Metabolic plasticity in stem cell homeostasis and differentiation

Metabolic landscape and rewiring in normal hematopoiesis, leukemia and aging

Recent advancements in metabolism research have demonstrated its critical roles in a lot of critical biological processes, including stemness maintenance, cell differentiation, proliferation, and function. Hematopoiesis is the fundamental cell differentiation process with the production of millions of red blood cells per second in carrying oxygen and white blood cells in fighting infection and cancers. The differentiation processes of hematopoietic stem and progenitor cells (HSPCs) are accompanied by significant metabolic reprogramming. In hematological malignancy, metabolic reprogramming is also essential to the malignant hematopoiesis processes. The metabolic rewiring is driven by distinct molecular mechanisms that meet the specific demands of different target cells. Leukemic cells, for instance, adopt unique metabolic profiles to support their heightened energy needs for survival and proliferation. Moreover, aging HSPCs exhibit altered energy consumption compared to their younger counterparts, often triggering protective mechanisms at the cellular level. In this review, we provide a comprehensive analysis of the metabolic processes involved in hematopoiesis and the metabolic rewiring that occurs under adverse conditions. In addition, we highlight current research directions and discuss the potential of targeting metabolic pathways for the management of hematological malignancies and aging.

Cellular senescence in age-related musculoskeletal diseases

Aging is typically associated with decreased musculoskeletal function, leading to reduced mobility and increased frailty. As a hallmark of aging, cellular senescence plays a crucial role in various age-related musculoskeletal diseases, including osteoporosis, osteoarthritis, intervertebral disc degeneration, and sarcopenia. The detrimental effects of senescence are primarily due to impaired regenerative capacity of stem cells and the pro-inflammatory environment created by accumulated senescent cells. The secreted senescence-associated secretory phenotype (SASP) can induce senescence in neighboring cells, further amplifying senescent signals. Although the removal of senescent cells and the suppression of SASP factors have shown promise in alleviating disease progression and restoring musculoskeletal health in mouse models, clinical trials have yet to demonstrate significant efficacy. This review summarizes the mechanisms of cellular senescence in age-related musculoskeletal diseases and discusses potential therapeutic strategies targeting cellular senescence.

Mitochondrial fatty acid oxidation regulates adult muscle stem cell function through modulating metabolic flux and protein acetylation

During homeostasis and regeneration, satellite cells, the resident stem cells of skeletal muscle, have distinct metabolic requirements for fate transitions between quiescence, proliferation and differentiation. However, the contribution of distinct energy sources to satellite cell metabolism and function remains largely unexplored. Here, we uncover a role of mitochondrial fatty acid oxidation (FAO) in satellite cell integrity and function. Single-cell RNA sequencing revealed progressive enrichment of mitochondrial FAO and downstream pathways during activation, proliferation and myogenic commitment of satellite cells. Deletion of Carnitine palmitoyltransferase 2 (Cpt2), the rate-limiting enzyme in FAO, hampered muscle stem cell expansion and differentiation upon acute muscle injury, markedly delaying regeneration. Cpt2 deficiency reduces acetyl-CoA levels in satellite cells, impeding the metabolic flux and acetylation of selective proteins including Pax7, the central transcriptional regulator of satellite cells. Notably, acetate supplementation restored cellular metabolic flux and partially rescued the regenerative defects of Cpt2-null satellite cells. These findings highlight an essential role of fatty acid oxidation in controlling satellite cell function and suggest an integration of lipid metabolism and protein acetylation in adult stem cells.

A Cross-Linked Cyclosiloxane Polymer Matrix as a Platform Enabling Long-Term Culture of Human Induced Pluripotent Stem Cells with Naïve-Like Features

Culture platforms for human induced pluripotent stem cells (hiPSCs) that rely on feeder cells or extracellular matrices (ECMs) face substantial limitations for practical regenerative medicine applications, including undefined components, high costs, and a tendency to maintain hiPSCs in the primed pluripotent state, which has lower differentiation potential than the naïve state. To overcome these challenges, we developed a long-term hiPSC culture platform based on a cross-linked cyclosiloxane polymer matrix that preserves pluripotency with naïve-like characteristics. Through optimization, we identified an ideal cyclosiloxane polymer matrix, designated as poly-Z, which supported the growth of hiPSCs as spheroids. Even after 60 d of continuous culture, hiPSC spheroids maintained on poly-Z retained pluripotency markers and normal karyotypes at levels comparable to those of hiPSC colonies cultured on conventional vitronectin (VN)-coated plates. Furthermore, mRNA sequencing revealed that hiPSC spheroids cultured on poly-Z not only exhibited up-regulation of typical pluripotency-related genes but also showed increased expression of genes associated with the naïve pluripotent state, in contrast to the primed state observed in hiPSCs cultured on VN-coated plates or in suspension culture. Gene ontology (GO) analysis and gene set enrichment analysis (GSEA) further suggested that the down-regulation of genes involved in cell-ECM interactions contributed to the induction of naïve-like features in poly-Z-cultured hiPSC spheroids. These findings highlight the potential of cross-linked cyclosiloxane-based polymer matrices as an innovative platform for human pluripotent stem cell research and regenerative medicine.

The protective role of GPX4 in naïve ESCs is highlighted by induced ferroptosis resistance through GPX4 expression

Ferroptosis, a form of oxidative cell death mediated by lipid peroxidation, is strictly regulated by glutathione peroxidase 4 (GPX4). Knockout of Gpx4 results in embryonic lethality, highlighting its essential role in development. In vitro, mouse embryonic stem cells (mESCs), which represent the naïve pluripotent state, require β-mercaptoethanol (bME) to prevent cell death, unlike human embryonic stem cells, which represent the primed state. We hypothesized that naïve pluripotency is linked to a heightened susceptibility to ferroptosis due to unique metabolic demands and redox imbalances. In this study, we found that bME deprivation induces ferroptosis in naïve ESCs, as evidenced by lipid peroxidation; ferroptosis, however, is less evident in primed ESCs. Mechanistic analyses revealed that active oxidative phosphorylation (OXPHOS) in naïve ESCs increased mitochondrial reactive oxygen species. Consistent with the upregulation of Gpx4 transcripts and OXPHOS-associated gene sets seen in the inner cell mass of blastocysts, stable GPX4 expression conferred resistance to ferroptosis induced by bME withdrawal. These results suggest that the unique redox and metabolic landscape of naïve ESCs highlits a potential requirement for GPX4 in maintaining naïve pluripotency, providing insights into early developmental processes and vulnerabilities.

Mitochondrial damage-associated molecular patterns: New perspectives for mitochondria and inflammatory bowel diseases

Mitochondria are key regulators of inflammatory responses and mitochondrial dysfunction is closely linked to various inflammatory diseases. Increasing genetic and experimental evidence suggests that mitochondria play a critical role in inflammatory bowel disease (IBD). In the complex environment of the intestinal tract, intestinal epithelial cells (IECs) and their mitochondria possess unique phenotypic features, shaping each other and regulating intestinal homeostasis and inflammation through diverse mechanisms. Here, we focus on intestinal inflammation in IBD induced by mitochondrial damage-associated molecular patterns (mtDAMPs), which comprise mitochondrial components and metabolic products. The pathogenic mechanisms of mtDAMP signaling pathways mediated by two major mtDAMPs, mitochondrial DNA (mtDNA) and mitochondrial reactive oxygen species (mtROS), are discussed.

AMPK activation by glycogen expenditure primes the exit of naïve pluripotency

Embryonic and epiblast stem cells in pre-and post-implantation embryos are characterized by their naïve and primed states, respectively which represent distinct phases of pluripotency. Thus, cellular transition from naïve-to-primed pluripotency recapitulates a drastic metabolic and cellular remodeling after implantation to adapt to changes in extracellular conditions. Here, we found that inhibition of AMPK occurs during naïve transition with two conventional inhibitors of the MEK1 and GSK3β pathways. The accumulation of glycogen due to iGSK3β is responsible for AMPK inhibition, which accounts for high de novo fatty acid synthesis in naïve (ESCs). The knockout of glycogen synthase 1 in naïve ESCs; GKO, resulting in a drastic glycogen loss, leads to a robust AMPK activation and lowers the level of fatty acids. GKO loses cellular characteristics of naïve ESCs and rapidly transitioned to a primed state. The characteristics of GKO are restored by the simultaneous AMPK KO. These findings suggest that high glycogen in epiblast within pre-implantation blastocyst may act as a signaling molecule for timely activation of AMPK, thus ultimately contributing to transition to post-implantation stage epiblast.

The role of different physical exercises as an anti-aging factor in different stem cells

The senescence process is connected to the characteristics of cellular aging. Understanding their causal network helps develop a framework for creating new treatments to slow down the senescence process. A growing body of research indicates that aging may adversely affect stem cells (SCs). SCs change their capability to differentiate into different cell types and decrease their potential for renewal as they age. Research has indicated that consistent physical exercise offers several health advantages, including a reduced risk of age-associated ailments like tumors, heart disease, diabetes, and neurological disorders. Exercise is a potent physiological stressor linked to higher red blood cell counts and an enhanced immune system, promoting disease resistance. Sports impact mesenchymal SCs (MSCs), hematopoietic SCs (HSCs), neuronal SCs (NuSCs), and muscular SCs (MuSCs), among other aged SCs types. These changes to the niche will probably affect the amount and capability of adult SCs after exercise. In this work, we looked into how different types of SCs age. The impact of physical activity on the aging process has been studied. Additionally, there has been discussion and study on the impact of different sports and physical activities on SCs as an anti-aging component.

Role of Mitochondrial Dynamics in Skin Homeostasis: An Update

Skin aging is the most prominent phenotype of host aging and is the consequence of a combination of genes and environment. Improving skin aging is essential for maintaining the healthy physiological function of the skin and the mental health of the human body. Mitochondria are vital organelles that play important roles in cellular mechanisms, including energy production and free radical balance. However, mitochondrial metabolism, mitochondrial dynamics, biogenesis, and degradation processes vary greatly in various cells in the skin. It is well known that mitochondrial dysfunction can promote the aging and its associated diseases of the skin, resulting in the damage of skin physiology and the occurrence of skin pathology. In this review, we summarize the important role of mitochondria in various skin cells, review the cellular responses to vital steps in mitochondrial quality regulation, mitochondrial dynamics, mitochondrial biogenesis, and mitochondrial phagocytosis, and describe their importance and specific pathways in skin aging.

Super-enhancer Activates Master Transcription Factor NR3C1 Expression and Promotes 5-FU Resistance in Gastric Cancer

Poor response to 5-fluorouracil (5-FU) remains an obstacle in the treatment of gastric cancer (GC). Super enhancers (SEs) are crucial for determining tumor cell survival under drug pressure. SE landscapes related to 5-FU-resistance are mapped to GC using chromatin immunoprecipitation-sequencing (ChIP-Seq). SiRNA transcription factors (TFs) screen determines master TF Nuclear Receptor Subfamily 3 Group C Member 1 (NR3C1) activated by SE. High NR3C1 expression driven by SE correlated with 5-FU resistance in patient-derived organoids (PDOs). Phase separation formed by NR3C1 is observed using fluorescence recovery after photobleaching (FRAP). NR3C1 protein and Mediator promoted SE-related gene transcription via phase separation. SEs and NR3C1 co-binding patterns are explored using Cleavage Under Targets and Tagmentation (CUT&Tag) sequencing. 5-FU-related genes driven by NR3C1 are identified using epigenetic reader inhibitor JQ1 and NR3C1 specific inhibitor Cort108297. NR3C1 knockdown increases 5-FU sensitivity and alters the SE landscape through enhancer reprogramming, reducing downstream 5-FU-related target genes. JQ1 and Cort108297 both improve 5-FU efficacy in PDOs and patient-derived xenografts (PDXs) by destroying SEs or inhibiting NR3C1. In conclusion, SE-driven NR3C1 promotes 5-FU resistance in GC. SE destruction and NR3C1 inhibition lead to enhancer reconstruction and reduce 5-FU-related gene transcription, providing alternative therapeutic strategies for improving 5-FU sensitivity.

Hematopoietic stem cell metabolism within the bone marrow niche - insights and opportunities

Hematopoiesis unfolds within the bone marrow niche where hematopoietic stem cells (HSCs) play a central role in continually replenishing blood cells. The hypoxic bone marrow environment imparts peculiar metabolic characteristics to hematopoietic processes. Here, we discuss the internal metabolism of HSCs and describe external influences exerted on HSC metabolism by the bone marrow niche environment. Importantly, we suggest that the metabolic environment and metabolic cues are intertwined with HSC cell fate, and are crucial for hematopoietic processes. Metabolic dysregulation within the bone marrow niche during acute stress, inflammation, and chronic inflammatory conditions can lead to reduced HSC vitality. Additionally, we raise questions regarding metabolic stresses imposed on HSCs during implementation of stem cell protocols such as allo-SCT and gene therapy, and the potential ramifications. Enhancing our comprehension of metabolic influences on HSCs will expand our understanding of pathophysiology in the bone marrow and improve the application of stem cell therapies.

MTCH2 controls energy demand and expenditure to fuel anabolism during adipogenesis

Mitochondrial carrier homolog 2 (MTCH2) is a regulator of apoptosis, mitochondrial dynamics, and metabolism. Loss of MTCH2 results in mitochondrial fragmentation, an increase in whole-body energy utilization, and protection against diet-induced obesity. In this study, we used temporal metabolomics on HeLa cells to show that MTCH2 deletion results in a high ATP demand, an oxidized cellular environment, and elevated utilization of lipids, amino acids, and carbohydrates, accompanied by a decrease in several metabolites. Lipidomics analysis revealed a strategic adaptive reduction in membrane lipids and an increase in storage lipids in MTCH2 knockout cells. Importantly, MTCH2 knockout cells showed an increase in mitochondrial oxidative function, which may explain the higher energy demand. Interestingly, this imbalance in energy metabolism and reductive potential triggered by MTCH2-deletion prevents NIH3T3L1 preadipocytes from differentiating into mature adipocytes, an energy consuming reductive biosynthetic process. In summary, the loss of MTCH2 leads to increased mitochondrial oxidative activity and energy demand, creating a catabolic and oxidative environment that fails to fuel the anabolic processes required for lipid accumulation and adipocyte differentiation.

Bone Marrow Niche in Cardiometabolic Disease: Mechanisms and Therapeutic Potential

Cardiovascular and cardiometabolic diseases are leading causes of morbidity and mortality worldwide, driven in part by chronic inflammation. Emerging research suggests that the bone marrow microenvironment, or marrow niche, plays a critical role in both immune system regulation and disease progression. The bone marrow niche is essential for maintaining hematopoietic stem cells (HSCs) and orchestrating hematopoiesis. Under normal conditions, this niche ensures a return to immune homeostasis after acute stress. However, in the setting of inflammatory conditions such as those seen in cardiometabolic diseases, it becomes dysregulated, leading to enhanced myelopoiesis and immune activation. This review explores the reciprocal relationship between the bone marrow niche and cardiometabolic diseases, highlighting how alterations in the niche contribute to disease development and progression. The niche regulates HSCs through complex interactions with stromal cells, endothelial cells, and signaling molecules. However, in the setting of chronic diseases such as hypertension, atherosclerosis, and diabetes, inflammatory signals disrupt the balance between HSC self-renewal and differentiation, promoting the excessive production of proinflammatory myeloid cells that exacerbate the disease. Key mechanisms discussed include the effects of hyperlipidemia, hyperglycemia, and sympathetic nervous system activation on HSC proliferation and differentiation. Furthermore, the review emphasizes the role of epigenetic modifications and metabolic reprogramming in creating trained immunity, a phenomenon whereby HSCs acquire long-term proinflammatory characteristics that sustain disease states. Finally, we explore therapeutic strategies aimed at targeting the bone marrow niche to mitigate chronic inflammation and its sequelae. Novel interventions that modulate hematopoiesis and restore niche homeostasis hold promise for the treatment of cardiometabolic diseases. By interrupting the vicious cycle of inflammation and marrow dysregulation, such therapies may offer new avenues for reducing cardiovascular risk and improving patient outcomes.

MetaboLINK is a novel algorithm for unveiling cell-specific metabolic pathways in longitudinal datasets

Introduction

In the rapidly advancing field of 'omics research, there is an increasing demand for sophisticated bioinformatic tools to enable efficient and consistent data analysis. As biological datasets, particularly metabolomics, become larger and more complex, innovative strategies are essential for deciphering the intricate molecular and cellular networks.

Methods

We introduce a pioneering analytical approach that combines Principal Component Analysis (PCA) with Graphical Lasso (GLASSO). This method is designed to reduce the dimensionality of large datasets while preserving significant variance. For the first time, we applied the PCA-GLASSO algorithm (i.e., MetaboLINK) to metabolomics data derived from Nuclear Magnetic Resonance (NMR) spectroscopy performed on neural cells at various developmental stages, from human embryonic stem cells to neurons.

Results

The MetaboLINK analysis of longitudinal metabolomics data has revealed distinct pathways related to amino acids, lipids, and energy metabolism, uniquely associated with specific cell progenies. These findings suggest that different metabolic pathways play a critical role at different stages of cellular development, each contributing to diverse cellular functions.

Discussion

Our study demonstrates the efficacy of the MetaboLINK approach in analyzing NMR-based longitudinal metabolomic datasets, highlighting key metabolic shifts during cellular transitions. We share the methodology and the code to advance general 'omics research, providing a powerful tool for dissecting large datasets in neurobiology and other fields.

Single-Cell RNA sequencing reveals mitochondrial dysfunction in microtia chondrocytes

Microtia is a congenital malformation characterized by underdevelopment of the external ear. While chondrocyte dysfunction has been implicated in microtia, the specific cellular abnormalities remain poorly understood. This study aimed to investigate mitochondrial dysfunction in microtia chondrocytes using single-cell RNA sequencing. Cartilage samples were obtained from patients with unilateral, non-syndromic microtia and healthy controls. Single-cell RNA sequencing was performed using the 10 × Genomics platform. Bioinformatic analyses including cell type identification, trajectory analysis, and gene co-expression network analysis were conducted. Mitochondrial function was assessed through ROS levels, membrane potential, and transmission electron microscopy. Chondrocytes from microtia samples showed lower mitochondrial function scores compared to normal samples. Trajectory analysis revealed more disorganized differentiation patterns in microtia chondrocytes. Mitochondrial dysfunction in microtia chondrocytes was confirmed by increased ROS production, decreased membrane potential, and altered mitochondrial structure. Gene co-expression network analysis identified hub genes associated with mitochondrial function, including SDHA, SIRT1, and PGC1A, which showed reduced expression in microtia chondrocytes. This study provides evidence of mitochondrial dysfunction in microtia chondrocytes and identifies potential key genes involved in this process. These findings offer new insights into the pathogenesis of microtia and may guide future therapeutic strategies.

The impact of endocrine-disrupting chemicals on stem cells: Mechanisms and implications for human health

Endocrine-disrupting chemicals (EDCs) are compounds, either natural or man-made, that interfere with the normal functioning of the endocrine system. There is increasing evidence that exposure to EDCs can have profound adverse effects on reproduction, metabolic disorders, neurological alterations, and increased risk of hormone-dependent cancer. Stem cells (SCs) are integral to these pathological processes, and it is therefore crucial to understand how EDCs may influence SC functionality. This review examines the literature on different types of EDCs and their effects on various types of SCs, including embryonic, adult, and cancer SCs. Possible molecular mechanisms through which EDCs may influence the phenotype of SCs are also evaluated. Finally, the possible implications of these effects on human health are discussed. The available literature demonstrates that EDCs can influence the biology of SCs in a variety of ways, including by altering hormonal pathways, DNA damage, epigenetic changes, reactive oxygen species production and alterations in the gene expression patterns. These disruptions may lead to a variety of cell fates and diseases later in adulthood including increased risk of endocrine disorders, obesity, infertility, reproductive abnormalities, and cancer. Therefore, the review emphasizes the importance of raising broader awareness regarding the intricate impact of EDCs on human health.

The Dlk1-Dio3 noncoding RNA cluster coordinately regulates mitochondrial respiration and chromatin structure to establish proper cell state for muscle differentiation

The coordinate regulation of metabolism and epigenetics to establish cell state-specific gene expression patterns during lineage progression is a central aspect of cell differentiation, but the factors that regulate this elaborate interplay are not well-defined. The imprinted Dlk1-Dio3 noncoding RNA (ncRNA) cluster has been associated with metabolism in various progenitor cells, suggesting it functions as a regulator of metabolism and cell state. Here, we directly demonstrate that the Dlk1-Dio3 ncRNA cluster coordinates mitochondrial respiration and chromatin structure to maintain proper cell state. Stable mouse muscle cell lines were generated harboring two distinct deletions in the proximal promoter region, resulting in either greatly upregulated or downregulated expression of the entire Dlk1-Dio3 ncRNA cluster. Both mutant lines displayed impaired muscle differentiation along with dysregulated structural gene expression and abnormalities in mitochondrial respiration. Genome-wide chromatin accessibility and histone methylation patterns were also severely affected in these mutants. Our results strongly suggest that muscle cells are sensitive to Dlk1-Dio3 ncRNA dosage, and that the cluster coordinately regulates metabolic activity and the epigenome to maintain proper cell state in the myogenic lineage.

Acupuncture and Moxibustion for Inflammatory Bowel Disease: Regulatory Mechanisms Revealed by Microbiome and Metabolomic Analysis

Acupuncture and moxibustion are widely acknowledged as effective complementary therapies for managing inflammatory bowel disease (IBD) in traditional Chinese medicine. However, the regulatory mechanisms by which these two therapies exert their therapeutic effects in IBD are yet to be fully elucidated. The objective of this study was to investigate the mechanisms of action underlying acupuncture and moxibustion and the regulative differences between them as therapeutic interventions for IBD. Using a dextran sodium sulfate-induced IBD mice model, the effects of the two treatments were evaluated by examination of body weight, stool samples, colon morphology, inflammatory factors, gut microbiota, and metabolites. The results indicated that both acupuncture and moxibustion mitigated body weight reduction; improved the structural characteristics of intestinal tissues; increased levels of anti-inflammatory cytokines including interleukin (IL)-10; and decreased levels of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-[Formula: see text]), nuclear factor kappa B (NF-[Formula: see text]B), IL-6, IL-1[Formula: see text], and IL-17. Acupuncture and moxibustion had distinct effects on the regulation of the intestinal microbiota and metabolic pathways in IBD mice. Moxibustion regulated a greater number of metabolic pathways than acupuncture, the majority of which were associated with amino acid metabolism, brain signal transmission, energy metabolism, and anti-inflammatory pathways. These findings provide a scientific basis for the differential applications of acupuncture and moxibustion in clinical practice.

TET3 regulates terminal cell differentiation at the metabolic level

TET-family members play a critical role in cell fate commitment. Indeed, TET3 is essential to postnatal development due to yet unknown reasons. To define TET3 function in cell differentiation, we have profiled the intestinal epithelium at single-cell level from wild-type and Tet3 knockout mice. We have found that Tet3 is mostly expressed in differentiated enterocytes. In the absence of TET3, enterocytes exhibit an aberrant differentiation trajectory and do not acquire a physiological cell identity due to an impairment in oxidative phosphorylation, specifically due to an ATP synthase assembly deficiency. Moreover, spatial metabolomics analysis has revealed that Tet3 knockout enterocytes exhibit an unphysiological metabolic profile when compared with their wild-type counterparts. In contrast, no metabolic differences have been observed between both genotypes in the stem cell compartment where Tet3 is mainly not expressed. Collectively, our findings suggest a mechanism by which TET3 regulates mitochondrial function and, thus, terminal cell differentiation at the metabolic level.

EZH2 inhibition sensitizes retinoic acid-driven senescence in synovial sarcoma

Synovial sarcoma (SS) is driven by a unique t(18;X) chromosomal translocation resulting in expression of the SS18-SSX fusion oncoprotein, a transcriptional regulator with both activating and repressing functions. However, the manner in which SS18-SSX contributes to the development of SS is not entirely known. Here, we show that SS18-SSX drives the expression of Preferentially Expressed Antigen in Melanoma (PRAME), which is highly expressed in SS but whose function remains poorly understood. The fusion protein directly binds and activates the PRAME promoter and we found that expression of SS18-SSX and PRAME are positively correlated. We provide evidence that PRAME modulates retinoic acid (RA) signaling, forming a ternary complex with the RA receptor α (RARα) and the Enhancer of Zeste Homolog 2 (EZH2). Knockdown of PRAME suppressed the response to all-trans retinoic acid (ATRA) supporting PRAME's role in modulating RA-signaling. Notably, we demonstrate that combined pharmacological inhibition of EZH2 and treatment with ATRA reconstituted RA signaling followed by reduced proliferation and induction of cellular senescence. In conclusion, our data provides new insights on the role of the SS18-SSX fusion protein in regulation of PRAME expression and RA signaling, highlighting the therapeutic potential of disrupting the RARα-PRAME-EZH2 complex in SS. Schematic presentation of the proposed model. A The RARα-PRAME-EZH2 ternary complex in SS. The fusion SS18-SSX oncoprotein binds to the PRAME promoter and activates its expression. PRAME in turn interacts with RARα-RXR heterodimers as well as with EZH2, and the complex binds to retinoic acid response elements (RAREs) in the DNA. This results in transcriptional repression of retinoic acid (RA) responsive genes and thus inhibition of RA-signaling, allowing tumor cell proliferation. B Therapeutic strategy. Treatment with an EZH2 inhibitor, such as GSK343, or activation of RAR receptors via all-trans retinoic acid (ATRA), disrupts the RARα-PRAME-EZH2 ternary complex and restores RA-signaling. Exposure to GSK343 or ATRA results in inhibition of cell proliferation and induction of cellular senescence, where GSK343 shows a dominant effect. The Figure was created with Biorender.com.

Renovascular Disease and Mitochondrial Dysfunction in Human Mesenchymal Stem Cells

Key Points

Renovascular disease impairs the capacity of human adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic murine kidneys. miR-378h modulated the capacity of renovascular disease adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic kidneys in vivo .

Background

Renovascular disease leads to renal ischemia, hypertension, and eventual kidney failure. Autologous transplantation of adipose tissue–derived mesenchymal stem/stromal cells (MSCs) improves perfusion and oxygenation in stenotic human kidneys, but associated atherosclerosis and hypertension might blunt their effectiveness. We hypothesized that renovascular disease alters the human MSC transcriptome and impairs their reparative potency.

Methods

MSCs were harvested from subcutaneous abdominal fat of patients with renovascular disease and healthy volunteers (n =3 each), characterized and subsequently injected (5×105/200 μ l) into mice 2 weeks after renal artery stenosis or sham surgery (n =6/group). Two weeks later, mice underwent imaging and tissue studies. MSCs from healthy volunteers and in those with renovascular disease were also characterized by mRNA/microRNA (miRNA) sequencing. Based on these, MSC proliferation and mitochondrial damage were assessed in vitro before and after miRNA modulation and in vivo in additional renal artery stenosis mice administered with MSCs from renovascular disease pretreated with miR-378h mimic (n =5) or inhibitor (n =4).

Results

MSCs engrafted in stenotic mouse kidneys. Healthy volunteer MSCs (but not renovascular disease MSCs) decreased BP, improved serum creatinine levels and stenotic-kidney cortical perfusion and oxygenation, and attenuated peritubular capillary loss, tubular injury, and fibrosis. Genes upregulated in renovascular disease MSCs versus healthy volunteer MSCs were mostly implicated in transcription and cell proliferation, whereas those downregulated encoded mainly mitochondrial proteins. Upregulated miRNAs, including miR-378h, primarily target nuclear-encoded mitochondrial genes, whereas downregulated miRNAs mainly target genes implicated in transcription and cell proliferation. MSC proliferation was similar, but their mitochondrial structure and reparative function both in vivo and in vitro improved after miR-378h inhibition.

Conclusions

Renovascular disease impaired the reparative capacity of human MSCs, possibly by dysregulating miR-378h that targets mitochondrial genes.

Podcast

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A scoping review regarding reproductive capacity modulation based on alpha-ketoglutarate supplementation

In brief

Alpha-ketoglutarate is a common metabolite in the tricarboxylic acid cycle and is central in modulating the reproductive potential in animal models. The present scoping review systematically covers the spectrum of a wide range of evidence from different viewpoints, focusing on the underlying processes and mechanisms of the developmental framework, aiming to fill the gaps within the existing literature.

Abstract

Alpha-ketoglutarate is an important intermediate molecule in the tricarboxylic acid cycle with a prominent role in distinct biological processes such as cellular energy metabolism, epigenetic regulation, and signaling pathways. We conducted a registered scoping review (OSF: osf.io/b8nyt) to explore the impact of exogenous supplementation on reproductive capabilities. Our strategy included evaluating the main research literature from different databases like PubMed-MEDLINE, Web of ScienceTM, Scopus, and Excerpta Medica dataBASE using a specific systematic layout to encompass all investigations based on experimental models and critically compare the results. Twenty-one studies were included in the main body of this manuscript, which revealed that exogenous supplementation induced dose- and sex-dependent modifications. This metabolite modulates the expression of pluripotency genes, thus controlling stem cells' self-renewal, differentiation, and reprogramming dynamics, while also alleviating structural transformations induced by exposure to heavy metals and other inhibitors. This significantly demonstrated a direct influence of alpha-ketoglutarate in mitigating oxidative stress and prolonging the lifespan, consequently supporting metabolic and endocrine adjustments. It influences oocyte quality and quantity, delays reproductive aging, and establishes an optimal competence framework for development with minimal risk of failure. Therefore, alpha-ketoglutarate is linked to improving reproductive performance, but further studies are needed due to a lack of studies on humans.

[Muscle stem cells and metabolism in Duchenne muscular dystrophy, focus on AMPK]

Through their myogenic activity, adult muscle stem cells (MuSCs) are crucial for the regeneration of striated skeletal muscle. Once activated, they proliferate, differentiate and then fuse to repair or form new muscle fibers (myofibers). Their progression through myogenesis requires a complex regulation involving multiple players such as metabolism, in particular via AMPK. This protein kinase regulates the self-renewal and myonuclear accretion of MuSCs after acute skeletal muscle injury or skeletal muscle contraction. However, in a context of dystrophy such as Duchenne muscular dystrophy (DMD), the regenerative capacity of MuSCs is reduced, presumably due to an increase of the proliferation that is detrimental to differentiation. We are interested here in the potential of metabolism to regulate the myogenic activity of MuSCs in DMD via AMPK.

Overexpression of CPT1A disrupts the maintenance and regenerative function of muscle stem cells

The skeletal muscle satellite cells (SCs) mediate regeneration of myofibers upon injury. As they switch from maintenance (quiescence) to regeneration, their relative reliance on glucose and fatty acid metabolism alters. To explore the contribution of mitochondrial fatty acid oxidation (FAO) pathway to SCs and myogenesis, we examined the role of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme of FAO. CPT1A is highly expressed in quiescent SCs (QSCs) compared with activated and proliferating SCs, and its expression level decreases during myogenic differentiation. Myod1Cre-driven overexpression (OE) of Cpt1a in embryonic myoblasts (Cpt1aMTG) reduces muscle weight, grip strength, and contractile force without affecting treadmill endurance of adult mice. Adult Cpt1aMTG mice have reduced number of SC, impairing muscle regeneration and promoting lipid infiltration. Similarly, Pax7CreER-driven, tamoxifen-inducible Cpt1a-OE in QSCs of adult muscles (Cpt1aPTG) leads to depletion of SCs and compromises muscle regeneration. The reduced proliferation of Cpt1a-OE SCs is associated with elevated level of acyl-carnitine, and acyl-carnitine treatment impedes proliferation of wildtype SCs. These findings indicate that aberrant level of CPT1A elevates acyl-carnitine to impair the maintenance, proliferation and regenerative function of SCs.

ACAT1 Induces the Differentiation of Glioblastoma Cells by Rewiring Choline Metabolism

Abnormal differentiation of cells is a hallmark of malignancy. Induction of cancer-cell differentiation is emerging as a novel therapeutic strategy with low toxicity in hematological malignances, but whether such treatment can be used in solid tumors is not known. Here, we uncovered a novel function of acetyl coenzyme A acetyltransferase (ACAT1) in regulating the differentiation of glioblastoma (GBM) cells. Inhibition of ACAT1 promoted the differentiation of GBM cells into astrocytes but also delayed tumor growth. Mechanistically, suppression of ACAT1 restored mitochondrial function and led to metabolic "reprogramming" in GBM cells: reduction of fatty-acid oxidation and acetyl-CoA, but an increase in free fatty acids. Importantly, ACAT1 negatively regulated the choline metabolic pathway, which is crucial for the differentiation of GBM cells. Finally, we demonstrated that a naturally available substance, chlorogenic acid (CHA), could inhibit phosphorylation of ACAT1 and so delay GBM progression, CHA is a promising candidate to treat GBM because it could induce the differentiation of cancer cells.

Culturing Conditions Dictate the Composition and Pathways Enrichment of Human and Rat Perirenal Adipose-Derived Stromal Cells' Secretomes

Understanding the impact of various culturing strategies on the secretome composition of adipose-derived stromal cells (ASC) enhances their therapeutic potential. This study investigated changes in the secretome of perirenal ASC (prASC) under different conditions: normoxia, cytokine exposure, high glucose, hypoxia, and hypoxia with high glucose. Using mass spectrometry and enrichment clustering analysis, we found that normoxia enriched pathways related to extracellular matrix (ECM) organization, platelet degranulation, and insulin-like growth factor (IGF) transport and uptake. Cytokine exposure influenced metabolism, vascular development, and protein processing pathways. High glucose affected the immune system, metabolic processes, and IGF transport and uptake. Hypoxia impacted immune and metabolic processes and protein processing. Combined hypoxia and high glucose influenced the immune system, IGF transport and uptake, and ECM organization. Our findings highlight the potential of manipulating culturing conditions to produce secretomes with distinct protein and functional profiles, tailoring therapeutic strategies accordingly.

Reprogramming hematopoietic stem cell metabolism in lung cancer: glycolysis, oxidative phosphorylation, and the role of 2-DG

Hematopoietic stem cells (HSCs) exhibit significant functional and metabolic alterations within the lung cancer microenvironment, contributing to tumor progression and immune evasion by increasing differentiation into myeloid-derived suppressor cells (MDSCs). Our aim is to analyze the metabolic transition of HSCs from glycolysis to oxidative phosphorylation (OXPHOS) in lung cancer and determine its effects on HSC functionality. Using a murine Lewis Lung Carcinoma lung cancer model, we conducted metabolic profiling of long-term and short-term HSCs, as well as multipotent progenitors, comparing their metabolic states in normal and cancer conditions. We measured glucose uptake using 2-[N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino]-2-Deoxyglucose (2-NBDG) and assessed levels of lactate, acetyl-coenzyme A, and ATP. Mitochondrial functionality was evaluated through flow cytometry, alongside the impact of the glucose metabolism inhibitor 2-DG on HSC differentiation and mitochondrial activity. HSCs under lung cancer conditions showed increased glucose uptake and lactate production, with an associated rise in OXPHOS activity, marking a metabolic shift. Treatment with 2-DG led to decreased T-HSCs and MDSCs and an increased red blood cell count, highlighting its potential to influence metabolic and differentiation pathways in HSCs. This study provides novel insights into the metabolic reprogramming of HSCs in lung cancer, emphasizing the critical shift from glycolysis to OXPHOS and its implications for the therapeutic targeting of cancer-related metabolic pathways.

Emerging Landscape of Mesenchymal Stem Cell Senescence Mechanisms and Implications on Therapeutic Strategies

Mesenchymal stem cells (MSCs) hold significant promise for regenerative medicine and tissue engineering due to their unique multipotent differentiation ability and immunomodulatory properties. MSC therapy is widely discussed and utilized in clinical treatment. However, during both in vitro expansion and in vivo transplantation, MSCs are prone to senescence, an irreversible growth arrest characterized by morphological, gene expression, and functional changes in genomic regulation. The microenvironment surrounding MSCs plays a crucial role in modulating their senescence phenotype, influenced by factors such as hypoxia, inflammation, and aging status. Numerous strategies targeting MSC senescence have been developed, including senolytics and senomorphic agents, antioxidant and exosome therapies, mitochondrial transfer, and niche modulation. Novel approaches addressing replicative senescence have also emerged. This paper comprehensively reviews the current molecular manifestations of MSC senescence, addresses the environmental impact on senescence, and highlights potential therapeutic strategies to mitigate senescence in MSC-based therapies. These insights aim to enhance the efficacy and understanding of MSC therapies.

PGC-1α drives small cell neuroendocrine cancer progression towards an ASCL1-expressing subtype with increased mitochondrial capacity

Adenocarcinomas from multiple tissues can evolve into lethal, treatment-resistant small cell neuroendocrine (SCN) cancers comprising multiple subtypes with poorly defined metabolic characteristics. The role of metabolism in directly driving subtype determination remains unclear. Through bioinformatics analyses of thousands of patient tumors, we identified enhanced PGC-1α-a potent regulator of oxidative phosphorylation (OXPHOS)-in various SCN cancers (SCNCs), closely linked with neuroendocrine differentiation. In a patient-derived prostate tissue SCNC transformation system, the ASCL1-expressing neuroendocrine subtype showed elevated PGC-1α expression and increased OXPHOS activity. Inhibition of PGC-1α and OXPHOS reduced the proliferation of SCN lung and prostate cancer cell lines and blocked SCN prostate tumor formation. Conversely, enhancing PGC- 1α and OXPHOS, validated by small-animal Positron Emission Tomography mitochondrial imaging, tripled the SCN prostate tumor formation rate and promoted commitment to the ASCL1 lineage. These results establish PGC-1α as a driver of SCNC progression and subtype determination, highlighting novel metabolic vulnerabilities in SCNCs across different tissues.

STATEMENT OF SIGNIFICANCE

Our study provides functional evidence that metabolic reprogramming can directly impact cancer phenotypes and establishes PGC-1α-induced mitochondrial metabolism as a driver of SCNC progression and lineage determination. These mechanistic insights reveal common metabolic vulnerabilities across SCNCs originating from multiple tissues, opening new avenues for pan-SCN cancer therapeutic strategies.

Obesity-driven mitochondrial dysfunction in human adipose tissue-derived mesenchymal stem/stromal cells involves epigenetic changes

Obesity exacerbates tissue degeneration and compromises the integrity and reparative potential of mesenchymal stem/stromal cells (MSCs), but the underlying mechanisms have not been sufficiently elucidated. Mitochondria modulate the viability, plasticity, proliferative capacity, and differentiation potential of MSCs. We hypothesized that alterations in the 5-hydroxymethylcytosine (5hmC) profile of mitochondria-related genes may mediate obesity-driven dysfunction of human adipose-derived MSCs. MSCs were harvested from abdominal subcutaneous fat of obese and age/sex-matched non-obese subjects (n = 5 each). The 5hmC profile and expression of nuclear-encoded mitochondrial genes were examined by hydroxymethylated DNA immunoprecipitation sequencing (h MeDIP-seq) and mRNA-seq, respectively. MSC mitochondrial structure (electron microscopy) and function, metabolomics, proliferation, and neurogenic differentiation were evaluated in vitro, before and after epigenetic modulation. hMeDIP-seq identified 99 peaks of hyper-hydroxymethylation and 150 peaks of hypo-hydroxymethylation in nuclear-encoded mitochondrial genes from Obese- versus Non-obese-MSCs. Integrated hMeDIP-seq/mRNA-seq analysis identified a select group of overlapping (altered levels of both 5hmC and mRNA) nuclear-encoded mitochondrial genes involved in ATP production, redox activity, cell proliferation, migration, fatty acid metabolism, and neuronal development. Furthermore, Obese-MSCs exhibited decreased mitochondrial matrix density, membrane potential, and levels of fatty acid metabolites, increased superoxide production, and impaired neuronal differentiation, which improved with epigenetic modulation. Obesity elicits epigenetic changes in mitochondria-related genes in human adipose-derived MSCs, accompanied by structural and functional changes in their mitochondria and impaired fatty acid metabolism and neurogenic differentiation capacity. These observations may assist in developing novel therapies to preserve the potential of MSCs for tissue repair and regeneration in obese individuals.

Energy Metabolism in Human Pluripotent Stem and Differentiated Cells Compared Using a Seahorse XF96 Extracellular Flux Analyzer

Evaluating cell metabolism is crucial during pluripotent stem cell (PSC) differentiation and somatic cell reprogramming as it affects cell fate. As cultured stem cells are heterogeneous, a comparative analysis of relative metabolism using existing metabolic analysis methods is difficult, resulting in inaccuracies. In this study, we measured human PSC basal metabolic levels using a Seahorse analyzer. We used fibroblasts, human induced PSCs, and human embryonic stem cells to monitor changes in basal metabolic levels according to cell number and determine the number of cells suitable for analysis. We evaluated normalization methods using glucose and selected the most suitable for the metabolic analysis of heterogeneous PSCs during the reprogramming stage. The response of fibroblasts to glucose increased with starvation time, with oxygen consumption rate and extracellular acidification rate responding most effectively to glucose 4 hours after starvation and declining after 5 hours of starvation. Fibroblasts and PSCs achieved appropriate responses to glucose without damaging their metabolism 2∼4 and 2∼3 hours after starvation, respectively. We developed a novel method for comparing basal metabolic rates of fibroblasts and PSCs, focusing on quantitative analysis of glycolysis and oxidative phosphorylation using glucose without enzyme inhibitors. This protocol enables efficient comparison of energy metabolism among cell types, including undifferentiated PSCs, differentiated cells, and cells undergoing cellular reprogramming, and addresses critical issues, such as differences in basal metabolic levels and sensitivity to normalization, providing valuable insights into cellular energetics.

Trans-omic profiling uncovers molecular controls of early human cerebral organoid formation

Defining the molecular networks orchestrating human brain formation is crucial for understanding neurodevelopment and neurological disorders. Challenges in acquiring early brain tissue have incentivized the use of three-dimensional human pluripotent stem cell (hPSC)-derived neural organoids to recapitulate neurodevelopment. To elucidate the molecular programs that drive this highly dynamic process, here, we generate a comprehensive trans-omic map of the phosphoproteome, proteome, and transcriptome of the exit of pluripotency and neural differentiation toward human cerebral organoids (hCOs). These data reveal key phospho-signaling events and their convergence on transcriptional factors to regulate hCO formation. Comparative analysis with developing human and mouse embryos demonstrates the fidelity of our hCOs in modeling embryonic brain development. Finally, we demonstrate that biochemical modulation of AKT signaling can control hCO differentiation. Together, our data provide a comprehensive resource to study molecular controls in human embryonic brain development and provide a guide for the future development of hCO differentiation protocols.

Rbm46 inhibits reactive oxygen species in mouse embryonic stem cells through modulating BNIP3-mediated mitophagy

Embryonic stem cells (ESCs) exhibit a metabolic preference for glycolysis over oxidative phosphorylation to meet their substantial adenosine triphosphate (ATP) demands during self-renewal. This metabolic choice inherently maintains low mitochondrial activity and minimal reactive oxygen species (ROS) generation. Nonetheless, the intricate molecular mechanisms governing the restraint of ROS production and the mitigation of cellular damage remain incompletely elucidated. In this study, we reveal the pivotal role of RNA-binding motif protein 46 (RBM46) in ESCs, acting as a direct post transcriptional regulator of ROS levels by modulating BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (Bnip3) mRNA expression. Rbm46 knockout lead to diminished mitochondrial autophagy, culminating in elevated ROS within ESCs, disrupting the delicate balance required for healthy self-renewal. These findings provide insights into a novel mechanism governing ROS regulation in ESCs.

Mitochondrial heterogeneity and adaptations to cellular needs

Although it is well described that mitochondria are at the epicentre of the energy demands of a cell, it is becoming important to consider how each cell tailors its mitochondrial composition and functions to suit its particular needs beyond ATP production. Here we provide insight into mitochondrial heterogeneity throughout development as well as in tissues with specific energy demands and discuss how mitochondrial malleability contributes to cell fate determination and tissue remodelling.

Crosstalk between DNA Damage Repair and Metabolic Regulation in Hematopoietic Stem Cells

Self-renewal and differentiation are two characteristics of hematopoietic stem cells (HSCs). Under steady physiological conditions, most primitive HSCs remain quiescent in the bone marrow (BM). They respond to different stimuli to refresh the blood system. The transition from quiescence to activation is accompanied by major changes in metabolism, a fundamental cellular process in living organisms that produces or consumes energy. Cellular metabolism is now considered to be a key regulator of HSC maintenance. Interestingly, HSCs possess a distinct metabolic profile with a preference for glycolysis rather than oxidative phosphorylation (OXPHOS) for energy production. Byproducts from the cellular metabolism can also damage DNA. To counteract such insults, mammalian cells have evolved a complex and efficient DNA damage repair (DDR) system to eliminate various DNA lesions and guard genomic stability. Given the enormous regenerative potential coupled with the lifetime persistence of HSCs, tight control of HSC genome stability is essential. The intersection of DDR and the HSC metabolism has recently emerged as an area of intense research interest, unraveling the profound connections between genomic stability and cellular energetics. In this brief review, we delve into the interplay between DDR deficiency and the metabolic reprogramming of HSCs, shedding light on the dynamic relationship that governs the fate and functionality of these remarkable stem cells. Understanding the crosstalk between DDR and the cellular metabolism will open a new avenue of research designed to target these interacting pathways for improving HSC function and treating hematologic disorders.

Integrative physiology and transcriptome reveal salt-tolerance differences between two licorice species: Ion transport, Casparian strip formation and flavonoids biosynthesis

BACKGROUND

Glycyrrhiza inflata Bat. and Glycyrrhiza uralensis Fisch. are both original plants of 'Gan Cao' in the Chinese Pharmacopoeia, and G. uralensis is currently the mainstream variety of licorice and has a long history of use in traditional Chinese medicine. Both of these species have shown some degree of tolerance to salinity, G. inflata exhibits higher salt tolerance than G. uralensis and can grow on saline meadow soils and crusty saline soils. However, the regulatory mechanism responsible for the differences in salt tolerance between different licorice species is unclear. Due to land area-related limitations, the excavation and cultivation of licorice varieties in saline-alkaline areas that both exhibit tolerance to salt and contain highly efficient active substances are needed. The systematic identification of the key genes and pathways associated with the differences in salt tolerance between these two licorice species will be beneficial for cultivating high-quality salt-tolerant licorice G. uralensis plant varieties and for the long-term development of the licorice industry. In this research, the differences in growth response indicators, ion accumulation, and transcription expression between the two licorice species were analyzed.

RESULTS

This research included a comprehensive comparison of growth response indicators, including biomass, malondialdehyde (MDA) levels, and total flavonoids content, between two distinct licorice species and an analysis of their ion content and transcriptome expression. In contrast to the result found for G. uralensis, the salt treatment of G. inflata ensured the stable accumulation of biomass and total flavonoids at 0.5 d, 15 d, and 30 d and the restriction of Na+ to the roots while allowing for more K+ and Ca2+ accumulation. Notably, despite the increase in the Na+ concentration in the roots, the MDA concentration remained low. Transcriptome analysis revealed that the regulatory effects of growth and ion transport on the two licorice species were strongly correlated with the following pathways and relevant DEGs: the TCA cycle, the pentose phosphate pathway, and the photosynthetic carbon fixation pathway involved in carbon metabolism; Casparian strip formation (lignin oxidation and translocation, suberin formation) in response to Na+; K+ and Ca2+ translocation, organic solute synthesis (arginine, polyamines, GABA) in response to osmotic stresses; and the biosynthesis of the nonenzymatic antioxidants carotenoids and flavonoids in response to antioxidant stress. Furthermore, the differential expression of the DEGs related to ABA signaling in hormone transduction and the regulation of transcription factors such as the HSF and GRAS families may be associated with the remarkable salt tolerance of G. inflata.

CONCLUSION

Compared with G. uralensis, G. inflata exhibits greater salt tolerance, which is primarily attributable to factors related to carbon metabolism, endodermal barrier formation and development, K+ and Ca2+ transport, biosynthesis of carotenoids and flavonoids, and regulation of signal transduction pathways and salt-responsive transcription factors. The formation of the Casparian strip, especially the transport and oxidation of lignin precursors, is likely the primary reason for the markedly higher amount of Na+ in the roots of G. inflata than in those of G. uralensis. The tendency of G. inflata to maintain low MDA levels in its roots under such conditions is closely related to the biosynthesis of flavonoids and carotenoids and the maintenance of the osmotic balance in roots by the absorption of more K+ and Ca2+ to meet growth needs. These findings may provide new insights for developing and cultivating G. uralensis plant species selected for cultivation in saline environments or soils managed through agronomic practices that involve the use of water with a high salt content.

Oxaloacetate as new inducer for osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells in vitro

BACKGROUND

Mitochondrial organelles play a crucial role in cellular metabolism so different cell types exhibit diverse metabolic and energy demands. Therefore, alternations in the intracellular distribution, quantity, function, and structure of mitochondria are required for stem cell differentiation. Finding an effective inducer capable of modulating mitochondrial activity is critical for the differentiation of specific stem cells into osteo-like cells for addressing issues related to osteogenic disorders. This study aimed to investigate the effect of oxaloacetate (OAA) on the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) in vitro.

METHODS AND RESULTS

First, the most favorable OAA concentration was measured through MTT assay and subsequently confirmed using acridine orange staining. Human ADSCs were cultured in osteogenic medium supplemented with OAA and analyzed on days 7 and 14 of differentiation. Various assays including alkaline phosphatase assay (ALP), cellular calcium content assay, mineralized matrix staining with alizarin red, catalase (CAT) and superoxide dismutase (SOD) activity, and real-time RT-PCR analysis of three bone-specific markers (ALP, osteocalcin, and collagen type I) were conducted to characterize the differentiated cells. Following viability assessment, OAA at a concentration of 1 µM was considered the optimal dosage for further studies. The results of osteogenic differentiation assays showed that OAA at a concentration of 1 × 10- 6 M significantly increased ALP enzyme activity, mineralization, CAT and SOD activity and the expression of bone-specific genes in differentiated cells compared to control groups in vitro.

CONCLUSIONS

In conclusion, the fundings from this study suggest that OAA possesses favorable properties that make it a potential candidate for application in medical bone regeneration.

Glucose-derived glutamate drives neuronal terminal differentiation in vitro

Neuronal maturation is the phase during which neurons acquire their final characteristics in terms of morphology, electrical activity, and metabolism. However, little is known about the metabolic pathways governing neuronal maturation. Here, we investigate the contribution of the main metabolic pathways, namely glucose, glutamine, and fatty acid oxidation, during the maturation of primary rat hippocampal neurons. Blunting glucose oxidation through the genetic and chemical inhibition of the mitochondrial pyruvate transporter reveals that this protein is critical for the production of glutamate, which is required for neuronal arborization, proper dendritic elongation, and spine formation. Glutamate supplementation in the early phase of differentiation restores morphological defects and synaptic function in mitochondrial pyruvate transporter-inhibited cells. Furthermore, the selective activation of metabotropic glutamate receptors restores the impairment of neuronal differentiation due to the reduced generation of glucose-derived glutamate and rescues synaptic local translation. Fatty acid oxidation does not impact neuronal maturation. Whereas glutamine metabolism is important for mitochondria, it is not for endogenous glutamate production. Our results provide insights into the role of glucose-derived glutamate as a key player in neuronal terminal differentiation.

Enhancement of de novo lipogenesis by the IDH1 and IDH2-dependent reverse TCA cycle maintains the growth and angiogenic capacity of bone marrow-derived endothelial progenitor cells under hypoxia

BACKGROUND

Bone marrow-derived endothelial progenitor cells (EPCs) play a dynamic role in maintaining the structure and function of blood vessels. But how these cells maintain their growth and angiogenic capacity under bone marrow hypoxic niche is still unclear. This study aims to explore the mechanisms from a perspective of cellular metabolism.

METHODS

XFe96 Extracellular Flux Analyzer was used to analyze the metabolic status of EPCs. Gas Chromatography-Mass Spectrometry (GC-MS) was used to trace the carbon movement of 13C-labeled glucose and glutamine under 1 % O2 (hypoxia) and ∼20 % O2 (normoxia). Moreover, RNA interference, targeting isocitrate dehydrogenase-1 (IDH1) and IDH2, was used to inhibit the reverse tricarboxylic acid (TCA) cycle and analyze metabolic changes via isotope tracing as well as changes in cell growth and angiogenic potential under hypoxia. The therapeutic potential of EPCs under hypoxia was investigated in the ischemic hindlimb model.

RESULTS

Compared with normoxic cells, hypoxic cells showed increased glycolysis and decreased mitochondrial respiration. Isotope metabolic tracing revealed that under hypoxia, the forward TCA cycle was decreased and the reverse TCA cycle was enhanced, mediating the conversion of α-ketoglutarate (α-KG) into isocitrate/citrate, and de novo lipid synthesis was promoted. Downregulation of IDH1 or IDH2 under hypoxia suppressed the reverse TCA cycle, attenuated de novo lipid synthesis (DNL), elevated α-KG levels, and decreased the expression of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (VEGFA), eventually inhibiting the growth and angiogenic capacity of EPCs. Importantly, the transplantation of hypoxia-cultured EPCs in a mouse model of limb ischemia promoted new blood vessel regeneration and blood supply recovery in the ischemic area better than the transplantation of normoxia-cultured EPCs.

CONCLUSIONS

Under hypoxia, the IDH1- and IDH2-mediated reverse TCA cycle promotes glutamine-derived de novo lipogenesis and stabilizes the expression of α-KG and HIF-1α, thereby enhancing the growth and angiogenic capacity of EPCs.

Metabolic reprogramming of glycolysis favors cartilage progenitor cells rejuvenation

Osteoarthritis (OA), the leading cause of disability in the elderly, still lacks effective treatment due to the unelucidated mechanisms of pathogenesis and progression. In cartilage, although the solo cell type of chondrocytes is resident, cartilage progenitor cells (CPCs) are identified. Chondrocytes in cartilage mainly utilize glycolysis because of the low oxygen tension. Until now, whether the metabolic pathway changes are associated with OA initiation or progression, as well as the biology of CPCs, remains fully clarified. By reviewing relevant literature from previous functional studies, we further mined recently published mouse and human chondrocytes single-cell RNA-sequencing datasets to explore gene expression profiles shift in OA initiation or during OA progression, regarding metabolism. In this review, we demonstrated that chondrocytes' metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) in OA initiation or during OA progression. Genes that related to OXPHOS, electron transport, mitochondrial translation, and mitochondrial respiratory chain complex assembly were upregulated in chondrocytes of injured cartilage or during OA progression. In addition, compared to OXPHOS, glycolysis facilitates CPC expansion and chondrogenic potential. The collated information suggests a potential therapeutic for OA through metabolic reprogramming of glycolysis to interrupt OA pathology and favor CPCs rejuvenation to restore healthy cartilage.

Glutathione safeguards TET-dependent DNA demethylation and is critical for the acquisition of totipotency and pluripotency during preimplantation development

During early development, both genome-wide epigenetic reprogramming and metabolic remodeling are hallmark changes of normal embryogenesis. However, little is known about their relationship and developmental functions during the preimplantation window, which is essential for the acquisition of totipotency and pluripotency. Herein, we reported that glutathione (GSH), a ubiquitous intracellular protective antioxidant that maintains mitochondrial function and redox homeostasis, plays a critical role in safeguarding postfertilization DNA demethylation and is essential for establishing developmental potential in preimplantation embryos. By profiling mitochondria-related transcriptome that coupled with different pluripotency, we found GSH is a potential marker that is tightly correlated with full pluripotency, and its beneficial effect on prompting developmental potential was functionally conformed using in vitro fertilized mouse and bovine embryos as the model. Mechanistic study based on preimplantation embryos and embryonic stem cells further revealed that GSH prompts the acquisition of totipotency and pluripotency by facilitating ten-eleven-translocation (TET)-dependent DNA demethylation, and ascorbic acid (AsA)-GSH cycle is implicated in the process. In addition, we also reported that GSH serves as an oviductal paracrine factor that supports development potential of preimplantation embryos. Thus, our results not only advance the current knowledge of functional links between epigenetic reprogramming and metabolic remodeling during preimplantation development but also provided a promising approach for improving current in vitro culture system for assisted reproductive technology.

Developmental regulation of cellular metabolism is required for intestinal elongation and rotation

Malrotation of the intestine is a prevalent birth anomaly, the etiology of which remains poorly understood. Here, we show that late-stage exposure of Xenopus embryos to atrazine, a widely used herbicide that targets electron transport chain (ETC) reactions, elicits intestinal malrotation at high frequency. Interestingly, atrazine specifically inhibits the cellular morphogenetic events required for gut tube elongation, including cell rearrangement, differentiation and proliferation; insufficient gut lengthening consequently reorients the direction of intestine rotation. Transcriptome analyses of atrazine-exposed intestines reveal misexpression of genes associated with glycolysis and oxidative stress, and metabolomics shows that atrazine depletes key glycolytic and tricarboxylic acid cycle metabolites. Moreover, cellular bioenergetics assays indicate that atrazine blocks a crucial developmental transition from glycolytic ATP production toward oxidative phosphorylation. Atrazine-induced defects are phenocopied by rotenone, a known ETC Complex I inhibitor, accompanied by elevated reactive oxygen species, and rescued by antioxidant supplementation, suggesting that malrotation may be at least partly attributable to redox imbalance. These studies reveal roles for metabolism in gut morphogenesis and implicate defective gut tube elongation and/or metabolic perturbations in the etiology of intestinal malrotation.

Adaptation of Glucose Metabolism to Limb Autotomy and Regeneration in the Chinese Mitten Crab

Limb autotomy and regeneration represent distinctive responses of crustaceans to environmental stress. Glucose metabolism plays a pivotal role in energy generation for tissue development and regeneration across various species. However, the relationship between glucose metabolism and tissue regeneration in crustaceans remains elusive. Therefore, this study is aimed at analyzing the alterations of glucose metabolic profile during limb autotomy and regeneration in Eriocheir sinensis, while also evaluating the effects of carbohydrate supplementation on limb regeneration. The results demonstrated that limb autotomy triggered a metabolic profile adaption at the early stage of regeneration. Hemolymph glucose levels were elevated, and multiple glucose catabolic pathways were enhanced in the hepatopancreas. Additionally, glucose and ATP levels in the regenerative limb were upregulated, along with increased expression of glucose transporters. Furthermore, the gene expression and activity of enzymes involved in gluconeogenesis were repressed in the hepatopancreas. These findings indicate that limb regeneration triggers metabolic profile adaptations to meet the elevated energy requirements. Moreover, the study observed that supplementation with corn starch enhanced limb regeneration capacity by promoting wound healing and blastema growth. Interestingly, dietary carbohydrate addition influenced limb regeneration by stimulating gluconeogenesis rather than glycolysis in the regenerative limb. Thus, these results underscore the adaptation of glucose metabolism during limb autotomy and regeneration, highlighting its essential role in the limb regeneration process of E. sinensis.

Large-scale cultivation of human iPS cells in bioreactor with reciprocal mixing

A substantial number of human iPS cells (hiPSCs) is needed for cell therapy to be successful against various diseases. We previously reported on a bioreactor with reciprocal mixing that produces specific physical properties that differ from those of conventional bioreactors with rotary paddle stirring. Moreover, such reactors not only provide a homogeneous environment but also allow the control of spheroid size by changing the mixing speed. In this study, we applied this bioreactor to the large-scale cultivation of hiPSCs. Approximately 10 billion hiPSCs were obtained from 2.0 L of culture, and the high expression of pluripotency markers was maintained. Our findings indicate that a bioreactor with reciprocal mixing can be used for large-scale hiPSC cultivation.

Image-guided metabolomics and transcriptomics reveal tumour heterogeneity in luminal A and B human breast cancer beyond glucose tracer uptake

BACKGROUND

Breast cancer is a metabolically heterogeneous disease, and although the concept of heterogeneous cancer metabolism is known, its precise role in human breast cancer is yet to be fully elucidated.

METHODS

We investigated in an explorative approach a cohort of 42 primary mamma carcinoma patients with positron emission tomography/magnetic resonance imaging (PET/MR) prior to surgery, followed by histopathology and molecular diagnosis. From a subset of patients, which showed high metabolic heterogeneity based on tracer uptake and pathology classification, tumour centre and periphery specimen tissue samples were further investigated by a targeted breast cancer gene expression panel and quantitative metabolomics by nuclear magnetic resonance (NMR) spectroscopy. All data were analysed in a combinatory approach.

RESULTS

[18 F]FDG (2-deoxy-2-[fluorine-18]fluoro-d-glucose) tracer uptake confirmed dominance of glucose metabolism in the breast tumour centre, with lower levels in the periphery. Additionally, we observed differences in lipid and proliferation related genes between luminal A and B subtypes in the centre and periphery. Tumour periphery showed elevated acetate levels and enrichment in lipid metabolic pathways genes especially in luminal B. Furthermore, serine was increased in the periphery and higher expression of thymidylate synthase (TYMS) indicated one-carbon metabolism increased in tumour periphery. The overall metabolic activity based on [18 F]FDG uptake of luminal B subtype was higher than that of luminal A and the difference between the periphery and centre increased with tumour grade.

CONCLUSION

Our analysis indicates variations in metabolism among different breast cancer subtypes and sampling locations which details the heterogeneity of the breast tumours. Correlation analysis of [18 F]FDG tracer uptake, transcriptome and tumour metabolites like acetate and serine facilitate the search for new candidates for metabolic tracers and permit distinguishing luminal A and B. This knowledge may help to differentiate subtypes preclinically or to provide patients guide for neoadjuvant therapy and optimised surgical protocols based on individual tumour metabolism.

Metabolic control of induced pluripotency

Pluripotent stem cells of the mammalian epiblast and their cultured counterparts-embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs)-have the capacity to differentiate in all cell types of adult organisms. An artificial process of reactivation of the pluripotency program in terminally differentiated cells was established in 2006, which allowed for the generation of induced pluripotent stem cells (iPSCs). This iPSC technology has become an invaluable tool in investigating the molecular mechanisms of human diseases and therapeutic drug development, and it also holds tremendous promise for iPSC applications in regenerative medicine. Since the process of induced reprogramming of differentiated cells to a pluripotent state was discovered, many questions about the molecular mechanisms involved in this process have been clarified. Studies conducted over the past 2 decades have established that metabolic pathways and retrograde mitochondrial signals are involved in the regulation of various aspects of stem cell biology, including differentiation, pluripotency acquisition, and maintenance. During the reprogramming process, cells undergo major transformations, progressing through three distinct stages that are regulated by different signaling pathways, transcription factor networks, and inputs from metabolic pathways. Among the main metabolic features of this process, representing a switch from the dominance of oxidative phosphorylation to aerobic glycolysis and anabolic processes, are many critical stage-specific metabolic signals that control the path of differentiated cells toward a pluripotent state. In this review, we discuss the achievements in the current understanding of the molecular mechanisms of processes controlled by metabolic pathways, and vice versa, during the reprogramming process.

High glucose levels delay the senescence of stem cells from human exfoliated deciduous teeth by suppressing autophagy

OBJECTIVE

In this study, we aimed to investigate the effects of varying glucose concentrations on the proliferation and senescence of stem cells from human exfoliated deciduous teeth (SHED) compared to human bone marrow-derived mesenchymal stem cells (hBMSC), and preliminarily clarify the difference of glucose metabolism between SHED and hBMSC.

DESIGN

We cultured SHED and hBMSC in the presence of increasing glucose concentrations to study the role of glucose in cell viability, proliferation, and senescence. Gene expression related to the stemness of mesenchymal stem cells was evaluated using real-time quantitative reverse transcription-polymerase chain reaction. In addition, glucose consumption, lactic acid production, oxidative phosphorylation, and glycolysis were measured to analyze glucose metabolism and expression of autophagy-related markers, including microtubule-associated proteins 1 A/1B light chain 3 B and p62.

RESULTS

While a high glucose level (4.5 g/L) promoted the proliferation of both SHED and hBMSC, it delayed senescence in SHED via autophagy inhibition but accelerated hBMSC senescence. In contrast to that in hBMSC, glycolysis in SHED was enhanced under the high-glucose culture condition.

CONCLUSIONS

The glycometabolism of SHED and hBMSC differed, and a high glucose culture medium was more favorable for SHED.

Multiple roles for AU-rich RNA binding proteins in the development of haematologic malignancies and their resistance to chemotherapy

Post-transcriptional regulation by RNA binding proteins can determine gene expression levels and drive changes in cancer cell proteomes. Identifying mechanisms of protein-RNA binding, including preferred sequence motifs bound in vivo, provides insights into protein-RNA networks and how they impact mRNA structure, function, and stability. In this review, we will focus on proteins that bind to AU-rich elements (AREs) in nascent or mature mRNA where they play roles in response to stresses encountered by cancer cells. ARE-binding proteins (ARE-BPs) specifically impact alternative splicing, stability, decay and translation, and formation of RNA-rich biomolecular condensates like cytoplasmic stress granules (SGs). For example, recent findings highlight the role of ARE-BPs - like TIAR and HUR - in chemotherapy resistance and in translational regulation of mRNAs encoding pro-inflammatory cytokines. We will discuss emerging evidence that different modes of ARE-BP activity impact leukaemia and lymphoma development, progression, adaptation to microenvironment and chemotherapy resistance.

Sniping Cancer Stem Cells with Nanomaterials

Cancer stem cells (CSCs) drive tumor initiation, progression, and therapeutic resistance due to their self-renewal and differentiation capabilities. Despite encouraging progress in cancer treatment, conventional approaches often fail to eliminate CSCs, necessitating the development of precise targeted strategies. Recent advances in materials science and nanotechnology have enabled promising CSC-targeted approaches, harnessing the power of tailoring nanomaterials in diverse therapeutic applications. This review provides an update on the current landscape of nanobased precision targeting approaches against CSCs. We elucidate the nuanced application of organic, inorganic, and bioinspired nanomaterials across a spectrum of therapeutic paradigms, encompassing targeted therapy, immunotherapy, and multimodal synergistic therapies. By examining the accomplishments and challenges in this potential field, we aim to inform future efforts to advance nanomaterial-based therapies toward more effective "sniping" of CSCs and tumor clearance.