1 4976 123 PATHOPHYSIOLOGICAL MECHANISMS OF HEPATIC STELLATE CELLS ACTIVATION IN LIVER FIBROSIS. LIVER FIBROSIS IS A COMPLEX PATHOLOGICAL PROCESS CONTROLLED BY A VARIETY OF CELLS, MEDIATORS AND SIGNALING PATHWAYS. HEPATIC STELLATE CELLS PLAY A CENTRAL ROLE IN THE DEVELOPMENT OF LIVER FIBROSIS. IN CHRONIC LIVER DISEASE, HEPATIC STELLATE CELLS UNDERGO DRAMATIC PHENOTYPIC ACTIVATION AND ACQUIRE FIBROGENIC PROPERTIES. THIS REVIEW FOCUSES ON THE PATHOPHYSIOLOGICAL MECHANISMS OF HEPATIC STELLATE CELLS ACTIVATION IN LIVER FIBROSIS. THEY ENTER THE CELL CYCLE UNDER THE INFLUENCE OF VARIOUS TRIGGERS. THE "INITIATION" PHASE OF HEPATIC STELLATE CELLS ACTIVATION OVERLAPS AND CONTINUES WITH THE "PERPETUATION" PHASE, WHICH IS CHARACTERIZED BY A PRONOUNCED INFLAMMATORY AND FIBROGENIC REACTION. THIS IS FOLLOWED BY A RESOLUTION PHASE IF THE INJURY SUBSIDES. KNOWLEDGE OF THESE PATHOPHYSIOLOGICAL MECHANISMS PAVED THE WAY FOR DRUGS AIMED AT PREVENTING THE DEVELOPMENT AND PROGRESSION OF LIVER FIBROSIS. IN THIS RESPECT, IMPAIRMENTS IN INTRACELLULAR SIGNALING, EPIGENETIC CHANGES AND CELLULAR STRESS RESPONSE CAN BE THE TARGETS OF THERAPY WHERE THE GOAL IS TO DEACTIVATE HEPATIC STELLATE CELLS. POTENTIAL ANTIFIBROTIC THERAPY MAY FOCUS ON INDUCING HEPATIC STELLATE CELLS TO RETURN TO AN INACTIVE STATE THROUGH CELLULAR AGING, APOPTOSIS, AND/OR CLEARANCE BY IMMUNE CELLS, AND SERVE AS POTENTIAL ANTIFIBROTIC THERAPY. IT IS ESPECIALLY IMPORTANT TO PREVENT THE FORMATION OF LIVER CIRRHOSIS SINCE THE ONLY RADICAL APPROACH TO ITS TREATMENT IS LIVER TRANSPLANTATION WHICH CAN BE PERFORMED IN ONLY A LIMITED NUMBER OF COUNTRIES. 2022 2 2817 35 FIBROSIS IN THE LIVER: ACUTE PROTECTION AND CHRONIC DISEASE. THE UNDERSTANDING OF THE CELLULAR AND MOLECULAR MECHANISMS OF THE FIBROTIC WOUND-HEALING RESPONSE OF THE LIVER HAS MADE DRAMATIC PROGRESS IN THE PAST 20 YEARS. HEPATIC STELLATE CELLS (HSCS), WHICH AFTER LIVER INJURY PROLIFERATE AND TRANSDIFFERENTIATE TO MYOFIBROBLASTS, HAVE EMERGED AS THE PRIMARY SOURCE OF THE FIBROTIC RESPONSE, EVEN THOUGH OTHER FIBROGENIC CELLS MAY ALSO CONTRIBUTE TO THE PRODUCTION OF EXTRACELLULAR MATRIX (ECM). ADVANCES IN THE UNDERSTANDING OF HSC REGULATION INCLUDE APOPTOTIC SIGNALING, ANGIOGENIC SIGNALING, AND RESPONSES TO OXIDATIVE STRESS. THE ECM HAS EMERGED NOT ONLY AS A STRUCTURAL SCAFFOLD, BUT ALSO AS A DYNAMIC AND INTERACTIVE MATRIX REGULATING STELLATE CELL ACTIVATION. ADDITIONALLY, THE INNATE IMMUNE SYSTEM AND IMMUNE SIGNALING, AS WELL AS A BROADENING UNDERSTANDING OF THE TRANSCRIPTIONAL REGULATION INCLUDING MICRORNAS AND EPIGENETIC EVENTS OFFER POTENTIAL THERAPEUTIC TARGETS. UNRAVELING GENETIC DETERMINANTS RELATED TO MECHANISMS OF HEPATIC FIBROGENESIS PROMISE INDIVIDUALIZED THERAPY OR PREVENTION. HEPATIC FIBROSIS AND CIRRHOSIS HAVE EMERGED AS TREATABLE AND POTENTIALLY REVERSIBLE CONSEQUENCE OF CHRONIC LIVER DISEASE. 2010 3 2164 35 EPIGENETIC MECHANISMS IN HEPATIC STELLATE CELL ACTIVATION DURING LIVER FIBROSIS AND CARCINOGENESIS. LIVER FIBROSIS IS AN ESSENTIAL COMPONENT OF CHRONIC LIVER DISEASE (CLD) AND HEPATOCARCINOGENESIS. THE FIBROTIC STROMA IS A CONSEQUENCE OF SUSTAINED LIVER DAMAGE COMBINED WITH EXACERBATED EXTRACELLULAR MATRIX (ECM) ACCUMULATION. IN THIS CONTEXT, ACTIVATION OF HEPATIC STELLATE CELLS (HSCS) PLAYS A KEY ROLE IN BOTH INITIATION AND PERPETUATION OF FIBROGENESIS. THESE CELLS SUFFER PROFOUND REMODELING OF GENE EXPRESSION IN THIS PROCESS. THIS REVIEW IS FOCUSED ON THE EPIGENETIC ALTERATIONS PARTICIPATING IN THE TRANSDIFFERENTIATION OF HSCS FROM THE QUIESCENT TO ACTIVATED STATE. RECENT ADVANCES IN THE FIELD OF DNA METHYLATION AND POST-TRANSLATIONAL MODIFICATIONS (PTM) OF HISTONES (ACETYLATION AND METHYLATION) PATTERNS ARE DISCUSSED HERE, TOGETHER WITH ALTERED EXPRESSION AND ACTIVITY OF EPIGENETIC REMODELERS. WE ALSO CONSIDER RECENT ADVANCES IN TRANSLATIONAL APPROACHES, INCLUDING THE USE OF EPIGENETIC MARKS AS BIOMARKERS AND THE PROMISING ANTIFIBROTIC PROPERTIES OF EPIGENETIC DRUGS THAT ARE CURRENTLY BEING USED IN PATIENTS. 2019 4 2323 32 EPIGENETIC REGULATION OF HEPATIC STELLATE CELL ACTIVATION AND MACROPHAGE IN CHRONIC LIVER INFLAMMATION. CHRONIC LIVER INFLAMMATION IS A COMPLEX PATHOLOGICAL PROCESS UNDER DIFFERENT STRESS CONDITIONS, AND THE ROLES OF STELLATE CELLS AND MACROPHAGES IN CHRONIC LIVER INFLAMMATION HAVE BEEN WIDELY REPORTED. MODERATE LIVER INFLAMMATION CAN PROTECT THE LIVER FROM DAMAGE AND FACILITATE THE RECOVERY OF LIVER INJURY. HOWEVER, AN INFLAMMATORY RESPONSE THAT IS TOO INTENSE CAN RESULT IN MASSIVE DEATH OF HEPATOCYTES, WHICH LEADS TO IRREVERSIBLE DAMAGE TO THE LIVER PARENCHYMA. EPIGENETIC REGULATION PLAYS A KEY PART IN LIVER INFLAMMATION. THIS STUDY REVIEWS THE REGULATION OF EPIGENETICS ON STELLATE CELLS AND MACROPHAGES TO EXPLORE THE NEW MECHANISMS OF EPIGENETICS ON LIVER INFLAMMATION AND PROVIDE NEW IDEAS FOR THE TREATMENT OF LIVER DISEASE. 2021 5 3245 39 HEPATIC STELLATE CELLS AS KEY TARGET IN LIVER FIBROSIS. PROGRESSIVE LIVER FIBROSIS, INDUCED BY CHRONIC VIRAL AND METABOLIC DISORDERS, LEADS TO MORE THAN ONE MILLION DEATHS ANNUALLY VIA DEVELOPMENT OF CIRRHOSIS, ALTHOUGH NO ANTIFIBROTIC THERAPY HAS BEEN APPROVED TO DATE. TRANSDIFFERENTIATION (OR "ACTIVATION") OF HEPATIC STELLATE CELLS IS THE MAJOR CELLULAR SOURCE OF MATRIX PROTEIN-SECRETING MYOFIBROBLASTS, THE MAJOR DRIVER OF LIVER FIBROGENESIS. PARACRINE SIGNALS FROM INJURED EPITHELIAL CELLS, FIBROTIC TISSUE MICROENVIRONMENT, IMMUNE AND SYSTEMIC METABOLIC DYSREGULATION, ENTERIC DYSBIOSIS, AND HEPATITIS VIRAL PRODUCTS CAN DIRECTLY OR INDIRECTLY INDUCE STELLATE CELL ACTIVATION. DYSREGULATED INTRACELLULAR SIGNALING, EPIGENETIC CHANGES, AND CELLULAR STRESS RESPONSE REPRESENT CANDIDATE TARGETS TO DEACTIVATE STELLATE CELLS BY INDUCING REVERSION TO INACTIVATED STATE, CELLULAR SENESCENCE, APOPTOSIS, AND/OR CLEARANCE BY IMMUNE CELLS. CELL TYPE- AND TARGET-SPECIFIC PHARMACOLOGICAL INTERVENTION TO THERAPEUTICALLY INDUCE THE DEACTIVATION WILL ENABLE MORE EFFECTIVE AND LESS TOXIC PRECISION ANTIFIBROTIC THERAPIES. 2017 6 5805 44 STRATEGIES TO PREVENT AND REVERSE LIVER FIBROSIS IN HUMANS AND LABORATORY ANIMALS. LIVER FIBROSIS RESULTS FROM CHRONIC DAMAGE TO THE LIVER IN CONJUNCTION WITH VARIOUS PATHWAYS AND IS MEDIATED BY A COMPLEX MICROENVIRONMENT. BASED ON CLINICAL OBSERVATIONS, IT IS NOW EVIDENT THAT FIBROSIS IS A DYNAMIC, BIDIRECTIONAL PROCESS WITH AN INHERENT CAPACITY FOR RECOVERY AND REMODELING. THE MAJOR MECHANISMS INVOLVED IN LIVER FIBROSIS INCLUDE THE REPETITIVE INJURY OF HEPATOCYTES, THE ACTIVATION OF THE INFLAMMATORY RESPONSE AFTER INJURY STIMULATION, AND THE ACTIVATION AND PROLIFERATION OF HEPATIC STELLATE CELLS (HSCS), WHICH REPRESENTS THE MAJOR EXTRACELLULAR MATRIX (ECM)-PRODUCING CELLS, STIMULATED BY HEPATOCYTE INJURY AND INFLAMMATION. THE MICROENVIRONMENT IN THE LIVER IS SYNERGISTICALLY REGULATED ABNORMAL ECM DEPOSITION, SCAR FORMATION, ANGIOGENESIS, AND FIBROGENESIS. MOREOVER, RECENT STUDIES HAVE CLARIFIED NOVEL MECHANISM IN FIBROSIS SUCH AS EPIGENETIC REGULATION OF HSCS, THE LEPTIN AND PPARGAMMA PATHWAYS, THE COAGULATION SYSTEM, AND EVEN AUTOPHAGY. UNCOVERING THE MECHANISMS OF LIVER FIBROGENESIS PROVIDES A BASIS TO DEVELOP POTENTIAL THERAPIES TO REVERSE AND TREAT THE FIBROTIC RESPONSE, THEREBY IMPROVING THE OUTCOMES OF PATIENTS WITH CHRONIC LIVER DISEASE. ALTHOUGH BOTH SCIENTIFIC AND CLINICAL CHALLENGES REMAIN, EMERGING STUDIES ATTEMPT TO REVEAL THE IDEAL ANTI-FIBROTIC DRUG THAT COULD BE EASILY DELIVERED TO THE LIVER WITH HIGH SPECIFICITY AND LOW TOXICITY. THIS REVIEW HIGHLIGHTS THE MECHANISMS, INCLUDING NOVEL PATHWAYS UNDERLYING FIBROGENESIS THAT MAY BE TRANSLATED INTO PREVENTIVE AND TREATMENT STRATEGIES, REVIEWS BOTH CURRENT AND NOVEL AGENTS THAT TARGET SPECIFIC PATHWAYS OR MULTIPLE TARGETS, AND DISCUSSES NOVEL DRUG DELIVERY SYSTEMS SUCH AS NANOTECHNOLOGY THAT CAN BE APPLIED IN THE TREATMENT OF LIVER FIBROSIS. IN ADDITION, WE ALSO DISCUSS SOME CURRENT TREATMENT STRATEGIES THAT ARE BEING APPLIED IN ANIMAL MODELS AND IN CLINICAL TRIALS. 2015 7 4448 31 MOLECULAR MECHANISM AND TREATMENT OF VIRAL HEPATITIS-RELATED LIVER FIBROSIS. HEPATIC FIBROSIS IS A WOUND-HEALING RESPONSE TO VARIOUS CHRONIC STIMULI, INCLUDING VIRAL HEPATITIS B OR C INFECTION. ACTIVATED MYOFIBROBLASTS, PREDOMINANTLY DERIVED FROM THE HEPATIC STELLATE CELLS (HSCS), REGULATE THE BALANCE BETWEEN MATRIX METALLOPROTEINASES AND THEIR TISSUE INHIBITORS TO MAINTAIN EXTRACELLULAR MATRIX HOMEOSTASIS. TRANSFORMING GROWTH FACTOR-BETA AND PLATELET-DERIVED GROWTH FACTOR ARE CLASSIC PROFIBROGENIC SIGNALS THAT ACTIVATE HSC PROLIFERATION. IN ADDITION, PROINFLAMMATORY CYTOKINES AND CHEMOKINES COORDINATE MACROPHAGES, T CELLS, NK/NKT CELLS, AND LIVER SINUSOIDAL ENDOTHELIAL CELLS IN COMPLEX FIBROGENIC AND REGRESSION PROCESSES. IN ADDITION, FIBROGENESIS INVOLVES ANGIOGENESIS, METABOLIC REPROGRAMMING, AUTOPHAGY, MICRORNA, AND EPIGENETIC REGULATIONS. HEPATIC INFLAMMATION IS THE DRIVING FORCE BEHIND LIVER FIBROSIS; HOWEVER, HOST SINGLE NUCLEOTIDE POLYMORPHISMS AND VIRAL FACTORS, INCLUDING THE GENOTYPE, VIRAL LOAD, VIRAL MUTATION, AND VIRAL PROTEINS, HAVE BEEN ASSOCIATED WITH FIBROSIS PROGRESSION. ELIMINATING THE UNDERLYING ETIOLOGY IS THE MOST CRUCIAL ANTIFIBROTIC THERAPY. GROWING EVIDENCE HAS INDICATED THAT PERSISTENT VIRAL SUPPRESSION WITH ANTIVIRAL THERAPY CAN RESULT IN FIBROSIS REGRESSION, REDUCED LIVER DISEASE PROGRESSION, DECREASED HEPATOCELLULAR CARCINOMA, AND IMPROVED CHANCES OF SURVIVAL. PRECLINICAL STUDIES AND CLINICAL TRIALS ARE CURRENTLY EXAMINING SEVERAL INVESTIGATIONAL AGENTS THAT TARGET KEY FIBROGENIC PATHWAYS; THE RESULTS ARE PROMISING AND SHED LIGHT ON THIS DEBILITATING ILLNESS. 2014 8 6372 33 THE ROLE OF MIR-29A IN THE REGULATION, FUNCTION, AND SIGNALING OF LIVER FIBROSIS. BOTH FIBROSIS AND CIRRHOSIS OF THE LIVER ARE THE END RESULTS OF MOST KINDS OF CHRONIC LIVER DAMAGE AND REPRESENT A COMMON BUT DIFFICULT CLINICAL CHALLENGE THROUGHOUT THE WORLD. THE INHIBITION OF THE FIBROGENIC, PROLIFERATIVE, AND MIGRATORY EFFECTS OF HEPATIC STELLATE CELLS (HSCS) HAS BECOME AN EXPERIMENTAL THERAPY FOR PREVENTING AND EVEN REVERSING HEPATIC FIBROSIS. FURTHERMORE, A COMPLETE UNDERSTANDING OF THE FUNCTION OF NON-CODING RNA-MEDIATED EPIGENETIC MECHANISMS IN HSC ACTIVATION MAY IMPROVE OUR PERCEPTION OF LIVER FIBROSIS PATHOGENESIS. THIS REVIEW FOCUSES ON THE EVOLVING VIEW OF THE MOLECULAR MECHANISMS BY WHICH HSC ACTIVATION BY MIR-29A SIGNALING MAY MODERATE THE PROFIBROGENIC PHENOTYPE OF THESE CELLS, THUS SUPPORTING THE USE OF MIR-29A AGONISTS AS A POTENTIAL THERAPY FOR TREATING LIVER FIBROSIS IN THE FUTURE. 2018 9 2545 36 EPIGENETICS IN LIVER FIBROSIS: COULD HDACS BE A THERAPEUTIC TARGET? CHRONIC LIVER DISEASES (CLD) REPRESENT A WORLDWIDE HEALTH PROBLEM. WHILE CLDS MAY HAVE DIVERSE ETIOLOGIES, A COMMON PATHOGENIC DENOMINATOR IS THE PRESENCE OF LIVER FIBROSIS. CIRRHOSIS, THE END-STAGE OF CLD, IS CHARACTERIZED BY EXTENSIVE FIBROSIS AND IS MARKEDLY ASSOCIATED WITH THE DEVELOPMENT OF HEPATOCELLULAR CARCINOMA. THE MOST IMPORTANT EVENT IN HEPATIC FIBROGENESIS IS THE ACTIVATION OF HEPATIC STELLATE CELLS (HSC) FOLLOWING LIVER INJURY. ACTIVATED HSCS ACQUIRE A MYOFIBROBLAST-LIKE PHENOTYPE BECOMING PROLIFERATIVE, FIBROGENIC, AND CONTRACTILE CELLS. WHILE TRANSIENT ACTIVATION OF HSCS IS PART OF THE PHYSIOLOGICAL MECHANISMS OF TISSUE REPAIR, PROTRACTED ACTIVATION OF A WOUND HEALING REACTION LEADS TO ORGAN FIBROSIS. THE PHENOTYPIC CHANGES OF ACTIVATED HSCS INVOLVE EPIGENETIC MECHANISMS MEDIATED BY NON-CODING RNAS (NCRNA) AS WELL AS BY CHANGES IN DNA METHYLATION AND HISTONE MODIFICATIONS. DURING CLD THESE EPIGENETIC MECHANISMS BECOME DEREGULATED, WITH ALTERATIONS IN THE EXPRESSION AND ACTIVITY OF EPIGENETIC MODULATORS. HERE WE PROVIDE AN OVERVIEW OF THE EPIGENETIC ALTERATIONS INVOLVED IN FIBROGENIC HSCS TRANSDIFFERENTIATION WITH PARTICULAR FOCUS ON HISTONES ACETYLATION CHANGES. WE ALSO DISCUSS RECENT STUDIES SUPPORTING THE PROMISING THERAPEUTIC POTENTIAL OF HISTONE DEACETYLASE INHIBITORS IN LIVER FIBROSIS. 2020 10 2322 31 EPIGENETIC REGULATION OF HEPATIC STELLATE CELL ACTIVATION AND LIVER FIBROSIS. CHRONIC LIVER INJURY TO HEPATOCYTES OR CHOLANGIOCYTES, WHEN LEFT UNMANAGED, LEADS TO THE DEVELOPMENT OF LIVER FIBROSIS, A CONDITION CHARACTERIZED BY THE EXCESSIVE INTRAHEPATIC DEPOSITION OF EXTRACELLULAR MATRIX PROTEINS. ACTIVATED HEPATIC STELLATE CELLS CONSTITUTE THE PREDOMINANT SOURCE OF EXTRACELLULAR MATRIX IN FIBROTIC LIVERS AND THEIR TRANSITION FROM A QUIESCENT STATE DURING FIBROGENESIS IS ASSOCIATED WITH IMPORTANT ALTERATIONS IN THEIR TRANSCRIPTIONAL AND EPIGENETIC LANDSCAPE. AREAS COVERED: WE BRIEFLY DESCRIBE THE PROCESSES INVOLVED IN HEPATIC STELLATE CELL ACTIVATION AND DISCUSS OUR CURRENT UNDERSTANDING OF ALTERATIONS IN THE EPIGENETIC LANDSCAPE, I.E DNA METHYLATION, HISTONE MODIFICATIONS AND THE FUNCTIONAL ROLE OF NON-CODING RNAS THAT ACCOMPANY THIS KEY EVENT IN THE DEVELOPMENT OF CHRONIC LIVER DISEASE. EXPERT COMMENTARY: ALTHOUGH GREAT PROGRESS HAS BEEN MADE, OUR UNDERSTANDING OF THE EPIGENETIC REGULATION OF HEPATIC STELLATE CELL ACTIVATION IS LIMITED AND, THUS FAR, INSUFFICIENT TO ALLOW THE DEVELOPMENT OF EPIGENETIC DRUGS THAT CAN SELECTIVELY INTERRUPT LIVER FIBROSIS. 2016 11 5533 37 ROLE AND MECHANISM OF DNA METHYLATION AND ITS INHIBITORS IN HEPATIC FIBROSIS. LIVER FIBROSIS IS A REPAIR RESPONSE TO INJURY CAUSED BY VARIOUS CHRONIC STIMULI THAT CONTINUALLY ACT ON THE LIVER. AMONG THEM, THE ACTIVATION OF HEPATIC STELLATE CELLS (HSCS) AND THEIR TRANSFORMATION INTO A MYOFIBROBLAST PHENOTYPE IS A KEY EVENT LEADING TO LIVER FIBROSIS, HOWEVER THE MECHANISM HAS NOT YET BEEN ELUCIDATED. THE MOLECULAR BASIS OF HSC ACTIVATION INVOLVES CHANGES IN THE REGULATION OF GENE EXPRESSION WITHOUT CHANGES IN THE GENOME SEQUENCE, NAMELY, VIA EPIGENETIC REGULATION. DNA METHYLATION IS A KEY FOCUS OF EPIGENETIC RESEARCH, AS IT AFFECTS THE EXPRESSION OF FIBROSIS-RELATED, METABOLISM-RELATED, AND TUMOR SUPPRESSOR GENES. INCREASING STUDIES HAVE SHOWN THAT DNA METHYLATION IS CLOSELY RELATED TO SEVERAL PHYSIOLOGICAL AND PATHOLOGICAL PROCESSES INCLUDING HSC ACTIVATION AND LIVER FIBROSIS. THIS REVIEW AIMED TO DISCUSS THE MECHANISM OF DNA METHYLATION IN THE PATHOGENESIS OF LIVER FIBROSIS, EXPLORE DNA METHYLATION INHIBITORS AS POTENTIAL THERAPIES FOR LIVER FIBROSIS, AND PROVIDE NEW INSIGHTS ON THE PREVENTION AND CLINICAL TREATMENT OF LIVER FIBROSIS. 2023 12 2219 39 EPIGENETIC MODIFICATIONS IN HEPATIC STELLATE CELLS CONTRIBUTE TO LIVER FIBROSIS. LIVER FIBROSIS REPRESENTS THE FINAL COMMON PATHWAY OF VIRTUALLY ALL TYPES OF CHRONIC LIVER DISEASES, AND IT HAS BEEN A MAJOR PUBLIC HEALTH CONCERN. MANY GENES HAVE BEEN DEMONSTRATED TO BE INVOLVED IN THE PATHOGENESIS OF LIVER FIBROSIS, WHILE THE MECHANISMS UNDERLYING GENE REGULATION STILL NEEDS FURTHER RESEARCH. ON THE OTHER HAND, HEPATIC STELLATE CELLS (HSCS) ARE QUIESCENT CELLS IN THE PERISINUSOIDAL SPACE IN LIVER. HSCS FACILITATE HEPATOCYTES INTERACTIONS VIA RELEASING SOLUBLE INFLAMMATORY FACTORS AND PRODUCING EXTRACELLULAR MATRIX. HSCS CAN BE ACTIVATED IN RESPONSE TO LIVER INJURY, AND THEY DIFFERENTIATE TO MYOFIBROBLASTS, WHICH GREATLY CONTRIBUTE TO THE FIBROGENESIS PROCESS. VARIOUS EPIGENETIC PROCEDURES, INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND FORMATION OF PARTICULAR CHROMATIN STRUCTURE, PLAY CRUCIAL ROLES IN THE GENE TRANSCRIPTIONAL EXPRESSION IN HSCS, REGULATING VARIOUS VITAL PROCESSES. FOR INSTANCE, EPIGENETIC MODULATION ON THE PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR GAMMA (PPAR-GAMMA) GENE PROMOTER ACCOUNTS FOR HSC DIFFERENTIATION THROUGH INTERACTING PATHWAYS. ABERRANT EXPRESSION OF A SERIES OF HISTONES AND CHEMOKINES IN ACTIVATED HSCS CAN AGGRAVATE INFLAMMATION AND OXIDATIVE STRESS, WHICH IN TURN PROMOTES DIFFERENTIATION OF HSCS TO MYOFIBROBLASTS AND ENHANCES THE WHOLE FIBROGENESIS PROCESS. DEGRADATION OF EXTRACELLULAR MATRIX IS ALSO REGULATED THROUGH EPIGENETIC MODULATION ON MATRIX ASSOCIATED ENZYMES. MOREOVER, FIBROSIS-RELATED EPIGENETIC MODIFICATIONS IN THE PARENTAL GENERATION MAY BE INHERITED TO THEIR OFFSPRING. IN THIS REVIEW, WE FIRSTLY SUMMARIZE THE VITAL EPIGENETIC MODIFICATIONS OF FIBROSIS-RELATED GENES IN HSCS, AND HIGHLIGHT SPECIFIC NUCLEIC ACID SEQUENCES AND STRUCTURES IN GENE PROMOTERS AS IMPORTANT ACTION SITES, WHICH MAY PROVIDE INDICATORS FOR LIVER FIBROSIS DIAGNOSIS IN THE FUTURE. 2013 13 4132 33 MECHANISMS OF HEPATIC FIBROGENESIS. SUBSTANTIAL IMPROVEMENTS IN THE TREATMENT OF CHRONIC LIVER DISEASE HAVE ACCELERATED INTEREST IN UNCOVERING THE MECHANISMS UNDERLYING HEPATIC FIBROSIS AND ITS RESOLUTION. ACTIVATION OF RESIDENT HEPATIC STELLATE CELLS INTO PROLIFERATIVE, CONTRACTILE, AND FIBROGENIC CELLS IN LIVER INJURY REMAINS A DOMINANT THEME DRIVING THE FIELD. HOWEVER, SEVERAL NEW AREAS OF RAPID PROGRESS IN THE PAST 5-10 YEARS ALSO HAVE TAKEN ROOT, INCLUDING: (1) IDENTIFICATION OF DIFFERENT FIBROGENIC POPULATIONS APART FROM RESIDENT STELLATE CELLS, FOR EXAMPLE, PORTAL FIBROBLASTS, FIBROCYTES, AND BONE-MARROW-DERIVED CELLS, AS WELL AS CELLS DERIVED FROM EPITHELIAL MESENCHYMAL TRANSITION; (2) EMERGENCE OF STELLATE CELLS AS FINELY REGULATED DETERMINANTS OF HEPATIC INFLAMMATION AND IMMUNITY; (3) ELUCIDATION OF MULTIPLE PATHWAYS CONTROLLING GENE EXPRESSION DURING STELLATE CELL ACTIVATION INCLUDING TRANSCRIPTIONAL, POST-TRANSCRIPTIONAL, AND EPIGENETIC MECHANISMS; (4) RECOGNITION OF DISEASE-SPECIFIC PATHWAYS OF FIBROGENESIS; (5) RE-EMERGENCE OF HEPATIC MACROPHAGES AS DETERMINANTS OF MATRIX DEGRADATION IN FIBROSIS RESOLUTION AND THE IMPORTANCE OF MATRIX CROSS-LINKING AND SCAR MATURATION IN DETERMINING REVERSIBILITY; AND (6) HINTS THAT HEPATIC STELLATE CELLS MAY CONTRIBUTE TO HEPATIC STEM CELL BEHAVIOR, CANCER, AND REGENERATION. CLINICAL AND TRANSLATIONAL IMPLICATIONS OF THESE ADVANCES HAVE BECOME CLEAR, AND HAVE BEGUN TO IMPACT SIGNIFICANTLY ON THE MANAGEMENT AND OUTLOOK OF PATIENTS WITH CHRONIC LIVER DISEASE. 2008 14 2502 27 EPIGENETICS AND LIVER FIBROSIS. LIVER FIBROSIS ARISES BECAUSE PROLONGED INJURY COMBINED WITH EXCESSIVE SCAR DEPOSITION WITHIN HEPATIC PARENCHYMA ARISING FROM OVERACTIVE WOUND HEALING RESPONSE MEDIATED BY ACTIVATED MYOFIBROBLASTS. FIBROSIS IS THE COMMON END POINT FOR ANY TYPE OF CHRONIC LIVER INJURY INCLUDING ALCOHOLIC LIVER DISEASE, NONALCOHOLIC FATTY LIVER DISEASE, VIRAL HEPATITIS, AND CHOLESTATIC LIVER DISEASES. ALTHOUGH GENETIC INFLUENCES ARE IMPORTANT, IT IS EPIGENETIC MECHANISMS THAT HAVE BEEN SHOWN TO ORCHESTRATE MANY ASPECTS OF FIBROGENESIS IN THE LIVER. NEW DISCOVERIES IN THE FIELD ARE LEADING TOWARD THE DEVELOPMENT OF EPIGENETIC BIOMARKERS AND TARGETED THERAPIES. THIS REVIEW CONSIDERS EPIGENETIC MECHANISMS AS WELL AS RECENT ADVANCES IN EPIGENETIC PROGRAMMING IN THE CONTEXT OF HEPATIC FIBROSIS. 2017 15 4613 41 NEOVASCULARIZATION IS A KEY FEATURE OF LIVER FIBROSIS PROGRESSION: ANTI-ANGIOGENESIS AS AN INNOVATIVE WAY OF LIVER FIBROSIS TREATMENT. LIVER FIBROSIS AFFECTS OVER 100 MILLION PEOPLE IN THE WORLD; IT REPRESENTS A MULTIFACTORIAL, FIBRO-INFLAMMATORY DISORDER CHARACTERIZED BY EXACERBATED PRODUCTION OF EXTRACELLULAR MATRIX WITH CONSEQUENT ABERRATION OF HEPATIC TISSUE. THE AETIOLOGY OF THIS DISEASE IS VERY COMPLEX AND SEEMS TO INVOLVE A BROAD SPECTRUM OF FACTORS INCLUDING THE LIFESTYLE, ENVIRONMENT FACTORS, GENES AND EPIGENETIC CHANGES. MORE EVIDENCES INDICATE THAT ANGIOGENESIS, A PROCESS CONSISTING IN THE FORMATION OF NEW BLOOD VESSELS FROM PRE-EXISTING VESSELS, PLAYS A CRUCIAL ROLE IN THE PROGRESSION OF LIVER FIBROSIS. CENTRAL TO THE PATHOGENESIS OF LIVER FIBROSIS IS THE HEPATIC STELLATE CELLS (HSCS) WHICH REPRESENT A CROSSROAD AMONG INFLAMMATION, FIBROSIS AND ANGIOGENESIS. QUIESCENT HSCS CAN BE STIMULATED BY A HOST OF GROWTH FACTORS, PRO-INFLAMMATORY MEDIATORS PRODUCED BY DAMAGED RESIDENT LIVER CELL TYPES, AS WELL AS BY HYPOXIA, CONTRIBUTING TO NEOANGIOGENESIS, WHICH IN TURN CAN BE A BRIDGE BETWEEN ACUTE AND CHRONIC INFLAMMATION. AS MATTER OF FACT, STUDIES DEMONSTRATED THAT NEUTRALIZATION OF VASCULAR ENDOTHELIAL GROWTH FACTOR AS WELL AS OTHER PROANGIOGENIC AGENTS CAN ATTENUATE THE PROGRESSION OF LIVER FIBROSIS. WITH THIS REVIEW, OUR INTENT IS TO DISCUSS THE CAUSE AND THE ROLE OF ANGIOGENESIS IN LIVER FIBROSIS FOCUSING ON THE CURRENT KNOWLEDGE ABOUT THE IMPACT OF ANTI-ANGIOGENETIC THERAPIES IN THIS PATHOLOGY. 2020 16 3931 30 LIVER INJURY AND THE ACTIVATION OF THE HEPATIC MYOFIBROBLASTS. LIVER FIBROSIS IS A WOUND HEALING PROCESS, THE END RESULT OF CHRONIC LIVER INJURY ELICITED BY DIFFERENT NOXIOUS STIMULI. ACTIVATED HEPATIC STELLATE CELLS OR MYOFIBROBLASTS AND PORTAL MYOFIBROBLASTS ARE CONSIDERED AS THE MAIN PRODUCERS OF THE EXTRACELLULAR MATRIX IN THE LIVER. UPON LIVER INJURY THE QUIESCENT STELLATE CELLS TRANSDIFFERENTIATE INTO MYOFIBROBLASTS A PROCESS HIGHLIGHTED BY THE LOSS OF VITAMIN A STORES, UPREGULATION OF INTERSTITIAL TYPE COLLAGENS, SMOOTH MUSCLE ALPHA ACTIN, MATRIX METALLOPROTEINASES, PROTEOGLYCANS, AND THE INDUCTION OF CELL SURVIVAL PATHWAYS. ACTIVATION OF HEPATIC STELLATE CELLS IS A RESULT OF A COMPLEX INTERPLAY BETWEEN THE PARENCHYMAL CELLS, IMMUNE CELLS, EXTRACELLULAR MATRIX MECHANICS AND EXTRAHEPATIC MILIEU SUCH AS THE GUT MICROBIOME. IN THIS REVIEW WE WILL FOCUS ON THE PATHOMECHANISM OF STELLATE CELL ACTIVATION FOLLOWING CHRONIC LIVER INJURY; WITH THE AIM OF IDENTIFYING POSSIBLE TREATMENT TARGETS FOR ANTI-FIBROGENIC AGENTS. 2013 17 4980 37 PATHOPHYSIOLOGY OF LIVER FIBROSIS. PROGRESSIVE ACCUMULATION OF FIBRILLAR EXTRACELLULAR MATRIX (ECM) IN THE LIVER IS THE CONSEQUENCE OF REITERATED LIVER TISSUE DAMAGE DUE TO INFECTIVE (MOSTLY HEPATITIS B AND C VIRUSES), TOXIC/DRUG-INDUCED, METABOLIC AND AUTOIMMUNE CAUSES, AND THE RELATIVE CHRONIC ACTIVATION OF THE WOUND-HEALING REACTION. THE PROCESS MAY RESULT IN CLINICALLY EVIDENT LIVER CIRRHOSIS AND HEPATIC FAILURE. ALTHOUGH CIRRHOSIS IS THE COMMON RESULT OF PROGRESSIVE FIBROGENESIS, THERE ARE DISTINCT PATTERNS OF FIBROTIC DEVELOPMENT RELATED TO THE UNDERLYING DISORDERS CAUSING THE FIBROSIS. THESE DIFFERENT PATTERNS OF FIBROGENIC EVOLUTION ARE RELATED TO DIFFERENT FACTORS AND PARTICULARLY: (1) THE TOPOGRAPHIC LOCALIZATION OF TISSUE DAMAGE, (2) THE RELATIVE CONCENTRATION OF PROFIBROGENIC FACTORS AND (3) THE PREVALENT PROFIBROGENIC MECHANISM(S). THE MECHANISMS RESPONSIBLE FOR THE FIBROGENIC EVOLUTION OF CHRONIC LIVER DISEASES CAN BE SUMMARIZED IN THREE MAIN GROUPS: CHRONIC ACTIVATION OF THE WOUND-HEALING REACTION, OXIDATIVE STRESS-RELATED MOLECULAR MECHANISMS, AND THE DERANGEMENT OF THE SO-CALLED 'EPITHELIAL-MESENCHYMAL' INTERACTION LEADING TO THE GENERATION OF REACTIVE CHOLANGIOCYTES AND PERIBILIARY FIBROSIS. MOST OF THE KNOWLEDGE ON THE CELL AND MOLECULAR BIOLOGY OF HEPATIC FIBROSIS DERIVES FROM IN VITRO STUDIES EMPLOYING CULTURE OF ACTIVATED HEPATIC STELLATE CELLS ISOLATED FROM RAT, MOUSE OR HUMAN LIVER. IT IS NOW EVIDENT THAT OTHER ECM-PRODUCING CELLS, I.E. FIBROBLASTS AND MYOFIBROBLASTS OF THE PORTAL TRACT AND CIRCULATING 'FIBROCYTES', ARE LIKELY TO CONTRIBUTE TO LIVER FIBROSIS. MORE RECENTLY, THE ATTENTION IS PROGRESSIVELY SHIFTING TO THE PROFIBROTIC MICROENVIRONMENT OF THE LIVER WITH INCREASING INTEREST FOR THE ROLE OF IMMUNE CELLS AND SPECIFIC SUBSETS OF MACROPHAGES REGULATING THE PROGRESSION OR THE REGRESSION OF FIBROSIS, THE ROLE OF INTESTINAL MICROBIOTA AND THE INFLUENCE OF TISSUE STIFFNESS. OTHER MAJOR AREAS OF DEVELOPMENT INCLUDE THE ROLE OF TISSUE HYPOXIA AND THE ESTABLISHMENT OF AN ANAEROBIC PROINFLAMMATORY ENVIRONMENT AND THE INFLUENCE OF EPIGENETIC MODIFICATION IN CONDITIONING THE PROGRESSION OF FIBROSIS. 2015 18 1255 40 CURRENT STATUS OF NOVEL ANTIFIBROTIC THERAPIES IN PATIENTS WITH CHRONIC LIVER DISEASE. FIBROSIS ACCUMULATION IS A DYNAMIC PROCESS RESULTING FROM A WOUND-HEALING RESPONSE TO ACUTE OR CHRONIC LIVER INJURY OF ALL CAUSES. THE CASCADE STARTS WITH HEPATOCYTE NECROSIS AND APOPTOSIS, WHICH INSTIGATE INFLAMMATORY SIGNALING BY CHEMOKINES AND CYTOKINES, RECRUITMENT OF IMMUNE CELL POPULATIONS, AND ACTIVATION OF FIBROGENIC CELLS, CULMINATING IN THE DEPOSITION OF EXTRACELLULAR MATRIX. THESE KEY ELEMENTS, ALONG WITH PATHWAYS OF TRANSCRIPTIONAL AND EPIGENETIC REGULATION, REPRESENT FERTILE THERAPEUTIC TARGETS. NEW THERAPIES INCLUDE DRUGS SPECIFICALLY DESIGNED AS ANTIFIBROTICS, AS WELL AS DRUGS ALREADY AVAILABLE WITH WELL-ESTABLISHED SAFETY PROFILES, WHOSE MECHANISM OF ACTION MAY ALSO BE ANTIFIBROTIC. AT THE SAME TIME, THE DEVELOPMENT OF NONINVASIVE FIBROGENIC MARKERS, AND TECHNIQUES (E.G. FIBROSCAN), AS WELL AS COMBINED SCORING SYSTEMS INCORPORATING SERUM AND CLINICAL FEATURES WILL ALLOW IMPROVED ASSESSMENT OF THERAPY RESPONSE. IN AGGREGATE, THE ADVANCES IN THE ELUCIDATION OF THE BIOLOGY OF FIBROSIS, COMBINED WITH IMPROVED TECHNOLOGIES FOR ASSESSMENT WILL PROVIDE A COMPREHENSIVE FRAMEWORK FOR DESIGN OF ANTIFIBROTICS AND THEIR ANALYSIS IN WELL-DESIGNED CLINICAL TRIALS. THESE EFFORTS MAY ULTIMATELY YIELD SUCCESS IN HALTING THE PROGRESSION OF, OR REVERSING, LIVER FIBROSIS. 2011 19 3244 35 HEPATIC STELLATE CELLS AND EXTRACELLULAR MATRIX IN HEPATOCELLULAR CARCINOMA: MORE COMPLICATED THAN EVER. HEPATOCELLULAR CARCINOMA (HCC) IS THE FIFTH MOST COMMON CANCER WORLDWIDE AND THE THIRD LEADING CAUSE OF CANCER DEATH. RECENT EPIDEMIOLOGICAL DATA INDICATE THAT THE MORTALITY RATE OF HCC WILL DOUBLE OVER THE NEXT DECADES IN THE USA AND EUROPE. LIVER CANCER PROGRESSES IN A LARGE PERCENTAGE OF CASES DURING THE CLINICAL COURSE OF CHRONIC FIBRO-INFLAMMATORY LIVER DISEASES LEADING TO CIRRHOSIS. THEREFORE, HCC DEVELOPMENT IS REGARDED AS THE RESULT OF DIFFERENT ENVIRONMENTAL RISK FACTORS EACH INVOLVING DIFFERENT GENETIC, EPIGENETIC- AND CHROMOSOMAL ALTERATIONS AND GENE MUTATIONS. DURING TUMOUR PROGRESSION, THE MALIGNANT HEPATOCYTES AND THE ACTIVATED HEPATIC STELLATE CELLS ARE ACCOMPANIED BY CANCER-ASSOCIATED FIBROBLASTS, MYOFIBROBLASTS AND IMMUNE CELLS GENERALLY CALLED TUMOUR STROMAL CELLS. THIS NEW AND DYNAMIC MILIEU FURTHER ENHANCES THE RESPONSIVENESS OF TUMOUR CELLS TOWARDS SOLUBLE MEDIATORS SECRETED BY TUMOUR STROMAL CELLS, THUS DIRECTLY AFFECTING THE MALIGNANT HEPATOCYTES. THIS RESULTS IN ALTERED MOLECULAR PATHWAYS WITH CELL PROLIFERATION AS THE MOST IMPORTANT MECHANISM OF LIVER CANCER PROGRESSION. GIVEN THIS CONTEXTUAL COMPLEXITY, IT IS OF UTMOST IMPORTANCE TO CHARACTERIZE THE MOLECULAR PATHOGENESIS OF HCC, AND TO IDENTIFY THE DOMINANT PATHWAYS/DRIVERS AND ABERRANT SIGNALLING PATHWAYS. THIS WILL ALLOW AN EFFECTIVE THERAPY FOR HCC THAT SHOULD COMBINE STRATEGIES AFFECTING BOTH CANCER AND THE TUMOUR STROMAL CELLS. THIS REVIEW PROVIDES AN OVERVIEW OF THE RECENT CHALLENGES AND ISSUES REGARDING HEPATIC STELLATE CELLS, EXTRACELLULAR MATRIX DYNAMICS, LIVER FIBROSIS/CIRRHOSIS AND THERAPY, TUMOUR MICROENVIRONMENT AND HCC. 2014 20 2691 30 EVOLUTION OF HEPATIC FIBROSIS RESEARCH. MOLECULAR ANALYSIS OF HEPATIC FIBROGENESIS HAS PROGRESSED WITH RESPECT TO BOTH FIBROSIS PROGRESSION AND REGRESSION BY USING CELL BIOLOGICAL, MOLECULAR BIOLOGICAL AND (EPI)GENETIC APPROACHES. RECENT RESEARCHES HAVE REVEALED SOURCES OF COLLAGEN-PRODUCING CELLS OTHER THAN HEPATIC STELLATE CELLS IN THE LIVER, AND THE INVOLVEMENT OF THE INNATE IMMUNE SYSTEM AND OXIDATIVE STRESS IN THE FIBROTIC PROCESS HAS ATTRACTED NEW ATTENTION. TOGETHER WITH THESE ADVANCEMENTS IN BASIC KNOWLEDGE ON THE CELLULAR AND MOLECULAR BIOLOGY OF HEPATIC FIBROSIS, CLINICAL RESEARCHES HAVE LINKED THE CLARIFICATION OF THE RELATIONSHIP BETWEEN PROGRESSION OF THE FIBROSIS STAGE AND THERAPEUTIC EFFICACY FOR CHRONIC VIRAL HEPATITIS AND NON-ALCOHOLIC STEATOHEPATITIS AND VALIDATION OF THE REGRESSION OF ADVANCED FIBROSIS, EVEN CIRRHOSIS, OF APPROPRIATE THERAPIES USING MODERN MEDICINES. FURTHERMORE, NON-INVASIVE ASSESSMENT OF LIVER FIBROSIS USING AN ULTRASOUND-BASED MODALITY HAS BECOME A FOCUS IN THE CLINICAL DIAGNOSIS OF LIVER FIBROSIS INSTEAD OF LIVER BIOPSY. TAKEN TOGETHER, LIVER FIBROSIS RESEARCH HAS BEEN EVOLVING BOTH BASICALLY AND CLINICALLY IN THE PAST THREE DECADES. 2011