Feeders facilitate telomere maintenance and chromosomal stability of embryonic stem cells

Assessment of the clonal growth potential of meibomian gland stem/progenitor cells via clonal analysis

PURPOSE

Clonal analysis is a feasible method to evaluate the status of stem/progenitor cells in epidermal or limbus investigations. This study aimed to evaluate the clonal growth potential of meibomian gland (MG) epithelial cells using clonal analysis.

METHODS

Mouse and human MG tissues were isolated and cocultured with 3T3 feeder cells. Immunofluorescent staining of K14, K6a, and PPARγ on MG clones was applied. Holoclones, meroclones and paraclones were categorized based on clonal area. Triple staining and tile scans provided a comprehensive view of MG clone formation. MG ductal and acinar clones were cultured separately to compare stem/progenitor cell characteristics. We further evaluated an age-related MGD (ARMGD) mouse model along with two human MG samples of different ages using clonal analysis. Crystal violet staining was employed to assess clone formation efficiency (CFE).

RESULTS

Both mouse and human MG epithelial cells formed clones on the feeder layers, which enlarged over time. The expression of K14, K6a, and PPARγ was decreased in differentiated clones during development. The CFE of holoclones and meroclones was approximately 1 ‰ in mouse MG clones and approximately 2.5 ‰ in holoclones and 5.6 ‰ in meroclones in human MG clones. The CFE of holoclones generated by ductal epithelial cells was significantly higher than did acinar clones. In the ARMGD mouse model and human samples, smaller clones, reduced CFE, and decreased K14+, K6a+, and PPARγ+ cells in MG clones were identified.

CONCLUSIONS

Clonal analysis effectively evaluates stem and progenitor cells in MGs, revealing deterioration in these cells under MGD conditions.

Zscan4 mediates ubiquitination and degradation of the corepressor complex to promote chromatin accessibility in 2C-like cells

Zygotic genome activation occurs in two-cell (2C) embryos, and a 2C-like state is also activated in sporadic (~1%) naïve embryonic stem cells in mice. Elevated chromatin accessibility is critical for the 2C-like state to occur, yet the underlying molecular mechanisms remain elusive. Zscan4 exhibits burst expression in 2C embryos and 2C-like cells. Here, we show that Zscan4 mediates chromatin remodeling to promote the chromatin accessibility for achieving the 2C-like state. Through coimmunoprecipitation/mass spectrometry, we identified that Zscan4 interacts with the corepressors Kap1/Trim28, Lsd1, and Hdac1, also with H3K9me3 modifiers Suv39h1/2, to transiently form a repressive chromatin complex. Then, Zscan4 mediates the degradation of these chromatin repressors by recruiting Trim25 as an E3 ligase, enabling the ubiquitination of Lsd1, Hdac1, and Suv39h1/2. Degradation of the chromatin repressors promotes the chromatin accessibility for activation of the 2C-like state. These findings reveal the molecular insights into the roles of Zscan4 in promoting full activation of the 2C-like state.

In vivo and in vitro sperm production: an overview of the challenges and advances in male fertility restoration

Male infertility can be caused by genetic anomalies, endocrine disorders, inflammation, and exposure to toxic chemicals or gonadotoxic treatments. Therefore, several recent studies have concentrated on the preservation and restoration of fertility to enhance the quality of life for affected individuals. It is currently recommended to biobank the tissue extracted from testicular biopsies to provide a later source of spermatogonial stem cells (SSCs). Another successful approach has been the in vitro production of haploid male germ cells. The capacity of SSCs to transform into sperm, as in testicular tissue transplantation, SSC therapy, and in vitro or ex vivo spermatogenesis, makes them ideal candidates for in vivo fertility restoration. The transplantation of SSCs or testicular tissue to regenerate spermatogenesis and create embryos has been achieved in nonhuman mammal species. Although the outcomes of human trials have yet to be released, this method may soon be approved for clinical use in humans. Furthermore, regenerative medicine techniques that develop tissue or cells on organic or synthetic scaffolds enriched with bioactive molecules have also gained traction. All of these methods are now in different stages of experimentation and clinical trials. However, thanks to rigorous studies on the safety and effectiveness of SSC-based reproductive treatments, some of these techniques may be clinically available in upcoming decades.

ZFP982 confers mouse embryonic stem cell characteristics by regulating expression of Nanog, Zfp42, and Dppa3

BACKGROUND

Understanding the genetic underpinnings of protein networks conferring stemness is of broad interest for basic and translational research.

METHODS

We used multi-omics analyses to identify and characterize stemness genes, and focused on the zinc finger protein 982 (Zfp982) that regulates stemness through the expression of Nanog, Zfp42, and Dppa3 in mouse embryonic stem cells (mESC).

RESULTS

Zfp982 was expressed in stem cells, and bound to chromatin through a GCAGAGKC motif, for example near the stemness genes Nanog, Zfp42, and Dppa3. Nanog and Zfp42 were direct targets of ZFP982 that decreased in expression upon knockdown and increased upon overexpression of Zfp982. We show that ZFP982 expression strongly correlated with stem cell characteristics, both on the transcriptional and morphological levels. Zfp982 expression decreased with progressive differentiation into ecto-, endo- and mesodermal cell lineages, and knockdown of Zfp982 correlated with morphological and transcriptional features of differentiated cells. Zfp982 showed transcriptional overlap with members of the Hippo signaling pathway, one of which was Yap1, the major co-activator of Hippo signaling. Despite the observation that ZFP982 and YAP1 interacted and localized predominantly to the cytoplasm upon differentiation, the localization of YAP1 was not influenced by ZFP982 localization.

CONCLUSIONS

Together, our study identified ZFP982 as a transcriptional regulator of early stemness genes, and since ZFP982 is under the control of the Hippo pathway, underscored the importance of the context-dependent Hippo signals for stem cell characteristics.

Learning Towards Maturation of Defined Feeder-free Pluripotency Culture Systems: Lessons from Conventional Feeder-based Systems

Pluripotent stem cells (PSCs) are widely recognized as one of the most promising types of stem cells for applications in regenerative medicine, tissue engineering, disease modeling, and drug screening. This is due to their unique ability to differentiate into cells from all three germ layers and their capacity for indefinite self-renewal. Initially, PSCs were cultured using animal feeder cells, but these systems presented several limitations, particularly in terms of Good Manufacturing Practices (GMP) regulations. As a result, feeder-free systems were introduced as a safer alternative. However, the precise mechanisms by which feeder cells support pluripotency are not fully understood. More importantly, it has been observed that some aspects of the need for feeder cells like the optimal density and cell type can vary depending on conditions such as the developmental stage of the PSCs, phases of the culture protocol, the method used in culture for induction of pluripotency, and intrinsic variability of PSCs. Thus, gaining a better understanding of the divergent roles and necessity of feeder cells in various conditions would lead to the development of condition-specific defined feeder-free systems that resolve the failure of current feeder-free systems in some conditions. Therefore, this review aims to explore considerable feeder-related issues that can lead to the development of condition-specific feeder-free systems.

Static Magnetic Fields Promote Generation of Muscle Lineage Cells from Pluripotent Stem Cells and Myoblasts

Static magnetic fields (SMFs) exhibit numerous biological effects and regulate the proliferation and differentiation of several adult stem cells. However, the role of SMFs in the self-renewal maintenance and developmental potential of pluripotent embryonic stem cells (ESCs) remains largely uninvestigated. Here, we show that SMFs promote the expression of the core pluripotent markers Sox2 and SSEA-1. Furthermore, SMFs facilitate the differentiation of ESCs into cardiomyocytes and skeletal muscle cells. Consistently, transcriptome analysis reveals that muscle lineage differentiation and skeletal system specification of ESCs are remarkably strengthened by SMF stimuli. Additionally, when treated with SMFs, C2C12 myoblasts exhibit an increased proliferation rate, improved expression of skeletal muscle markers and elevated myogenic differentiation capacity compared with control cells. Together, our data show that SMFs effectively promote muscle cell generation from pluripotent stem cells and myoblasts. The noninvasive and convenient physical stimuli can be used to increase the production of muscle cells in regenerative medicine and the manufacture of cultured meat in cellular agriculture.

Culture conditions of mouse ESCs impact the tumor appearance in vivo

Various culture conditions by small molecules have been explored to extend pluripotency of stem cells, but their impacts on cell fate in vivo remain elusive. We systematically compared the effects of various culture conditions on the pluripotency and cell fate in vivo of mouse embryonic stem cells (ESCs) by tetraploid embryo complementation assay. Conventional ESC cultures in serum/LIF-based condition produced complete ESC mice and also the survival to adulthood at the highest rates of all other chemical-based cultures. Moreover, long-term examination of the survived ESC mice demonstrated that conventional ESC cultures did not lead to visible abnormality for up to 1.5-2 years, whereas the prolonged chemical-based cultures developed retroperitoneal atypical teratomas or leiomyomas. The chemical-based cultures exhibited transcriptomes and epigenomes that typically differed from those of conventional ESC cultures. Our results warrant further refinement of culture conditions in promoting the pluripotency and safety of ESCs in future applications.

Optimization of bovine embryonic fibroblast feeder layer prepared by Mitomycin C

Feeder cells play important roles in In-vitro culture of stem cells. However, the preparation protocol of feeder cells produced by bovine embryonic fibroblast cells (bEFs) is still lack. In this study, the preparation of bEF-feeder by Mitomycin C was optimized with different concentrations and treatment time. The cell viability of bEFs was detected by CCK8 and 5-Ethynyl-2'-deoxyuridine. The growth of bESCs in each bEFs-feeder group was assessed by alkaline phosphatase staining and CCK8. Quantitative real time PCR was used to detect the mRNA expression of pluripotency-related genes of bESCs. Results showed that the proliferation of bEFs was significantly repressed while bEFs were treated with 14 ug/mL or 16 ug/mL Mitomycin C for 3 h, and the cell viability within 2-4 days after treatment was consistent with the 1st day. The numbers of bESCs clones in bEF-feeder treated with 14 μg/mL Mitomycin C for 3 h or 16 μg/mL Mitomycin C for 3 h were significantly higher than that in bEF-feeder treated with 8 μg/mL Mitomycin C for 8 h or bEFs treated with 6 μg/mL Mitomycin C for 9 h. The mRNA expression of pluripotency-related genes in bESCs cultured by bEF-feeder were higher than the MEF-feeder, the clone morphology of bESCs cultured in bEF-feeder was rounder and sharper than the MEF-feeder. In conclusion, the bEF-feeder prepared with 14 μg/mL Mitomycin C for 3 h or 16 μg/mL Mitomycin C for 3 h could effectively maintains the growth of bESCs, and bEF-feeder is more suitable for bESCs culture than the MEF-feeder.

The adaptation of bovine embryonic stem cells to the changes of feeder layers

Although the feeder-free culture system has been established, the microenvironment provided by the feeder cells still possesses a unique advantage in maintaining the long-term stability and the rapid proliferation of pluripotent stem cells (PSCs). The aim of this study is to discover the adaptive ability of PSCs upon changes of feeder layers. In this study, the morphology, pluripotent marker expression, differentiation ability of bovine embryonic stem cells (bESCs) cultured on low-density, or methanol fixed mouse embryonic fibroblasts were examined by immunofluorescent staining, Western blotting, real-time reverse transcription polymerase chain reaction, and RNA-seq. The results showed that the changes of feeder layers did not induce the rapid differentiation of bESCs, while resulting in the differentiation initiation and alteration of pluripotent state of bESCs. More importantly, the expression of endogenous growth factors and extracellular matrix were increased, and the expression of cell adhesion molecules was altered, which indicated that bESCs may compensate some functions of the feeder layers upon its changes. This study shows the PSCs have the self-adaptive ability responded to the feeder layer alteration.

Exogenous pyruvate and recombinant human basic fibroblast growth factor maintain pluripotency and enhance global metabolic activity of bovine embryonic stem cells grown on low-density feeder layers

A suitable microenvironment or niche is essential for self-renewal and pluripotency of stem cells cultured in vitro, including bovine embryonic stem cells (bESCs). Feeder cells participate in the construction of stem cell niche by secreting growth factors and extracellular matrix proteins. In this study, metabolomics and transcriptomics analyses were used to investigate the effects of low-density feeder cells on bESCs. The results showed that bESCs co-cultured with low-density feeder cells experienced a decrease in pluripotent gene expression, cell differentiation, and a reduction of central carbon metabolic activity. When cell-permeable pyruvate (Pyr) and recombinant human basic fibroblast growth factor (rhbFGF) were added to the culture system, the pluripotency of bESCs on low-density feeder layers was rescued, and acetyl-coenzyme A (AcCoA) synthesis and fatty acid de novo synthesis increased. In addition, rhbFGF enhances the effects of Pyr and activates the overall metabolic level of bESCs grown on low-density feeder layers. This study explored the rescue effects of exogenous Pyr and rhbFGF on bESCs cultured on low-density feeder layers, which will provide a reference for improvement of the PSC culture system through the supplementation of energy metabolites and growth factors.

Snap29 Is Dispensable for Self-Renewal Maintenance but Required for Proper Differentiation of Mouse Embryonic Stem Cells

Pluripotent embryonic stem cells (ESCs) can self-renew indefinitely and are able to differentiate into all three embryonic germ layers. Synaptosomal-associated protein 29 (Snap29) is implicated in numerous intracellular membrane trafficking pathways, including autophagy, which is involved in the maintenance of ESC pluripotency. However, the function of Snap29 in the self-renewal and differentiation of ESCs remains elusive. Here, we show that Snap29 depletion via CRISPR/Cas does not impair the self-renewal and expression of pluripotency-associated factors in mouse ESCs. However, Snap29 deficiency enhances the differentiation of ESCs into cardiomyocytes, as indicated by heart-like beating cells. Furthermore, transcriptome analysis reveals that Snap29 depletion significantly decreased the expression of numerous genes required for germ layer differentiation. Interestingly, Snap29 deficiency does not cause autophagy blockage in ESCs, which might be rescued by the SNAP family member Snap47. Our data show that Snap29 is dispensable for self-renewal maintenance, but required for the proper differentiation of mouse ESCs.

Epigenetics as "conductor" in "orchestra" of pluripotent states

Pluripotent character is described as the potency of cells to differentiate into all three germ layers. The best example to reinstate the term lies in the context of embryonic stem cells (ESCs). Pluripotent ESC describes the in vitro status of those cells that originate during the complex process of embryogenesis. Pre-implantation to post-implantation development of embryo embrace cells with different levels of stemness. Currently, four states of pluripotency have been recognized, in the progressing order of "naïve," "poised," "formative," and "primed." Epigenetics act as the "conductor" in this "orchestra" of transition in pluripotent states. With a distinguishable gene expression profile, these four states associate with different epigenetic signatures, sometimes distinct while otherwise overlapping. The present review focuses on how epigenetic factors, including DNA methylation, bivalent chromatin, chromatin remodelers, chromatin/nuclear architecture, and microRNA, could dictate pluripotent states and their transition among themselves.

A Comprehensive Review on the Role of ZSCAN4 in Embryonic Development, Stem Cells, and Cancer

ZSCAN4 is a transcription factor that plays a pivotal role during early embryonic development. It is a unique gene expressed specifically during the first tide of de novo transcription during the zygotic genome activation. Moreover, it is reported to regulate telomere length in embryonic stem cells and induced pluripotent stem cells. Interestingly, ZSCAN4 is expressed in approximately 5% of the embryonic stem cells in culture at any given time, which points to the fact that it has a tight regulatory system. Furthermore, ZSCAN4, if included in the reprogramming cocktail along with core reprogramming factors, increases the reprogramming efficiency and results in better quality, genetically stable induced pluripotent stem cells. Also, it is reported to have a role in promoting cancer stem cell phenotype and can prospectively be used as a marker for the same. In this review, the multifaceted role of ZSCAN4 in embryonic development, embryonic stem cells, induced pluripotent stem cells, cancer, and germ cells are discussed comprehensively.

BMP4 preserves the developmental potential of mESCs through Ube2s- and Chmp4b-mediated chromosomal stability safeguarding

Chemically defined medium is widely used for culturing mouse embryonic stem cells (mESCs), in which N2B27 works as a substitution for serum, and GSK3β and MEK inhibitors (2i) help to promote ground-state pluripotency. However, recent studies suggested that MEKi might cause irreversible defects that compromise the developmental potential of mESCs. Here, we demonstrated the deficient bone morphogenetic protein (BMP) signal in the chemically defined condition is one of the main causes for the impaired pluripotency. Mechanistically, activating the BMP signal pathway by BMP4 could safeguard the chromosomal integrity and proliferation capacity of mESCs through regulating downstream targets Ube2s and Chmp4b. More importantly, BMP4 promotes a distinct in vivo developmental potential and a long-term pluripotency preservation. Besides, the pluripotent improvements driven by BMP4 are superior to those by attenuating MEK suppression. Taken together, our study shows appropriate activation of BMP signal is essential for regulating functional pluripotency and reveals that BMP4 should be applied in the serum-free culture system.

An ERK5-KLF2 signalling module regulates early embryonic gene expression and telomere rejuvenation in stem cells

The ERK5 MAP kinase signalling pathway drives transcription of naïve pluripotency genes in mouse Embryonic Stem Cells (mESCs). However, how ERK5 impacts on other aspects of mESC biology has not been investigated. Here, we employ quantitative proteomic profiling to identify proteins whose expression is regulated by the ERK5 pathway in mESCs. This reveals a function for ERK5 signalling in regulating dynamically expressed early embryonic 2-cell stage (2C) genes including the mESC rejuvenation factor ZSCAN4. ERK5 signalling and ZSCAN4 induction in mESCs increases telomere length, a key rejuvenative process required for prolonged culture. Mechanistically, ERK5 promotes ZSCAN4 and 2C gene expression via transcription of the KLF2 pluripotency transcription factor. Surprisingly, ERK5 also directly phosphorylates KLF2 to drive ubiquitin-dependent degradation, encoding negative feedback regulation of 2C gene expression. In summary, our data identify a regulatory module whereby ERK5 kinase and transcriptional activities bi-directionally control KLF2 levels to pattern 2C gene transcription and a key mESC rejuvenation process.

Blastocyst-Inspired Hydrogels to Maintain Undifferentiation of Mouse Embryonic Stem Cells

Stem cell fate is determined by specific niches that provide multiple physical, chemical, and biological cues. However, the hierarchy or cascade of impact of these cues remains elusive due to their spatiotemporal complexity. Here, anisotropic silk protein nanofiber-based hydrogels with suitable cell adhesion capacity are developed to mimic the physical microenvironment inside the blastocele. The hydrogels enable mouse embryonic stem cells (mESCs) to maintain stemness in vitro in the absence of both leukemia inhibitory factor (LIF) and mouse embryonic fibroblasts (MEFs), two critical factors in the standard protocol for mESC maintenance. The mESCs on hydrogels can achieve superior pluripotency, genetic stability, developmental capacity, and germline transmission to those cultured with the standard protocol. Such biomaterials establish an improved dynamic niche through stimulating the secretion of autocrine factors and are sufficient to maintain the pluripotency and propagation of ESCs. The mESCs on hydrogels are distinct in their expression profiles and more resemble ESCs in vivo. The physical cues can thus initiate a self-sustaining stemness-maintaining program. In addition to providing a relatively simple and low-cost option for expansion and utility of ESCs in biological research and therapeutic applications, this biomimetic material helps gain more insights into the underpinnings of early mammalian embryogenesis.

Elevated retrotransposon activity and genomic instability in primed pluripotent stem cells

BACKGROUND

Naïve and primed pluripotent stem cells (PSCs) represent two different pluripotent states. Primed PSCs following in vitro culture exhibit lower developmental potency as evidenced by failure in germline chimera assays, unlike mouse naïve PSCs. However, the molecular mechanisms underlying the lower developmental competency of primed PSCs remain elusive.

RESULTS

We examine the regulation of telomere maintenance, retrotransposon activity, and genomic stability of primed PSCs and compare them with naïve PSCs. Surprisingly, primed PSCs only minimally maintain telomeres and show fragile telomeres, associated with declined DNA recombination and repair activity, in contrast to naïve PSCs that robustly elongate telomeres. Also, we identify LINE1 family integrant L1Md_T as naïve-specific retrotransposon and ERVK family integrant IAPEz to define primed PSCs, and their transcription is differentially regulated by heterochromatic histones and Dnmt3b. Notably, genomic instability of primed PSCs is increased, in association with aberrant retrotransposon activity.

CONCLUSIONS

Our data suggest that fragile telomere, retrotransposon-associated genomic instability, and declined DNA recombination repair, together with reduced function of cell cycle and mitochondria, increased apoptosis, and differentiation properties may link to compromised developmental potency of primed PSCs, noticeably distinguishable from naïve PSCs.

Oncostatin M Maintains Naïve Pluripotency of mESCs by Tetraploid Embryo Complementation (TEC) Assay

It has been well established that leukemia inhibitory factor (LIF) is essential for maintaining naïve pluripotency of embryonic stem cells (ESCs). Oncostatin M (OSM) is a member of the IL-6 family of cytokines which share gp130 as a receptor subunit, and the OSM-gp130 complex can recruit either LIF receptor β or OSM receptor β. Here we show that OSM can completely replace LIF to maintain naïve pluripotency of ESCs. Mouse ESCs (mESCs) cultured in the presence of LIF or OSM not only express pluripotency genes at similar levels but also exhibit the same developmental pluripotency as evidenced by the generation of germline competent chimeras, supporting previous findings. Moreover, we demonstrate by tetraploid embryo complementation assay, the most stringent functional test of authentic pluripotency that mESCs cultured in OSM produce viable all-ESC pups. Furthermore, telomere length and telomerase activity, which are also crucial for unlimited self-renewal and genomic stability of mESCs, do not differ in mESCs cultured under OSM or LIF. The transcriptome of mESCs cultured in OSM overall is very similar to that of LIF, and OSM activates Stat3 signaling pathway, like LIF. Additionally, OSM upregulates pentose and glucuronate interconversion, ascorbate and aldarate metabolism, and steroid and retinol metabolic pathways. Although the significance of these pathways remains to be determined, our data shows that OSM can maintain naïve pluripotent stem cells in the absence of LIF.

Complex biology of constitutional ring chromosomes structure and (in)stability revealed by somatic cell reprogramming

Human ring chromosomes are often unstable during mitosis, and daughter cells can be partially or completely aneuploid. We studied the mitotic stability of four ring chromosomes, 8, 13, 18, and 22, in long-term cultures of skin fibroblasts and induced pluripotent stem cells (iPSCs) by GTG karyotyping and aCGH. Ring chromosome loss and secondary aberrations were observed in all fibroblast cultures except for r(18). We found monosomy, fragmentation, and translocation of indexed chromosomes. In iPSCs, aCGH revealed striking differences in mitotic stability both between iPSC lines with different rings and, in some cases, between cell lines with the same ring chromosome. We registered the spontaneous rescue of karyotype 46,XY,r(8) to 46,XY in all six iPSC lines through ring chromosome loss and intact homologue duplication with isoUPD(8)pat occurrence, as proven by SNP genotype distribution analysis. In iPSCs with other ring chromosomes, karyotype correction was not observed. Our results suggest that spontaneous correction of the karyotype with ring chromosomes in iPSCs is not universal and that pluripotency is compatible with a wide range of derivative karyotypes. We conclude that marked variability in the frequency of secondary rearrangements exists in both fibroblast and iPSC cultures, expanding the clinical significance of the constitutional ring chromosome.

A mechanical non-enzymatic method for isolation of mouse embryonic fibroblasts

Mouse embryonic fibroblasts (MEFs) accessibility coupled with their simple generation make them as a typical embryonic cell model and feeder layer for in vitro expansion of pluripotent stem cells (PSCs). In this study, a mechanical isolation technique was adopted to isolate MEFs and the efficiency of this technique was compared with enzymatic digestion method. The suspended MEFs were prepared either by mechanical method or 0.25% trypsin enzymatic digestion. The effect of tissue processing on cell apoptosis/necrosis, morphology, viable cell yield, population doubling time, surface marker expression, and the capacity to support PSCs were determined. The mechanical method yielded a significantly higher number of viable cells. However, it showed similar morphology and proliferation characteristics as compared to enzymatic digestion. The mechanical method induced slight apoptosis in MEFs; however, it did not exert the necrotic effect of trypsinization. Treatment of tissue slurry with trypsin solution caused cell lysis and subsequently cell clump formation. Mechanically isolated cells exhibited a higher expression of the MEF surface antigens Sca1, CD106, and CD105. The PSCs on mechanically isolated MEFs displayed a higher expression of pluripotency genes, and formed more compact colonies with a stronger tendency to crowding compared with those cultured on cells isolated by enzymatic digestion. The mechanical method based on tissue inter-syringe processing is relatively a rapid and simple method for MEF isolation. Compared to the enzymatic digestion, the cells obtained from this method show higher expression of embryonic fibroblasts markers and a more functional capacity in supporting PSCs culture.

Exosomal LncRNA-NEAT1 derived from MIF-treated mesenchymal stem cells protected against doxorubicin-induced cardiac senescence through sponging miR-221-3p

Background

The chemotherapy drug doxorubicin (Dox) is widely used for treating a variety of cancers. However, its high cardiotoxicity hampered its clinical use. Exosomes derived from stem cells showed a therapeutic effect against Dox-induced cardiomyopathy (DIC). Previous studies reported that exosomes derived from mesenchymal stem cells (MSCs) pretreated with macrophage migration inhibitory factor (MIF) (exosome^MIF) showed a cardioprotective effect through modulating long noncoding RNAs/microRNAs (lncRNAs/miRs). This study aimed to investigate the role of exosome^MIF in the treatment of DIC.

Results

Exosomes were isolated from control MSCs (exosome) and MIF-pretreated MSCs (exosome^MIF). Regulatory lncRNAs activated by MIF pretreatment were explored using genomics approaches. Fluorescence-labeled exosomes were tracked in vitro by fluorescence imaging. In vivo and in vitro, miR-221-3p mimic transfection enforced miR-221-3p overexpression, and senescence-associated β-galactosidase assay was applied to test cellular senescence. Exosomal delivering LncRNA-NEAT1 induced therapeutic effect in vivo was confirmed by echocardiography. It demonstrated that exosomes^MIF recovered the cardiac function and exerted the anti-senescent effect through LncRNA–NEAT1 transfer against Dox. TargetScan and luciferase assay showed that miR-221-3p targeted the Sirt2 3′-untranslated region. Silencing LncRNA–NEAT1 in MSCs, miR-221-3p overexpression or Sirt2 silencing in cardiomyocytes decreased the exosome^MIF-induced anti-senescent effect against Dox.

Conclusions

The results indicated exosome^MIF serving as a promising anti-senescent effector against Dox-induced cardiotoxicity through LncRNA–NEAT1 transfer, thus inhibiting miR-221-3p and leading to Sirt2 activation. The study proposed that exosome^MIF might have the potential to serve as a cardioprotective therapeutic agent during cancer chemotherapy.

Acquisition of chromosome 1q duplication in parental and genome-edited human-induced pluripotent stem cell-derived neural stem cells results in their higher proliferation rate in vitro and in vivo

Objectives

Genetic engineering of human‐induced pluripotent stem cell‐derived neural stem cells (hiPSC‐NSC) may increase the risk of genomic aberrations. Therefore, we asked whether genetic modification of hiPSC‐NSCs exacerbates chromosomal abnormalities that may occur during passaging and whether they may cause any functional perturbations in NSCs in vitro and in vivo.

Materials and Methods

The transgenic cassette was inserted into the AAVS1 locus, and the genetic integrity of zinc‐finger nuclease (ZFN)‐modified hiPSC‐NSCs was assessed by the SNP‐based karyotyping. The hiPSC‐NSC proliferation was assessed in vitro by the EdU incorporation assay and in vivo by staining of brain slices with Ki‐67 antibody at 2 and 8 weeks after transplantation of ZFN‐NSCs with and without chromosomal aberration into the striatum of immunodeficient rats.

Results

During early passages, no chromosomal abnormalities were detected in unmodified or ZFN‐modified hiPSC‐NSCs. However, at higher passages both cell populations acquired duplication of the entire long arm of chromosome 1, dup(1)q. ZNF‐NSCs carrying dup(1)q exhibited higher proliferation rate than karyotypically intact cells, which was partly mediated by increased expression of AKT3 located on Chr1q. Compared to karyotypically normal ZNF‐NSCs, cells with dup(1)q also exhibited increased proliferation in vivo 2 weeks, but not 2 months, after transplantation.

Conclusions

These results demonstrate that, independently of ZFN‐editing, hiPSC‐NSCs have a propensity for acquiring dup(1)q and this aberration results in increased proliferation which might compromise downstream hiPSC‐NSC applications.

Reducing mitomycin-C-induced ROS levels in mouse feeder cells improves induced pluripotent stem cell colony growth

Chemically defined stem cell culture media are often costly, and the use of mitotically arrested mouse embryonic fibroblasts (MEFs) as feeder cells is a popular and cost-efficient way to maintain induced pluripotent stem cells (iPSCs). However, the commonly used mitotic inhibitor mitomycin-C (MMC) is known to cause cellular metabolic stress. Therefore, our aim was to determine whether such stress in feeder cells indirectly affects iPSC growth during coculture. We report that prolonged exposure to MMC causes metabolic stress in MEFs in the form of oxidative dysregulation. Through optimization of MMC exposure time, we show how to effectively arrest MEFs without inducing oxidative stress, thus promoting significantly better colony growth rates (p < 0.05), improved viability and longer periods between passages of iPSCs in coculture.

Alternative Lengthening of Telomeres (ALT) in Tumors and Pluripotent Stem Cells

A telomere consists of repeated DNA sequences (TTAGGG)n as part of a nucleoprotein structure at the end of the linear chromosome, and their progressive shortening induces DNA damage response (DDR) that triggers cellular senescence. The telomere can be maintained by telomerase activity (TA) in the majority of cancer cells (particularly cancer stem cells) and pluripotent stem cells (PSCs), which exhibit unlimited self-proliferation. However, some cells, such as telomerase-deficient cancer cells, can add telomeric repeats by an alternative lengthening of the telomeres (ALT) pathway, showing telomere length heterogeneity. In this review, we focus on the mechanisms of the ALT pathway and potential clinical implications. We also discuss the characteristics of telomeres in PSCs, thereby shedding light on the therapeutic significance of telomere length regulation in age-related diseases and regenerative medicine.

Potential use of stem cells for fertility preservation

BACKGROUND

Infertility and gonadal dysfunction can result from gonadotoxic therapies, environmental exposures, aging, or genetic conditions. In men, non-obstructive azoospermia (NOA) results from defects in the spermatogenic process that can be attributed to spermatogonial stem cells (SSC) or their niche, or both. While assisted reproductive technologies and sperm banking can enable fertility preservation (FP) in men of reproductive age who are at risk for infertility, FP for pre-pubertal patients remains experimental. Therapeutic options for NOA are limited. The rapid advance of stem cell research and of gene editing technologies could enable new FP options for these patients. Induced pluripotent stem cells (iPSC), SSC, and testicular niche cells, as well as mesenchymal stromal cells (aka medicinal signaling cells, MSCs), have been investigated for their potential use in male FP strategies.

OBJECTIVE

Here, we review the benefits and challenges for three types of stem cell-based approaches under investigation for male FP, focusing on the role that promising sources of MSC derived from human umbilical cord, specifically human umbilical cord perivascular cells (HUCPVC), could fulfill. These approaches are as follows: 1. isolation and ex vivo expansion of autologous SSC for in vivo transplantation or in vitro spermatogenesis; 2. in vitro differentiation toward germ cell and testicular somatic cell lineages using autologous SSC, or stem cells such iPSC or MSC; and 3. protection or regeneration of the spermatogenic niche after gonadotoxic insults in vivo.

CONCLUSION

Our studies suggest that HUCPVC are promising sources of cells that could be utilized in multiple aspects of male FP strategies.

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline Alters Autophagosome Maturation, Cellular Lipidomic Profiles, and Expression of Core Pluripotent Factors

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), one of the most abundant heterocyclic aromatic amines (HAAs) found in the human diet, is primarily produced during high-temperature meat or fish cooking. While MeIQx has been investigated as a potential carcinogen, the cytotoxicity and related molecular mechanisms remain unclear. Here, we demonstrate that autophagosome maturation is blocked by MeIQx. Mechanistically, MeIQx inhibits acidification of lysosomes rather than prevents autophagosome-lysosome fusion. Moreover, cellular lipid profiles are altered by MeIQx treatment. Notably, many phospholipids and sphingolipids are significantly upregulated after exposure to MeIQx. Furthermore, MeIQx decreases expression of pluripotency-associated proteins in mouse embryonic stem cells (ESCs). Together, MeIQx blocks autophagosome maturation through inhibiting acidification of lysosomes, alters lipid metabolism, and decreases expression of pluripotent factors. Our studies provide more cytotoxic evidence and elucidate related mechanisms on the risk of HAA exposure and are expected to promote supervision of food safety and human health.

A novel member of Prame family, Gm12794c, counteracts retinoic acid differentiation through the methyltransferase activity of PRC2

Embryonic stem cells (ESCs) fluctuate among different levels of pluripotency defined as metastates. Sporadically, metastable cellular populations convert to a highly pluripotent metastate that resembles the preimplantation two-cell embryos stage (defined as 2C stage) in terms of transcriptome, DNA methylation, and chromatin structure. Recently, we found that the retinoic acid (RA) signaling leads to a robust increase of cells specifically expressing 2C genes, such as members of the Prame family. Here, we show that Gm12794c, one of the most highly upregulated Prame members, and previously identified as a key player for the maintenance of pluripotency, has a functional role in conferring ESCs resistance to RA signaling. In particular, RA-dependent expression of Gm12794c induces a ground state-like metastate, as evaluated by activation of 2C-specific genes, global DNA hypomethylation and rearrangement of chromatin similar to that observed in naive totipotent preimplantation epiblast cells and 2C-like cells. Mechanistically, we demonstrated that Gm12794c inhibits Cdkn1A gene expression through the polycomb repressive complex 2 (PRC2) histone methyltransferase activity. Collectively, our data highlight a molecular mechanism employed by ESCs to counteract retinoic acid differentiation stimuli and contribute to shed light on the molecular mechanisms at grounds of ESCs naive pluripotency-state maintenance.

Ageing and sources of transcriptional heterogeneity

Cellular heterogeneity is an important contributor to biological function and is employed by cells, tissues and organisms to adapt, compensate, respond, defend and/or regulate specific processes. Research over the last decades has revealed that transcriptional noise is a major driver for cell-to-cell variability. In this review we will discuss sources of transcriptional variability, in particular bursting of gene expression and how it could contribute to cellular states and fate decisions. We will highlight recent developments in single cell sequencing technologies that make it possible to address cellular heterogeneity in unprecedented detail. Finally, we will review recent literature, in which these new technologies are harnessed to address pressing questions in the field of ageing research, such as transcriptional noise and cellular heterogeneity in the course of ageing.

Follistatin-like 1 protects mesenchymal stem cells from hypoxic damage and enhances their therapeutic efficacy in a mouse myocardial infarction model

BACKGROUND

Cell therapy remains the most promising approach against ischemic heart injury. However, poor survival of engrafted cells in ischemic sites diminishes its therapeutic efficacy. Follistatin-like 1 (Fstl1) is documented as a novel pro-survival cardiokine for cardiomyocytes, and it is protective during ischemic heart injury. In the present study, we characterize the potential of Fstl1 as an effective strategy to enhance hypoxia resistance of donor cells and optimize stem cell-based therapy.

METHODS

Murine bone marrow-derived mesenchymal stem cells (MSCs) were expanded in monolayer culture and characterized by flow cytometry. MSCs were subjected to hypoxia to mimic cardiac ischemic environment. Expression of Fstl1 was monitored 0, 24, and 48 h following hypoxia. Constitutive expression of Fstl1 in MSCs was achieved by lentivirus-mediated Fstl1 overexpression. Genetically modified MSCs were further collected for cell death and proliferation assay following 48 h of hypoxic treatment. Acute myocardial infarction (MI) model was created by ligating the left anterior descending coronary artery, while control MSCs (MSCs-mCherry) or Fstl1-overexpressing MSCs (MSCs-Fstl1) were injected into the peri-infarct zone simultaneously. Subsequently, retention of the donor cells was evaluated on post-therapy 1, 3, & 7 days. Finally, myocardial function, infarct size, inflammation, and neovascularization of the infarcted hearts were calculated thereafter.

RESULTS

Expression of Fstl1 in hypoxic MSCs declines dramatically in a time-dependent manner. In vitro study further demonstrated that Fstl1 promotes survival and proliferation of hypoxic MSCs. Moreover, Fstl1 significantly prolongs MSC survival/retention after implantation. Finally, transplantation with Fstl1-overexpressing MSCs significantly improves post-MI cardiac function by limiting scar formation, reducing inflammatory response, and enhancing neovascularization.

CONCLUSIONS

Our results suggest Fstl1 is an intrinsic cardiokine promoting survival and proliferation of MSCs, thereby optimizing their engraftment and therapeutic efficacy during cell therapy.