Fabian Benz

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.

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.

Elevated miR-122 serum levels are an independent marker of liver injury in inflammatory diseases.

Serum concentrations of miR‐122 were proposed as a marker for various inflammatory diseases, but the mechanisms driving alterations in miR‐122 serum levels are unknown.

Circulating MicroRNAs as Biomarkers for Sepsis

Sepsis represents a major cause of lethality during intensive care unit (ICU) treatment. Pharmacological treatment strategies for sepsis are still limited and mainly based on the early initiation of antibiotic and supportive treatment. In this context, numerous clinical and serum based markers have been evaluated for the diagnosis, the severity, and the etiology of sepsis. However until now, few of these factors could be translated into clinical use. MicroRNAs (miRNAs) do not encode for proteins but regulate gene expression by inhibiting the translation or transcription of their target mRNAs. Recently it was demonstrated that miRNAs are released into the circulation and that the spectrum of circulating miRNAs might be altered during various pathologic conditions, such as inflammation, infection, and sepsis. By using array- and single PCR-based methods, a variety of deregulated miRNAs, including miR-25, miR-133a, miR-146, miR-150, and miR-223, were described in the context of sepsis. Some of the miRNAs correlated with the disease stage, as well as patients’ short and long term prognosis. Here, we summarize the current findings on the role of circulating miRNAs in the diagnosis and staging of sepsis in critically ill patients. We compare data from patients with findings from animal models and, finally, highlight the challenges and drawbacks that currently prevent the use of circulating miRNAs as biomarkers in clinical routine.

miR-30c and miR-193 are a part of the TGF-β-dependent regulatory network controlling extracellular matrix genes in liver fibrosis.

MicroRNAs (miRNAs) have recently emerged as novel regulators in liver fibrosis. miR‐30c and miR‐193 are involved in fibrotic remodeling processes and cancer development, respectively. This study aimed to explore the role of miR‐30c and miR‐193 in liver fibrosis.

The role of miRNAs in the regulation of inflammatory processes during hepatofibrogenesis

Liver cirrhosis represents the end stage of most chronic inflammatory liver diseases and is a major global health burden. Despite the enormous relevance of cirrhotic disease, pharmacological strategies for prevention or treatment of hepatic fibrosis are still limited, underlining the need to establish a better understanding of the molecular mechanisms underlying the pathogenesis of hepatic cirrhosis. Recently, miRNAs have emerged as a new class of RNAs that do not withhold the information to encode for proteins but regulate whole gene expression networks during different physiological and pathological processes. Various authors demonstrated that miRNA species are functionally involved in the regulation of chronic liver damage and development of liver cirrhosis in inflamed livers. Moreover, circulating miRNA patterns were suggested to serve as blood-based biomarkers indicating liver injury and progression to hepatic cirrhosis and cancer. Here we summarize current findings on a potential role of miRNAs in the cascade leading from liver inflammation to liver fibrosis and finally hepatocellular carcinoma. We compare data from animal models with findings on miRNAs dysregulated in human patients and finally highlight a potential use of miRNAs as biomarkers for liver injury, fibrosis and cancer.

RIPK1 Suppresses a TRAF2-Dependent Pathway to Liver Cancer

Receptor-interacting protein kinase 1 (RIPK1) represents an essential signaling node in cell death and inflammation. Ablation of Ripk1 in liver parenchymal cells (LPC) did not cause a spontaneous phenotype, but led to tumor necrosis factor (TNF)-dependent hepatocyte apoptosis and liver injury without affecting inducible nuclear factor κB (NF-κB) activation. Loss of Ripk1 induced the TNF-dependent proteasomal degradation of the E3-ligase, TNF receptor-associated factor 2 (TRAF2), in a kinase-independent manner, thereby activating caspase-8. Moreover, loss of both Ripk1 and Traf2 in LPC not only resulted in caspase-8 hyperactivation but also impaired NF-κB activation, promoting the spontaneous development of hepatocellular carcinoma. In line, low RIPK1 and TRAF2 expression in human HCCs was associated with an unfavorable prognosis, suggesting that RIPK1 collaborates with TRAF2 to inhibit murine and human hepatocarcinogenesis.

Circulating MicroRNA-223 Serum Levels Do Not Predict Sepsis or Survival in Patients with Critical Illness

Background and Aims. Dysregulation of miR-223 was recently linked to various diseases associated with systemic inflammatory responses such as type 2 diabetes, cancer, and bacterial infections. However, contradictory results are available on potential alterations of miR-223 serum levels during sepsis. We thus aimed to evaluate the diagnostic and prognostic value of miR-223 serum concentrations in patients with critical illness and sepsis. Methods. We used i.v. injection of lipopolysaccharide (LPS) as well as cecal pole ligation and puncture (CLP) for induction of polymicrobial sepsis in mice and measured alterations in serum levels of miR-223. These results from mice were translated into a large and well-characterized cohort of critically ill patients admitted to the medical intensive care unit (ICU). Finally, results from analysis in patients were correlated with clinical data and extensive sets of routine and experimental biomarkers. Results. Although LPS injection induced moderately elevated serum miR-223 levels in mice, no significant alterations in miR-223 serum levels were found in mice after CLP-induced sepsis. In accordance with these results from animal models, serum miR-223 levels did not differ between critically ill patients and healthy controls. However, ICU patients with more severe disease (APACHE-II score) showed moderately reduced circulating miR-223. Strikingly, no differences in miR-223 levels were found in critically ill patients with or without sepsis, and serum levels of miR-223 did not correlate with classical markers of inflammation or bacterial infection. Finally, low miR-223 serum levels were moderately associated with an unfavorable prognosis of patients during the ICU treatment but did not predict long-term mortality. Conclusion. Recent reports on alterations in miR-223 serum levels during sepsis revealed contradictory results, preventing a potential use of this miRNA in clinical routine. We clearly show that miR-223 serum levels do not reflect the presence of sepsis neither in mouse models nor in a large cohort of ICU patients and do not indicate clinical outcome of critically ill patients. Thus miR-223 serum levels should not be used as a biomarker in this setting.

Elevated levels of circulating osteopontin are associated with a poor survival after resection of cholangiocarcinoma

BACKGROUND & AIMS Cholangiocarcinoma (CCA) represents a primary hepatic malignancy with incidence and mortality rising globally. Surgical treatment has remained the only potentially curative treatment option, but it is still unclear which patients benefit most from extended liver surgery, highlighting the need for new pre-operative stratification strategies. Osteopontin is a secreted extracellular glyco-phosphoprotein that has been associated with inflammation, metabolic disorders and cancer. Here, we examined the potential of circulating osteopontin serum levels as a diagnostic or prognostic biomarker in patients with CCA undergoing extended liver surgery. METHODS Osteopontin expression levels were analysed in human and murine CCA tumour samples, using semi-quantitative reverse transcriptase PCR and immunohistochemistry. Osteopontin serum concentrations were measured by enzyme-linked immunosorbent assay in 107 patients with CCA undergoing elective tumour resection as well as 55 healthy controls. Results were correlated with clinical data. RESULTS Correlating with an upregulation in CCA tumour cells and the tumour stroma, serum levels of osteopontin were elevated in patients with cholangiocarcinoma compared to healthy controls and patients with primary sclerosing cholangitis. Importantly, pre- and postoperative elevations of osteopontin showed a striking association with poor postoperative survival. CONCLUSIONS Serum osteopontin concentrations represent a promising prognostic biomarker in patients resectable CCA which could help to guide preoperative treatment decisions and to identify patients that will particularly benefit from extended liver surgery. Lay summary: Extended liver surgery is the only potentially curative treatment for patients with cholangiocarcinoma (CCA/biliary cancer), but it is currently unclear which patients benefit most from surgery. Detecting serum levels of osteopontin - a specific secreted glycoprotein involved in multiple human diseases - in CCA patients might help to identify those patients that particularly benefit from tumour resection.

Serum Levels of TNF Receptor Ligands Are Dysregulated in Sepsis and Predict Mortality in Critically Ill Patients

Introduction TNF superfamily members, including TNF-related weak inducer of apoptosis (TWEAK) and Glucocorticoid-Induced TNFR-Related Protein Ligand (GITRL) have been described as serum based biomarkers for inflammatory and immune mediated diseases. However, up to now the role of TWEAK and GITRL has not been analyzed in critical illness and sepsis. Methods GITRL and TWEAK serum concentrations were measured in 121 critically ill patients (84 fulfilled with septic disease), in comparison to 50 healthy controls. Results were correlated with clinical data. Results Serum levels of TWEAK and GITRL were strongly decreased in critically ill patients compared with healthy controls. Concentrations of TWEAK (but not GITRL) were further decreased in patients with sepsis and correlated with routinely used markers of inflammation and bacterial infection such as C-reactive protein, procalcitonin and Interleukin-6. Notably, we failed to detect a correlation to other TNFR ligands such as TNF or APRIL. Finally, TWEAK levels of the upper quartile of the cohort were prognostic for mortality during ICU treatment. Conclusion TWEAK and GITRL levels were lower in intensive care unit medical patients. Levels of TWEAK were further decreased in septic patients, and alterations in TWEAK concentrations were linked to an unfavorable outcome. Together with recently published results on other TNFR ligands, these data indicate specific functions of the different TNFR ligands in septic diseases.