L-arginine homeostasis governs adult neural stem cell activation by modulating energy metabolism in vivo

cGAMP-targeting injectable hydrogel system promotes periodontal restoration by alleviating cGAS-STING pathway activation

The impaired function of periodontal ligament stem cells (PDLSCs) impedes restoration of periodontal tissues. The cGAS-cGAMP-STING pathway is an innate immune pathway that sensing cytosolic double-stranded DNA (dsDNA), but its role in regulating the function of PDLSCs is still unclear. In this study, we found that mitochondrial DNA (mtDNA) was released into the cytoplasm through the mitochondrial permeability transition pore (mPTP) in PDLSCs upon inflammation, which binds to cGAS and activated the STING pathway by promoting the production of cGAMP, and ultimately impaired the osteogenic differentiation of PDLSCs. Additionally, it is first found that inflammation can down-regulate the level of the ATP-binding cassette membrane subfamily member C1 (ABCC1, a cGAMP exocellular transporter) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1, a cGAMP hydrolase), which further aggravated the accumulation of intracellular cGAMP, leading to the persistent activation of the cGAS-STING pathway and thus the impaired the differentiation capacity of PDLSCs. Furthermore, we designed a hydrogel system loaded with a mPTP blocker, an ABCC1 agonist and ENPP1 to promote periodontal tissue regeneration by modulating the production, exocytosis, and clearance of cGAMP. In conclusion, our results highlight the profound effects, and specific mechanisms, of the cGAS-STING pathway on the function of stem cells and propose a new strategy to promote periodontal tissue restoration based on the reestablishment of cGAMP homeostasis.

Lactate shuttling links histone lactylation to adult hippocampal neurogenesis in mice

Lactate has emerged as a central metabolic fuel and an important signaling molecule. Its availability participates in various brain functions. Although lactate homeostasis is vital for adult hippocampal neurogenesis and cognition, it is still unknown how shuttles lactate across the plasma membrane of neural stem cells (NSCs) to control their activity and neurogenic potential. In this study, we show that monocarboxylate transporter (MCT)1 and MCT2, respectively, control efflux and influx of lactate in the murine NSCs, thereby maintaining intracellular lactate homeostasis. Mechanistically, lactate shuttling links histone lactylation to govern NSC proliferation through MDM2-p53 signaling pathway. Notably, genetic ablation of MCT2 from NSCs or pharmacological inhibition of MDM2-P53 interaction prevents voluntary running-induced NSC proliferation in the murine adult hippocampus. Taken together, our findings demonstrate that lactate shuttling controls histone lactylation, which acts as a nexus for controlling adult hippocampal neurogenesis.

Dysregulation of astrocyte-derived matrix gla protein impairs dendritic spine development in pyridoxine-dependent epilepsy

In spite of adequate seizure control, approximately 75% of pyridoxine-dependent epilepsy (PDE) patients with ALDH7A1 mutation still suffer from intellectual disability. However, the mechanisms underlying brain dysfunction in PDE patients are still unknown even when seizure control is achieved. In this study, we show that mice with specific deletion of Aldh7a1 from astrocytes, but not neurons, exhibit PDE, and have defective dendritic spine development and cognitive impairment when seizure occurrence is well controlled. Mechanistically, ALDH7A1 deficiency leads to dysregulation of astrocyte-derived matrix gla protein (MGP), one of the vitamin K-dependent proteins, thereby impairing dendritic spine development and synaptic transmission. Notably, supplementation of menaquinone-7, a form of vitamin K, promotes MGP activation and rescues defective dendritic spine development, abnormal synaptic transmission, and cognitive impairment in Aldh7a1-deficient mice. Therefore, our findings not only unravel the important role of ALDH7A1 in astrocytes contributing to the pathogenesis of PDE, but also provide a potential therapeutic intervention to ameliorate cognitive impairment in PDE beyond pyridoxine treatment.

IRAP Drives Ribosomal Degradation to Refuel Energy for Platelet Activation during Septic Thrombosis

Platelets play crucial roles in multiple pathophysiological processes after energy-dependent activation. It is puzzling how such a small cellular debris has abundant energy supply. In this study, it is shown that insulin-regulated aminopeptidase (IRAP), a type II transmembrane protein, is a key regulator for platelet activation by promoting energy regeneration during septic thrombosis. Through interaction with certain endosome membrane proteins, IRAP can not only promote granule release, but also facilitate lysosomal degradation of theoretically discarded ribosomes in an mTORC1- and S-acylation-dependent manner in activated platelets. Plentiful amino acids obtained from IRAP-mediated ribophagy are recruited to aerobic glycolysis and then promote energy metabolism reprogramming, thereby producing abundant energy for platelet life extension and prolonged activation. Consequently, targeted blocking IRAP can dramatically alleviate platelet hyperactivation and septic thrombosis.

The Role of microRNAs in Lidocaine-Induced Spinal Cord Neurotoxicity: An Exploration Based on Bioinformatics Analysis

This study investigated the impact of lidocaine-induced neurotoxicity on microRNA (miRNA) expression in the spinal cord of rats. Sprague-Dawley rats underwent intrathecal catheterization and were randomly assigned to receive either 10% lidocaine or normal saline for three consecutive days. Post-treatment, the paw withdrawal threshold significantly increased, accompanied by notable histopathological changes. Additionally, 470 miRNAs exhibited altered expression following lidocaine treatment, with miR-155-5p, miR-3544, and miR-675-5p showing significant changes. Gene Ontology analysis identified cellular metabolic processes as the most significantly enriched functions. Kyoto encyclopedia of genes and genomes pathway analysis revealed that the enriched signaling pathways are associated with neural injury and neuroprotection, and are involved in regulating cellular metabolism. The Mitogen-Activated Protein Kinase (MAPK) signaling pathway was notably enriched, with Mitogen-activated protein kinase kinase kinase 10 (Map3k10) and Mitogen-activated protein kinase kinase kinase 14 (Map3k14) identified as target genes of miR-155-5p. Following lidocaine treatment, there was an observed increase in the expression of MAP3K10 and MAP3K14 at both the mRNA and protein levels. These results indicate that miR-155-5p, miR-3544, and miR-675-5p might be significantly involved in lidocaine-induced neurotoxicity by influencing cellular metabolism. Furthermore, miR-155-5p/MAPK shows potential therapeutic value for treating lidocaine-induced neurotoxicity.

Neural stem cell heterogeneity in adult hippocampus

Adult neurogenesis is a unique cellular process of the ongoing generation of new neurons throughout life, which primarily occurs in the subgranular zone (SGZ) of the dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricle. In the adult DG, newly generated granule cells from neural stem cells (NSCs) integrate into existing neural circuits, significantly contributing to cognitive functions, particularly learning and memory. Recently, more and more studies have shown that rather than being a homogeneous population of identical cells, adult NSCs are composed of multiple subpopulations that differ in their morphology and function. In this study, we provide an overview of the origin, regional characteristics, prototypical morphology, and molecular factors that contribute to NSC heterogeneity. In particular, we discuss the molecular mechanisms underlying the balance between activation and quiescence of NSCs. In summary, this review highlights that deciphering NSC heterogeneity in the adult brain is a challenging but critical step in advancing our understanding of tissue-specific stem cells and the process of neurogenesis in the adult brain.

Multi-omics analysis of synovial tissue and fluid reveals differentially expressed proteins and metabolites in osteoarthritis

BACKGROUND

Knee osteoarthritis is a common degenerative joint disease involving multiple pathological processes, including energy metabolism, cartilage repair, and osteogenesis. To investigate the alterations in critical metabolic pathways and differential proteins in osteoarthritis patients through metabolomic and proteomic analyses and to explore the potential mechanisms underlying synovial osteogenesis during osteoarthritis progression.

METHODS

Metabolomics was used to analyze metabolites in the synovial fluid and synovium of osteoarthritis patients (osteoarthritis group: 10; control group: 10), whereas proteomics was used to examine differential protein expression. Alkaline phosphatase activity was assessed to evaluate osteogenesis.

RESULTS

Upregulation of the tricarboxylic acid cycle: Significant upregulation of the tricarboxylic acid cycle in the synovial fluid and synovium of osteoarthritis patients indicated increased energy metabolism and cartilage repair activity. Arginine metabolism and collagen degradation: Elevated levels of ornithine, proline, and hydroxyproline in the synovial fluid reflect active collagen degradation and metabolism, contributing to joint cartilage breakdown. Abnormal Phenylalanine Metabolism: Increased phenylalanine and tyrosine metabolite levels in osteoarthritis patients suggest their involvement in cartilage destruction and osteoarthritis progression. Synovial osteogenesis: Increased expression of type I collagen in the synovium and elevated alkaline phosphatase activity confirmed the occurrence of osteogenesis, potentially driven by the differentiation of synovial fibroblasts, mesenchymal stem cells, and hypertrophic chondrocytes. Relationships between differential proteins and osteogenesis: FN1 and TGFBI are closely associated with synovial osteogenesis, while the upregulation of energy metabolism pathways provides the energy source for osteogenic transformation.

CONCLUSIONS

Alterations in energy metabolism, cartilage repair, and osteogenic mechanisms are critical. The related metabolites and proteins have potential as diagnostic and therapeutic targets for osteoarthritis.

Dual recombinase-mediated intersectional genetics defines the functional heterogeneity of neural stem cells in adult hippocampus

The Cre-lox site-specific recombinase system is one of the most powerful and versatile technology platforms for studying neural stem cells (NSCs) in adult brain, which is now challenged due to the complex and dynamic nature of in vivo gene expression. In this study, we develop an inducible dual recombinase-mediated intersectional genetics by combining Dre-rox and Cre-lox recombination technologies to specifically target two subpopulations of NSCs (α- and β-NSCs). By visiting their cell lineage and functionality, we find that α- and β-NSCs display distinct self-renewal and differentiation potential, as well as differential responses to external stimuli. Notably, in contrast to α-NSCs, the number of β-NSCs is not affected in aged mice and an APP/PS1 mouse model of Alzeimer's disease. Single cell transcriptome analysis reveals divergent molecular signatures between type α- and β-NSCs and identifies PRMT1 as an important regulatory element to differentially regulate the neurogenic potential of α- and β-NSCs. Inhibition of PRMT1 specifically enhances the neurogenic capacity of β-NSCs and promotes the cognition functions in aged mice. Importantly, PRMT1 inhibition combined with increased BDNF levels pharmacologically ameliorates the cognitive impairments in APP/PS1 mice. Together, our study suggests that understanding the functional heterogeneity of NSCs might pave the way for harnessing the specific subpopulation of NSCs to treat brain disorders.

Neuronal LAMP2A-mediated reduction of adenylyl cyclases induces acute neurodegenerative responses and neuroinflammation after ischemic stroke

Lysosomes regulate cellular metabolism to maintain cell survival, but the mechanisms whereby they determine neuronal cell fate after acute metabolic stress are unknown. Neuron-enriched lysosomal membrane protein LAMP2A is involved in selective chaperone-mediated autophagy and exosome loading. This study demonstrates that abnormalities in the neuronal LAMP2A-lysosomal pathway cause neurological deficits following ischemic stroke and that this is an early inducer of the PANoptosis-like molecular pathway and neuroinflammation, simultaneously inducing upregulation of FADD, RIPK3, and MLKL after ischemia. Quantitative proteomic and pharmacological analysis showed that after acute metabolic stress, the neuronal LAMP2A pathway induced acute synaptic degeneration and PANoptosis-like responses involving downregulation of protein kinase A (PKA) signaling. LAMP2A directed post-stroke lysosomal degradation of adenylyl cyclases (ADCY), including ADCY1 and ADCY3 in cortical neurons. Post-stroke treatment with cAMP mimetic or ADCY activator salvaged cortical neurons from PANoptosis-like responses and neuroinflammation, suggesting that the neuronal ADCY-cAMP-PKA axis is an upstream arrester of the pathophysiological process following an ischemic stroke. This study demonstrates that the neuronal LAMP2A-lysosmal pathway drives intricate acute neurodegenerative and neuroinflammatory responses after brain metabolic stress by downregulating the ADCY-PKA signaling cascade, and highlights the therapeutic potential of PKA signal inducers for improving stroke outcomes.

Flavonoid chrysin activates both TrkB and FGFR1 receptors while upregulates their endogenous ligands such as brain derived neurotrophic factor to promote human neurogenesis

Neurogenesis is the process of generating new neurons from neural stem cells (NSCs) and plays a crucial role in neurological diseases. The process involves a series of steps, including NSC proliferation, migration and differentiation, which are regulated by multiple pathways such as neurotrophic Trk and fibroblast growth factor receptors (FGFR) signalling. Despite the discovery of numerous compounds capable of modulating individual stages of neurogenesis, it remains challenging to identify an agent that can regulate multiple cellular processes of neurogenesis. Here, through screening of bioactive compounds in dietary functional foods, we identified a flavonoid chrysin that not only enhanced the human NSCs proliferation but also facilitated neuronal differentiation and neurite outgrowth. Further mechanistic study revealed the effect of chrysin was attenuated by inhibition of neurotrophic tropomyosin receptor kinase-B (TrkB) receptor. Consistently, chrysin activated TrkB and downstream ERK1/2 and AKT. Intriguingly, we found that the effect of chrysin was also reduced by FGFR1 blockade. Moreover, extended treatment of chrysin enhanced levels of brain-derived neurotrophic factor, as well as FGF1 and FGF8. Finally, chrysin was found to promote neurogenesis in human cerebral organoids by increasing the organoid expansion and folding, which was also mediated by TrkB and FGFR1 signalling. To conclude, our study indicates that activating both TrkB and FGFR1 signalling could be a promising avenue for therapeutic interventions in neurological diseases, and chrysin appears to be a potential candidate for the development of such treatments.

Regulation of adult neurogenesis: the crucial role of astrocytic mitochondria

Neurogenesis has emerged as a promising therapeutic approach for central nervous system disorders. The role of neuronal mitochondria in neurogenesis is well-studied, however, recent evidence underscores the critical role of astrocytic mitochondrial function in regulating neurogenesis and the underlying mechanisms remain incompletely understood. This review highlights the regulatory effects of astrocyte mitochondria on neurogenesis, focusing on metabolic support, calcium homeostasis, and the secretion of neurotrophic factors. The effect of astrocytic mitochondrial dysfunction in the pathophysiology and treatment strategies of Alzheimer's disease and depression is discussed. Greater attention is needed to investigate the mitochondrial autophagy, dynamics, biogenesis, and energy metabolism in neurogenesis. Targeting astrocyte mitochondria presents a potential therapeutic strategy for enhancing neural regeneration.

Inhalation Anesthetics Play a Janus-Faced Role in Self-Renewal and Differentiation of Stem Cells

Inhalation anesthesia stands as a pivotal modality within clinical anesthesia practices. Beyond its primary anesthetic effects, inhaled anesthetics have non-anesthetic effects, exerting bidirectional influences on the physiological state of the body and disease progression. These effects encompass impaired cognitive function, inhibition of embryonic development, influence on tumor progression, and so forth. For many years, inhaled anesthetics were viewed as inhibitors of stem cell fate regulation. However, there is now a growing appreciation that inhaled anesthetics promote stem cell biological functions and thus are now regarded as a double-edged sword affecting stem cell fate. In this review, the effects of inhaled anesthetics on self-renewal and differentiation of neural stem cells (NSCs), embryonic stem cells (ESCs), and cancer stem cells (CSCs) were summarized. The mechanisms of inhaled anesthetics involving cell cycle, metabolism, stemness, and niche of stem cells were also discussed. A comprehensive understanding of these effects will enhance our comprehension of how inhaled anesthetics impact the human body, thus promising breakthroughs in the development of novel strategies for innovative stem cell therapy approaches.

Mitochondrial regulation of adult hippocampal neurogenesis: Insights into neurological function and neurodevelopmental disorders

Mitochondria are essential regulators of cellular energy metabolism and play a crucial role in the maintenance and function of neuronal cells. Studies in the last decade have highlighted the importance of mitochondrial dynamics and bioenergetics in adult neurogenesis, a process that significantly influences cognitive function and brain plasticity. In this review, we examine the mechanisms by which mitochondria regulate adult neurogenesis, focusing on the impact of mitochondrial function on the behavior of neural stem/progenitor cells and the maturation and plasticity of newborn neurons in the adult mouse hippocampus. In addition, we explore the link between mitochondrial dysfunction, adult hippocampal neurogenesis and genes associated with cognitive deficits in neurodevelopmental disorders. In particular, we provide insights into how alterations in the transcriptional regulator NR2F1 affect mitochondrial dynamics and may contribute to the pathophysiology of the emerging neurodevelopmental disorder Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS). Understanding how genes involved in embryonic and adult neurogenesis affect mitochondrial function in neurological diseases might open new directions for therapeutic interventions aimed at boosting mitochondrial function during postnatal life.

Cellular and Molecular Insights into the Divergence of Neural Stem Cells on Matrigel and Poly-l-lysine Interfaces

Poly-l-lysine (PLL) and Matrigel, both classical coating materials for culture substrates in neural stem cell (NSC) research, present distinct interfaces whose effect on NSC behavior at cellular and molecular levels remains ambiguous. Our investigation reveals intriguing disparities: although both PLL and Matrigel interfaces are hydrophilic and feature amine functional groups, Matrigel stands out with lower stiffness and higher roughness. Based on this diversity, Matrigel surpasses PLL, driving NSC adhesion, migration, and proliferation. Intriguingly, PLL promotes NSC differentiation into astrocytes, whereas Matrigel favors neural differentiation and the physiological maturation of neurons. At the molecular level, Matrigel showcases a wider upregulation of genes linked to NSC behavior. Specifically, it enhances ECM-receptor interaction, activates the YAP transcription factor, and heightens glycerophospholipid metabolism, steering NSC proliferation and neural differentiation. Conversely, PLL upregulates genes associated with glial cell differentiation and amino acid metabolism and elevates various amino acid levels, potentially linked to its support for astrocyte differentiation. These distinct transcriptional and metabolic activities jointly shape the divergent NSC behavior on these substrates. This study significantly advances our understanding of substrate regulation on NSC behavior, offering novel insights into optimizing and targeting the application of these surface coating materials in NSC research.

Disrupted de novo pyrimidine biosynthesis impairs adult hippocampal neurogenesis and cognition in pyridoxine-dependent epilepsy

Despite seizure control by early high-dose pyridoxine (vitamin B6) treatment, at least 75% of pyridoxine-dependent epilepsy (PDE) patients with ALDH7A1 mutation still suffer from intellectual disability. It points to a need for additional therapeutic interventions for PDE beyond pyridoxine treatment, which provokes us to investigate the mechanisms underlying the impairment of brain hemostasis by ALDH7A1 deficiency. In this study, we show that ALDH7A1-deficient mice with seizure control exhibit altered adult hippocampal neurogenesis and impaired cognitive functions. Mechanistically, ALDH7A1 deficiency leads to the accumulation of toxic lysine catabolism intermediates, α-aminoadipic-δ-semialdehyde and its cyclic form, δ-1-piperideine-6-carboxylate, which in turn impair de novo pyrimidine biosynthesis and inhibit NSC proliferation and differentiation. Notably, supplementation of pyrimidines rescues abnormal neurogenesis and cognitive impairment in ALDH7A1-deficient adult mice. Therefore, our findings not only define the important role of ALDH7A1 in the regulation of adult hippocampal neurogenesis but also provide a potential therapeutic intervention to ameliorate the defective mental capacities in PDE patients with seizure control.

Adult neurogenesis research in China

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Molecular mechanisms of cellular metabolic homeostasis in stem cells

Many tissues and organ systems have intrinsic regeneration capabilities that are largely driven and maintained by tissue-resident stem cell populations. In recent years, growing evidence has demonstrated that cellular metabolic homeostasis plays a central role in mediating stem cell fate, tissue regeneration, and homeostasis. Thus, a thorough understanding of the mechanisms that regulate metabolic homeostasis in stem cells may contribute to our knowledge on how tissue homeostasis is maintained and provide novel insights for disease management. In this review, we summarize the known relationship between the regulation of metabolic homeostasis and molecular pathways in stem cells. We also discuss potential targets of metabolic homeostasis in disease therapy and describe the current limitations and future directions in the development of these novel therapeutic targets.

Energy metabolic pathways in neuronal development and function

Neuronal development and function are known to be among the most energy-demanding functions of the body. Constant energetic support is therefore crucial at all stages of a neuron's life. The two main adenosine triphosphate (ATP)-producing pathways in cells are glycolysis and oxidative phosphorylation. Glycolysis has a relatively low yield but provides fast ATP and enables the metabolic versatility needed in dividing neuronal stem cells. Oxidative phosphorylation, on the other hand, is highly efficient and therefore thought to provide most or all ATP in differentiated neurons. However, it has recently become clear that due to their distinct properties, both pathways are required to fully satisfy neuronal energy demands during development and function. Here, we provide an overview of how glycolysis and oxidative phosphorylation are used in neurons during development and function.