Under physiological conditions, adult stem cells are located in a special microenvironment, known as the niche, which is characterized by low oxygen levels. Hypoxia is a crucial factor regulating stem cell behavior, and in vitro normoxic culture often leads to the loss of pluripotency, resulting in reduced therapeutic potential of cells. In this study, we aimed to investigate the effects of cobalt chloride (CoCl2), a hypoxia-mimetic agent, on mesenchymal stem cells (MSCs) derived from different sources by inducing hypoxia-inducible factor-1α. Cell proliferation, migration, survival, and metabolic activity were assessed. CoCl2 treatment decreased the proliferation and migration and enhanced the survival of MSCs. Furthermore, a metabolic shift from oxidative phosphorylation to glycolysis was observed in cells. Overall, our findings provide important insights into the mechanisms by which hypoxic conditions differentially influence stem cells, facilitating the improvement of their therapeutic potential.

Energy metabolism homeostasis emerges as a dominant element influencing mesenchymal stem/stromal cells' trajectory of development. The predominant glycolysis activity is a primary driver of cell proliferation and maintenance of the high-energetic state. Here, we examined the functions of two crucial auxiliary pathways: the phosphate-pentose pathway (PPP) and fructose-2,6-biphosphate pathway (FBP) to evaluate their impact on the therapeutic potential of Adipose-Derived Stem/Stromal cells (ASCs) during prolonged culture in various oxygen conditions: 5 % O2 - physiological normoxia or 21 % O2 - atmospheric oxygen. Our findings demonstrate that ASCs cultured in 5 % O2 increased the rate of proliferation, migration, and expression of stemness factors, which is prominent during the initial and middle passages. Additionally, ASCs cultured in a 5 % O2 exhibited heightened protection mechanisms against free radicals, increased LDH gene expression, and elevated extracellular acidification rate (ECAR). By estimating the HIF-1α level, we concluded that 5 % oxygen conditions were insufficient to induce a profound hypoxic state in ASCs. However, at the protein level, both the PPP and FBP pathways appeared to be more active in young (2-passage) cells, regardless of oxygen conditions, and their activity diminished over time. Additionally, the chemical suppression of G6PDH by Polydatin and inhibition of PFKFB3 by PFK-158 in ASCs (passage-2) revealed dose- and time-dependent effect on decreasing migratory capabilities of cells. Nevertheless, our work underscores the adaptable nature of ASC metabolism to prevailing external conditions, with the aging of the culture contributing to the decline in glycolysis-associated auxiliary pathways.

ObjectiveThis study aimed to isolate and compare the mesenchymal stem cell characteristics of CD90+ cells from different fibrocartilage tissues in the temporomandibular joint (TMJ), the knee joint, and the intervertebral joint to further understand the similarities and differences of these 4 fibrocartilage tissues.MethodsCD90+ cells were isolated from TMJ disc, condylar cartilage, meniscus, and intervertebral disc by using magnetic-activated cell sorting. Cellular assays including 4.5-ethynyl-2'-deoxyuridine labeling, multilineage differentiation, colony formation, and cell migration were conducted to compare their mesenchymal stem cell characteristics. Immunofluorescent staining was performed for observing the expression of actively proliferating CD90+ cells within the tissues. H&E staining and Safranine O staining were used to compare the histological features.ResultsThe CD90+ cells derived from these 4 fibrocartilage tissues exhibited comparable cell proliferation abilities. However, the cells from the TMJ disc displayed limited multilineage differentiation potential, colony formation, and cell migration abilities in comparison with the cells from the other fibrocartilage tissues. In vivo, there was relatively more abundant expression of CD90+ cells in the TMJ disc during the early postnatal stage. The limited EDU+ cell numbers signified a low proliferation capacity of CD90+ cells in the TMJ disc. In addition, we observed a significant decrease in cell density and a restriction in the synthesis of extracellular proteoglycans in the TMJ disc.ConclusionOur study highlights the spatial heterogeneity of CD90+ cells in the fibrocartilages of different joint tissues, which may contribute to the limited cartilage repair capacity in the TMJ disc.

Disruption of low oxygen tension homeostasis during intervertebral disc degeneration inhibits endogenous stem cell viability and function, posing a challenge for endogenous regeneration. Here, to achieve sustained hypoxia manipulation, constructed hypoxia-inducible interpenetrating polymer network (IPN) hydrogel microspheres (HIMS) are constructed by microfluidics to integrate the hypoxic system with a stabilizing network. The IPN is synthesized through a two-step polymerization process, consisting of rapid photo-crosslinked gelatin methacrylate anhydride (GM) polymer I and slow enzyme-crosslinked vanillin-grafted gelatin (GV) polymer II. The enzymatic reaction between GV and laccase is able to create a hypoxic microenvironment to modulate oxygen tension in situ within the injured region. HIMS can reduce microenvironmental oxygen tension by 1/3 and maintain a hypoxic microenvironment for up to 5 days, thereby activating the PI3K/AKT/HIF-1α signaling pathway in endogenous stem cells to promote differentiation into nucleus pulposus-like cells. Additionally, NSC-Exos are loaded onto HIMS to trigger endogenous progenitor/stem cell recruitment and migration. Both in vitro and in vivo assays demonstrate that NSC-Exos@HIMS facilitates stem cell recruitment, targets differentiation, and stimulates extracellular matrix synthesis. Overall, the microspheres established herein provide a novel strategy for manipulating oxygen tension and enhancing endogenous tissue regeneration in injured regions during intervertebral disc degeneration.

Muscle stem cells (MuSCs) are the key to muscle regeneration. The activation and maintenance of MuSCs require the precise regulation of their microenvironments. Myofibers and other cells including endothelial cells, fibroblasts, and immune cell populations constitute the cell components of the MuSC niche. The communication between these cell populations and MuSCs play an essential role in muscle repair. Furthermore, the physical and chemical stimulations around MuSCs also affect the cell behaviors of MuSCs. Extracellular matrix (ECM) and the factors stored in it generate a repair-promoting niche for efficient muscle regeneration. Understanding the mechanism of muscle stem cell regulation is the basis of clinically optimizing muscle repair. In this review, we discuss recent findings about the microenvironments of MuSCs and their functions in muscle regeneration, which would shed light on new targets and strategies for muscle injury treatment.

Acute myeloid leukemia (AML) exhibits a pronounced ability to develop drug resistance and undergo disease relapse. Recent research has noticed that resistance to treatments could substantially be attributed to drug-tolerant persister (DTP) cells, which are capable of surviving under therapeutic pressures. These are transient, reversibly dormant cells with the capability to act as a reservoir for disease relapse. DTP cells utilize diverse adaptive strategies to optimize the ecological niche, undergo metabolic reprogramming, and interact with microenvironment. The persister state of AML is established through transient cellular reprogramming, thus allowing cells to survive the initial phase of drug therapy and develop drug resistance. Our review explores the identification and phenotypic characteristics of AML DTP cells, as well as their clinical relevance. We summarize the mechanisms underlying the persistence of AML DTP cells and the molecular attributes that define the DTP state. We further address the current challenges and future prospects of DTP-targeting approaches. Understanding these features may provide critical insights into novel therapeutic strategies aimed at targeting AML DTP cells, especially in the new era of immunotherapy against AML.

Iron is required for redox homeostasis but poses toxicity risks due to its redox activity. Erythropoiesis hence requires tight regulation of iron utilization for hemoglobin synthesis. The requirement for iron in erythropoiesis has necessitated the evolution of mechanisms to handle the iron required for hemoglobinization. FAM210B was identified as a regulator of mitochondrial iron import and heme synthesis in erythroid cell culture and zebrafish models. Here, we demonstrate that although FAM210B is required for erythroid differentiation and heme synthesis under standard cell culture conditions, holotransferrin supplementation was sufficient to chemically complement the iron-deficient phenotype. To investigate the role of FAM210B in erythropoiesis, we used knockout mice. Although Fam210b-/- mice were viable and did not exhibit overt erythropoietic defects in the bone marrow, the male mice exhibited an increase in serum transferrin, suggesting sex-specific alterations in systemic iron sensing. On phlebotomy-induced stress erythropoiesis, Fam210b-/- mice exhibited differences in serum transferrin levels, and more starkly, had markedly smaller spleens, indicating defects in stress response. Fam210b-/- males had defects in neutrophil and monocyte numbers, as well as decreased erythroid progenitor numbers during erythropoietic stress. Together, our findings show that Fam210b plays a key role in the splenic response to erythropoietic stress. Our findings reveal a critical role for FAM210B in mediating splenic stress erythropoiesis and suggest it may act as a sex-specific regulator, potentially linked to androgen signaling.

At different stages of life, from embryonic to postnatal, varying oxygen concentrations modulate cellular gene expression by enhancing or repressing hypoxia-inducible transcription factors. During embryonic/fetal life, these genes encode proteins involved in adapting to a low-oxygen environment, including the induction of specific enzymes related to glycolytic metabolism, erythropoiesis, angiogenesis, and vasculogenesis. However, oxygen concentrations fluctuate during intrauterine life, enabling the induction of tissue-specific differentiation processes. Fetal well-being is thus closely linked to the physiological benefits of a dynamically hypoxic environment. Premature birth entails the precocious exposure of the immature fetus to a more oxygen-rich environment compared to the womb. As a result, preterm newborns face a condition of relative hyperoxia, which alters the postnatal development of organs and contributes to prematurity-related diseases. However, until recently, the molecular mechanism by which high oxygen tension alters normal fetal differentiation remained unclear. In this review, we discuss the research trajectory followed by our research group, which suggests that early exposure to a relatively hyperoxic environment may impair preterm neonates due to reduced expression of the β3-adrenoceptor. Additionally, we explore how these impairments could be prevented through the pharmacological stimulation of the remaining β3-adrenoceptors. Recent preclinical studies demonstrate that pharmacological stimulation of the β3-adrenoceptor can decouple exposure to hyperoxia from its harmful effects, offering a glimpse of the possibility to recreating the conditions typical of intrauterine life, even after premature birth.

Hypoxia, a prevalent characteristic of solid tumors, substantially impairs the efficacy of cancer treatments. However, there are no feasible clinical approaches for treating hypoxic tumors. Here, we develop metal-phenolic networks (CuGI) utilizing the natural glycolysis inhibitor (epigallocatechin gallate) and the essential metal element in the human body (copper ions), specifically targeting and annihilating hypoxic cancer cells. CuGI redirects the metabolic pathway of hypoxic cancer cells from anaerobic glycolysis to oxidative phosphorylation, thereby enhancing reactive oxygen species production and promoting oligomerization of lipoylated proteins in the tricarboxylic acid cycle. Through targeted induction of oxidative and proteotoxic stresses, CuGI induces apoptosis and cuproptosis specifically in cancer cells under hypoxic conditions while sparing normal cells. Moreover, cancer cell membrane-coated CuGI (CuGI@CM) exhibits enhanced tumor penetration effect and demonstrates commendable biocompatibility, effectively suppressing colorectal tumor growth. Importantly, CuGI@CM, when combined with vascular disruptors or radiotherapy which aggravate tumor hypoxia, synergistically potentiates therapeutic efficacy. Thus, CuGI represents a specific and potent nanotherapeutic capable of selectively eliminating hypoxic tumors, offering promise in combination therapies to address tumor hypoxia.

SETD5, an atypical member of the histone lysine methyltransferase family known for its association with cancer stemness, is a significant predictor of unfavorable survival outcomes in non-small cell lung cancer (NSCLC). However, the function of SETD5 in NSCLC stemness remains unclear, and whether it is an active H3K36me3 is controversial. Consequently, further investigation is required to clarify the pivotal role of SETD5 in NSCLC stemness and its related mechanism. Thus, this study employed the NSCLC tissue microarray and bioinformatics tools to analyze SETD5 expression and determine its effect on stemness and investigated the role of SETD5 in the metastasis of NSCLC using in vitro and in vivo analyses. The findings indicated high SETD5 expression in embryonic and NSCLC tissues, which was related to the pathological tumor stage, lymph node metastasis, and clinical stage, indicating that SETD5 could be used as a biomarker and prognostic factor in NSCLC. In addition, we found that SETD5 can promote glycolysis, thereby inhibiting ferroptosis and promoting the stemness of NSCLC, causing tumor metastasis and adverse prognosis in patients. In terms of mechanism, SETD5 as H3K36me3 facilitates the m6A modification of METTL14 and the recruitment of YTHDF1 and mediates PKM2 nuclear translocation and phosphorylation of p-PKM2 Tyr105, regulating GPX4 mediated ferroptosis resistance and SOX9 mediated stemness in NSCLC. The findings emphasize that SETD5 may serve as a promising indicator of stemness in NSCLC, which can help develop therapeutic targets for NSCLC and prognostic evaluation. This study provides evidence that SETD5 as H3K36me3 facilitates the m6A modification of METTL14 and the recruitment of YTHDF1 and mediates the nuclear translocation of PKM2, regulating GPX4 mediated ferroptosis resistance and SOX9 mediated stemness, causing tumor metastasis and adverse prognosis in patients.

Primordial germ cells (PGCs), the precursors of oocytes or spermatozoa, are highly pluripotent. In recent years, the in vitro induction of human primordial germ cell-like cells (hPGCLCs) has advanced significantly. However, the stability and efficacy of obtaining hPGCLCs in vitro still require further improvement. In the current study, we identified a novel induction system by using Dulbecco's Modified Eagle Medium/Nutrient Mixture F-12 (DMEM/F-12) as the basal medium supplemented with B27 and N2 (referred to as N2B27) in combination with four cytokines: bone morphogenetic protein 4 (BMP4), stem cell factor (SCF), epidermal growth factor (EGF), and leukemia inhibitory factor (LIF). The hPGCLCs induced under these conditions closely resemble PGCs from 4 to 5-week-old embryos at the transcriptome level. Compared with traditional GK15 (GMEM supplemented with 15% Knockout™ SR)-based induction conditions, the N2B27 system significantly increased the speed and efficacy of hPGCLC induction. RNA sequencing analysis revealed that this improvement resulted from an increased cell capacity to cope with hypoxic stress and avoid apoptosis. The N2B27 medium promoted an increase in mitochondrial activity, enabling cells to better cope with hypoxic stress while also reducing the production of reactive oxygen species. Moreover, by gradient concentration experiments, we demonstrated that addition of the common antioxidant N-acetyl-L-cysteine at an optimized concentration further enhanced the efficiency of PGCLC induction under GK15 conditions. Thus, our study established an optimized induction system that enhances the efficiency of hPGCLC differentiation by improving cellular resilience to hypoxic stress and apoptosis.

Embryonic development is a complex process of concurrent events comprising cell proliferation, differentiation, morphogenesis, migration, and tissue remodeling. To cope with the demands arising from these developmental processes, cells increase their nutrient uptake, which subsequently increases their metabolic activity. Mitochondria play a key role in the maintenance of metabolism and production of reactive oxygen species (ROS) as a natural byproduct. Regulation of ROS by antioxidants is critical and tightly regulated during embryonic development, as dysregulation results in oxidative stress that damages essential cellular components such as DNA, proteins, and lipids, which are crucial for cellular maintenance and in extension development. However, during development, exposure to certain exogenous factors or damage to cellular components can result in an imbalance between ROS production and its neutralization by antioxidants, leading to detrimental effects on the developmental process. In this review article, we highlight the crucial role of redox homeostasis in normal development and how disruptions in redox balance may result in developmental defects.

Dissolved oxygen is crucial for metabolism, growth, and other complex physiological and pathological processes; however, standard physiological models (such as organ-on-chip systems) often use ambient oxygen levels, which do not reflect the lower levels that are typically found in vivo. Additionally, the local generation of reactive oxygen species (ROS; a key factor in physiological systems) is often overlooked in biology-mimicking models. Here, we present a microfluidic system that integrates electrochemical dissolved oxygen sensors with lab-on-a-chip technology to monitor the physiological oxygen concentrations and generate hydrogen peroxide (H2O2; a specific ROS). This microfluidic lab-on-a-chip system was fabricated using high-resolution 3D printing technology in a one-step process. It incorporates a micromixer, an on-chip bubble-trap, an electrochemical cell with fabricated gold or platinum black-coated working electrodes as well as an Ag/AgCl reference electrode, and a commercial optical oxygen sensor for validation. This device enables an automated variation of the oxygen levels as well as sensitive electrochemical oxygen monitoring (limit of detection = 11.9 ± 0.3 μM), with a statistically significant correlation with the optical sensor. The proposed system can serve as a tool to characterize and evaluate custom-made electrodes. Indeed, we envision that in the future it will be used to regulate dissolved oxygen levels and oxygen species in real time in organ-on-chip systems.

Cancer is a heterogeneous disease, which contributes to its rapid progression and therapeutic failure. Besides interpatient tumor heterogeneity, tumors within a single patient can present with a heterogeneous mix of genetically and phenotypically distinct subclones. These unique subclones can significantly impact the traits of cancer. With the plasticity that intratumoral heterogeneity provides, cancers can easily adapt to changes in their microenvironment and therapeutic exposure. Indeed, tumor cells dynamically shift between a more differentiated, rapidly proliferating state with limited tumorigenic potential and a cancer stem cell (CSC)-like state that resembles undifferentiated cellular precursors and is associated with high tumorigenicity. In this context, CSCs are functionally located at the apex of the tumor hierarchy, contributing to the initiation, maintenance, and progression of tumors, as they also represent the subpopulation of tumor cells most resistant to conventional anti-cancer therapies. Although the CSC model is well established, it is constantly evolving and being reshaped by advancing knowledge on the roles of CSCs in different cancer types. Here, we review the current evidence of how CSCs play a pivotal role in providing the many traits of aggressive tumors while simultaneously evading immunosurveillance and anti-cancer therapy in several cancer types. We discuss the key traits and characteristics of CSCs to provide updated insights into CSC biology and highlight its implications for therapeutic development and improved treatment of aggressive cancers.

Vascular pathologies and injuries are important factors for the delayed wound healing in diabetes. Previous studies have demonstrated that hypoxic environments could induce formation of new blood vessels by regulating intercellular communication and cellular behaviors. In this study, we have enhanced the angiogenic potential of exosomes by subjecting urine-derived stem cells (USCs) to hypoxic preconditioning. To prolong the retention of exosomes at the wound site, we have also engineered a novel dECM hydrogel termed SISMA, which was modified from porcine small intestinal submucosa (SIS). For its rapid and controllable gelation kinetics, excellent biocompatibility, and exosome release capability, the SISMA hydrogel has proven to be a reliable delivery vehicle for exosomes. The hypoxia-induced exosomes-loaded hydrogel has promoted endothelial cell proliferation, migration, and tube formation. More importantly, as evidenced by significant in vivo vascular regeneration in the early stages post-injury, it has facilitated tissue repair. This may because miR-486-5p in H-exo inhibit SERPINE1 activity in endothelial cell. Additionally, miRNA sequencing analysis suggested that the underlying mechanism for enhanced angiogenesis may be associated with the activation of classical HIF-1α signaling pathway. In summary, our study has presented a novel non-invasive, cell-free therapeutic approach for accelerating diabetes wound healing and development of a practical and efficient exosomes delivery platform.

Cell migration of mesenchymal stem cells (MSCs) is critical for bone healing and remodeling. Cobalt is a well-known hypoxia mimic, which can enhance MSC migration. Therefore, the objective of this study was to investigate the migratory response of MSCs to a developed cobalt-incorporated hydroxyapatite (HACo) material. HACo was fabricated by a simple ion exchange procedure at concentrations ranging from 40 to 8000 μM into disc shape. HACo discs were incubated in the media and conditioned media (CM; HACoCM) were collected for MSC culture. HACM served as a control. MSCs were cultured until reaching 90% confluence before the wound was generated by scraping. Time-lapse imaging of wound migration was monitored, recorded, and assessed. Statistical analysis was performed by one-way ANOVA followed by a Dunnett's test. The wound area gradually declined from 0 to 40 h for all samples. HACoCM at 40 µM (HACo40CM) promoted wound closure at the early period of wound healing. Both HACo40CM and HACo8000CM enhanced the distance and velocity of individual cell migration. However, only HACo40CM affected cell persistence and direction at the early period of cell migration. Exposure to HACoCM accelerated the speed of MSC migration, which is necessary for wound healing. The migratory ability of individual cells could help the rate of wound healing. Therefore, HACo materials may serve as potential biomaterials for enhanced bone healing.

A large body of evidence suggests that hypoxia drives aggressive molecular features of malignant cells irrespective of cancer type. Non-Hodgkin lymphomas (NHL) are the most common hematologic malignancies characterized by frequent involvement of diverse hypoxic microenvironments. We studied the impact of long-term deep hypoxia (1% O2) on the biology of lymphoma cells. Only 2 out of 6 tested cell lines (Ramos, and HBL2) survived ≥ 4 weeks under hypoxia. The hypoxia-adapted (HA)b Ramos and HBL2 cells had a decreased proliferation rate accompanied by significant suppression of both oxidative phosphorylation and glycolytic pathways. Transcriptome and proteome analyses revealed marked downregulation of genes and proteins of the mitochondrial respiration complexes I and IV, and mitochondrial ribosomal proteins. Despite the observed suppression of glycolysis, the proteome analysis of both HA cell lines showed upregulation of several proteins involved in the regulation of glucose utilization including the active catalytic component of prolyl-4-hydroxylase P4HA1, an important druggable oncogene. HA cell lines demonstrated increased transcription of key regulators of auto-/mitophagy, e.g., neuritin, BCL2 interacting protein 3 (BNIP3), BNIP3-like protein, and BNIP3 pseudogene. Adaptation to hypoxia was further associated with deregulation of apoptosis, namely upregulation of BCL2L1/BCL-XL, overexpression of BCL2L11/BIM, increased binding of BIM to BCL-XL, and significantly increased sensitivity of both HA cell lines to A1155463, a BCL-XL inhibitor. Finally, in both HA cell lines AKT kinase was hyperphosphorylated and the cells showed increased sensitivity to copanlisib, a pan-PI3K inhibitor. In conclusion, our data report on several shared mechanisms of lymphoma cell adaptation to long-term hypoxia including: 1. Upregulation of proteins responsible for glucose utilization, 2. Degradation of mitochondrial proteins for potential mitochondrial recycling (by mitophagy), and 3. Increased dependence on BCL-XL and PI3K-AKT signaling for survival. In translation, inhibition of glycolysis, BCL-XL, or PI3K-AKT cascade may result in targeted elimination of HA lymphoma cells.

Tumor hypoxia drives metabolic shifts, cancer progression, and therapeutic resistance. Challenges in quantifying hypoxia have hindered the exploitation of this potential "Achilles' heel." While gene expression signatures have shown promise as surrogate measures of hypoxia, signature usage is heterogeneous and debated. Here, we present a systematic pan-cancer evaluation of 70 hypoxia signatures and 14 summary scores in 104 cell lines and 5,407 tumor samples using 472 million length-matched random gene signatures. Signature and score choice strongly influenced the prediction of hypoxia in vitro and in vivo. In cell lines, the Tardon signature was highly accurate in both bulk and single-cell data (94% accuracy, interquartile mean). In tumors, the Buffa and Ragnum signatures demonstrated superior performance, with Buffa/mean and Ragnum/interquartile mean emerging as the most promising for prospective clinical trials. This work delivers recommendations for experimental hypoxia detection and patient stratification for hypoxia-targeting therapies, alongside a generalizable framework for signature evaluation.

Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) are increasingly recognized for their therapeutic potential in regenerative medicine, driven by their capabilities in immunomodulation and tissue repair. However, MSCs present risks such as immunogenic responses, malignant transformation, and the potential to transmit infectious pathogens due to their intrinsic proliferative and differentiative abilities. In contrast, MSC-EVs, particularly exosomes (MSC-exosomes, 30-150 nm in diameter), offer a safer therapeutic profile. These acellular vesicles mitigate risks associated with immune rejection and tumorigenesis and are inherently incapable of forming ectopic tissues, thereby enhancing their clinical safety and applicability. This review highlights the therapeutic promise of MSC-exosomes especially focusing on the modulation of miRNA (one of bioactive molecules in MSC-EVs) profiles through various preconditioning strategies such as exposure to hypoxia, chemotherapeutic agents, inflammatory cytokines, and physical stimuli. Such conditioning is shown to optimize their therapeutic potential. Key miRNAs including miR-21, miR-146, miR-125a, miR-126, and miR-181a are particularly noted for their roles in facilitating tissue repair and modulating inflammatory responses. These functionalities position MSC-exosomes as a valuable tool in personalized medicine, particularly in the case of exosome-based interventions. Despite the potential of MSC-EVs, this review also acknowledged the limitations of traditional MSC therapies and advocates for a strategic pivot towards exosome-based modalities to enhance therapeutic outcomes. By discussing recent advances in detail and identifying remaining pitfalls, this review aims to guide future directions in improving the efficacy of MSC-exosome-based therapeutics. Additionally, miRNA variability in MSC-EVs presents challenges due to the diverse roles of miRNAs play in regulating gene expression and cell behavior. The miRNA content of MSC-EVs can be influenced by preconditioning strategies and differences in isolation and purification methods, which may alter the expression profiles of specific miRNAs, contributing to differences in their therapeutic effects.

Premature ovarian insufficiency (POI) is an ovarian dysfunction disorder that significantly impacts female fertility. Ovarian granulosa cells (GCs) are crucial somatic components supporting oocyte development that rely on glycolysis for energy production, which is essential for follicular growth. Hypoxia-induced exosomal circRNAs regulate glycolysis, but their biological functions and molecular mechanisms in POI are largely unexplored. The present comprehensive investigation revealed a substantial reduction in ovarian glycolysis levels in POI rats. Notably, hypoxia-induced exosomes originating from mesenchymal stem cells (HM-Exs) exhibit a remarkable capacity to enhance ovarian glycolysis, mitigate GCs apoptosis, reinstate disrupted estrous cycles, modulate sex hormone levels, and curtail the presence of atretic follicles. These restorative actions collectively contribute to fostering fertility revival in POI-afflicted rats.

Cyclophosphamide was administered for 2 weeks to induce POI rat model, and POI rats were randomly divided into three groups and treated with PBS, NM-Exs and HM-Exs, respectively. Ovarian function and fertility were assessed at the end of the study and ovarian tissues were collected for analysis of energy metabolites. The relationship between circDennd2a and POI was explored in vitro by qRT-PCR, Western blotting, CCK-8 assay, EdU staining, TUNEL staining, extracellular acidification rate (ECAR) measurements, and ATP, lactate and pyruvate level assays.

Our findings revealed depletion of circDennd2a in serum samples and GCs from individuals suffering from POI. The introduction of HM-Exs-derived circDennd2a (HM-Exs-circDennd2a) effectively counteracted GCs apoptosis by enhancing glycolytic processes and driving cellular proliferation. CircDennd2a interacted with lactate dehydrogenase A (LDHA), which served as a catalyst to increase LDHA enzymatic activity and facilitate the conversion of NADH to NAD+. This biochemical cascade worked synergistically to sustain glycolytic function within GCs.

This study revealed that HM-Exs-circDennd2a promoted LDHA activity and enhanced GCs glycolytic capacity, both of which support its use as a potential clinical diagnostic and therapeutic target for POI.

This study aimed to explore the role and mechanism of hypoxic environment in rat bone mesenchymal stem cells (rBMSCs) proliferation, osteogenic differentiation and angiogenesis.

Cell proliferation, angiogenesis and osteogenic differentiation were assessed using the CCK-8 assay, tube formation assay and alizarin red staining, respectively. Transcriptomic databases for rBMSCs under hypoxic (1 % O2) and normoxic (18 % O2) conditions were constructed to identify differentially expressed genes (DEGs), which were then subjected to gene function annotation and KEGG pathway analysis. To modulate the expression of Itga11, siRNA targeting Itga11 (si-Itga11) and a negative control (si-con), as well as pcDNA-Itga11 and an empty control plasmid (pcDNA), were employed to induce silencing or overexpression of Itga11. The protein levels were evaluated using Western blot analysis.

Hypoxia stimulated the proliferation and angiogenesis of rBMSCs but suppressed their osteogenic differentiation. Differential expression analysis identified 541 upregulated and 277 downregulated genes in the hypoxic group compared to the normoxic group. KEGG pathway enrichment analysis suggested that the hypoxic response in rBMSCs is closely associated with the Pi3k /Akt signaling pathway. Itga11 was significantly downregulated in rBMSCs under hypoxic conditions. Overexpression of Itga11 in rBMSCs inhibited their proliferation and angiogenesis and enhanced osteogenic differentiation, while its knockdown had the opposite effect. Itga11 was found to activate the Pi3k /Akt signaling pathway in rBMSCs.

Itga11 facilitates osteogenic differentiation and suppresses angiogenesis and proliferation of MSCs under hypoxia by activating the Pi3k /Akt signaling pathway.

The SARS-CoV-2 pandemic has resulted in 762 million infections worldwide from 2020 to date, of which approximately ten percent are suffering from the effects after infection in 2019 (COVID-19) [1, 40]. In Germany, it is now assumed that at least one million people suffer from post-COVID condition with long-term consequences. These have been previously reported in diseases like Myalgic Encephalomyelitis (ME) and Chronic Fatigue Syndrome (CFS). Symptoms show a changing variability and recent surveys in the COVID context indicate that 10-30 % of outpatients, 50 to 70% of hospitalised patients suffer from sequelae. Recent data suggest that only 13% of all ill people were completely free of symptoms after recovery [3, 9]. Current hypotheses consider chronic inflammation, mitochondrial dysfunction, latent viral persistence, autoimmunity, changes of the human microbiome or multilocular sequelae in various organ system after infection. Hyperbaric oxygen therapy (HBOT) is applied since 1957 for heart surgery, scuba dive accidents, CO intoxication, air embolisms and infections with anaerobic pathogens. Under hyperbaric pressure, oxygen is physically dissolved in the blood in higher concentrations and reaches levels four times higher than under normobaric oxygen application. Moreover, the alternation of hyperoxia and normoxia induces a variety of processes at the cellular level, which improves oxygen supply in areas of locoregional hypoxia. Numerous target gene effects on new vessel formation, anti-inflammatory and anti-oedematous effects have been demonstrated [74]. The provision of intermittently high, local oxygen concentrations increases repair and regeneration processes and normalises the predominance of hyperinflammation. At present time only one prospective, randomized and placebo-controlled study exists with positive effects on global cognitive function, attention and executive function, psychiatric symptoms and pain interference. In conclusion, up to this date HBO is the only scientifically proven treatment in a prospective randomized controlled trial to be effective for cognitive improvement, regeneration of brain network and improvement of cardiac function. HBOT may have not only theoretical but also potential impact on targets of current pathophysiology of Post COVID condition, which warrants further scientific studies in patients.

Radiotherapy is a cornerstone in the treatment of various tumors, yet radioresistance often leads to treatment failure and tumor recurrence. Several factors contribute to this resistance, including hypoxia, DNA repair mechanisms, and cancer stem cells. This review explores the diverse elements that drive tumor radiotherapy resistance. Historically, resistance has been attributed to cellular repair and tumor repopulation, but recent research has expanded this understanding. The tumor microenvironment - characterized by hypoxia, immune evasion, and stromal interactions - further complicates treatment. Additionally, molecular mechanisms such as aberrant signaling pathways, epigenetic modifications, and non-B-DNA structures play significant roles in mediating resistance. This review synthesizes current knowledge, highlighting the interplay of these factors and their clinical implications. Understanding these mechanisms is crucial for developing strategies to overcome resistance and improve therapeutic outcomes in cancer patients.

To mimic physiological microenvironments in organ-on-a-chip systems, physiologically relevant parameters are required to precisely access drug metabolism. Oxygen level is a critical microenvironmental parameter to maintain cellular or tissue functions and modulate their behaviors. Current organ-on-a-chip setups are oftentimes subjected to the ambient incubator oxygen level at 21%, which is higher than most if not all physiological oxygen concentrations. Additionally, the physiological oxygen level in each tissue is different ranging from 0.5 to 13%. Here, a closed-loop modular multiorgan-on-chips platform is developed to enable not only real-time monitoring of the oxygen levels but, more importantly, tight control of them in the range of 4 to 20% across each connected microtissue-on-a-chip in the circulatory culture medium. This platform, which consists of microfluidic oxygen scavenger(s), an oxygen generator, a monitoring/controller system, and bioreactor(s), allows for independent, precise upregulation and downregulation of dissolved oxygen in the perfused culture medium to meet the physiological oxygen level in each modular microtissue compartment, as needed. Furthermore, drug studies using the platform demonstrate that the oxygen level affects drug metabolism in the parallelly connected liver, kidney, and arterial vessel microtissues without organ-organ interactions factored in. Overall, this platform can promote the performances of organ-on-a-chip devices in drug screening by providing more physiologically relevant and independently adjustable oxygen microenvironments for desired organ types on a single- or a multiorgan-on-chip(s) configuration.

Human organoids have been proposed to be powerful tools mimicking the physiopathological processes of the organs of origin. Recently, human pancreatic organoids (hPOs) have gained increasing attention due to potential theragnostic and regenerative medicine applications. However, the cellular components of hPOs have not been defined precisely. In this work, we finely characterized these structures, focusing first on morphology and identity-defining molecular features under long-term culture conditions. Next, we focused our attention on hPOs cell type composition using single-cell RNA sequencing founding a complex heterogeneity in ductal components, ranging from progenitor components to terminally differentiated ducts. Furthermore, an extensive comparison of human pancreatic organoids with previously reported transcriptomics signature of human and mouse pancreatic ductal populations, confirmed the functional pancreatic duct subpopulation heterogeneity. Finally, we showed that pancreatic organoid cells follow a precise developmental trajectory and utilize diverse signalling mechanisms, including EGF and SPP1, to facilitate cell-cell communication and maturation. Together our results offer an in-depth description of human pancreatic organoids providing a strong foundation for future in vitro diagnostic and translational studies of pancreatic health and disease.

Impaired tissue regeneration negatively impacts on left ventricular (LV) function and remodeling after acute myocardial infarction (AMI). Little is known about the intrinsic regulatory machinery of ischemia-induced endogenous cardiac stem cells (eCSCs) self-renewing divisions after AMI. The interleukin 22 (IL-22)/IL-22 receptor 1 (IL-22R1) pathway has emerged as an important regulator of several cellular processes, including the self-renewal and proliferation of stem cells. However, whether the hypoxic environment could trigger the self-renewal of eCSCs via IL-22/IL-22R1 activation remains unknown. In this study, the upregulation of IL-22R1 occurred due to activation of hypoxia-inducible factor-1α (HIF-1α) under hypoxic and ischemic conditions. Systemic IL-22 administration not only attenuated cardiac remodeling, inflammatory responses, but also promoted eCSC-mediated cardiac repair after AMI. Unbiased RNA microarray analysis showed that the downstream mediator Bmi1 regulated the activation of CSCs. Therefore, the HIF-1α-induced IL-22/IL-22R1/Bmi1 cascade can modulate the proliferation and activation of eCSCs in vitro and in vivo. Collectively, investigating the HIF-1α-activated IL-22/IL-22R1/Bmi1 signaling pathway might offer a new therapeutic strategy for AMI via eCSC-induced cardiac repair.

Chronic prostate inflammation in patients with benign prostate hyperplasia (BPH) correlates with the severity of symptoms. How inflammation contributes to prostate enlargement and/or BPH symptoms and the underlying mechanisms remain unclear. In this study, we utilize a unique transgenic mouse model that mimics chronic non-bacterial prostatitis in men and investigate the impact of inflammation on androgen receptor (AR) in basal prostate stem cells (bPSC) and their differentiation in vivo. We find that inflammation significantly enhances AR levels and activity in bPSC. More importantly, we identify interleukin 1 receptor antagonist (IL-1RA) as a crucial regulator of AR in bPSC during inflammation. IL-1RA is one of the top molecules upregulated by inflammation, and inhibiting IL-1RA reverses the enhanced AR activity in organoids derived from inflamed bPSC. Additionally, IL-1RA appears to activate AR by counteracting IL-1α's inhibitory effect. Furthermore, using a lineage tracing model, we observe that inflammation induces bPSC proliferation and differentiation into luminal cells even under castrate conditions, indicating that AR activation driven by inflammation is sufficient to promote bPSC proliferation and differentiation. Taken together, our study uncovers mechanisms through which inflammation modulates AR signaling in bPSC and induces bPSC luminal differentiation that may contribute to prostate hyperplasia.

Osteoarthritis (OA) induced microenvironmental alterations are a common and unavoidable phenomenon that greatly exacerbate the pathologic process of OA. Imbalances in the synthesis and degradation of cartilage extracellular matrix (ECM) have been reported to be associated with an adverse microenvironment. Stem cell therapy is a promising treatment for OA, and mesenchymal stem cells (MSCs) are the main cell sources for this therapy. With multispectral differentiation and immunomodulation, MSCs can effectively regulate the microenvironment of articular cartilage, ameliorate inflammation, promote regeneration of damaged cartilage, and ultimately alleviate OA symptoms. However, the efficacy of MSCs in the treatment of OA is greatly influenced by articular cavity microenvironments. This article reviews the five microenvironments of OA articular cavity, including inflammatory microenvironment, senescence microenvironment, hypoxic microenvironment, high glucose microenvironment and high lipid environment, focus on the positive and negative effects of OA microenvironments on the fate of MSCs. In this regard, we emphasize the mechanisms of the current use of MSCs in OA treatment, as well as its limitations and challenges.

The significance of hypoxia at the maternal-fetal interface is proven to be self-explanatory in the context of pregnancy. During the first trimester, low oxygen conditions play a crucial role in processes such as angiogenesis, trophoblast invasion and differentiation, and immune regulation. Recently, there has been increasing research on decidual macrophages, which contribute to the maintenance of immune tolerance, placental and fetal vascular development, and spiral artery remodeling, to investigate the effects of hypoxia on their biological behaviors. On these grounds, this review describes the dynamic changes in oxygen levels at the maternal-fetal interface throughout gestation, summarizing current knowledge on how the hypoxic environment sustains a successful pregnancy by regulating retention, differentiation and efferocytosis of decidual macrophages. Additionally, we explore the relationship between spontaneous miscarriages and an abnormal hypoxia-macrophage axis, shedding light on the underlying mechanisms. However, further studies are essential to elucidate these pathways in greater detail and to develop targeted interventions that could improve pregnancy outcomes.

The existence of neural stem cells (NSCs) in the adult mammalian nervous system, although small in number and restricted to the sub-ventricular zone of the lateral ventricles, the dentate gyrus of the hippocampus, and the olfactory epithelium, is a gift of evolution for the adaptive brain function which requires persistent plastic changes of these regions. It is known that most adult NSCs are latent, showing long cell cycles. In the past decade, the concept of quiescent NSCs (qNSCs) has been widely accepted by researchers in the field, and great progress has been made in the biology of qNSCs. Although the spontaneous neuronal regeneration derived from adult NSCs is not significant, understanding how the behaviors of qNSCs are regulated sheds light on stimulating endogenous NSC-based neuronal regeneration. In this review, we mainly focus on the recent progress of the developmental origin and regulatory mechanisms that maintain qNSCs under normal conditions, and that mobilize qNSCs under pathological conditions, hoping to give some insights for future study.

The skin is made up of different layers with various gradients, which maintain a complex microenvironment, particularly in terms of oxygen levels. However, all types of skin cells are cultured in conventional incubators that do not reproduce physiological oxygen levels. Instead, they are cultured at atmospheric oxygen levels, a condition that is far removed from physiology and may lead to the generation of free radicals known to induce skin ageing. This review aims to summarize the current literature on the effect of physiological oxygen levels on skin cells, highlight the shortcomings of current in vitro models, and demonstrate the importance of respecting skin oxygen levels. We begin by clarifying the terminology used about oxygen levels and describe the specific distribution of oxygen in the skin. We review and discuss how skin cells adapt their oxygen consumption and metabolism to oxygen levels environment, as well as the changes that are induced, particularly, their redox state, life cycle and functions. We examine the effects of oxygen on both simple culture models and more complex reconstructed skin models. Finally, we present the implications of oxygen modulation for a more therapeutic approach.

Stem cells are crucial in tissue engineering, and their microenvironment greatly influences their behavior. Among the various dental stem cell types, stem cells from the apical papilla (SCAPs) have shown great potential for regenerating the pulp-dentin complex. Microenvironmental cues that affect SCAPs include physical and biochemical factors. To research optimal pulp-dentin complex regeneration, researchers have developed several models of controlled biomimetic microenvironments, ranging from in vivo animal models to in vitro models, including two-dimensional cultures and three-dimensional devices. Among these models, the most powerful tool is a microfluidic microdevice, a tooth-on-a-chip with high spatial resolution of microstructures and precise microenvironment control. In this review, we start with the SCAP microenvironment in the regeneration of pulp-dentin complexes and discuss research models and studies related to the biological process.

Cancer stem cells (CSCs) drive malignant tumor progression, recurrence, and metastasis with unique characteristics, including self-renewal and resistance to conventional treatments. Conventional differentiation inducers, although promising, have limited cytotoxicity and may inadvertently enhance CSC stemness. To address these challenges, ongoing efforts are dedicated to developing strategies that can effectively combine both cytotoxicity and differentiation-inducing effects. In this study, we introduce oridonin (Ori), a small molecule with dual differentiation-inducing and cytotoxicity properties capable of eliminating tumor CSCs. We isolated CSCs in B16F10 cells using the Hoechst side population method and assessed the differentiation effect of Ori. Ori's differentiation-inducing effect was further evaluated using human acute promyelocytic leukemia. The cytotoxic potential of Ori against MCF-7 and B16F10 cell lines was assessed through various methods. In vivo anti-tumor and anti-CSC efficacy of Ori was investigated using mouse melanoma and CSCs melanoma models. Safety evaluation included zebrafish embryotoxicity and mouse acute toxicity experiments. As a result, Ori effectively dismantles tumorspheres, inhibits proliferation, and reduces the expression of CSC-specific markers. It induces significant differentiation, especially in the case of NB4. Additionally, Ori upregulates TP53 expression, mitigates the hypoxic tumor microenvironment, suppresses stemness, and inhibits PD-L1 expression, prompting a robust anti-cancer immune response. Ori demonstrates pronounced cytotoxicity, inducing notable pro-apoptotic effects on B16F10 and MCF-7 cells, with specific triggering of mitochondrial apoptosis. Importantly, Ori maintains a commendable biosafety record. The dual-action prowess of Ori not only induces the differentiation of CSCs but also dispatches differentiated and residual tumor cells, effectively thwarting the relentless march of tumor progression.

Oxygen played a pivotal role in the evolution of multicellularity during the Cambrian Explosion. Not surprisingly, responses to fluctuating oxygen concentrations are integral to the evolution of cancer-a disease characterized by the breakdown of multicellularity. Poorly organized tumor vasculature results in chaotic patterns of blood flow characterized by large spatial and temporal variations in intra-tumoral oxygen concentrations. Hypoxia-inducible growth factor (HIF-1) plays a pivotal role in enabling cells to adapt, metabolize, and proliferate in low oxygen conditions. HIF-1 is often constitutively activated in cancers, underscoring its importance in cancer progression. Here, we argue that the phenotypic changes mediated by HIF-1, in addition to adapting the cancer cells to their local environment, also "pre-adapt" them for proliferation at distant, metastatic sites. HIF-1-mediated adaptations include a metabolic shift towards anaerobic respiration or glycolysis, activation of cell survival mechanisms like phenotypic plasticity and epigenetic reprogramming, and formation of tumor vasculature through angiogenesis. Hypoxia induced epigenetic reprogramming can trigger epithelial to mesenchymal transition in cancer cells-the first step in the metastatic cascade. Highly glycolytic cells facilitate local invasion by acidifying the tumor microenvironment. New blood vessels, formed due to angiogenesis, provide cancer cells a conduit to the circulatory system. Moreover, survival mechanisms acquired by cancer cells in the primary site allow them to remodel tissue at the metastatic site generating tumor promoting microenvironment. Thus, hypoxia in the primary tumor promoted adaptations conducive to all stages of the metastatic cascade from the initial escape entry into a blood vessel, intravascular survival, extravasation into distant tissues, and establishment of secondary tumors.

Breast cancer stands as the most prevalent malignancy among women, with radiotherapy serving as a primary treatment modality. Despite radiotherapy, a subset of breast cancer patients experiences local recurrence, attributed to the intrinsic resistance of tumors to radiation. Therefore, there is a compelling need to explore novel approaches that can enhance cytotoxic effects through alternative mechanisms. Traditional Chinese Medicine (TCM) and its active constituents exhibit diverse pharmacological actions, including anti-tumor effects, offering extensive possibilities to identify effective components capable of overcoming radiotherapy resistance. This review delineates the mechanisms underlying radiotherapy resistance in breast cancer, along with potential candidate Chinese herbal medicines that may sensitize breast cancer cells to radiotherapy. The exploration of such herbal interventions holds promise for improving therapeutic outcomes in the context of breast cancer radiotherapy resistance.

Germ cells (GCs) serve as indispensable carriers in both animals and plants, ensuring genetic continuity across generations. While it is generally acknowledged that the timing of germline segregation differs significantly between animals and plants, ongoing debates persist as new evidence continues to emerge. In this review, we delve into studies focusing on male germ cell specifications in plants, and we summarize the core gene regulatory circuits in germ cell specification, which show remarkable parallels to those governing meristem homeostasis. The similarity in germline establishment between animals and plants is also discussed.