Hypothesis: epithelial-to-mesenchymal transition is a common cause of chronic allograft failure

Novel role for tumor suppressor gene, liver kinase B1, in epithelial-mesenchymal transition leading to chronic lung allograft dysfunction

Epithelial-mesenchymal transition (EMT) has been implicated to play a role in chronic lung allograft dysfunction (CLAD). Liver kinase B1 (LKB1), a tumor suppressor gene, can regulate EMT. However, its role in CLAD development following lung transplantation remains unknown. Using qRT-PCR, biopsies from lung transplant recipients with bronchiolitis obliterans syndrome (BOS) demonstrated significant downregulation of LKB1 (p = .0001), compared to stable biopsies. To determine the role of LKB1 in EMT development, we analyzed EMT in human bronchial epithelial cell line BEAS-2B. Knockdown of LKB1 by siRNA significantly dysregulated mesenchymal markers expression in BEAS-2B cells. Following incubation of human primary bronchial epithelial cell or BEAS-2B cells with exosomes isolated from BOS or stable lung transplant recipients, LKB1 expression was inhibited when incubated with BOS-exosome. Incubation with BOS-exosomes also decreased LKB1 expression and induced EMT markers in air-liquid interface culture method. Our results provide novel evidence that exosomes released from transplanted lungs undergoing chronic rejection are associated with inactivated tumor suppressor gene LKB1 and this loss induces EMT leading to the pathogenesis of CLAD following human lung transplantation.

Fully integrating pathophysiological insights in COPD: an updated working disease model to broaden therapeutic vision

Our starting point is that relatively new findings into the pathogenesis and pathophysiology of airway disease in smokers that lead to chronic obstructive pulmonary disease (COPD) need to be reassessed as a whole and integrated into "mainstream" thinking along with traditional concepts which have stood the test of time. Such a refining of the accepted disease paradigm is urgently needed as thinking on therapeutic targets is currently under active reconsideration. We feel that generalised airway wall "inflammation" is unduly over-emphasised, and highlight the patchy and variable nature of the pathology (with the core being airway remodelling). In addition, we present evidence for airway wall disease in smokers/COPD as including a hypocellular, hypovascular, destructive, fibrotic pathology, with a likely spectrum of epithelial-mesenchymal transition states as significant drivers of this remodelling. Furthermore, we present data from a number of research modalities and integrate this with the aetiology of lung cancer, the role of chronic airway luminal colonisation/infection by a specific group of "respiratory" bacteria in smokers (which results in luminal inflammation) and the central role for oxidative stress on the epithelium. We suggest translation of these insights into more focus on asymptomatic smokers and early COPD, with the potential for fresh preventive and therapeutic approaches.

Periostin: a novel tissue biomarker correlates with chronicity index and renal function in lupus nephritis patients

Lupus nephritis (LN) is one of the most serious complications in patients with systemic lupus erythematosus (SLE). At present, there is no specific biomarker with high sensitivity and renal pathology involvement in use in clinical practice. Periostin is an extracellular matrix protein involved in kidney development and kidney injury. We performed immunohistochemical analysis for periostin and routine staining of 42 kidney tissues from LN patients compared with controlled kidney tissues. Activity index, chronicity index and periostin staining were evaluated and scored by a renal pathologist. Periglomerular staining of periostin was the most predominant finding. Positive periostin staining was also observed in areas with fibrosis such as sclerosed glomeruli, interstitial fibrosis and fibrous vessels. Moreover, the tubules seemed to be the main location for periostin staining. There was a statistically different level of periostin staining score between patient and control tissues. Periostin staining score also correlated with the chronicity index score of renal pathology ( r = 0.594, p < 0.001). Periostin was also correlated with worsening renal outcomes including serum creatinine, blood urea nitrogen and estimated glomerular filtration rate (eGFR). Subgroup analysis within patients with low activity index score or low chronicity index score found that there was a statistical difference in serum creatinine and eGFR between groups with low and high periostin staining scores. We concluded that periostin staining score correlated with chronicity index score and renal function in patients with lupus nephritis.

Urine periostin as a biomarker of renal injury in chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) represents the main cause of renal allograft failure after transplantation. Noninvasive CAN testing is required. Periostin promotes the expression of a mesenchymal phenotype in renal tubules and is a promising urine biomarker for progressive renal injury. Information regarding periostin expression in the setting of CAN remains scarce.

METHODS

Subjects were recruited from our outpatient transplantation clinic. Random urine samples were collected from CAN patients (n = 24) and renal transplant patients with normal renal function (transplant controls, n = 18). Control samples were collected from healthy volunteers (n = 18) who had normal renal function. Urine periostin was measured by enzyme-linked immunosorbent assay.

RESULTS

The median urine periostin in CAN patients was significantly higher than in transplant and healthy controls (1.74 vs 0.00 vs 0.14 ng/mg creatinine, respectively; P < .001). Urine periostin enzyme-linked immunosorbent assay at a cutoff value of 0.152 ng/mg creatinine demonstrated the sensitivity, specificity, and accuracy for distinguishing CAN patients from transplant patients with normal renal function (91.7%, 77.8%, and 85.7%, respectively). In addition, urine periostin levels correlated directly with urine protein creatinine ratio (R = 0.566, P < .001) and serum creatinine (R = 0.522; P < .001), whereas inverse significant correlations were evidenced with estimated glomerular filtration rate (R = -0.431; P < .001).

CONCLUSION

The appearance of urine periostin in CAN patients but not in healthy and transplant controls underscores its value as a potential biomarker for chronic progressive renal injury in transplant recipients.

Renal dysfunction and intragraft proMMP9 activity in renal transplant recipients with interstitial fibrosis and tubular atrophy

Chronic renal allograft injury is reflected by interstitial fibrosis and tubular atrophy (IF/TA) and by the accumulation of extracellular matrix (ECM). Metalloproteinases (MMPs) are renal physiologic regulators of ECM degradation. Changes in MMPs expression or activity may disturb ECM turnover leading to glomerular scarring and worsening renal function. Our goal was to investigate intragraft MMP2 and MMP9 activities and their correlation with renal dysfunction. Plasma MMP2 and MMP9 activities were analyzed as noninvasive markers of renal allograft deterioration. Transplanted patients were biopsied and histopathologically characterized as IF/TA+ or IF/TA-. Renal function was evaluated by serum creatinine, glomerular filtration rate (GFR) estimated by Modification of Diet in Renal Disease equation and urinary protein/creatinine ratio. Kidney and plasma MMP2 and MMP9 activities were analyzed by zymography. A significant renal dysfunction was observed in IF/TA+ patients. Intragraft proMMP9 showed a significant higher activity in IF/TA+ than in IF/TA- samples and was inversely correlated with the GFR. Intragraft proMMP2 activity tended to increase in IF/TA+ samples, although no statistic significance was reached. Circulating proMMP2 and proMMP9 activities did not show significant differences between groups. Our data provide evidence that correlates intragraft proMMP9 activity with the fibrotic changes and renal dysfunction observed in IF/TA.

Isolation of fibroblasts and epithelial cells in bronchoalveolar lavage (BAL)

The long-term outcome of lung transplants is poor with 60%-70% of patients developing chronic rejection. Chronic rejection is manifested histologically by obliterative bronchiolitis with bronchiolitis obliterans syndrome (BOS), the clinical surrogate. Recent studies suggest that fibroblasts and epithelial cells present in bronchoalveolar lavage (BAL) may be a clinically relevant biomarker for BOS. The goal of this investigation was to develop a fast, repeatable method to individually isolate these low-frequency cell types. Fibroblasts and epithelial cells were isolated from BAL using attachment methods and the phenotype of the cells confirmed using immunostaining for vimentin (fibroblasts) and epithelial cell adhesion molecule (EpCAM, epithelial cells). Both fibroblasts and epithelial cells were isolated in every sample of BAL processed with the frequency of fibroblasts ranging from 0.03% to 0.48% and epithelial cells ranging from 0.05% to 1.5% of the total sample. Additional studies were performed using cytospins of cells after macrophages were depleted; cells exhibiting characteristics of both fibroblasts and epithelial cells were observed. The frequency of the cells of interest suggests that conventional methods of immunomagnetic isolation will not be effective in isolating these subpopulations. Finally, some of the low-frequency cells isolated via cytospin exhibit characteristics of epithelial to mesenchymal transition (which was not observed in plating incubations), indicating that the epithelial to mesenchymal cell transition fibroblasts may be nonadherent. In future studies, this technique and dataset may be of use to statistically correlate low-frequency cell type abundance to the onset and development of BOS.

Differentiated transplant derived airway epithelial cell cytokine secretion is not regulated by cyclosporine

Background

While lung transplantation is an increasingly utilized therapy for advanced lung diseases, chronic rejection in the form of Bronchiolitis Obliterans Syndrome (BOS) continues to result in significant allograft dysfunction and patient mortality. Despite correlation of clinical events with eventual development of BOS, the causative pathophysiology remains unknown. Airway epithelial cells within the region of inflammation and fibrosis associated with BOS may have a participatory role.

Methods

Transplant derived airway epithelial cells differentiated in air liquid interface culture were treated with IL-1β and/or cyclosporine, after which secretion of cytokines and growth factor and gene expression for markers of epithelial to mesenchymal transition were analyzed.

Results

Secretion of IL-6, IL-8, and TNF-α, but not TGF-β1, was increased by IL-1β stimulation. In contrast to previous studies using epithelial cells grown in submersion culture, treatment of differentiated cells in ALI culture with cyclosporine did not elicit cytokine or growth factor secretion, and did not alter IL-6, IL-8, or TNF-α production in response to IL-1β treatment. Neither IL-1β nor cyclosporine elicited expression of markers of the epithelial to mesenchymal transition E-cadherin, EDN-fibronectin, and α-smooth muscle actin.

Conclusion

Transplant derived differentiated airway epithelial cell IL-6, IL-8, and TNF-α secretion is not regulated by cyclosporine in vitro; these cells thus may participate in local inflammatory responses in the setting of immunosuppression. Further, treatment with IL-1β did not elicit gene expression of markers of epithelial to mesenchymal transition. These data present a model of differentiated airway epithelial cells that may be useful in understanding epithelial participation in airway inflammation and allograft rejection in lung transplantation.

Human islet-derived precursor cells can cycle between epithelial clusters and mesenchymal phenotypes

We showed previously that undifferentiated, proliferating human islet-derived precursor cells (hIPCs) are a type of mesenchymal stem/stromal cell (MSC) that can be induced by serum deprivation to form clusters and ultimately differentiate in vitro to endocrine cells. We also demonstrated that partially differentiated hIPC clusters, when implanted under the kidney capsules of mice, continued to differentiate in vivo into hormone-producing cells. However, we noted that not all hIPC preparations yielded insulin-secreting cells in vivo and that in some animals no hormone-expressing cells were found. This suggested that the implanted cells were not always irreversibly committed to further differentiation and may even de-differentiate to a mesenchymal phenotype. In this study, we show that human cells with a mesenchymal phenotype are indeed found in the grafts of mice implanted with hIPCs in epithelial cell clusters (ECCs), which are obtained after 4-day in vitro culture of hIPCs in serum-free medium (SFM); mesenchymal cells were predominant in some grafts. We could mimic the transition of ECCs to de-differentiated mesenchymal cells in vitro by exposure to foetal bovine serum (FBS) or mouse serums, and to a significantly lesser extent to human serum. In a complementary series of experiments, we show that mouse serum and FBS are more effective stimulants of mesenchymal hIPC migration than is human serum. We found that proliferation was not needed for the transition from ECCs to de-differentiated cells because mitomycin-treated hIPCs that could not proliferate underwent a similar transition. Lastly, we show that cells exhibiting a mesenchymal phenotype can be found in grafts of adult human islets in mice. We conclude that epithelial-to-mesenchymal transition (EMT) of cells in hIPC ECCs can occur following implantation in mice. This potential for EMT of human islets or differentiated precursor cells must be considered in strategies for cell replacement therapy for diabetes.

Expression of transforming growth factor-β1 and Smads in hepatic fibrosis induced by Schistosoma Japonica in mice

AIM: To investigate the expression of transforming growth factor-β1 (TGF-β1), Smad2/3, Smad4 and Smad7 in Schistosoma japonicum-fibrotic liver tissues and to explore the fibrogenic molecular mechanism.

METHODS: Eighty healthy ICR mice were randomly divided into model group and normal control group. The model mice were infected with cercaria of Schistosoma japonica. The mice in both groups were killed at the end of the 4^th, 6^th, 8^th and 12^th wk respectively, and their livers, spleens, and bodies were weighed. Liver tissues were taken for HE and scarlet staining. Tissue microarray was prepared and immunohistochemical staining was used to detect the expression of TGF-β1, Smad2/3, Smad4 and Smad7.

RESULTS: In comparison with those in the normal control group, the livers and spleens of model mice were heavier and liver/body ratio was higher (liver, 12 wk: 2.99 ± 0.28 g vs 1.83 ± 0.13 g; spleen, 12 wk: 0.87 ± 0.15 g vs 0.14 ± 0.02 g; liver/body ratio, 12 wk: 0.09 ± 0.01 vs 0.04 ± 0.00; all P < 0.01); the expression of TGF-β1 and Smad2/3 was significantly stronger in livers of the model mice (TGF-β1, 12 wk: 0.105 ± 0.008 vs 0.024 ± 0.002; Smad2/3, 12 wk: 0.094 ± 0.009 vs 0.003 ± 0.001, all P < 0.01), and the above indexes were positively correlated with the degrees of hepatic fibrosis (r = 0.635, 0.482, 0.646, 0.347, and 0.662, respectively; all P < 0.05). Smad4 was found increased in livers of the model mice, but its expression decreased with the development of hepatic fibrosis (4 wk: 0.075 ± 0.011 vs 0.023 ± 0.006, 6 wk: 0.043 ± 0.008 vs 0.010 ± 0.002, 8 wk: 0.038 ± 0.009 vs 0.003 ± 0.002, 12 wk: 0.028 ± 0.004 vs 0.013 ± 0.006, all P < 0.01). Smad7 expression heightened only at the 8^th wk.

CONCLUSION: TGF-β1 and Smad2/3 might play important roles in liver fibrogenesis and Smad4's effect might occur at early and middle stage of hepatic fibrosis.

Perspectives on endothelial-to-mesenchymal transition: potential contribution to vascular remodeling in chronic pulmonary hypertension

All forms of pulmonary hypertension are characterized by structural changes in pulmonary arteries. Increased numbers of cells expressing α-smooth muscle (α-SM) actin is a nearly universal finding in the remodeled artery. Traditionally, it was assumed that resident smooth muscle cells were the exclusive source of these newly appearing α-SM actin-expressing cells. However, rapidly emerging experimental evidence suggests other, alternative cellular sources of these cells. One possibility is that endothelial cells can transition into mesenchymal cells expressing α-SM actin and that this process contributes to the accumulation of SM-like cells in vascular pathologies. We review the evidence that endothelial-mesenchymal transition is an important contributor to cardiac and vascular development as well as to pathophysiological vascular remodeling. Recent work has provided evidence for the role of transforming growth factor-β, Wnt, and Notch signaling in this process. The potential roles of matrix metalloproteinases and serine proteases are also discussed. Importantly, endothelial-mesenchymal transition may be reversible. Thus insights into the mechanisms controlling endothelial-mesenchymal transition are relevant to vascular remodeling and are important as we consider new therapies aimed at reversing pulmonary vascular remodeling.

Risk factors for early epithelial to mesenchymal transition in renal grafts

Epithelial-to-mesenchymal transition (EMT) of tubular epithelial cells (TECs) may participate in the pathogenesis of renal fibrosis. We performed a prospective study of EMT markers in protocol biopsies obtained 3 months after engraftment from 56 patients who received deceased donor kidneys and who had stable renal function. The presence of EMT was examined, and quantified by immunohistochemical staining for vimentin and translocation of beta-catenin to the cytoplasm. EMT status was defined as the presence of EMT markers in > or = 10% of TECs. EMT features were virtually absent in implantation biopsies, whereas 41% of the grafts were EMT-positive in the absence of advanced chronic allograft nephropathy. Thirteen patients (23%) had borderline changes or acute rejection. EMT features were more frequent in these patients than in those with normal kidney grafts (vimentin expression, p = 0.003; beta-catenin translocation, p = 0.002). EMT in grafts corresponded with elevated serum creatinine of the donor before the recovery of kidney (p = 0.02) and longer cold ischemia time (p = 0.02). In contrast, the donor age had no influence on the expression of EMT markers. These results suggest that EMT is an early and frequent phenomenon in kidney transplants that could be triggered by immunological and/or ischemic tubular injury.

Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Modern pathogenetic concepts of liver fibrosis suggest stellate cells and TGF-beta as major players and therapeutic targets

Hepatic fibrosis is a scarring process that is associated with an increased and altered deposition of extracellular matrix in liver. At the cellular and molecular level, this progressive process is mainly characterized by cellular activation of hepatic stellate cells and aberrant activity of transforming growth factor-beta1 and its downstream cellular mediators. Although the cellular responses to this cytokine are complex, the signalling pathways of this pivotal cytokine during the fibrogenic response and its connection to other signal cascades are now understood in some detail. Based on the current advances in understanding the pleiotropic reactions during fibrogenesis, various inhibitors of transforming growth factor-beta were developed and are now being investigated as potential drug candidates in experimental models of hepatic injury. Although it is too early to favour one of these antagonists for the treatment of hepatic fibrogenesis in human, the experimental results obtained yet provide stimulatory impulses for the development of an effective treatment of choice in the not too distant future. The present review summarises the actual knowledge on the pathogenesis of hepatic fibrogenesis, the role of transforming growth factor-beta and its signalling pathways in promoting the fibrogenic response, and the therapeutic modalities that are presently in the spotlight of many investigations and are already on the way to take the plunge into clinical studies.

Matrix metalloproteinase 2 and basement membrane integrity: a unifying mechanism for progressive renal injury

Chronic kidney disease (CKD) and failure are problems of increasing importance. Regardless of the primary etiology, CKD is characterized by tubular atrophy, interstitial fibrosis, and glomerulosclerosis. It has been assumed that diminished matrix metalloproteinase (MMP) activity is responsible for the accumulation of the extracellular matrix (ECM) proteins and collagens that typify the fibrotic kidney. Here we demonstrate that transgenic renal proximal tubular epithelial expression of a specific enzyme, MMP-2, is sufficient to generate the entire spectrum of pathological and functional changes characteristic of human CKD. At the earliest point, MMP-2 leads to structural alterations in the tubular basement membrane, a process that triggers tubular epithelial-mesenchymal transition, with resultant tubular atrophy, fibrosis and renal failure. Inhibition of MMP-2, specifically in the early, prefibrotic stages of disease may offer an additional approach for treatment of these disabling disorders.