1 5432 79 REJUVENATION OF MESENCHYMAL STEM CELLS TO AMELIORATE SKELETAL AGING. ADVANCED AGE IS A SHARED RISK FACTOR FOR MANY CHRONIC AND DEBILITATING SKELETAL DISEASES INCLUDING OSTEOPOROSIS AND PERIODONTITIS. MESENCHYMAL STEM CELLS DEVELOP VARIOUS AGING PHENOTYPES INCLUDING THE ONSET OF SENESCENCE, INTRINSIC LOSS OF REGENERATIVE POTENTIAL AND EXACERBATION OF INFLAMMATORY MICROENVIRONMENT VIA SECRETORY FACTORS. THIS REVIEW ELABORATES ON THE EMERGING CONCEPTS ON THE MOLECULAR AND EPIGENETIC MECHANISMS OF MSC SENESCENCE, SUCH AS THE ACCUMULATION OF OXIDATIVE STRESS, DNA DAMAGE AND MITOCHONDRIAL DYSFUNCTION. SENESCENT MSCS AGGRAVATE LOCAL INFLAMMATION, DISRUPT BONE REMODELING AND BONE-FAT BALANCE, THEREBY CONTRIBUTING TO THE PROGRESSION OF AGE-RELATED BONE DISEASES. VARIOUS REJUVENATION STRATEGIES TO TARGET SENESCENT MSCS COULD PRESENT A PROMISING PARADIGM TO RESTORE SKELETAL AGING. 2023 2 2644 26 EPIGENOMIC DRIVERS OF IMMUNE DYSFUNCTION IN AGING. AGING INEVITABLY LEADS TO REDUCED IMMUNE FUNCTION, LEAVING THE ELDERLY MORE SUSCEPTIBLE TO INFECTIONS, LESS ABLE TO RESPOND TO PATHOGEN CHALLENGES, AND LESS RESPONSIVE TO PREVENTATIVE VACCINATIONS. NO CELL TYPE IS EXEMPT FROM THE RAVAGES OF AGE, AND EXTENSIVE STUDIES HAVE FOUND AGE-RELATED ALTERATIONS IN THE FREQUENCIES AND FUNCTIONS OF BOTH STEM AND PROGENITOR CELLS, AS WELL AS EFFECTOR CELLS OF BOTH THE INNATE AND ADAPTIVE IMMUNE SYSTEMS. THE INTRINSIC FUNCTIONAL REDUCTION IN IMMUNE COMPETENCE IS ALSO ASSOCIATED WITH LOW-GRADE CHRONIC INFLAMMATION, TERMED "INFLAMM-AGING," WHICH FURTHER PERPETUATES IMMUNE DYSFUNCTION. WHILE MANY OF THESE AGE-RELATED CELLULAR CHANGES ARE WELL CHARACTERIZED, UNDERSTANDING THE MOLECULAR CHANGES THAT UNDERPIN THE FUNCTIONAL DECLINE HAS PROVEN MORE DIFFICULT. CHANGES IN CHROMATIN ARE INCREASINGLY APPRECIATED AS A CAUSATIVE MECHANISM OF CELLULAR AND ORGANISMAL AGING ACROSS SPECIES. THESE CHANGES INCLUDE INCREASED GENOMIC INSTABILITY THROUGH LOSS OF HETEROCHROMATIN AND INCREASED DNA DAMAGE, TELOMERE ATTRITION, AND EPIGENETIC ALTERATIONS. IN THIS REVIEW, WE DISCUSS THE CONNECTIONS BETWEEN CHROMATIN, IMMUNOCOMPETENCE, AND THE LOSS OF FUNCTION ASSOCIATED WITH MAMMALIAN IMMUNE AGING. THROUGH UNDERSTANDING THE MOLECULAR EVENTS WHICH UNDERPIN THE PHENOTYPIC CHANGES OBSERVED IN THE AGED IMMUNE SYSTEM, IT IS HOPED THAT THE AGED IMMUNE SYSTEM CAN BE RESTORED TO PROVIDE YOUTHFUL IMMUNITY ONCE MORE. 2019 3 3180 26 HALLMARKS OF AGING IN MACROPHAGES: CONSEQUENCES TO SKIN INFLAMMAGING. THE SKIN IS OUR LARGEST ORGAN AND THE OUTERMOST PROTECTIVE BARRIER. ITS AGING REFLECTS BOTH INTRINSIC AND EXTRINSIC PROCESSES RESULTING FROM THE CONSTANT INSULTS IT IS EXPOSED TO. AGING IN THE SKIN IS ACCOMPANIED BY SPECIFIC EPIGENETIC MODIFICATIONS, ACCUMULATION OF SENESCENT CELLS, REDUCED CELLULAR PROLIFERATION/TISSUE RENEWAL, ALTERED EXTRACELLULAR MATRIX, AND A PROINFLAMMATORY ENVIRONMENT FAVORING UNDESIRABLE CONDITIONS, INCLUDING DISEASE ONSET. MACROPHAGES (MPHI) ARE THE MOST ABUNDANT IMMUNE CELL TYPE IN THE SKIN AND COMPRISE A GROUP OF HETEROGENEOUS AND PLASTIC CELLS THAT ARE KEY FOR SKIN HOMEOSTASIS AND HOST DEFENSE. HOWEVER, THEY HAVE ALSO BEEN IMPLICATED IN ORCHESTRATING CHRONIC INFLAMMATION DURING AGING. SINCE MPHI ARE RELATED TO INNATE AND ADAPTIVE IMMUNITY, IT IS POSSIBLE THAT AGE-MODIFIED SKIN MPHI PROMOTE ADAPTIVE IMMUNITY EXACERBATION AND EXHAUSTION, FAVORING THE EMERGENCE OF PROINFLAMMATORY PATHOLOGIES, SUCH AS SKIN CANCER. IN THIS REVIEW, WE WILL HIGHLIGHT RECENT FINDINGS PERTAINING TO THE EFFECTS OF AGING HALLMARKS OVER MPHI, SUPPORTING THE RECOGNITION OF SUCH CELL TYPES AS A DRIVING FORCE IN SKIN INFLAMMAGING AND AGE-RELATED DISEASES. WE WILL ALSO PRESENT RECENT RESEARCH TARGETING MPHI AS POTENTIAL THERAPEUTIC INTERVENTIONS IN INFLAMMATORY SKIN DISORDERS AND CANCER. 2021 4 1378 20 DEVELOPMENTAL PROGRAMS ARE KEPT ALIVE DURING ADULTHOOD BY STEM CELLS: THE AGING ASPECT. STEM CELLS ARE FUNDAMENTAL FOR LIFE-LONG PRESERVATION OF CELLULAR SOMATIC MAINTENANCE. TISSUE-BORNE STEM CELLS REPLENISH WORN-OUT CRITICAL ELEMENTS. PROVIDED THEY REMAIN FIT OVER LIFETIME, ENDURING STEM CELL ACTIVITIES AVERT THE EMERGENCE OF AGE-ASSOCIATED CHRONIC DEGENERATIVE DISEASES AND PATHOLOGIES. ALTHOUGH EXPERIMENTALLY STILL UNCLEAR, IT IS ASSUMED THAT STEM CELLS RESIDE IN PROTECTED NICHES. FRESHLY ISOLATED MESENCHYMAL STEM CELLS EXHIBIT DONOR-SPECIFIC ABERRATIONS, WHICH CANNOT SOLELY BE ASCRIBED TO DIFFERENCES IN GENETIC BACKGROUND. BESIDES INEVITABLY ACCUMULATING INTRINSIC MODIFICATIONS, THE SYSTEMIC ENVIRONMENT ALSO IMPACTS ON BASIC PROPERTIES OF MESENCHYMAL STEM CELLS SUCH AS THEIR INHERENT MULTI-LINEAGE DIFFERENTIATION POTENTIAL. CHRONIC SYSTEMIC ABERRATIONS OVER TIME COMPRISE UNWHOLESOME INFLUENCES, IN PARTICULAR IN TERMS OF REGENERATION AND REPAIR WHEN STEM CELLS RECAPITULATE DISTINCT DEVELOPMENTAL PROGRAMS. DURING OR THEREAFTER, STEM CELLS CAN DIVERSIFY EITHER BECAUSE OF INSUFFICIENTLY SILENCING ACTIVATED BUILDING CYCLES, OR BY ACQUIRING EPIGENETIC DEVIATIONS. 2013 5 5428 24 REGULATION OF STRESS-INDUCED HEMATOPOIESIS. PURPOSE OF REVIEW: THE HEMATOPOIETIC COMPARTMENT IS TASKED WITH THE ESTABLISHMENT AND MAINTENANCE OF THE ENTIRE BLOOD PROGRAM IN STEADY-STATE AND IN RESPONSE TO STRESS. KEY TO THIS PROCESS ARE HEMATOPOIETIC STEM CELLS (HSCS), WHICH POSSESS THE UNIQUE ABILITY TO SELF-RENEW AND DIFFERENTIATE TO REPLENISH BLOOD CELLS THROUGHOUT AN ORGANISM'S LIFETIME. THOUGH TIGHTLY REGULATED, THE HEMATOPOIETIC SYSTEM IS VULNERABLE TO BOTH INTRINSIC AND EXTRINSIC FACTORS THAT INFLUENCE HEMATOPOIETIC STEM AND PROGENITOR CELL (HSPC) FATE. HERE, WE REVIEW RECENT ADVANCES IN OUR UNDERSTANDING OF HEMATOPOIETIC REGULATION UNDER STRESS CONDITIONS SUCH AS INFLAMMATION, AGING, MITOCHONDRIAL DEFECTS, AND DAMAGE TO DNA OR ENDOPLASMIC RETICULUM. RECENT FINDINGS: RECENT STUDIES HAVE ILLUSTRATED THE VAST MECHANISMS INVOLVED IN REGULATING STRESS-INDUCED HEMATOPOIESIS, INCLUDING CYTOKINE-MEDIATED LINEAGE BIAS, GENE SIGNATURE CHANGES IN AGED HSCS ASSOCIATED WITH CHRONIC INFLAMMATION, THE IMPACT OF CLONAL HEMATOPOIESIS AND STRESS TOLERANCE, CHARACTERIZATION OF THE HSPC RESPONSE TO ENDOPLASMIC RETICULUM STRESS AND OF SEVERAL EPIGENETIC REGULATORS THAT INFLUENCE HSPC RESPONSE TO CELL CYCLE STRESS. SUMMARY: SEVERAL KEY RECENT FINDINGS HAVE DEEPENED OUR UNDERSTANDING OF STRESS HEMATOPOIESIS. THESE STUDIES WILL ADVANCE OUR ABILITIES TO REDUCE THE IMPACT OF STRESS IN DISEASE AND AGING THROUGH CLINICAL INTERVENTIONS TO TREAT STRESS-RELATED OUTCOMES. 2020 6 5816 26 STRESS AND STEM CELLS. THE UNIQUE PROPERTIES AND FUNCTIONS OF STEM CELLS MAKE THEM PARTICULARLY SUSCEPTIBLE TO STRESSES AND ALSO LEAD TO THEIR REGULATION BY STRESS. STEM CELL DIVISION MUST RESPOND TO THE DEMAND TO REPLENISH CELLS DURING NORMAL TISSUE TURNOVER AS WELL AS IN RESPONSE TO DAMAGE. OXIDATIVE STRESS, MECHANICAL STRESS, GROWTH FACTORS, AND CYTOKINES SIGNAL STEM CELL DIVISION AND DIFFERENTIATION. MANY OF THE CONSERVED PATHWAYS REGULATING STEM CELL SELF-RENEWAL AND DIFFERENTIATION ARE ALSO STRESS-RESPONSE PATHWAYS. THE LONG LIFE SPAN AND DIVISION POTENTIAL OF STEM CELLS CREATE A PROPENSITY FOR TRANSFORMATION (CANCER) AND SPECIFIC STRESS RESPONSES SUCH AS APOPTOSIS AND SENESCENCE ACT AS ANTITUMOR MECHANISMS. QUIESCENCE REGULATED BY CDK INHIBITORS AND A HYPOXIC NICHE REGULATED BY FOXO TRANSCRIPTION FACTOR FUNCTION TO REDUCE STRESS FOR SEVERAL TYPES OF STEM CELLS TO FACILITATE LONG-TERM MAINTENANCE. AGING IS A PARTICULARLY RELEVANT STRESS FOR STEM CELLS, BECAUSE REPEATED DEMANDS ON STEM CELL FUNCTION OVER THE LIFE SPAN CAN HAVE CUMULATIVE CELL-AUTONOMOUS EFFECTS INCLUDING EPIGENETIC DYSREGULATION, MUTATIONS, AND TELOMERE EROSION. IN ADDITION, AGING OF THE ORGANISM IMPAIRS FUNCTION OF THE STEM CELL NICHE AND SYSTEMIC SIGNALS, INCLUDING CHRONIC INFLAMMATION AND OXIDATIVE STRESS. 2012 7 4037 19 MACROPHAGE IMMUNOMETABOLISM AND INFLAMMAGING: ROLES OF MITOCHONDRIAL DYSFUNCTION, CELLULAR SENESCENCE, CD38, AND NAD. AGING IS A COMPLEX PROCESS THAT INVOLVES DYSFUNCTION ON MULTIPLE LEVELS, ALL OF WHICH SEEM TO CONVERGE ON INFLAMMATION. MACROPHAGES ARE INTIMATELY INVOLVED IN INITIATING AND RESOLVING INFLAMMATION, AND THEIR DYSREGULATION WITH AGE IS A PRIMARY CONTRIBUTOR TO INFLAMMAGING-A STATE OF CHRONIC, LOW-GRADE INFLAMMATION THAT DEVELOPS DURING AGING. AMONG THE AGE-RELATED CHANGES THAT OCCUR TO MACROPHAGES ARE A HEIGHTENED STATE OF BASAL INFLAMMATION AND DIMINISHED OR HYPERACTIVE INFLAMMATORY RESPONSES, WHICH SEEM TO BE DRIVEN BY METABOLIC-DEPENDENT EPIGENETIC CHANGES. IN THIS REVIEW ARTICLE WE PROVIDE A BRIEF OVERVIEW OF MITOCHONDRIAL FUNCTIONS AND AGE-RELATED CHANGES THAT OCCUR TO MACROPHAGES, WITH AN EMPHASIS ON HOW THE INFLAMMAGING ENVIRONMENT, SENESCENCE, AND NAD DECLINE CAN AFFECT THEIR METABOLISM, PROMOTE DYSREGULATION, AND CONTRIBUTE TO INFLAMMAGING AND AGE-RELATED PATHOLOGIES. 2020 8 6532 17 TRANSCRIPTIONAL REGULATION OF INFLAMMASOMES. INFLAMMASOMES ARE MULTIMOLECULAR COMPLEXES WITH POTENT INFLAMMATORY ACTIVITY. AS SUCH, THEIR ACTIVITY IS TIGHTLY REGULATED AT THE TRANSCRIPTIONAL AND POST-TRANSCRIPTIONAL LEVELS. IN THIS REVIEW, WE PRESENT THE TRANSCRIPTIONAL REGULATION OF INFLAMMASOME GENES FROM SENSORS (E.G., NLRP3) TO SUBSTRATES (E.G., IL-1BETA). LINEAGE-DETERMINING TRANSCRIPTION FACTORS SHAPE INFLAMMASOME RESPONSES IN DIFFERENT CELL TYPES WITH PROFOUND CONSEQUENCES ON THE RESPONSIVENESS TO INFLAMMASOME-ACTIVATING STIMULI. PRO-INFLAMMATORY SIGNALS (STERILE OR MICROBIAL) HAVE A KEY TRANSCRIPTIONAL IMPACT ON INFLAMMASOME GENES, WHICH IS LARGELY MEDIATED BY NF-KAPPAB AND THAT TRANSLATES INTO HIGHER ANTIMICROBIAL IMMUNE RESPONSES. FURTHERMORE, DIVERSE INTRINSIC (E.G., CIRCADIAN CLOCK, METABOLITES) OR EXTRINSIC (E.G., XENOBIOTICS) SIGNALS ARE INTEGRATED BY SIGNAL-DEPENDENT TRANSCRIPTION FACTORS AND CHROMATIN STRUCTURE CHANGES TO MODULATE TRANSCRIPTIONALLY INFLAMMASOME RESPONSES. FINALLY, ANTI-INFLAMMATORY SIGNALS (E.G., IL-10) COUNTERBALANCE INFLAMMASOME GENES INDUCTION TO LIMIT DELETERIOUS INFLAMMATION. TRANSCRIPTIONAL REGULATIONS THUS APPEAR AS THE FIRST LINE OF INFLAMMASOME REGULATION TO RAISE THE DEFENSE LEVEL IN FRONT OF STRESS AND INFECTIONS BUT ALSO TO LIMIT EXCESSIVE OR CHRONIC INFLAMMATION. 2020 9 5258 25 PROGRESSION OF TUBULOINTERSTITIAL FIBROSIS AND THE CHRONIC KIDNEY DISEASE PHENOTYPE - ROLE OF RISK FACTORS AND EPIGENETICS. ALTHOUGH THE KIDNEY HAS CAPACITY TO REPAIR AFTER MILD INJURY, ONGOING OR SEVERE DAMAGE RESULTS IN SCARRING (FIBROSIS) AND AN ASSOCIATED PROGRESSIVE LOSS OF KIDNEY FUNCTION. HOWEVER, DESPITE ITS UNIVERSAL SIGNIFICANCE, EVIDENCE HIGHLIGHTS A POPULATION BASED HETEROGENEITY IN THE TRAJECTORY OF CHRONIC KIDNEY DISEASE (CKD) IN THESE PATIENTS. TO EXPLAIN THE HETEROGENEITY OF THE CKD PHENOTYPE REQUIRES AN UNDERSTANDING OF THE RELEVANT RISK FACTORS FOR FIBROSIS. THESE FACTORS INCLUDE BOTH THE EXTRINSIC NATURE OF INJURY, AND INTRINSIC FACTORS SUCH AS AGE, GENDER, GENETICS, AND PERPETUAL ACTIVATION OF FIBROBLASTS THROUGH PRIMING. IN MANY CASES AN ADDITIONAL LEVEL OF REGULATION IS PROVIDED BY EPIGENETIC MECHANISMS WHICH INTEGRATE THE VARIOUS PRO-FIBROTIC AND ANTI-FIBROTIC TRIGGERS IN FIBROGENESIS. IN THIS REVIEW WE THEREFORE EXAMINE THE VARIOUS MOLECULAR AND STRUCTURAL CHANGES OF FIBROSIS, AND HOW THEY ARE INFLUENCED BY EXTRINSIC AND INTRINSIC FACTORS. OUR AIM IS TO PROVIDE A UNIFYING HYPOTHESIS TO HELP EXPLAIN THE TRANSITION FROM ACUTE TO CKD. 2017 10 5632 29 SENESCENT CELLS: SASPECTED DRIVERS OF AGE-RELATED PATHOLOGIES. THE PROGRESSION OF PHYSIOLOGICAL AGEING IS DRIVEN BY INTRACELLULAR ABERRATIONS INCLUDING TELOMERE ATTRITION, GENOMIC INSTABILITY, EPIGENETIC ALTERATIONS AND LOSS OF PROTEOSTASIS. THESE IN TURN DAMAGE CELLS AND COMPROMISE THEIR FUNCTIONALITY. CELLULAR SENESCENCE, A STABLE IRREVERSIBLE CELL-CYCLE ARREST, IS ELICITED IN DAMAGED CELLS AND PREVENTS THEIR PROPAGATION IN THE ORGANISM. UNDER NORMAL CONDITIONS, SENESCENT CELLS RECRUIT THE IMMUNE SYSTEM WHICH FACILITATES THEIR REMOVAL FROM TISSUES. NEVERTHELESS, DURING AGEING, TISSUE-RESIDING SENESCENT CELLS TEND TO ACCUMULATE, AND MIGHT NEGATIVELY IMPACT THEIR MICROENVIRONMENT VIA PROFOUND SECRETORY PHENOTYPE WITH PRO-INFLAMMATORY CHARACTERISTICS, TERMED SENESCENCE-ASSOCIATED SECRETORY PHENOTYPE (SASP). INDEED, SENESCENT CELLS ARE MOSTLY ABUNDANT AT SITES OF AGE-RELATED PATHOLOGIES, INCLUDING DEGENERATIVE DISORDERS AND MALIGNANCIES. INTERESTINGLY, STUDIES ON PROGEROID MICE INDICATE THAT SELECTIVE ELIMINATION OF SENESCENT CELLS CAN DELAY AGE-RELATED DETERIORATION. THIS SUGGESTS THAT CHRONIC INFLAMMATION INDUCED BY SENESCENT CELLS MIGHT BE A MAIN DRIVER OF THESE PATHOLOGIES. IMPORTANTLY, SENESCENT CELLS ACCUMULATE AS A RESULT OF DEFICIENT IMMUNE SURVEILLANCE, AND THEIR REMOVAL IS INCREASED UPON THE USE OF IMMUNE STIMULATORY AGENTS. INSIGHTS INTO MECHANISMS OF SENESCENCE SURVEILLANCE COULD BE COMBINED WITH CURRENT APPROACHES FOR CANCER IMMUNOTHERAPY TO PROPOSE NEW PREVENTIVE AND THERAPEUTIC STRATEGIES FOR AGE-RELATED DISEASES. 2014 11 115 24 A STEM CELL AGING FRAMEWORK, FROM MECHANISMS TO INTERVENTIONS. STEM CELLS PLAY CENTRAL ROLES IN TISSUE DEVELOPMENT, HOMEOSTASIS, AND REGENERATION. DECADES OF SCIENTIFIC RESEARCH HAVE UNCOVERED PROCESSES OF STEM CELL DECLINE IN TISSUE AND ORGANISMAL AGING, AND MORE RECENTLY, PIONEERING TECHNOLOGIES PERMIT THE DISSECTION OF ITS UNDERLYING MECHANISMS AND INFORM THERAPEUTIC DEVELOPMENT FOR AGING AND AGING-ASSOCIATED DISORDERS. IN THIS REVIEW, WE ELUCIDATE AGING-RELATED FEATURES ACROSS DIFFERENT SOMATIC STEM CELL TYPES, WITH A SPECIFIC FOCUS ON EPIGENETIC CHANGES, LOSS OF PROTEIN HOMEOSTASIS, AND SYSTEMIC INFLUENCING FACTORS, INCLUDING CHRONIC INFLAMMATION, CIRCADIAN RHYTHM DYSREGULATION, AND METABOLIC DISORDER. OUR SURVEY OF ORGANISMAL STEM CELL AGING SUMMARIZES ITS UNDERLYING BIOLOGICAL IMPLICATIONS, POINTS TO POTENTIAL BIOMARKERS OF STEM CELL AGING, AND DISCUSSES STEM CELL-BASED THERAPEUTIC STRATEGIES WITH THE POTENTIAL FOR PROMOTING HEALTHY AGING AND COMBATING AGING AND AGE-RELATED DISEASES. 2022 12 5631 22 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 4 26 "MIX OF MICS"- PHENOTYPIC AND BIOLOGICAL HETEROGENEITY OF "MULTIPOTENT" MUSCLE INTERSTITIAL CELLS (MICS). THE CAPACITY OF ADULT SKELETAL MUSCLE FOR REGENERATION APPEARS TO BE LIMITED, WITH PROGRESSIVE IMPAIRMENT IN REPAIR EFFICIENCY OF INJURED MUSCLES OBSERVED IN CHRONIC MUSCULAR DISORDERS AND DURING AGING. WHILE SATELLITE CELLS, THE COMMITTED ADULT MUSCLE STEM CELLS, ARE THE MAIN DIRECT CELL SOURCE SUPPORTING THE REGENERATIVE POTENTIAL OF ADULT SKELETAL MUSCLES, THE CHARACTERIZATION OF THE CELL TYPES AND SIGNALS THAT CONSTITUTE THE FUNCTIONAL "NICHE" OF SATELLITE CELLS IS CURRENTLY THE OBJECT OF INTENSE INVESTIGATION. RECENT STUDIES HAVE IDENTIFIED A FUNCTIONAL RELATIONSHIP BETWEEN SATELLITE CELLS AND VARIOUS CELL TYPES LOCATED IN KEY ANATOMICAL POSITION, SUCH AS THE INTERSTITIUM OF SKELETAL MUSCLES. THIS HETEROGENEOUS POPULATION OF MUSCLE INTERSTITIAL CELLS (MICS) APPEARS TO RETAIN AN INTRINSIC MULTIPOTENCY WITHIN THE MESODERMAL LINEAGE, AND THEIR DIRECT OR INDIRECT CONTRIBUTION TO MYOFIBER TURNOVER, REPAIR AND DEGENERATION HAS BEEN SUGGESTED BY MANY STUDIES THAT WILL BE REVIEWED HERE. GIVEN THE EXISTING GAP OF KNOWLEDGE ON LINEAGE IDENTITY AND FUNCTIONAL PROPERTIES OF MICS, THEIR DETAILED CHARACTERIZATION AT THE SINGLE CELL LEVEL HOLDS THE PROMISE TO PROVIDE KEY INSIGHT INTO THE COMPOSITION OF THIS HETEROGENEOUS POPULATION AND THE DYNAMIC TRANSITION THROUGH DISTINCT SUB-POPULATIONS IN HEALTHY, DISEASED AND AGING MUSCLES. THIS REVIEW PROVIDES AN OVERVIEW OF THE RESULTS OF VARIOUS STUDIES DESCRIBING THE PHENOTYPE AND THE FUNCTION OF CELLS ISOLATED FROM SKELETAL MUSCLE INTERSTITIUM, AND DISCUSSES THE IMPORTANCE OF SINGLE CELL TRANSCRIPTION PROFILING IN ORDER TO DECIPHER THE FUNCTIONAL AND PHENOTYPICAL HETEROGENEITY OF MUSCLE INTERSTITIAL CELLS (MICS). 2012 14 3183 23 HALLMARKS OF T CELL AGING. THE AGED ADAPTIVE IMMUNE SYSTEM IS CHARACTERIZED BY PROGRESSIVE DYSFUNCTION AS WELL AS INCREASED AUTOIMMUNITY. THIS DECLINE IS RESPONSIBLE FOR ELEVATED SUSCEPTIBILITY TO INFECTION AND CANCER, AS WELL AS DECREASED VACCINATION EFFICACY. RECENT EVIDENCE INDICATES THAT CD4(+) T CELL-INTRINSIC ALTERATINS CONTRIBUTE TO CHRONIC INFLAMMATION AND ARE SUFFICIENT TO ACCELERATE AN ORGANISM-WIDE AGING PHENOTYPE, SUPPORTING THE IDEA THAT T CELL AGING PLAYS A MAJOR ROLE IN BODY-WIDE DETERIORATION. IN THIS REVIEW, WE PROPOSE TEN MOLECULAR HALLMARKS TO REPRESENT COMMON DENOMINATORS OF T CELL AGING. THESE HALLMARKS ARE GROUPED INTO FOUR PRIMARY HALLMARKS (THYMIC INVOLUTION, MITOCHONDRIAL DYSFUNCTION, GENETIC AND EPIGENETIC ALTERATIONS, AND LOSS OF PROTEOSTASIS) AND FOUR SECONDARY HALLMARKS (REDUCTION OF THE TCR REPERTOIRE, NAIVE-MEMORY IMBALANCE, T CELL SENESCENCE, AND LACK OF EFFECTOR PLASTICITY), AND TOGETHER THEY EXPLAIN THE MANIFESTATION OF THE TWO INTEGRATIVE HALLMARKS (IMMUNODEFICIENCY AND INFLAMMAGING). A MAJOR CHALLENGE NOW IS WEIGHING THE RELATIVE IMPACT OF THESE HALLMARKS ON T CELL AGING AND UNDERSTANDING THEIR INTERCONNECTIONS, WITH THE FINAL GOAL OF DEFINING MOLECULAR TARGETS FOR INTERVENTIONS IN THE AGING PROCESS. 2021 15 4386 15 MITOCHONDRIAL STRESS INDUCED BY CONTINUOUS STIMULATION UNDER HYPOXIA RAPIDLY DRIVES T CELL EXHAUSTION. CANCER AND CHRONIC INFECTIONS INDUCE T CELL EXHAUSTION, A HYPOFUNCTIONAL FATE CARRYING DISTINCT EPIGENETIC, TRANSCRIPTOMIC AND METABOLIC CHARACTERISTICS. HOWEVER, DRIVERS OF EXHAUSTION REMAIN POORLY UNDERSTOOD. AS INTRATUMORAL EXHAUSTED T CELLS EXPERIENCE SEVERE HYPOXIA, WE HYPOTHESIZED THAT METABOLIC STRESS ALTERS THEIR RESPONSES TO OTHER SIGNALS, SPECIFICALLY, PERSISTENT ANTIGENIC STIMULATION. IN VITRO, ALTHOUGH CD8(+) T CELLS EXPERIENCING CONTINUOUS STIMULATION OR HYPOXIA ALONE DIFFERENTIATED INTO FUNCTIONAL EFFECTORS, THE COMBINATION RAPIDLY DROVE T CELL DYSFUNCTION CONSISTENT WITH EXHAUSTION. CONTINUOUS STIMULATION PROMOTED BLIMP-1-MEDIATED REPRESSION OF PGC-1ALPHA-DEPENDENT MITOCHONDRIAL REPROGRAMMING, RENDERING CELLS POORLY RESPONSIVE TO HYPOXIA. LOSS OF MITOCHONDRIAL FUNCTION GENERATED INTOLERABLE LEVELS OF REACTIVE OXYGEN SPECIES (ROS), SUFFICIENT TO PROMOTE EXHAUSTED-LIKE STATES, IN PART THROUGH PHOSPHATASE INHIBITION AND THE CONSEQUENT ACTIVITY OF NUCLEAR FACTOR OF ACTIVATED T CELLS. REDUCING T CELL-INTRINSIC ROS AND LOWERING TUMOR HYPOXIA LIMITED T CELL EXHAUSTION, SYNERGIZING WITH IMMUNOTHERAPY. THUS, IMMUNOLOGIC AND METABOLIC SIGNALING ARE INTRINSICALLY LINKED: THROUGH MITIGATION OF METABOLIC STRESS, T CELL DIFFERENTIATION CAN BE ALTERED TO PROMOTE MORE FUNCTIONAL CELLULAR FATES. 2021 16 4178 14 MEMORY T-CELL HETEROGENEITY AND TERMINOLOGY. IMMUNOLOGICAL MEMORY AND EXHAUSTION ARE FUNDAMENTAL FEATURES OF ADAPTIVE IMMUNITY. RECENT ADVANCES REVEAL INCREASING HETEROGENEITY AND DIVERSITY AMONG CD8 T-CELL SUBSETS, RESULTING IN NEW SUBSETS TO ANNOTATE AND UNDERSTAND. HERE, WE REVIEW OUR CURRENT KNOWLEDGE OF DIFFERENTIATION AND MAINTENANCE OF MEMORY AND EXHAUSTED CD8 T CELLS, INCLUDING PHENOTYPIC CLASSIFICATION, DEVELOPMENTAL PATHS, TRANSCRIPTIONAL AND EPIGENETIC FEATURES, AND CELL INTRINSIC AND EXTRINSIC FACTORS. ADDITIONALLY, WE USE THIS OUTLINE TO DISCUSS THE NOMENCLATURE OF EFFECTOR, MEMORY, AND EXHAUSTED CD8 T CELLS. FINALLY, WE DISCUSS HOW NEW FINDINGS ABOUT THESE CELL TYPES MAY IMPACT THE THERAPEUTIC EFFICACY AND DEVELOPMENT OF IMMUNOTHERAPIES TARGETING EFFECTOR, MEMORY, AND/OR EXHAUSTED CD8 T CELLS IN CHRONIC INFECTIONS AND CANCER. 2021 17 6154 33 THE GENE EXPRESSION PROGRAM OF PROSTATE FIBROBLAST SENESCENCE MODULATES NEOPLASTIC EPITHELIAL CELL PROLIFERATION THROUGH PARACRINE MECHANISMS. THE GREATEST RISK FACTOR FOR DEVELOPING CARCINOMA OF THE PROSTATE IS ADVANCED AGE. POTENTIAL MOLECULAR AND PHYSIOLOGIC CONTRIBUTORS TO THE FREQUENCY OF CANCER OCCURRENCE IN OLDER INDIVIDUALS INCLUDE THE ACCUMULATION OF SOMATIC MUTATIONS THROUGH DEFECTS IN GENOME MAINTENANCE, EPIGENETIC GENE SILENCING, OXIDATIVE STRESS, LOSS OF IMMUNE SURVEILLANCE, TELOMERE DYSFUNCTION, CHRONIC INFLAMMATION, AND ALTERATIONS IN TISSUE MICROENVIRONMENT. IN THIS CONTEXT, THE PROCESS OF PROSTATE CARCINOGENESIS CAN BE INFLUENCED THROUGH INTERACTIONS BETWEEN INTRINSIC CELLULAR ALTERATIONS AND THE EXTRINSIC MICROENVIRONMENT AND MACROENVIRONMENT, BOTH OF WHICH CHANGE SUBSTANTIALLY AS A CONSEQUENCE OF AGING. IN THIS STUDY, WE SOUGHT TO CHARACTERIZE THE MOLECULAR ALTERATIONS THAT OCCUR DURING THE PROCESS OF PROSTATE FIBROBLAST SENESCENCE TO IDENTIFY FACTORS IN THE AGED TISSUE MICROENVIRONMENT CAPABLE OF PROMOTING THE PROLIFERATION AND POTENTIALLY THE NEOPLASTIC PROGRESSION OF PROSTATE EPITHELIUM. WE EVALUATED THREE MECHANISMS LEADING TO CELL SENESCENCE: OXIDATIVE STRESS, DNA DAMAGE, AND REPLICATIVE EXHAUSTION. WE IDENTIFIED A CONSISTENT PROGRAM OF GENE EXPRESSION THAT INCLUDES A SUBSET OF PARACRINE FACTORS CAPABLE OF INFLUENCING ADJACENT PROSTATE EPITHELIAL GROWTH. BOTH DIRECT COCULTURE AND CONDITIONED MEDIUM FROM SENESCENT PROSTATE FIBROBLASTS STIMULATED EPITHELIAL CELL PROLIFERATION, 3-FOLD AND 2-FOLD, RESPECTIVELY. THE PARACRINE-ACTING PROTEINS FIBROBLAST GROWTH FACTOR 7, HEPATOCYTE GROWTH FACTOR, AND AMPHIREGULIN (AREG) WERE ELEVATED IN THE EXTRACELLULAR ENVIRONMENT OF SENESCENT PROSTATE FIBROBLASTS. EXOGENOUS AREG ALONE STIMULATED PROSTATE EPITHELIAL CELL GROWTH, AND NEUTRALIZING ANTIBODIES AND SMALL INTERFERING RNA TARGETING AREG ATTENUATED, BUT DID NOT COMPLETELY ABROGATE THE GROWTH-PROMOTING EFFECTS OF SENESCENT FIBROBLAST CONDITIONED MEDIUM. THESE RESULTS SUPPORT THE CONCEPT THAT AGING-RELATED CHANGES IN THE PROSTATE MICROENVIRONMENT MAY CONTRIBUTE TO THE PROGRESSION OF PROSTATE NEOPLASIA. 2006 18 3818 20 INTRINSIC AND ENVIRONMENTAL BASIS OF AGING: A NARRATIVE REVIEW. LONGEVITY HAS BEEN A TOPIC OF INTEREST SINCE THE BEGINNINGS OF HUMANITY, YET ITS AETIOLOGY AND PRECISE MECHANISMS REMAIN TO BE ELUCIDATED. AGING IS CURRENTLY VIEWED AS A PHYSIOLOGICAL PHENOMENON CHARACTERIZED BY THE GRADUAL DEGENERATION OF ORGANIC PHYSIOLOGY AND MORPHOLOGY DUE TO THE PASSAGE OF TIME WHERE BOTH EXTERNAL AND INTERNAL STIMULI INTERVENE. THE INFLUENCE OF INTRINSIC FACTORS, SUCH AS PROGRESSIVE TELOMERE SHORTENING, GENOME INSTABILITY DUE TO MUTATION BUILDUP, THE DIRECT OR INDIRECT ACTIONS OF AGE-RELATED GENES, AND MARKED CHANGES IN EPIGENETIC, METABOLIC, AND MITOCHONDRIAL PATTERNS CONSTITUTE A BIG PART OF ITS UNDERLYING ENDOGENOUS MECHANISMS. ON THE OTHER HAND, SEVERAL PSYCHOSOCIAL AND DEMOGRAPHIC FACTORS, SUCH AS DIET, PHYSICAL ACTIVITY, SMOKING, AND DRINKING HABITS, MAY HAVE AN EVEN MORE SIGNIFICANT IMPACT ON SHAPING THE AGING PROCESS. CONSEQUENTIALLY, IMPLEMENTING DIETARY AND EXERCISE PATTERNS HAS BEEN PROPOSED AS THE MOST VIABLE ALTERNATIVE STRATEGY FOR ATTENUATING THE MOST TYPICAL DEGENERATIVE AGING CHANGES, THUS INCREASING THE LIKELIHOOD OF PROLONGING LIFESPAN AND ACHIEVING SUCCESSFUL AGING. 2023 19 2069 22 EPIGENETIC CONTROL OF SKELETAL MUSCLE REGENERATION: INTEGRATING GENETIC DETERMINANTS AND ENVIRONMENTAL CHANGES. DURING EMBRYONIC DEVELOPMENT, PLURIPOTENT CELLS ARE GENETICALLY COMMITTED TO SPECIFIC LINEAGES BY THE EXPRESSION OF CELL-TYPE-SPECIFIC TRANSCRIPTIONAL ACTIVATORS THAT DIRECT THE FORMATION OF SPECIALIZED TISSUES AND ORGANS IN RESPONSE TO DEVELOPMENTAL CUES. CHROMATIN-MODIFYING PROTEINS ARE EMERGING AS ESSENTIAL COMPONENTS OF THE EPIGENETIC MACHINERY, WHICH ESTABLISHES THE NUCLEAR LANDSCAPE THAT ULTIMATELY DETERMINES THE FINAL IDENTITY AND FUNCTIONAL SPECIALIZATION OF ADULT CELLS. RECENT EVIDENCE HAS REVEALED THAT DISCRETE POPULATIONS OF ADULT CELLS CAN RETAIN THE ABILITY TO ADOPT ALTERNATIVE CELL FATES IN RESPONSE TO ENVIRONMENTAL CUES. THESE CELLS INCLUDE CONVENTIONAL ADULT STEM CELLS AND A STILL POORLY DEFINED COLLECTION OF CELL TYPES ENDOWED WITH FACULTATIVE PHENOTYPE AND FUNCTIONAL PLASTICITY. UNDER PHYSIOLOGICAL CONDITIONS OR ADAPTIVE STATES, THESE CELLS COOPERATE TO SUPPORT TISSUE AND ORGAN HOMEOSTASIS, AND TO PROMOTE GROWTH OR COMPENSATORY REGENERATION. HOWEVER, DURING CHRONIC DISEASES AND AGING THESE CELLS CAN ADOPT A PATHOLOGICAL PHENOTYPE AND MEDIATE MALADAPTIVE RESPONSES, SUCH AS THE FORMATION OF FIBROTIC SCARS AND FAT DEPOSITION THAT PROGRESSIVELY REPLACES STRUCTURAL AND FUNCTIONAL UNITS OF TISSUES AND ORGANS. THE MOLECULAR DETERMINANTS OF THESE PHENOTYPIC TRANSITIONS ARE ONLY EMERGING FROM RECENT STUDIES THAT REVEAL HOW DYNAMIC CHROMATIN STATES CAN GENERATE FLEXIBLE EPIGENETIC LANDSCAPES, WHICH CONFER ON CELLS THE ABILITY TO RETAIN PARTIAL PLURIPOTENCY AND ADAPT TO ENVIRONMENTAL CHANGES. THIS REVIEW SUMMARIZES OUR CURRENT KNOWLEDGE ON THE ROLE OF THE EPIGENETIC MACHINERY AS A 'FILTER' BETWEEN GENETIC COMMITMENT AND ENVIRONMENTAL SIGNALS IN CELL TYPES THAT CAN ALTERNATIVELY PROMOTE SKELETAL MUSCLE REGENERATION OR FIBRO-ADIPOGENIC DEGENERATION. 2013 20 4503 22 MOSAIC AGING. ALTHOUGH ALL MULTICELLULAR ORGANISMS UNDERGO STRUCTURAL AND FUNCTIONAL DETERIORATION WITH AGE, SENESCENCE IS NOT A UNIFORM PROCESS. RATHER, EACH ORGANISM EXPERIENCES A CONSTELLATION OF CHANGES THAT REFLECT THE HETEROGENEOUS EFFECTS OF AGE ON MOLECULES, CELLS, ORGANS AND SYSTEMS, AN IDIOSYNCRATIC PATTERN THAT WE REFER TO AS MOSAIC AGING. VARYING GENETIC, EPIGENETIC AND ENVIRONMENTAL FACTORS (LOCAL AND EXTRINSIC) CONTRIBUTE TO THE AGING PHENOTYPE IN A GIVEN INDIVIDUAL, AND THESE AGENTS INFLUENCE THE TYPE AND RATE OF FUNCTIONAL DECLINE, AS WELL AS THE LIKELIHOOD OF DEVELOPING AGE-ASSOCIATED AFFLICTIONS SUCH AS CARDIOVASCULAR DISEASE, ARTHRITIS, CANCER, AND NEURODEGENERATIVE DISORDERS. IDENTIFYING KEY FACTORS THAT DRIVE AGING, CLARIFYING THEIR ACTIVITIES IN DIFFERENT SYSTEMS, AND IN PARTICULAR UNDERSTANDING HOW THEY INTERACT WILL ENHANCE OUR COMPREHENSION OF THE AGING PROCESS, AND COULD YIELD INSIGHTS INTO THE PERMISSIVE ROLE THAT SENESCENCE PLAYS IN THE EMERGENCE OF ACUTE AND CHRONIC DISEASES OF THE ELDERLY. 2010