Intragraft tubular vimentin and CD44 expression correlate with long-term renal allograft function and interstitial fibrosis and tubular atrophy

CD44 expression in renal tubular epithelial cells in the kidneys of rats with cyclosporine-induced chronic kidney disease

Renal tubular epithelial cell (TEC) injury is the most common cause of drug-induced kidney injury (DIKI). Although TEC regeneration facilitates renal function and structural recovery following DIKI, maladaptive repair of TECs leads to irreversible fibrosis, resulting in chronic kidney disease (CKD). CD44 is specifically expressed in TECs during maladaptive repair in several types of rat CKD models. In this study, we investigated CD44 expression and its role in renal fibrogenesis in a cyclosporine (CyA) rat model of CKD. Seven-week-old male Sprague-Dawley rats fed a low-salt diet were subcutaneously administered CyA (0, 15, or 30 mg/kg) for 28 days. CD44 was expressed in atrophic, dilated, and hypertrophic TECs in the fibrotic lesions of the CyA groups. These TECs were collected by laser microdissection and evaluated by microarray analysis. Gene ontology analysis suggested that these TECs have a mesenchymal phenotype, and pathway analysis identified CD44 as an upstream regulator of fibrosis-related genes, including fibronectin 1 (Fn1). Immunohistochemistry revealed that epithelial and mesenchymal markers of TECs of fibrotic lesions were downregulated and upregulated, respectively, and that these TECs were surrounded by a thickened basement membrane. In situ hybridization revealed an increase in Fn1 mRNA in the cytoplasm of TECs of fibrotic lesions, whereas fibronectin protein was localized in the stroma surrounding these tubules. Enzyme-linked immunosorbent assay revealed increased serum CD44 levels in CyA-treated rats. Collectively, these findings suggest that CD44 contributes to renal fibrosis by inducing fibronectin secretion in TECs exhibiting partial epithelial-mesenchymal transition and highlight the potential of CD44 as a biomarker of renal fibrosis.

Role of CD44 expressed in renal tubules during maladaptive repair in renal fibrogenesis in an allopurinol-induced rat model of chronic kidney disease

The kidney is a major target organ for the adverse effects of pharmaceuticals; renal tubular epithelial cells (TECs) are particularly vulnerable to drug-induced toxicity. TECs have regenerative capacity; however, maladaptive repair of TECs after injury leads to renal fibrosis, resulting in chronic kidney disease (CKD). We previously reported the specific expression of CD44 in failed-repair TECs of rat CKD model induced by ischemia reperfusion injury. Here, we investigated the pathophysiological role of CD44 in renal fibrogenesis in allopurinol-treated rat CKD model. Dilated or atrophic TECs expressing CD44 in fibrotic areas were collected by laser microdissection and subjected to microarray analysis. Gene ontology showed that extracellular matrix (ECM)-related genes were upregulated and differentiation-related genes were downregulated in dilated/atrophic TECs. Ingenuity Pathway Analysis identified CD44 as an upstream regulator of fibrosis-related genes, including Fn1, which encodes fibronectin. Immunohistochemistry demonstrated that dilated/atrophic TECs expressing CD44 showed decreases in differentiation markers of TECs and clear expression of mesenchymal markers during basement membrane attachment. In situ hybridization revealed an increase in Fn1 mRNA in the cytoplasm of dilated/atrophic TECs, whereas fibronectin was localized in the stroma around these TECs, supporting the production/secretion of ECM by dilated/atrophic TECs. Overall, these data indicated that dilated/atrophic TECs underwent a partial epithelial-mesenchymal transition (pEMT) and that CD44 promoted renal fibrogenesis via induction of ECM production in failed-repair TECs exhibiting pEMT. CD44 was detected in the urine and serum of APL-treated rats, which may reflect the expression of CD44 in the kidney.

Laser capture microdissection on formalin-fixed and paraffin-embedded renal transplanted biopsies: Technical perspectives for clinical practice application

Renal biopsy (RBx) is an essential tool in the diagnostic and therapeutic process of most native kidney diseases and in the renal transplanted graft. Laser capture microdissection (LCM), combined with molecular biology, might improve the diagnostic power of RBx. However, the limited amount of available renal tissue is often an obstacle for achieving a satisfactory qualitative and quantitative analysis. In our work we present a method which allows us to obtain good quality and quantity of RNA from formalin-fixed and paraffin-embedded (FFPE) renal tissue derived from RBx performed in transplanted patients. Histology, immunohistochemistry, LCM, pre-amplify system and qRT-PCR of biomarkers related to tubular damage, inflammation and fibrosis on FFPE RBx were performed. Glomeruli, tubules and interstitium of three RBx (RB-A: no alteration; RB-B and -C: the progressive rise of creatinine) were compared. The method proposed, could well be useful in future clinical practice. It is quick, easy to perform and allows the analyses of many biomarkers. In addition, it could be extended to all types of RBx without any limitation on the sample amount. Nevertheless, the need for a higher number of well-trained technicians might represent some limitation, counterbalanced by the opportunity to elaborate more accurate diagnosis and, consequently, more targeted therapies.

Progress in drug delivery system for fibrosis therapy

Fibrosis is a necessary process in the progression of chronic disease to cirrhosis or even cancer, which is a serious disease threatening human health. Recent studies have shown that the early treatment of fibrosis is turning point and particularly important. Therefore, how to reverse fibrosis has become the focus and research hotspot in recent years. So far, the considerable progress has been made in the development of effective anti-fibrosis drugs and targeted drug delivery. Moreover, the existing research results will lay the foundation for more breakthrough delivery systems to achieve better anti-fibrosis effects. Herein, this review summaries anti-fibrosis delivery systems focused on three major organ fibrotic diseases such as liver, pulmonary, and renal fibrosis accompanied by the elaboration of relevant pathological mechanisms, which will provide inspiration and guidance for the design of fibrosis drugs and therapeutic systems in the future.

Transforming growth factor-β-mediated CD44/STAT3 signaling contributes to the development of atrial fibrosis and fibrillation

Atrial fibrillation (AF) is associated with atrial fibrosis. Inhibition of atrial fibrosis might be a plausible approach for AF prevention and therapy. This study is designed to evaluate the potential role of CD44, a membrane receptor known to regulate fibrosis, and its related signaling in the pathogenesis of atrial fibrosis and AF. Treatment of cultured rat atrial fibroblasts with transforming growth factor-β (TGF-β, a key mediator of atrial fibrosis) led to a higher expression of hyaluronan (HA), CD44, STAT3, and collagen (a principal marker of fibrosis) than that of ventricular fibroblasts. In vivo, TGF-β transgenic mice and AF patients exhibited a greater expression of HA, CD44, STAT3, and collagen in their atria than wild-type mice and sinus rhythm subjects, respectively. Treating TGF-β transgenic mice with an anti-CD44 blocking antibody resulted in a lower expression of STAT3 and collagen in their atria than those with control IgG antibody. Programmed stimulation triggered less AF episodes in TGF-β transgenic mice treated with anti-CD44 blocking antibody than in those with control IgG. Blocking CD44 signaling with anti-CD44 antibody and mutated CD44 plasmids attenuated TGF-β-induced STAT3 activation and collagen expression in cultured atrial fibroblasts. Deletion and mutational analysis of the collagen promoter along with chromatin immunoprecipitation demonstrated that STAT3 served as a vital transcription factor in collagen expression. TGF-β-mediated HA/CD44/STAT3 pathway plays a crucial role in the development of atrial fibrosis and AF. Blocking CD44-dependent signaling may be a feasible way for AF management.

Oligo-fucoidan prevents renal tubulointerstitial fibrosis by inhibiting the CD44 signal pathway

Tubulointerstitial fibrosis is recognized as a key determinant of progressive chronic kidney disease (CKD). Fucoidan, a sulphated polysaccharide extracted from brown seaweed, exerts beneficial effects in some nephropathy models. The present study evaluated the inhibitory effect of oligo-fucoidan (800 Da) on renal tubulointerstitial fibrosis. We established a mouse CKD model by right nephrectomy with transient ischemic injury to the left kidney. Six weeks after the surgery, we fed the CKD mice oligo-fucoidan at 10, 20, and 100 mg/kg/d for 6 weeks and found that the oligo-fucoidan doses less than 100 mg/kg/d improved renal function and reduced renal tubulointerstitial fibrosis in CKD mice. Oligo-fucoidan also inhibited pressure-induced fibrotic responses and the expression of CD44, β-catenin, and TGF-β in rat renal tubular cells (NRK-52E). CD44 knockdown downregulated the expression of β-catenin and TGF-β in pressure-treated cells. Additional ligands for CD44 reduced the anti-fibrotic effect of oligo-fucoidan in NRK-52E cells. These data suggest that oligo-fucoidan at the particular dose prevents renal tubulointerstitial fibrosis in a CKD model. The anti-fibrotic effect of oligo-fucoidan may result from interfering with the interaction between CD44 and its extracellular ligands.

Renal Fibrosis mRNA Classifier: Validation in Experimental Lithium-Induced Interstitial Fibrosis in the Rat Kidney

Accurate diagnosis of fibrosis is of paramount clinical importance. A human fibrosis classifier based on metzincins and related genes (MARGS) was described previously. In this investigation, expression changes of MARGS genes were explored and evaluated to examine whether the MARGS-based algorithm has any diagnostic value in a rat model of lithium nephropathy. Male Wistar rats (n = 12) were divided into 2 groups (n = 6). One group was given a diet containing lithium (40 mmol/kg food for 7 days, followed by 60mmol/kg food for the rest of the experimental period), while a control group (n = 6) was fed a normal diet. After six months, animals were sacrificed and the renal cortex and medulla of both kidneys removed for analysis. Gene expression changes were analysed using 24 GeneChip^® Affymetrix Rat Exon 1.0 ST arrays. Statistically relevant genes (p-value<0.05, fold change>1.5, t-test) were further examined. Matrix metalloproteinase-2 (MMP2), CD44, and nephroblastoma overexpressed gene (NOV) were overexpressed in the medulla and cortex of lithium-fed rats compared to the control group. TGFβ2 was overrepresented in the cortex of lithium-fed animals 1.5-fold, and 1.3-fold in the medulla of the same animals. In Gene Set Enrichment Analysis (GSEA), both the medulla and cortex of lithium-fed animals showed an enrichment of the MARGS, TGFβ network, and extracellular matrix (ECM) gene sets, while the cortex expression signature was enriched in additional fibrosis-related-genes and the medulla was also enriched in immune response pathways. Importantly, the MARGS-based fibrosis classifier was able to classify all samples correctly. Immunohistochemistry and qPCR confirmed the up-regulation of NOV, CD44, and TGFβ2. The MARGS classifier represents a cross-organ and cross-species classifier of fibrotic conditions and may help to design a test to diagnose and to monitor fibrosis. The results also provide evidence for a common pathway in the pathogenesis of 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.

Fibrosis progression according to epithelial-mesenchymal transition profile: a randomized trial of everolimus versus CsA

Markers of epithelial-mesenchymal transition (EMT) may identify patients at high risk of graft fibrogenesis who could benefit from early calcineurin inhibitor (CNI) withdrawal. In a randomized, open-label, 12-month trial, de novo kidney transplant patients received cyclosporine, enteric-coated mycophenolate sodium (EC-MPS) and steroids to month 3. Patients were stratified as EMT+ or EMT- based on month 3 biopsy, then randomized to start everolimus with half-dose EC-MPS (720 mg/day) and cyclosporine withdrawal (CNI-free) or continue cyclosporine with standard EC-MPS (CNI). The primary endpoint was progression of graft fibrosis (interstitial fibrosis/tubular atrophy [IF/TA] grade increase ≥1 between months 3-12) in EMT+ patients. 194 patients were randomized (96 CNI-free, 98 CNI); 153 (69 CNI-free, 84 CNI) were included in histological analyses. Fibrosis progression occurred in 46.2% (12/26) CNI-free EMT+ patients versus 51.6% (16/31) CNI EMT+ patients (p = 0.68). Biopsy-proven acute rejection (BPAR, including subclinical events) occurred in 25.0% and 5.1% of CNI-free and CNI patients, respectively (p < 0.001). In conclusion, early CNI withdrawal with everolimus initiation does not prevent interstitial fibrosis. Using this CNI-free protocol, in which everolimus exposure was relatively low and administered with half-dose EC-MPS, CNI-free patients were overwhelmingly under-immunosuppressed and experienced an increased risk of BPAR.

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.

Allograft rejection and tubulointerstitial fibrosis in human kidney allografts: interrogation by urinary cell mRNA profiling

Because the kidney allograft has the potential to function as an in-vivo flow cytometer and facilitate the access of immune cells and kidney parenchymal cells in to the urinary space, we hypothesized that mRNA profiling of urinary cells offers a noninvasive means of assessing the kidney allograft status. We overcame the inherent challenges of urinary cell mRNA profiling by developing pre-amplification protocols to compensate for low RNA yield from urinary cells and by developing robust protocols for absolute quantification mRNAs using RT-PCR assays. Armed with these tools, we undertook first single-center studies urinary cell mRNA profiling and then embarked on the multicenter Clinical Trials in Organ Transplantation-04 study of kidney transplant recipients. We report here our discovery and validation of diagnostic and prognostic biomarkers of acute cellular rejection and of interstitial fibrosis and tubular atrophy (IF/TA). Our urinary cell mRNA profiling studies, in addition to demonstrating the feasibility of accurate diagnosis of acute cellular rejection and IF/TA in the kidney allograft, advance mechanistic and potentially targetable biomarkers. Interventional trials, guided by urinary cell mRNA profiles, may lead to personalized immunosuppression in recipients of kidney allografts.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Opposite role of CD44-standard and CD44-variant-3 in tubular injury and development of renal fibrosis during chronic obstructive nephropathy

Chronic kidney diseases (CKDs) are characterized by tubular atrophy and interstitial fibrosis. We previously showed that in obstructive nephropathy de novo CD44 renal expression contributes to renal fibrosis but attenuates tubular damage/apoptosis. As CD44-standard (CD44s) has been linked to TGF-β1-mediated actions and CD44-variant-3 (CD44v3) favors HGF-c-Met binding, we compared the functional properties of these CD44 isoforms in the progression of obstructive nephropathy, using specific CD44-variant knockout/knockin mice. The presence of CD44v3 diminished tubular damage during obstructive nephropathy, decreased apoptosis, and increased proliferation of tubular epithelial cells, and prevented renal fibrosis development. In contrast, expression of CD44s led to increased tubular damage and tubular epithelial cell apoptosis, and more renal fibrosis. A relative increase in renal β-catenin expression, HGF production, and HGF/c-Met signaling, together with a relative inhibition of TGF-β1 downstream signaling and TGF-β type I receptor expression, was found in CD44v3 mice compared with CD44s littermates. In line with this, Wnt3a/HGF treatment of tubular cells resulted in higher β-catenin/p-AKT levels in CD44v3(+) tubular epithelial cells, whereas TGF-β1 induced a mild collagen I upregulation in CD44v3(+) mouse embryonic fibroblasts as compared with CD44s(+) cells. Thus, CD44s and CD44v3 exert opposite roles in the progression of obstructive nephropathy, with CD44v3-v10 being the protective isoform that delays evolution of the renal pathology.

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

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

CD44-deficiency attenuates the immunologic responses to LPS and delays the onset of endotoxic shock-induced renal inflammation and dysfunction

Acute kidney injury (AKI) is a common complication during systemic inflammatory response syndrome (SIRS), a potentially deadly clinical condition characterized by whole-body inflammatory state and organ dysfunction. CD44 is a ubiquitously expressed cell-surface transmembrane receptor with multiple functions in inflammatory processes, including sterile renal inflammation. The present study aimed to assess the role of CD44 in endotoxic shock-induced kidney inflammation and dysfunction by using CD44 KO and WT mice exposed intraperitoneally to LPS for 2, 4, and 24 hours . Upon LPS administration, CD44 expression in WT kidneys was augmented at all time-points. At 2 and 4 hours, CD44 KO animals showed a preserved renal function in comparison to WT mice. In absence of CD44, the pro-inflammatory cytokine levels in plasma and kidneys were lower, while renal expression of the anti-inflammatory cytokine IL-10 was higher. The cytokine levels were associated with decreased leukocyte influx and endothelial activation in CD44 KO kidneys. Furthermore, in vitro assays demonstrated a role of CD44 in enhancing macrophage cytokine responses to LPS and leukocyte migration. In conclusion, our study demonstrates that lack of CD44 impairs the early pro-inflammatory cytokine response to LPS, diminishes leukocyte migration/chemotaxis and endothelial activation, hence, delays endotoxic shock-induced AKI.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.

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

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

CD44v3-v10 reduces the profibrotic effects of TGF-β1 and attenuates tubular injury in the early stage of chronic obstructive nephropathy

CD44 family members are cell surface glycoproteins, which are expressed on tubular epithelial cells (TEC) solely upon kidney injury and are involved in renal fibrosis development. Renal interstitial fibrosis is the final manifestation of chronic kidney diseases and is regulated by a complex network of cytokines, including the profibrotic factor transforming growth factor-β1 (TGF-β1) and the two antifibrotic cytokines bone morphogenic protein-7 (BMP-7) and hepatocyte growth factor (HGF). The present study investigates the potential role of CD44 standard (CD44s) and CD44v3-v10 (CD44v3) isoforms as modulators of the balance between TGF-β1 and HGF/BMP-7. CD44s is the shortest and most common isoform. CD44v3-v10 (CD44v3) has heparan sulfate moieties, which enable the binding to HGF/BMP-7, and hence, might exert renoprotective effects. Using transgenic mice overexpressing either CD44s or CD44v3 specifically on proximal TEC, we found that in vitro the overexpression of CD44v3 on primary TEC renders cells less susceptible to TGF-β1 profibrotic actions and more sensitive to BMP-7 and HGF compared with TEC overexpressing CD44s. One day after unilateral ureteric obstruction, obstructed kidneys from CD44v3 transgenic mice showed less tubular damage and myofibroblasts accumulation, which was associated with decreased TGF-β1 signaling and increased BMP-7 synthesis and signaling compared with kidneys from wild-type and CD44s transgenic mice. These data suggest that CD44v3 plays a renoprotective role in early stage of chronic obstructive nephropathy.

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.

Assessing the responses of cellular proteins induced by hyaluronic acid-modified surfaces utilizing a mass spectrometry-based profiling system: over-expression of CD36, CD44, CDK9, and PP2A

The cell responses to biopolymer surface at the early adhesion stages can be critical for cell survival. The purpose of this research was to assess formation of hyaluronic acid (HA) biopolymer surface, the fibroblasts were used as an experimental model to evaluate the responses of cellular proteins induced by biopolymer materials using a mass spectrometry-based profiling system. Surfaces were covered by multi-walled carbon nanotubes (CNT), chitosan (CS), and HA to increase the surface area, enhance the adhesion of biopolymer and promote the rate of cell proliferation. The amount of adhered fibroblasts on CNT/CS/HA electrodes of quartz crystal microbalance (QCM) were greatly exceeded those on other surfaces that were consistent with cell-count technique. Moreover, analyzing differential protein expressions of adhered fibroblasts on those biopolymer surfaces by proteomic approaches identified CD36, CD44, PP2A, and CDK9 as key proteins. To validate the influences of those four proteins on adhesions of fibroblasts on biopolymers, the cells were blocked by antibodies of the proteins and the adhesions of cells on the tested biopolymer surfaces were examined using a QCM technique, flow cytometric analysis and morphological observations. The results of significantly decreasing the weights and densities of the blocked fibroblasts adhering to CNT/CS/HA surfaces were obtained, and validate those proteins found by proteomic approaches. Utilizing mass spectrometry-based proteomics to evaluate cell adhesions on biopolymers is proposed.

Monitoring tolerance and rejection in organ transplant recipients

To avoid toxic side effects caused by permanent immunosuppressive treatment, research in transplantation focuses on new treatment strategies inducing tolerance or allowing drug weaning. Implementing drug minimization into clinical routine can be only safely achieved when guided by biomarkers reflecting the individual immune reactivity. We review recently described biomarkers and assays allowing identification of patients suitable for drug weaning or at risk of rejection. However, the majority of described biomarkers and assays have not been validated in prospective clinical trials. Thus, collaborative efforts are needed to design and perform prospective multicenter trials to validate the identified biomarkers across different laboratories.