Iron Homeostasis Determines Fate of Human Pluripotent Stem Cells Via Glycerophospholipids-Epigenetic Circuit

Ferroptosis: a novel strategy to overcome chemoresistance in gynecological malignancies

Ferroptosis is an iron-dependent form of cell death, distinct from apoptosis, necrosis, and autophagy, and is characterized by altered iron homeostasis, reduced defense against oxidative stress, and increased lipid peroxidation. Extensive research has demonstrated that ferroptosis plays a crucial role in the treatment of gynecological malignancies, offering new strategies for cancer prevention and therapy. However, chemotherapy resistance poses an urgent challenge, significantly hindering therapeutic efficacy. Increasing evidence suggests that inducing ferroptosis can reverse tumor resistance to chemotherapy. This article reviews the mechanisms of ferroptosis and discusses its potential in reversing chemotherapy resistance in gynecological cancers. We summarized three critical pathways in regulating ferroptosis: the regulation of glutathione peroxidase 4 (GPX4), iron metabolism, and lipid peroxidation pathways, considering their prospects and challenges as strategies to reverse chemotherapy resistance. These studies provide a fresh perspective for future cancer treatment modalities.

Identification and validation of stemness-based and ferroptosis-related molecular clusters in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with an extremely poor prognosis. Cancer stem cells (CSCs) are considered to be responsible for the poor survival, recurrence and therapy resistance of PDAC. Ferroptosis plays a crucial role in the sustain and survival of CSCs. Here, we employed a rigorous evaluation of multiple datasets to identify a novel stemness-based and ferroptosis-related genes (SFRGs) signature to access the potential prognostic application. This work we retrieved RNA-sequencing and clinical annotation data from the TCGA, ICGC, GTEx and GEO database, and acquired 26 stem cell gene sets and 259 ferroptosis genes from StemChecker database and FerrDb database, respectively. Based on consensus clustering and ssGSEA analysis, we identified two expression patterns of CSCs traits (C1 and C2). Then, WGCNA analysis was implemented to screen out hub module genes correlated with stemness. Furthermore, differential expression analysis, Pearson correlation analysis, and the Least absolute shrinkage and selection operator (LASSO) and Cox regression were performed to identify the SFRGs and to construct model. In addition, the differences in prognosis, tumor microenvironment (TME) components and therapy responses were evaluated between two risk groups. Finally, we verified the most influential marker ARNTL2 experimentally by western blot, qRT-PCR, sphere formation assay, mitoscreen assay, intracellular iron concentration determination and MDA determination assays. In conclusion, we developed a stemness-based and ferroptosis-related prognostic model, which could help predict overall survival for PDAC patients. Targeting ferroptosis may be a promising therapeutic strategy to inhibit PDAC progression by suppressing CSCs.

Iron-responsive element of Divalent metal transporter 1 (Dmt1) controls Notch-mediated cell fates

Notch receptor activation is regulated by the intramembrane protease γ-secretase, which cleaves and liberates the Notch intracellular domain (Nicd) that regulates gene transcription. While γ-secretase cleavage is necessary, we demonstrate it is insufficient for Notch activation and requires vesicular trafficking. Here, we report Divalent metal transporter 1 (Dmt1, Slc11A2) as a novel and essential regulator of Notch signalling. Dmt1-deficient cells are defective in Notch signalling and have perturbed endolysosomal trafficking and function. Dmt1 encodes for two isoforms, with and without an iron response element (ire). We show that isoform-specific silencing of Dmt1-ire and Dmt1+ire has opposite consequences on Notch-dependent cell fates in cell lines and intestinal organoids. Loss of Dmt1-ire suppresses Notch activation and promotes differentiation, whereas loss of Dmt1+ire causes Notch activation and maintains stem-progenitor cell fates. Dmt1 isoform expression correlates with Notch and Wnt signalling in Apc-deficient intestinal organoids and human colorectal cancers. Consistently, Dmt1-ire silencing induces Notch-dependent differentiation in colorectal cancer cells. These data identify Dmt1 isoforms as binary switches controlling Notch cell fate decisions in normal and tumour cells.

Ferroptosis: The functions of Nrf2 in human embryonic stem cells

Human embryonic stem cells (hESCs) have the capacity of self-renewal as well as differentiation towards three germ layer derivatives which makes them as a source of therapeutic application. hESCs are tremendously prone to cell death after dissociation into single cells. Therefore, it technically hinders their applications. Our recent study has revealed that hESCs can be prone to ferroptosis which differs from those in earlier explorations reporting that cellular detachment results in a process cited as anoikis. Ferroptosis occurs via increasing intracellular iron. Therefore, this form of programmed cell death is distinct from other cell deaths in terms of biochemistry, morphology, and genetics. Ferroptosis is found by excessive iron which plays an important part role in reactive oxygen species (ROS) generation through the Fenton reaction as a cofactor. Many genes are related to ferroptosis under the control of nuclear factor erythroid 2-related factor 2 (Nrf2) which is a transcription factor regulating the expression of genes to protect cells from oxidative stress. Nrf2 was demonstrated to take a perilous role in the suppression of ferroptosis by regulating the iron, antioxidant defense enzymes, usage, and restoration of glutathione, thioredoxin, and NADPH. Mitochondrial function is another target of Nrf2 to control cell homeostasis through the modulation of ROS production. In this review, we will give a succinct overview of lipid peroxidation and discuss the major players in the ferroptotic cascade. Additionally, we discussed the important role of the Nrf2 signaling pathway in mediating lipid peroxidation and ferroptosis, with a focus on known Nrf2 target genes that inhibit these processes and their possible role in hESCs.

Distinct accumulation of nanoplastics in human intestinal organoids

Plastic particles, especially nanoplastics, represent an emerging concern of threat to human health, oral uptake is an important pathway for the plastic particles ingestion by human. While their fate and adverse effects in animal gastrointestinal tract are increasingly investigated, knowledge about their uptake and toxicity in human intestine is still limited. Here, by exposing human intestinal organoids to polystyrene nanoplastics (PS-NPs, ~50 nm in size) with concentrations of 10 and 100 μg/mL, we present evidence of their distinct accumulation in various type cells in intestinal organoids, then causing the cell apoptosis and inflammatory response. Our results further revealed that the effective inhibition of PS-NPs accumulation in secretive cells through co-exposure to a clathrin-mediated endocytosis inhibitor (chlorpromazine), and proved the essential role of active endocytosis in the PS-NPs uptaking into enterocyte cells. Our work not only elucidated the potential uptake and toxicity of PS-NPs in human intestinal cells and the underlying mechanism, but also provide a potential therapeutic approach to relieve the toxicity of PS-NPs to human through the endocytosis inhibition.

Monitoring the induction of ferroptosis following dissociation in human embryonic stem cells

Human embryonic stem cells (hESCs) are vulnerable to cell death upon dissociation. Thus, dissociation is an obstacle in culturing, maintaining, and differentiating of hESCs. To date, apoptosis has become the focus of research into the nature of cell death triggered by cellular detachment; it remains baffling whether another form of cell death can occur upon dissociation in hESCs. Here, we demonstrate that iron accumulation and subsequently lipid peroxidation are responsible for dissociation-mediated hESC death. Moreover, we found that a decrease of glutathione peroxidase 4 because of iron accumulation promotes ferroptosis. Inhibition of lipid peroxidation (ferrostatin-1) or chelating iron (deferoxamine) largely suppresses iron accumulation-induced ferroptosis in dissociated hESCs. The results show that P53 mediates the dissociation-induced ferroptosis in hESCs, which is suppressed by pifithrin α. Multiple genes involved in ferroptosis are regulated by the nuclear factor erythroid 2-related factor 2 (Nrf2). In this study, solute carrier family 7 member 11 and glutathione peroxidase 4 are involved in GSH synthesis decreased upon dissociation as a target of Nrf2. In conclusion, our study demonstrates that iron accumulation as a consequence of cytoskeleton disruption appears as a pivotal factor in the initiation of ferroptosis in dissociated hESCs. Nrf2 inhibits ferroptosis via its downstream targets. Our study suggests that the antiferroptotic target might be a good candidate for the maintenance of hESCs.

[Lipid metabolomic analysis in exosomes of osteonecrosis of the femoral head based on ultra performance liquid chromatography-tandem mass spectrometry]

Osteonecrosis of the femoral head (ONFH) can lead to its collapse which requires total hip arthroplasty. Exosomes, which are important for intercellular communication are involved in a series of physiological and pathological processes, and therefore play a unique role in disease diagnosis and treatment. In this study, untargeted metabolomics was used to investigate the metabolic characteristics of lipids in exosomes of femoral head tissue with osteonecrosis and to explain the metabolic changes that occur in the body during this disease. Ultracentrifugation was used to separate and enrich exosomes from femoral head tissue with osteonecrosis. Exosomes were identified using dynamic light scattering (DLS), Western blotting, and transmission electron microscopy (TEM). Gradient elution was performed with ultrapure water and acetonitrile as mobile phases using a Kinetex XB-C18 column (100 mm×2.1 mm, 2.6 μm). The column oven temperature, flow rate of the mobile phase, and duration were 30 ℃, 300 μL/min, and 15 min, respectively. A triple TOF 4600 high resolution mass spectrometry system was used, and the mass scan range of m/z was set at 100 -1000. Other conditions were as follows: sheath gas, 380 kPa; auxiliary gas, 380 kPa; curtain gas, 170 kPa; and atomization temperature, 600 ℃. Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with multivariate statistical analysis was used to identify the lipid metabolic profile of ONFH-derived exosomes. The exosome metabolites were characterized in detail, which enables their identification and provided a reliable method for quality evaluation. After transforming the obtained original data using MarkView software, peak identification, peak alignment, subtraction of solvent peak, impurity peak, noise filtering, and other treatments, a three-dimensional matrix was obtained from the exported data table. Principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) in the SIMCA-P14.1 software were used for multivariate statistical analysis of differentially expressed exosome lipid metabolites. This strategy was validated using lipid metabolites from patients with ONFH and healthy controls. The correlation distribution was shown according to the point dispersion of the PCA score plot, and lipid metabolites from the same disease showed ideal clustering. This result indicates a small difference between the groups. A good clustering effect is also obtained using OPLS-DA, and the statistical model has high reliability. A total of 18 significantly altered lipid metabolites were detected in the exosomes, including acrylolipids, fatty acid esters, glycerides, and their derivatives. The pathway analysis was conducted with MetaboAnalyst (https://www.metaboanalyst.ca/) via database source including the HMDB (http://www.hmdb.ca/) and MMCD (http://mmcd.nmrfam.wisc.edu/) for confirming the impacted metabolic pathways and visualization. Metabolic pathway analysis showed that glycerophospholipid and sphingolipid metabolism were the most significantly altered in exosomes. An imbalance between sphingolipids and glycerophospholipids leads to lipotoxic damage, which is implicated in the pathophysiology of common metabolic diseases. Furthermore, glycerophospholipids are correlated with cell proliferation, differentiation, and apoptosis, and the change in glycerophospholipid ratio can reflect the disturbance in lipid metabolism. The metabolic changes in exosomes may reflect the metabolic changes in ONFH. In this study, lipid metabolomics analysis based on UPLC-MS/MS was used to determine metabolic differences between exosomes extracted from ONFN and femoral neck fracture (FNF). Metabolomic analysis of necrotic femoral head tissue-derived exosomes can help explore the most relevant pathways for assessing the changes in exosome metabolism that affect exosome metabolism in necrotic bone tissue.

ALKBH5-mediated m6A mRNA methylation governs human embryonic stem cell cardiac commitment

N6-methyladenosine (m⁶A), as the most abundant modification of mammalian messenger RNAs, is essential for tissue development and pathogenesis. However, the biological significance of m⁶A methylation in cardiac differentiation and development remains largely unknown. Here, we identify that the downregulation of m⁶A demethylase ALKBH5 is responsible for the increase of m⁶A methylation and cardiomyocyte fate determination of human embryonic stem cells (hESCs) from mesoderm cells (MESs). In contrast, ALKBH5 overexpression remarkably blocks cardiomyocyte differentiation of hESCs. Mechanistically, KDM5B and RBBP5, the components of H3K4 modifying enzyme complexes, are identified as downstream targets for ALKBH5 in cardiac-committed hESCs. Loss of function of ALKBH5 alters the expression of KDM5B and RBBP5 through impairing stability of their mRNAs, which in turn promotes the transcription of GATA4 by enhancing histone H3 Lys4 trimethylation (H3K4me3) at the promoter region of GATA4. Taken together, we reveal a previously unidentified role of m⁶A demethylase ALKBH5 in determining cardiac lineage commitment of hESCs.

Lipidomics reveals perturbations in the liver lipid profile of iron-overloaded mice

Iron overload is an important contributor to disease. The liver, the major site of iron storage in the body, is a key organ impacted by iron overload. While several studies have reported perturbations in liver lipids in iron overload, it is not clear, on a global scale, how individual liver lipid ions are altered. Here, we used lipidomics to study the changes in hepatic lipid ions in iron-overloaded mice. Iron overload was induced by daily intraperitoneal injections of 100 mg/kg body weight iron dextran for 1 week. Iron overload was verified by serum markers of iron status, liver iron quantitation, and Perls stain. Compared with the control group, the serum of iron-overload mice exhibited low levels of urea nitrogen and high-density lipoprotein (HDL), and high concentrations of total bile acid, low-density lipoprotein (LDL), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH), suggestive of liver injury. Moreover, iron overload disrupted liver morphology, induced reactive oxygen species (ROS) production, reduced superoxide dismutase (SOD) activity, caused lipid peroxidation, and led to DNA fragmentation. Iron overload altered the overall composition of lipid ions in the liver, with significant changes in over 100 unique lipid ions. Notably, iron overload selectively increased the overall abundance of glycerolipids and changed the composition of glycerophospholipids and sphingolipids. This study, one of the first to report iron-overload induced lipid alterations on a global lipidomics scale, provides early insight into lipid ions that may be involved in iron overload-induced pathology.

A study using LC-MS/MS-based metabolomics to investigate the effects of iron oxide nanoparticles on rat liver

Iron oxide nanoparticles (IONPs) are widely used in food additives, but their metabolic mechanism in the body is still unclear. In this study, male Sprague-Dawley rats were orally administered with IONPs for 28 days to investigate the adverse effect and metabolic mechanism on liver by the combination of traditional toxicology technology and liquid chromatography tandem-mass spectrometry (LC-MS/MS)-based metabolomics. The results showed that IONPs could increase the concentration of blood glucose and the metabolites in the liver of the control and IONPs-treated group were significantly changed. A total of 32 different metabolites were found, including choline, Phosphatidylcholine (PC), Phosphatidylethanolamine (PE), Phosphatidylserine (PS), etc. Pathway analysis based on KEGG database demonstrated that the glycerophospholipid metabolism pathway would be affected. And the expression of the key enzymes of altered metabolomics pathway was further verified at the transcription level. In short, our study clarified oral exposure to IONPs would induce lipid metabolism disorders in the liver of rats, which provided useful information about their safety and potential risks.

Uncovering the Metabolic and Stress Responses of Human Embryonic Stem Cells to FTH1 Gene Silencing

Embryonic stem cells (ESCs) are pluripotent cells with indefinite self-renewal ability and differentiation properties. To function properly and maintain genomic stability, ESCs need to be endowed with an efficient repair system as well as effective redox homeostasis. In this study, we investigated different aspects involved in ESCs' response to iron accumulation following stable knockdown of the ferritin heavy chain (FTH1) gene, which encodes for a major iron storage protein with ferroxidase activity. Experimental findings highlight unexpected and, to a certain extent, paradoxical results. If on one hand FTH1 silencing does not correlate with increased ROS production nor with changes in the redox status, strengthening the concept that hESCs are extremely resistant and, to a certain extent, even refractory to intracellular iron imbalance, on the other, the differentiation potential of hESCs seems to be affected and apoptosis is observed. Interestingly, we found that FTH1 silencing is accompanied by a significant activation of the nuclear factor (erythroid-derived-2)-like 2 (Nrf2) signaling pathway and pentose phosphate pathway (PPP), which crosstalk in driving hESCs antioxidant cascade events. These findings shed new light on how hESCs perform under oxidative stress, dissecting the molecular mechanisms through which Nrf2, in combination with PPP, counteracts oxidative injury triggered by FTH1 knockdown.

The epigenetic and morphogenetic effects of molecular oxygen and its derived reactive species in development

The development of multicellular organisms involves the unpacking of a complex genetic program. Extensive characterization of discrete developmental steps has revealed the genetic program is controlled by an epigenetic state. Shifting the epigenome is a group of epigenetic enzymes that modify DNA and proteins to regulate cell type specific gene expression. While the role of these modifications in development has been established, the input(s) responsible for electing changes in the epigenetic state remains unknown. Development is also associated with dynamic changes in cellular metabolism, redox, free radical production, and oxygen availability. It has previously been postulated that these changes are causal in development by affecting gene expression. This suggests that oxygen is a morphogenic compound that impacts the removal of epigenetic marks. Likewise, metabolism and reactive oxygen species influence redox signaling through iron and glutathione to limit the availability of key epigenetic cofactors such as α-ketoglutarate, ascorbate, NAD⁺ and S-adenosylmethionine. Given the close relationship between these cofactors and epigenetic marks it seems likely that the two are linked. Here we describe how changing these inputs might affect the epigenetic state during development to drive gene expression. Combined, these cofactors and reactive oxygen species constitute the epigenetic landscape guiding cells along differing developmental paths.

Ascorbic Acid and Iron Supplement Treatment Improves Stem Cell-Mediated Cartilage Regeneration in a Minipig Model

BACKGROUND

The transplantation of mesenchymal stem cells (MSCs) into cartilage defects has led to variable cartilage repair outcomes. Previous in vitro studies have shown that ascorbic acid and reduced iron independently can improve the chondrogenic differentiation of MSCs. However, the combined effect of ascorbic acid and iron supplementation on MSC differentiation has not been investigated.

PURPOSE

To investigate the combined in vivo effects of ascorbic acid and a US Food and Drug Administration (FDA)-approved iron supplement on MSC-mediated cartilage repair in mature Göttingen minipigs.

STUDY DESIGN

Controlled laboratory study.

METHODS

We pretreated bone marrow-derived MSCs with ascorbic acid and the FDA-approved iron supplement ferumoxytol and then transplanted the MSCs into full-thickness cartilage defects in the distal femurs of Göttingen minipigs. Untreated cartilage defects served as negative controls. We evaluated the cartilage repair site with magnetic resonance imaging at 4 and 12 weeks after MSC implantation, followed by histological examination and immunofluorescence staining at 12 weeks.

RESULTS

Ascorbic acid plus iron-pretreated MSCs demonstrated a significantly better MOCART (magnetic resonance observation of cartilage repair tissue) score (73.8 ± 15.5), better macroscopic cartilage regeneration score according to the International Cartilage Repair Society (8.6 ± 2.0), better Pineda score (2.9 ± 0.8), and larger amount of collagen type II (28,469 ± 21,313) compared with untreated controls (41.3 ± 2.5, 1.8 ± 2.9, 12.8 ± 1.9, and 905 ± 1326, respectively). The obtained scores were also better than scores previously reported in the same animal model for MSC implants without ascorbic acid.

CONCLUSION

Pretreatment of MSCs with ascorbic acid and an FDA-approved iron supplement improved the chondrogenesis of MSCs and led to hyaline-like cartilage regeneration in the knee joints of minipigs.

CLINICAL RELEVANCE

Ascorbic acid and iron supplements are immediately clinically applicable. Thus, these results, in principle, could be translated into clinical applications.

MgFe-LDH Nanoparticles: A Promising Leukemia Inhibitory Factor Replacement for Self-Renewal and Pluripotency Maintenance in Cultured Mouse Embryonic Stem Cells

Leukemia inhibitory factor (LIF), an indispensable bioactive protein that sustains self-renewal and pluripotency in stem cells, is vital for mouse embryonic stem cell (mESC) culture. Extensive research is conducted on reliable alternatives for LIF as its clinical application in stable culture and large-scale expansion of ESCs is limited by its instability and high cost. However, few studies have sought to replace LIF with nanoparticles to provide a xeno-free culture condition. MgAl-LDH (layered double hydroxide) nanoparticles can partially replace LIF in maintaining pluripotency of mESCs; however, the requirement and tolerance for aluminum ions in mice are far lesser than those of iron ions. Hence, MgFe-LDH nanoparticles are selected for this study. MgFe-LDH is superior to MgAl-LDH in maintaining self-renewal and pluripotency of mESCs, in the absence of LIF and mouse embryonic fibroblast. Furthermore, combined transcriptomic and proteomic analysis confirms that MgFe-LDH can activate the LIF receptor (LIFR)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B(AKT), LIFR/JAK/janus kinase (JAK)/signal transducer and activator of transcription 3(STAT3), and phospho-signal transducer and activator of transcription 3(p-STAT3)/ten-eleven translocation (TET) signaling pathways, while the extra Fe2+ provided by MgFe-LDH would also enhance TET1/2 abundance thus affecting the TET1/2 regulated pluripotency related marker expression and TET1/2 meditated DNA demethylation. These results suggest that MgFe-LDH nanoparticles can thus be used as an affordable and efficient replacement for LIF in mESC cultivation.

ALKBH5 regulates cardiomyocyte proliferation and heart regeneration by demethylating the mRNA of YTHDF1

N⁶-methyladenosine (m⁶A) RNA modification, a dynamic and reversible process, is essential for tissue development and pathogenesis. However, the potential involvement of m⁶A in the regulation of cardiomyocyte (CM) proliferation and cardiac regeneration remains unclear. In this study, we aimed to investigate the essential role of m⁶A modification in heart regeneration during postnatal and adult injury.

Methods and results: In this study, we identified the downregulation of m⁶A demethylase ALKBH5, an m6A “eraser” that is responsible for increased m⁶A methylation, in the heart after birth. Notably, ALKBH5 knockout mice exhibited decreased cardiac regenerative ability and heart function after neonatal apex resection. Conversely, forced expression of ALKBH5 via adeno-associated virus-9 (AAV9) delivery markedly reduced the infarct size, restored cardiac function and promoted CM proliferation after myocardial infarction in juvenile (7 days old) and adult (8-weeks old) mice. Mechanistically, ALKBH5-mediated m⁶A demethylation improved the mRNA stability of YTH N⁶-methyladenosine RNA-binding protein 1 (YTHDF1), thereby increasing its expression, which consequently promoted the translation of Yes-associated protein (YAP). The modulation of ALKBH5 and YTHDF1 expression in human induced pluripotent stem cell-derived cardiomyocytes consistently yielded similar results.

Conclusion: Taken together, our findings highlight the vital role of the ALKBH5-m⁶A-YTHDF1-YAP axis in the regulation of CMs to re-enter the cell cycle. This finding suggests a novel potential therapeutic strategy for cardiac regeneration.

Role of Iron on Physical and Mechanical Properties of Brushite Cements, and Interaction with Human Dental Pulp Stem Cells

Improving the physical, mechanical and biological properties of brushite cements (BrC) is of a great interest for using them in bone and dental tissue engineering applications. The objective of this study was to incorporate iron (Fe) at different concentrations (0.25, 0.50, and 1.00 wt.%) to BrC and study the role of Fe on phase composition, setting time, compressive strength, and interaction with human dental pulp stem cells (hDPSCs). Results showed that increase in Fe concentration increases the β-tricalcium phosphate (β-TCP)/ dicalcium phosphate dihydrate (DCPD) ratio and prolongs the initial and final setting time due to effective role of Fe on stabilizing the β-TCP crystal structure and retarding its dissolution kinetic, in a dose dependent manner where the highest setting time was recorded for 1.00 wt.% Fe-BrC sample. Addition of low concentrations of Fe (0.25 and 0.50 wt.%) did not have adverse effect on compressive strength and strength was in the range of 5.7-7.05 (±~1.4) MPa; however, presence of 1.00 wt.% Fe decreases the strength of BrC from 7.05 ± 1.57 MPa to 3.12 ± 1.06 MPa. Interaction between the BrCs and hDPSCs was evaluated by cell proliferation assay, scanning electron microscopy, and live/dead staining. Low concentrations of 0.25, and 0.50 wt.% of Fe did not have any adverse effect on cell attachment and proliferation; while significant decrease in cellular activity was evident in BrC samples doped with 1.00 wt. %. Together, these data show that low concentrations of Fe (equal or less than 0.50 wt. %) can be safely added to BrC without any adverse effect on physical, mechanical and biological properties in presence of hDPSCs.

Iron overload inhibits self-renewal of human pluripotent stem cells via DNA damage and generation of reactive oxygen species

Iron overload affects the cell cycle of various cell types, but the effect of iron overload on human pluripotent stem cells has not yet been reported. Here, we show that the proliferation capacities of human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) were significantly inhibited by ferric ammonium citrate (FAC) in a concentration‐dependent manner. In addition, deferoxamine protected hESCs/hiPSCs against FAC‐induced cell‐cycle arrest. However, iron overload did not affect pluripotency in hESCs/hiPSCs. Further, treatment of hiPSCs with FAC resulted in excess reactive oxygen species production and DNA damage. Collectively, our findings provide new insights into the role of iron homeostasis in the maintenance of self‐renewal in human pluripotent stem cells.

Inorganic Biomaterials for Regenerative Medicine

Regenerative medicine leverages the innate potential of the human body to efficiently repair and regenerate damaged tissues using engineered biomaterials. By designing responsive biomaterials with the appropriate biophysical and biochemical characteristics, cellular response can be modulated to direct tissue healing. Recently, inorganic biomaterials have been shown to regulate cellular responses including cell-cell and cell-matrix interactions. Moreover, ions released from these mineral-based biomaterials play a vital role in defining cell identity, as well as driving tissue-specific functions. The intrinsic properties of inorganic biomaterials, such as the release of bioactive ions (e.g., Ca, Mg, Sr, Si, B, Fe, Cu, Zn, Cr, Co, Mo, Mn, Au, Ag, V, Eu, and La), can be leveraged to induce phenotypic changes in cells or modulate the immune microenvironment to direct tissue healing and regeneration. Biophysical characteristics of biomaterials, such as topography, charge, size, electrostatic interactions, and stiffness can be modulated by addition of inorganic micro- and nanoparticles to polymeric networks have also been shown to play an important role in their biological response. In this Review, we discuss the recent emergence of inorganic biomaterials to harness the innate regenerative potential of the body. Specifically, we will discuss various biophysical or biochemical effects of inorganic-based materials in directing cellular response for regenerative medicine applications.

YAP/TEAD3 signal mediates cardiac lineage commitment of human-induced pluripotent stem cells

Cardiomyocytes differentiated from human-induced pluripotent stem cells (hiPSCs) hold great potential for therapy of heart diseases. However, the underlying mechanisms of its cardiac differentiation have not been fully elucidated. Hippo-YAP signal pathway plays important roles in cell differentiation, tissue homeostasis, and organ size. Here, we identify the role of Hippo-YAP signal pathway in determining cardiac differentiation fate of hiPSCs. We found that cardiac differentiation of hiPSCs were significantly inhibited after treatment with verteporfin (a selective and potent YAP inhibitor). During hiPSCs differentiation from mesoderm cells (MESs) into cardiomyocytes, verteporfin treatment caused the cells retained in the earlier cardiovascular progenitor cells (CVPCs) stage. Interestingly, during hiPSCs differentiation from CVPC into cardiomyocytes, verteporfin treatment induced cells dedifferentiation into the earlier CVPC stage. Mechanistically, we found that YAP interacted with transcriptional enhanced associate domain transcription factor 3 (TEAD3) to regulate cardiac differentiation of hiPSCs during the CVPC stage. Consistently, RNAi-based silencing of TEAD3 mimicked the phenotype as the cells treated with verteporfin. Collectively, our study suggests that YAP-TEAD3 signaling is important for cardiomyocyte differentiation of hiPSCs. Our findings provide new insight into the function of Hippo-YAP signal in cardiovascular lineage commitment.