1 3184 125 HARNESSING METABOLISM OF HEPATIC MACROPHAGES TO AID LIVER REGENERATION. LIVER REGENERATION IS A DYNAMIC AND REGULATED PROCESS THAT INVOLVES INFLAMMATION, GRANULATION, AND TISSUE REMODELING. HEPATIC MACROPHAGES, ABUNDANTLY DISTRIBUTED IN THE LIVER, ARE ESSENTIAL COMPONENTS THAT ACTIVELY PARTICIPATE IN EACH STEP TO ORCHESTRATE LIVER REGENERATION. IN THE HOMEOSTATIC LIVER, RESIDENT MACROPHAGES (KUPFFER CELLS) ACQUIRE A TOLEROGENIC PHENOTYPE AND CONTRIBUTE TO IMMUNOLOGICAL TOLERANCE. FOLLOWING TOXICITY-INDUCED DAMAGE OR PHYSICAL RESECTION, KUPFFER CELLS AS WELL AS MONOCYTE-DERIVED MACROPHAGES CAN BE ACTIVATED AND PROMOTE AN INFLAMMATORY PROCESS THAT SUPPORTS THE SURVIVAL AND ACTIVATION OF HEPATIC MYOFIBROBLASTS AND THUS PROMOTES SCAR TISSUE FORMATION. SUBSEQUENTLY, THESE MACROPHAGES, IN TURN, EXHIBIT THE ANTI-INFLAMMATORY EFFECTS CRITICAL TO EXTRACELLULAR MATRIX REMODELING DURING THE RESOLUTION STAGE. HOWEVER, CONTINUOUS DAMAGE-INDUCED CHRONIC INFLAMMATION GENERALLY LEADS TO HEPATIC MACROPHAGE DYSFUNCTION, WHICH EXACERBATES HEPATOCELLULAR INJURY AND TRIGGERS FURTHER LIVER FIBROSIS AND EVEN CIRRHOSIS. EMERGING MACROPHAGE-TARGETING STRATEGIES HAVE SHOWN EFFICACY IN BOTH PRECLINICAL AND CLINICAL STUDIES. INCREASING EVIDENCE INDICATES THAT METABOLIC REWIRING PROVIDES SUBSTRATES FOR EPIGENETIC MODIFICATION, WHICH ENDOWS MONOCYTES/MACROPHAGES WITH PROLONGED "INNATE IMMUNE MEMORY". THEREFORE, IT IS REASONABLE TO CONCEIVE NOVEL THERAPEUTIC STRATEGIES FOR METABOLICALLY REPROGRAMMING MACROPHAGES AND THUS MEDIATE A HOMEOSTATIC OR REPARATIVE PROCESS FOR HEPATIC INFLAMMATION MANAGEMENT AND LIVER REGENERATION. 2023 2 3931 25 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 3 3245 24 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 4 4749 31 NOVEL PROSPECTS FOR SCARLESS WOUND HEALING: THE ROLES OF MYOFIBROBLASTS AND ADIPOCYTES. DISTURBANCES OR DEFECTS IN THE PROCESS OF WOUND REPAIR CAN DISRUPT THE DELICATE BALANCE OF CELLS AND MOLECULES NECESSARY FOR COMPLETE WOUND HEALING, THUS LEADING TO CHRONIC WOUNDS OR FIBROTIC SCARS. MYOFIBROBLASTS ARE ONE OF THE MOST IMPORTANT CELLS INVOLVED IN FIBROTIC SCARS, AND REPROGRAMMING PROVIDES A POTENTIAL AVENUE TO INCREASE MYOFIBROBLAST CLEARANCE. ALTHOUGH MYOFIBROBLASTS HAVE LONG BEEN RECOGNIZED AS TERMINALLY DIFFERENTIATED CELLS, RECENT STUDIES HAVE SHOWN THAT MYOFIBROBLASTS HAVE THE CAPACITY TO BE REPROGRAMMED INTO ADIPOCYTES. THIS REVIEW INTENDS TO SUMMARIZE THE POTENTIAL OF REPROGRAMMING MYOFIBROBLASTS INTO ADIPOCYTES. WE WILL DISCUSS MYOFIBROBLAST LINEAGE TRACING, AS WELL AS THE KNOWN MECHANISMS UNDERLYING ADIPOCYTE REGENERATION FROM MYOFIBROBLASTS. IN ADDITION, WE INVESTIGATED DIFFERENT CHANGES IN MYOFIBROBLAST GENE EXPRESSION, TRANSCRIPTIONAL REGULATORS, SIGNALLING PATHWAYS AND EPIGENETIC REGULATORS DURING SKIN WOUND HEALING. IN THE FUTURE, MYOFIBROBLAST REPROGRAMMING IN WOUND HEALING WILL BE BETTER UNDERSTOOD AND APPRECIATED, WHICH MAY PROVIDE NEW IDEAS FOR THE TREATMENT OF SCARLESS WOUND HEALING. 2022 5 6206 33 THE INFLUENCE OF TISSUE SPATIAL GEOMETRY AND FUNCTIONAL ORGANISATION ON LIVER REGENERATION. THE ADULT LIVER EXERTS CRUCIAL FUNCTIONS, INCLUDING NUTRIENT METABOLISM AND STORAGE, BILE PRODUCTION AND DRUG DETOXIFICATION. THESE COMPLEX FUNCTIONS EXPOSE THE LIVER TO CONSTANT DAMAGE INDUCED BY TOXINS, METABOLIC INTERMEDIATES AND OXIDATIVE STRESS. HOWEVER, THE ADULT LIVER EXHIBITS AN EXCEPTIONAL REGENERATIVE POTENTIAL, WHICH ALLOWS FAST AND EFFICIENT RESTORATION OF TISSUE ARCHITECTURE AND FUNCTION BOTH AFTER TISSUE RESECTION AND TOXIC DAMAGE. TO ACCOMPLISH ITS VITAL ROLE, THE LIVER SHOWS A PECULIAR TISSUE ARCHITECTURE INTO FUNCTIONAL UNITS, WHICH FOLLOW THE GRADIENT OF OXYGEN AND NUTRIENTS WITHIN THE PARENCHYMA. MUCH LESS IS KNOWN ABOUT THE INFLUENCE OF TISSUE SPATIAL GEOMETRY AND FUNCTIONAL ORGANISATION ON ADULT LIVER REGENERATION. HERE I EXAMINE THE EXPERIMENTAL EVIDENCE IN MOUSE MODELS SHOWING THAT THE SPATIAL ORGANISATION OF THE EPITHELIAL AND MESENCHYMAL COMPARTMENTS PLAYS A KEY ROLE IN LIVER REGENERATION AND FAVOURS THE ESTABLISHMENT OF REGENERATIVE ADULT LIVER PROGENITORS FOLLOWING LIVER INJURY. I ALSO DISCUSS THE ADVANTAGES AND LIMITATIONS OF HUMAN AND MOUSE 3D HEPATIC ORGANOID SYSTEMS, WHICH RECAPITULATE KEY ASPECTS OF LIVER FUNCTION AND ARCHITECTURE, AS MODELS OF LIVER REGENERATION AND DISEASE. FINALLY, I ANALYSE THE ROLE OF THE YAP/TAZ TRANSCRIPTIONAL CO-ACTIVATORS AS A CENTRAL HUB SENSING THE EXTRA-CELLULAR MATRIX (ECM), METABOLIC AND EPIGENETIC REMODELLING THAT REGULATE LIVER REGENERATION AND PROMOTE LIVER DISEASE, SUCH AS FIBROSIS, CHRONIC LIVER DISEASE AND LIVER CANCER. TOGETHER, THE FINDINGS SUMMARISED HERE DEMONSTRATE THAT LOCAL PHYSICAL AND FUNCTIONAL CELLULAR INTERACTIONS DETERMINED BY THE LIVER PECULIAR SPATIAL GEOMETRY, PLAY A CRUCIAL ROLE IN LIVER REGENERATION, AND THAT THEIR ALTERATIONS HAVE IMPORTANT IMPLICATIONS FOR HUMAN LIVER DISEASE. 2022 6 5939 43 TARGETING MECHANOTRANSDUCTION AT THE TRANSCRIPTIONAL LEVEL: YAP AND BRD4 ARE NOVEL THERAPEUTIC TARGETS FOR THE REVERSAL OF LIVER FIBROSIS. LIVER FIBROSIS IS THE RESULT OF A DEREGULATED WOUND HEALING PROCESS CHARACTERIZED BY THE EXCESSIVE DEPOSITION OF EXTRACELLULAR MATRIX. HEPATIC STELLATE CELLS (HSCS), WHICH ARE ACTIVATED IN RESPONSE TO LIVER INJURY, ARE THE MAJOR SOURCE OF EXTRACELLULAR MATRIX AND DRIVE THE WOUND HEALING PROCESS. HOWEVER, CHRONIC LIVER DAMAGE LEADS TO PERPETUAL HSC ACTIVATION, PROGRESSIVE FORMATION OF PATHOLOGICAL SCAR TISSUE AND ULTIMATELY, CIRRHOSIS AND ORGAN FAILURE. HSC ACTIVATION IS TRIGGERED LARGELY IN RESPONSE TO MECHANOSIGNALING FROM THE MICROENVIRONMENT, WHICH INDUCES A PROFIBROTIC NUCLEAR TRANSCRIPTION PROGRAM THAT PROMOTES HSC PROLIFERATION AND EXTRACELLULAR MATRIX SECRETION THEREBY SETTING UP A POSITIVE FEEDBACK LOOP LEADING TO MATRIX STIFFENING AND SELF-SUSTAINED, PATHOLOGICAL, HSC ACTIVATION. DESPITE THE SIGNIFICANT PROGRESS IN OUR UNDERSTANDING OF LIVER FIBROSIS, THE MOLECULAR MECHANISMS THROUGH WHICH THE EXTRACELLULAR MATRIX PROMOTES HSC ACTIVATION ARE NOT WELL UNDERSTOOD AND NO EFFECTIVE THERAPIES HAVE BEEN APPROVED TO DATE THAT CAN TARGET THIS EARLY, REVERSIBLE, STAGE IN LIVER FIBROSIS. SEVERAL NEW LINES OF INVESTIGATION NOW PROVIDE IMPORTANT INSIGHT INTO THIS AREA OF STUDY AND IDENTIFY TWO NUCLEAR TARGETS WHOSE INHIBITION HAS THE POTENTIAL OF REVERSING LIVER FIBROSIS BY INTERFERING WITH HSC ACTIVATION: YES-ASSOCIATED PROTEIN (YAP), A TRANSCRIPTIONAL CO-ACTIVATOR AND EFFECTOR OF THE MECHANOSENSITIVE HIPPO PATHWAY, AND BROMODOMAIN-CONTAINING PROTEIN 4 (BRD4), AN EPIGENETIC REGULATOR OF GENE EXPRESSION. YAP AND BRD4 ACTIVITY IS INDUCED IN RESPONSE TO MECHANICAL STIMULATION OF HSCS AND EACH PROTEIN INDEPENDENTLY CONTROLS WAVES OF EARLY GENE EXPRESSION NECESSARY FOR HSC ACTIVATION. SIGNIFICANTLY, INHIBITION OF EITHER PROTEIN CAN REVERT THE CHRONIC ACTIVATION OF HSCS AND IMPEDE PATHOLOGICAL PROGRESSION OF LIVER FIBROSIS IN CLINICALLY RELEVANT MODEL SYSTEMS. IN THIS REVIEW WE WILL DISCUSS THE ROLES OF THESE NUCLEAR CO-ACTIVATORS IN HSC ACTIVATION, THEIR MECHANISM OF ACTION IN THE FIBROTIC PROCESS IN THE LIVER AND OTHER ORGANS, AND THE POTENTIAL OF TARGETING THEIR ACTIVITY WITH SMALL MOLECULE DRUGS FOR FIBROSIS REVERSAL. 2016 7 4448 39 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 2817 30 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 9 4976 33 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 10 4132 34 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 11 1300 33 DEDIFFERENTIATION AND IN VIVO REPROGRAMMING OF COMMITTED CELLS IN WOUND REPAIR (REVIEW). ACCUMULATING EVIDENCE HAS SHOWN THAT CELL DEDIFFERENTIATION OR REPROGRAMMING IS A PIVOTAL PROCEDURE FOR ANIMALS TO DEAL WITH INJURY AND PROMOTE ENDOGENOUS TISSUE REPAIR. TISSUE DAMAGE IS A CRITICAL FACTOR THAT TRIGGERS CELL DEDIFFERENTIATION OR REPROGRAMMING IN VIVO. BY CONTRAST, MICROENVIRONMENTAL CHANGES, INCLUDING THE LOSS OF STEM CELLS, HYPOXIA, CELL SENESCENCE, INFLAMMATION AND IMMUNITY, CAUSED BY TISSUE DAMAGE CAN RETURN CELLS TO AN UNSTABLE STATE. IF THE WOUND PERSISTS IN THE LONG?TERM DUE TO CHRONIC DAMAGE, THEN DEDIFFERENTIATION OR REPROGRAMMING OF THE SURROUNDING CELLS MAY LEAD TO CARCINOGENESIS. IN RECENT YEARS, EXTENSIVE RESEARCH HAS BEEN PERFORMED INVESTIGATING CELL DEDIFFERENTIATION OR REPROGRAMMING IN VIVO, WHICH CAN HAVE SIGNIFICANT IMPLICATIONS FOR WOUND REPAIR, TREATMENT AND PREVENTION OF CANCER IN THE FUTURE. THE CURRENT REVIEW SUMMARIZES THE MOLECULAR EVENTS THAT ARE KNOWN TO DRIVE CELL DEDIFFERENTIATION DIRECTLY FOLLOWING TISSUE INJURY AND THE EFFECTS OF EPIGENETIC MODIFICATION ON DEDIFFERENTIATION OR REPROGRAMMING IN VIVO. IN ADDITION, THE PRESENT REVIEW EXPLORES THE INTRACELLULAR MECHANISM OF ENDOGENOUS TISSUE REPAIR AND ITS RELATIONSHIP WITH CANCER, WHICH IS ESSENTIAL FOR BALANCING THE RISK BETWEEN TISSUE REPAIR AND MALIGNANT TRANSFORMATION AFTER INJURY. 2022 12 5631 33 SENESCENCE-INFLAMMATORY REGULATION OF REPARATIVE CELLULAR REPROGRAMMING IN AGING AND CANCER. THE INABILITY OF ADULT TISSUES TO TRANSITORILY GENERATE CELLS WITH FUNCTIONAL STEM CELL-LIKE PROPERTIES IS A MAJOR OBSTACLE TO TISSUE SELF-REPAIR. NUCLEAR REPROGRAMMING-LIKE PHENOMENA THAT INDUCE A TRANSIENT ACQUISITION OF EPIGENETIC PLASTICITY AND PHENOTYPE MALLEABILITY MAY CONSTITUTE A REPARATIVE ROUTE THROUGH WHICH HUMAN TISSUES RESPOND TO INJURY, STRESS, AND DISEASE. HOWEVER, TISSUE REJUVENATION SHOULD INVOLVE NOT ONLY THE TRANSIENT EPIGENETIC REPROGRAMMING OF DIFFERENTIATED CELLS, BUT ALSO THE COMMITTED RE-ACQUISITION OF THE ORIGINAL OR ALTERNATIVE COMMITTED CELL FATE. CHRONIC OR UNRESTRAINED EPIGENETIC PLASTICITY WOULD DRIVE AGING PHENOTYPES BY IMPAIRING THE REPAIR OR THE REPLACEMENT OF DAMAGED CELLS; SUCH UNCONTROLLED PHENOMENA OF IN VIVO REPROGRAMMING MIGHT ALSO GENERATE CANCER-LIKE CELLULAR STATES. WE HEREIN PROPOSE THAT THE ABILITY OF SENESCENCE-ASSOCIATED INFLAMMATORY SIGNALING TO REGULATE IN VIVO REPROGRAMMING CYCLES OF TISSUE REPAIR OUTLINES A THRESHOLD MODEL OF AGING AND CANCER. THE DEGREE OF SENESCENCE/INFLAMMATION-ASSOCIATED DEVIATION FROM THE HOMEOSTATIC STATE MAY DELINEATE A TYPE OF THRESHOLDING ALGORITHM DISTINGUISHING BENEFICIAL FROM DELETERIOUS EFFECTS OF IN VIVO REPROGRAMMING. FIRST, TRANSIENT ACTIVATION OF NF-KAPPAB-RELATED INNATE IMMUNITY AND SENESCENCE-ASSOCIATED INFLAMMATORY COMPONENTS (E.G., IL-6) MIGHT FACILITATE REPARATIVE CELLULAR REPROGRAMMING IN RESPONSE TO ACUTE INFLAMMATORY EVENTS. SECOND, PARA-INFLAMMATION SWITCHES MIGHT PROMOTE LONG-LASTING BUT REVERSIBLE REFRACTORINESS TO REPARATIVE CELLULAR REPROGRAMMING. THIRD, CHRONIC SENESCENCE-ASSOCIATED INFLAMMATORY SIGNALING MIGHT LOCK CELLS IN HIGHLY PLASTIC EPIGENETIC STATES DISABLED FOR REPARATIVE DIFFERENTIATION. THE CONSIDERATION OF A CELLULAR REPROGRAMMING-CENTERED VIEW OF EPIGENETIC PLASTICITY AS A FUNDAMENTAL ELEMENT OF A TISSUE'S CAPACITY TO UNDERGO SUCCESSFUL REPAIR, AGING DEGENERATION OR MALIGNANT TRANSFORMATION SHOULD PROVIDE CHALLENGING STOCHASTIC INSIGHTS INTO THE CURRENT DETERMINISTIC GENETIC PARADIGM FOR MOST CHRONIC DISEASES, THEREBY INCREASING THE SPECTRUM OF THERAPEUTIC APPROACHES FOR PHYSIOLOGICAL AGING AND CANCER. 2017 13 6757 37 WNT SIGNALING IN LIVER FIBROSIS: PROGRESS, CHALLENGES AND POTENTIAL DIRECTIONS. LIVER FIBROSIS IS A COMMON WOUND-HEALING RESPONSE TO CHRONIC LIVER INJURIES, INCLUDING ALCOHOLIC OR DRUG TOXICITY, PERSISTENT VIRAL INFECTION, AND GENETIC FACTORS. MYOFIBROBLASTIC TRANSDIFFERENTIATION (MTD) IS THE PIVOTAL EVENT DURING LIVER FIBROGENESIS, AND RESEARCH IN THE PAST FEW YEARS HAS IDENTIFIED KEY MEDIATORS AND MOLECULAR MECHANISMS RESPONSIBLE FOR MTD OF HEPATIC STELLATE CELLS (HSCS). HSCS ARE UNDIFFERENTIATED CELLS WHICH PLAY AN IMPORTANT ROLE IN LIVER REGENERATION. RECENT EVIDENCE DEMONSTRATES THAT HSCS DERIVE FROM MESODERM AND AT LEAST IN PART VIA SEPTUM TRANSVERSUM AND MESOTHELIUM, AND HSCS EXPRESS MARKERS FOR DIFFERENT CELL TYPES WHICH DERIVE FROM MULTIPOTENT MESENCHYMAL PROGENITORS. THERE IS A REGULATORY COMMONALITY BETWEEN DIFFERENTIATION OF ADIPOCYTES AND THAT OF HSC, AND THE SHIFT FROM ADIPOGENIC TO MYOGENIC OR NEURONAL PHENOTYPE CHARACTERIZES HSC MTD. CENTRAL OF THIS SHIFT IS A LOSS OF EXPRESSION OF THE MASTER ADIPOGENIC REGULATOR PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR GAMMA (PPARGAMMA). RESTORED EXPRESSION OF PPARGAMMA AND/OR OTHER ADIPOGENIC TRANSCRIPTION GENES CAN REVERSE MYOFIBROBLASTIC HSCS TO DIFFERENTIATED CELLS. VERTEBRATE WNT AND DROSOPHILA WINGLESS ARE HOMOLOGOUS GENES, AND THEIR TRANSLATED PROTEINS HAVE BEEN SHOWN TO PARTICIPATE IN THE REGULATION OF CELL PROLIFERATION, CELL POLARITY, CELL DIFFERENTIATION, AND OTHER BIOLOGICAL ROLES. MORE RECENTLY, WNT SIGNALING IS IMPLICATED IN HUMAN FIBROSING DISEASES, SUCH AS PULMONARY FIBROSIS, RENAL FIBROSIS, AND LIVER FIBROSIS. BLOCKING THE CANONICAL WNT SIGNAL PATHWAY WITH THE CO-RECEPTOR ANTAGONIST DICKKOPF-1 (DKK1) ABROGATES THESE EPIGENETIC REPRESSIONS AND RESTORES THE GENE PPARGAMMA EXPRESSION AND HSC DIFFERENTIATION. THE IDENTIFIED MORPHOGEN MEDIATED EPIGENETIC REGULATION OF PPARGAMMA AND HSC DIFFERENTIATION ALSO SERVES AS NOVEL THERAPEUTIC TARGETS FOR LIVER FIBROSIS AND LIVER REGENERATION. IN CONCLUSION, THE WNT SIGNALING PROMOTES LIVER FIBROSIS BY ENHANCING HSC ACTIVATION AND SURVIVAL, AND WE HEREIN DISCUSS WHAT WE CURRENTLY KNOW AND WHAT WE EXPECT WILL COME IN THIS FIELD IN THE NEXT FUTURE. 2013 14 4501 30 MORPHOGENS AND HEPATIC STELLATE CELL FATE REGULATION IN CHRONIC LIVER DISEASE. HEPATIC STELLATE CELLS (HSC) ARE THE LIVER MESENCHYMAL CELL TYPE WHICH RESPONDS TO HEPATOCELLULAR DAMAGE AND PARTICIPATES IN WOUND HEALING. ALTHOUGH HSC MYOFIBROBLASTIC TRANS-DIFFERENTIATION (ACTIVATION) IS IMPLICATED IN EXCESSIVE EXTRACELLULAR MATRIX DEPOSITION, MOLECULAR UNDERSTANDING OF THIS PHENOTYPIC SWITCH FROM THE VIEWPOINT OF CELL FATE REGULATION IS LIMITED. RECENT STUDIES DEMONSTRATE THE ROLES OF ANTI-ADIPOGENIC MORPHOGENS (WNT, NECDIN, SHH) IN EPIGENETIC REPRESSION OF THE HSC DIFFERENTIATION GENE PPARGAMMA AS A CAUSAL EVENT IN HSC ACTIVATION. THESE MORPHOGENS HAVE POSITIVE CROSS-INTERACTIONS WHICH CONVERGE TO EPIGENETIC REPRESSION OF PPARGAMMA INVOLVING THE METHYL-CPG BINDING PROTEIN MECP2. HOWEVER, THESE MORPHOGENS EXPRESSED BY ACTIVATED HSC MAY ALSO PARTICIPATE IN CROSS-TALK BETWEEN HSC AND HEPATOBLASTS/HEPATOCYTES TO SUPPORT LIVER REGENERATION, AND THEIR ABERRANT REGULATION MAY CONTRIBUTE TO LIVER TUMORIGENESIS. IMPLICATIONS OF HSC-DERIVED MORPHOGENS IN THESE POSSIBILITIES ARE DISCUSSED. 2012 15 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 16 5140 30 POTENTIAL REGULATORS OF THE SENESCENCE-ASSOCIATED SECRETORY PHENOTYPE DURING SENESCENCE AND AGING. SENESCENT CELLS EXPRESS AND SECRETE A VARIETY OF EXTRACELLULAR MODULATORS THAT INCLUDE CYTOKINES, CHEMOKINES, PROTEASES, GROWTH FACTORS, AND SOME ENZYMES ASSOCIATED WITH EXTRACELLULAR MATRIX REMODELING, DEFINED AS THE SENESCENCE-ASSOCIATED SECRETORY PHENOTYPE (SASP). SASP REINFORCES SENESCENT CELL CYCLE ARREST, STIMULATES AND RECRUITS IMMUNE CELLS FOR IMMUNE-MEDIATED CLEARANCE OF POTENTIALLY TUMORIGENIC CELLS, LIMITS OR INDUCES FIBROSIS, AND PROMOTES WOUND HEALING AND TISSUE REGENERATION. ON THE OTHER HAND, SASP MEDIATES CHRONIC INFLAMMATION LEADING TO THE DESTRUCTION OF TISSUE STRUCTURE AND FUNCTION AND STIMULATING THE GROWTH AND SURVIVAL OF TUMOR CELLS. SASP IS HIGHLY HETEROGENEOUS AND THE ROLE OF SASP DEPENDS ON THE CONTEXT. THE REGULATION OF SASP OCCURS AT MULTIPLE LEVELS INCLUDING CHROMATIN REMODELING, TRANSCRIPTION, MRNA TRANSLATION, INTRACELLULAR TRAFFICKING, AND SECRETION. SEVERAL SASP MODULATORS HAVE ALREADY BEEN IDENTIFIED SETTING THE STAGE FOR FUTURE RESEARCH ON THEIR CLINICAL APPLICATIONS. IN THIS REVIEW, WE SUMMARIZE IN DETAIL THE POTENTIAL SIGNALING PATHWAYS THAT TRIGGER AND REGULATE SASP PRODUCTION DURING AGING AND SENESCENCE. 2022 17 2933 45 GENESIS OF THE MYOFIBROBLAST IN LUNG INJURY AND FIBROSIS. TISSUE INJURY INCITES A REPAIR RESPONSE WITH A KEY MESENCHYMAL COMPONENT THAT PROVIDES THE ESSENTIAL CONNECTIVE TISSUE FOR SUBSEQUENT REGENERATION OR PATHOLOGICAL FIBROSIS. THE FIBROBLAST IS THE MAJOR MESENCHYMAL CELL TYPE TO BE IMPLICATED IN THIS CONNECTIVE TISSUE RESPONSE, AND IT IS IN ITS ACTIVATED OR DIFFERENTIATED FORM THAT IT PARTICIPATES IN THE REPAIR PROCESS. THE MYOFIBROBLAST REPRESENTS SUCH AN ACTIVATED MESENCHYMAL CELL AND IS A KEY SOURCE OF EXTRACELLULAR MATRIX AND INFLAMMATORY/FIBROGENIC CYTOKINES AS WELL AS PARTICIPATING IN WOUND CONTRACTION. ALTHOUGH SUCCESSFUL HEALING RESULTS IN GRADUAL DISAPPEARANCE OF MYOFIBROBLASTS, THEIR PERSISTENCE IS ASSOCIATED WITH CHRONIC AND PROGRESSIVE FIBROSIS. THUS, ELUCIDATION OF THE MECHANISM INVOLVED IN THE GENESIS OF THE MYOFIBROBLAST SHOULD PROVIDE INSIGHT INTO BOTH PATHOGENESIS OF CHRONIC FIBROTIC DISEASES AND THERAPEUTIC STRATEGIES FOR THEIR MANAGEMENT AND CONTROL. ALTHOUGH THE FIBROBLAST IS A WELL-DOCUMENTED PROGENITOR CELL FOR THE MYOFIBROBLAST, RECENT STUDIES HAVE SUGGESTED ADDITIONAL PRECURSOR CELLS THAT HAVE THE POTENTIAL TO GIVE RISE TO THE MYOFIBROBLAST. MANY OF THE STUDIES FOCUSED ON MECHANISMS AND FACTORS THAT REGULATE INDUCTION OF ALPHA-SMOOTH MUSCLE ACTIN EXPRESSION, A KEY AND COMMONLY USED MARKER OF THE MYOFIBROBLAST. THESE REVEAL COMPLEX AND MULTIFACTORIAL MECHANISMS INVOLVING TRANSCRIPTIONAL AND EPIGENETIC REGULATION AND IMPLICATING DIVERSE CELL-SIGNALING PATHWAYS, INCLUDING THOSE ACTIVATED BY THE POTENT FIBROGENIC CYTOKINE TRANSFORMING GROWTH FACTOR BETA. DESPITE THESE EXTENSIVE STUDIES, MANY ASPECTS REMAIN POORLY UNDERSTOOD, WITH THE SUGGESTION THAT ADDITIONAL NOVEL MECHANISMS REMAIN TO BE DISCOVERED. FUTURE STUDIES WITH THE HELP OF NEWLY DEVELOPED TECHNICAL ADVANCEMENTS SHOULD EXPEDITE DISCOVERY IN THIS DIRECTION. 2012 18 6413 22 THE STATE OF ART OF REGENERATIVE THERAPY IN CARDIOVASCULAR ISCHEMIC DISEASE: BIOLOGY, SIGNALING PATHWAYS, AND EPIGENETICS OF ENDOTHELIAL PROGENITOR CELLS. ISCHEMIC HEART DISEASE IS CURRENTLY A MAJOR CAUSE OF MORTALITY AND MORBIDITY WORLDWIDE. NEVERTHELESS, THE ACTUAL THERAPEUTIC SCENARIO DOES NOT TARGET MYOCARDIAL CELL REGENERATION AND CONSEQUENTLY, THE PROGRESSION TOWARD THE LATE STAGE OF CHRONIC HEART FAILURE IS COMMON. ENDOTHELIAL PROGENITOR CELLS (EPCS) ARE BONE MARROW-DERIVED STEM CELLS THAT CONTRIBUTE TO THE HOMEOSTASIS OF THE ENDOTHELIAL WALL IN ACUTE AND CHRONIC ISCHEMIC DISEASE. CALCIUM MODULATION AND OTHER MOLECULAR PATHWAYS (NOTCH, VEGFR, AND CXCR4) CONTRIBUTE TO EPC PROLIFERATION AND DIFFERENTIATION. THE PRESENT REVIEW PROVIDES A SUMMARY OF EPC BIOLOGY WITH A PARTICULAR FOCUS ON THE REGULATORY PATHWAYS OF EPCS AND DESCRIBES PROMISING APPLICATIONS FOR CARDIOVASCULAR CELL THERAPY. 2020 19 2323 28 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 20 5950 36 TARGETING THE PROGRESSION OF CHRONIC KIDNEY DISEASE. CHRONIC KIDNEY DISEASE (CKD) IS A DEVASTATING CONDITION THAT IS REACHING EPIDEMIC LEVELS OWING TO THE INCREASING PREVALENCE OF DIABETES MELLITUS, HYPERTENSION AND OBESITY, AS WELL AS AGEING OF THE POPULATION. REGARDLESS OF THE UNDERLYING AETIOLOGY, CKD IS SLOWLY PROGRESSIVE AND LEADS TO IRREVERSIBLE NEPHRON LOSS, END-STAGE RENAL DISEASE AND/OR PREMATURE DEATH. FACTORS THAT CONTRIBUTE TO CKD PROGRESSION INCLUDE PARENCHYMAL CELL LOSS, CHRONIC INFLAMMATION, FIBROSIS AND REDUCED REGENERATIVE CAPACITY OF THE KIDNEY. CURRENT THERAPIES HAVE LIMITED EFFECTIVENESS AND ONLY DELAY DISEASE PROGRESSION, UNDERSCORING THE NEED TO DEVELOP NOVEL THERAPEUTIC APPROACHES TO EITHER STOP OR REVERSE PROGRESSION. PRECLINICAL STUDIES HAVE IDENTIFIED SEVERAL APPROACHES THAT REDUCE FIBROSIS IN EXPERIMENTAL MODELS, INCLUDING TARGETING CYTOKINES, TRANSCRIPTION FACTORS, DEVELOPMENTAL AND SIGNALLING PATHWAYS AND EPIGENETIC MODULATORS, PARTICULARLY MICRORNAS. SOME OF THESE NEPHROPROTECTIVE STRATEGIES ARE NOW BEING TESTED IN CLINICAL TRIALS. LESSONS LEARNED FROM THE FAILURE OF CLINICAL STUDIES OF TRANSFORMING GROWTH FACTOR BETA1 (TGFBETA1) BLOCKADE UNDERSCORE THE NEED FOR ALTERNATIVE APPROACHES TO CKD THERAPY, AS STRATEGIES THAT TARGET A SINGLE PATHOGENIC PROCESS MAY RESULT IN UNEXPECTED NEGATIVE EFFECTS ON SIMULTANEOUSLY OCCURRING PROCESSES. ADDITIONAL PROMISING AVENUES INCLUDE PREVENTING TUBULAR CELL INJURY AND ANTI-FIBROTIC THERAPIES THAT TARGET ACTIVATED MYOFIBROBLASTS, THE MAIN COLLAGEN-PRODUCING CELLS. 2020