Addiction is a chronically relapsing neuropsychiatric disease that occurs in some, but not all, individuals who use substances of abuse. Relatively little is known about the mechanisms which contribute to individual differences in susceptibility to addiction. Neural gene expression regulation underlies the pathogenesis of addiction, which is mediated by epigenetic mechanisms, such as DNA modifications. A growing body of work has demonstrated distinct DNA epigenetic signatures in brain reward regions that may be associated with addiction susceptibility. Furthermore, factors that influence addiction susceptibility are also known to have a DNA epigenetic basis. In the present review, we discuss the notion that addiction susceptibility has an underlying DNA epigenetic basis. We focus on major phenotypes of addiction susceptibility and review evidence of cell type-specific, time dependent, and sex biased effects of drug use. We highlight the role of DNA epigenetics in these diverse processes and propose its contribution to addiction susceptibility differences. Given the prevalence and lack of effective treatments for addiction, elucidating the DNA epigenetic mechanism of addiction vulnerability may represent an expeditious approach to relieving the addiction disease burden. DNA cytosine methylation (mC) is a major epigenetic modification in which methyl groups are covalently bound to the 5-carbon position of cytosine bases by DNA methyltransferases  . CytosinAs potent forms of environmental stimuli, drugs of abuse affect the expression and activity of DNA epigenetic machinery ; Table 1While addiction is a chronically relapsing neuropsychiatric disease , it only. The opportunity to explore and engage with novel environmental conditions leads to inter-individual differences, such as in patterns of exploratory behavior, social behaviors, and cognitive traits. Underlying these behavioral changes are morphological, physiological, and molecular adaptations throughout the brain. Over time, differences in experience can thus drive the development of distinct behavioral phenotypes within members of the same population  displayed differences in drug taking after drug infusions were subsequently paired with electric shocks. The electric shocks were introduced after 20 days of shock-free METH self-administration to model the negative effects of chronic METH use in humans. Though all rats readily self-administered METH during the shock-free period, only some of them maintained drug seeking in the presence of electric shocks. Using hydroxymethylated DNA immunoprecipitation followed by sequencing (hMeDIP-seq), between-group differences in hmC were revealed in the NAc of these shock-resistant (more addicted) rats compared to rats that stopped taking drug after electric shock exposure. Specifically, differential hmC occurred in gene bodies of eight potassium channel genes of the shock-susceptible rats, whereas shock-resistant rats were similar to controls . Since aIn non-human primates, DNA methylation is also associated with individual differences in alcohol use disorder (AUD) susceptibility. Over the course of 1 year of daily access to alcohol, divergent patterns of drinking behaviors emerged. Based on patterns of daily alcohol intake and blood alcohol levels, male rhesus macaques were classified into low/binge drinkers and high/very high drinkers. Whole-genome bisulfite sequencing was then applied to assess DNA methylation in the NAc. A discrete set of differentially-methylated regions (DMRs) were identified between low/binge drinkers and high/very high drinkers and correlated with average daily alcohol intake . A majorTet1 and Dnmt1 was detected in the amygdala of alcohol-preferring rats, which implies downstream phenotype-specific differences in DNA modifications. However, a caveat to this interpretation and other studies mentioned here is that subjects classified as susceptible to addiction also consistently consume more drug over time than their less-susceptible counterparts. As drug exposure itself has been known to induce time-dependent DNA epigenetic changes in brain reward regions, the drug intake differences over time may therefore have contributed to differential methylation in the susceptible animals , about 15% of rats will select alcohol over sucrose. These alcohol-preferring rats also display features of human alcoholics, including increased motivation to work for alcohol and compulsive alcohol seeking in the presence of aversive stimuli . By usin animals . However animals  provided animals ]; a beha animals . Cocaineddiction . FurtherTaken together, among the growing number of studies on DNA epigenetics in drug action, a few have assessed its role in addiction susceptibility differences. Though it remains to be determined how much susceptibility variation may be attributed to DNA methylation changes, the evidence is beginning to establish that addiction susceptibility differences are associated with discrete DNA methylation events in brain reward regions. This was also supported by the finding that the strength of memory for natural rewards is regulated by DNA methylation in VTA dopamine neurons . The stuNumerous brain regions are involved in addiction, including cortical , prefrontal cortex (PFC), and cingulate cortex), striatal , and other basal ganglia  structures within the mesolimbic system  . Many ofin vivo is the heterogeneous cell populations in the brain, with each cell type presumably carrying out distinct functions in addiction. To exemplify this concept, we will take medium spiny neurons (MSNs) in NAc to demonstrate how two morphologically indistinguishable neuron subtypes that are intermingled together play contrasting roles in addiction. Centrally located in the brain reward circuitry and highly implicated in motivated behavior and addiction, the NAc receives inputs from both dopaminergic neurons of the VTA and glutamatergic neurons of the hippocampus, amygdala, and PFC. Approximately 95% of NAc neurons are MSNs, which can be classified into dopamine D1 receptor-expressing and dopamine D2 receptor-expressing MSNs . The remaining neuron types, such as cholinergic and GABAergic interneurons, comprise 1-2% of NAc neuronal cell types , in D2-MSNs suppresses cocaine reward, while the same manipulation in D1-MSNs generates the opposite behavioral consequence (egr3) molecule, which binds to the promotor area of several cocaine-regulated genes, was found to execute opposite roles in NAc D1-and D2-MSNs during cocaine-induced behavioral responding   . The N-mctivity) . Importae action , was dece action . While De action . ConsidePronounced brain cell type-specific differences in DNA modifications have been observed, which also appear to be brain region dependent . Recent Growing evidence also indicates a role for hmC in neuronal cell-specific functions. Neuronal hmC accumulates at gene bodies of actively-transcribed genes, poised and active enhancers, and exon/intron boundaries at both CG and CH contexts . PronounQK1 locus, which encodes an RNA binding protein involved in myelination, is hypermethylated in cortical neurons and hypomethylated in oligodendrocytes, the glial cell type that establishes myelin in the central nervous system. This pattern of differential methylation at the QK1 gene between neurons and oligodendrocytes was observed in both humans and non-human primates, suggesting that oligodendrocyte DNA methylation was conserved during evolution  and non-neuronal cells  suggested that cell type-specific CG-DMRs were localized to functional regions of the genome, while mCH, which is nearly depleted in non-neuronal cell types, was considered the primary neuron-specific DNA modification . Analysevolution . Likewisvolution , which fvolution .The recent advent of single cell methylation profiling has facilitated the recognition of brain cell types at an unprecedented level . In a piDnmt3a in mouse hippocampal ensembles enhanced the retrieval of memories in fear-conditioned mice. Moreover, its over-expression in recently-activated cultured hippocampal neurons induced hypermethylation at synaptic plasticity genes, suggesting that DNA methylation mediates the strength and stability of ensemble formation. The contribution of DNA methylation to neural plasticity in neuronal ensembles will likely give rise to broader patterns of neural and behavioral adaptations, such as those that characterize addiction. This may represent a functional connection between cell type-specific DNA modifications and addiction susceptibility.Though substantial progress has been made towards understanding the role of discrete brain cell types engaged in addiction, how these neural cells come to function differently among individuals and lead to variable responding to drugs of abuse remains largely unknown. Likewise, methodological advancements in single-cell DNA modification profiling have revealed the mosaicism of DNA epigenetic modifications in the brain, but how these differences give rise to broader patterns of brain activity and behavior remains elusive. Neuronal ensembles, or subgroups of cells which respond synchronously to sensory stimuli and cognitive states, may exemplify an intersection between cell-specific DNA methylation dynamics and addiction susceptibility. Exogenous influences, such as drugs of abuse, have been shown to promote the formation of neuronal ensembles in rodent brain , and their synchronous activation facilitates memory retrieval and stimuli-specific behavioral plasticity . A recenConsidering the dynamic developmental trajectory of the brain across ontogeny, disruption of one or more underlying developmental processes may predispose individuals to addiction susceptibility. In particular, maternal alcohol use during pregnancy can impart lasting changes in the brains of offspring and increase their propensity for addiction later in life . EpidemiWhereas prenatal development establishes global brain structure, postnatal brain development is associated with the refinement and maturation of neural circuitries, including increases in myelination, connectivity, and synaptic pruning. The maturation of the PFC and limbic brain structures is especially protracted and dynamically regulated by life experience. This allows the gradual acquisition of adult cognitive and emotional behaviors in accordance with an individual’s environmental needs . Drug exConsidered together, the dynamic course of brain development represents a protracted window of vulnerability to the deleterious effects of addictive drugs. Drug exposure in-utero and during early life can induce a lasting sensitivity to drug action that may confer increased vulnerability to addiction later in life. Therefore, a deeper understanding of the molecular consequences of drug exposure during brain development should aid in our interpretation of how prior drug experience impacts later-life vulnerability to addiction.DNA modifications play pivotal roles in mammalian development . In miceThe early postnatal period (immediately after birth) is characterized by a shift of brain methylome dynamics, with mCG and mCH levels accumulating in neurons and repressing the expression of genes involved in embryonic brain development . RegionaAgeing is characterized by a global decrease in DNA methylation in the brain. Age-related brain demethylation coincides with decreased synaptic density, particularly in cortex and hippocampus, which is thought to contribute to cognitive decline in older adults . Recent Taken together, DNA epigenetic dynamics mediate gene expression changes in pre- and post-natal brain development, with time-dependent changes in DNA modifications appearing to be integral to the development and continued functioning of neurons throughout the lifespan. Life experience may leave its imprint on the brain in the form of DNA modification signatures which denote the biological state of the brain. The temporal specificity of the DNA modification landscape may underscore the vulnerability of the brain to drugs of abuse during development and ageing.Ample evidence supports sex-specific differences in addiction-like behaviors . EpidemiIn addition to human studies, investigations of sex differences in addiction have been extensively executed in lab animals. The use of animal models, such as operant drug self-administration models in rodents, not only supports epidemiological findings of sex differences in drug use from humans, but also provides the advantage of parsing specific aspects of addiction, including sensitivity to drug reward, compulsive drug seeking, and relapse-like behaviors, among others . Using tThough still few in number, studies have illustrated sex-specific DNA epigenetic landscapes in the brain. Understanding such DNA modification variations should provide insights into the sexually-dimorphic addiction phenotypes.IGF2 and GR, in human fetal liver (BLCAP (bladder cancer-associated protein) gene was identified as the most significant target of alcohol-dependent DNA methylation changes in female lymphoblasts (Sex differences in DNA modifications are known to exist in peripheral tissues. In-utero exposure to cigarette chemicals was found to be associated with sex-dependent DNA methylation alterations at two imprinting genes, al liver . It was al liver . Differeal liver . Additiohoblasts . Notablyhoblasts .Remarkable sex differences in the fetal brain methylome have been reported, and many of these differentially-methylated loci persist in the adult cortex , implyinSex differences are not only detected in the methylome, but also observed in the expression of DNA modification enzymes in the brain, which may further contribute to sexually-dimorphic risk of addiction. For example, relative to males, female rats have significantly higher levels of DNMT3A in the amygdala in the first 2 weeks after birth, which indicates a time window when DNA methylation may have different impacts on the transcriptome between males and females . AdditioDnmt3a led to male sexual behaviors in female rats (In addition to sex-dependent DNA epigenetic differences, DNA methylation was shown to maintain sex differences in the brain. While the developing brain is destined for a female phenotype, it is masculinized by gonadal hormones during the perinatal critical period. It was found that gonadal hormones function through suppression of DNMT enzymes, which can release masculinizing genes from repression. Therefore, inhibition of DNMTs or conditional knockout of ale rats . A studyale rats .esr1 in mice results in altered behavioral responses to cocaine, including enhanced behavioral sensitization and an increased trend of cocaine seeking (esr1 gene promoter and activation of esr1 transcription, whereas intra-NAc infusions of an ESR1 agonist during forced cocaine withdrawal dramatically attenuated cocaine-seeking behavior in a reinstatement test. This suggests that the methylation status of esr1 plays a functional role during the incubation of cocaine craving after prolonged abstinence (esr1 expression levels between males and females were also found to be different during early development, which is associated with sex dependent DNA methylation at its promoter region (Gonadal steroid hormones function through their respective steroid receptors, where receptor activation translocates the ligand–receptor complex to the nucleus to mediate gene expression. Malfunctioning of this signaling pathway interrupts responding for drugs. For example, deletion of the estrogen receptor 1 gene  seeking . In addistinence . Furtherr region . TherefoIn sum, sex differences in DNA modifications exist not only in peripheral tissues, but also in the brain, and they appear to be established early in development and progress through the lifespan. DNA modifications maintain gonadal hormone signaling and some sex differences in the brain that may alter behavioral output. Considering the sex-dependent DNA methylome changes in response to drugs of abuse, DNA modifications are positioned as a molecular switch for sexual dimorphism in drug use behaviors and addiction susceptibility.In the present review, we explored the notion that DNA epigenetic dynamics in the brain mediate inter-individual difference in addiction susceptibility. Findings from humans and animals have established that drug use affects the expression and activity of DNA epigenetic machinery, particularly in brain regions comprising the reward circuitry. However, only some individuals who use drugs recreationally go on to develop the maladaptive behavioral plasticity indicative of addiction. Growing evidence suggests that the specific propensity for addiction may have a DNA epigenetic basis, because phenotypes of addiction susceptibility are associated with unique DNA epigenetic signatures in the brain. Moreover, factors known to influence addiction susceptibility, such as sex differences and life experience, also have a DNA epigenetic basis in the brain . Given t


Effectiveness of intensive care must be evaluated not only by short-term survival after a critical illness, but also by the recovery to an adequate quality of life. The increased evidence of long-term functional disabilities in intensive care survivors led to the definition of post-intensive care syndrome (PICS) . Early dThe improvement of mortality rates in the ICU has evidenced that survivors to a critical illness face a number of long-term severe complications and sequelae that can impair their quality of life . SeveralPICS covers several dimensions, including physical, cognitive and emotional aspects Fig. , for manSeveral ICU-related risk factors and short-term complications have been related to these long-term outcomes , Insulin-like growth factor (IGF-1), platelet derived growth factor (PDGF) or connective tissue growth factor (CTGF) among others –19. TGFβActivation of coagulation and fibrin deposition is another pathogenetic mechanism activated during acute lung injury that has been linked to long-term sequels. It has been shown that patients with lung interstitial diseases have an increased expression of procoagulant factors within the lung, including tissue factor or thrombin, or a decrease in protein C. Activation of proteinase-activated receptors (PARs) by the proteinases from the coagulation cascade  provides the mechanistic link between coagulation and fibrosis. Downstream signaling following PAR1 activation results in the expression of several profibrotic growth factors  and perpetuates the local release of proinflammatory cytokines and TGFβ .Wnt-dependent mechanism [Epithelial–Mesenchymal Transition (EMT) has also gained relevance in this scenario, where massive tissue remodeling takes place. EMT is a process in which a polarized epithelial cell acquires a mesenchymal phenotype, that includes synthesis of extracellular matrix components . During echanism , suggestechanism .Another common feature in these chronic conditions is epithelial barrier dysfunction, characterized by altered cell composition of the pseudostratified respiratory epithelium with basal and goblet cell hyperplasia and metaplasia , 28. In Finally, cell renewal is a key feature of chronic lung diseases. Excessive stem cell activation leads to accumulation of DNA damage and cell senescence . In patiThere are several mechanisms that may lead to brain injury in critically ill patients . The cenIl1b and Il6 in the brain stem [Il1b expression was abolished after vagotomy, suggesting the simultaneous activation of different mechanisms.Circulating molecules and cells may also reach the brain during critical illness. The systemic inflammatory response decreases blood–brain barrier permeability  and faciain stem . InteresThe link between these brain responses and functional outcomes has also been assessed. In a large animal model of prolonged protective mechanical ventilation, hippocampal damage was demonstrated . Acute lICUAW is a bilateral and symmetrical neuromuscular involvement, common in critically ill mechanically ventilated patients. Clinical studies in critical care settings involving electrophysiological tests and muscle histopathology suggest that both polyneuropathy and myopathy may coexist in ICU patients, being myopathy more frequently identified as the cause of weakness . CriticaMultiple molecular mechanisms, either independent or interacting, are involved in muscle wasting and evolve over time, from the onset of critical illness till the long-term recovery phase around 6 months after ICU discharge  Fig. 4)4). MusclInflammatory cytokines have been suggested to play a relevant role in the development of ICUAW. TNFα has been widely studied in this setting. In differentiated myotubes, TNFα stimulates catabolism by binding to TNF receptor subtype 1 and activating nuclear factor-kB. This transcriptional factor is essential for TNFα-induced reduction in muscle protein and loss of adult myosin heavy chain content , which iElevated levels of IL-1 are commonly found in critically ill patients’ serum and represent a potential stimulus for protein loss and muscle atrophy. The suggested underlying mechanisms are related to both protein synthesis and degradation , 70. IntHistologic and molecular analyses performed in skeletal muscle biopsies of critically ill patients suggest that recovery failure may be associated with satellite/progenitor cells loss and fibrosis , but it Similarly, the microvascular niche seems to be another partner of satellite cells. Christov et al. have suggested quiescent satellite cells to easily interplay with endothelial cells upon activation to set up coordinated angio-myogenesis in a functional manner . Indeed,Apart from inflammation and stem cell depletion, several other mechanisms may be involved in the development of persistent muscle weakness in survivors of critical illness. Distal axonal sensory-motor damage/dysfunction has also been described in ICUAW, being attributable to a reduced membrane excitability resulting from membrane depolarization and ion channel dysfunction , 86, togIn critically ill patients, the limited sample size of the muscle specimens precludes the identification of different mechanism-specific subphenotypes of muscle weakness, with different histopathological findings and driven by different mechanisms, though leading to the wide clinical spectrum of long-term functional disability. These different pathogenetic subphenotypes could explain the heterogeneous recovery observed among survivors of critical illness. For instance, the activated pathways could be promoting proliferation of satellite cells in some patients while related to fibrotic repair and satellite cell depletion in others. Understanding these mechanisms is crucial to identify therapeutic targets that, interfered at the beginning of the process, could modify the clinical course of ICUAW before the 6-month plateau has been achieved, either at the acute phase or during recovery.Long-term sequelae included in the PICS framework may be the consequence of organ-specific mechanisms, as described in the previous sections. However, the variety of symptoms included in PICS in response to common triggers  and the observed links and correlations amongst the different dimensions of the syndrome  raise thThe most characterized and studied mechanism in this setting is the inflammatory response. Inflammation is a physiological response necessary to fight against infections or injury and, therefore, restore homeostasis. During the acute phase of the inflammatory response, the presence of damage or pathogen-associated molecular patterns (DAMPs and PAMPs respectively) induces an initial systemic inflammatory response, mediated by the release of pro-inflammatory mediators, such as growth factors  and cytokines  as well as through mesenchymal or immune cells . This coDuring chronic inflammation, an unbalance between pro- and anti-inflammatory mediators makes homeostasis impossible to restore. The persistence of stimuli that modify the inflammatory response, either directly or indirectly, may perpetuate the release of inflammatory mediators not only to the lung but also to the systemic compartment, as the increased alveolo-capillary permeability facilitates their translocation. This persistent inflammation has been demonstrated in ARDS survivors even after clinical improvement or recover and related to worse physical recovery .Other potential mechanism which might be involved in PICS is related to the activation and spread of senescent responses. Cell senescence is defined as the cell cycle arrest in response to a stimulus, and a shift towards a specific phenotype characterized by the loss of several cell functions and the paracrine release of a variety of molecules (termed senescence-associated secretory phenotype—SASP), including proinflammatory mediators and senescence inductors (thus activating a positive feedback) . There aOf note, there is a positive feedback between inflammation and senescence. Inflammation causes activation of senescence through several mediators, such as IL-6. In turn, SASP includes the release of proinflammatory molecules, thus promoting a sustained response .A third mechanism potentially involved in the development of PICS is the so-called integrated stress response (ISR). ISR is a conserved cell response to different pathological conditions that results in a general decrease in protein synthesis and expression of a specific gene signature. Its activation is necessary to maintain cell homeostasis in the presence of different stress signals . This reISR plays an important role during acute lung injury or mechanical ventilation. Alveolar overdistension induced by mechanical ventilation results in PERK phosphorylation and subsequent phosphorylation of the factor elF2α. This alters epithelial permeability, induces proinflammatory cytokine release and cell death . ISR mayFinally, all these pathways converge in a reduced number of cell responses that mediate tissue dysfunction. The most studied response is apoptosis. There is substantial evidence showing disseminated apoptosis during the acute response to critical illness . This prBCL2 or tyrosine-kinases), may promote the selective death of these cells, facilitating a delayed repair [Activation of senescence, that render cells resistant to apoptosis , may be d repair . AlthougRather than a settled syndromic condition, PICS is an evolving concept that covers a large variety of symptoms and conditions experienced by ICU survivors. Clinical research in this topic may help to better identify, characterize and manage the long-term consequences of critical illness from the early onset of acute illnesses. The main components of PICS have been covered in the previous sections, but the systemic nature of acute severe diseases may cause other organ injuries.Critical illness may increase the risk of cardiovascular events after ICU and hospital discharge. Greater rates of atrial fibrillation, heart failure, and myocardial infarction have been described after sepsis . HoweverSimilarly, there is increasing evidence of long-term impaired kidney function after critical care, even in patients without acute renal failure . The devFinally, transgenerational effects of critical illness, requiring modification of the genome or epigenome of germline cells, have barely been explored. It has been shown that experimental sepsis changes the sperm methylome, mainly in intergenic regions or development-related genes . Both syThe objectives of intensive care must go well beyond ICU survival and aim to provide critically ill patients with the best achievable quality of life. This includes prevention, treatment and/or palliation of the long-term sequels derived from their ICU stay. The complex organ crosstalk and the pleiotropic effects of most of the responses triggered by critical illness make difficult to find treatments that translate into a clinical benefit. In this difficult scenario, knowledge of the underlying biological mechanisms may allow clinicians and researchers to identify novel biomarkers, therapeutic targets and strategies that ultimately will facilitate the identification and treatment of these long-term sequelae even at early and acute stages, thus contributing to improve long-term outcomes.


In recent years, the scientific and therapeutic fields for rare, genetic central nervous system (CNS) diseases such as leukodystrophies, or white matter disorders, have expanded significantly in part due to technological advancements in cellular and clinical screenings as well as remedial therapies using novel techniques such as gene therapy. However, treatments aimed at normalizing the pathological changes associated with leukodystrophies have especially been complicated due to the innate and variable effects of glial abnormalities, which can cause large-scale functional deficits in developmental myelination and thus lead to downstream neuronal impairment. Emerging research in the past two decades have depicted glial cells, particularly oligodendrocytes and astrocytes, as key, regulatory modulators in constructing and maintaining myelin function and neuronal viability. Given the significance of myelin formation in the developing brain, myelin repair in a time-dependent fashion is critical in restoring homeostatic functionality to the CNS of patients diagnosed with white matter disorders. Using Canavan Disease (CD) as a leukodystrophy model, here we review the hypothetical roles of N-acetylaspartate (NAA), one of the brain's most abundant amino acid derivatives, in Canavan disease's CNS myelinating pathology, as well as discuss the possible functions astrocytes serve in both CD and other leukodystrophies' time-sensitive disease correction. Through this analysis, we also highlight the potential remyelinating benefits of gene therapy for other leukodystrophies in which alternative CNS cell targeting for white matter disorders may be an applicable path for reparative treatment. Leukodystrophies, also known as myelin or white matter (WM) disorders, result from functional mutations in glia or downstream metabolic divergence in neuronal and/or non-neuronal populations  gene primarily in ASPA-expressing mature oligodendrocytes of the Central Nervous System (CNS)  over-expressing the NAA synthesizing enzyme, N-acetyltransferase 8-like (NAT8L), depicted a 4-fold increase of incorporated labeled-glucose into lipids such as triacylglycerols and free fatty acids  receptors in a calcium induced manner, but to a much lesser extent in white matter oligodendrocytes  theory, NAA has also been hypothesized to function as a neuronal osmolyte involved in osmoregulation Baslow, . Given tIn the main hypotheses presented for NAA's myelinating role in the CNS, we see a common thread of liberated acetate from NAA catabolism acting as a precursor for lipid synthesis and energy production. This is interesting because as evidenced by radiolabeled tracing of acetate, astrocytes have previously been identified as acetate transporters from the extracellular space into synaptosomes , into neurons and oligodendrocytes where it is converted back into pyruvate for energy production through the Kreb's cycle, thus maintaining the functional, energic needs of those respective cell populations , and astrocytes  into mature, myelinating oligodendrocytes  was constructed by genomic deletion in the region containing the ASPA gene, resulting in lack of ASPA expression and presence of phenotypical Canavan disease traits such as CNS spongiform degeneration , first constructed in a C57BL/6 background  of pAAV-ASPA in a group of first two CD patients and then later in 14 CD patients , and glial fibrillary acidic protein (GFAP) have been utilized to enhance oligodendrocyte and astrocyte targeting  driven hASPA transgene in mice treated at postnatal day 1 (P1) is adequate for rescuing CD KO mice and furthermore leads to sustained motor and histological recovery into adulthood  in response to TNFα and IL-1β pro-inflammatory cytokines, which act to suppress oligodendrocyte differentiation  to promote oligodendrocyte differentiation  to differentiate into either neural progenitor cells (iNPCs) or oligodendrocyte progenitor cells (iOPCs), it has been elegantly demonstrated that upon stereotaxic injection of iNPCs or iOPCs into brains of In addition to stem-cell therapies, gene therapy for leukodystrophies such as Metachromatic Leukodystrophy (MLD) and Krabbe's disease (KD) have also illustrated the therapeutic benefit of targeting unconventional cell types relative to the core of the pathology. MLD, which results from a deficiency of the lysosomal enzyme arylsulfatase A (ARSA), is a leukodystrophy which exhibits neurological damage with similar phenotypes to that of CD, such as ataxia and seizures, in addition to early infantile or juvenile death Neufeld, . The ARSvia cross-correction approaches, either through enzyme redistribution by substitute cells or by metabolite recompartmentalization and/or processing by neighboring cells. Although metabolic cross-correction mechanisms have not yet been established in Canavan disease, it is possible that such strategies may be therapeutic for non-metabolic leukodystrophies. Therefore, the therapeutic achievements using gene therapy, as well as potentially metabolic treatments, to target alternative glial cell-types, further highlight the advantages of non-traditional cell type targeting for leukodystrophies on a restorative front.Notably, leukodystrophies such as CD, MLD, and KD result from enzyme deficiencies and therefore disease mitigation could involve forms of metabolic restoration Leukodystrophies, which are largely classified according to the affected CNS cell-type in the respective white matter disorder  that is relevant to the content of this manuscript and may result in potential royalties if granted or licensed. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


A high intratumoral nerve density is correlated with poor survival, high metastasis, and high recurrence across multiple solid tumor types. Recent research has revealed that cancer cells release diverse neurotrophic factors and exosomes to promote tumor innervation, in addition, infiltrating nerves can also mediate multiple tumor biological processes via exosomes and neurotransmitters. In this review, through seminal studies establishing tumor innervation, we discuss the communication between peripheral nerves and tumor cells in the tumor microenvironment (TME), and revealed the nerve-tumor regulation mechanisms on oncogenic process, angiogenesis, lymphangiogenesis, and immunity. Finally, we discussed the promising directions of ‘old drugs newly used’ to target TME communication and clarified a new line to prevent tumor malignant capacity. Innervation in some solid tumor is associated with poor outcome.As a malignant factor, intratumoral nerve play an important role in tumor progression, and its density determines tumor malignant capacities.Nerves in tumors can regulate various biological process, such as angiogenesis lymphangiogenesis, immunity and inflammation, Fibroblasts and the extracellular matrix, DNA repair, and oncogene activation.Otherwise, tumor cells also involved in axonogenesis, neurogenesis, and neural reprogramming process in tumor microenvironment.Targeting innervation provides a huge research prospect for tumor therapy.How to achieve clinical treatment through cutting off nerves in solid tumors?How to target nerve-tumor communication to prevent tumor prorgression?What is the major biomolecule in tumor microenvironment mediating axonogenesis, neurogenesis, and neural reprogramming process?Whether clinical neurologic drugs can be a way to treat tumors?Cancer is a major health problem with an increasing impact on all societies. In 2018, there were an estimated 18.1 million new cancer cases and 9.6 million cancer-related deaths globally . PathophA growing body of evidence has suggested that cancer prognosis is related to intratumoral nerve infiltration. This phenomenon occurs in organs or tissues with high innervation, especially in pancreatic cancers(PRC) nearly 100%), 80% of head and neck cancers, 75% of prostate cancers (PC), and 33% of colorectal cancers (CRC) 0%, 80% o, 12, bilDriven by evidence from clinical studies, new translational cancer therapy techniques are being developed to target the interaction between nerves and the TME. In this review, we summarized the role of cancer cells in regulating neurogenesis and described how nerves modulate the TME to promote cancer development and progression. Our overarching aim was to thereby help clinicians and researchers gain a deeper understanding of the mechanisms of nerve-cancer interactions.Since the 16th century, nerves and blood vessels have been observed to move at the same time, and both structures are necessary for maintaining organs . BecauseAs tumor growth requires increased angiogenesis, increased vascular density is one of the earliest histological changes observed in tumor tissues. Previous study showed that as cancer progresses from preneoplastic lesions to dominant cancers, nerve density can almost double to the level seen in the non-neoplastic control group , 39. JusCo-culture experiments revealed that the dorsal root ganglia of mice form bumps on prostate cancer cells, and promote the differentiation of nerve cells to cancer cells , which reduces the caner-nerve distance, thus promoting the formation of a cancer-nerve crosslinking system . FormatiSubsequent breast cancer studies also demonstrated that breast cancer cells promoted axonogenesis. In the N-methyl-N-nitrosourea (MNU)-induced breast cancer rat model, immunofluorescence experiments showed that axons were generated in breast cancer tissues with increased nerve density. Interestingly, sensory and sympathetic nerves were detected in cancer tissues, but parasympathetic nerves were not observed , 44. TheIn a study on the regulation of axonogenesis by tumor cells, Paola et al. found that cancer cells with impaired exosome release had less effect on nerves compared with the control group in vivo, and that inhibition of exosome release also attenuated cancer innervation . EphrinB+ exosomes released by HPV-positive cancer cells have a greater ability to promote cancer innervation in vivo [Taken together, these results suggest that CD9 in vivo . Exosome in vivo . Consist in vivo , 55. Stu in vivo . In addi in vivo . It was  in vivo , 58, theAll these studies suggested a certain correlation between nerves and axonogenesis; however, regardless of the combination of relevant factors, interference with cancer exosome release or blockage of the response ability of nerves to exosomes may prove to be an effective cancer treatment strategy. Although this concept needs to be rigorously tested, if proven to be effective, it has the potential to drive an important clinical transformation.In addition to research on axonogenesis, Ayala et al. proposed that cancer cells could promote neurogenesis . In prosThese studies illustrated how cancers communicate with distant organs and tissues to recruit the cells that they need, and highlight the importance of neurogenesis. However, it is worth noting that cancers can deplete normal cells in the same manner; indeed, several clinical oncology studies have clearly shown that patients who receive chemotherapy are at a greater risk of experiencing brain nerve progenitor cell damage and cognitive decline; however, in patients who do not receive chemotherapy, the depletion of neural progenitor cells by cancer cells may also lead to cognitive impairment . These rIn addition to remote regulation, cancer can also form new neurons from cancer stem cells. Lu et al.  obtainedC176F and p53A161s) increases the number of nerve fibers [Studies have found that exosome-induced neural reprogramming is usually observed during cancer development, suggesting that cancer-derived extracellular vesicle (EV) function in cancer-associated axonogenesis. Exosomes of p53-depleted head and neck cancer cells can carry multiple miRNAs to participate in axonogenesis, while p53 knockout or mutation  and CSCs –78. IntrHere, as an extension, we noted that knockdown of miR-34a not only induced neural reprogramming, but also promoted sensory neurogenesis. Based on a physiological nerve distribution feature, the oral trigeminal nerve is widely distributed, and oral cancer-related pain is the most frequent symptom , 80–82. Thus far, we have summarized the regulation of cancer cells by neighboring nerve cells, but the influence of nerves on cancers is extensive and complex, and the initial research on the neurological impact on cancer biology was inspired by clinical observations indicating a potential link between stress and cancer progression –85. PeopExperimental analyses of animal models in vivo have shown that behavioral stress can accelerate the progression of various cancers, including breast cancer, prostate cancer, ovarian cancer –97, neur+) and endothelial cells (CD31+) was significantly increased in tissues with high-grade prostate intraepithelial neoplasia, suggesting that a shortened physical distance between nerve cells and endothelial cells is associated with an increased malignant capacity of prostate cancer. Interestingly, within the first 18 days of neoplasia, cancer tissues in the control group and the Adrb2 receptor knockout group showed no difference in size, vascular permeability, or hypoxia, whereas after 18 days, the difference was significant [Angiogenesis, the formation of new blood vessels from the existing vascular system, is necessary for cancer growth . In tissnificant .The lymphatic system plays an important role in immune function and can thus influence the course of the disease. Physiologically, the lymphatic system maintains internal environmental stability by guiding cells and solutes from the surrounding interstitial fluid to the lymph nodes via the lymphatic vessels, where they perform immune examinations , 114. In+ T cells, thereby inhibiting its activation, leading to immune escape via immunosuppression, in addition, adrenergic signaling activation impairs CD8+ T-cell mitochondrial function and mass [Lymphocyte activation and infiltration of cancers are key components of the host’s anticancer immune response . Stress and mass . It meanand mass . Interesand mass . TherefoChanges in the three-dimensional structure and composition of the TME greatly affect cancer progression and metastasis –134. ForThe β-adrenergic signaling pathway can inhibit DNA damage repair and p53-related apoptotic processes , 141–143The β-adrenergic signaling pathway stimulates several oncogenic signaling pathways, including those of Src and HER2 (encoded by ERBB2) . In HER2An interesting study found that nervous stress induced the secretion of catecholamines, which are involved in the viral-related carcinogenic process . In B-ceSince the last century, researchers have attempted to cut nerves surgically to block tumor growth and metastasis Table  48, 50,, 150–155Many questions remain to be clarified regarding the regulation of the autonomic nervous system in tumor biology, especially in the parasympathetic nervous system. In the era of targeted therapies, radiation and chemotherapy combined with adjuvant therapeutic strategies, such as β-blocking, can provide a highly synergistic approach to control cancer progression Table  159–173173. In aWhether the use of antipsychotic drugs can prevent neural stress signals and thus inhibit tumor growth still needs to be further explored. Because fluoxetine is an antidepressant, it has anticancer effects in mice , but in Neural signaling has emerged as a therapeutic target after its role in cancer initiation and progression has been further understood , 185. WiChemical denervation in pancreatic cancer has been effective at reducing clinically uncontrollable cancer pain, but as the authors state, this denervation is not permanent . RepeateIn this review, we present evidence that activation of reprogramming signals and regenerative pathways to recruit nerve cells are important factors in the establishment and progression of cancers. The roles of the autonomic and sensory nerve groups in different tumor tissues may vary depending on the type of native tissue as well as the pattern of innervation of the native nerve. With recent advances in genetic engineering and imaging technologies, the role of nerve cells in the TME has progressed; however, many questions remain to be answered. For example; What factors are involved in neurogenesis and axonogenesis at different stages of tumorigenesis? How can we target tumor-specific pathways without affecting the established neural circuits elsewhere in the body? Will the nervous system mediate tumor initiation and development as feedback? Emerging technologies, such as electroceuticals, may help bridge this gap and provide minimally invasive tools –190. Tak


Since the groundbreaking experimental studies on ventilator-induced lung injury (VILI) performed in the 1990s , early rIn this issue of the Journal of Clinical Monitoring and Computing, Pulletz and coworkers present an innovative approach for determining the dynamic regional relative strain (DRRS) with electrical impedance tomography (EIT) during unassisted spontaneous breathing . DRRS isIn their present study, Pulletz and coworkers compared DRRS between a group of spontaneously breathing patients suffering from COVID-19 and a control group of healthy volunteers. They found that elevated pixel values of DRRS were more frequent in COVID-19 patients as compared to healthy controls. As COVID-19 patients may be at increased risk for developing P-SILI , these dThe potential of the new method, however, comes with a few caveats: As a consequence of the normalization procedure, the average DRRS value of the patient’s lungs is always close to 1, regardless of the severity of lung damage or the vigorousness of spontaneous efforts. DRRS therefore only provides regional information on lung areas that are more distended in comparison to the rest of this individual patient’s lungs. If, as a consequence of inhomogeneous lung damage, some lung regions exhibit an above-average stretch, DRRS for these lung regions will assume higher values, indicating relative regional overdistension. If, on the other hand, lung stretch is distributed homogeneously across the whole lung without any particularly overdistended areas, DRRS may remain close to 1 even if the entire lung is already dangerously close to overdistension. Moreover, as the calculation of DRRS is based on a comparison between normalized pixel values of tidal impedance change and EELI, it may be influenced by the application of PEEP. High levels of PEEP may thus lead to potentially lower values of DRRS in lung regions that are already overdistended at end-expiration and whose tidal impedance change is therefore low in comparison to their already-high EELI.Despite these caveats, Pulletz and coworkers present an intriguing approach that adresses a previously unresolved clinical challenge: identifying patients at risk for P-SILI while they are still breathing spontaneously without assistance.


We thank Dr. Landry and colleagues  for theiAdherence to dietary prescriptions is of pivotal importance in studies comparing different nutritional interventions. In our randomized clinical trial, self-reported dietary compliance was assessed by trained dietitians at 2 and 4 weeks of diet using semiquantitative food frequency questionnaires, according to previously described methods ,4. NutriAs already pointed out and discussed , a low-cLastly, participants’ satisfaction with their assigned diet was not formally assessed and quantified in our study. However, none withdrew the diet or complained about its composition during the 4-week intervention, suggesting the feasibility of these dietary prescriptions, at least in the short term. In conclusion, our study emphasizes important differences in the effectiveness of two calorie-restricted eating patterns on weight loss and glucose homeostatic mechanisms in morbidly obese individuals. A great effort has been made to maximize participants’ engagement to nutritional interventions and reduce heterogeneity, with the final aim to minimize the influence of dietary adherence on study findings.


Despite heavy burdens and responsibilities, some caregivers are more likely to cope better with their care responsibilities than others, and this could vary by cultural beliefs and norms on caregiving. This study examined contributing factors of resilience with three racial-ethnic groups . A total of 2,652 caregivers were included from Round 7 of the National Study of Caregiving. Caregiving resilience was defined by higher levels of care demands and higher levels of psychological well-being. Five domains of contributing factors were included: socio-demographic characteristics, context of care, caregivers’ psychological attributes, informal and formal support. Multiple logistic regressions showed that caregivers with higher psychological attribute levels were more likely to be resilient in all three groups. However, unique predictors have also been observed by race-ethnic groups . These findings suggest the need for culturally specific programs to facilitate resilience among caregivers.


Burst-suppression electroencephalography (EEG) patterns of electrical activity, characterized by intermittent high-power broad-spectrum oscillations alternating with isoelectricity, have long been observed in the human brain during general anesthesia, hypothermia, coma and early infantile encephalopathy. Recently, commonalities between conditions associated with burst-suppression patterns have led to new insights into the origin of burst-suppression EEG patterns, their effects on the brain, and their use as a therapeutic tool for protection against deleterious neural states. These insights have been further supported by advances in mechanistic modeling of burst suppression. In this Perspective, we review the origins of burst-suppression patterns and use recent insights to weigh evidence in the controversy regarding the extent to which burst-suppression patterns observed during profound anesthetic-induced brain inactivation are associated with adverse clinical outcomes. Whether the clinical intent is to avoid or maintain the brain in a state producing burst-suppression patterns, monitoring and controlling neural activity presents a technical challenge. We discuss recent advances that enable monitoring and control of burst suppression. In the past century, electroencephalography (EEG) has been used to monitor the human brain during altered states of arousal and conscious experience including wakefulness, sleep, coma, general anesthesia, hallucination, and others . CharactThe phenomenological characteristics of burst suppression  have received considerable attention in the literature. While these properties serve as a useful guide for furthering our understanding of burst suppression in both scientific and clinical contexts, they do not uniquely determine an underlying mechanism responsible for producing burst-suppression patterns, nor do they determine whether or not there exists a single unifying neurophysiological explanation that applies across the numerous medical contexts with which burst suppression is associated. Multiple hypotheses have been proposed in an attempt to identify the relevant neurophysiological mechanisms, most notably the cortical hypersensitivity  and the Despite these open questions, empirical study of the burst suppression pattern and its clinical relevance has led to significant advances in understanding. Recent research has improved our understanding by which anesthetic agents and anesthetic adjuncts act within nociceptive and arousal circuits to create unconsciousness and antinociception during general anesthesia . In paraIn this perspective, we present a current conception of the burst-suppression phenomena. We first establish the scope of this phenomenon by summarizing the medical contexts in which it is observed. We then provide a detailed phenomenological characterization of burst-suppression patterns. Building on the observable characteristics of burst suppression, we discuss how neurophysiology and modeling studies have enabled insight into the biophysics underlying the phenomenon. Finally, we present recent advances in the clinical monitoring of burst-suppression patterns during medical care, and controversy regarding the appropriate use of burst suppression in clinical practice. Throughout, we synthesize evidence from medical studies, neurophysiology studies, and mathematical modeling.Burst suppression occurs in a variety of physiologic and neurological conditions . In geneMajor structural or functional impairments, such as stroke or trauma, can precipitate coma, a state of brain inactivation and profound unresponsiveness . ComatosA) receptors (N-methyl-D-aspartate (NMDA) receptor antagonist administration during GABAergic anesthesia is also known to induce burst-suppression-like patterns , early myoclonic encephalopathy (EME), and Aicardi syndrome (AS) are disorders in which burst suppression patterns have been reported during EEG monitoring . First dSimilar to a deepening state of general anesthesia, a progressive increase in the fraction of time spent in suppression occurs during hypothermia . Burst sBurst suppression can be clearly observed in both the time and frequency domains. This is exemplified in As characterized by There is evidence suggesting that, under burst suppression, the spectral structure of bursting activity resembles that of EEG prior to the onset of burst suppression . In propBurst suppression has commonly been treated as a global brain state, but Drug-specific features of burst suppression have been observed in rodents  and humaThe above characteristics of burst-suppression patterns do not provide a definitive explanation of its underlying neurophysiology. Instead, they establish a set of constraints that should be satisfied by a hypothesized mechanism. The large variation in burst suppression producing conditions creates a challenge for fundamental research aimed at identifying these physiological mechanisms that give rise to burst-suppression EEG patterns. A combination of mathematical modeling and neurophysiology research has led to advances in tracking and understanding the origins of burst suppression. Mathematical models may be used within the scientific method as a means of either (1) generating testable quantitative hypotheses given a conception regarding the mechanistic structure of a physical system; and/or (2) comparing conceptions of the physical system through analysis of empirical evidence . Both apOne prevailing hypothesis is that the burst-suppression EEG pattern results from cortical hypersensitivity. This idea originated with Kroeger et al. , where iA second explanation for the mechanistic underpinnings of burst suppression links suppressions with metabolic dynamics by way of the adenosine triphosphate (ATP)-gated potassium channel . In contGenerative models of burst suppression data can help in justifying proposed mechanisms, formulating further research questions, or providing a framework for performing inference given observed EEG data.Rather than proposing a viable physical mechanism to explain how burst-suppression patterns are generated in humans, early generative models focused solely on developing mathematical equations for creating waveforms with intermittent patterns. More recently, generative models have been developed with the intent of providing evidence supporting a particular mechanistic explanation of burst suppression. To support the metabolic hypothesis, Given the anesthetic conditions and broad range of pathological conditions that give rise to burst suppression, and that many of these conditions pose challenges for collecting controlled experimental data, identifying a definitive and concise physiologic explanation of burst suppression remains challenging. In light of this perspective, Liley et al.  propose Lastly, probabilistic models have been developed to model burst suppression EEG . These mBurst-suppression patterns are produced by high doses of GABAergic anesthetic. High-dose propofol is administered at times to establish a medically induced coma  when coma is considered less deleterious than unregulated neural activity. In the past several decades, understanding of the physiology and effect of burst suppression has led to rapidly changing guidelines for when burst suppression may yield therapeutic neuroprotective benefit in cases of traumatic brain injury, refractory status epilepticus, and during cardiac surgery, and whether instead burst suppression may be harmful. Here, we briefly discuss medical situations in which burst suppression has been used as a neuroprotective tool, and describe how burst suppression may be tracked or controlled in the clinic.Early uses of medically induced burst suppression involved delivering high doses of barbiturates to actively induce burst suppression in order to reduce intracranial pressure in patients with severe traumatic brain injury (TBI) . Burst sPropofol- or barbiturate-induced burst suppression in conjunction with mild hypothermia has been studied for potential therapeutic neuroprotective benefits for patients undergoing cardiac surgery  or intraMedically induced sedation or burst suppression/coma has long been a treatment for refractory status epilepticus (RSE) . SedatioThere have also been indications that sustained epochs of burst suppression during surgical procedures may harm the brain rather than provide neuroprotection, and significant controversy exists regarding the relationship between EEG suppression and postoperative delirium. In one study, duration of intraoperative burst suppression was associated with postoperative cognitive deficits for patients undergoing cardiac surgery . LikewisIrrespective of whether burst suppression is itself advantageous, deleterious, or indicative of other relevant physiological states, it is necessary to be able to reliably detect and track burst-suppression patterns in clinical settings. Algorithms for tracking burst-suppression patterns and segmenting burst and suppression events in EEG have been developed for a variety of purposes. Burst suppression is most commonly quantified by BSR or burst suppression probability  . Either CNS, bispectral index (BIS), and patient state index (PSI) process EEG into a scaled value between 0 and 100 that represents an abstract “depth of anesthesia” irrespective of the drug administered. These algorithms directly incorporate burst suppression tracking either explicitly or implicitly. For example, BIS is perfectly linearly related with BSR for BIS values less than 40 . In a CLAD system, anesthetic infusion is automatically titrated in response to patient signals  to maintain a precise state of anesthesia . For patBurst-suppression EEG patterns arise from a variety of clinical and pathological states, generally portraying a state of profound brain inactivation. However, it is important to note that burst suppression patterns are not monolithic. An emerging body of research has elucidated wide variations in the EEG with regards to local cortical dynamics, suppression duration, periodicity, and substance-specific differences in burst power and amplitude . FurtherAs burst suppression is a complex and multi-faceted phenomenon, there is not a definitive theory of its physiological origins. Nevertheless, the varied approaches to characterizing these origins offer different insights that can be used to guide further burst suppression research. In particular, the experimental studies that gave rise to the cortical hypersensitivity hypothesis  is not iUltimately, a challenge in advancing our understanding of burst-suppression EEG pattern etiology and effects is unifying theoretical and experimental frameworks to test precise hypotheses. Experimental studies have provided valuable data that shape our understanding of what cellular mechanisms might drive burst-suppression EEG patterns, but are challenging to relate to overarching theories of burst suppression generation and effects on patients. Similarly, modeling studies of burst-suppression patterns produce elegant overarching theories and generate data that match experimental observations, but without experimentally testing these models, it is impossible to falsify the hypotheses they posit. Experimentation and modeling must go hand-in-hand. Modeling studies of the hyperpolarization hypothesis must now yield testable predictions, e.g., for how burst/suppression durations change as membrane potential is artificially perturbed. Meanwhile, the metabolic hypothesis must yield specific testable predictions for how burst-suppression patterns change as ATP/glucose availability varies. These hypotheses also fit into large conceptions of burst suppression use in medicine. Support for the metabolic hypothesis is in accordance with burst suppression as a potentially neuroprotective response to a vulnerable state. However, seeking to understand burst-suppression EEG patterns via teleology remains a fraught proposition, and directly testing for effects of burst suppression on postoperative outcomes remains merited. One path to understanding the causes involves examining burst-suppression EEG patterns across the medical scenarios in which they arise . The central challenge in this approach is collecting sufficient data from patients with OS, hypothermia, and TBI, as these conditions are not as amenable to targeted burst-suppression studies as is general anesthesia. Development of “big data” repositories of medical data along with precise burst suppression tracking algorithms may enable conducting massive retrospective pseudo-experiments with precise propensity-matching of study cohorts. Still, the subtlety of the burst-suppression phenomenon and the variety of contexts in which it arises all but ensures that its controversial status is its most concrete feature.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.AS, JA, GS, and EB conceived the perspective. AS, GS, and JA wrote the manuscript. JA and GS analyzed the data and created the figures. All authors reviewed, edited, and approved the manuscript.EB holds founding shares in PASCALL, a company developing physiological control systems. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Literature in the field of stem cell therapy indicates that, when stem cells in a state of single-cell suspension are injected systemically, they show poor in vivo survival, while such cells show robust cell survival and regeneration activity when transplanted in the state of being attached on a biomaterial surface. Although an attachment-deprived state induces anoikis, when cell-surface engineering technology was adopted for stem cells in a single-cell suspension state, cell survival and regenerative activity dramatically improved. The biochemical signal coming from ECM (extracellular matrix) molecules activates the cell survival signal transduction pathway and prevents anoikis. According to the target disease, various therapeutic cells can be engineered to improve their survival and regenerative activity, and there are several types of biomaterials available for cell-surface engineering. In this review, biomaterial types and application strategies for cell-surface engineering are presented along with their expected efficacy. Since it was discovered that various regenerative cell sources can exert essential functions to promote the regeneration of tissues damaged by injury or disease, the number of clinical applications of cell therapeutic agents has continued to increase. Although many cell-based therapies can provide valuable functionality that cannot be exerted by any other therapeutic options, the duration of the efficacy could be limited due to the fact that an in vivo environment is not favorable for the survival of the transplanted cells. Cell encapsulation can increase the duration of cell survival by providing protection from unfavorable environments.Escherichia coli ,9,557,9,Diabetes patients suffer from a lack of control over glucose metabolism caused by insulin insufficiency. Type I diabetes is caused by autoimmune-mediated beta-cell destruction, and the current treatment regimen for diabetes relies on the administration of exogenous insulin by frequent injections. Natural islet beta-cells sense blood glucose levels and respond by producing insulin for exactly the right duration to control blood glucose levels within a strict physiological range, while exogenous insulin delivery often fails to control blood glucose levels. Pancreatic islet transplantation can be an effective treatment for achieving naturally controlled insulin production in response to blood glucose levels.In experimental conditions, the xenogenic transplantation of hESC-derived β-cells into mice ameliorated hyperglycemia in diabetic mice . After tAllogeneic beta-cell transplantation might provide a functional restoration of islet beta-cells and a promising therapy for type I diabetes. However, allogeneic cell transplantation necessitates life-long immune suppression, which might cause graver side effects. . To solvMicroencapsulation with high-mannuronic-acid alginate allowed for the prolonged survival of allogeneic transplanted islets in diabetic mice ,28. WhilDiseases associated with the vascular system, particularly those associated with cardiac and cerebrovascular disease is the leading cause of death worldwide. The current therapeutic approach includes pharmacological treatment that can involve side effects and surgical revascularization. Because these approaches cannot completely reverse pathophysiology, many experimental therapeutic approaches utilize endothelial progenitor cells (EPCs) to treat cardiovascular diseases (CVDs). Active EPCs served as a potent source of the essential mediators of a new vessel formation .In a murine model of peripheral limb ischemia, human EPC injections improved tissue reperfusion, and limb salvage rate was significantly increased . In clinHowever, a low retention rate due to cell scattering after injection was still a major concern. To stabilize cell retention and survival, various approaches were employed with EPC transplantation. Hyaluronan (HA) was known to increase the proliferation of human umbilical vein endothelial cells (HUVECs) and protect apoptosis. Injecting HUVECs with HA showed a significantly improved outcome in restoring blood perfusion and salvaging the ischemic limb when compared with HUVECs injected without HA .The use of micro-encapsulation provided a cyto-protective effect to endothelial cells. When the elements of the encapsulation were composed to exert multifunctionality, encapsulated cells proliferated in a time-dependent manner and eventually released from the encapsulation and migrated to a nearby site in longer time points. The injection of multifunctional microgels encapsulating endothelial cells and growth factors induced neovascularization in animal models of hindlimb ischemia ,63.Although liver tissue shows the great regenerative capacity and spontaneous recovery upon mild damage or partial hepatectomy, acute/chronic liver failure, metabolic disorders such as Crigler-Najjar syndrome type 1 (CN-2), or urea cycle defects with hepatic basis can be a life-threatening situation, and organ transplantation is needed .If cell therapy could replace organ transplantation, it could be a better therapeutic option because cell therapy involves a less invasive transplantation procedure, and the cryo-preserved cell source makes it immediately available in an emergency . An in vHowever, the same challenges exist as in the case of islet beta-cell encapsulation. The immunosuppression regimen to evade immune rejection is recognized as a high-risk factor for patients with coagulopathy. Additionally, a sufficient amount of target area needs to be secured for safe engraftment and further growth of the organ, which will be essential for patients’ long-term survival. Therefore, further research is needed to meet those challenges for in vivo transplantation and practical utilization in clinical situations.Neural progenitor cells (NPCs) or neural stem cells (NSCs) are stem cells that can differentiate into the major cell types of the central nervous system. The potential of NPCs to directly replace damaged tissue make it a promising therapeutic cell type for many neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, or spinal cord damage.Although NPCs have high therapeutic potential, they show an inferior survival rate upon transplantation. Additionally, the biochemical and biomechanical environment is important for retaining their functionality, such that neuronal stem cells (NSCs), including NPCs, are maintained in a spheroid culture to retain their differentiation potential. Especially, matrix components generated by cells during spheroid culture induce three-dimensional cell–cell interactions and cell–ECM interactions, which play important roles in cells’ long-term survival and stemness . When NPAnimal cells in culture are exposed to various stresses coming from the culture environment and are susceptible to damages that eventually lead to cell death. Among these, mechanical stress can cause direct damage to the cultured cells. In mild degrees, mechanical stress can activate cells to survive  or expreEven simple centrifugation could be critically detrimental for mechanical-stress-sensitive cell types such as hepatocytes or neuronal cells. A study with hepatocyte carcinoma showing extremely high cell death after four rounds of centrifuge indicates that hepatocytes are highly susceptible to mechanical stress . Cell cuThe high susceptibility to mechanical stress is based on the fact that the lipid bilayer of the cell plasma membrane is constructed by a hydrophobic interaction between phospholipid molecules. However, hepatocytes, highly susceptible to mechanical stress in an attachment-deprived state, show mechanical stability inside the liver tissue surrounded by matrix molecules. Likewise, cell surface modification by the deposition of hydrogels or matrix molecules can dramatically reduce mechanical insult by providing mechanical stability. When HepG2 cells (hepatocyte carcinoma) were coated with FN-gelatin or Col IV-LN by LbL assembly, more than 85% of the cells survived after nine rounds of centrifugation, while the non-coated control group showed poor cell survival (6%) . SystemiWhen cells make attachments to the substrate, ECM molecules bind to their corresponding receptor and transduce survival signals to the cells. Therefore, when the cells are detached from the stroma and are left in the attachment-deprived state for a certain duration, the cells eventually undergo anoikis, a specific type of apoptosis caused by an attachment-deprived state. Most cell surface-located matrix receptors such as integrin or CD44 can activate survival signaling pathways leading to Akt activation. Therefore, cell encapsulation mimicking the interaction between matrix molecules and matrix receptors on the cell surface can result in Akt activation and significantly increase the survival of cells in the attachment-deprived state. When BMSCs were surface-modified by LbL assembly composed of poly-L-lysine and hyaluronic acid, the cell survival rate and Akt activation were significantly increased . When thDuring the cryopreservation of animal cells, a cryoprotective agent (CPA) such as DMSO was used to suppress the damage caused by ice crystal formation. Although there is some controversy about the active concentrations, the CPA has a negative effect on cell activity-inducing proliferation arrest or cytotoxicity. Many reports show that a CPA such as DMSO results in reduced proliferation at a concentration of around 1–2%, and a concentration over 10% causes the cell number to decrease due to cytotoxicity . HoweverThe cryopreservation of encapsulated cells might be utilized for the preservation of therapeutic cells with transplantation purposes. Alginate-encapsulated hepatocytes induced promising outcomes when they were intra-peritoneally transplanted to an acute liver failure animal model, which is a life-threatening condition without liver transplantation ,23. As aThe development of cell therapeutic agents is intended for a pathological situation where ordinary drug-based therapy fails to cure, and it is highly likely that the cell sources from the highly pathological site cannot yield promising effects for regeneration. In the case of type I diabetes, islet β-cells in the pancreas cannot produce enough insulin to metabolize glucose. To avoid frequent injection of insulins and find radical treatment, the possibility of allogeneic β-cell transplantation has long been investigated . For allNot only for stroma-attached islet β-cells, but also circulating blood cells such as red blood cells (RBCs) were surface-modified to evade host immune rejection or blood coagulation induced by antibodies against the corresponding ABC type . Poly-doIn some studies, encapsulated cells showed no increase in cell number during in vitro culture periods. During four days of culture, HeLa cells and human BM-MSCs encapsulated in an enzyme-responsive polymer nano-shell maintained a surviving state without cell proliferation, while non-incapsulated HeLa cells and BM-MSCs showed an approximately 10-fold and 8-fold increase in cell number, respectively . In otheWhen encapsulation is not stiff enough to repress cell expansion and refrain the cell activity, the encapsulated cells hatch. The incorporation of hyaluronic acid in alginate-based encapsulation provided a softer spot in the encapsulated structure, and the cells hatched out of the encapsulation, while the cells encapsulated in the alginate bead stayed inside during the other culture . The incWhen MSCs encapsulated in hydrogel composed of agarose, dextran sulfate, and collagen were transplanted to the myocardial infarction site, encapsulated cells were slowly released and integrated into adjacent tissues. This slow release of cells showed a beneficial effect in various aspects. The released cells easily integrated into adjacent tissues when compared with cells transplanted in an attachment-deprived single cell state. The gradual integration of released cells proceeded without provoking abrupt changes or a foreign body response, resulting in active participation in the wound healing process in the myocardial infarction site .According to the encapsulation strategy and the type of employed biomaterials, the activity of cells in encapsulation can be controlled. Cells could remain stable without significant changes of the proliferative state if stiff biomaterials were adopted for encapsulation ,21,42. BBasically, stem cells residing in the body are close to the state of being dormant and non-differentiated. The signals coming from the environment activate the stem cells to proliferate and get differentiated to show functionality. Many previous studies have shown that those environmental signals can be a chemical moiety  or a mecHowever, cells for a therapeutic purpose are subjected to scrutiny for their safety and stability in their functionality. Therefore, the characteristics of encapsulated cells during dormancy and after hatching need to be defined in detail.Classical approaches of tissue engineering include cell seeding to a porous scaffold of a desired shape and volume. If the target tissue for therapy is independent of formulating shape and dimension, encapsulated cells can serve as a good strategy for the recovery of tissue functionality. The transplantation of islet beta-cells and hepatocytes in their encapsulated stats can be good examples.As cell spheroids or aggregates are increasingly used as a building block for the tissue engineering strategy ,73, encaWhen designing cell encapsulation, the conditions required for the functionality of the target tissue should be considered. In the case of reconstructing cartilage tissue, maintaining cell–cell contact is critical . FlexiblThe clinical application of cell therapy can save repetitive drug injections or acute symptoms, which can be exemplified by type I diabetes or graft-versus-host disease (GVHD), respectively. In the case of injected cells, the modulation of cell activity after the injection is beyond control. Therefore, stabilizing cell quality even after the injection or transplantation can result in augmented therapeutic activity. The ultimate goal of developing technology for potentiated cell therapy is to be utilized for human welfare. Therefore, a clinical trial of an encapsulated cell therapeutic agent needs regulatory approval, which requires scrutiny for its safety and therapeutic effects. The complexity of the method can result in challenges in the scale-up manufacturing of the therapeutic agent. Likewise, the complexity of the therapeutic agent leads to regulatory complexity . Therefo


Hyperspectral imaging (HSI) in situ core scanning has emerged as a valuable and novel tool for rapid and non-destructive biogeochemical analysis of lake sediment cores. Variations in sediment composition can be assessed directly from fresh sediment surfaces at ultra-high-resolution (40–300 μm measurement resolution) based on spectral profiles of light reflected from sediments in visible, near infrared, and short-wave infrared wavelengths (400–2500 nm). Here, we review recent methodological developments in this new and growing field of research, as well as applications of this technique for paleoclimate and paleoenvironmental studies. Hyperspectral imaging of sediment cores has been demonstrated to effectively track variations in sedimentary pigments, organic matter, grain size, minerogenic components, and other sedimentary features. These biogeochemical variables record information about past climatic conditions, paleoproductivity, past hypolimnetic anoxia, aeolian input, volcanic eruptions, earthquake and flood frequencies, and other variables of environmental relevance. HSI has been applied to study seasonal and inter-annual environmental variability as recorded in individual varves  or to study sedimentary records covering long glacial–interglacial time-scales . The scientific investigation of sediment deposited in lakes can provide important and diverse information about past changes in environmental conditions, as well as human impacts to the natural environment, over timescales ranging from the recent past to over 100,000 years . Lake seThis ultra-high measurement resolution is especially valuable in studies of lake sediments, because spatial resolution, along with sedimentation rate, determines the temporal resolution of the data obtained from sediments. To convert sediment depths into ages and determine sedimentation rates, a variety of geochronological techniques can be used, including radiocarbon dating  and varvHSI of lake sediment cores is a novel technique rapidly growing in interest, particularly due to its rapid acquisition of ultra-high-resolution datasets. HSI core scanning has utilized cameras operating in the visible and near infrared  and short wave infrared  wavelengths to detect sedimentary components and properties such as organic matter , sedimenIn this review, we summarize the state-of-the-art application of HSI to lake sediment cores. We present the development of the technique from VNIR reflectance spectroscopy to HSI core-scanning. Then, we describe the available equipment and general methodological workflow used for in situ HSI core scanning and data processing. Next, we review common biogeochemical interpretations of sediment reflectance spectra. The potential and limitations of the HSI core-scanning method are discussed. Finally, we assess the peer-reviewed literature on HSI core scanning of lake sediments and present several key research themes where the application of HSI has led to important insights relevant for paleoenvironmental research.It has been recognized for a long time that sediment color in the visible (VIS) range  contains valuable information about organic and inorganic sediment components, lithotypes, and depositional environments. The pioneering work of Swain , Züllig Deaton and Balsam  provideda and derivatives , carotenoids (index: RABD510), and lithogenic components . Spectrolino point measurements were taken directly from the fresh sediment surface (in situ) at a resolution of 2 mm. In a case study on a marine core from offshore Peru, Rein et al. . Se. Se47].  to grow ,67. Thera to reconstruct past lake mixing regimes. Detectable concentrations of Bphe throughout the varve year indicate the continuous growth of purple sulfur bacteria and are interpreted as being indicative of year-round water-column stratification .,53.a (Bpa (Bphe) data, when compared with archaeological information and high-resolution pollen data, show that anoxic and meromictic (meromixis is defined as multi-year periods with no complete lake mixing) periods occurred during times when the lakeshore was not occupied by pile-dwellers and forest coverage was most extensive. The dense forest shielded the small, deep, lake from wind, which led to strong density stratification in the water column and anoxic conditions ideal for Bphe-producing purple sulfur bacteria.Lake Moossee, Switzerland, provides a clear example of a strong relationship between human land use and lake mixing  43]. HS. HS43]. In a more arid environment, Lake Son Kol in Kyrgyzstan provides an example from a large, shallow lake. This lake featured a period of extensive anoxia from about 8500–5200 cal yr BP, driven by warmer temperatures and increased deposition of organic matter, which increased oxygen consumption rates .Reconstructions of aquatic productivity, as recorded by HSI-inferred chloropigments (TChl) in several small temperate lakes, suggest that these lakes experienced gradual increases in productivity during the stable environmental conditions of the Holocene prior to human disturbance ,50,51,53The high spatial  resolution of HSI data, particularly from varved sediments, provides unique information about rapid environmental changes and short-lived events. For instance, mass movements, such as slumps and turbidity currents, are known to disturb stratification within lakes. At Lake Żabińskie, the reestablishment of lake stratification following a mass movement event could be constrained to within 2–5 years following the event  53]. Al. Al53]. Sediment stratigraphy represents the classification of sediment layers based on their properties and is fundamental for paleoenvironmental research because changes in sediment properties are driven by changing environmental conditions. Hyperspectral imaging of lake sediments has proven useful for discriminating stratigraphic changes at scales ranging from micrometers to meters. A common approach is to identify reference areas on a core image that represent a certain sediment type (lithotype). Then, an image classification algorithm is used to identify other areas in the sediment core with similar properties. This approach was used to discriminate layers deposited during flood events from continuous background sedimentation at Lake Bourget, France . RecentlBiogeochemical data derived from HSI methods have also been used in conjunction with other high-resolution datasets  to identify stratigraphic changes in sediment cores ,49,53. THSI offers several clear advantages in comparison with conventional analytical techniques that require time-consuming and destructive laboratory analysis. HSI provides data at an extremely high spatial resolution (40–200 μm) with relatively minimal time, labor, and cost. Additionally, spatial variations in sedimentary characteristics captured by HSI can provide important information about sedimentation and diagenetic processes, as well as the representativeness of a sample area. Sediments that feature substantial variability at μm-to-cm scales are particularly well suited for HSI analysis because conventional methods are unable to capture such high-resolution spatial  variability. Varved sediments preserve annual variations in sediment composition and are particularly well suited for HSI. Considering that lake sediments typically accumulate at rates of approximately 0.1 to 10 mm per year, the 0.04–0.2 mm resolution of HSI data is ideal for studying seasonal-to-annual-scale variability. Nevertheless, HSI is efficient for investigating long records covering tens of meters and thousands of years (or greater). HSI is most valuable for studies that require high-resolution data, including studies on high-frequency climate oscillations , thresholds and tipping points, and short-lived events . HSI analysis is most effective when complemented by traditional sedimentological analysis, X-ray florescence core scanning, HPLC analysis, or other methods . These t670 index has been applied in a wide variety of sites and, therefore, is expected to successfully track changing aquatic production at most sites [670 to chloropigment concentrations. Biogeochemical analysis of sediments using HSI is limited by inherent uncertainty related to the interpretation of reflectance spectra. Similar spectral features can be produced by multiple substances or mixtures of substances. Therefore, HSI data should be validated using independent information. The use of established indices in well-characterized sediments may be possible without independent validation. However, significant questions remain about calibration and predictive models based on HSI data. For example, the RABDst sites . HoweverHSI analysis of sediments can be limited or affected by the characteristics of lake sediments. Water-saturated sediments can cause interference through spectral scattering, and water causes prominent absorption bands in the SWIR range that interfere with the reflectance signal of the sediments. Drying sediments may be useful in some cases, though this typically leads to cracking/deformation of intact sediment cores. Degradation and oxidation of sediments during core opening and storage should also be considered. These effects may lead to the loss of organic components or variations in the reflectance data due to oxidation during storage. Certain sediments may be too dark to obtain reliable data . Low reflectance can lead to biases in calibration models applied to spectral indices for pigments . The proResearch on HSI applied to lake sediments is still in its initial development, and much potential remains for advancement in data processing techniques and the interpretation of large HSI datasets. Continued research can be expected to include new applications, better interpretation models of sediment reflectance, and advanced numerical tools applied to HSI datasets.In this review, we summarized the recent developments of in situ hyperspectral imaging applied to lake sediment cores for biogeochemical analysis. This promising field of research is growing rapidly since the first published demonstration of the technique in 2014 . HSI offTo date, the majority of paleoenvironmental reconstructions based on HSI data have utilized spectral indices that quantify pigment groups . Such indices can be calibrated to concentrations measured on discrete samples using conventional wet-chemical techniques. HSI-inferred pigment records have been used to track changes in lake productivity, organic matter sources, and lake mixing over thousands of years, leading to important insights about relationships between climate, land cover, and lake ecosystems. These studies provide examples of the potential of HSI for paleoenvironmental research, which can only be expected to grow in the future.Several areas of opportunity regarding HSI applied to lake sediments should be considered in future research. One important task is to assess to what extent methods can be universally applied to different sites with variable environments and sedimentary compositions. For instance, can universal calibration models be established to convert HSI data to sedimentary properties of interest? This likely requires better standardization of methods between various research groups as this field of study continues to grow. Expanding the geographic scope of HSI investigations of sediment across the globe is an important goal. Currently, the vast majority of HSI studies on lake sediment have been from lakes in Europe. Additionally, HSI should be applied to records covering longer time periods. The longest published HSI record to date is 20,000 years . Applyin