Connective tissue growth factor is a biomarker and mediator of kidney allograft fibrosis

HK-2 cell response to TGF-β highly depends on cell culture medium formulations

The immortalized human renal proximal tubular epithelial cell line HK-2 is most commonly used to study renal cell physiology and human kidney diseases with tubulointerstitial fibrosis such as diabetic nephropathy, obstructive uropathy or allograft fibrosis. Epithelial-to-mesenchymal transition (EMT) is the main pathological process of tubulointerstitial fibrosis in vitro. Transforming growth factor-beta (TGF-β) is a key inducer of EMT. Several pro-fibrotic gene expression differences have been observed in a TGF-β-induced EMT model of HK-2 cells. However, growth conditions and medium formulations might greatly impact these differences. We investigated gene and protein expression of HK-2 cells cultured in six medium formulations. TGF-β1 increased the expression of ACTA2, TGFB1, COL4A1, EGR2, VIM and CTGF genes while reducing PPARG in all medium formulations. Interestingly, TGF-β1 treatment either increased or decreased EGR1, FN, IL6 and C3 gene expression, depending on medium formulations. The cell morphology was slightly affected, but immunoblots revealed TGFB1 and vimentin protein overexpression in all media. However, fibronectin expression as well as the nuclear translocation of EGR1 was medium dependent. In conclusion, our study demonstrates that, using the HK-2 in vitro model of EMT, the meticulous selection of appropriate cell culture medium formulation is essential to achieve reliable scientific results.

Protein Biomarkers in Chronic Kidney Disease in Children-What Do We Know So Far?

Chronic kidney disease (CKD) in children is a major concern of medical care and public health as it is related to high morbidity and mortality due to progression to end-stage kidney disease (ESKD). It is essential to identify patients with a risk of developing CKD to implement therapeutic interventions. Unfortunately, conventional markers of CKD, such as serum creatinine, glomerular filtration rate (GFR) and proteinuria, have many limitations in serving as an early and specific diagnostic tool for this condition. Despite the above, they are still the most frequently utilized as we do not have better. Studies from the last decade identified multiple CKD blood and urine protein biomarkers but mostly assessed the adult population. This article outlines some recent achievements and new perspectives in finding a set of protein biomarkers that might improve our ability to prognose CKD progression in children, monitor the response to treatment, or even become a potential therapeutic target.

Evaluation of interstitial fibrosis in chronic kidney disease by multiparametric functional MRI and histopathologic analysis

OBJECTIVES

To investigate the diagnostic value of functional MRI to assess renal interstitial fibrosis in patients with chronic kidney disease (CKD).

METHODS

We prospectively recruited 80 CKD patients who underwent renal biopsies and 16 healthy volunteers to undergo multiparametric functional MRI examinations. The Oxford MEST-C classification was used to score the interstitial fibrosis. The diagnostic performance of functional MRI to discriminate interstitial fibrosis was evaluated by calculating the area under the receiver operating characteristic (ROC) curves.

RESULTS

IgA nephropathy (60%) accounted for the majority of pathologic type in the CKD patients. Apparent diffusion coefficient (ADC) from diffusion-weighted imaging (DWI) was correlated with interstitial fibrosis (rho = -0.73). Decreased renal blood flow (RBF) derived from arterial spin labeling (rho = -0.78) and decreased perfusion fraction (f) derived from DWI (rho = -0.70) were accompanied by increased interstitial fibrosis. The T1 value from T1 mapping correlated with interstitial fibrosis (rho = 0.67) (all p < 0.01). The areas under the ROC curve for the discrimination of ≤ 25% vs. > 25% and ≤ 50% vs. > 50% interstitial fibrosis were 0.87 (95% confidence interval, 0.78 to 0.94) and 0.93 (0.86 to 0.98) by ADC, 0.84 (0.74 to 0.91) and 0.94 (0.86 to 0.98) by f, 0.93 (0.85 to 0.98) and 0.90 (0.82 to 0.96) by RBF, and 0.91 (0.83 to 0.96) and 0.77 (0.66 to 0.85) by T1, respectively.

CONCLUSIONS

Functional MRI parameters were strongly correlated with the interstitial fibrosis of CKD. Therefore, it might a powerful tool to assess interstitial fibrosis of CKD noninvasively.

KEY POINTS

• In CKD patients, the renal cortical ADC value decreased and T1 value increased significantly compared with healthy volunteers. • Functional MRI revealed significantly decreased renal perfusion in CKD patients compared with healthy volunteers. • The renal cortical ADC, f, RBF, and T1 values were strongly correlated with the interstitial fibrosis of CKD.

Molecular mechanisms of histone deacetylases and inhibitors in renal fibrosis progression

Renal fibrosis is a common progressive manifestation of chronic kidney disease. This phenomenon of self-repair in response to kidney damage seriously affects the normal filtration function of the kidney. Yet, there are no specific treatments for the condition, which marks fibrosis as an irreversible pathological sequela. As such, there is a pressing need to improve our understanding of how fibrosis develops at the cellular and molecular levels and explore specific targeted therapies for these pathogenic mechanisms. It is now generally accepted that renal fibrosis is a pathological transition mediated by extracellular matrix (ECM) deposition, abnormal activation of myofibroblasts, and epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells under the regulation of TGF-β. Histone deacetylases (HDACs) appear to play an essential role in promoting renal fibrosis through non-histone epigenetic modifications. In this review, we summarize the mechanisms of renal fibrosis and the signaling pathways that might be involved in HDACs in renal fibrosis, and the specific mechanisms of action of various HDAC inhibitors (HDACi) in the anti-fibrotic process to elucidate HDACi as a novel therapeutic tool to slow down the progression of renal fibrosis.

Role for exosomes with self-antigens and immune regulatory molecules in allo- and auto-immunity leading to chronic immune injury following murine kidney transplantation

OBJECTIVE

Antibodies against donor human leukocyte antigen are a risk factor for chronic immune injury (CII) following renal transplantation; however, it is often not detectable. The main goal of this study is to gain new insights into the kinetics of exosome release and content in sensitized vs non-sensitized recipients. Towards this, we investigated the role for circulating exosomes with allo and self-antigens as well as immunoregulatory molecules in the development of CII and acute rejection.

METHODS

Using murine kidney allograft rejection models, we investigated the role of exosomes on immune responses leading to allo- and auto-immunity to self-antigens resulting in rejection. Exosomes were analyzed for kidney self-antigens (Collagen-IV, fibronectin, angiotensin II receptor type 1), and immune-regulatory molecules (PD-L1, CD73) using western blot. Antibodies to donor MHC in serum samples were detected by immunofluorescence, self-antigens by enzyme-linked immunosorbent assay and kidney tissue infiltrating cells were determined by immunohistochemistry.

RESULTS

BALB/c; H2^d to C57BL/6; H2^b renal transplantation (BALB/c), resulted in tubulitis and cellular infiltration by day 14, suggestive of acute inflammation, that was self-limiting with functioning graft. This contributed to CII on post-transplant day >100, which was preceded by induction of exosomes with donor and self-antigens leading to antibodies and immune-regulatory molecules. The absence of acute rejection in this allogenic transplant model is likely due to the induction of splenic and, graft-infiltrating CD4 + FoxP3+ T regulatory cells. In contrast, prior sensitization by skin graft followed by kidney transplantation induced antibodies to MHC and self-antigens leading to acute rejection.

CONCLUSION

We demonstrate a pivotal role for induction of exosomes with immune-regulatory molecules, allo- and auto-immunity to self-antigens leading to chronic immune injury following murine kidney transplantation.

Chronic Allograft Injury

With the incremental improvements in long-term kidney transplant survival, there is renewed focus on what causes failure of the transplanted allograft. Over the past decade, our understanding of the injuries that lead to loss of graft function over time has evolved. Chronic allograft injury includes both immune-mediated and nonimmune-mediated injuries, which may involve the organ donor, the recipient, or both. The targets of injury include the kidney tubular epithelium, the endothelium, and the glomerulus. As a response to injury, there are the expected tissue remodeling and repair processes. However, if inflammation persists, which is not uncommon in the transplant setting, the resulting maladaptive response is matrix deposition and/or fibrosis. This ultimately leads to declining graft function and, finally, failure. With our advancing knowledge of the multiple etiologies and mechanisms, enhanced by more recent cohort studies in humans, there is an opportunity to identify those at greater risk to initiate new strategies to ameliorate the process. Although the most recent studies focus on immune-mediated injuries, there is a critical need to identify both markers of injury and mechanisms of injury. In this review, we highlight the findings of recent studies, highlight the potential therapeutic targets, and identify the continued unmet need for understanding the mechanisms of late graft failure.

Combination of Functional Magnetic Resonance Imaging and Histopathologic Analysis to Evaluate Interstitial Fibrosis in Kidney Allografts

BACKGROUND AND OBJECTIVES

Recent developments indicated that functional magnetic resonance imaging (MRI) could potentially provide noninvasive assessment of kidney interstitial fibrosis in patients with kidney diseases, but direct evidence from histopathology is scarce. We aimed to explore the diagnostic utilities of functional MRI for the evaluation of kidney allograft interstitial fibrosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We prospectively examined 103 kidney transplant recipients who underwent for-cause biopsies and 20 biopsy-proven normal subjects with functional MRI. Histomorphometric analyses of interstitial fibrosis and peritubular capillary densities were performed on digitally scanned Masson's trichrome- and CD34-stained slides, respectively. The performances of functional MRI to discriminate interstitial fibrosis were assessed by calculating the area under the curve using receiver-operating characteristic curve.

RESULTS

Main pathologic findings in this single-center cohort were representative of common diagnostic entities in the kidney allografts, with rejection (32%) and glomerulonephritides (31%) accounting for the majority of diagnoses. Apparent diffusion coefficient from diffusion-weighted imaging correlated with interstitial fibrosis (ρ=-0.77; P<0.001). Additionally, decreased arterial spin labelings were accompanied by peritubular capillary density reductions (r=0.77; P<0.001). Blood oxygen level-dependent (BOLD) imaging demonstrated cortical hypoxia with increasing interstitial fibrosis (ρ=0.61; P<0.001). The area under the curve for the discrimination of ≤25% versus >25% interstitial fibrosis and ≤50% versus >50% interstitial fibrosis were 0.87 (95% confidence interval [95% CI], 0.79 to 0.93) and 0.88 (95% CI, 0.80 to 0.93) by apparent diffusion coefficient, 0.92 (95% CI, 0.85 to 0.97) and 0.94 (95% CI, 0.87 to 0.98) by arterial spin labeling, 0.81 (95% CI, 0.72 to 0.88) and 0.86 (95% CI, 0.78 to 0.92) by perfusion fraction, 0.79 (95% CI, 0.69 to 0.87) and 0.85 (95% CI, 0.76 to 0.92) by BOLD imaging, respectively.

CONCLUSIONS

Functional MRI measurements were strongly correlated with kidney allograft interstitial fibrosis. The performances of functional MRI for discriminating ≤50% versus >50% interstitial fibrosis were good to excellent.

Selective Deletion of Heparan Sulfotransferase Enzyme, Ndst1, in Donor Endothelial and Myeloid Precursor Cells Significantly Decreases Acute Allograft Rejection

Early damage to transplanted organs initiates excess inflammation that can cause ongoing injury, a leading cause for late graft loss. The endothelial glycocalyx modulates immune reactions and chemokine-mediated haptotaxis, potentially driving graft loss. In prior work, conditional deficiency of the glycocalyx-modifying enzyme N-deacetylase-N-sulfotransferase-1 (Ndst1^f/f TekCre⁺) reduced aortic allograft inflammation. Here we investigated modification of heparan sulfate (HS) and chemokine interactions in whole-organ renal allografts. Conditional donor allograft Ndst1 deficiency (Ndst1^−/−; C57Bl/6 background) was compared to systemic treatment with M-T7, a broad-spectrum chemokine-glycosaminoglycan (GAG) inhibitor. Early rejection was significantly reduced in Ndst1^−/− kidneys engrafted into wildtype BALB/c mice (Ndst1^+/+) and comparable to M-T7 treatment in C57Bl/6 allografts (P < 0.0081). M-T7 lost activity in Ndst1^−/− allografts^, while M-T7 point mutants with modified GAG-chemokine binding displayed a range of anti-rejection activity. CD3+ T cells (P < 0.0001), HS (P < 0.005) and CXC chemokine staining (P < 0.012), gene expression in NFκB and JAK/STAT pathways, and HS and CS disaccharide content were significantly altered with reduced rejection. Transplant of donor allografts with conditional Ndst1 deficiency exhibit significantly reduced acute rejection, comparable to systemic chemokine-GAG inhibition. Modified disaccharides in engrafted organs correlate with reduced rejection. Altered disaccharides in engrafted organs provide markers for rejection with potential to guide new therapeutic approaches in allograft rejection.

Caspase-3 Is a Pivotal Regulator of Microvascular Rarefaction and Renal Fibrosis after Ischemia-Reperfusion Injury

Background Ischemia-reperfusion injury (IRI) is a major risk factor for chronic renal failure. Here, we characterize the different modes of programmed cell death in the tubular and microvascular compartments during the various stages of IRI-induced AKI, and their relative importance to renal fibrogenesis.Methods We performed unilateral renal artery clamping for 30 minutes and contralateral nephrectomy in wild-type mice (C57BL/6) or caspase-3^-/- mice.Results Compared with their wild-type counterparts, caspase-3^-/- mice in the early stage of AKI had high urine cystatin C levels, tubular injury scores, and serum creatinine levels. Electron microscopy revealed evidence of tubular epithelial cell necrosis in caspase-3^-/- mice, and immunohistochemistry showed upregulation of the necroptosis marker receptor-interacting serine/threonine-protein kinase 3 (RIPK3) in renal cortical sections. Western blot analysis further demonstrated enhanced levels of phosphorylated RIPK3 in the kidneys of caspase-3^-/- mice. In contrast, caspase-3^-/- mice had less microvascular congestion and activation in the early and extension phases of AKI. In the long term (3 weeks after IRI), caspase-3^-/- mice had reduced microvascular rarefaction and renal fibrosis, as well as decreased expression of α-smooth muscle actin and reduced collagen deposition within peritubular capillaries. Moreover, caspase-3^-/- mice exhibited signs of reduced tubular ischemia, including lower tubular expression of hypoxia-inducible factor-1α and improved tubular injury scores.Conclusions These results establish the pivotal importance of caspase-3 in regulating microvascular endothelial cell apoptosis and renal fibrosis after IRI. These findings also demonstrate the predominant role of microvascular over tubular injury as a driver of progressive renal damage and fibrosis after IRI.

Rapeseed protein-derived antioxidant peptide RAP alleviates renal fibrosis through MAPK/NF-κB signaling pathways in diabetic nephropathy

Introduction

Kidney fibrosis is the main pathologic change in diabetic nephropathy (DN), which is the major cause of end-stage renal disease. Current therapeutic strategies slow down but cannot reverse the progression of renal dysfunction in DN. Plant-derived bioactive peptides in foodstuffs are widely used in many fields because of their potential pharmaceutical and nutraceutical benefits. However, this type of peptide has not yet been studied in renal fibrosis of DN. Previous studies have indicated that the peptide YWDHNNPQIR (named RAP), a natural peptide derived from rapeseed protein, has an antioxidative stress effect. The oxidative stress is believed to be associated with DN. The aim of this study was to evaluate the pharmacologic effects of RAP against renal fibrosis of DN and high glucose (HG)-induced mesangial dysfunction.

Materials and methods

Diabetes was induced by streptozotocin and high-fat diet in C57BL/6 mice and these mice were treated by subcutaneous injection of different doses of RAP (0.1 mg/kg and 0.5 mg/kg, every other day) or PBS for 12 weeks. Later, functional and histopathologic analyses were performed. Parallel experiments verifying the molecular mechanism by which RAP alleviates DN were carried out in HG-induced mesangial cells (MCs).

Results

RAP improved the renal function indices, including 24-h albuminuria, triglyceride, serum creatinine, and blood urea nitrogen levels, but did not lower blood glucose levels in DN mice. RAP also simultaneously attenuated extracellular matrix accumulation in DN mice and HG-induced MCs. Furthermore, RAP reduced HG-induced cell proliferation, but it showed no toxicity in MCs. Additionally, RAP inhibited the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways.

Conclusion

RAP can attenuate fibrosis in vivo and in vitro by antagonizing the MAPK and NF-κB pathways.

TGF-β1 Inhibits Human Trophoblast Cell Invasion by Upregulating Connective Tissue Growth Factor Expression

Appropriate trophoblast invasion into the maternal endometrium is essential for successful human implantation and placentation. Connective tissue growth factor (CTGF), also known as CCN2, is a matricellular protein that is expressed in the placenta. Interestingly, the CTGF expression levels in the placenta and serum from patients with severe preeclampsia or fetal growth restriction are higher than those from healthy controls. However, to date, the role of CTGF in the regulation of trophoblast cell invasion remains unclear. Transforming growth factor-β1 (TGF-β1) is a potent stimulator of CTGF expression and has been shown to inhibit trophoblast cell invasiveness. However, whether CTGF mediates TGF-β1-inhibited human trophoblast cell invasion is unknown. In the present study, we show that treatment with TGF-β1 upregulates CTGF expression in a human trophoblast cell line, HTR-8/SVneo, and in primary human trophoblast cells. Our results also demonstrate that the SMAD2/3 signaling pathways are required for TGF-β1-induced upregulation of CTGF. Importantly, CTGF knockdown attenuates TGF-β1-inhibited cell invasion. Furthermore, cell invasiveness is decreased by treatment with recombinant CTGF. These results provide evidence that CTGF mediates TGF-β1-inhibited human trophoblast cell invasion.

Tubulointerstitial expression and urinary excretion of connective tissue growth factor 3 months after renal transplantation predict interstitial fibrosis and tubular atrophy at 5 years in a retrospective cohort analysis

Connective tissue growth factor (CTGF) is an important mediator of renal allograft fibrosis, and urinary CTGF (CTGFu) levels correlate with the development of human allograft interstitial fibrosis. We evaluated the predictive value of CTGF protein expression in 160 kidney transplant recipients with paired protocol biopsies at 3 months and 5 years after transplantation. At month 3 and year 1, CTGFu was measured using ELISA, and biopsies were immunohistochemically stained for CTGF, with semiquantitative scoring of tubulointerstitial CTGF-positive area (CTGFti). Predictors of interstitial fibrosis and tubular atrophy (IF/TA) severity at 5 years were donor age [OR 1.05 (1.02-1.08), P = 0.001], female donor [OR 0.40 (0.18-0.90), P = 0.026], induction therapy [OR 2.76 (1.10-6.89), P = 0.030], and CTGFti >10% at month 3 [OR 2.72 (1.20-6.15), P = 0.016]. In subgroups of patients with little histologic damage at 3 months [either ci score 0 (n = 119), IF/TA score ≤1 (n = 123), or absence of IF/TA, interstitial inflammation, and tubulitis (n = 45)], consistent predictors of progression of chronic histologic damage by 5 years were donor age, induction therapy, CTGFti >10%, and CTGFu. These results suggest that, even in patients with favorable histology at 3 months, significant CTGF expression is often present which may predict accelerated accumulation of histologic damage.

Antagonism of profibrotic microRNA-21 improves outcome of murine chronic renal allograft dysfunction

Chronic renal allograft dysfunction (CAD) is a major limiting factor of long-term graft survival. It is characterized by interstitial fibrosis and tubular atrophy. The underlying pathomechanisms are incompletely understood. MicroRNAs are powerful regulators of gene expression and may have an impact on various diseases by direct mRNA decay or translational inhibition. A murine model of allogenic kidney transplantation was used resulting in CAD at 6 weeks after kidney transplantation. We identified fibrosis-associated miR-21a-5p by whole miRNAome expression analysis to be among the most highly upregulated miRNAs. In vitro in renal fibroblasts, miR-21a-5p was transcriptionally activated by interleukin 6-induced signal transducer and activator of transcription 3. Co-culture of LPS-activated macrophages with renal fibroblasts increased expression levels of miR-21a-5p and markers of fibrosis and inflammation. In addition, mature miR-21a-5p was secreted by macrophages in small vesicles, which were internalized by renal fibroblasts, thereby promoting profibrotic and proinflammatory effects. Notch2 receptor was identified as a potential target of miR-21a-5p and validated by luciferase gene reporter assays. Therapeutic silencing of miR-21a-5p in mice after allogenic kidney transplantation resulted in an amelioration of CAD, as indicated by a reduction in fibrosis development, inflammatory cell influx, tissue injury and BANFF lesion scoring. In a life-supporting model, miR-21a-5p antagonism had beneficial effects on kidney function. miR-21a-5p silencing may therefore be a viable therapeutic option in the treatment of patients following kidney transplantation to halt the development of CAD.

ELISA of CCN Family Proteins in Body Fluids Including Serum and Plasma

Enzyme-linked immunosorbent assay (ELISA) is the most popular methodology for absolute quantification of particular proteins in liquid samples. Especially for CCN family members that are associated with human diseases, utility of ELISA for those proteins in clinics as well as research laboratories is emphasized. However, in order to obtain accurate and stable results in ELISA, particular care should be taken in controlling the quality and quantity of standard CCN family proteins, which bind to various materials and can be unstable in a purified form. Recently, diagnostic value of the CCN family protein fragments in body fluids has been indicated in several diseases. Therefore, module-specific detection system for the CCN family members is desired as a promising tool in clinics. It should be also noted that modular fragments of CCN family members can be more stable than the full-length in purified forms, whose quality may be easier to control than that of the full-length ones.

Connective tissue growth factor (CTGF/CCN2) in haemophilic arthropathy and arthrofibrosis: a histological analysis

INTRODUCTION

Joint haemorrhage is the principal clinical manifestation of haemophilia frequently leading to advanced arthropathy and arthrofibrosis, resulting in severe disability. The degree and prevalence of arthrofibrosis in hemophilic arthropathy is more severe than in other forms of arthropathy. Expression of connective tissue growth factor (CTGF) has been linked to many fibrotic diseases, but has not been studied in the context of haemophilic arthropathy.

AIM

We aim to compare synovial tissues histologically from haemophilia and osteoarthritis patients with advanced arthropathy in order to compare expression of proteins that are possibly aetiologic in the development of arthrofibrosis.

METHODS

Human synovial tissues were obtained from 10 haemophilia and 10 osteoarthritis patients undergoing joint surgery and processed for histology and immunohistochemistry.

RESULTS

All samples from haemophilia patients had synovitis with hypertrophy and hyperplasia of synovial villi. Histologically, synovial tissues contained hyperplastic villi with increased cellularity and abundant haemosiderin- and ferritin-pigmented macrophage-like cells (HMCs), with a perivascular localization in the sub-surface layer. CTGF staining was observed in the surface layer and sub-surface layer in all haemophilia patients, exclusively co-localizing with HMCs. Quantification showed that the extent of CTGF-positive areas was correlated with the degree of detection of HMCs. CTGF was not observed in any of the samples from osteoarthritis patients.

CONCLUSION

Using histological analysis, we showed that CTGF expression is elevated in haemophilia patients with arthrofibrosis and absent in patients with osteoarthritis. Additionally, we found that CTGF is always associated with haemosiderin-pigmented macrophage-like cells, which suggests that CTGF is produced by synovial A cells following the uptake of blood breakdown products.

A LASSO Method to Identify Protein Signature Predicting Post-transplant Renal Graft Survival

Identifying novel biomarkers to predict renal graft survival is important in post-transplant clinical practice. Serum creatinine, currently the most popular surrogate biomarker, offers limited information of the underlying allograft profiles. It is known to perform unsatisfactorily to predict renal function. In this paper, we apply a LASSO machine-learning algorithm in the Cox proportional hazards model to identify promising proteins that are associated with the hazard of allograft loss after renal transplantation, motivated by a clinical pilot study that collected 47 patients receiving renal transplants at the University of Michigan Hospital. We assess the association of 17 proteins previously identified by Cibrik et al. [5] with allograft rejection in our regularized Cox regression analysis, where the LASSO variable selection method is applied to select important proteins that predict the hazard of allograft loss. We also develop a post-selection inference to further investigate the statistical significance of the proteins on the hazard of allograft loss, and conclude that two proteins KIM-1 and VEGF-R2 are important protein markers for risk prediction.

Mechanism of tacrolimus-induced chronic renal fibrosis following transplantation is regulated by ox-LDL and its receptor, LOX-1

Chronic renal allograft dysfunction (CRAD) is the most common cause of graft failure following renal transplantation. However, the underlying mechanisms remain to be fully elucidated. Immunosuppressants and hyperlipidemia are associated with renal fibrosis following long-term use. The present study aimed to determine the effects of tacrolimus (FK506) and lipid metabolism disorder on CRAD. In vitro and in vivo models were used for this investigation. Cells of the mouse proximal renal tubular epithelial cell strain, NRK-52E, were cultured either with oxidized low-density lipoprotein (ox-LDL), FK506, ox-LDL combined with FK506, or vehicle, respectively. Changes in cell morphology and changes in the levels of lectin-like ox-LDL receptor-1 (LOX-1), reactive oxygen species (ROS), hydrogen peroxide and fibrosis-associated genes were evaluated at 24, 48 and 72 h. In separate experiment, total of 60 Sprague-Dawley rats were divided randomly into four groups, which included a high-fat group, FK506 group, high-fat combined with FK506 group, and control group. After 2, 4 and 8 weeks, the serum lipid levels, the levels of ox-LDL, ROS, and the expression levels of transforming growth factor (TGF)-β1 and connective tissue growth factor were determined. The in vitro and in vivo models revealed that lipid metabolism disorder and FK506 caused oxidative stress and a fibrogenic response. In addition, decreased levels of LOX-1 markedly reduced the levels of TGF-β1 in the in vitro model. Taken together, FK506 and dyslipidemia were found to be associated with CRAD following transplantation.

Plasma CTGF is independently related to an increased risk of cardiovascular events and mortality in patients with atherosclerotic disease: the SMART study

AIMS

Connective tissue growth factor (CTGF) plays a key role in tissue fibrogenesis and growing evidence indicates a pathogenic role in cardiovascular disease. Aim of this study is to investigate the association of connective tissue growth factor (CTGF/CCN2) with cardiovascular risk and mortality in patients with manifest vascular disease.

METHODS AND RESULTS

Plasma CTGF was measured by ELISA in a prospective cohort study of 1227 patients with manifest vascular disease (mean age 59.0 ± 9.9 years). Linear regression analysis was performed to quantify the association between CTGF and cardiovascular risk factors. Results are expressed as beta (β) regression coefficients with 95% confidence intervals (CI). The relation between CTGF and the occurrence of new cardiovascular events and mortality was assessed with Cox proportional hazard analysis. Adjustments were made for potential confounding factors. Plasma CTGF was positively related to total cholesterol (β 0.040;95%CI 0.013-0.067) and LDL cholesterol (β 0.031;95%CI 0.000-0.062) and inversely to glomerular filtration rate (β -0.004;95%CI -0.005 to -0.002). CTGF was significantly lower in patients with cerebrovascular disease. During a median follow-up of 6.5 years (IQR 5.3-7.4) 131 subjects died, 92 experienced an ischemic cardiac complication and 45 an ischemic stroke. CTGF was associated with an increased risk of new vascular events (HR 1.21;95%CI 1.04-1.42), ischemic cardiac events (HR 1.41;95%CI 1.18-1.67) and all-cause mortality (HR 1.18;95%CI 1.00-1.38) for every 1 nmol/L increase in CTGF. No relation was observed between CTGF and the occurrence of ischemic stroke.

CONCLUSIONS

In patients with manifest vascular disease, elevated plasma CTGF confers an increased risk of new cardiovascular events and all-cause mortality.

Autophagy fosters myofibroblast differentiation through MTORC2 activation and downstream upregulation of CTGF

Recent evidence suggests that autophagy may favor fibrosis through enhanced differentiation of fibroblasts in myofibroblasts. Here, we sought to characterize the mediators and signaling pathways implicated in autophagy-induced myofibroblast differentiation. Fibroblasts, serum starved for up to 4 d, showed increased LC3-II/-I ratios and decreased SQSTM1/p62 levels. Autophagy was associated with acquisition of markers of myofibroblast differentiation including increased protein levels of ACTA2/αSMA (actin, α 2, smooth muscle, aorta), enhanced gene and protein levels of COL1A1 (collagen, type I, α 1) and COL3A1, and the formation of stress fibers. Inhibiting autophagy with 3 different class I phosphoinositide 3-kinase and class III phosphatidylinositol 3-kinase (PtdIns3K) inhibitors or through ATG7 silencing prevented myofibroblast differentiation. Autophagic fibroblasts showed increased expression and secretion of CTGF (connective tissue growth factor), and CTGF silencing prevented myofibroblast differentiation. Phosphorylation of the MTORC1 target RPS6KB1/p70S6K kinase was abolished in starved fibroblasts. Phosphorylation of AKT at Ser473, a MTORC2 target, was reduced after initiation of starvation but was followed by spontaneous rephosphorylation after 2 d of starvation, suggesting the reactivation of MTORC2 with sustained autophagy. Inhibiting MTORC2 activation with long-term exposure to rapamycin or by silencing RICTOR, a central component of the MTORC2 complex abolished AKT rephosphorylation. Both RICTOR silencing and rapamycin treatment prevented CTGF and ACTA2 upregulation, demonstrating the central role of MTORC2 activation in CTGF induction and myofibroblast differentiation. Finally, inhibition of autophagy with PtdIns3K inhibitors or ATG7 silencing blocked AKT rephosphorylation. Collectively, these results identify autophagy as a novel activator of MTORC2 signaling leading to CTGF induction and myofibroblast differentiation.

Rapamycin increases CCN2 expression of lung fibroblasts via phosphoinositide 3-kinase

Excessive production of connective tissue growth factor (CTGF, CCN2) and increased motor ability of the activated fibroblast phenotype contribute to the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, molecules and signal pathways regulating CCN2 expression and migration of lung fibroblasts are still elusive. We hypothesize that rapamycin, via binding and blocking mammalian target of rapamycin (mTOR) complex (mTORC), affects CCN2 expression and migration of lung fibroblasts in vitro. Primary normal and fibrotic human lung fibroblasts were isolated from lung tissues of three patients with primary spontaneous pneumothorax and three with IPF. Cells were incubated with regular medium, or medium containing rapamycin, human recombinant transforming growth factor (TGF)-β1, or both. CCN2 and tissue inhibitor of metalloproteinase (TIMP)-1 expression in cells or supernatant was detected. Wound healing and migration assay was used to measure the migratory potential. TGF-β type I receptor (TβRI)/Smad inhibitor, SB431542 and phosphoinositide 3-kinase (PI3K) inhibitor, LY294002 were used to determine rapamycin's mechanism of action. We demonstrated that rapamycin amplified basal or TGF-β1-induced CCN2 mRNA and protein expression in normal or fibrotic fibroblasts by Smad-independent but PI3K-dependent pathway. Additionally, rapamycin also enhanced TIMP-1 expression as indicated by ELISA. However, wound healing and migrating assay showed rapamycin did not affect the mobility of fibroblasts. Collectively, this study implies a significant fibrogenic induction activity of rapamycin by activating AKT and inducing CCN2 expression in vitro and provides the possible mechanisms for the in vivo findings which previously showed no antifibrotic effect of rapamycin on lung fibrosis.

How tubular epithelial cells dictate the rate of renal fibrogenesis?

The main threat to a kidney injury, whatever its cause and regardless of whether it is acute or chronic, is the initiation of a process of renal fibrogenesis, since fibrosis can auto-perpetuate and is of high prognostic significance in individual patients. In the clinic, a decrease in glomerular filtration rate correlates better with tubulointerstitial damage than with glomerular injury. Accumulation of the extracellular matrix should not be isolated from other significant cellular changes occurring in the kidney, such as infiltration by inflammatory cells, proliferation of myofibroblasts, obliteration of peritubular capillaries and atrophy of tubules. The aim of this review is to focus on tubular epithelial cells (TEC), which, necessarily involved in the repair process, eventually contribute to accelerating fibrogenesis. In the context of injury, TEC rapidly exhibit phenotypic and functional changes that recall their mesenchymal origin, and produce several growth factors known to activate myofibroblasts. Because they are high-demanding energy cells, TEC will subsequently suffer from the local hypoxia that progressively arises in a microenvironment where the matrix increases and capillaries become rarified. The combination of hypoxia and metabolic acidosis may induce a vicious cycle of sustained inflammation, at the center of which TEC dictate the rate of renal fibrogenesis.

Therapeutic targets for treating fibrotic kidney diseases

Renal fibrosis is the hallmark of virtually all progressive kidney diseases and strongly correlates with the deterioration of kidney function. The renin-angiotensin-aldosterone system blockade is central to the current treatment of patients with chronic kidney disease (CKD) for the renoprotective effects aimed to prevent or slow progression to end-stage renal disease (ESRD). However, the incidence of CKD is still increasing, and there is a critical need for new therapeutics. Here, we review novel strategies targeting various components implicated in the fibrogenic pathway to inhibit or retard the loss of kidney function. We focus, in particular, on antifibrotic approaches that target transforming growth factor (TGF)-β1, a key mediator of kidney fibrosis, and exciting new data on the role of autophagy. Bone morphogenetic protein (BMP)-7 and connective tissue growth factor (CTGF) are highlighted as modulators of profibrotic TGF-β activity. BMP-7 has a protective role against TGF-β1 in kidney fibrosis, whereas CTGF enhances TGF-β-mediated fibrosis. We also discuss recent advances in the development of additional strategies for antifibrotic therapy. These include strategies targeting chemokine pathways via CC chemokine receptors 1 and 2 to modulate the inflammatory response, inhibition of phosphodiesterase to restore nitric oxide-cyclic 3',5'-guanosine monophosphate function, inhibition of nicotinamide adenine dinucleotide phosphate oxidase 1 and 4 to suppress reactive oxygen species production, and inhibition of endothelin 1 or tumor necrosis factor α to ameliorate progressive renal fibrosis. Furthermore, a brief overview of some of the biomarkers of kidney fibrosis is currently being explored that may improve the ability to monitor antifibrotic therapies. It is hoped that evidence based on the preclinical and clinical data discussed in this review leads to novel antifibrotic therapies effective in patients with CKD to prevent or delay progression to ESRD.

Renal allograft fibrosis: biology and therapeutic targets

Renal tubulointerstitial fibrosis is the final common pathway of progressive renal diseases. In allografts, it is assessed with tubular atrophy as interstitial fibrosis/tubular atrophy (IF/TA). IF/TA occurs in about 40% of kidney allografts at 3-6 months after transplantation, increasing to 65% at 2 years. The origin of renal fibrosis in the allograft is complex and includes donor-related factors, in particular in case of expanded criteria donors, ischemia-reperfusion injury, immune-mediated damage, recurrence of underlying diseases, hypertensive damage, nephrotoxicity of immunosuppressants, recurrent graft infections, postrenal obstruction, etc. Based largely on studies in the non-transplant setting, there is a large body of literature on the role of different cell types, be it intrinsic to the kidney or bone marrow derived, in mediating renal fibrosis, and the number of mediator systems contributing to fibrotic changes is growing steadily. Here we review the most important cellular processes and mediators involved in the progress of renal fibrosis, with a focus on the allograft situation, and discuss some of the challenges in translating experimental insights into clinical trials, in particular fibrosis biomarkers or imaging modalities.

A perspective on anti-CCN2 therapy for chronic kidney disease

Kidney fibrosis is the common end point of chronic kidney disease independent of aetiology. Currently, no effective therapy exists to reduce kidney fibrosis. CCN2 appears to be an interesting candidate for anti-fibrotic drug targeting, because it holds a central position in the development of kidney fibrosis and interacts with a variety of factors that are involved in the fibrotic response, including transforming growth factor (TGF) β and Bone morphogenetic proteins. Although CCN2 modifies many pathways, it does not appear to have a membrane receptor of its own. Numerous experimental and clinical studies lowering CCN2 bioavailability have shown promising results with minimal adverse side effects. This review aims to provide an overview of the current state of CCN2 research with a focus on anti-fibrotic therapy.

Targeting CTGF, EGF and PDGF pathways to prevent progression of kidney disease

Chronic kidney disease (CKD) is a major health and economic burden with a rising incidence. During progression of CKD, the sustained release of proinflammatory and profibrotic cytokines and growth factors leads to an excessive accumulation of extracellular matrix. Transforming growth factor β (TGF-β) and angiotensin II are considered to be the two main driving forces in fibrotic development. Blockade of the renin-angiotensin-aldosterone system has become the mainstay therapy for preservation of kidney function, but this treatment is not sufficient to prevent progression of fibrosis and CKD. Several factors that induce fibrosis have been identified, not only by TGF-β-dependent mechanisms, but also by TGF-β-independent mechanisms. Among these factors are the (partially) TGF-β-independent profibrotic pathways involving connective tissue growth factor, epidermal growth factor and platelet-derived growth factor and their receptors. In this Review, we discuss the specific roles of these pathways, their interactions and preclinical evidence supporting their qualification as additional targets for novel antifibrotic therapies.

Results of the 4th scientific workshop of the ECCO (Group II): markers of intestinal fibrosis in inflammatory bowel disease

The fourth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on intestinal fibrosis in inflammatory bowel disease (IBD). The objective was to better understand basic mechanisms and markers of intestinal fibrosis as well as to suggest new therapeutic targets to prevent or treat fibrosis. The results of this workshop are presented in three separate manuscripts. This section describes markers of fibrosis in IBD, identifies unanswered questions in the field and provides a framework for future studies addressing the unmet needs in the field of intestinal fibrosis.

Biological pathways and potential targets for prevention and therapy of chronic allograft nephropathy

Renal transplantation (RT) is the best option for patients with end-stage renal disease, but the half-life is limited to a decade due to progressive deterioration of renal function and transplant failure from chronic allograft nephropathy (CAN), which is the leading cause of transplant loss. Extensive research has been done to understand the pathogenesis, the biological pathways of fibrogenesis, and potential therapeutic targets for the prevention and treatment of CAN. Despite the advancements in the immunosuppressive agents and patient care, CAN continues to remain an unresolved problem in renal transplantation. The aim of this paper is to undertake a comprehensive review of the literature on the pathogenesis, biological pathways of RT fibrogenesis, and potential therapeutic targets for the prevention and therapy of CAN.

Urinary connective tissue growth factor is associated with human renal allograft fibrogenesis

BACKGROUND

Connective tissue growth factor (CTGF) is a key mediator of tissue fibrogenesis in kidney disease. Its involvement in renal allograft fibrosis was recently demonstrated in a mouse model.

METHODS

We prospectively studied the association between urinary CTGF (CTGFu) levels and renal allograft fibrosis during the first 2 years after transplantation. Histologic and biochemical data were collected from 315 kidney transplant recipients enrolled in a protocol biopsy-based clinical program.

RESULTS

At 3, 12, and 24 months after transplantation, CTGFu levels were independently associated with the degree of interstitial fibrosis in protocol biopsies, scored according to the revised 1997 Banff criteria. In a subgroup of 164 patients with pristine biopsies at 3 months, higher CTGFu levels at 3 months were associated with moderate and severe interstitial fibrosis developed at 24 months after transplantation.

CONCLUSIONS

As it is readily quantifiable in urine, a role for CTGFu as a noninvasive candidate biomarker and predictor of human renal allograft fibrogenesis deserves further study.

Identification of a protein signature in renal allograft rejection

PURPOSE

Serum creatinine functions as a poor surrogate marker of renal allograft dysfunction and long-term graft survival. By measuring multiple proteins simultaneously in the serum of transplant patients, we can identify unique protein signatures of graft dysfunction.

EXPERIMENTAL DESIGN

We utilized training and validation cohorts composed of healthy and volunteer subjects, stable renal transplant patients, and renal transplant patients experiencing acute allograft rejection. Utilizing our antibody microarray, we measured 108 proteins simultaneously in these groups.

RESULTS

Using Mann-Whitney tests with Bonferroni correction, we identified ten serum proteins from 19 renal transplant patients with stable renal function, which are differentially expressed, compared to healthy control subjects. In addition, we identified 17 proteins that differentiate rejecting renal transplant recipients from stable renal transplant. Validation cohorts substantiated these findings.

CONCLUSION AND CLINICAL RELEVANCE

Our preliminary results support that a specific pattern of protein expression or "protein signature" may be able to differentiate between stable transplant patients from those with rejection. Future studies will focus on other etiologies of renal allograft dysfunction and the effect of treatment on protein expression and long-term outcome.

Systematic review of mouse kidney transplantation

A mouse model of kidney transplantation was first described in 1973 by Skoskiewicz et al. Although the mouse model is technically difficult, it is attractive for several reasons: the mouse genome has been characterized and in many aspects is similar to man and there is a greater diversity of experimental reagents and techniques available for mouse studies than other experimental models. We reviewed the literature on all studies of mouse kidney transplantation to report the donor and recipient strain combinations that have been investigated and the resultant survival and histological outcomes. Some models of kidney transplantation have used the transplanted kidney as a life-supporting organ, however, in many studies the recipient mouse's native kidney has been left in situ. Several different combinations of inbred mouse strains have been reported, with varying degrees of injury, survival or tolerance because of haplotype differences. This model has been exceptionally useful as an investigational tool to understand multiple aspects of transplantation including acute rejection, cellular and humoral rejection mechanisms and their treatment. Furthermore, this model has been used to investigate disease mechanisms beyond transplant rejection including intrinsic renal disease and infection-associated pathology.

Epithelial phenotypic changes are associated with a tubular active fibrogenic process in human renal grafts

Some recently published works contest the epithelial origin of myofibroblasts, which are the major extracellular matrix producers. However, our previous studies showed that, in tubular cells, some phenotypic changes reminiscent of epithelial-to-mesenchymal transition constitute an interesting early marker that predicts the progression of fibrosis in renal grafts. We hypothesized that activated epithelial cells could directly contribute to fibrogenesis, although they remain within the tubules. Using immunohistochemistry, we studied the association between epithelial phenotypic changes (de novo expression of vimentin and intracellular translocation of β-catenin) and the production of profibrotic molecules (connective tissue growth factor, HSP47, and laminin), in tubular epithelial cells from 93 renal grafts biopsied of 77 patients. We observed the de novo production of connective tissue growth factor, HSP47, and laminin in the tubular epithelial cells displaying epithelial phenotypic changes. The score of vimentin was significantly correlated with those of connective tissue growth factor (r = 0.785, P < .0001), HSP47 (r = 0.887, P < .0001), and laminin (r = 0.836, P < .0001). The level of tubular expression of mesenchymal cell markers and profibrogenic molecules, but not graft histologic lesions according to Banff acute or chronic scores, was correlated with graft dysfunction and proteinuria at the time of biopsy (r = -0.611, P < .0001 for vimentin with estimated glomerular filtration rate) (r = 0.42, P = .0006 for vimentin with proteinuria). Our results demonstrate that the epithelial phenotypic switch is associated with an active fibrogenic process in tubular epithelial cells and with graft injury indicators. Perpetuation of this tissue injury-repair response may drive fibrogenesis in renal grafts. This "repair response" represents an interesting marker for renal graft surveillance.

Chronic renoprotective effect of pulsatile perfusion machine RM3 and IGL-1 solution in a preclinical kidney transplantation model

BACKGROUND

Machine perfusion (MP) of kidney graft provides benefits against preservation injury, however decreased graft quality requires optimization of the method. We examined the chronic benefits of MP on kidney grafts and the potential improvements provided by IGL-1 solution.

METHOD

We used an established autotransplantation pig kidney model to study the effects of MP against the deleterious effects of warm ischemia (WI: 60 minutes) followed by 22 hours of cold ischemia in MP or static cold storage (CS) followed by autotransplantation. MPS and IGL-1 solutions were compared.

RESULTS

Animal survival was higher in MPS-MP and both IGL groups. Creatinine measurement did not discriminate between the groups, however MPS-MP and both IGL groups showed decreased proteinuria. Chronic fibrosis level was equivalent between the groups. RTqPCR and immunohistofluorescent evaluation showed that MP and IGL-1 provided some protection against epithelial to mesenchymal transition and chronic lesions. IGL-1 was protective with both MP and CS, particularly against chronic inflammation, with only small differences between the groups.

CONCLUSION

IGL-1 used in either machine or static preservation offers similar levels of protection than standard MP. The compatibility of IGL-1 with both machine perfusion and static storage could represent an advantage for clinical teams when choosing the correct solution to use for multi-organ collection. The path towards improving machine perfusion, and organ quality, may involve the optimization of the solution and the correct use of colloids.

Vectorial secretion of CTGF as a cell-type specific response to LPA and TGF-β in human tubular epithelial cells

BACKGROUND

Increased expression of the pro-fibrotic protein connective tissue growth factor (CTGF) has been detected in injured kidneys and elevated urinary levels of CTGF are discussed as prognostic marker of chronic kidney disease. There is evidence that epithelial cells lining the renal tubular system contribute to uptake and secretion of CTGF. However, the role of different types of tubular epithelial cells in these processes so far has not been addressed in primary cultures of human cells.

RESULTS

Tubular epithelial cells of proximal and distal origin were isolated from human kidneys and cultured as polarized cells in insert wells. The pro-fibrotic stimuli lysophosphatidic acid (LPA) and transforming growth factor β (TGF-β) were used to induce CTGF secretion.LPA activated CTGF secretion in proximal tubular cells when applied from either the apical or the basolateral side as shown by immunocytochemistry. CTGF was secreted exclusively to the apical side. Signaling pathways activated by LPA included MAP kinase and Rho kinase signaling. TGF-β applied from either side also stimulated CTGF secretion primarily to the apical side with little basolateral release.Interestingly, TGF-β activation induced different signaling pathways depending on the side of TGF-β application. Smad signaling was almost exclusively activated from the basolateral side most prominently in cells of distal origin. Only part of these cells also synthesized CTGF indicating that Smad activation alone was not sufficient for CTGF induction. MAP kinases were involved in apical TGF-β-mediated activation of CTGF synthesis in proximal cells and a subset of epithelial cells of distal origin. This subpopulation of distal tubular cells was also able to internalize recombinant apical CTGF, in addition to proximal cells which were the main cells to take up exogenous CTGF.

CONCLUSIONS

Analysis of polarized human primary renal epithelial cells in a transwell system shows that vectorial secretion of the pro-fibrotic protein CTGF depends on the cell type, the stimulus and the signaling pathway activated. In all conditions, CTGF was secreted mainly to the apical side upon TGF-β and LPA treatment and therefore, likely contributes to increased urinary CTGF levels in vivo. Moreover, CTGF secreted basolaterally may be active as paracrine pro-fibrotic mediator.

A knotless technique for kidney transplantation in the mouse

Mouse models of kidney transplantation are important to study molecular mechanisms of organ transplant rejection as well as to develop new therapeutic strategies aimed at improving allograft survival. However, the surgical technique necessary to result in a viable allograft has traditionally proven to be complex and very demanding. Here, we introduce a new, simple, and rapid knotless technique for vessel anastomosis wherein the last stitch of the anastomosis is not tied to the short end of the upper tie as in the classical approach but is left free. This is a critical difference in that it allows the size of the anastomosis to be increased or decreased after graft reperfusion in order to avoid stenosis or bleeding, respectively. We compared the outcome of this new knotless technique (n = 175) with the classical approach (n = 122) in terms of local thrombosis or bleeding, time for anastomosis, and survival rates. By this modification of the suture technique, local thrombosis was significantly reduced (1.1% versus 6.6%), anastomosis time was less, and highly reproducible kidney graft survival was achieved (95% versus 84% with the classical approach). We believe that this knotless technique is easy to learn and will improve the success rates in the technically demanding model of mouse kidney transplantation.

Mycophenolate mofetil and FK506 have different effects on kidney allograft fibrosis in rats that underwent chronic allograft nephropathy

Background

Tacrolimus (FK506) is associated with renal fibrosis in long-term use. Mycophenolatemofetil (MMF) can also inhibit or attenuate the progression of renal fibrosis. This study aimed to determine the different effects of FK506 and MMF on fibrosis-associated genes in the kidney in rats that underwent chronic allograft nephropathy (CAN).

Methods

Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. All recipients were given Cyclosporin A (CsA) 10 mg/kg^-1.d^-1 × 10 day and were then randomly divided into three oral treatment groups (n = 9 in each group): (1) the vehicle group was given vehicle orally; (2) the FK506 group was given 0.15 mg/kg^-1.d^-1 FK506; and (3) the MMF group was given 20 mg/kg^-1.d^-1 MMF. At 4, 8, and 12 weeks post-transplantation, serum creatinine (SCr), collagen deposition, Connective tissue growth factor (CTGF), alpha smooth muscle actin (α-SMA) and E-cadherin expressions were determined and hematoxylin-eosin (HE) and Periodic acid-Schiff (PAS) stains were performed.

Results

Renal function progressively deteriorated and showed typical CAN morphology in the vehicle and FK506 groups, while SCr and inflammatory infiltration (Banff score) showed a significant decrease in the MMF group after 8 weeks post-transplantation compared with those in the other groups (p < 0.05). Furthermore, expression levels of CTGF and α-SMA in the MMF group were significantly reduced, and the down-regulated expression of E-cadherin was abated (p < 0.05).

Conclusions

MMF showed favorable effects on renal interstitial fibrosis, thus efficiently retarding the progression of CAN.

The molecular legacy of apoptosis in transplantation

Transplanted organs have to cope with diverse immunologic and metabolic stressors that augment the percentage of stressed and dying cells. Cell death, whether apoptotic or necrotic, is crucial in various transplantation-associated conditions. Necrosis, a proinflammatory type of cell death classically considered as accidental, is increasingly recognized as a highly controlled death program. Apoptosis, the classical programmed cell death mode program, is tightly orchestrated and culminates in the activation of caspases. Apoptosis was classically regarded as a silent form of cell death, but mounting evidence indicates that apoptotic cells "don't go silently" and leave a heritage to the local microenvironment. This apoptotic legacy, embedded within the effector phase of apoptosis, is aimed, at least in part, at controlling leukocyte trafficking and fostering tissue remodeling at sites of apoptotic cell deletion and can promote maladaptive remodeling pathways of importance for obliterative vascular remodeling. Moreover, apoptotic cells can transfer bioactive molecules by the release of apoptotic membrane vesicles that, in turn, shapes the phenotype and functions of immune cells. In this review, we summarize recent data highlighting the importance of apoptosis-associated intercellular communication networks in the regulation of allograft remodeling and immune responses in transplantation.

Adaptive immunity rather than viral cytopathology mediates polyomavirus-associated nephropathy in mice

Nephropathy associated with BK polyomavirus causes kidney allograft dysfunction and failure. Understanding the pathogenesis of polyomavirus-associated allograft nephropathy (PVAN) is hampered by the species specificity of Polyomaviridae family members. Using a mouse polyomavirus (MPyV) kidney transplant model, we investigated clinically relevant variables that may contribute to PVAN. We found that the timing and source (i.e. donor vs. recipient) of MPyV infection and the titer of the viral inoculum have significant effects on the extent of allograft injury, with acute infection of the recipient by high-titer MPyV inoculums producing the most profound PVAN. In contrast, altering the degree of MHC matching or increasing ischemia/reperfusion injury by prolonging the cold ischemic time of the allograft did not affect the severity of PVAN. Survival correlated positively with serum creatinine levels, but not with viral loads in the kidney allograft. Using splenectomized alymphoplasia mice, which are unable to mount primary adaptive immune responses, we further demonstrate that persistent high viral loads in the kidney are not sufficient to cause advanced PVAN. These findings suggest that the mechanism of PVAN in mice is not a direct consequence of viral cytopathology, but rather involves interplay between viral infection and the recipient antidonor immune response.

Clinical significance of connective tissue growth factor in hepatitis B virus-induced hepatic fibrosis

AIM: To determine the utility of connective tissue growth factor (CCN2/CTGF) for assessing hepatic fibrosis in hepatitis B virus (HBV)-induced chronic liver diseases (CLD-B).

METHODS: Enzyme-linked immunosorbent assay was used to measure CCN2 in sera from 107 patients with chronic hepatitis B (CHB) and 39 patients with HBV-induced active liver cirrhosis and 30 healthy individuals. Liver samples from 31 patients with CHB, 8 patients with HBV-induced liver cirrhosis and 8 HBV carriers with normal liver histology were examined for transforming growth factor β-1 (TGF-β1) or CCN2 mRNA levels by in situ hybridization, and computer image analysis was performed to measure integrated optimal density (IOD) of CCN2 mRNA-positive cells in liver tissues. Histological inflammation grading and fibrosis staging were evaluated by H and E staining and Van Gieson’s method.

RESULTS: Serum CCN2 concentrations were, respectively, 4.0- or 4.9-fold higher in patients with CHB or active liver cirrhosis as compared to healthy individuals (P < 0.01). There was good consistency between the levels of CCN2 in sera and CCN2 mRNA expression in liver tissues (r = 0.87, P < 0.01). The levels of CCN2 in sera were increased with the enhancement of histological fibrosis staging in patients with CLD-B (r = 0.85, P < 0.01). Serum CCN2 was a reliable marker for the assessment of liver fibrosis, with areas under the receiver operating characteristic (ROC) curves (AUC) of 0.94 or 0.85 for, respectively, distinguishing normal liver controls from patients with F1 stage liver fibrosis or discriminating between mild and significant fibrosis.

CONCLUSION: Detection of serum CCN2 in patients with CLD-B may have clinical significance for assessment of severity of hepatic fibrosis.

Rapamycin is less fibrogenic than Cyclosporin A as demonstrated in a rat model of chronic allograft nephropathy

BACKGROUND

Cyclosporin A (CsA) is associated with significant chronic nephrotoxicity, which typically manifests as renal fibrosis. In contrast, rapamycin (RAPA) has been shown to inhibit fibrosis. This study sought to determine the effect of CsA and RAPA on the expression of connective tissue growth factor (CTGF) and E-cadherin in a rat kidney model of chronic allograft nephropathy.

MATERIALS AND METHODS

Left renal grafts from male Fisher (F344, RT1(1v1)) rats were orthotopically transplanted into Lewis (LEW, RT1(1)) rats. After transplantation, all recipients were given CsA 10 mg/kg(-1) d(-1) for 10 d and divided into three groups (n = 9/group): (1) vehicle, administered orally; (2) CsA, 6 mg/kg(-1) d(-1); (3) RAPA, 0.8 mg/kg(-1) d(-1). At 4, 8, and 12 wk posttransplantation, the kidney allografts were harvested and serum creatinine levels were measured. Connective tissue growth factor expression was determined using real-time polymerase chain reaction and Western blot. Kidney allografts sections also underwent hematoxylin-eosin and Masson trichrome staining, in addition to CTGF and E-cadherin immunostaining.

RESULTS

The serum creatinine levels were increased at 8 and 12 wk posttransplantation and were significantly lower in the RAPA group (P < 0.05). The Banff score also showed a significant decrease at 4, 8, and 12 wk (P < 0.05). CTGF messenger ribonucleic acid and protein levels were significantly lower in the RAPA group (P < 0.05), whereas E-cadherin expression was higher in the RAPA group at 4, 8, and 12 wk (P < 0.05). Masson's trichrome staining showed a significant decrease in collagen deposition at 8 and 12 wk after RAPA treatment.

CONCLUSION

RAPA can ameliorate fibrogenesis in kidney allografts by inhibiting epithelial-mesenchymal transition process, whereas CsA did not have this effect.

Effect of GFR on plasma N-terminal connective tissue growth factor (CTGF) concentrations

BACKGROUND

Connective tissue growth factor (CTGF) has a key role in the pathogenesis of renal and cardiac fibrosis. Its amino-terminal fragment (N-CTGF), the predominant form of CTGF detected in plasma, has a molecular weight in the middle molecular range (18 kDa). However, it is unknown whether N-CTGF is a uremic retention solute that accumulates in chronic kidney disease (CKD) due to decreased renal clearance and whether it can be removed by hemodiafiltration.

STUDY DESIGN

4 observational studies in patients and 2 pharmacokinetic studies in rodents.

SETTING & PARTICIPANTS

4 single-center studies. First study (cross-sectional): 88 patients with CKD not receiving kidney replacement therapy. Second study (cross-sectional): 23 patients with end-stage kidney disease undergoing low-flux hemodialysis. Third study: 9 kidney transplant recipients before and 6 months after transplant. Fourth study: 11 low-flux hemodialysis patients and 12 hemodiafiltration patients before and after one dialysis session.

PREDICTOR

First, second, and third study: (residual) glomerular filtration rate (GFR). Fourth study: dialysis modality.

OUTCOMES & MEASUREMENTS

Plasma (N-)CTGF concentrations, measured by enzyme-linked immunosorbent assay.

RESULTS

In patients with CKD, we observed an independent association between plasma CTGF level and estimated GFR (β = -0.72; P < 0.001). In patients with end-stage kidney disease, plasma CTGF level correlated independently with residual kidney function (β = -0.55; P = 0.046). Successful kidney transplant resulted in a decrease in plasma CTGF level (P = 0.008) proportional to the increase in estimated GFR. Plasma CTGF was not removed by low-flux hemodialysis, whereas it was decreased by 68% by a single hemodiafiltration session (P < 0.001). Pharmacokinetic studies in nonuremic rodents confirmed that renal clearance is the major elimination route of N-CTGF.

LIMITATIONS

Observational studies with limited number of patients. Fourth study: nonrandomized, evaluation of the effect of one session; randomized longitudinal study is warranted.

CONCLUSION

Plasma (N-)CTGF is eliminated predominantly by the kidney, accumulates in CKD, and is decreased substantially by a single hemodiafiltration session.

The insulin-like growth factor system in chronic kidney disease: Pathophysiology and therapeutic opportunities

The growth hormone-insulin-like growth factor-insulin-like growth factor binding protein (GH-IGF-IGFBP) axis plays a critical role in the maintenance of normal renal function and the pathogenesis and progression of chronic kidney disease (CKD). Serum IGF-I and IGFBPs are altered with different stages of CKD, the speed of onset, the amount of proteinuria, and the potential of remission. Recent studies demonstrate that growth failure in children with CKD is due to a relative GH insensitivity and functional IGF deficiency. The functional IGF deficiency in CKD results from either IGF resistance due to increased circulating levels of IGFBPs or IGF deficiency due to increased urinary excretion of serum IGF-IGFBP complexes. In addition, not only GH and IGFs in circulation, but locally produced IGFs, the high-affinity IGFBPs, and low-affinity insulin-like growth factor binding protein-related proteins (IGFBP-rPs) may also affect the kidney. With respect to diabetic kidney disease, there is growing evidence suggesting that GH, IGF-I, and IGFBPs are involved in the pathogenesis of diabetic nephropathy (DN). Thus, prevention of GH action by blockade either at the receptor level or along its signal transduction pathway offers the potential for effective therapeutic opportunities. Similarly, interrupting IGF-I and IGFBP actions also may offer a way to inhibit the development or progression of DN. Furthermore, it is well accepted that the systemic inflammatory response is a key player for progression of CKD, and how to prevent and treat this response is currently of great interest. Recent studies demonstrate existence of IGF-independent actions of high-affinity and low-affinity-IGFBPs, in particular, antiinflammatory action of IGFBP-3 and profibrotic action of IGFBP-rP2/CTGF. These findings reinforce the concept in support of the clinical significance of the IGF-independent action of IGFBPs in the assessment of pathophysiology of kidney disease and its therapeutic potential for CKD. Further understanding of GH-IGF-IGFBP etiopathophysiology in CKD may lead to the development of therapeutic strategies for this devastating disease. It would hold promise to use of GH, somatostatin analogs, IGFs, IGF agonists, GHR and insulin-like growth factor-I receptor (IGF-IR) antagonists, IGFBP displacer, and IGFBP antagonists as well as a combination treatment as therapeutic agents for CKD.

Connective tissue growth factor (CTGF/CCN2) ELISA: a novel tool for monitoring fibrosis

BACKGROUND

Connective tissue growth factor (CTGF) has been identified as a key factor in the pathogenesis of diseases with significant fibrosis-related complications such as hepatitis, diabetes and renal transplantation. Increasing evidence shows that CTGF levels in plasma, serum and urine have promising biomarker applicability in these disorders.

OBJECTIVE

To present an overview of current knowledge on CTGF in various patient populations and the technical aspects of CTGF measurement by enzyme-linked immunosorbent assay (ELISA).

METHOD

We performed a comprehensive literature search by using electronic bibliographic databases.

CONCLUSION

CTGF is associated with disease severity parameters and outcome in fibrotic disease and may have diagnostic and prognostic values. However, CTGF ELISA needs standardization.

Immune biomarker panel monitoring utilizing IDO enzyme activity and CD4 ATP levels: prediction of acute rejection vs. viral replication events

Infections have become as important an event as acute rejection posttransplant for long-term allograft survival. Less invasive biomarkers tested so far predict risk for one event or the other, not both. We prospectively tested blood and urine monthly for 12 months posttransplant from children receiving a kidney transplant. The IDO enzyme pathway was assessed by MS assays using the ratio of product l-kyn to substrate trp. Kyn/trp ratios and blood CD4 T-cell ATP levels were correlated with acute rejection or major infection events or stable group (no events) in the next 30 days. The 25 subjects experienced six discrete episodes of acute rejection in five subjects and 16 discrete events of major infection in 14 subjects (seven BK viruria, six cytomegaloviremia, one EB and cytomegaloviremia, and two transplant pyelonephritis). Mean serum kyn/trp ratios were significantly elevated in the group that experienced acute rejection (p = 0.02). Within-subject analyses revealed that over time, urine kyn/trp ratios showed an increase (p = 0.01) and blood CD4-ATP levels showed a decrease (p = 0.007) prior to a major infection event. These pilot results suggest that a panel of biomarkers together can predict over- or under-immunosuppression, but need independent validation.

Contribution of epithelial plasticity to renal transplantation-associated fibrosis

Every year in the United States, 5000 renal transplant recipients start or restart dialysis because of the unusual propensity of these allografts to develop interstitial fibrosis and tubular atrophy (IF/TA). Although IF/TA often follows one or more identifiable events, our capacity to specifically treat, prevent, or even detect IF/TA at an early stage is poor. These limitations are largely related to our lack of adequate tools to assess graft failure over time. Data accumulated over the past 5 years have demonstrated that tubular epithelial cells may react to certain fibrogenic stimuli to engage in the process of epithelial-to-mesenchymal transition (EMT). In this review, we highlight the current view of EMT with a focus on both its role in the context of renal transplantation and the potential for utilizing markers of EMT to identify patients undergoing early IF/TA.

Immune monitoring and biomarkers to predict chronic allograft dysfunction

Late failure of a kidney transplant continues to be a major problem after transplantation, in spite of more potent immunosuppressive strategies and the focus of clinical management shifting toward prolonging long-term graft survival. It is now recognized that graft failure occurs because of two major complications: death with a functioning graft and intrinsic allograft failure. Recent studies of late kidney graft loss have indicated a complexity of findings, including etiologies that are both immune and non-immune. These studies suggest that late graft failure is not an inevitable fact and that further investigation into the etiology of transplant graft failure may lead to a new understanding of the biology that will provide novel therapeutic strategies and biomarkers. In this review, we will focus on late allograft failure due to intrinsic injury to the transplant. The role of immune monitoring will be discussed in the context of monitoring for ongoing injury or for identifying late injury. A variety of methodologies have been used, including genomics, proteomics, and metabolomics, not only for monitoring allograft injury but also for identifying markers of graft failure that are more sensitive than serum creatinine. The available studies, as they relate to late or chronic graft injury, will also be reviewed.

Review: Serum and urine biomarkers of kidney disease: A pathophysiological perspective

The use of reliable biomarkers is becoming increasingly important for the improved management of patients with acute and chronic kidney diseases. Recent developments have identified a number of novel biomarkers in serum or urine that can determine the potential risk of kidney damage, distinguish different types of renal injury, predict the progression of disease and have the potential to assess the efficacy of therapeutic intervention. Some of these biomarkers can be used independently while others are more beneficial when used in combination with knowledge of other clinical risk factors. Advances in gene expression analysis, chromatography, mass spectrometry and the development of sensitive enzyme-linked immunosorbent assays have facilitated accurate quantification of many biomarkers. This review primarily focuses on describing new and established biomarkers, which identify and measure the various pathophysiological processes that promote kidney disease. It provides an overview of some of the different classes of renal biomarkers that can be assessed in serum/plasma and urine, including markers of renal function, oxidative stress, structural and cellular injury, immune responses and fibrosis. However, it does not explore the current status of these biomarkers in terms of their clinical validation.