Human liver regeneration is characterized by the coordinated expression of distinct microRNA governing cell cycle fate

microRNA associated with hepatocyte injury and systemic inflammation may predict adverse outcomes in cirrhotic patients

As the global prevalence of chronic liver disease continues to rise, the need to determine which patients will develop end-stage liver disease and require liver transplantation is increasingly important. However, current prognostic models perform sub-optimally. We aim to determine microRNA profiles associated with clinical decompensation and mortality/transplantation within 1 year. We examined microRNA expression profiles in plasma samples from patients across the spectrum of cirrhosis (n = 154), acute liver failure (ALF) (n = 22), sepsis (n = 20) and healthy controls (HC) (n = 20). We demonstrated that a microRNA-based model (miR-24 and -27a) associated with systemic inflammation differentiated decompensated cirrhosis states from compensated cirrhosis and HC (AUC 0.77 (95% CI 0.69-0.85)). 6 patients within the compensated cirrhosis group decompensated the subsequent year and their exclusion improved model performance (AUC 0.81 (95% CI 0.71-0.89)). miR-191 (associated with liver injury) predicted risk of mortality across the cohort when acutely decompensated and acute-on-chronic-liver failure patients were included. When they were excluded miR-24 (associated with systemic inflammation) predicted risk of mortality. Our findings demonstrate that microRNA associated with systemic inflammation and liver injury predict adverse outcomes in cirrhosis. miR-24 and -191 require further investigation as prognostic biomarkers and therapeutic targets for patients with liver disease.

The Role of Mechanistic Biomarkers in Understanding Acetaminophen Hepatotoxicity in Humans

Our understanding of the fundamental molecular mechanisms of acetaminophen (APAP) hepatotoxicity began in 1973 to 1974, when investigators at the US National Institutes of Health published seminal studies demonstrating conversion of APAP to a reactive metabolite that depletes glutathione and binds to proteins in the liver in mice after overdose. Since then, additional groundbreaking experiments have demonstrated critical roles for mitochondrial damage, oxidative stress, nuclear DNA fragmentation, and necrotic cell death as well. Over the years, some investigators have also attempted to translate these mechanisms to humans using human specimens from APAP overdose patients. This review presents those studies and summarizes what we have learned about APAP hepatotoxicity in humans so far. Overall, the mechanisms of APAP hepatotoxicity in humans strongly resemble those discovered in experimental mouse and cultured hepatocyte models, and emerging biomarkers also suggest similarities in liver repair. The data not only validate the first mechanistic studies of APAP-induced liver injury performed 50 years ago but also demonstrate the human relevance of numerous studies conducted since then. SIGNIFICANCE STATEMENT: Human studies using novel translational, mechanistic biomarkers have confirmed that the fundamental mechanisms of acetaminophen (APAP) hepatotoxicity discovered in rodent models since 1973 are the same in humans. Importantly, these findings have guided the development and understanding of treatments such as N-acetyl-l-cysteine and 4-methylpyrazole over the years. Additional research may improve not only our understanding of APAP overdose pathophysiology in humans but also our ability to predict and treat serious liver injury in patients.

MicroRNAs in chronic pediatric diseases (Review)

MicroRNAs are small non-coding RNAs with a length of 20-24 nucleotides. They bind to the 3'-untranslated region of target genes to induce the degradation of target mRNAs or inhibit their translation. Therefore, they are involved in the regulation of development, apoptosis, proliferation, differentiation and other biological processes (including hormone secretion, signaling and viral infections). Chronic diseases in children may be difficult to treat and are often associated with malnutrition resulting from a poor diet. Consequently, further complications, disease aggravation and increased treatment costs impose a burden on patients and their families. Existing evidence suggests that microRNAs are involved in various chronic non-neoplastic diseases in children. The present review discusses the roles of microRNAs in five major chronic diseases in children, namely, diabetes mellitus, congenital heart diseases, liver diseases, bronchial asthma and epilepsy, providing a theoretical basis for them to become therapeutic biomarkers in chronic pediatric diseases.

The challenges and potential of microRNA-based therapy for patients with liver failure syndromes and hepatocellular carcinoma

INTRODUCTION

Morbidity and mortality from liver disease continues to rise worldwide. There are currently limited curative treatments for patients with liver failure syndromes, encompassing acute liver failure and decompensated cirrhosis states, outside of transplantation. Whilst there have been improvements in therapeutic options for patients with hepatocellular carcinoma (HCC), there remain challenges necessitating novel therapeutic agents. microRNA have long been seen as potential therapeutic targets but there has been limited clinical translation.

AREAS COVERED

We will discuss the limitations of conventional non-transplant management of patients with liver failure syndromes and HCC. We will provide an overview of microRNA and the challenges in developing and delivering microRNA-based therapeutic agents. We will finally provide an overview of microRNA-based therapeutic agents which have progressed to clinical trials.

EXPERT OPINION

microRNA have great potential to be developed into therapeutic agents due to their association with critical biological processes which govern health and disease. Utilizing microRNA sponges to target multiple microRNA associated with specific biological processes may improve their therapeutic efficacy. However, there needs to be significant improvements in delivery systems to ensure the safe delivery of microRNA to target sites and minimize systemic distribution. This currently significantly impacts the clinical translation of microRNA-based therapeutic agents.

The Evolution of Circulating Biomarkers for Use in Acetaminophen/Paracetamol-Induced Liver Injury in Humans: A Scoping Review

Acetaminophen (APAP) is a widely used drug, but overdose can cause severe acute liver injury. The first reports of APAP hepatotoxicity in humans were published in 1966, shortly after the development of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as the first biomarkers of liver injury as opposed to liver function. Thus, the field of liver injury biomarkers has evolved alongside the growth in APAP hepatotoxicity incidence. Numerous biomarkers have been proposed for use in the management of APAP overdose patients in the intervening years. Here, we comprehensively review the development of these markers from the 1960s to the present day and briefly discuss possible future directions.

Acute Liver Failure: Biomarkers Evaluated by the Acute Liver Failure Study Group

There has been a growing interest in identifying prognostic biomarkers that alone or with available prognostic models (King's College Criteria, KCC; MELD and ALFSG Prognostic Index) would improve prognosis in acute liver failure (ALF) patients being assessed for liver transplantation. The Acute Liver Failure Study Group (ALFSG) has evaluated 15 potential prognostic biomarkers: serum AFP; apoptosis-associated proteins; serum actin-free Gc-globulin; serum glycodeoxycholic acid; sRAGE/RAGE ligands; plasma osteopontin; circulating MBL, M-, L-, H-ficolin and CL-1; plasma galectin-9; serum FABP1; serum Lct2; miRNAs; factor V; thrombocytopenia, and sCD163. The ALFSG also has reported on 4 susceptibility biomarkers: keratins 8 and 18 (K8/K18) gene variants; polymorphisms of genes encoding putative APAP-metabolizing enzymes ( UGT1A1 , UGT 1A0 , UGT 2B15 , SULT1A1 , CYP2E1 , and CYP3A5 ) as well as CD44 and BHMT1 ; single nucleotide polymorphisms (SNPs) of genes associated with human behavior, rs2282018 in the arginine vasopressin ( AVP ) gene and rs11174811 in the AVP receptor 1A gene. Finally, rs2277680 of the CSCL16 gene in HBV-ALF patients. In conclusion, we have reviewed the prognostic and susceptibility biomarkers studied by the ALFSG. We suggest that a better approach to predicting the clinical outcome of an ALF patient will require a combination of biomarkers of pathogenic processes such as cell death, hepatic regeneration, and degree of inflammation that could be incorporated into prognostic models such as KCC, MELD or ALFSG PI.

Biological and Mechanical Factors and Epigenetic Regulation Involved in Tendon Healing

Tendons are an important part of the musculoskeletal system. Connecting muscles to bones, tendons convert force into movement. Tendon injury can be acute or chronic. Noticeably, tendon healing requires a long time span and includes inflammation, proliferation, and remodeling processes. The mismatch between endogenous and exogenous healing may lead to adhesion causing further negative effects. Management of tendon injuries and complications such as subsequent adhesion formation are still challenges for clinicians. Due to numerous factors, tendon healing is a complex process. This review introduces the role of various biological and mechanical factors and epigenetic regulation processes involved in tendon healing.

MicroRNAs: Small molecules with big impacts in liver injury

A type of small noncoding RNAs known as microRNAs (miRNAs) fine-tune gene expression posttranscriptionally by binding to certain messenger RNA targets. Numerous physiological processes in the liver, such as differentiation, proliferation, and apoptosis, are regulated by miRNAs. Additionally, there is growing evidence that miRNAs contribute to liver pathology. Extracellular vesicles like exosomes, which contain secreted miRNAs, may facilitate paracrine and endocrine communication between various tissues by changing the gene expression and function of distal cells. The use of stable miRNAs as noninvasive biomarkers was made possible by the discovery of these molecules in body fluids. Circulating miRNAs reflect the conditions of the liver that are abnormal and may serve as new biomarkers for the early detection, prognosis, and evaluation of liver pathological states. miRNAs are appealing therapeutic targets for a range of liver disease states because altered miRNA expression is associated with deregulation of the liver's metabolism, liver damage, liver fibrosis, and tumor formation. This review provides a comprehensive review and update on miRNAs biogenesis pathways and mechanisms of miRNA-mediated gene silencing. It also outlines how miRNAs affect hepatic cell proliferation, death, and regeneration as well as hepatic detoxification. Additionally, it highlights the diverse functions that miRNAs play in the onset and progression of various liver diseases, including nonalcoholic fatty liver disease, alcoholic liver disease, fibrosis, hepatitis C virus infection, and hepatocellular carcinoma. Further, it summarizes the diverse liver-specific miRNAs, illustrating the potential merits and possible caveats of their utilization as noninvasive biomarkers and appealing therapeutic targets for liver illnesses.

Acute liver failure

PURPOSE OF REVIEW

Present an outline of acute liver failure, from its definition to its management in critical care, updated with findings of selected newer research.

RECENT FINDINGS

Survival of patients with acute liver failure has progressively improved. Intracranial hypertension complicating hepatic encephalopathy is now much less frequent than in the past and invasive ICP monitoring is now rarely used. Early renal replacement therapy and possibly therapeutic plasma exchange have consolidated their role in the treatment. Further evidence confirms the low incidence of bleeding in these patients despite striking abnormalities in standard tests of coagulation and new findings of abnormalities on thromboelastographic testing. Specific coagulopathy profiles including an abnormal vWF/ADAMTS13 ratio may be associated with poor outcome and increased bleeding risk. Use of N-acetylcysteine in nonparacetamol-related cases remains unsupported by robust clinical evidence. New microRNA-based prognostic markers to select patients for transplantation are described but are still far from widespread clinical applicability; imaging-based prognostication tools are also promising. The use of extracorporeal artificial liver devices in clinical practice is yet to be supported by evidence.

SUMMARY

Medical treatment of patients with acute liver failure is now associated with significantly improved survival. Better prognostication and selection for emergency liver transplant may further improve care for these patients.

The role of MicroRNAs in tendon injury, repair, and related tissue engineering

Tendon injuries are one of the most common musculoskeletal disorders that cause considerable morbidity and significantly compromise the patients' quality of life. The innate limited regenerative capacity of tendon poses a substantial treating challenge for clinicians. MicroRNAs (miRNAs) are a family of small non-coding RNAs that play a vital role in orchestrating many biological processes through post-transcriptional regulation. Increasing evidence reveals that miRNA-based therapeutics may serve as an innovative strategy for the treatment of tendon pathologies. In this review, we briefly present miRNA biogenesis, the role of miRNAs in tendon cell biology and their involvement in tendon injuries, followed by a summary of current miRNA-based approaches in tendon tissue engineering with a special focus on attenuating post-injury fibrosis. Next, we discuss the advantages of miRNA-functionalized scaffolds in achieving sustained and localized miRNA administration to minimize off-target effects, and thus hoping to inspire the development of effective miRNA delivery platforms specifically for tendon tissue engineering. We envision that advancement in miRNA-based therapeutics will herald a new era of tendon tissue engineering and pave a way for clinical translation for the treatments of tendon disorders.

A novel microRNA-based prognostic model outperforms standard prognostic models in patients with acetaminophen-induced acute liver failure

BACKGROUND & AIMS

Acetaminophen (APAP)-induced acute liver failure (ALF) remains the most common cause of ALF in the Western world. Conventional prognostic models, utilising markers of liver injury and organ failure, lack sensitivity for mortality prediction. We previously identified a microRNA signature that is associated with successful regeneration post-auxiliary liver transplant and with recovery from APAP-ALF. Herein, we aimed to use this microRNA signature to develop outcome prediction models for APAP-ALF.

METHODS

We undertook a nested, case-control study using serum samples from 194 patients with APAP-ALF enrolled in the US ALF Study Group registry (1998-2014) at early (day 1-2) and late (day 3-5) time-points. A microRNA qPCR panel of 22 microRNAs was utilised to assess microRNA expression at both time-points. Multiple logistic regression was used to develop models which were compared to conventional prognostic models using the DeLong method.

RESULTS

Individual microRNAs confer limited prognostic value when utilised in isolation. However, incorporating them within microRNA-based outcome prediction models increases their clinical utility. Our early time-point model (AUC = 0.78, 95% CI 0.71-0.84) contained a microRNA signature associated with liver regeneration and our late time-point model (AUC = 0.83, 95% CI 0.76-0.89) contained a microRNA signature associated with cell-death. Both models were enhanced when combined with model for end-stage liver disease (MELD) score and vasopressor use and both outperformed the King's College criteria. The early time-point model combined with clinical parameters outperformed the ALF Study Group prognostic index and the MELD score.

CONCLUSIONS

Our findings demonstrate that a regeneration-linked microRNA signature combined with readily available clinical parameters can outperform existing prognostic models for ALF in identifying patients with poor prognosis who may benefit from transplantation.

LAY SUMMARY

While acute liver failure can be reversible, some patients will die without a liver transplant. We show that blood test markers that measure the potential for liver recovery may help improve identification of patients unlikely to survive acute liver failure who may benefit from a liver transplant.

Regeneration linked miRNA modify tumor phenotype and can enforce multi-lineage growth arrest in vivo

Regulated cell proliferation is an effector mechanism of regeneration, whilst dysregulated cell proliferation is a feature of cancer. We have previously identified microRNA (miRNA) that regulate successful and failed human liver regeneration. We hypothesized that these regulators may directly modify tumor behavior. Here we show that inhibition of miRNAs -503 and -23a, alone or in combination, enhances tumor proliferation in hepatocyte and non-hepatocyte derived cancers in vitro, driving more aggressive tumor behavior in vivo. Inhibition of miRNA-152 caused induction of DNMT1, site-specific methylation with associated changes in gene expression and in vitro and in vivo growth inhibition. Enforced changes in expression of two miRNA recapitulating changes observed in failed regeneration led to complete growth inhibition of multi-lineage cancers in vivo. Our results indicate that regulation of regeneration and tumor aggressiveness are concordant and that miRNA-based inhibitors of regeneration may constitute a novel treatment strategy for human cancers.

Molecular pathways of liver regeneration: A comprehensive review

The liver is a unique parenchymal organ with a regenerative capacity allowing it to restore up to 70% of its volume. Although knowledge of this phenomenon dates back to Greek mythology (the story of Prometheus), many aspects of liver regeneration are still not understood. A variety of different factors, including inflammatory cytokines, growth factors, and bile acids, promote liver regeneration and control the final size of the organ during typical regeneration, which is performed by mature hepatocytes, and during alternative regeneration, which is performed by recently identified resident stem cells called “hepatic progenitor cells”. Hepatic progenitor cells drive liver regeneration when hepatocytes are unable to restore the liver mass, such as in cases of chronic injury or excessive acute injury. In liver maintenance, the body mass ratio is essential for homeostasis because the liver has numerous functions; therefore, a greater understanding of this process will lead to better control of liver injuries, improved transplantation of small grafts and the discovery of new methods for the treatment of liver diseases. The current review sheds light on the key molecular pathways and cells involved in typical and progenitor-dependent liver mass regeneration after various acute or chronic injuries. Subsequent studies and a better understanding of liver regeneration will lead to the development of new therapeutic methods for liver diseases.

Serum MicroRNA Signatures in Recovery From Acute and Chronic Liver Injury and Selection for Liver Transplantation

We previously demonstrated a distinct hepatic microRNA (miRNA) signature (down-regulation of miRNA-23a, -150, - 200b, -503, and -663 and up-regulation of miRNA-20a) is associated with successful regeneration in auxiliary liver transplantation (ALT). This study aimed to evaluate whether the serum expression of this regeneration-linked miRNA signature is associated with clinical outcomes in acute and chronic liver disease. These were represented by patients with acetaminophen-induced acute liver failure (ALF; n = 18) and patients with hepatitis C virus (HCV) undergoing treatment with direct-acting antivirals (n = 56), respectively. Patients were grouped depending on their clinical outcome. Global serum miRNA expression was analyzed using polymerase chain reaction (PCR) arrays and selected miRNA expression using targeted PCR. We demonstrate that specific regeneration-linked miRNAs discriminate outcomes in both clinical scenarios. We further show that miRNA-20a, -23a, -150, -200b, -503, and -663 undergo concordant changes in expression in 3 distinct clinical settings: liver regeneration accompanying successful ALT, clinical recovery after ALF, and clinical recompensation after cure of HCV. This miRNA signature represents a potentially novel biomarker to predict outcome and optimize patient selection for liver transplantation in both acute and chronic liver disease.

MicroRNAs and long non-coding RNAs in liver surgery: Diagnostic and therapeutic merits

BACKGROUND

Hepatectomy and liver transplantation (LT) are the two most commonly performed surgical procedures for various hepatic lesions. microRNA (miRNA) and long non-coding RNA (lncRNA) have been gradually unveiled their roles as either biomarkers for early diagnosis or potentially therapeutic tools to manipulate gene expression in many disease entities. This review aimed to discuss the effects of miRNA or lncRNA in the hepatectomy and LT fields.

DATA SOURCES

We did a literature search from 1990 through January 2018 to summarize the currently available evidence with respect to the effects of miRNA and lncRNA in liver regeneration after partial hepatectomy, as well as their involvement in several key issues related to LT, including ischemia-reperfusion injury, allograft rejection, tolerance, recurrence of original hepatic malignancies, etc. RESULTS: Certain miRNAs and lncRNAs are actively involved in the regulation of various aspects of liver resection and transplantation. During the process of liver regeneration after hepatectomy, the expression of miRNAs and lncRNAs shows dynamic changes.

CONCLUSIONS

It is now clear that miRNAs and lncRNAs orchestrate in various aspects of the pathophysiological process of LT and hepatectomy. Better understanding of the underlying mechanism and future clinical trials may strengthen their positions as either biomarkers or potential therapeutic targets in the management of complications after liver surgery.

MiR-27a/b Regulates Liver Regeneration by Posttranscriptional Modification of Tmub1

BACKGROUND

Transmembrane and ubiquitin-like domain-containing 1 protein (Tmub1) negatively regulates liver regeneration. However, whether this regulation involves posttranscriptional modification of Tmub1 expression is unknown.

AIM

The aim of the study was to investigate whether microRNA (miR)-27a/b regulates posttranscriptional modification of Tmub1 and cell proliferation during liver regeneration.

METHODS

Tmub1 mRNA 3'-untranslated region (UTR) sequences were analyzed using online software. A luciferase assay was used to verify the relationship between miR-27a/b and the 3'-UTR of Tmub1. Rat partial hepatectomy models were used to investigate miR-27a/b and Tmub1 levels after partial hepatectomy. MiR-27a/b expression was down- and up-regulated with mimics and inhibitors, respectively, to observe the effects of miR-27a/b on Tmub1 expression. Quantitative RT-PCR and Western blot analyses were used to measure miR-27a/b and Tmub1 expression. Hepatocyte proliferation was measured using the CCK8 method for BRL-3A liver cells and proliferating cell nuclear antigen and histone H3 phosphorylation in the regenerating liver.

RESULTS

A potential binding site of miR-27a/b was found in the 3'-UTR sequence of Tmub1. Our luciferase assay confirmed that the Tmub1 mRNA 3'-UTR was the target of miR-27a/b. We observed a temporal correlation between miR-27a/b and Tmub1 expression during liver regeneration. MiR-27a/b down-regulated Tmub1 expression both in vivo and in vitro. MiR-27a/b regulated hepatocyte proliferation during liver regeneration.

CONCLUSION

MiR-27a/b regulates hepatocyte proliferation by controlling posttranscriptional modification of Tmub1 during liver regeneration.

Update on the Mechanisms of Liver Regeneration

Liver possesses many critical functions such as synthesis, detoxification, and metabolism. It continually receives nutrient-rich blood from gut, which incidentally is also toxin-rich. That may be why liver is uniquely bestowed with a capacity to regenerate. A commonly studied procedure to understand the cellular and molecular basis of liver regeneration is that of surgical resection. Removal of two-thirds of the liver in rodents or patients instigates alterations in hepatic homeostasis, which are sensed by the deficient organ to drive the restoration process. Although the exact mechanisms that initiate regeneration are unknown, alterations in hemodynamics and metabolism have been suspected as important effectors. Key signaling pathways are activated that drive cell proliferation in various hepatic cell types through autocrine and paracrine mechanisms. Once the prehepatectomy mass is regained, the process of regeneration is adequately terminated. This review highlights recent discoveries in the cellular and molecular basis of liver regeneration.

EASL Clinical Practical Guidelines on the management of acute (fulminant) liver failure

The term acute liver failure (ALF) is frequently applied as a generic expression to describe patients presenting with or developing an acute episode of liver dysfunction. In the context of hepatological practice, however, ALF refers to a highly specific and rare syndrome, characterised by an acute abnormality of liver blood tests in an individual without underlying chronic liver disease. The disease process is associated with development of a coagulopathy of liver aetiology, and clinically apparent altered level of consciousness due to hepatic encephalopathy. Several important measures are immediately necessary when the patient presents for medical attention. These, as well as additional clinical procedures will be the subject of these clinical practice guidelines.

Function and Regulation of MicroRNAs and Their Potential as Biomarkers in Paediatric Liver Disease

MicroRNAs (miRNAs) are short non-coding RNAs involved in biological and pathological processes of every cell type, including liver cells. Transcribed from specific genes, miRNA precursors are processed in the cytoplasm into mature miRNAs and as part of the RNA-induced silencing complex (RISC) complex binds to messenger RNA (mRNA) by imperfect complementarity. This leads to the regulation of gene expression at a post-transcriptional level. The function of a number of different miRNAs in fibrogenesis associated with the progression of chronic liver disease has recently been elucidated. Furthermore, miRNAs have been shown to be both disease-and tissue-specific and are stable in the circulation, which has led to increasing investigation on their utility as biomarkers for the diagnosis of chronic liver diseases, including those in children. Here, we review the current knowledge on the biogenesis of microRNA, the mechanisms of translational repression and the use of miRNA as circulatory biomarkers in chronic paediatric liver diseases including cystic fibrosis associated liver disease, biliary atresia and viral hepatitis B.

The role of microRNAs in liver injury at the crossroad between hepatic cell death and regeneration

The liver fulfills critical metabolic functions, such as controlling blood sugar and ammonia levels, and is of central importance for lipid metabolism and detoxification of environmental and chemical agents, including drugs. Liver injuries of different etiology can elicit a spectrum of responses. Some hepatocytes initiate molecular programs resulting in cell death, whereas others undergo cellular divisions to regenerate the damaged organ. Interestingly, recent research indicates that microRNAs serve as very rapid as well as long-term regulators in these processes. In this review, we discuss their importance in liver disease etiology and progression as well as for therapy with particular focus on metabolic and inflammatory conditions. Furthermore, we highlight the central role of microRNAs in controlling hepatocyte differentiation and plasticity, which are required for successful regeneration, but under certain conditions, such as chronic liver insults, can result in the formation of hepatocellular carcinoma.

MicroRNAs in the Evaluation and Potential Treatment of Liver Diseases

Acute and chronic liver disease continue to result in significant morbidity and mortality of patients, along with increasing burden on their families, society and the health care system. This in part is due to increased incidence of liver disease associated factors such as metabolic syndrome; improved survival of patients with chronic predisposing conditions such as HIV; as well as advances in the field of transplantation and associated care leading to improved survival. The fact that one disease can result in different manifestations and outcomes highlights the need for improved understanding of not just genetic phenomenon predisposing to a condition, but additionally the role of epigenetic and environmental factors leading to the phenotype of the disease. It is not surprising that providers continue to face daily challenges pertaining to diagnostic accuracy, prognostication of disease severity, progression, and response to therapies. A number of these challenges can be addressed by incorporating a personalized approach of management to the current paradigm of care. Recent advances in the fields of molecular biology and genetics have paved the way to more accurate, individualized and precise approach to caring for liver disease. The study of microRNAs and their role in both healthy and diseased livers is one example of such advances. As these small, non-coding RNAs work on fine-tuning of cellular activities and organ function in a dynamic and precise fashion, they provide us a golden opportunity to advance the field of hepatology. The study of microRNAs in liver disease promises tremendous improvement in hepatology and is likely to lay the foundation towards a personalized approach in liver disease.

Role of microRNA in liver regeneration

BACKGROUND

Liver regeneration is a complex process. microRNAs (miRNAs) are short, single-stranded RNAs that modify gene expression at the post-transcriptional level. Recent investigations have revealed that miRNAs are closely linked to liver regeneration.

DATA SOURCES

All included studies were obtained from PubMed, Embase, the ScienceDirect databases and Web of Science, with no limitation on publication year. Only studies published in English were considered.

RESULTS

We grouped studies that involved miRNA and liver regeneration into two groups: miRNAs as promoters and as inhibitors of liver regeneration. We summarized the relevant miRNAs separately from the related pathways.

CONCLUSIONS

Blocking or stimulating the pathways of miRNAs in liver regeneration may be novel therapeutic strategies in future regeneration-related liver managements. We may discover additional chemotherapy targets of miRNA.

Systems analysis of non-parenchymal cell modulation of liver repair across multiple regeneration modes

Background

A hallmark of chronic liver disease is the impairment of the liver’s innate regenerative ability. In this work we use a computational approach to unravel the principles underlying control of liver repair following an acute physiological challenge.

Methods

We used a mathematical model of inter- and intra-cellular interactions during liver regeneration to infer key molecular factors underlying the dysregulation of multiple regeneration modes, including delayed, suppressed, and enhanced regeneration. We used model analysis techniques to identify organizational principles governing the cellular regulation of liver regeneration. We fit our model to several published data sets of deficient regeneration in rats and healthy regeneration in humans, rats, and mice to predict differences in molecular regulation in disease states and across species. 

Results

Analysis of the computational model pointed to an important balance involving inflammatory signals and growth factors, largely produced by Kupffer cells and hepatic stellate cells, respectively. Our model analysis results also indicated an organizational principle of molecular regulation whereby production rate of molecules acted to induce coarse-grained control of signaling levels while degradation rate acted to induce fine-tuning control. We used this computational framework to investigate hypotheses concerning molecular regulation of regeneration across species and in several chronic disease states in rats, including fructose-induced steatohepatitis, alcoholic steatohepatitis, toxin-induced cirrhosis, and toxin-induced diabetes. Our results indicate that altered non-parenchymal cell activation is sufficient to explain deficient regeneration caused by multiple disease states. We also investigated liver regeneration across mammalian species. Our results suggest that non-invasive measures of liver regeneration taken at 30 days following resection could differentiate between several hypotheses about how human liver regeneration differs from rat regeneration.

Conclusions

Overall, our results provide a new computational platform integrating a wide range of experimental information, with broader utility in exploring the dynamic patterns of liver regeneration across species and over multiple chronic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0220-9) contains supplementary material, which is available to authorized users.

miR-150 Deficiency Protects against FAS-Induced Acute Liver Injury in Mice through Regulation of AKT

Although miR-150 is implicated in the regulation of immune cell differentiation and activation, it remains unknown whether miR-150 is involved in liver biology and disease. This study was performed to explore the potential role of miR-150 in LPS/D-GalN and Fas-induced liver injuries by using wild type and miR-150 knockout (KO) mice. Whereas knockout of miR-150 did not significantly alter LPS/D-GalN-induced animal death and liver injury, it protected against Fas-induced liver injury and mortality. The Jo2-induced increase in serum transaminases, apoptotic hepatocytes, PARP cleavage, as well as caspase-3/7, caspase-8, and caspase-9 activities were significantly attenuated in miR-150 KO mice. The liver tissues from Jo2-treated miR-150 KO mice expressed higher levels of Akt1, Akt2, total Akt, as well as p-Akt(Ser473) compared to the wild type livers. Pretreatment with the Akt inhibitor V reversed Jo2-induced liver injury in miR-150 KO mice. The primary hepatocytes isolated from miR-150 KO mice also showed protection against Fas-induced apoptosis in vitro (characterized by less prominent PARP cleavage, less nuclear fragmentation and less caspase activation) in comparison to hepatocytes from wild type mice. Luciferase reporter assays in hepatocytes transfected with the Akt1 or Akt2 3’-UTR reporter constructs (with or without mutation of miR-150 binding site) established Akt1 and Akt2 as direct targets of miR-150. Tail vein injection of lentiviral particles containing pre-miR-150 enhanced Jo2-induced liver injury in miR-150 KO mice. These findings demonstrate that miR-150 deficiency prevents Fas-induced hepatocyte apoptosis and liver injury through regulation of the Akt pathway.

miRNA control of tissue repair and regeneration

Tissue repair and regeneration rely on the function of miRNA, molecular silencers that enact post-transcriptional gene silencing of coding genes. Disruption of miRNA homeostasis is developmentally lethal, indicating that fetal tissue development is tightly controlled by miRNAs. Multiple critical facets of adult tissue repair are subject to control by miRNAs, as well. Sources of cell pool for tissue repair and regeneration are diverse and provided by processes including cellular dedifferentiation, transdifferentiation, and reprogramming. Each of these processes is regulated by miRNAs. Furthermore, induced pluripotency may be achieved by miRNA-based strategies independent of transcription factor manipulation. The observation that miRNA does not integrate into the genome makes miRNA-based therapeutic strategies translationally valuable. Tools to manipulate cellular and tissue miRNA levels include mimics and inhibitors that may be specifically targeted to cells of interest at the injury site. Here, we discuss the extraordinary importance of miRNAs in tissue repair and regeneration based on emergent reports and rapid advances in miRNA-based therapeutics.

The microRNA Expression Profile in Donation after Cardiac Death (DCD) Livers and Its Ability to Identify Primary Non Function

Donation after cardiac death (DCD) livers are marginal organs for transplant and their use is associated with a higher risk of primary non function (PNF) or early graft dysfunction (EGD). The aim was to determine if microRNA (miRNA) was able to discriminate between DCD livers of varying clinical outcome. DCD groups were categorized as PNF retransplanted within a week (n=7), good functional outcome (n=7) peak aspartate transaminase (AST) ≤ 1000 IU/L and EGD (n=9) peak AST ≥ 2500 IU/L. miRNA was extracted from archival formalin fixed post-perfusion tru-cut liver biopsies. High throughput expression analysis was performed using miRNA arrays. Bioinformatics for expression data analysis was performed and validated with real time quantitative PCR (RT-qPCR). The function of miRNA of interest was investigated using computational biology prediction algorithms. From the array analysis 16 miRNAs were identified as significantly different (p<0.05). On RT-qPCR miR-155 and miR-940 had the highest expression across all three DCD clinical groups. Only one miRNA, miR-22, was validated with marginal significance, to have differential expression between the three groups (p=0.049). From computational biology miR-22 was predicted to affect signalling pathways that impact protein turnover, metabolism and apoptosis/cell cycle. In conclusion, microRNA expression patterns have a low diagnostic potential clinically in discriminating DCD liver quality and outcome.

Genomics of liver transplant injury and regeneration

While improved surgical techniques, post-operative care, and immunosuppression regimens have reduced morbidity and mortality associated with orthotopic liver transplantation (OLT), further improvement of outcomes requires personalized treatment and a better understanding of genomic mechanisms involved. Gene expression profiles of ischemia/reperfusion (I/R) injury, regeneration, and rejection, may suggest mechanisms for development of better predictive tools and treatments. The liver is unique in its regenerative potential, recovering lost mass and function after injury from ischemia, resection, and rejection. I/R injury, an inevitable consequence of perfusion cessation, cold storage, and reperfusion, is regulated by the interaction of the immune system, inflammatory cytokines, and reduced microcirculatory blood flow in the liver. Rejection, a common post-operative complication, is mediated by the recipient's immune system through T-cell-dependent responses activating proinflammatory and apoptotic pathways. Characterizing distinctive gene expression signatures for these events can identify therapies to reduce injury, promote regeneration, and improve outcomes. While certain markers of liver injury and regeneration have been observed in animals, many of these are unverified in human studies. Further investigation of these genomic signatures and mechanisms through new technology offers promise, but continues to pose a significant challenge. An overview of the current fund of knowledge in this area is reviewed.

MicroRNA-21 accelerates hepatocyte proliferation in vitro via PI3K/Akt signaling by targeting PTEN

MicroRNAs (miRNAs) are involved in controlling hepatocyte proliferation during liver regeneration. In this study, we established the miRNAs-expression patterns of primary hepatocytes in vitro under stimulation of epidermal growth factor (EGF), and found that microRNA-21 (miR-21) was appreciably up-regulated and peaked at 12h. In addition, we further presented evidences indicating that miR-21 promotes primary hepatocyte proliferation through in vitro transfecting with miR-21 mimics or inhibitor. We further demonstrated that phosphatidylinositol 3'-OH kinase (PI3K)/Akt signaling was altered accordingly, it is, by targeting phosphatase and tensin homologue deleted on chromosome 10, PI3K/Akt signaling is activated by miR-21 to accelerate hepatocyte rapid S-phase entry and proliferation in vitro.