Stress-mediated p38 activation promotes somatic cell reprogramming

Hypo-osmolarity promotes naive pluripotency by reshaping cytoskeleton and increasing chromatin accessibility

INTRODUCTION

Cell fate determination and transition are of paramount importance in biology and medicine. Naive pluripotency could be achieved by reprogramming differentiated cells. However, the mechanism is less clear. Osmolarity is an essential physical factor that acts on living cells, especially for pluripotent cells, but its significance in cell fate transition remains unexplored.

OBJECTIVES

To investigate the role of osmolarity in cell fate transition and its underlying mechanism.

METHODS

Flow cytometry, quantitative real-time PCR, teratoma and chimeric mice assays were performed to assess reprogramming efficiency and characterize iPSCs. TEM, immunofluorescence staining, western blot, chemical treatment and genetic modification were utilized to evaluate cell morphology, signaling pathways, cytoskeleton and nuclear structure. Multiomic sequencings were applied to unveil the transcriptome, histone markers and chromatin accessibility of EpiSCs in hypo-osmotic condition.

RESULTS

In hypo-osmotic condition, the reprogramming efficiency of hypo-osmotic EpiSCs increased over 60-fold than that of iso-osmotic cells (1100 vs 18 colonies per 3 × 105 cells), whereas no colony formed in hyper-osmotic cells. As expected, the converted cells displayed naive pluripotency. The hypo-osmotic EpiSCs exhibited larger cell size, nuclear area and less heterochromatin; ATAC-seq and ChIP-seq confirmed the increased accessibility of naive pluripotent gene loci with more H3K27ac. Mechanistically, hypo-osmolarity activated PI3K-AKT-SP1 signaling in EpiSCs, which reshaped cytoskeleton and nucleoskeleton, resulting in genome reorganization and pluripotent gene expression. In contrast, hypo-osmolarity delayed the ESCs' exit from naive pluripotency. Moreover, in MEFs reprograming, hypo-osmolarity promoted the conversion to naive pluripotency.

CONCLUSION

Hypo-osmolarity promotes cell fate transition by remodeling cytoskeleton, nucleoskeleton and genome via PI3K-AKT-SP1 pathway.

Enhancing cord blood stem cell-derived NK cell growth and differentiation through hyperosmosis

BACKGROUND

Natural killer (NK) cells hold great promise in treating diverse hematopoietic and solid tumors. Despite their availability from peripheral blood and cord blood, stem cell-derived NK cells offer an 'off-the-shelf' solution. Hematopoietic stem and progenitor cells (HSPCs) derived from cord blood pose no risk to the newborn or mother and are virtually ideal sources for NK cell differentiation.

METHODS

We developed a modified protocol to differentiate HSPCs to NK cells under serum-free conditions using defined factors. The HSPC-derived NK (HSC-NK) cells could be expanded in a K562 feeder cell-dependent manner. Furthermore, using lentivirus transduction, chimeric antigen receptor (CAR)-modified HSPCs could be differentiated into NK cells, leading to the establishment of CAR-NK cells.

RESULTS

The efficiency of NK cell differentiation from HSPCs was increased through the simple modulation of osmotic pressure by the addition of sodium chloride or glucose. Furthermore, the hyperosmosis-primed HSC-NK cells exhibited enhanced proliferation capacity and maintained normal functional characteristics, including transcriptome and antitumor efficacy. The optimized protocol yielded approximately 1.8 million NK cells from a single CD34-positive cell within a 28-day cycle, which signifies more than a ten-fold increase in efficiency relative to the conventional methods. This optimized protocol was also suitable for generating CAR-NK cells with high yields compared to standard conditions.

CONCLUSIONS

The results of this study establish high osmotic pressure as a simple yet powerful adjustment that significantly enhances the efficiency and functionality of HSC-NK cells, including CAR-NK cells. This optimized protocol could lead to cost-effective, high-yield NK cell therapies, potentially revolutionizing cancer immunotherapy strategies.

Modelling cell adaptation using internal variables: Accounting for cell plasticity in continuum mathematical biology

Cellular adaptation is the ability of cells to change in response to different stimuli and environmental conditions. It occurs via phenotypic plasticity, that is, changes in gene expression derived from changes in the physiological environment. This phenomenon is important in many biological processes, in particular in cancer evolution and its treatment. Therefore, it is crucial to understand the mechanisms behind it. Specifically, the emergence of the cancer stem cell phenotype, showing enhanced proliferation and invasion rates, is an essential process in tumour progression. We present a mathematical framework to simulate phenotypic heterogeneity in different cell populations as a result of their interaction with chemical species in their microenvironment, through a continuum model using the well-known concept of internal variables to model cell phenotype. The resulting model, derived from conservation laws, incorporates the relationship between the phenotype and the history of the stimuli to which cells have been subjected, together with the inheritance of that phenotype. To illustrate the model capabilities, it is particularised for glioblastoma adaptation to hypoxia. A parametric analysis is carried out to investigate the impact of each model parameter regulating cellular adaptation, showing that it permits reproducing different trends reported in the scientific literature. The framework can be easily adapted to any particular problem of cell plasticity, with the main limitation of having enough cells to allow working with continuum variables. With appropriate calibration and validation, it could be useful for exploring the underlying processes of cellular adaptation, as well as for proposing favourable/unfavourable conditions or treatments.

Oncoprotein SET dynamically regulates cellular stress response through nucleocytoplasmic transport in breast cancer

SETβ is the predominant isoform of oncoprotein SE translocation (SET) in various breast cancer cell lines. Interactome-transcriptome analysis has shown that SETβ is intimately associated with cellular stress response. Among various exogenous stimuli, formaldehyde (FA) causes distinct biological effects in a dose-dependent manner. In response to FA at different concentrations, SET dynamically shuttles between the nucleus and cytoplasm, performing diverse biofunctions to restore homeostasis. At a low concentration, FA acts as an epidermal growth factor (EGF) and activates the HER2 receptor and downstream signaling pathways in HER2+ breast cancer cells, resulting in enhanced cell proliferation. Nucleocytoplasmic transport of SETβ is controlled by the PI3K/PKCα/CK2α axis and depletion or blockade of the transport of SETβ suppresses EGF-induced activation of AKT and ERK. SETβ also inhibits not only stress-induced activation of p38 MAPK signaling pathway, but also assembly of stress granules by hindering formation of the G3BP1-RNA complex. Our findings suggest that SET functions as an important regulator which modulates cellular stress signaling pathways dynamically.

Long Noncoding RNA U90926 Is Induced in Activated Macrophages, Is Protective in Endotoxic Shock, and Encodes a Novel Secreted Protein

Thousands of long noncoding RNAs are encoded in mammalian genomes, yet most remain uncharacterized. In this study, we functionally characterized a mouse long noncoding RNA named U90926. Analysis of U90926 RNA levels revealed minimal expression across multiple tissues at steady state. However, the expression of this gene was highly induced in macrophages and dendritic cells by TLR activation, in a p38 MAPK- and MyD88-dependent manner. To study the function of U90926, we generated U90926-deficient (U9-KO) mice. Surprisingly, we found minimal effects of U90926 deficiency in cultured macrophages. Given the lack of macrophage-intrinsic effect, we investigated the subcellular localization of U90926 transcript and its protein-coding potential. We found that U90926 RNA localizes to the cytosol, associates with ribosomes, and contains an open reading frame that encodes a novel glycosylated protein (termed U9-ORF), which is secreted from the cell. An in vivo model of endotoxic shock revealed that, in comparison with wild type mice, U9-KO mice exhibited increased sickness responses and mortality. Mechanistically, serum levels of IL-6 were elevated in U9-KO mice, and IL-6 neutralization improved endotoxemia outcomes in U9-KO mice. Taken together, these results suggest that U90926 expression is protective during endotoxic shock, potentially mediated by the paracrine and/or endocrine actions of the novel U9-ORF protein secreted by activated myeloid cells.

Attenuating iPSC reprogramming stress with dominant-negative BET peptides

Generation of induced pluripotent stem cells (iPSCs) is inefficient and stochastic. The underlying causes for these deficiencies are elusive. Here, we showed that the reprogramming factors (OCT4, SOX2, and KLF4, collectively OSK) elicit dramatic reprogramming stress even without the pro-oncogene MYC including massive transcriptional turbulence, massive and random deregulation of stress-response genes, cell cycle impairment, downregulation of mitotic genes, illegitimate reprogramming, and cytotoxicity. The conserved dominant-negative (DN) peptides of the three ubiquitous human bromodomain and extraterminal (BET) proteins enhanced iPSC reprogramming and mitigated all the reprogramming stresses mentioned above. The concept of reprogramming stress developed here affords an alternative avenue to understanding and improving iPSC reprogramming. These DN BET fragments target a similar set of the genes as the BET chemical inhibitors do, indicating a distinct approach to targeting BET proteins.

MAP2K6 remodels chromatin and facilitates reprogramming by activating Gatad2b-phosphorylation dependent heterochromatin loosening

Somatic cell reprogramming is an ideal model for studying epigenetic regulation as it undergoes dramatic chromatin remodeling. However, a role for phosphorylation signaling in chromatin protein modifications for reprogramming remains unclear. Here, we identified mitogen-activated protein kinase kinase 6 (Mkk6) as a chromatin relaxer and found that it could significantly enhance reprogramming. The function of Mkk6 in heterochromatin loosening and reprogramming requires its kinase activity but does not depend on its best-known target, P38. We identified Gatad2b as a novel target of Mkk6 phosphorylation that acts downstream to elevate histone acetylation levels and loosen heterochromatin. As a result, Mkk6 over-expression facilitates binding of Sox2 and Klf4 to their targets and promotes pluripotency gene expression during reprogramming. Our studies not only reveal an Mkk phosphorylation mediated modulation of chromatin status in reprogramming, but also provide new rationales to further investigate and improve the cell fate determination processes.

Uncompensated mitochondrial oxidative stress underlies heart failure in an iPSC-derived model of congenital heart disease

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease with 30% mortality from heart failure (HF) in the first year of life, but the cause of early HF remains unknown. Induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CM) from patients with HLHS showed that early HF is associated with increased apoptosis, mitochondrial respiration defects, and redox stress from abnormal mitochondrial permeability transition pore (mPTP) opening and failed antioxidant response. In contrast, iPSC-CM from patients without early HF showed normal respiration with elevated antioxidant response. Single-cell transcriptomics confirmed that early HF is associated with mitochondrial dysfunction accompanied with endoplasmic reticulum (ER) stress. These findings indicate that uncompensated oxidative stress underlies early HF in HLHS. Importantly, mitochondrial respiration defects, oxidative stress, and apoptosis were rescued by treatment with sildenafil to inhibit mPTP opening or TUDCA to suppress ER stress. Together these findings point to the potential use of patient iPSC-CM for modeling clinical heart failure and the development of therapeutics.

Genetic resiliency associated with dominant lethal TPM1 mutation causing atrial septal defect with high heritability

Analysis of large-scale human genomic data has yielded unexplained mutations known to cause severe disease in healthy individuals. Here, we report the unexpected recovery of a rare dominant lethal mutation in TPM1, a sarcomeric actin-binding protein, in eight individuals with large atrial septal defect (ASD) in a five-generation pedigree. Mice with Tpm1 mutation exhibit early embryonic lethality with disrupted myofibril assembly and no heartbeat. However, patient-induced pluripotent-stem-cell-derived cardiomyocytes show normal beating with mild myofilament defect, indicating disease suppression. A variant in TLN2, another myofilament actin-binding protein, is identified as a candidate suppressor. Mouse CRISPR knock-in (KI) of both the TLN2 and TPM1 variants rescues heart beating, with near-term fetuses exhibiting large ASD. Thus, the role of TPM1 in ASD pathogenesis unfolds with suppression of its embryonic lethality by protective TLN2 variant. These findings provide evidence that genetic resiliency can arise with genetic suppression of a deleterious mutation.

AMPK activation reverts mouse epiblast stem cells to naive state

Despite increasing knowledge on primed and naive pluripotency, the cell signaling that regulates the pluripotency type in stem cells remains not fully understood. Here we show that AMP kinase (AMPK) activators can induce the reversion of primed mouse epiblast stem cells (mEpiSCs) to the naive pluripotent state. The addition of AMPK activators alone or together with leukemia inhibitory factor to primed mEpiSCs induced the appearance of naive-like cells. After passaging in naive culture conditions, the colony morphology, protein expression, and global gene expression profiles indicated the naive state, as did germline transmission ability. Loss-of-function and gain-of-function studies suggested that p38 is a critical downstream target in AMPK activation. Finally, single-cell RNA sequencing analysis revealed that the reversion process through AMPK signaling passes an intermediate naive-like population. In conclusion, the AMPK pathway is a critical driving force in the reversion of primed to naive pluripotency.

Plant callus-derived shikimic acid regenerates human skin through converting human dermal fibroblasts into multipotent skin-derived precursor cells

Background

The human skin-derived precursors (SKPs) are a good cell source for regeneration. However, the isolation of SKP from human skin is limited. To overcome this drawback, we hypothesized that the component of plant stem cells could convert human fibroblasts to SKPs.

Methods

Human dermal fibroblasts were treated with shikimic acid, a major component of Sequoiadendron giganteum callus extract. The characteristics of these reprogrammed cells were analyzed by qPCR, western blot, colony-forming assay, and immunofluorescence staining. Artificial human skin was used for CO₂ laser-induced wound experiments. Human tissues were analyzed by immunohistochemistry.

Results

The reprogrammed cells expressed nestin (a neural precursor-specific protein), fibronectin, and vimentin and could differentiate into the ectodermal and mesodermal lineage. Nestin expression was induced by shikimic acid through the mannose receptor and subsequent MYD88 activation, leading to P38 phosphorylation and then CREB binding to the nestin gene promoter. Finally, we confirmed that shikimic acid facilitated the healing of cut injury and enhanced dermal reconstruction in a human artificial skin model. Moreover, in a clinical study with healthy volunteers, plant callus extracts increased the expression of stem cell markers in the basal layer of the epidermis and collagen deposit in the dermis.

Conclusions

These results indicate that shikimic acid is an effective agent for tissue regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02409-3.

Small Molecules that Promote Self-Renewal of Stem Cells and Somatic Cell Reprogramming

The ground state of embryonic stem cells (ESCs) is closely related to the development of regenerative medicine. Particularly, long-term culture of ESCs in vitro, maintenance of their undifferentiated state, self-renewal and multi-directional differentiation ability is the premise of ESCs mechanism and application research. Induced pluripotent stem cells (iPSC) reprogrammed from mouse embryonic fibroblasts (MEF) cells into cells with most of the ESC characteristics show promise towards solving ethical problems currently facing stem cell research. However, integration into chromosomal DNA through viral-mediated genes may activate proto oncogenes and lead to risk of cancer of iPSC. At the same time, iPS induction efficiency needs to be further improved to reduce the use of transcription factors. In this review, we discuss small molecules that promote self-renewal and reprogramming, including growth factor receptor inhibitors, GSK-3β and histone deacetylase inhibitors, metabolic regulators, pathway modulators as well as EMT/MET regulation inhibitors to enhance maintenance of ESCs and enable reprogramming. Additionally, we summarize the mechanism of action of small molecules on ESC self-renewal and iPSC reprogramming. Finally, we will report on the progress in identification of novel and potentially effective agents as well as selected strategies that show promise in regenerative medicine. On this basis, development of more small molecule combinations and efficient induction of chemically induced pluripotent stem cell (CiPSC) is vital for stem cell therapy. This will significantly improve research in pathogenesis, individualized drug screening, stem cell transplantation, tissue engineering and many other aspects.

Induced Pluripotent Stem Cells for Ischemic Stroke Treatment

Ischemic stroke is one of the main central nervous system diseases and is associated with high disability and mortality rates. Recombinant tissue plasminogen activator (rt-PA) and mechanical thrombectomy are the optimal therapies available currently to restore blood flow in patients with stroke; however, their limitations are well recognized. Therefore, new treatments are urgently required to overcome these shortcomings. Recently, stem cell transplantation technology, involving the transplantation of induced pluripotent stem cells (iPSCs), has drawn the interest of neuroscientists and is considered to be a promising alternative for ischemic stroke treatment. iPSCs are a class of cells produced by introducing specific transcription factors into somatic cells, and are similar to embryonic stem cells in biological function. Here, we have reviewed the current applications of stem cells with a focus on iPSC therapy in ischemic stroke, including the neuroprotective mechanisms, development constraints, major challenges to overcome, and clinical prospects. Based on the current state of research, we believe that stem cells, especially iPSCs, will pave the way for future stroke treatment.

Matrine attenuates pathological cardiac fibrosis via RPS5/p38 in mice

Pathological cardiac fibrosis is a common feature in multiple cardiovascular diseases that contributes to the occurrence of heart failure and life-threatening arrhythmias. Our previous study demonstrated that matrine could attenuate doxorubicin-induced oxidative stress and cardiomyocyte apoptosis. In this study, we investigated the effect of matrine on cardiac fibrosis. Mice received aortic banding (AB) operation or continuous injection of isoprenaline (ISO) to generate pathological cardiac fibrosis and then were exposed to matrine lavage (200 mg·kg-1·d-1) or an equal volume of vehicle as the control. We found that matrine lavage significantly attenuated AB or ISO-induced fibrotic remodeling and cardiac dysfunction. We also showed that matrine (200 μmol/L) significantly inhibited the proliferation, migration, collagen production, and phenotypic transdifferentiation of cardiac fibroblasts. Mechanistically, matrine suppressed p38 activation in vivo and in vitro, and overexpression of constitutively active p38 completely abolished the protective effects of matrine. We also demonstrated that ribosomal protein S5 (RPS5) upregulation was responsible for matrine-mediated inhibition on p38 and fibrogenesis. More importantly, matrine was capable of ameliorating preexisting cardiac fibrosis in mice. In conclusion, matrine treatment attenuates cardiac fibrosis by regulating RPS5/p38 signaling in mice, and it might be a promising therapeutic agent for treating pathological cardiac fibrosis.

AMPK activators contribute to maintain naïve pluripotency in mouse embryonic stem cells

Pluripotent stem cells retain the property to self-renew and differentiate into all cell types under defined conditions. Among mouse embryonic stem cells (ESCs), which are pluripotent but heterogenous in gene expression and morphology, an ESC population cultured in small molecule inhibitors of two kinases, MAPK/ERK kinase (Mek) and Glycogen synthase kinase 3 (Gsk3), and leukemia inhibitory factor (Lif) (2i/L) is considered to be naïve pluripotent with uniform pluripotent machinery operation. Though the gene regulatory mechanism for the naïve pluripotency has been investigated in recent years, it is still not fully elucidated. Here we show a novel signaling involved in the maintenance of naïve pluripotency. An AMP-activated protein kinase (AMPK) activator, AICAR (5-Aminoimidazole-4-carboxamied-1-β-riboside) blocked the differentiation of mouse naïve ESCs in the absence of 2i/L and maintained the naïve state. AICAR with Lif condition induced an almost comparable level of naïve pluripotent gene expression in mouse ESCs. Another AMPK activator, A769662, also showed similar effects. A p38 inhibitor, SB203580, blocked the AMPK activation-elicited naïve state maintenance. On the other hand, p38 activation partially mimicked the maintenance effects of AMPK activators, suggesting that p38 is one of the functional downstream molecules to conduct the AMPK effects. Thus, AMPK pathway should be involved in the molecular circuitry of naïve pluripotency in mouse ESCs. These findings would be a valuable clue to further elucidate the molecular machinery of naïve pluripotency.

Quasi-Stem Cells Derived from Human Somatic Cells by Chemically Modified Carbon Nanotubes

Surface modification of micro- and nanotopography was employed to alter the surface properties of scaffolds for controlling cell attachment, proliferation, and differentiation. This study reports a method for generating multinucleated colonies as evidenced by spherical colony formation through nanotopography-induced expression of reprogramming factors in human dermal fibroblasts. Colony formation was achieved by subjecting the cells to specific environments such as culturing with single-walled carbon nanotubes and poly-l-lysine (PLL-SWCNTs). We obtained encouraging results showing that PLL-SWCNT treatment transformed fibroblast cells, and the transformed cells expressed the pluripotency-associated factors OCT4, NANOG, and SOX2 in addition to TRA-1-60 and SSEA-4, which are characteristic stem cell markers. Downregulation of lamin A/C, HDAC1, HDAC6, Bcl2, cytochrome c, p-FAK, p-ERK, and p-JNK and upregulation of H3K4me3 and p-p38 were confirmed in the generated colonies, indicating reprogramming of cells. This protocol increases the possibility of successfully reprogramming somatic cells into induced pluripotent stem cells (iPSCs), thereby overcoming the difficulties in iPSC generation such as genetic mutations, carcinogenesis, and undetermined risk factors.

Post-irradiation promotes susceptibility to reprogramming to pluripotent state in human fibroblasts

Ionizing radiation causes not only targeted effects in cells that have been directly irradiated but also non-targeted effects in several cell generations after initial exposure. Recent studies suggest that radiation can enrich for a population of stem cells, derived from differentiated cells, through cellular reprogramming. Here, we elucidate the effect of irradiation on reprogramming, subjected to two different responses, using an induced pluripotent stem cell (iPSC) model. iPSCs were generated from non-irradiated cells, directly-irradiated cells, or cells subsequently generated after initial radiation exposure. We found that direct irradiation negatively affected iPSC induction in a dose-dependent manner. However, in the post-irradiated group, after five subsequent generations, cells became increasingly sensitive to the induction of reprogramming compared to that in non-irradiated cells as observed by an increased number of Tra1-81-stained colonies as well as enhanced alkaline phosphatase and Oct4 promoter activity. Comparative analysis, based on reducing the number of defined factors utilized for reprogramming, also revealed enhanced efficiency of iPSC generation in post-irradiated cells. Furthermore, the phenotypic acquisition of characteristics of pluripotent stem cells was observed in all resulting iPSC lines, as shown by morphology, the expression of pluripotent markers, DNA methylation patterns of pluripotency genes, a normal diploid karyotype, and teratoma formation. Overall, these results suggested that reprogramming capability might be differentially modulated by altered radiation-induced responses. Our findings provide that susceptibility to reprogramming in somatic cells might be improved by the delayed effects of non-targeted response, and contribute to a better understanding of the biological effects of radiation exposure.

Chemical Cocktails Enable Hepatic Reprogramming of Mouse Fibroblasts with a Single Transcription Factor

Liver or hepatocytes transplantation is limited by the availability of donor organs. Functional hepatocytes independent of the donor sources may have wide applications in regenerative medicine and the drug industry. Recent studies have demonstrated that chemical cocktails may induce reprogramming of fibroblasts into a range of functional somatic cells. Here, we show that mouse fibroblasts can be transdifferentiated into the hepatocyte-like cells (iHeps) using only one transcription factor (TF) (Foxa1, Foxa2, or Foxa3) plus a chemical cocktail. These iHeps show typical epithelial morphology, express multiple hepatocyte-specific genes, and acquire hepatocyte functions. Genetic lineage tracing confirms the fibroblast origin of these iHeps. More interestingly, these iHeps are expandable in vitro and can reconstitute the damaged hepatic tissues of the fumarylacetoacetate hydrolase-deficient (Fah⁻/⁻) mice. Our study provides a strategy to generate functional hepatocyte-like cells by using a single TF plus a chemical cocktail and is one step closer to generate the full-chemical iHeps.

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Fibroblasts are converted to iHeps using only one TF plus a chemical cocktail

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Genetic lineage tracing confirms the fibroblast origin of these iHeps

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The iHeps are expendable and functional both in vitro and in vivo

A critical role for p38MAPK signalling pathway during reprogramming of human fibroblasts to iPSCs

Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) holds enormous promise for regenerative medicine. Reprogramming is a stepwise process with well-defined stages of initiation, maturation and stabilisation which are critically dependent on interactions between key pluripotency transcription factors, epigenetic regulators and signalling pathways. In this manuscript we have investigated the role of p38 MAPK signalling pathway and have shown a subpopulation- and phase-specific pattern of activation occurring during the initiation and maturation stage of reprogramming in partially and fully reprogrammed cells respectively. Downregulation of p38 MAPK activity via RNA interference or small molecule inhibitor led to cell accumulation in G1 phase of the cell cycle and reduced expression of cell cycle regulators during the initiation stage of reprogramming. This was associated with a significant downregulation of key pluripotency marker expression, disruption of mesenchymal to epithelial transition (MET), increased expression of differentiation markers and presence of partially reprogrammed cells which retained a typical gene expression profile of mesendodermal cells and were unable to progress to fully reprogrammed phenotype. Together our data indicate an important role for p38 MAPK activity in proliferation, MET progression and establishment of pluripotent phenotype, which are necessary steps for the development of human iPSCs.

Selenoprotein X Gene Knockdown Aggravated H2O2-Induced Apoptosis in Liver LO2 Cells

To determine the roles of selenoprotein X gene (Selx) in protecting liver cells against oxidative damage, the influences of Selx knockdown on H2O2-induced apoptosis in human normal hepatocyte (LO2) cells were studied. pSilencer 3.1 was used to develop knockdown vector targeting the 3'-UTR of human Selx. The Selx knockdown and control cells were further exposed to H2O2, and cell viability, cell apoptosis rate, and the expression levels of mRNA and protein of apoptosis-related genes were detected. The results showed that vector targeting the 3'-UTR of Selx successfully silenced mRNA or protein expression of SelX in LO2 cells. Selx knockdown resulted in decreased cell viability, increased percentage of early apoptotic cells, decreased Bcl2A1 and Bcl-2 expression, and increased phosphorylation of P38 in LO2 cells. When Selx knockdown LO2 cells were exposed to H2O2, characteristics of H2O2-induced cell dysfunctions were further exacerbated. Taken together, our findings suggested that SelX played important roles in protecting LO2 cells against oxidative damage and reducing H2O2-induced apoptosis in liver cells.

Natural variability in Drosophila larval and pupal NaCl tolerance

The regulation of NaCl is essential for the maintenance of cellular tonicity and functionality, and excessive salt exposure has many adverse effects. The fruit fly, Drosophila melanogaster, is a good osmoregulator and some strains can survive on media with very low or high NaCl content. Previous analyses of mutant alleles have implicated various stress signaling cascades in NaCl sensitivity or tolerance; however, the genes influencing natural variability of NaCl tolerance remain for the most part unknown. Here, we use two approaches to investigate natural variation in D. melanogaster NaCl tolerance. We describe four D. melanogaster lines that were selected for different degrees of NaCl tolerance, and present data on their survival, development, and pupation position when raised on varying NaCl concentrations. After finding evidence for natural variation in salt tolerance, we present the results of Quantitative Trait Loci (QTL) mapping of natural variation in larval and pupal NaCl tolerance, and identify different genomic regions associated with NaCl tolerance during larval and pupal development.

ROS/p38/p53/Puma signaling pathway is involved in emodin-induced apoptosis of human colorectal cancer cells

AIM

Emodin was found effective in suppressing proliferation of cancer cells including colorectal cancer (CRC), but the mechanisms were still unclear. This study was aimed to investigate the possible mechanism of emodin's anti-CRC effects.

METHODS

Two most frequently used CRC cell lines, SW480 and SW620, were investigated in this study. Serially diluted emodin solutions were used to incubate CRC cells. siRNAs were used to silence the expressions of p38 and Puma respectively. Intracellular ROS production was detected by DCFH-DA staining; proliferation and apoptosis of CRC cells were assessed by MTT assay and Hoechst staining respectively. Western blotting was applied to evaluate the activation of p38/p53/Puma signaling.

RESULTS

Both in SW480 and SW620 cells, emodin inhibited proliferation by inducing ROS-mediated apoptosis in a concentration-dependent manner. The p38/p53/Puma signaling was also activated after emodin incubation in a concentration-dependent manner. The ROS scavenger NAC, p38 silencing and Puma silencing impaired the anti-proliferation and apoptosis- inducing effects of emodin.

CONCLUSIONS

emodin inhibited proliferation of human CRC cells by inducing cell apoptosis by activating ROS/p38/p53/Puma signaling.

Autophagy and mTORC1 regulate the stochastic phase of somatic cell reprogramming

We describe robust induction of autophagy during the reprogramming of mouse fibroblasts to induced pluripotent stem cells by four reprogramming factors (Sox2, Oct4, Klf4 and c-Myc), henceforth 4F. This process occurs independently of p53 activation, and is mediated by the synergistic downregulation of mechanistic target of rapamycin complex 1 (mTORC1) and the induction of autophagy-related genes. The 4F coordinately repress mTORC1, but bifurcate in their regulation of autophagy-related genes, with Klf4 and c-Myc inducing them but Sox2 and Oct4 inhibiting them. On one hand, inhibition of mTORC1 facilitates reprogramming by promoting cell reshaping (mitochondrial remodelling and cell size reduction). On the other hand, mTORC1 paradoxically impairs reprogramming by triggering autophagy. Autophagy does not participate in cell reshaping in reprogramming but instead degrades p62, whose accumulation in autophagy-deficient cells facilitates reprogramming. Our results thus reveal a complex signalling network involving mTORC1 inhibition and autophagy induction in the early phase of reprogramming, whose delicate balance ultimately determines reprogramming efficiency.

Current advances in the generation of human iPS cells: implications in cell-based regenerative medicine

Over the last few years, the generation of induced pluripotent stem cells (iPSCs) from human somatic cells has proved to be one of the most potentially useful discoveries in regenerative medicine. iPSCs are becoming an invaluable tool to study the pathology of different diseases and for drug screening. However, several limitations still affect the possibility of applying iPS cell-based technology in therapeutic prospects. Most strategies for iPSCs generation are based on gene delivery via retroviral or lentiviral vectors, which integrate into the host's cell genome, causing a remarkable risk of insertional mutagenesis and oncogenic transformation. To avoid such risks, significant advances have been made with non-integrative reprogramming strategies. On the other hand, although many different kinds of somatic cells have been employed to generate iPSCs, there is still no consensus about the ideal type of cell to be reprogrammed. In this review we present the recent advances in the generation of human iPSCs, discussing their advantages and limitations in terms of safety and efficiency. We also present a selection of somatic cell sources, considering their capability to be reprogrammed and tissue accessibility. From a translational medicine perspective, these two topics will provide evidence to elucidate the most suitable combination of reprogramming strategy and cell source to be applied in each human iPSC-based therapy. The wide variety of diseases this technology could treat opens a hopeful future for regenerative medicine. Copyright © 2015 John Wiley & Sons, Ltd.

Reprogramming fibroblasts to pluripotency using arginine-terminated polyamidoamine nanoparticles based non-viral gene delivery system

Induced pluripotent stem cells (iPSCs) have attracted keen interest in regenerative medicine. The generation of iPSCs from somatic cells can be achieved by the delivery of defined transcription factor (Oct4, Sox2, Klf4, and c-Myc[OSKM]). However, most instances of iPSC-generation have been achieved by potentially harmful genome-integrating viral vectors. Here we report the generation of iPSCs from mouse embryonic fibroblasts (MEFs) using arginine-terminated generation 4 polyamidoamine (G4Arg) nanoparticles as a nonviral transfection vector for the delivery of a single plasmid construct carrying OSKM (pOSKM). Our results showed that G4Arg nanoparticles delivered pOSKM into MEFs at a significantly higher transfection efficiency than did conventional transfection reagents. After serial transfections of pOSKM-encapsulated G4Arg nanoparticles, we successfully generated iPSCs from MEFs. Our study demonstrates that G4Arg nanoparticles may be a promising candidate for generating of virus-free iPSCs that have great potential for clinical application.

Cell reprogramming. Histone chaperone ASF1A is required for maintenance of pluripotency and cellular reprogramming

Unfertilized oocytes have the intrinsic capacity to remodel sperm and the nuclei of somatic cells. The discoveries that cells can change their phenotype from differentiated to embryonic state using oocytes or specific transcription factors have been recognized as two major breakthroughs in the biomedical field. Here, we show that ASF1A, a histone-remodeling chaperone specifically enriched in the metaphase II human oocyte, is necessary for reprogramming of human adult dermal fibroblasts (hADFs) into undifferentiated induced pluripotent stem cell. We also show that overexpression of just ASF1A and OCT4 in hADFs exposed to the oocyte-specific paracrine growth factor GDF9 can reprogram hADFs into pluripotent cells. Our Report underscores the importance of studying the unfertilized MII oocyte as a means to understand the molecular pathways governing somatic cell reprogramming.

Matrix identity and tractional forces influence indirect cardiac reprogramming

Heart regeneration through in vivo cardiac reprogramming has been demonstrated as a possible regenerative strategy. While it has been reported that cardiac reprogramming in vivo is more efficient than in vitro, the influence of the extracellular microenvironment on cardiac reprogramming remains incompletely understood. This understanding is necessary to improve the efficiency of cardiac reprogramming in order to implement this strategy successfully. Here we have identified matrix identity and cell-generated tractional forces as key determinants of the dedifferentiation and differentiation stages during reprogramming. Cell proliferation, matrix mechanics, and matrix microstructure are also important, but play lesser roles. Our results suggest that the extracellular microenvironment can be optimized to enhance cardiac reprogramming.

iPSCs and small molecules: a reciprocal effort towards better approaches for drug discovery

The revolutionary induced pluripotent stem cell (iPSC) technology provides a new path for cell replacement therapies and drug screening. Patient-specific iPSCs and subsequent differentiated cells manifesting disease phenotypes will finally position human disease pathology at the core of drug discovery. Cells used to test the toxic effects of drugs can also be generated from normal iPSCs and provide a much more accurate and cost-effective system than many animal models. Here, we highlight the recent progress in iPSC-based cell therapy, disease modeling and drug evaluations. In addition, we discuss the use of small molecule drugs to improve the generation of iPSCs and understand the reprogramming mechanism. It is foreseeable that the interplay between iPSC technology and small molecule compounds will push forward the applications of iPSC-based therapy and screening systems in the real world and eventually revolutionize the methods used to treat diseases.

Roles of small molecules in somatic cell reprogramming

The Nobel Prize in Physiology and Medicine 2012 was awarded to Sir John B GURDON and Shinya YAMANAKA for their discovery that mature cells can be reprogrammed to become pluripotent. This event reaffirms the importance of research on cell fate plasticity and the technology progress in the stem cell field and regenerative medicine. Indeed, reprogramming technology has developed at a dazzling speed within the past 6 years, yet we are still at the early stages of understanding the mechanisms of cell fate identity. This is particularly true in the case of human induced pluripotent stem cells (iPSCs), which lack reliable standards in the evaluation of their fidelity and safety prior to their application. Along with the genetic approaches, small molecules nowadays become convenient tools for modulating endogenous protein functions and regulating key cellular processes, including the mesenchymal-to-epithelial transition, metabolism, signal transduction and epigenetics. Moreover, small molecules may affect not only the efficiency of clone formation but also the quality of the resulting cells. With increasing availability of such chemicals, we can better understand the biology of stems cells and further improve the technology of generation of stem cells.