor (EGF) pathways are significantly differentially expressed in all classes of CAN/IFTA. MAPK-dependent pathways were also significant. However, the TGFβ pathways, albeit present, failed to differentiate CAN/IFTA progression. The integrin subunits β8, αv, αμ and β5 are differentially expressed, but β1, β6 and α6 specifically correlate with progression of chronic injury. Results were validated using our published proteomic profiling of CAN/IFTA.

CONCLUSIONS

CAN/IFTA with chronic kidney injury is characterized by expression of distinct growth factors and specific integrin adhesion molecules as well as their canonical signaling pathways. Drug target mapping suggests several novel candidates for the next generation of therapeutics to prevent or treat progressive transplant dysfunction with interstitial fibrosis.

Discovery and validation of a molecular signature for the noninvasive diagnosis of human renal allograft fibrosis

BACKGROUND

Tubulointerstitial fibrosis (fibrosis), a histologic feature associated with a failing kidney allograft, is diagnosed using the invasive allograft biopsy. A noninvasive diagnostic test for fibrosis may help improve allograft outcome.

METHODS

We obtained 114 urine specimens from 114 renal allograft recipients: 48 from 48 recipients with fibrosis in their biopsy results and 66 from 66 recipients with normal biopsy results. Levels of messenger RNAs (mRNAs) in urinary cells were measured using kinetic, quantitative polymerase chain reaction assays, and the levels were related to allograft diagnosis. A discovery set of 76 recipients (32 with allograft fibrosis and 44 with normal biopsy results) was used to develop a diagnostic signature, and an independent validation set of 38 recipients (16 with allograft fibrosis and 22 with normal biopsy results) was used to validate the signature.

RESULTS

In the discovery set, urinary cell levels of the following mRNAs were significantly associated with the presence of allograft fibrosis: vimentin (P<0.0001, logistic regression model), hepatocyte growth factor (P<0.0001), α-smooth muscle actin (P<0.0001), fibronectin 1 (P<0.0001), perforin (P=0.0002), plasminogen activator inhibitor 1 (P=0.0002), transforming growth factor β1 (P=0.0004), tissue inhibitor of metalloproteinase 1 (P=0.0009), granzyme B (P=0.0009), fibroblast-specific protein 1 (P=0.006), CD103 (P=0.02), and collagen 1A1 (P=0.04). A four-gene model composed of the levels of mRNA for vimentin, NKCC2, and E-cadherin and of 18S ribosomal RNA provided the most accurate, parsimonious diagnostic model of allograft fibrosis with a sensitivity of 93.8% and a specificity of 84.1% (P<0.0001). In the independent validation set, this same model predicted the presence of allograft fibrosis with a sensitivity of 77.3% and a specificity of 87.5% (P<0.0001).

CONCLUSIONS

Measurement of mRNAs in urinary cells may offer a noninvasive means of diagnosing fibrosis in human renal allografts.

Phenolic secoiridoids in extra virgin olive oil impede fibrogenic and oncogenic epithelial-to-mesenchymal transition: extra virgin olive oil as a source of novel antiaging phytochemicals

The epithelial-to-mesenchymal transition (EMT) genetic program is a molecular convergence point in the life-threatening progression of organ fibrosis and cancer toward organ failure and metastasis, respectively. Here, we employed the EMT process as a functional screen for testing crude natural extracts for accelerated drug development in fibrosis and cancer. Because extra virgin olive oil (EVOO) (i.e., the juice derived from the first cold pressing of the olives without any further refining process) naturally contains high levels of phenolic compounds associated with the health benefits derived from consuming an EVOO-rich Mediterranean diet, we have tested the ability of an EVOO-derived crude phenolic extract to regulate fibrogenic and oncogenic EMT in vitro. High-performance liquid chromatography (HPLC) coupled to time-of-flight (TOF) mass spectrometry assays revealed that the EVOO phenolic extract was mainly composed (∼70%) of two members of the secoiridoid family of complex polyphenols, namely oleuropein aglycone-the bitter principle of olives-and its derivative decarboxymethyl oleuropein aglycone. EVOO secoiridoids efficiently prevented loss of proteins associated with polarized epithelial phenotype (i.e., E-cadherin) as well as de novo synthesis of proteins associated with mesenchymal migratory morphology of transitioning cells (i.e., vimentin). The ability of EVOO to impede transforming growth factor-β (TGF-β)-induced disintegration of E-cadherin-mediated cell-cell contacts apparently occurred as a consequence of the ability of EVOO phenolics to prevent the upregulation of SMAD4-a critical mediator of TGF-β signaling-and of the SMAD transcriptional cofactor SNAIL2 (Slug)-a well-recognized epithelial repressor. Indeed, EVOO phenolics efficiently prevented crucial TGF-β-induced EMT transcriptional events, including upregulation of SNAI2, TCF4, VIM (Vimentin), FN (fibronectin), and SERPINE1 genes. While awaiting a better mechanistic understanding of how EVOO phenolics molecularly shut down the EMT differentiation process, it seems reasonable to suggest that nontoxic Oleaceae secoiridoids certainly merit to be considered for aging studies and, perhaps, for ulterior design of more pharmacologically active second-generation anti-EMT molecules.

Correction of postkidney transplant anemia reduces progression of allograft nephropathy

Retrospective studies suggest that chronic allograft nephropathy might progress more rapidly in patients with post-transplant anemia, but whether correction of anemia improves renal outcomes is unknown. An open-label, multicenter, randomized controlled trial investigated the effect of epoetin-β to normalize hemoglobin values (13.0-15.0 g/dl, n=63) compared with partial correction of anemia (10.5-11.5 g/dl, n=62) on progression of nephropathy in transplant recipients with hemoglobin <11.5 g/dl and an estimated creatinine clearance (eCrCl) <50 ml/min per 1.73 m(2). After 2 years, the mean hemoglobin was 12.9 and 11.3 g/dl in the normalization and partial correction groups, respectively (P<0.001). From baseline to year 2, the eCrCl decreased by a mean 2.4 ml/min per 1.73 m(2) in the normalization group compared with 5.9 ml/min per 1.73 m(2) in the partial correction group (P=0.03). Furthermore, fewer patients in the normalization group progressed to ESRD (3 versus 13, P<0.01). Cumulative death-censored graft survival was 95% and 80% in the normalization and partial correction groups, respectively (P<0.01). Complete correction was associated with a significant improvement in quality of life at 6 and 12 months. The number of cardiovascular events was low and similar between groups. In conclusion, this prospective study suggests that targeting hemoglobin values ≥13 g/dl reduces progression of chronic allograft nephropathy in kidney transplant recipients.

Factors increasing quantitative interstitial fibrosis from 0 hr to 1 year in living kidney transplant patients receiving tacrolimus

BACKGROUND

This study investigated the increase in interstitial fibrosis (IF) from 0 hr to 1 month and 1 year posttransplantation in biopsy sections and assessed the risk of developing IF in 118 living kidney recipients.

METHODS

A quantitative analysis of IF was performed using computer-assisted imaging. The percent IF (%IF) in the cortical region at 0 hr was defined as the baseline, and the increases in %IF at 1 month and 1 year were calculated. Demographics, higher (regimen 1) and lower (regimen 2) target trough concentrations of tacrolimus, and the cytochrome P450 (CYP) 3A5 polymorphism were tested as risk factors.

RESULTS

The mean %IF at 0 hr, 1 month, and 1 year was 10.3%+/-4.2%, 15.0%+/-5.8%, and 19.0%+/-7.7%, respectively. %IF increased 1.7- and 2.2-fold from 0 hr to 1 month and 1 year posttransplantation, respectively. At 1 year, the increase was higher in patients with the CYP3A5*3/*3 genotype (nonexpressers), those treated with regimen 1, and those with a lower estimated glomerular filtration rate and higher body mass index. In a multivariate analysis, CYP3A5 nonexpression correlated with the development of IF (odds ratio 2.63, P=0.018). Tacrolimus blood levels in the early stage posttransplantation were higher in nonexpressers than CYP3A5 expressers in both regimens 1 and 2, despite therapeutic drug monitoring.

CONCLUSIONS

The higher concentrations of tacrolimus, especially in the nonexpressers treated with regimen 1, might influence the development of IF. This study suggested that a new regimen with lower and narrow target trough levels of tacrolimus or a dosing strategy based on the CYP3A5 genotype is needed to reduce the risk of developing IF.

Scar wars: mapping the fate of epithelial-mesenchymal-myofibroblast transition

The hypothesis that epithelial-mesenchymal transition (EMT) might be a contributor to the accumulation of fibroblasts and myofibroblasts (MFs) in the kidney during fibrogenesis was postulated 15 years ago. This paradigm offered an elegant explanation of how the loss of epithelial functions is coupled to the gain of deleterious mesenchymal functions; for example, excessive matrix deposition. Moreover, it interpreted chronic kidney disease in a developmental context: because the tubular epithelium originates from the metanephric mesenchyme, EMT can be viewed as a dedifferentiation process in response to injury, which might serve healing or--if dysregulated--might facilitate fibrosis. Several observations support the role of EMT in renal fibrosis: (1) Tubular cells can transform to fibroblasts and MFs in vitro. (2) Histological 'snapshots' reveal the coexistence of epithelial and mesenchymal markers in transitioning tubular cells in fibrosis models and human kidney diseases. (3) Early lineage-tracing experiments detected mesenchymal markers in the genetically tagged epithelium. However, the paradigm has been recently challenged; new fate-mapping studies found no evidence for the expression of (myo)fibroblast markers in the epithelium during fibrogenesis. This review summarizes the key findings and caveats, aiming at a balanced view, which neither overestimates the role of the epithelium in MF generation nor denies the importance of epithelial plasticity in fibrogenesis.

Fibroblasts and myofibroblasts in renal fibrosis

Interstitial fibrosis, associated with extensive accumulation of extracellular matrix constituents in the cortical interstitium, is directly correlated to progression of renal disease. The earliest histological marker of this progression is the accumulation in the interstitium of fibroblasts with the phenotypic appearance of myofibroblasts. These myofibroblasts are contractile cells that express alpha smooth muscle actin and incorporate it into intracellular stress fibres. Although fibroblasts are histologically visible in normal kidneys, there are relatively few of them and proximal tubular epithelial cells predominate. In progressive disease, however, the interstitium becomes filled with myofibroblasts. In this review, we will examine the phenotype and function of fibroblasts and myofibroblasts in the cortical interstitium and the processes that may modulate them.