Christoph Roderburg

Micro‐RNA profiling reveals a role for miR‐29 in human and murine liver fibrosis

Liver fibrosis is orchestrated by a complex network of signaling pathways regulating the deposition of extracellular matrix proteins during fibrogenesis. MicroRNAs (miRNAs) represent a family of small noncoding RNAs controlling translation and transcription of many genes. Recently, miRNAs have been suggested to crucially modulate cellular processes in the liver such as hepatocarcinogenesis. However, their role in liver fibrosis is not well understood. We systematically analyzed the regulation of miRNAs in a mouse model of carbon tetrachloride–induced hepatic fibrogenesis (CCl4) by gene array analysis, which revealed a panel of miRNA that were specifically regulated in livers of mice undergoing hepatic fibrosis. Within those, all three members of the miR‐29‐family were significantly down‐regulated in livers of CCl4‐treated mice as well as in mice that underwent bile duct ligation. Specific regulation of miR‐29 members in murine fibrosis models correlated with lower expression of miR‐29 in livers from patients with advanced liver fibrosis. Moreover, patients with advanced liver cirrhosis showed significantly lower levels of miR‐29a in their serum when compared with healthy controls or patients with early fibrosis. On a cellular level, down‐regulation of miR‐29 in murine hepatic stellate cells (HSCs) was mediated by transforming growth factor beta (TGF‐β) as well as inflammatory signals, namely, lipopolysaccharide (LPS) and nuclear factor kappa B (NF‐κB). Furthermore, overexpression of miR‐29b in murine HSC resulted in down‐regulation of collagen expression. Conclusion: Our data indicate that miR‐29 mediates the regulation of liver fibrosis and is part of a signaling nexus involving TGF‐β‐ and NF‐κB–dependent down‐regulation of miR‐29 family members in HSC with subsequent up‐regulation of extracellular matrix genes. Thus they may represent targets for novel therapeutic strategies against hepatic fibrogenesis and also might evolve as biomarkers in the diagnosis of liver fibrosis. (HEPATOLOGY 2011.)

Tracheobronchial transplantation with a stem-cell-seeded bioartificial nanocomposite: a proof-of-concept study

BACKGROUND Tracheal tumours can be surgically resected but most are an inoperable size at the time of diagnosis; therefore, new therapeutic options are needed. We report the clinical transplantation of the tracheobronchial airway with a stem-cell-seeded bioartificial nanocomposite. METHODS A 36-year-old male patient, previously treated with debulking surgery and radiation therapy, presented with recurrent primary cancer of the distal trachea and main bronchi. After complete tumour resection, the airway was replaced with a tailored bioartificial nanocomposite previously seeded with autologous bone-marrow mononuclear cells via a bioreactor for 36 h. Postoperative granulocyte colony-stimulating factor filgrastim (10 μg/kg) and epoetin beta (40,000 UI) were given over 14 days. We undertook flow cytometry, scanning electron microscopy, confocal microscopy epigenetics, multiplex, miRNA, and gene expression analyses. FINDINGS We noted an extracellular matrix-like coating and proliferating cells including a CD105+ subpopulation in the scaffold after the reseeding and bioreactor process. There were no major complications, and the patient was asymptomatic and tumour free 5 months after transplantation. The bioartificial nanocomposite has patent anastomoses, lined with a vascularised neomucosa, and was partly covered by nearly healthy epithelium. Postoperatively, we detected a mobilisation of peripheral cells displaying increased mesenchymal stromal cell phenotype, and upregulation of epoetin receptors, antiapoptotic genes, and miR-34 and miR-449 biomarkers. These findings, together with increased levels of regenerative-associated plasma factors, strongly suggest stem-cell homing and cell-mediated wound repair, extracellular matrix remodelling, and neovascularisation of the graft. INTERPRETATION Tailor-made bioartificial scaffolds can be used to replace complex airway defects. The bioreactor reseeding process and pharmacological-induced site-specific and graft-specific regeneration and tissue protection are key factors for successful clinical outcome. FUNDING European Commission, Knut and Alice Wallenberg Foundation, Swedish Research Council, StratRegen, Vinnova Foundation, Radiumhemmet, Clinigene EU Network of Excellence, Swedish Cancer Society, Centre for Biosciences (The Live Cell imaging Unit), and UCL Business.

The fractalkine receptor CX3CR1 protects against liver fibrosis by controlling differentiation and survival of infiltrating hepatic monocytes

Chemokines modulate inflammatory responses that are prerequisites for organ fibrosis upon liver injury. Monocyte‐derived hepatic macrophages are critical for the development, maintenance, and resolution of hepatic fibrosis. The specific role of monocyte‐associated chemokine (C‐X3‐C motif) receptor 1 (CX3CR1) and its cognate ligand fractalkine [chemokine (C‐X3‐C motif) ligand 1)] in liver inflammation and fibrosis is currently unknown. We examined 169 patients with chronic liver diseases and 84 healthy controls; we found that CX3CL1 is significantly up‐regulated in the circulation upon disease progression, whereas CX3CR1 is down‐regulated intrahepatically in patients with advanced liver fibrosis or cirrhosis. To analyze the functional relevance of this pathway, two models of experimental liver fibrosis were applied to wild‐type (WT) and CX3CR1‐deficient mice. Fractalkine expression was induced upon liver injury in mice, primarily in hepatocytes and hepatic stellate cells. CX3CR1−/− animals developed greater hepatic fibrosis than WT animals with carbon tetrachloride–induced and bile duct ligation–induced fibrosis. CX3CR1−/− mice displayed significantly increased numbers of monocyte‐derived macrophages within the injured liver. Chimeric animals that underwent bone marrow transplantation revealed that CX3CR1 restricts hepatic fibrosis progression and monocyte accumulation through mechanisms exerted by infiltrating immune cells. In the absence of CX3CR1, intrahepatic monocytes develop preferentially into proinflammatory tumor necrosis factor–producing and inducible nitric oxide synthase–producing macrophages. CX3CR1 represents an essential survival signal for hepatic monocyte–derived macrophages by activating antiapoptotic bcl2 expression. Monocytes/macrophages lacking CX3CR1 undergo increased cell death after liver injury, which then perpetuates inflammation, promotes prolonged inflammatory monocyte infiltration into the liver, and results in enhanced liver fibrosis. Conclusion: CX3CR1 limits liver fibrosis in vivo by controlling the differentiation and survival of intrahepatic monocytes. The opposing regulation of CX3CR1 and fractalkine in patients suggests that pharmacological augmentation of this pathway may represent a possible therapeutic antifibrotic strategy. (HEPATOLOGY 2010;52:1769‐1782)

miR-199a-5p Is upregulated during fibrogenic response to tissue injury and mediates TGFbeta-induced lung fibroblast activation by targeting caveolin-1.

As miRNAs are associated with normal cellular processes, deregulation of miRNAs is thought to play a causative role in many complex diseases. Nevertheless, the precise contribution of miRNAs in fibrotic lung diseases, especially the idiopathic form (IPF), remains poorly understood. Given the poor response rate of IPF patients to current therapy, new insights into the pathogenic mechanisms controlling lung fibroblasts activation, the key cell type driving the fibrogenic process, are essential to develop new therapeutic strategies for this devastating disease. To identify miRNAs with potential roles in lung fibrogenesis, we performed a genome-wide assessment of miRNA expression in lungs from two different mouse strains known for their distinct susceptibility to develop lung fibrosis after bleomycin exposure. This led to the identification of miR-199a-5p as the best miRNA candidate associated with bleomycin response. Importantly, miR-199a-5p pulmonary expression was also significantly increased in IPF patients (94 IPF versus 83 controls). In particular, levels of miR-199a-5p were selectively increased in myofibroblasts from injured mouse lungs and fibroblastic foci, a histologic feature associated with IPF. Therefore, miR-199a-5p profibrotic effects were further investigated in cultured lung fibroblasts: miR-199a-5p expression was induced upon TGFβ exposure, and ectopic expression of miR-199a-5p was sufficient to promote the pathogenic activation of pulmonary fibroblasts including proliferation, migration, invasion, and differentiation into myofibroblasts. In addition, we demonstrated that miR-199a-5p is a key effector of TGFβ signaling in lung fibroblasts by regulating CAV1, a critical mediator of pulmonary fibrosis. Remarkably, aberrant expression of miR-199a-5p was also found in unilateral ureteral obstruction mouse model of kidney fibrosis, as well as in both bile duct ligation and CCl4-induced mouse models of liver fibrosis, suggesting that dysregulation of miR-199a-5p represents a general mechanism contributing to the fibrotic process. MiR-199a-5p thus behaves as a major regulator of tissue fibrosis with therapeutic potency to treat fibroproliferative diseases.

A positive feedback loop between RIP3 and JNK controls non-alcoholic steatohepatitis

Non‐alcoholic fatty liver disease (NAFLD) represents the most common liver disease in Western countries and often progresses to non‐alcoholic steatohepatitis (NASH) leading ultimately to liver fibrosis and liver cancer. The occurrence of hepatocyte cell death—so far characterized as hepatocyte apoptosis—represents a fundamental step from benign steatosis toward progressive steatohepatitis. In contrast, the function of RIP3‐dependent “necroptosis” in NASH and NASH‐induced fibrosis is currently unknown. We show that RIP3 is upregulated in human NASH and in a dietary mouse model of steatohepatitis. RIP3 mediates liver injury, inflammation, induction of hepatic progenitor cells/activated cholangiocytes, and liver fibrosis through a pathway suppressed by Caspase‐8. This function of RIP3 is mediated by a positive feedback loop involving activation of Jun‐(N)‐terminal Kinase (JNK). Furthermore, RIP3‐dependent JNK activation promotes the release of pro‐inflammatory mediators like MCP‐1, thereby attracting macrophages to the injured liver and further augmenting RIP3‐dependent signaling, cell death, and liver fibrosis. Thus, RIP3‐dependent necroptosis controls NASH‐induced liver fibrosis. This pathway might represent a novel and specific target for pharmacological strategies in patients with NASH.

RIP3, a kinase promoting necroptotic cell death, mediates adverse remodelling after myocardial infarction.

AIMS Programmed necrosis (necroptosis) represents a newly identified mechanism of cell death combining features of both apoptosis and necrosis. Like apoptosis, necroptosis is tightly regulated by distinct signalling pathways. A key regulatory role in programmed necrosis has been attributed to interactions of the receptor-interacting protein kinases, RIP1 and RIP3. However, the specific functional role of RIP3-dependent signalling and necroptosis in the heart is unknown. The aims of this study were thus to assess the significance of necroptosis and RIP3 in the context of myocardial ischaemia. METHODS AND RESULTS Immunoblots revealed strong expression of RIP3 in murine hearts, indicating potential functional significance of this protein in the myocardium. Consistent with a role in promoting necroptosis, adenoviral overexpression of RIP3 in neonatal rat cardiomyocytes and stimulation with TNF-α induced the formation of a complex of RIP1 and RIP3. Moreover, RIP3 overexpression was sufficient to induce necroptosis of cardiomyocytes. In vivo, cardiac expression of RIP3 was up-regulated upon myocardial infarction (MI). Conversely, mice deficient for RIP3 (RIP3(-/-)) showed a significantly better ejection fraction (45 ± 3.6 vs. 32 ± 4.4%, P < 0.05) and less hypertrophy in magnetic resonance imaging studies 30 days after experimental infarction due to left anterior descending coronary artery ligation. This was accompanied by a diminished inflammatory response of infarcted hearts and decreased generation of reactive oxygen species. CONCLUSION Here, we show that RIP3-dependent necroptosis modulates post-ischaemic adverse remodelling in a mouse model of MI. This novel signalling pathway may thus be an attractive target for future therapies that aim to limit the adverse consequences of myocardial ischaemia.

miR-133a mediates TGF-β-dependent derepression of collagen synthesis in hepatic stellate cells during liver fibrosis

BACKGROUND & AIMS miRNAs are novel regulators of organ fibrosis. miR-133a plays a role in cardiac and muscle remodeling, but its function in the liver is unclear. We therefore aimed at evaluating a possible function of miR-133a in hepatofibrogenesis. METHODS miR-133a levels were measured in whole liver samples from different murine hepatic fibrosis models and human liver tissue from patients with liver cirrhosis. The cell-specific regulation of miR-133a was assessed in FACS-sorted hepatic cell subpopulations. Murine and human primary hepatic stellate cells (HSC) were isolated and treated with different cytokines to evaluate upstream regulators of miR-133a. Moreover, GRX cells were transfected with synthetic miR-133a and the effect on extracellular matrix (ECM) gene regulation was assessed. Finally, miR-133a serum levels were measured in a cohort of patients with chronic liver diseases and correlated with disease progression. RESULTS Overall miR-133a expression levels were unchanged in whole RNA extracts from fibrotic murine and human livers. However, miR-133a was specifically downregulated in HSC during fibrogenesis. Treatment of primary murine and human HSC with transforming growth factor (TGF)-β resulted in a significant downregulation of miR-133a in these cells. In turn, overexpression of miR-133a in primary murine HSC led to decreased expression of collagens. In addition, miR-133a serum levels were increased in patients with chronic liver disease and indicated the presence and progression of liver cirrhosis. CONCLUSIONS Evidence is presented for a novel antifibrotic functional role of miR-133a in hepatofibrogenesis. miR-133a may thus represent a target for diagnostic and therapeutic strategies in liver fibrosis.

U6 is unsuitable for normalization of serum miRNA levels in patients with sepsis or liver fibrosis

MicroRNA (miRNA) levels in serum have recently emerged as potential novel biomarkers for various diseases. miRNAs are routinely measured by standard quantitative real-time PCR (qPCR); however, the high sensitivity of qPCR demands appropriate normalization to correct for nonbiological variation. Presently, RNU6B (U6) is used for data normalization of circulating miRNAs in many studies. However, it was suggested that serum levels of U6 themselves might differ between individuals. Therefore, no consensus has been reached on the best normalization strategy in ‘circulating miRNA’. We analyzed U6 levels as well as levels of spiked-in SV40-RNA in sera of 44 healthy volunteers, 203 intensive care unit patients and 64 patients with liver fibrosis. Levels of U6 demonstrated a high variability in sera of healthy donors, patients with critical illness and liver fibrosis. This high variability could also be confirmed in sera of mice after the cecal ligation and puncture procedure. Most importantly, levels of circulating U6 were significantly upregulated in sera of patients with critical illness and sepsis compared with controls and correlated with established markers of inflammation. In patients with liver fibrosis, U6 levels were significantly downregulated. In contrast, levels of spiked-in SV40 displayed a significantly higher stability both in human cohorts (healthy, critical illness, liver fibrosis) and in mice. Thus, we conclude that U6 levels in the serum are dysregulated in a disease-specific manner. Therefore, U6 should not be used for data normalization of circulating miRNAs in inflammatory diseases and previous studies using this approach should be interpreted with caution. Further studies are warranted to identify specific regulatory processes of U6 levels in sepsis and liver fibrosis.

Micro-RNA profiling in human serum reveals compartment-specific roles of miR-571 and miR-652 in liver cirrhosis.

Background and Aims Micro-RNAs (miRNAs) have recently emerged as crucial modulators of molecular processes involved in chronic liver diseases. The few miRNAs with previously proposed roles in liver cirrhosis were identified in screening approaches on liver parenchyma, mostly in rodent models. Therefore, in the present study we performed a systematic screening approach in order to identify miRNAs with altered levels in the serum of patients with chronic liver disease and liver cirrhosis. Methods We performed a systematic, array-based miRNA expression analysis on serum samples from patients with liver cirrhosis. In functional experiments we evaluated the relationship between alterations of miRNA serum levels and their role in distinct cellular compartments involved in hepatic cirrhosis. Results The array analysis and the subsequent confirmation by qPCR in a larger patient cohort identified significant alterations in serum levels of miR-513-3p, miR-571 and miR-652, three previously uncharacterized miRNAs, in patients with alcoholic or hepatitis C induced liver cirrhosis. Of these, miR-571 serum levels closely correlated with disease stages, thus revealing potential as a novel biomarker for hepatic cirrhosis. Further analysis revealed that up-regulation of miR-571 in serum reflected a concordant regulation in cirrhotic liver tissue. In isolated primary human liver cells, miR-571 was up-regulated in human hepatocytes and hepatic stellate cells in response to the pro-fibrogenic cytokine TGF-β. In contrast, alterations in serum levels of miR-652 were stage-independent, reflecting a concordant down-regulation of this miRNA in circulating monocytes of patients with liver cirrhosis, which was inducible by proinflammatory stimuli like bacterial lipopolysaccharide. Conclusion Alterations of miR571 and miR-652 serum levels in patients with chronic liver disease reflect their putative roles in the mediation of fibrogenic and inflammatory processes in distinct cellular compartments involved in the pathogenesis of liver cirrhosis.

Levels of circulating miR-133a are elevated in sepsis and predict mortality in critically ill patients.

Objective:Serum levels of microRNA have been proposed as biomarkers in various inflammatory diseases. However, up to now, their clinical relevance in critical illness and sepsis is unclear. Design:Single-center clinical study. Setting:Fourteen-bed medical ICU of the University Hospital Aachen, university laboratory research unit. Subjects and Patients:Experimental sepsis model in C57Bl/6 mice; 223 critically ill patients in comparison with 76 healthy volunteers. Interventions:We used the model of cecal pole ligation and puncture for induction of polymicrobial sepsis in mice and measured alterations in serum levels of six different microRNAs with a known function in inflammatory diseases upon induction of septic disease. These results from mice were translated into a large and well-characterized cohort of critically ill patients admitted to the medical ICU. Measurements and Main Results:Serum miR-133a was then measured in 223 critically ill patients (138 with sepsis and 85 without sepsis) and 76 controls and associated with disease severity, organ failure, and prognosis. Significant alterations of miR-133a, miR-150, miR-155, and miR-193b* were found in mice after cecal pole ligation and puncture–induced sepsis. Among all regulated microRNAs, miR-133a displayed the most prominent and concordant up-regulation in sepsis, and this microRNA was therefore chosen for further investigation in the human. Here, significantly elevated miR-133a levels were found in critically ill patients at ICU admission, when compared with healthy controls, especially in patients with sepsis. Correlation analyses revealed significant correlations of miR-133a with disease severity, classical markers of inflammation and bacterial infection, and organ failure. Strikingly, high miR-133a levels were predictive for an unfavorable prognosis and represented a strong independent predictor for both ICU and long-term mortality in critically ill patients. Conclusions:miR-133a serum levels were significantly elevated in critical illness and sepsis. High miR-133a levels were associated with the severity of disease and predicted an unfavorable outcome of critically ill patients.