Circulating microRNAs: promising candidates serving as novel biomarkers of acute hepatitis

Trials and Tribulations of MicroRNA Therapeutics

The discovery of the link between microRNAs (miRNAs) and a myriad of human diseases, particularly various cancer types, has generated significant interest in exploring their potential as a novel class of drugs. This has led to substantial investments in interdisciplinary research fields such as biology, chemistry, and medical science for the development of miRNA-based therapies. Furthermore, the recent global success of SARS-CoV-2 mRNA vaccines against the COVID-19 pandemic has further revitalized interest in RNA-based immunotherapies, including miRNA-based approaches to cancer treatment. Consequently, RNA therapeutics have emerged as highly adaptable and modular options for cancer therapy. Moreover, advancements in RNA chemistry and delivery methods have been pivotal in shaping the landscape of RNA-based immunotherapy, including miRNA-based approaches. Consequently, the biotechnology and pharmaceutical industry has witnessed a resurgence of interest in incorporating RNA-based immunotherapies and miRNA therapeutics into their development programs. Despite substantial progress in preclinical research, the field of miRNA-based therapeutics remains in its early stages, with only a few progressing to clinical development, none reaching phase III clinical trials or being approved by the US Food and Drug Administration (FDA), and several facing termination due to toxicity issues. These setbacks highlight existing challenges that must be addressed for the broad clinical application of miRNA-based therapeutics. Key challenges include establishing miRNA sensitivity, specificity, and selectivity towards their intended targets, mitigating immunogenic reactions and off-target effects, developing enhanced methods for targeted delivery, and determining optimal dosing for therapeutic efficacy while minimizing side effects. Additionally, the limited understanding of the precise functions of miRNAs limits their clinical utilization. Moreover, for miRNAs to be viable for cancer treatment, they must be technically and economically feasible for the widespread adoption of RNA therapies. As a result, a thorough risk evaluation of miRNA therapeutics is crucial to minimize off-target effects, prevent overdosing, and address various other issues. Nevertheless, the therapeutic potential of miRNAs for various diseases is evident, and future investigations are essential to determine their applicability in clinical settings.

Circulating microRNAs as Potential Biomarkers in Pancreatic Cancer-Advances and Challenges

There is an urgent unmet need for robust and reliable biomarkers for early diagnosis, prognosis, and prediction of response to specific treatments of many aggressive and deadly cancers, such as pancreatic cancer, and liquid biopsy-based miRNA profiling has the potential for this. MiRNAs are a subset of non-coding RNAs that regulate the expression of a multitude of genes post-transcriptionally and thus are potential diagnostic, prognostic, and predictive biomarkers and have also emerged as potential therapeutics. Because miRNAs are involved in the post-transcriptional regulation of their target mRNAs via repressing gene expression, defects in miRNA biogenesis pathway and miRNA expression perturb the expression of a multitude of oncogenic or tumor-suppressive genes that are involved in the pathogenesis of various cancers. As such, numerous miRNAs have been identified to be downregulated or upregulated in many cancers, functioning as either oncomes or oncosuppressor miRs. Moreover, dysregulation of miRNA biogenesis pathways can also change miRNA expression and function in cancer. Profiling of dysregulated miRNAs in pancreatic cancer has been shown to correlate with disease diagnosis, indicate optimal treatment options and predict response to a specific therapy. Specific miRNA signatures can track the stages of pancreatic cancer and hold potential as diagnostic, prognostic, and predictive markers, as well as therapeutics such as miRNA mimics and miRNA inhibitors (antagomirs). Furthermore, identified specific miRNAs and genes they regulate in pancreatic cancer along with downstream pathways can be used as potential therapeutic targets. However, a limited understanding and validation of the specific roles of miRNAs, lack of tissue specificity, methodological, technical, or analytical reproducibility, harmonization of miRNA isolation and quantification methods, the use of standard operating procedures, and the availability of automated and standardized assays to improve reproducibility between independent studies limit bench-to-bedside translation of the miRNA biomarkers for clinical applications. Here I review recent findings on miRNAs in pancreatic cancer pathogenesis and their potential as diagnostic, prognostic, and predictive markers.

MicroRNA in medication related osteonecrosis of the jaw: a review

Medication related osteonecrosis of the jaw (MRONJ) is a condition caused by inhibition of the osteoclast activity by the anti-resorptive and anti-angiogenic drugs. Clinically, there is an exposure of the necrotic bone or a fistula which fails to heal for more than 8 weeks. The adjacent soft tissue is inflamed and pus may be present as a result of the secondary infection. To date, there is no consistent biomarker that could aid in the diagnosis of the disease. The aim of this review was to explore the literature on the microRNAs (miRNAs) related to medication related osteonecrosis of the jaw, and to describe the role of each miRNA as a biomarker for diagnostic purpose and others. Its role in therapeutics was also searched. It was shown that miR-21, miR-23a, and miR-145 were significantly different in a study involving multiple myeloma patients as well as in a human-animal study while miR-23a-3p and miR-23b-3p were 12- to 14-fold upregulated compared to the control group in an animal study. The role of the microRNAs in these studies were for diagnostics, predictor of progress of MRONJ and pathogenesis. Apart from its potential diagnostics role, microRNAs have been shown to be bone resorption regulator through miR-21, miR-23a and miR-145 and this could be utilized therapeutically.

Anti-microRNA-1976 as a Novel Approach to Enhance Chemosensitivity in XAF1+ Pancreatic and Liver Cancer

The current cancer treatments using chemoagents are not satisfactory in terms of outcomes and prognosis. Chemoagent treatments result in cell death or arrest, but the accompanying cellular responses are not well-studied. Exosomes, which are extracellular vesicles secreted by living cells, might mediate cellular responses through microRNAs. We found that miR-1976 was highly enriched in exosomes secreted after chemoagent treatment. We developed a novel approach for in situ mRNA target screening and discovered several miR-1976-specific mRNA targets, including the proapoptotic gene XAF1, which was targeted by miR-1976 and which suppressed chemoagent-induced cell apoptosis. Increased RPS6KA1 gene transcription was associated with the increase in its intronic pre-miR-1976 expression. Blockade of miR-1976 could enhance chemosensitivities of hepatoma and pancreatic cancer cells in an XAF1-dependent manner, as evidenced by increased levels of cell apoptosis, reduced IC50 in cell toxicity assays, and suppressed tumor growth in animal xenograft experiments in vivo. We propose that intracellular levels of miR-1976 determine chemosensitivity, and its blockade could be a novel strategy and potential therapeutic application in cancer treatment.

The Role of miRNAs in Extracellular Matrix Repair and Chronic Fibrotic Lung Diseases

The lung extracellular matrix (ECM) plays a key role in the normal architecture of the lung, from embryonic lung development to mechanical stability and elastic recoil of the breathing adult lung. The lung ECM can modulate the biophysical environment of cells through ECM stiffness, porosity, topography and insolubility. In a reciprocal interaction, lung ECM dynamics result from the synthesis, degradation and organization of ECM components by the surrounding structural and immune cells. Repeated lung injury and repair can trigger a vicious cycle of aberrant ECM protein deposition, accompanied by elevated ECM stiffness, which has a lasting effect on cell and tissue function. The processes governing the resolution of injury repair are regulated by several pathways; however, in chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary disease (IPF) these processes are compromised, resulting in impaired cell function and ECM remodeling. Current estimates show that more than 60% of the human coding transcripts are regulated by miRNAs. miRNAs are small non-coding RNAs that regulate gene expressions and modulate cellular functions. This review is focused on the current knowledge of miRNAs in regulating ECM synthesis, degradation and topography by cells and their dysregulation in asthma, COPD and IPF.

Sensitivity of glutathione S-transferases to high doses of acrylamide in albino wistar rats: Affinity purification, biochemical characterization and expression analysis

The main objectives of this study were to purify the glutathione S-transfereses (GSTs) and assess the effect of high doses of acrylamide (ACR) on male albino Wistar rat liver, kidney, testis and bran GST activities, and expression analysis of GST. ACR (50 mg/300 ml) was ingested for 40 days (20 doses) in drinking water on alternative days, on 40 day post ingestion the control and treated tissues were collected for GST purification by affinity column and biochemical characterization of GSTs by substrate specificities, and GST expression by immuno dot blots. In the analysis of the purified GSTs, we observed that liver GSTs were resolved in to three bands known as Yc, Yb and Ya; kidney GSTs were resolved in to two bands known as Yc and Ya; testis and brain GSTs were resolved as four bands known as Yc, Yb, Yβ and Yδ on 12.5% sodium dodecyl sulfate polyacrylamide gel (SDS PAGE). In the analysis of biochemical characterization, we observed a significant decrease (p < 0.05) in the specific activities of liver GST isoforms with the substrates 1-chloro 2,4-dinitrobenzene (CDNB), bromosulfophthalein (BSP), p-nitrophenyl acetate (pNPA), p-nitrobenzyl chloride (pNBC) and cumene hydroperoxide (CHP), but showed no activity with ethacrynic acid (ECA) and significant decrease (p < 0.05) in the specific activities of kidney GST isoforms with the substrates CDNB, pNPA, pNBC and CHP, but showed no activity with BSP and ECA, and a significant decrease (p < 0.05) in the specific activities of testis and brain GST isoforms with the substrates CDNB, BSP, pNPA, pNBC, ECA and CHP. In the analysis of immuno dot blots, we observed a decreased expression of liver, kidney, testis and brain GSTs. Through the affinity purification and biochemical characterization, we observed a tissue specific distribution of GSTs that is liver GSTs possess Yc, Yb and Ya sub units known as alpha (α) and mu (μ) class GSTs; kidney GSTs possess Yc and Ya sub units known as (α) alpha class GST; testis and brain GSTs possess Yc, Yb, Yβ and Yδ sub units known as alpha (α), mu (μ) and pi (π) class GSTs. Purification studies, biochemical characterization and immuno dot blot analysis were revealed the GSTs were sensitive to high doses of ACR and the high level exposure to ACR cause the damage of detoxification function of GST due to decreased expression and hence lead to cellular dysfunction of vital organs.

The Potential for microRNA Therapeutics and Clinical Research

As FDA-approved small RNA drugs start to enter clinical medicine, ongoing studies for the microRNA (miRNA) class of small RNAs expand its preclinical and clinical research applications. A growing number of reports suggest a significant utility of miRNAs as biomarkers for pathogenic conditions, modulators of drug resistance, and/or as drugs for medical intervention in almost all human health conditions. The pleiotropic nature of this class of nonprotein-coding RNAs makes them particularly attractive drug targets for diseases with a multifactorial origin and no current effective treatments. As candidate miRNAs begin to proceed toward initiation and completion of potential phase 3 and 4 trials in the future, the landscape of both diagnostic and interventional medicine will arguably continue to evolve. In this mini-review, we discuss miRNA drug discovery development and their current status in clinical trials.

Identification of suitable reference microRNA for qPCR analysis in pediatric inflammatory bowel disease

Pediatric inflammatory bowel disease (IBD) accounts for 10-15% of IBD and is associated with considerable morbidity for patients. Dysregulated microRNAs (miRNA, miR), small noncoding RNA molecules that modulate gene expression, have been the target of research in IBD diagnosis, surveillance, and therapy. Proper selection of reference genes, which are a prerequisite for accurate measurement of miRNA expression, is currently lacking. We hypothesize that appropriate normalization requires unique reference genes for different tissue and disease types. Through the study of 28 pediatric intestinal samples, we sought to create a protocol for selection of suitable endogenous reference genes. Candidate reference genes (miR-16, 193a, 27a, 103a, 191) were analyzed by RT-quantitative (q)PCR. Criteria used for designation of suitable reference genes were as follows: 1) ubiquitous: present in all tissue samples with quantification cycle value 15-35; 2) uniform expression: no differential expression between control and disease samples (P > 0.05); 3) stability: stability value <0.5 by NormFinder. Our results suggest the use of miR-27a/191 for Crohn's disease small bowel, none of the five candidate genes for Crohn's disease colon, and miR-16/27a for ulcerative colitis. Additionally, target miR-874 had differential expression when normalized with different reference genes. Our results demonstrate that reference gene choice for qPCR analysis has a significant effect on study results and that proper data normalization is imperative.

Computational identification of microRNAs and their targets in liver cirrhosis

Previous studies have revealed that the deregulation of circulating miRNAs is associated with liver cirrhosis. The present study aimed to identify reliable candidate biomarkers to improve the early detection of liver cirrhosis. An integrated analysis of expression profiles of microRNAs (miRNAs/miRs) and mRNAs in liver cirrhosis tissues from the GEO database was performed. Next, the regulatory targets of the differentially expressed miRNAs in liver cirrhosis tissues were predicted. In addition, a regulatory network of miRNA-target genes was constructed. A total of 4 eligible mRNA expression profiling studies and 2 miRNA expression profiling studies met the inclusion criteria, and were thus included. A total of 48 differentially expressed miRNAs and 1,773 differentially expressed genes were identified in liver cirrhosis tissues compared with normal tissues. There were 240 miRNA-target pairs whose expression was negatively correlated. In the miRNA-target regulatory network, overexpression of miR-21 and miR-199a-3p was suggested to be closely associated with the progression of liver cirrhosis. In addition, functional enrichment analysis of the target genes indicated that cell cycle was the most significantly enriched pathway, and the dysregulation of leukemia inhibitory factor, cancerous inhibitor of protein phosphatase 2A and retinoblastoma-associated protein 1 clearly suggested their importance in the development of liver cirrhosis. We hypothesized that miR-21 and miR-199a-3p may be promising non-invasive diagnostic biomarkers for the early diagnosis of liver cirrhosis. The miRNA-target regulatory network may provide additional insight into the current data regarding the role of miRNAs in liver cirrhosis.

Serum and exosomal miR-122 and miR-199a as a biomarker to predict therapeutic efficacy of hepatitis C patients

MicroRNA (miRNA), which has been shown to correlate with liver functions, has been proposed as a new biomarker reflecting liver injury. The aim of the study was to investigate miRNA-122 (miR-122) and mir-RNA-199a (miR-199a) as a biomarker for predicting therapeutic efficacy in hepatitis C (HepC) patients. A total of 47 HepC 1b patients and 16 healthy subjects were enrolled in the study. Serum and exosomal mir-RNAs and other conventional biomarkers reflecting liver function were evaluated. The miR-122 levels in serum (miR-122_ser ) and exosomes (miR-122_exo ) were significantly lower in the Hepatitis C virus (HCV) genotype 1b patients than in the normal controls, but these levels were higher compared to the non-genotype 1b group. The mean miR-122_ser level in the sustained virological response (SVR) group was significantly higher than that in the non-response (NR) group (P < 0.01), and the miR-122_exo level in the SVR group was also higher than that in the NR group (P > 0.05), although this difference was not significant. miR-199a levels showed similar trends with the miR-122 levels in serum and exosomes. HCV RNA_ser was negatively correlated with the miR-122_ser (r = -0.473, P = 0.004) and miR-122_exo (r = -0.424, P = 0.009) levels. miR-122_ser levels were positively associated with miR-199a_ser levels (r = 0.453, P = 0.002)_. Univariate and multivariate regression analyses reveal that the miR-122_ser levels and ALT/AST ratio demonstrated a predictive value in evaluating patient outcomes. Serum miR-122 and miR-199a are potential biomarkers that reflect therapeutic efficacy.

慢加急性肝衰竭: 东西方诊断和预后的差异

慢加急性肝衰竭(acute-on-chronic liver failure, ACLF)是以慢性肝病基础上发生的急性肝功能失代偿和短期高死亡率为主要临床特征的一种可逆的、复杂的临床综合征. 由于不同区域ACLF的病因不同, 且病理机制复杂, 导致东西方对ACLF的定义及诊断标准仍存在争议, 且缺乏公认的预后评估体系. 近年来, ACLF引起了国内外学者的广泛关注, 取得了一些重要的研究进展, 本文将围绕国际上ACLF的最新进展, 对ACLF的定义及预后评估等进行分析总结.

Profiles of miRNAs in serum in severe acute drug induced liver injury and their prognostic significance

BACKGROUND & AIMS

Drug induced liver injury (DILI) is challenging because of the lack of biomarkers to predict mortality. Our aim was to describe miRNA changes in sera of subjects with acute idiosyncratic DILI and determine if levels of miRNAs were associated with 6 month mortality.

METHODS

Clinical data and sera were collected from subjects enrolled in the Drug Induced Liver Injury Network prospective study. miRNAs were isolated from serum obtained from 78 subjects within 2 weeks of acute DILI and followed up for 6 months or longer. miRNAs were compared to 40 normal controls and 6 month survivors vs non-survivors.

RESULTS

The mean age of the DILI cohort was 48 years, and 55% were female. Eleven (14.1%) subjects died, 10 within 6 months of DILI onset, 5 (45%) liver related. Lower levels of miRNAs-122, -4463 and -4270 were associated with death within 6 months (P<.05). None of the subjects with miRNA-122 greater than the median value died within 6 months for a sensitivity of 100% and specificity of 57%. In subjects with a serum albumin <2.8 g/dL and miR-122<7.89 RFU the sensitivity, specificity, positive and negative predictive values for death within 6 months were 100%, 57%, 38% and 100% respectively.

CONCLUSIONS

Serum miRNA-122 combined with albumin accurately identified subjects who died within 6 months of drug induced liver injury. If confirmed prospectively, miRNA-122 and albumin may be useful in identifying patients at high risk for mortality or liver transplantation.

Exosomes as miRNA Carriers: Formation-Function-Future

Exosomes, which are one of the smallest extracellular vesicles released from cells, have been shown to carry different nucleic acids, including microRNAs (miRNAs). miRNAs significantly regulate cell growth and metabolism by posttranscriptional inhibition of gene expression. The rapidly changing understanding of exosomes’ formation and function in delivering miRNAs from cell to cell has prompted us to review current knowledge in exosomal miRNA secretion mechanisms as well as possible therapeutic applications for personalized medicine.

Human Ex-Vivo Liver Model for Acetaminophen-induced Liver Damage

Reliable test systems to identify hepatotoxicity are essential to predict unexpected drug-related liver injury. Here we present a human ex-vivo liver model to investigate acetaminophen-induced liver injury. Human liver tissue was perfused over a 30 hour period with hourly sampling from the perfusate for measurement of general metabolism and clinical parameters. Liver function was assessed by clearance of indocyanine green (ICG) at 4, 20 and 28 hours. Six pieces of untreated human liver specimen maintained stable liver function over the entire perfusion period. Three liver sections incubated with low-dose acetaminophen revealed strong damage, with ICG half-lives significantly higher than in non-treated livers. In addition, the release of microRNA-122 was significantly higher in acetaminophen-treated than in non-treated livers. Thus, this model allows for investigation of hepatotoxicity in human liver tissue upon applying drug concentrations relevant in patients.

Circulating Extracellular RNA Markers of Liver Regeneration

BACKGROUND AND AIMS

Although a key determinant of hepatic recovery after injury is active liver regeneration, the ability to detect ongoing regeneration is lacking. The restoration of liver mass after hepatectomy involves systemic changes with coordinated changes in gene expression guiding regenerative responses, activation of progenitor cells, and proliferation of quiescent hepatocytes. We postulated that these responses involve intercellular communication involving extracellular RNA and that these could represent biomarkers of active regenerative responses.

METHODS

RNA sequencing was performed to identify temporal changes in serum extracellular non-coding RNA after partial hepatectomy in C57BL/6 male mice. Tissue expression of selected RNA was performed by microarray analysis and validated using qRT-PCR. Digital PCR was used to detect and quantify serum expression of selected RNA.

RESULTS

A peak increase in extracellular RNA content occurred six hours after hepatectomy. RNA sequencing identified alterations in several small non-coding RNA including known and novel microRNAs, snoRNAs, tRNA, antisense and repeat elements after partial hepatectomy. Combinatorial effects and network analyses identified signal regulation, protein complex assembly, and signal transduction as the most common biological processes targeted by miRNA that altered. miR-1A and miR-181 were most significantly altered microRNA in both serum and in hepatic tissues, and their presence in serum was quantitated using digital PCR.

CONCLUSIONS

Extracellular RNA selectively enriched during acute regeneration can be detected within serum and represent biomarkers of ongoing liver regeneration in mice. The ability to detect ongoing active regeneration would improve the assessment of hepatic recovery from liver injury.

Micro RNAs mir-106a, mir-122 and mir-197 are increased in severe acute viral hepatitis with coagulopathy

BACKGROUND & AIMS

The severity of acute viral hepatitis, which may be caused by several distinct viruses, varies among individual patients. In rare cases, severe hepatic injury with sudden loss of liver function may occur, which is clinically indicated by the occurrence of coagulopathy or encephalopathy. As the molecular mechanisms of this liver injury are largely unknown, we investigated extracellular micro RNA (miRNA) profiles in 54 patients acutely infected with one of four different hepatotropic viruses, in order to identify those miRNAs which indicate severe viral hepatitis associated with coagulopathy.

METHODS

First, the profile of miRNAs was extensively analysed using a microarray-based approach in highly characterized 24 patients, matched in terms of sex, age and level of liver enzymes, as well as in three healthy controls. The cohort included samples from 18 patients with moderate and six individuals with severe hepatitis, indicated by abnormal prothrombin time and higher alanine aminotransferase and bilirubin levels. miRNAs found to be upregulated in severe hepatitis were then quantified by real-time PCR in the expanded cohort of 54 patients.

RESULTS

Comprehensive microarray-based miRNA profiling identified upregulation of mir-106a, mir-122 and mir-197 in patients with severe acute viral hepatitis with coagulopathy, as compared to patients who did not develop coagulopathy. mir-106a, mir-122 and mir-197 were then proven to be significantly upregulated in patients with severe acute viral hepatitis by quantitative real-time PCR (P < 0.01, Mann-Whitney U-test).

CONCLUSIONS

mir-106a, mir-122 and mir-197 could be potential markers for severe acute viral hepatitis associated with coagulopathy.

Expression of microRNAs differed in the omental adipose tissue of obese rats

OBJECTIVE

To establish obese rat models by high-fat diet, screen microRNAs by microarray in the omental adipose tissue, and find out differential expression of microRNAs in obese rats, for further understanding the role of microRNAs as regulating molecules in obesity-induced lipid metabolism disorders.

METHODS

40 male SD rats were randomly divided into normal diet group and high-fat diet group, respectively. After fed for 8 weeks, rats were weighted, measured length and other characteristics were observed. Eye blood was taken to test blood glucose level, blood lipids level, insulin level and other indicators. The omental adipose tissue was measured by electronic analytical scales and saved at -80°C liquid nitrogen. Fat cells were stained by oil red to observe their morphology under microscopy. The expression of microRNAs was screened by microarray, and verified by Real-Time PCR.

RESULTS

After high-fat diet for 4 and 8 weeks, some fatty indicators changed, including increased body weight, omental fat weight, triglycerides, total cholesterol, low-density lipoprotein, blood glucose level and insulin level, and decreased high-density lipoprotein, and differential phenotype of fat cells. Besides, by microarray techniques and Real-Time PCR, 13 differential expression microRNAs were identified, including 7 up-regulated microRNAs (microRNA30a, microRNA7e, microRNA30c, microRNA335, microRNA103, microRNA107, microRNA139-5p), and 6 down-regulated microRNAs (microRNA494, microRNA140, microRNA342-5p, microRNA382, microRNA17-1-3p, microRNA92a).

CONCLUSION

Changes in the expression of microRNAs contribute to the pathogenesis of many diseases, including obesity disorders. These alterations can be due to various mechanisms, such as cell proliferation, apoptosis, migration, and differentiation, providing new therapies for diseases.

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

BACKGROUND & AIMS

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.

METHODS

We analysed miR-122 serum levels and hepatic miR-122 expression in mice after hepatic ischaemia and reperfusion (I/R) injury. These data were compared with data from mice after caecal pole ligation and puncture (CLP) procedure. To translate these data into the human, we analysed miR-122 serum concentrations in a cohort of 223 patients with critical illness and 57 patients with cirrhosis.

RESULTS

We detected strongly elevated levels of miR-122 in mice after hepatic I/R injury. miR-122-concentrations correlated with the degree of liver damage according to AST/ALT and were associated with the presence of hepatic cell death detected by TUNEL staining. miR-122 levels were elevated in the cellular supernatants in an in vitro model of hepatocyte injury, supporting the hypothesis that the passive release of miR-122 represents a surrogate for hepatocyte death in liver injury. Moreover, miR-122 levels were almost normal in patients with cirrhosis without ongoing liver damage, but were elevated when liver injury was present. In contrast to previous assumptions, miR-122-concentrations were independent of the presence of infection/sepsis in mice or human patients. miR-122 levels did not correlate with disease severity or mortality in critically ill patients. In contrast, serum miR-122 levels strictly correlated with the presence of hepatic injury in these patients.

CONCLUSION

In mice and humans, miR-122 levels represent an independent and potent marker of ongoing liver injury and hepatic cell death regardless of the underlying disease.

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.

Serum microRNA-124 is a novel biomarker for liver necroinflammation in patients with chronic hepatitis B virus infection

Patients with chronic hepatitis B virus (HBV) infection and normal or mildly increased transaminases may have sustained significant liver damage, as verified by liver biopsy. However, no suitable noninvasive method exists for identifying liver necroinflammation in such patients. We aimed to investigate the power of microRNA-124 as a novel biomarker for liver necroinflammation. A total of 131 recruited patients with chronic HBV infection underwent liver biopsy for grading of necroinflammation (G) and staging of fibrosis (S). Thirty healthy individuals were included as controls (HCs). Serum microRNA-124 and microRNA-122 levels were measured using qRT-PCR. Forty-five patients from the study population receiving entecavir therapy were monitored for changes in serum microRNA-124 levels in association with improved liver histology. The capacity of serum microRNA-124 levels in discriminating the grade of liver necroinflammation was compared with alanine aminotransferase (ALT) with liver biopsy validation. Serum microRNA-124 levels were significantly higher in patients with chronic HBV infection than in HCs (P < 0.0001). Patients with considerable liver necroinflammation (G ≥ 2) had significantly higher serum miRNA-124 levels than those without or with mild necroinflammation (P < 0.0001). After 48 weeks of antiviral therapy, serum microRNA-124 levels considerably declined in 45 patients (P < 0.0001), which were associated with histological improvement. In patients with normal ALT and a serum HBV DNA load >10(4) copies/mL, receiver operating characteristic (ROC) curve of serum microRNA-124 levels yielded an area under ROC curve (AUC) of 0.840, with 58.3% sensitivity and 91.7% specificity in discriminating between moderate-to-severe liver necroinflammation (G ≥ 2).

MicroRNAs in alcoholic liver disease

Alcoholic liver disease (ALD) is characterized by hepatocyte damage, inflammatory cell activation and increased intestinal permeability leading to the clinical manifestations of alcoholic hepatitis. Selected members of the family of microRNAs are affected by alcohol, resulting in an abnormal miRNA profile in the liver and circulation in ALD. Increasing evidence suggests that mRNAs that regulate inflammation, lipid metabolism and promote cancer are affected by excessive alcohol administration in mouse models of ALD. This communication highlights recent findings in miRNA expression and functions as they relate to the pathogenesis of ALD. The cell-specific distribution of miRNAs, as well as the significance of circulating extracellular miRNAs, is discussed as potential biomarkers. Finally, the prospects of miRNA-based therapies are evaluated in ALD.

MicroRNAs in alcoholic liver disease

Alcoholic liver disease (ALD) is characterized by hepatocyte damage, inflammatory cell activation and increased intestinal permeability leading to the clinical manifestations of alcoholic hepatitis. Selected members of the family of microRNAs are affected by alcohol, resulting in an abnormal miRNA profile in the liver and circulation in ALD. Increasing evidence suggests that mRNAs that regulate inflammation, lipid metabolism and promote cancer are affected by excessive alcohol administration in mouse models of ALD. This communication highlights recent findings in miRNA expression and functions as they relate to the pathogenesis of ALD. The cell-specific distribution of miRNAs, as well as the significance of circulating extracellular miRNAs, is discussed as potential biomarkers. Finally, the prospects of miRNA-based therapies are evaluated in ALD.

Circulating microRNAs as a marker for liver injury in human immunodeficiency virus patients

Human immunodeficiency virus (HIV) and hepatitis virus coinfection amplify and accelerate hepatic injury. MicroRNAs (miRNAs) are small regulatory RNAs suggested as biomarkers for liver injury. We analyzed the circulating levels of miRNAs in HIV patients with regard to the extent and etiology of liver injury. Total RNA was extracted from 335 serum samples of HIV patients and 22 healthy control participants using Qiazol. Comprehensive polymerase chain reaction (PCR) array analyses (768 miRNA) were performed in serum samples of eight HIV, eight HIV/HCV (hepatitis C virus), six HCV patients, and three healthy controls. Reverse transcription (RT)-PCR measured levels of miRNA-122, miRNA-22, and miRNA-34a in serum samples of 335 patients and 19 healthy control participants. Liver injury and fibrosis in these patients were defined using aspartate aminotransferase (AST) levels, fibrosis-4 (FIB-4) index and AST-to-platelet ratio index (APRI) score. The miRNA pattern of HIV/HCV samples showed altered expression of 57 and 33 miRNA compared to HCV and HIV infection, respectively. miRNA-122, miRNA-22, and miRNA-34a were highly up-regulated in HIV/HCV patients. Analyzing the entire cohort, these miRNAs were correlated with liver function tests and were independent predictors of liver injury (AST >2 × ULN). miRNA-122 and miRNA-22 were associated with relevant fibrosis (FIB-4 >1.45; APRI >1). Circulating levels of miRNA-122 were independent predictors for relevant fibrosis in HIV patients. Interestingly, miRNA-122 and miRNA-34a levels were higher in HIV/HCV patients, miRNA-22 levels were highest in HIV/HBV patients, and circulating levels of miRNA-34a correlated positively with illicit drug use and ethanol consumption.

CONCLUSION

Circulating miRNA-122, miRNA-22, and miRNA-34a correlates with the etiology of liver injury in HIV patients. These biomarkers not only mirror different mechanisms of hepatic injury, but also are independent predictors of liver injury in HIV patients.

Absolute quantification of serum microRNA-122 and its correlation with liver inflammation grade and serum alanine aminotransferase in chronic hepatitis C patients

OBJECTIVES

MicroRNA-122 has been shown to be crucial for efficient HCV RNA replication in vitro. Pretreatment intrahepatic microRNA-122 levels in chronic hepatitis C (CHC) patients have been associated with the outcomes of interferon therapy. Here, we determined microRNA-122 serum levels in CHC patients and healthy donors using an absolute quantification approach and evaluated the correlation with liver inflammation grades and serum alanine aminotransferase (ALT) levels.

METHODS

Serum samples were collected from 105 treatment-naive CHC patients, 11 acute hepatitis patients, and 33 healthy donors. Serum microRNA-122 was measured using the TaqMan RT-qPCR. The cycle threshold values were converted to copy numbers by drawing a standard curve using a chemical synthetic standard. For accurate quantification, copy numbers were further normalized according to the recovery ratios of spiked-in cel-miR-39.

RESULTS

Serum levels of microRNA-122 were significantly higher in acute hepatitis and CHC patients than in healthy donors (p<0.001). However, there was no significant association between microRNA-122 and ALT serum levels or liver inflammation grades.

CONCLUSIONS

The present study showed that serum microRNA-122 was elevated in acute and chronic hepatitis patients. However, this biomarker for acute liver injury did not reflect the liver inflammation activity in CHC patients.

MicroRNAs play a role in spontaneous recovery from acute liver failure

Acute liver failure (ALF) represents a life-threatening situation characterized by sudden and massive liver cell death in the absence of preexisting liver disease. Although most patients require liver transplantation to prevent mortality, some recover spontaneously and show complete liver regeneration. Because of the rarity of this disease, the molecular mechanisms regulating liver regeneration in ALF patients remain largely unknown. In this study, we investigated the role of microRNAs (miRs) that have been implicated in liver injury and regeneration in sera from ALF patients (n = 63). Patients with spontaneous recovery from ALF showed significantly higher serum levels of miR-122, miR-21, and miR-221, compared to nonrecovered patients. In liver biopsies, miR-21 and miR-221 displayed a reciprocal expression pattern and were found at lower levels in the spontaneous survivors, whereas miR-122 was elevated in both serum and liver tissue of those patients. As compared to nonrecovered patients, liver tissue of spontaneous survivors revealed not only increased hepatocyte proliferation, but also a strong down-regulation of miRNA target genes that impair liver regeneration, including heme oxygenase-1, programmed cell death 4, and the cyclin-dependent kinase inhibitors p21, p27, and p57.

CONCLUSION

Our data suggest that miR-122, miR-21, and miR-221 are involved in liver regeneration and might contribute to spontaneous recovery from ALF. Prospective studies will show whether serological detection of those miRNAs might be of prognostic value to predict ALF outcome.

Development of blood biomarkers for drug-induced liver injury: an evaluation of their potential for risk assessment and diagnostics

Drug-induced liver injury (DILI) remains a rare but serious complication in drug therapy that is a primary cause of drug failure during clinical trials. Conventional biomarkers, particularly the serum transaminases and bilirubin, serve as useful indicators of hepatocellular or cholestatic liver injury, respectively, but only after substantial and sometimes irreversible tissue damage. Ideally, more sensitive biomarkers that respond very early before irreversible injury has occurred would offer improved outcomes. Novel biomarkers are initially being developed in animal models exposed to intrinsically hepatotoxic stimuli. However, the eventual translation to human populations, even those with known risk factors that predispose the liver to drug toxicity, would be the fundamental goal. Ultimately, some might even be applicable for the early identification of individuals predisposed to idiosyncratic hepatotoxicity potential. This article reviews recent progress in the discovery and qualification of novel biomarkers for DILI and delineates the path to eventual utilization for risk assessment. Some major categories of plasma or serum biomarkers surveyed include proteins, cytokines, circulating mRNAs, and microRNAs.

Detection and quantification of extracellular microRNAs in murine biofluids

BACKGROUND

MicroRNAs (miRNAs) are short RNA molecules which regulate gene expression in eukaryotic cells, and are abundant and stable in biofluids such as blood serum and plasma. As such, there has been heightened interest in the utility of extracellular miRNAs as minimally invasive biomarkers for diagnosis and monitoring of a wide range of human pathologies. However, quantification of extracellular miRNAs is subject to a number of specific challenges, including the relatively low RNA content of biofluids, the possibility of contamination with serum proteins (including RNases and PCR inhibitors), hemolysis, platelet contamination/activation, a lack of well-established reference miRNAs and the biochemical properties of miRNAs themselves. Protocols for the detection and quantification of miRNAs in biofluids are therefore of high interest.

RESULTS

The following protocol was validated by quantifying miRNA abundance in C57 (wild-type) and dystrophin-deficient (mdx) mice. Important differences in miRNA abundance were observed depending on whether blood was taken from the jugular or tail vein. Furthermore, efficiency of miRNA recovery was reduced when sample volumes greater than 50 μl were used.

CONCLUSIONS

Here we describe robust and novel procedures to harvest murine serum/plasma, extract biofluid RNA, amplify specific miRNAs by RT-qPCR and analyze the resulting data, enabling the determination of relative and absolute miRNA abundance in extracellular biofluids with high accuracy, specificity and sensitivity.

Circulating microRNA 122 in the methionine and choline-deficient mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a progressive form of non-alcoholic fatty liver disease (NAFLD) and is a major cause of liver cirrhosis and hepatic failure. The methionine choline-deficient diet (MCD) is a frequently used hepatotoxicity animal model of NASH that induces hepatic transaminase (ALT, AST) elevations and hepatobiliary histological changes similar to those observed in human NASH. Liver-specific microRNA-122 (miR-122) has been shown as a key regulator of cholesterol and fatty acid metabolism in adult liver, and has recently been proposed as a sensitive and specific circulating biomarker of hepatic injury. The purpose of this study was to assess miR-122 serum levels in mice receiving an MCD diet for 0, 3, 7, 14, 28 and 56 days and compare the performance vs. routine clinical chemistry when benchmarked against the histopathological liver findings. MiR-122 levels were quantified in serum using RT-qPCR. Both miR-122 and ALT/AST levels were significantly elevated in serum at all timepoints. MiR-122 levels increased on average by 40-fold after 3 days of initiating the MCD diet, whereas ALT and AST changes were 4.8- and 3.3-fold, respectively. In general, miR-122 levels remained elevated across all time points, whereas the ALT/AST increases were less robust but correlated with the progressive severity of NASH as assessed by histopathology. In conclusion, serum levels of miR-122 can potentially be used as a sensitive biomarker for the early detection of hepatotoxicity and can aid in monitoring the extent of NAFLD-associated liver injury in mouse efficacy models.

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.