Chronic unpredictable stress induces autophagic death of adult hippocampal neural stem cells.

Chronic psychological stress is a critical factor for neurological complications like anxiety disorders, dementia, and depression. Our previous results show that chronic restraint stress causes cognitive deficits and mood dysregulation by inducing autophagic death of adult hippocampal neural stem cells (NSCs). However, it is unknown whether other models of psychological stress also induce autophagic death of adult hippocampal NSCs. Here, we show that chronic unpredictable stress (CUS) for 10 days impaired memory function and increased anxiety in mice. Immunohistochemical staining with SOX2 and KI67 revealed a significant reduction in the number of NSCs in the hippocampus following exposure to CUS. However, these deficits were prevented by NSC-specific, inducible conditional deletion of Atg7. These findings suggest that autophagic death of adult hippocampal NSCs is a critical pathogenic mechanism underlying stress-induced brain disorders.

The Role of Cancer and Somatic Stem Cells in the Anti-Inflammatory and Antitumor Effects of Aconitum baicalense Extract on Experimental Breast Cancer.

We studied the effects of the extract of the terrestrial part of Aconitum baicalense in BALB/c female mice at the early stages after the injection of N-methyl-N-nitrosourea (MNU). The extract reduced inflammatory activity and tumor growth in the mammary gland. The antitumor and anti-inflammatory effects of the extract are based on the inhibition of cancer stem cells, hematopoietic stem cells, and hematopoietic progenitor cells that promote inflammation. The extract of A. baicalense disrupted the recruitment of epithelial progenitor cells and angiogenesis precursors to the mammary gland preventing neovascularization and transformation of epithelial cells into tumor cells.

Intestinal Epithelial Responses to IL-17 in Adult Stem Cell-derived Human Intestinal Organoids.

BACKGROUND: Th17 cells and their signature cytokine, interleukin-17A [IL-17], are considered as the main pathogenic factors in inflammatory bowel diseases [IBDs]. However, IL-17 neutralising antibodies, a theoretically curative medication for IBDs, paradoxically aggravated intestinal inflammation. The mechanisms by which IL-17 mediates the protective and pathological effects of IL-17 remain unclear in the intestinal epithelium. METHODS: The intestinal epithelial responses induced by IL-17 were evaluated using the human small intestinal organoid [enteroid] model. RESULTS: Organoid-forming efficiency, cell viability, and proliferation of enteroids were decreased in proportion to IL-17 concentration. The IL-17 induced cytotoxicity was predominantly mediated by pyroptosis with activation of CASP1 and cleavage of GSDMD. Bulk RNA-sequencing revealed the enrichment of secretion signalling in IL-17 treated enteroids, leading to mucin exocytosis. Among its components, PIGR was up-regulated significantly as the concentration of IL-17 increased, resulting in IgA transcytosis. Mucin exocytosis and IgA transcytosis have a protective role against enteric pathogens. Single-cell RNA sequencing identified that CASP1-mediated pyroptosis occurred actively in intestinal stem cells [ISCs] and enterocytes. IL-17 neutralising antibody completely restored IL-17 induced cytotoxicity, but suppressed mucin secretion and IgA transcytosis. Pyroptosis inhibition using CASP1 inhibitors significantly improved IL-17 induced cytotoxicity without diminishing its beneficial effects. CONCLUSIONS: IL-17 induces the pyroptosis of ISCs and enterocytes, as well as mucin secretion of goblet cells and IgA transcytosis of epithelial cells. Paradoxical gastrointestinal effects of IL-17 neutralising antibodies may be associated with inhibition of mucin secretion and IgA transcytosis. The inhibition of pyroptosis using CASP1 inhibitors prevents IL-17 induced cytotoxicity without compromising its beneficial effects.

The neurogenic niche in Alzheimer's disease.

Adult hippocampal neurogenesis is the process of generation and functional incorporation of new neurons, formed by adult neural stem cells in the dentate gyrus. Adult hippocampal neurogenesis is highly dependent upon the integration of dynamic external stimuli and is instrumental in the formation of new spatial memories. Adult hippocampal neurogenesis is therefore uniquely sensitive to the summation of neuronal circuit and neuroimmune environments that comprise the neurogenic niche, and has powerful implications in diseases of aging and neurological disorders. This sensitivity underlies the neurogenic niche alterations commonly observed in Alzheimer's disease, the most common form of dementia. This review summarizes Alzheimer's disease associated changes in neuronal network activity, neuroinflammatory processes, and adult neural stem cell fate choice that ultimately result in neurogenic niche dysfunction and impaired adult hippocampal neurogenesis. A more comprehensive understanding of the complex changes mediating neurogenic niche disturbances in Alzheimer's disease will aid development of future therapies targeting adult neurogenesis.

Ongoing repair of migration-coupled DNA damage allows planarian adult stem cells to reach wound sites.

Mechanical stress during cell migration may be a previously unappreciated source of genome instability, but the extent to which this happens in any animal in vivo remains unknown. We consider an in vivo system where the adult stem cells of planarian flatworms are required to migrate to a distal wound site. We observe a relationship between adult stem cell migration and ongoing DNA damage and repair during tissue regeneration. Migrating planarian stem cells undergo changes in nuclear shape and exhibit increased levels of DNA damage. Increased DNA damage levels reduce once stem cells reach the wound site. Stem cells in which DNA damage is induced prior to wounding take longer to initiate migration and migrating stem cell populations are more sensitive to further DNA damage than stationary stem cells. RNAi-mediated knockdown of DNA repair pathway components blocks normal stem cell migration, confirming that active DNA repair pathways are required to allow successful migration to a distal wound site. Together these findings provide evidence that levels of migration-coupled-DNA-damage are significant in adult stem cells and that ongoing migration requires DNA repair mechanisms. Our findings reveal that migration of normal stem cells in vivo represents an unappreciated source of damage, which could be a significant source of mutations in animals during development or during long-term tissue homeostasis.

One stem cell program to rule them all?

Many species of animals have stem cells that they maintain throughout their lives, which suggests that stem cells are an ancestral feature of all animals. From this, we take the viewpoint that cells with the biological properties of 'stemness'-self-renewal and multipotency-may share ancestral genetic circuitry. However, in practice is it very difficult to identify and compare stemness gene signatures across diverse animals and large evolutionary distances? First, it is critical to experimentally demonstrate self-renewal and potency. Second, genomic methods must be used to determine specific gene expression in stem cell types compared with non-stem cell types to determine stem cell gene enrichment. Third, gene homology must be mapped between diverse animals across large evolutionary distances. Finally, conserved genes that fulfill these criteria must be tested for role in stem cell function. It is our viewpoint that by comparing stem cell-specific gene signatures across evolution, ancestral programs of stemness can be uncovered, and ultimately, the dysregulation of stemness programs drives the state of cancer stem cells.

Analysis of Thyroid Hormone Receptor α-Knockout Tadpoles Reveals That the Activation of Cell Cycle Program Is Involved in Thyroid Hormone-Induced Larval Epithelial Cell Death and Adult Intestinal Stem Cell Development During Xenopus tropicalis Metamorphosis.

Background: There are two highly conserved thyroid hormone (triiodothyronine [T3]) receptor (TR) genes, TRα and TRß, in all vertebrates, and the expression of TRα but not TRß is activated earlier than T3 synthesis during development. In human, high levels of T3 are present during the several months around birth, and T3 deficiency during this period causes severe developmental abnormalities including skeletal and intestinal defects. It is, however, difficult to study this period in mammals as the embryos and neonates depend on maternal supply of nutrients for survival. However, Xenopus tropicalis undergoes a T3-dependent metamorphosis, which drastically changes essentially every organ in a tadpole. Of interest is intestinal remodeling, which involves near complete degeneration of the larval epithelium through apoptosis. Concurrently, adult intestinal stem cells are formed de novo and subsequently give rise to the self-renewing adult epithelial system, resembling intestinal maturation around birth in mammals. We have previously demonstrated that T3 signaling is essential for the formation of adult intestinal stem cells during metamorphosis. Methods: We studied the function of endogenous TRα in the tadpole intestine by using knockout animals and RNA-seq analysis. Results: We observed that removing endogenous TRα caused defects in intestinal remodeling, including drastically reduced larval epithelial cell death and adult intestinal stem cell proliferation. Using RNA-seq on intestinal RNA from premetamorphic wild-type and TRα-knockout tadpoles treated with or without T3 for one day, before any detectable T3-induced cell death and stem cell formation in the tadpole intestine, we identified more than 1500 genes, which were regulated by T3 treatment of the wild-type but not TRα-knockout tadpoles. Gene Ontology and biological pathway analyses revealed that surprisingly, these TRα-regulated genes were highly enriched with cell cycle-related genes, in addition to genes related to stem cells and apoptosis. Conclusions: Our findings suggest that TRα-mediated T3 activation of the cell cycle program is involved in larval epithelial cell death and adult epithelial stem cell development during intestinal remodeling.

Repolarization studies using human stem cell-derived cardiomyocytes: Validation studies and best practice recommendations.

Human stem cell-derived cardiomyocytes (hSC-CMs) hold great promise as in vitro models to study the electrophysiological effects of novel drug candidates on human ventricular repolarization. Two recent large validation studies have demonstrated the ability of hSC-CMs to detect drug-induced delayed repolarization and "cellrhythmias" (interrupted repolarization or irregular spontaneous beating of myocytes) linked to Torsade-de-Pointes proarrhythmic risk. These (and other) studies have also revealed variability of electrophysiological responses attributable to differences in experimental approaches and experimenter, protocols, technology platforms used, and pharmacologic sensitivity of different human-derived models. Thus, when evaluating drug-induced repolarization effects, there is a need to consider 1) the advantages and disadvantages of different approaches, 2) the need for robust functional characterization of hSC-CM preparations to define "fit for purpose" applications, and 3) adopting standardized best practices to guide future studies with evolving hSC-CM preparations. Examples provided and suggested best practices are instructional in defining consistent, reproducible, and interpretable "fit for purpose" hSC-CM-based applications. Implementation of best practices should enhance the clinical translation of hSC-CM-based cell and tissue preparations in drug safety evaluations and support their growing role in regulatory filings.

Persistence of a regeneration-associated, transitional alveolar epithelial cell state in pulmonary fibrosis.

Stem cells undergo dynamic changes in response to injury to regenerate lost cells. However, the identity of transitional states and the mechanisms that drive their trajectories remain understudied. Using lung organoids, multiple in vivo repair models, single-cell transcriptomics and lineage tracing, we find that alveolar type-2 epithelial cells undergoing differentiation into type-1 cells acquire pre-alveolar type-1 transitional cell state (PATS) en route to terminal maturation. Transitional cells undergo extensive stretching during differentiation, making them vulnerable to DNA damage. Cells in the PATS show an enrichment of TP53, TGFß, DNA-damage-response signalling and cellular senescence. Gain and loss of function as well as genomic binding assays revealed a direct transcriptional control of PATS by TP53 signalling. Notably, accumulation of PATS-like cells in human fibrotic lungs was observed, suggesting persistence of the transitional state in fibrosis. Our study thus implicates a transient state associated with senescence in normal epithelial tissue repair and its abnormal persistence in disease conditions.

TNF­α promotes the malignant transformation of intestinal stem cells through the NF­κB and Wnt/ß­catenin signaling pathways.

Cancer stem cells are responsible for tumorigenesis, progression, recurrence and metastasis. Intestinal stem cells (ISCs) are regarded as the origin of intestinal neoplasia. Inflammation also serves an important role in intestinal neoplasia. To explore the molecular mechanisms underlying the inflammation­mediated induction of intestinal tumorigenesis, the present study investigated the function of tumor necrosis factor (TNF)­α in the malignant transformation of ISCs. NCM460 spheroid (NCM460s) cells with higher expression of stem cell genes, such as Oct4, Nanog, Sox2 and Lgr5, and with a higher ratio of CD133+, were obtained from NCM460 cells in serum­free medium. TNF­α accelerated cell proliferation, migration and invasion, induced chemotherapy resistance and the epithelial­mesenchymal transition. NF­κB and Wnt/ß­catenin pathways were activated in TNF­α­induced inflammatory responses, leading to the nuclear translocation of p65 and ß­catenin, as well as promoter activity of NF­κB and TCF/LEF transcription factors. It was further demonstrated that TNF­α­induced activation of the NF­κB and Wnt/ß­catenin signaling pathways, as well as the upregulation of proinflammatory cytokines, were significantly suppressed by p65­knockdown. Notably, PDTC, an inhibitor of NF­κB signaling, reversed TNF­α­induced activation of the NF­κB and Wnt/ß­catenin pathways. A similar role was observed for IWP­2, an inhibitor of Wnt/ß­catenin signaling. Collectively, these results demonstrated that the NF­κB and Wnt/ß­catenin pathways were activated to promote TNF­α­induced malignant transformation of ISCs, in which these two pathways cross­regulated each other.

The impact of ageing on lipid-mediated regulation of adult stem cell behavior and tissue homeostasis.

Adult stem cells sustain tissue homeostasis throughout life and provide an important reservoir of cells capable of tissue repair in response to stress and tissue damage. Age-related changes to stem cells and/or the specialized niches that house them have been shown to negatively impact stem cell maintenance and activity. In addition, metabolic inputs have surfaced as another crucial layer in the control of stem cell behavior (Chandel et al., 2016; Folmes and Terzic, 2016; Ito and Suda, 2014; Mana et al., 2017; Shyh-Chang and Ng, 2017). Here, we will present a brief review of how lipid metabolism influences adult stem cell behavior under homeostatic conditions and speculate on how changes in lipid metabolism may impact stem cell ageing. This review considers the future of lipid metabolism research in stem cells, with the long-term goal of identifying mechanisms that could be targeted to counter or slow the age-related decline in stem cell function.

Emerging Mechanisms by which EMT Programs Control Stemness.

Tissue regeneration relies on adult stem cells (SCs) that possess the ability to self-renew and produce differentiating progeny. In an analogous manner, the development of certain cancers depends on a subset of tumor cells, called cancer stem cells (CSCs), with SC-like properties. In addition to being responsible for tumorigenesis, CSCs exhibit elevated resistance to therapy and thus drive tumor relapse post-treatment. The epithelial-mesenchymal transition (EMT) programs promote SC and CSC stemness in many epithelial tissues. Here, we provide an overview of the mechanisms underlying the relationship between stemness and EMT programs, which may represent therapeutic vulnerabilities for the treatment of cancers.

NCoR1 Protects Mice From Dextran Sodium Sulfate-Induced Colitis by Guarding Colonic Crypt Cells From Luminal Insult.

BACKGROUND & AIMS: Colonic stem cells are essential for producing the mucosal lining, which in turn protects stem cells from insult by luminal factors. Discovery of genetic and biochemical events that control stem cell proliferation and differentiation can be leveraged to decipher the causal factors of ulcerative colitis and aid the development of more effective therapy. METHODS: We performed in vivo and in vitro studies from control (nuclear receptor corepressor 1 [NCoR1F/F]) and intestinal epithelial cell-specific NCoR1-deficient mice (NCoR1ΔIEC). Mice were challenged with dextran sodium sulfate to induce experimental ulcerative colitis, followed by colitis examination, barrier permeability analysis, cell proliferation immunostaining assays, and RNA sequencing analysis. By using crypt cultures, the organoid-forming efficiency, cell proliferation, apoptosis, and histone acetylation were analyzed after butyrate and/or tumor necrosis factor α treatments. RESULTS: NCoR1ΔIEC mice showed a dramatic increase in disease severity in this colitis model, with suppression of proliferative cells at the crypt base as an early event and a concomitant increase in barrier permeability. Genome expression patterns showed an important role for NCoR1 in colonic stem cell proliferation and secretory cell differentiation. Colonic organoids cultured from NCoR1ΔIEC mice were more sensitive to butyrate-induced cell growth inhibition and apoptosis, which were exaggerated further by tumor necrosis factor α co-treatment, which was accompanied by increased histone acetylation. CONCLUSIONS: NCoR1 regulates colonic stem cell proliferation and secretory cell differentiation. When NCoR1 is disrupted, barrier protection is weakened, allowing luminal products such as butyrate to penetrate and synergistically damage the colonic crypt cells. Transcript profiling: RNA sequencing data have been deposited in the GEO database, accession number: GSE136153.

Clozapine protects adult neural stem cells from ketamine-induced cell death in correlation with decreased apoptosis and autophagy.

Adult neurogenesis, the production of newborn neurons from neural stem cells (NSCs) has been suggested to be decreased in patients with schizophrenia. A similar finding was observed in an animal model of schizophrenia, as indicated by decreased bromodeoxyuridine (BrdU) labelling cells in response to a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist. The antipsychotic drug clozapine was shown to counteract the observed decrease in BrdU-labelled cells in hippocampal dentate gyrus (DG). However, phenotypic determination by immunohistochemistry analysis could not reveal whether BrdU-positive cells were indeed NSCs. Using a previously established cell model for analysing NSC protection in vitro, we investigated a protective effect of clozapine on NSCs. Primary NSCs were isolated from the mouse subventricular zone (SVZ), we show that clozapine had a NSC protective activity alone, as evident by employing an ATP cell viability assay. In contrast, haloperidol did not show any NSC protective properties. Subsequently, cells were exposed to the non-competitive NMDA-receptor antagonist ketamine. Clozapine, but not haloperidol, had a NSC protective/anti-apoptotic activity against ketamine-induced cytotoxicity. The observed NSC protective activity of clozapine was associated with increased expression of the anti-apoptotic marker Bcl-2, decreased expression of the pro-apoptotic cleaved form of caspase-3 and associated with decreased expression of the autophagosome marker 1A/1B-light chain 3 (LC3-II). Collectively, our findings suggest that clozapine may have a protective/anti-apoptotic effect on NSCs, supporting previous in vivo observations, indicating a neurogenesis-promoting activity for clozapine. If the data are further confirmed in vivo, the results may encourage an expanded use of clozapine to restore impaired neurogenesis in schizophrenia.

Differential effects of glucose deprivation on the survival of fetal versus adult neural stem cells-derived oligodendrocyte precursor cells.

Impaired myelination is a key feature in neonatal hypoxia/ischemia (HI), the most common perinatal/neonatal cause of death and permanent disabilities, which is triggered by the establishment of an inflammatory and hypoxic environment during the most critical period of myelin development. This process is dependent on oligodendrocyte precursor cells (OPCs) and their capability to differentiate into mature oligodendrocytes. In this study, we investigated the vulnerability of fetal and adult OPCs derived from neural stem cells (NSCs) to inflammatory and HI insults. The resulting OPCs/astrocytes cultures were exposed to cytokines to mimic inflammation, or to oxygen-glucose deprivation (OGD) to mimic an HI condition. The differentiation of both fetal and adult OPCs is completely abolished following exposure to inflammatory cytokines, while only fetal-derived OPCs degenerate when exposed to OGD. We then investigated possible mechanisms involved in OGD-mediated toxicity: (a) T3-mediated maturation induction; (b) glutamate excitotoxicity; (c) glucose metabolism. We found that while no substantial differences were observed in T3 intracellular content regulation and glutamate-mediated toxicity, glucose deprivation lead to selective OPC cell death and impaired differentiation in fetal cultures only. These results indicate that the biological response of OPCs to inflammation and demyelination is different in fetal and adult cells, and that the glucose metabolism perturbation in fetal central nervous system (CNS) may significantly contribute to neonatal pathologies. An understanding of the underlying molecular mechanism will contribute greatly to differentiating myelination enhancing and neuroprotective therapies for neonatal and adult CNS white matter lesions.

Progressive Pulmonary Fibrosis Is Caused by Elevated Mechanical Tension on Alveolar Stem Cells.

Fibrosis can develop in most organs and causes organ failure. The most common type of lung fibrosis is known as idiopathic pulmonary fibrosis, in which fibrosis starts at the lung periphery and then progresses toward the lung center, eventually causing respiratory failure. Little is known about the mechanisms underlying the pathogenesis and periphery-to-center progression of the disease. Here we discovered that loss of Cdc42 function in alveolar stem cells (AT2 cells) causes periphery-to-center progressive lung fibrosis. We further show that Cdc42-null AT2 cells in both post-pneumonectomy and untreated aged mice cannot regenerate new alveoli, resulting in sustained exposure of AT2 cells to elevated mechanical tension. We demonstrate that elevated mechanical tension activates a TGF-ß signaling loop in AT2 cells, which drives the periphery-to-center progression of lung fibrosis. Our study establishes a direct mechanistic link between impaired alveolar regeneration, mechanical tension, and progressive lung fibrosis.

Control of Muscle Fibro-Adipogenic Progenitors by Myogenic Lineage is Altered in Aging and Duchenne Muscular Dystrophy.

BACKGROUND/AIMS: Fibro-adipogenic progenitors (FAPs), a muscle-resident stem cell population, have recently emerged as important actors of muscle regeneration by interacting with myogenic progenitors (MPs) to promote the formation of new muscle fibers. However, FAPs are also considered as main contributors of intramuscular fibrotic and fat depositions, resulting in a poor quality of muscles and a defective regeneration in aging and Duchenne Muscular Dystrophy disease (DMD). Therefore, the understanding of the control of FAP fate is an important aspect of muscle repair and homeostasis, but little is known in humans. We wondered the extent to which human FAP proliferation, adipogenesis and fibrogenesis can be regulated by human myogenic progenitors (MPs) in physiological and pathological contexts. METHODS: FAPs and MPs were isolated from skeletal muscles of healthy young or old donors and DMD patients. FAP/MP contact co-cultures and conditioned-media from undifferentiated MPs or differentiated myotubes were assessed on both proliferation and fibro-adipogenic differentiation of FAPs. RESULTS: We showed that soluble molecules released by MPs activate the phosphoinositide 3-kinase (PI3Kinase)/Akt pathway in FAPs, resulting in the stimulation of FAP proliferation. FAP differentiation was regulated by MP-derived myotubes through the secretion of pro-fibrogenic factors and anti-adipogenic factors. Importantly, the regulation of FAP adipogenic and fibrogenic fates by myotubes was found to be mediated by Smad2 phosphorylation and the gene expression of glioma-associated oncogene homolog 1 (GLI1). Surprisingly, the regulations of proliferation and differentiation were disrupted for FAPs and MPs derived from aged individuals and patients with DMD. CONCLUSION: Our results highlight a novel crosstalk between FAPs and the myogenic lineage in humans that could be crucial in the formation of adipocyte and myofibroblast accumulation in dystrophic and aged skeletal muscle.

Niche stiffness underlies the ageing of central nervous system progenitor cells.

Ageing causes a decline in tissue regeneration owing to a loss of function of adult stem cell and progenitor cell populations1. One example is the deterioration of the regenerative capacity of the widespread and abundant population of central nervous system (CNS) multipotent stem cells known as oligodendrocyte progenitor cells (OPCs)2. A relatively overlooked potential source of this loss of function is the stem cell 'niche'-a set of cell-extrinsic cues that include chemical and mechanical signals3,4. Here we show that the OPC microenvironment stiffens with age, and that this mechanical change is sufficient to cause age-related loss of function of OPCs. Using biological and synthetic scaffolds to mimic the stiffness of young brains, we find that isolated aged OPCs cultured on these scaffolds are molecularly and functionally rejuvenated. When we disrupt mechanical signalling, the proliferation and differentiation rates of OPCs are increased. We identify the mechanoresponsive ion channel PIEZO1 as a key mediator of OPC mechanical signalling. Inhibiting PIEZO1 overrides mechanical signals in vivo and allows OPCs to maintain activity in the ageing CNS. We also show that PIEZO1 is important in regulating cell number during CNS development. Thus we show that tissue stiffness is a crucial regulator of ageing in OPCs, and provide insights into how the function of adult stem and progenitor cells changes with age. Our findings could be important not only for the development of regenerative therapies, but also for understanding the ageing process itself.