Cadmium sulfate induces apoptosis in planarians.

With rapid socio-economic development, heavy metal pollution in water has become common and affects both environment and human health. Cadmium (Cd) has been recognized as one of the heavy metals which cause acute or chronic toxic effects if ingested. Although its toxicity is undisputed, the underlying molecular mechanisms in vivo are not fully understood. Planarians, a model organism famous for their regenerative prowess, have long been utilized to study the effects of chemical exposure. In this study, we observed apoptosis with TUNEL assay in planarians induced by cadmium sulfate (CdSO4) in a dose-dependent manner. The apoptosis-related genes were detected with quantitative RT-PCR. Significant changes in c-Myc, P53, and BcL-2 were indicated, which may play a partial role in the regulation of the process of apoptosis in the planarians. H&E staining showed that Cd had obvious biological toxicity in the planarians. Here, new insights on metal toxicity mechanisms are provided, contributing to understand how CdSO4 induces the pathological and physiological processes of apoptosis in the living bodies. Meanwhile, planarians are proved to be a freshwater pollution indicator and toxicological research model.

Inhibition of cardiomyocyte differentiation of human induced pluripotent stem cells by Ribavirin: Implication for its cardiac developmental toxicity.

Ribavirin has been proven to be an antiviral treatment, whereas there are still risks of hemolysis and congenital malformation. Abnormal cardiac development contributes to the occurrence and development of many heart diseases. However, there is so far no evidence that ribavirin induces human cardiac developmental toxicity. Herein, we employed the cardiac differentiation model of human induced pluripotent stem cells (hiPSCs) to determine the impact of ribavirin on heart development. Our data showed that ribavirin at clinically high concentrations (5 and 10 µM) significantly inhibited the proliferation and differentiation of hiPSCs from mesoderm to cardiac progenitor cells and cardiac progenitor cells to cardiomyocytes, but not from pluripotent status to mesoderm. Meanwhile, DCFH-DA staining revealed that ribavirin could increase ROS content in the mid-phase of differentiation. In addition, ribavirin treatment (1, 5 and 10 µM) remarkably caused DNA damage which was shown by the increase of γH2AX-positive cells and upregulation of the p53 during the differentiation of hiPSCs from mesoderm to cardiac progenitor cells. Moreover, exposuring to ribavirin (5 and 10 µM) markedly upregulated the expression of lncRNAs Gas5 in both mid-phase and late phase of differentiation and HBL1 in the mid-phase. In conclusion, our results suggest that ribavirin is detrimental in cardiac differentiation of hiPSCs, which may be associated with DNA damage, upregulated p53 and increased Gas5. It may provide the evidence for the rational clinical application of ribavirin.

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.

Targeting LncDACH1 promotes cardiac repair and regeneration after myocardium infarction.

Neonatal mammalian heart maintains a transient regeneration capacity after birth, whereas this regeneration ability gradually loses in the postnatal heart. Thus, the reactivation of cardiomyocyte proliferation is emerging as a key strategy for inducing heart regeneration in adults. We have reported that a highly conserved long noncoding RNA (lncRNA) LncDACH1 was overexpressed in the failing hearts. Here, we found that LncDACH1 was gradually upregulated in the postnatal hearts. Cardiac-specific overexpression of LncDACH1 (TG) in mice suppressed neonatal heart regeneration and worsened cardiac function after apical resection. Conversely, in vivo cardiac conditional knockout of LncDACH1 (CKO) and adenovirus-mediated silencing of endogenous LncDACH1 reactivated cardiomyocyte-proliferative potential and promoted heart regeneration after myocardial infarction (MI) in juvenile and adult mice. Mechanistically, LncDACH1 was found to directly bind to protein phosphatase 1 catalytic subunit alpha (PP1A), and in turn, limit its dephosphorylation activity. Consistently, PP1A siRNA or pharmacological blockers of PP1A abrogated cardiomyocyte mitosis induced by LncDACH1 silencing. Furthermore, LncDACH1 enhanced yes-associated protein 1 (YAP1) phosphorylation and reduced its nuclear translocation by binding PP1A. Verteporfin, a YAP1 inhibitor decreased LncDACH1 silencing-induced cardiomyocyte proliferation. In addition, targeting a conserved fragment of LncDACH1 caused cell cycle re-entry of human iPSC-derived cardiomyocytes. Collectively, LncDACH1 governs heart regeneration in postnatal and ischemic hearts via regulating PP1A/YAP1 signal, which confers a novel therapeutic strategy for ischemic heart diseases.

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.

Arsenic trioxide blocked proliferation and cardiomyocyte differentiation of human induced pluripotent stem cells: Implication in cardiac developmental toxicity.

Arsenic trioxide (ATO) has been recommended as the first-line agent for the treatment of acute promyelocytic leukaemia (APL), due to its substantial anticancer effect. Numerous clinical reports have indicated that ATO is a developmental toxicant which can result in birth defects of human beings. But whether arsenic trioxide can lead to human cardiac developmental toxicity remains largely unknown. So the present study aims to explore the influence and mechanisms of ATO on human cardiac development by using a vitro cardiac differentiation model of human induced pluripotent stem cells (hiPSCs). Here we found that clinically achievable concentrations (0.1, 0.5 and 1 µM) of ATO resulted in a significant inhibition of proliferation during the whole process of cardiac differentiation of hiPSCs. Meanwhile, TUNEL assay revealed that ATO could cause cell apoptosis during cardiac differentiation in a concentration-dependent manner. Consistently, we found that ATO reduced the expressions of mesoderm markers Brachyury and EOMES, cardiac progenitor cell markers GATA-4, MESP-1 and TBX-5, and cardiac specific marker α-actinin in differentiated hiPSCs. Furthermore, ATO treatment had caused DNA damage which was shown in the upregulation of γH2AX, a sensitive marker for DNA double-strand breaks. Taken together, ATO blocked cardiomyocyte differentiation, induced apoptosis and cell growth arrest during cardiac differentiation of hiPSCs, which might be associated with DNA damage.

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

Iron homeostasis is crucial for a variety of biological processes, but the biological role of iron homeostasis in pluripotent stem cells (PSCs) remains largely unknown. The present study aimed to determine whether iron homeostasis is involved in maintaining the pluripotency of human PSCs (hPSCs). We found that the intracellular depletion of iron leads to a rapid downregulation of NANOG and a dramatic decrease in the self-renewal of hPSCs as well as spontaneous and nonspecific differentiation. Moreover, long-term depletion of iron can result in the remarkable cell death of hPSCs via apoptosis and necrosis pathways. Additionally, we found that the depletion of iron increased the activity of lipoprotein-associated phospholipase A2 (LP-PLA2) and the production of lysophosphatidylcholine, thereby suppressing NANOG expression by enhancer of zeste homolog 2-mediated trimethylation of histone H3 lysine 27. Consistently, LP-PLA2 inhibition abrogated iron depletion-induced loss of pluripotency and differentiation. Altogether, the findings of our study demonstrates that iron homeostasis, acting through glycerophospholipid metabolic pathway, is essential for the pluripotency and survival of hPSCs. Stem Cells 2019;37:489-503.

The Long Noncoding RNA CAREL Controls Cardiac Regeneration.

BACKGROUND: Adult mammalian heart loses regeneration ability following ischemic injury due to the loss of cardiomyocyte mitosis. However, the molecular mechanisms underlying the post-mitotic nature of cardiomyocytes remain largely unknown. OBJECTIVES: The purpose of this study was to define the essential role of long noncoding ribonucleic acids (lncRNAs) in heart regeneration during postnatal and adult injury. METHODS: Myh6-driving cardiomyocyte-specific lncRNA-CAREL transgenic mice and adenovirus-mediated in vivo silencing of endogenous CAREL were used in this study. The effect of CAREL on cardiomyocyte replication and heart regeneration after apical resection or myocardial infarction was assessed by detecting mitosis and cytokinesis. RESULTS: An lncRNA CAREL was found significantly up-regulated in cardiomyocytes from neonatal mice (P7) in parallel with loss of regenerative capacity. Cardiac-specific overexpression of CAREL in mice reduced cardiomyocyte division and proliferation and blunted neonatal heart regeneration after injury. Conversely, silencing of CAREL in vivo markedly promoted cardiac regeneration and improved heart functions after myocardial infarction in neonatal and adult mice. CAREL acted as a competing endogenous ribonucleic acid for miR-296 to derepress the expression of Trp53inp1 and Itm2a, the target genes of miR-296. Consistently, overexpression of miR-296 significantly increased cardiomyocyte replication and cardiac regeneration after injury. Decline of cardiac regenerative ability in CAREL transgenic mice was also rescued by miR-296. A short fragment containing the conserved sequence of CAREL reduced the proliferation of human induced pluripotent stem cell-derived cardiomyocytes as the full-length CAREL. CONCLUSIONS: LncRNA CAREL regulates cardiomyocyte proliferation and heart regeneration in postnatal and adult heart after injury by acting as a competing endogenous ribonucleic acid on miR-296 that targets Trp53inp1 and Itm2a.

Pre-Treatment with Melatonin Enhances Therapeutic Efficacy of Cardiac Progenitor Cells for Myocardial Infarction.

BACKGROUND/AIMS: Melatonin possesses many biological activities such as antioxidant and anti-aging. Cardiac progenitor cells (CPCs) have emerged as a promising therapeutic strategy for myocardial infarction (MI). However, the low survival of transplanted CPCs in infarcted myocardium limits the successful use in treating MI. In the present study, we aimed to investigate if melatonin protects against oxidative stress-induced CPCs damage and enhances its therapeutic efficacy for MI. METHODS: TUNEL assay and EdU assay were used to detect the effects of melatonin and miR-98 on H2O2-induced apoptosis and proliferation. MI model was used to evaluate the potential cardioprotective effects of melatonin and miR-98. RESULTS: Melatonin attenuated H2O2-induced the proliferation reduction and apoptosis of c-kit+ CPCs in vitro, and CPCs which pretreated with melatonin significantly improved the functions of post-infarct hearts compared with CPCs alone in vivo. Melatonin was capable to inhibit the increase of miR-98 level by H2O2 in CPCs. The proliferation reduction and apoptosis of CPCs induced by H2O2 was aggravated by miR-98. In vivo, transplantation of CPCs with miR-98 silencing caused the more significant improvement of cardiac functions in MI than CPCs. MiR-98 targets at the signal transducer and activator of the transcription 3 (STAT3), and thus aggravated H2O2-induced the reduction of Bcl-2 protein. CONCLUSIONS: Pre-treatment with melatonin protects c-kit+ CPCs against oxidative stress-induced damage via downregulation of miR-98 and thereby increasing STAT3, representing a potentially new strategy to improve CPC-based therapy for MI.

By Targeting Atg7 MicroRNA-143 Mediates Oxidative Stress-Induced Autophagy of c-Kit+ Mouse Cardiac Progenitor Cells.

Therapeutic efficiency of cardiac progenitor cells (CPCs) transplantation is limited by its low survival and retention in infarcted myocardium. Autophagy plays a critical role in regulating cell death and apoptosis, but the role of microRNAs (miRNAs) in oxidative stress-induced autophagy of CPCs remains unclear. This study aimed to explore if miRNAs mediate autophagy of c-kit+ CPCs. We found that the silencing of miR-143 promoted the autophagy of c-kit+ CPCs in response to H2O2, and the protective effect of miR-143 inhibitor was abrogated by autophagy inhibitor 3-methyladenine (3-MA). Furthermore, autophagy-related gene 7 (Atg7) was identified as the target gene of miR-143 by dual luciferase reporter assays. In vivo, after transfection with miR-143 inhibitor, c-kit+ CPCs from green fluorescent protein transgenic mice were more observed in infarcted mouse hearts. Moreover, transplantation of c-kit+ CPCs with miR-143 inhibitor improved cardiac function after myocardial infarction. Take together, our study demonstrated that miR-143 mediates oxidative stress-induced autophagy to enhance the survival of c-kit+ CPCs by targeting Atg7, which will provide a complementary approach for improving CPC-based heart repair.

Blocking Nox2 improves mesenchymal stem cells therapy in myocardial infarction via antagonizing oxidant and promoting survival.

An increase in reactive oxygen species (ROS) plays a key role in aging and apoptosis in mesenchymal stem cells derived from bone marrow (BMSCs). NADPH oxidase Nox2 serves as an important source of intracellular ROS formation. This study is designed to determine if blocking Nox2 enhances anti-apoptotic and anti-aging ability of BMSCs to oxidant stress, and thus improves therapeutic efficacy in myocardial infarction (MI). Nox2 inhibitor (Acetovanillone) and Nox2 siRNA were used to block Nox2 in BMSCs, and the cell viability, apoptosis, senescence and survival of BMSCs were determined by CCK-8, Edu staining, TUNEL staining, ß-galactosidase (ß-gal) assay and DAPI labeling. Here we found that both Nox2 inhibitor and Nox2 knockdown remarkably countered the decrease of viability, and the increase of aging and apoptosis of BMSCs by H2 O2 . Whereas, Nox2 overexpression exacerbated the viability reduction, senescence and apoptosis of BMSCs. The ROS accumulation in BMSCs was also suppressed by Nox2 blocking. Further study uncovered that Nox2 inhibitor caused the downregulation of p-p53, p21, p-FoxO1 and Bax, and the upregulation of anti-apoptotic protein Bcl-2. In vivo, Nox2 knockdown in grafted BMSCs led to the improvement of EF and FS in infarcted myocardium than BMSCs without Nox2 knockdown. Consistently, more retention and survival of BMSCs were found after Nox2 knockdown. Taken together, Nox2 inhibition enhances anti-aging and anti-apoptotic ability of BMSCs, and thus promotes survival and retention of BMSCs, which provides a new strategy for improving BMSCs-based therapy.

Inhibition of iron overload-induced apoptosis and necrosis of bone marrow mesenchymal stem cells by melatonin.

Iron overload induces severe damage to several vital organs such as the liver, heart and bone, and thus contributes to the dysfunction of these organs. The aim of this study is to investigate whether iron overload causes the apoptosis and necrosis of bone marrow mesenchymal stem cells (BMSCs) and melatonin may prevent its toxicity. Perls' Prussion blue staining showed that exposure to increased concentrations of ferric ammonium citrate (FAC) induced a gradual increase of intracellular iron level in BMSCs. Trypan blue staining demonstrated that FAC decreased the viability of BMSCs in a concentration-dependent manner. Notably, melatonin protected BMSCs against apoptosis and necrosis induced by FAC and it was vertified by Live/Dead, TUNEL and PI/Hoechst stainings. Furthermore, melatonin pretreatment suppressed FAC-induced reactive oxygen species accumulation. Western blot showed that exposure to FAC resulted in the decrease of anti-apoptotic protein Bcl-2 and the increase of pro-apoptotic protein Bax and Cleaved Caspase-3, and necrosis-related proteins RIP1 and RIP3, which were significantly inhibited by melatonin treatment. At last, melatonin receptor blocker luzindole failed to block the protection of BMSCs apoptosis and necrosis by melatonin. Taken together, melatonin protected BMSCs from iron overload induced apoptosis and necrosis by regulating Bcl-2, Bax, Cleaved Caspase-3, RIP1 and RIP3 pathways.