Immortalization of human neural stem cells with the c-myc mutant T58A

The effects of immortalization on the N-glycome and proteome of CDK4-transformed lung cancer cells

Biological experiments are often conducted in vitro using immortalized cells due to their accessibility and ease of propagation compared to primary cells and live animals. However, immortalized cells may present different proteomic and glycoproteomic characteristics from the primary cell source due to the introduction of genes that enhance proliferation (e.g. CDK4) or enable telomere lengthening. To demonstrate the changes in phenotype upon CDK4-transformation, we performed LC-MS/MS glycomic and proteomic characterizations of a human lung cancer primary cell line (DTW75) and a CDK4-transformed cell line (GL01) derived from DTW75. We observed that the primary and CDK4-transformed cells expressed significantly different levels of sialylated, fucosylated, and sialofucosylated N-glycans. Specifically, the primary cells expressed higher levels of hybrid- and complex-type sialylated N-glycans, while CDK4-transformed cells expressed higher levels of complex-type fucosylated and sialofucosylated N-glycans. Further, we compared the proteomic differences between the cell lines and found that CDK4-transformed cells expressed higher levels of RNA-binding and adhesion proteins. Further, we observed that the CDK4-transformed cells changed N-glycosylation after 31 days in cell culture, with a decrease in high-mannose and increase in fucosylated, sialylated, and sialofucosylated N-glycans. Identifying these changes between primary and CDK4-transformed cells will provide useful insight when adapting cell lines that more closely resemble in vivo physiological conditions.

Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention

Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.

Establishment of a fetal cow (Bos Borus) skin fibroblasts cell line with immortalized characterization through human telomerase reverse transcriptase (hTERT) ectopic expression

The ectopic introduction of the human telomerase reverse transcriptase (hTERT) is an effective way to establish an immortalized cell line. Here, hTERT was obtained by RT-PCR, and the eukaryotic expression plasmid and lentivirus shuttle plasmid of hTERT was successfully constructed by the homologous recombination method. The stable expression of hTERT in fetal cow skin fibroblasts (CSF) was established using the lentivirus package system. The hTERT-CSF proliferate and have immortalized characteristics. Meanwhile, the chromosome analysis identified that the number and structure of the hTERT-CSF genome maintain stable. The indirect immunofluorescence, western blot, and flow cytometry showed that the hTERT gene had been successfully integrated into the primary genome of bovine skin and stably expressed. The viral infection experiment first identifies the hTERT-CSF as a vulnerable cell model responding to the Lumpy skin disease virus (LSDV). Establishing hTERT-CSF provides an important cell model for basic and applied research, clinical application, and vaccine development. It provides an essential reference for the future's rapid establishment of other immortalized cell lines.

Stable expression of a truncated TLX variant drives differentiation of induced pluripotent stem cells into self-renewing neural stem cells for production of extracellular vesicles

Background

Neural stem cells (NSCs)-derived extracellular vesicles (EVs) possess great potential in treating severe neurological and cerebrovascular diseases, as they carry the modulatory and regenerative ingredients of NSCs. Induced pluripotent stem cells (iPSCs)-derived NSCs culture represents a sustainable source of therapeutic EVs. However, there exist two major challenges in obtaining a scalable culture of NSCs for high-efficiency EVs production: (1) the heterogeneity of iPSC-derived NSCs culture impairs the production of high-quality EVs and (2) the intrinsic propensity of neuronal or astroglial differentiation of NSCs during prolonged culturing reduces the number of NSCs for preparing EVs. A NSCs strain that is amenable to stable self-renewal and proliferation is thus greatly needed for scalable and long-term culture.

Methods

Various constructs of the genes encoding the orphan nuclear receptor NR2E1 (TLX) were stably transfected in iPSCs, which were subsequently cultured in a variety of differentiation media for generation of iNSCs^TLX. Transcriptomic and biomarker profile of iNSCs^TLX were investigated. In particular, the positivity ratios of Sox2/Nestin and Musashi/Vimentin were used to gauge the homogeneity of the iNSCs^TLX culture. The iNSCs expressing a truncated version of TLX (TLX-TP) was expanded for up to 45 passages, after which its neuronal differentiation potential and EV activity were evaluated.

Results

Stable expression of TLX-TP could confer the iPSCs with rapid and self-driven differentiation into NSCs through stable passaging up to 225 days. The long-term culture of NSCs maintained the highly homogenous expression of NSC-specific biomarkers and potential of neuronal differentiation. EVs harvested from the TLX-expressing NSCs cultures exhibited anti-inflammatory and neuroprotective activities.

Conclusions

iPSC-derived NSCs stably expressing TLX-TP is a promising cell line for scalable production of EVs, which should be further exploited for therapeutic development in neurological treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03131-4.

Generation of High-Yield, Functional Oligodendrocytes from a c-myc Immortalized Neural Cell Line, Endowed with Staminal Properties

Neural stem cells represent a powerful tool to study molecules involved in pathophysiology of Nervous System and to discover new drugs. Although they can be cultured and expanded in vitro as a primary culture, their use is hampered by their heterogeneity and by the cost and time needed for their preparation. Here we report that mes-c-myc A1 cells (A1), a neural cell line, is endowed with staminal properties. Undifferentiated/proliferating and differentiated/non-proliferating A1 cells are able to generate neurospheres (Ns) in which gene expression parallels the original differentiation status. In fact, Ns derived from undifferentiated A1 cells express higher levels of Nestin, Kruppel-like factor 4 (Klf4) and glial fibrillary protein (GFAP), markers of stemness, while those obtained from differentiated A1 cells show higher levels of the neuronal marker beta III tubulin. Interestingly, Ns differentiation, by Epidermal Growth Factors (EGF) and Fibroblast Growth Factor 2 (bFGF) withdrawal, generates oligodendrocytes at high-yield as shown by the expression of markers, Galactosylceramidase (Gal-C) Neuron-Glial antigen 2 (NG2), Receptor-Interacting Protein (RIP) and Myelin Basic Protein (MBP). Finally, upon co-culture, Ns-A1-derived oligodendrocytes cause a redistribution of contactin-associated protein (Caspr/paranodin) protein on neuronal cells, as primary oligodendrocytes cultures, suggesting that they are able to form compact myelin. Thus, Ns-A1-derived oligodendrocytes may represent a time-saving and low-cost tool to study the pathophysiology of oligodendrocytes and to test new drugs.

Transplantation of iPS-Derived Tumor Cells with a Homozygous MHC Haplotype Induces GRP94 Antibody Production in MHC-Matched Macaques

Immune surveillance is a critical component of the antitumor response in vivo, yet the specific components of the immune system involved in this regulatory response remain unclear. In this study, we demonstrate that autoantibodies can mitigate tumor growth in vitro and in vivo We generated two cancer cell lines, embryonal carcinoma and glioblastoma cell lines, from monkey-induced pluripotent stem cells (iPSC) carrying a homozygous haplotype of major histocompatibility complex (MHC, Mafa in Macaca fascicularis). To establish a monkey cancer model, we transplanted these cells into monkeys carrying the matched Mafa haplotype in one of the chromosomes. Neither Mafa-homozygous cancer cell line grew in monkeys carrying the matched Mafa haplotype heterozygously. We detected in the plasma of these monkeys an IgG autoantibody against GRP94, a heat shock protein. Injection of the plasma prevented growth of the tumor cells in immunodeficient mice, whereas plasma IgG depleted of GRP94 IgG exhibited reduced killing activity against cancer cells in vitro These results indicate that humoral immunity, including autoantibodies against GRP94, plays a role in cancer immune surveillance. Cancer Res; 77(21); 6001-10. ©2017 AACR.

IDH-mutant glioma specific association of rs55705857 located at 8q24.21 involves MYC deregulation

The single nucleotide polymorphism rs55705857, located in a non-coding but evolutionarily conserved region at 8q24.21, is strongly associated with IDH-mutant glioma development and was suggested to be a causal variant. However, the molecular mechanism underlying this association has remained unknown. With a case control study in 285 gliomas, 316 healthy controls, 380 systemic cancers, 31 other CNS-tumors, and 120 IDH-mutant cartilaginous tumors, we identified that the association was specific to IDH-mutant gliomas. Odds-ratios were 9.25 (5.17–16.52; 95% CI) for IDH-mutated gliomas and 12.85 (5.94–27.83; 95% CI) for IDH-mutated, 1p/19q co-deleted gliomas. Decreasing strength with increasing anaplasia implied a modulatory effect. No somatic mutations were noted at this locus in 114 blood-tumor pairs, nor was there a copy number difference between risk-allele and only-ancestral allele carriers. CCDC26 RNA-expression was rare and not different between the two groups. There were only minor subtype-specific differences in common glioma driver genes. RNA sequencing and LC-MS/MS comparisons pointed to significantly altered MYC-signaling. Baseline enhancer activity of the conserved region specifically on the MYC promoter and its further positive modulation by the SNP risk-allele was shown in vitro. Our findings implicate MYC deregulation as the underlying cause of the observed association.

Attempts on producing lymphoid cell line from Penaeus monodon by induction with SV40-T and 12S EIA oncogenes

In an attempt of in vitro transformation, transfection mediated expression of Simian virus-40 (T) antigen (SV40-T) and transduction mediated expression of Adenovirus type 12 early region 1A (12S E1A) oncogene were performed in Penaeus monodon lymphoid cells. pSV3-neo vector encoding SV40-T oncogene and a recombinant baculovirus BacP2-12S E1A-GFP encoding 12S E1A oncogene under the control of hybrid promoters were used. Electroporation and lipofection mediated transformation of SV40-T in lymphoid cells confirmed the transgene expression by phenotypic variation and the expression of GFP in co-transfection experiment. The cells transfected by lipofection (≥ 5%) survived for 14 days with lower toxicity (30%), whilst on electroporation, most of the cells succumbed to death (60%) and survived cells lived up to 7 days. Transduction efficiency in primary lymphoid cells was more than 80% within 14 days of post-transduction, however, an incubation period of 7 days post-transduction was observed without detectable expression of 12S E1A. High level of oncogenic 12S E1A expression were observed after 14 day post-transduction and the proliferating cells survived for more than 90 days with GFP expression, however, without in vitro transformation and immortalization. The study put forth the requirement of transduction mediated 'specific' oncogene expression along with telomerase activation and epigenetic induction for the immortalization and establishment of shrimp cell line.

Immortalization of Primary Keratinocytes and Its Application to Skin Research

As a major component of the epidermal tissue, a primary keratinocyte has served as an essential tool not only for the study of pathogenesis of skin-related diseases but also for the assessment of potential toxicities of various chemicals used in cosmetics. However, its short lifespan in ex vivo setting has been a great hurdle for many practical applications. Therefore, a number of immortalization attempts have been made with success to overcome this limitation. In order to understand the immortalization process of a primary keratinocyte, several key biological phenomena governing its lifespan will be reviewed first. Then, various immortalization methods for the establishment of stable keratinocyte cell lines will be explained. Finally, its application to a three-dimensional skin culture system will be described.

Isolation of Human Neural Stem Cells from the Amniotic Fluid with Diagnosed Neural Tube Defects

Human neural stem cells (NSCs) are particularly valuable for the study of neurogenesis process and have a therapeutic potential in treating neurodegenerative disorders. However, current progress in the use of human NSCs is limited due to the available NSC sources and the complicated isolation and culture techniques. In this study, we describe an efficient method to isolate and propagate human NSCs from the amniotic fluid with diagnosed neural tube defects (NTDs), specifically, anencephaly. These amniotic fluid-derived NSCs (AF-NSCs) formed neurospheres and underwent long-term expansion in vitro. In addition, these cells showed normal karyotypes and telomerase activity and expressed NSC-specific markers, including Nestin, Sox2, Musashi-1, and the ATP-binding cassette G2 (ABCG2). AF-NSCs displayed typical morphological patterns and expressed specific markers that were consistent with neurons, astrocytes, oligodendrocytes, and dopaminergic neurons after proper induction conditions. Furthermore, grafted AF-NSCs improved the physiological functions in a rat stroke model. The ability to isolate and bank human NSCs from this novel source provides a unique opportunity for translational studies of neurological disorders.

SOX2 and OCT4 mRNA-expressing cells, detected by molecular beacons, localize to the center of neurospheres during differentiation

Neurospheres are used as in vitro assay to measure the properties of neural stem cells. To investigate the molecular and phenotypic heterogeneity of neurospheres, molecular beacons (MBs) targeted against the stem cell markers OCT4 and SOX2 were designed, and synthesized with a 2'-O-methyl RNA backbone. OCT4 and SOX2 MBs were transfected into human embryonic mesencephalon derived cells, which spontaneously form neurospheres when grown on poly-L-ornitine/fibronectin matrix and medium complemented with bFGF. OCT4 and SOX2 gene expression were tracked in individual cell using the MBs. Quantitative image analysis every day for seven days showed that the OCT4 and SOX2 mRNA-expressing cells clustered in the centre of the neurospheres cultured in differentiation medium. By contrast, cells at the periphery of the differentiating spheres developed neurite outgrowths and expressed the tyrosine hydroxylase protein, indicating terminal differentiation. Neurospheres cultured in growth medium contained OCT4 and SOX2-positive cells distributed throughout the entire sphere, and no differentiating neurones. Gene expression of SOX2 and OCT4 mRNA detected by MBs correlated well with gene and protein expression measured by qRT-PCR and immunostaining, respectively. These experimental data support the theoretical model that stem cells cluster in the centre of neurospheres, and demonstrate the use of MBs for the spatial localization of specific gene-expressing cells within heterogeneous cell populations.

Immortality of cell lines: challenges and advantages of establishment

Cellular immortality happens upon impairment of cell-cycle checkpoint pathways (p53/p16/pRb), reactivation or up-regulation of telomerase enzyme, or upregulation of some oncogenes or oncoproteins leading to a higher rate of cell division.There are also some other factors and mechanisms involved in immortalisation, which need to be discovered. Immortalisation of cells derived from different sources and establishment of immortal cell lines has proven useful in understanding the molecular pathways governing cell developmental cascades in eukaryotic, especially human, cells. After the breakthrough of achieving the immortal cells and understanding their critical importance in the field of molecular biology, intense efforts have been dedicated to establish cell lines useful for elucidating the functions of telomerase, developmental lineage of progenitors, self-renewal potency, cellular transformation, differentiation patterns and some bioprocesses, like odontogenesis. Meanwhile, discovering the exact mechanisms of immortality, a major challenge for science yet, is believed to open new gateways toward understanding and treatment of cancer in the long term. This review summarises the methods involved in establishing immortality, its advantages and the challenges still being faced in this field.

MYC gene delivery to adult mouse utricles stimulates proliferation of postmitotic supporting cells in vitro

The inner ears of adult humans and other mammals possess a limited capacity for regenerating sensory hair cells, which can lead to permanent auditory and vestibular deficits. During development and regeneration, undifferentiated supporting cells within inner ear sensory epithelia can self-renew and give rise to new hair cells; however, these otic progenitors become depleted postnatally. Therefore, reprogramming differentiated supporting cells into otic progenitors is a potential strategy for restoring regenerative potential to the ear. Transient expression of the induced pluripotency transcription factors, Oct3/4, Klf4, Sox2, and c-Myc reprograms fibroblasts into neural progenitors under neural-promoting culture conditions, so as a first step, we explored whether ectopic expression of these factors can reverse supporting cell quiescence in whole organ cultures of adult mouse utricles. Co-infection of utricles with adenoviral vectors separately encoding Oct3/4, Klf4, Sox2, and the degradation-resistant T58A mutant of c-Myc (c-MycT58A) triggered significant levels of supporting cell S-phase entry as assessed by continuous BrdU labeling. Of the four factors, c-MycT58A alone was both necessary and sufficient for the proliferative response. The number of BrdU-labeled cells plateaued between 5–7 days after infection, and then decreased ∼60% by 3 weeks, as many cycling cells appeared to enter apoptosis. Switching to differentiation-promoting culture medium at 5 days after ectopic expression of c-MycT58A temporarily attenuated the loss of BrdU-labeled cells and accompanied a very modest but significant expansion of the sensory epithelium. A small number of the proliferating cells in these cultures labeled for the hair cell marker, myosin VIIA, suggesting they had begun differentiating towards a hair cell fate. The results indicate that ectopic expression of c-MycT58A in combination with methods for promoting cell survival and differentiation may restore regenerative potential to supporting cells within the adult mammalian inner ear.

Isolation of a novel rat neural progenitor clone that expresses Dlx family transcription factors and gives rise to functional GABAergic neurons in culture

Gamma-aminobutyric acid (GABA) ergic interneurons are lost in conditions including epilepsy and central nervous system injury, but there are few culture models available to study their function. Toward the goal of obtaining renewable sources of GABAergic neurons, we used the molecular profile of a functionally incomplete GABAergic precursor clone to screen 17 new clones isolated from GFP(+) rat E14.5 cortex and ganglionic eminence (GE) that were generated by viral introduction of v-myc. The clones grow as neurospheres in medium with FGF2, and after withdrawal of FGF2, they exhibit varying patterns of differentiation. Transcriptional profiling and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) indicated that one clone (GE6) expresses high levels of mRNAs encoding Dlx1, 2, 5, and 6, glutamate decarboxylases, and presynaptic proteins including neuropeptide Y and somatostatin. Protein expression confirmed that GE6 is a progenitor with restricted differentiation giving rise mostly to neurons with GABAergic markers. In cocultures with hippocampal neurons, GE6 neurons became electrically excitable and received both inhibitory and excitatory synapses. After withdrawal of FGF2 in cultures of GE6 alone, neurons matured to express βIII-tubulin, and staining for synaptophysin and vesicular GABA transporter were robust after 1-2 weeks of differentiation. GE6 neurons also became electrically excitable and displayed synaptic activity, but synaptic currents were carried by chloride and were blocked by bicuculline. The results suggest that the GE6 clone, which is ventrally derived from the GE, resembles GABAergic interneuron progenitors that migrate into the developing forebrain. This is the first report of a relatively stable fetal clone that can be differentiated into GABAergic interneurons with functional synapses.

Concise review: self-renewal in the central nervous system: neural stem cells from embryo to adult

The recent discovery of neural stem cells (NSCs) in the adult mammalian brain has fostered a plethora of translational and preclinical studies to investigate future therapeutic approaches for the cure of neurodegenerative diseases. These studies are finally at the clinical stage, and some of them are already under way. The definition of a bona fide stem cell has long been the object of much debate focused on the establishment of standard and univocal criteria to distinguish between stem and progenitor cells. It is commonly accepted that NSCs have to fulfill two basic requirements, the capacity for long-term self-renewal and the potential for differentiation, which account for their physiological role, namely central nervous system tissue homeostasis. Strategies such as immortalization or reprogramming of somatic cells to the embryonic-like stage of pluripotency indicate the relevance of extensive self-renewal ability of NSCs either in vitro or in vivo. Moreover, the discovery of stem-like tumor cells in brain tumors, such as gliomas, accompanied by the isolation of these cells through the same paradigm used for related healthy cells, has provided further evidence of the key role that self-renewal plays in the development and progression of neurodegenerative diseases and cancer. In this review we provide an overview of the current understanding of the self-renewal capacity of nontransformed human NSCs, with or without immortalization or reprogramming, and of stem-like tumor cells, referring to both research and therapeutic studies.

Differential pathotropism of non-immortalized and immortalized human neural stem cell lines in a focal demyelination model

Cell therapy is reaching the stage of phase I clinical trials for post-traumatic, post-ischemic, or neurodegenerative disorders, and the selection of the appropriate cell source is essential. In order to assess the capacity of different human neural stem cell lines (hNSC) to contribute to neural tissue regeneration and to reduce the local inflammation after an acute injury, we transplanted GMP-grade non-immortalized hNSCs and v-myc (v-IhNSC), c-myc T58A (T-IhNSC) immortalized cells into the corpus callosum of adult rats after 5 days from focal demyelination induced by lysophosphatidylcholine. At 15 days from transplantation, hNSC and T-IhNSC migrated to the lesioned area where they promoted endogenous remyelination and differentiated into mature oligodendrocytes, while the all three cell lines were able to integrate in the SVZ. Moreover, where demyelination was accompanied by an inflammatory reaction, a significant reduction of microglial cells' activation was observed. This effect correlated with a differential migratory pattern of transplanted hNSC and IhNSC, significantly enhanced in the former, thus suggesting a specific NSC-mediated immunomodulatory effect on the local inflammation. We provide evidence that, in the subacute phase of a demyelination injury, different human immortalized and non-immortalized NSC lines, all sharing homing to the stem niche, display a differential pathotropism, both through cell-autonomous and non-cell autonomous effects. Overall, these findings promote IhNSC as an inexhaustible cell source for large-scale preclinical studies and non-immortalized GMP grade hNSC lines as an efficacious, safe, and reliable therapeutic tool for future clinical applications.

Genetic modification of human adipose-derived stem cells for promoting wound healing

BACKGROUND

Diverse growth factors secreted from human adipocyte-derived stem cells (hASCs) that support or manage adjacent cells have been studied for therapeutic potentials to a variety of pathological models. However, senescent growth arrest in hASCs during in vitro culture and subsequent defective differentiation potential, have been technical barriers to further genetic modification of hASCs for functional improvement.

OBJECTIVE

We investigated the feasibility of long-term hASC culture to enhance their therapeutic use.

METHODS

We used a MYC variant to generate hASCs expressing v-myc and determined their growth potential and growth factor secretion profile. We further introduced an AKT variant to generate constitutively active (CA)-Akt/v-myc hASCs. Finally, we tested the ability of promoting wound healing of medium conditioned with CA-Akt/v-myc hASCs.

RESULTS

The v-myc hASCs actively proliferated longer than control hASCs. Increased secretion of vascular endothelial growth factor (VEGF) by v-myc hASCs promoted the migration potential of hASCs and vasculogenesis in co-cultured endothelial cells. Additional genetic modification of v-myc hASCs using CA-Akt further increased VEGF secretion. In addition, injection of CA-Akt/v-myc hASCs-CM into wound-mice model promoted wound healing compared to normal hASCs-CM.

CONCLUSION

Genetic modification of hASCs to stimulate secretion of growth factors is a novel strategy to maximize their paracrine effect and improve their therapeutic potential.

Stem cells as a potential therapy for epilepsy

Neural stem cells and neural progenitors (NSC/NPs) hold great promise in neuro-restorative therapy due to their remarkable capacity for self-renewal, plasticity, and ability to integrate into host brain circuitry. Some types of epilepsy would appear to be excellent targets for this type of therapy due to known alterations in local circuitry based on loss or malfunction of specific types of neurons in specific brain structures. Potential sources for NSC/NPs include the embryonic blastocyst, the fetal brain, and adult brain and non-neural tissues. Each of these cell types has potential strengths and weaknesses as candidates for clinical therapeutic agents. This article reviews some of the major types of NSC/NPs and how they have been studied with regard to synaptic integration into host brain circuits. It also reviews how these transplanted cells develop and interact with host brain cells in animal models of epilepsy. The field is still wide open with a number of very promising results but there are also some major challenges that will need to be addressed prior to considering clinical applications for epilepsy.

Hypoxia in the regulation of neural stem cells

In aerobic organisms, oxygen is a critical factor in tissue and organ morphogenesis from embryonic development throughout post-natal life, as it regulates various intracellular pathways involved in cellular metabolism, proliferation, survival and fate. In the mammalian central nervous system, oxygen plays a critical role in regulating the growth and differentiation state of neural stem cells (NSCs), multipotent neuronal precursor cells that reside in a particular microenvironment called the neural stem cell niche and that, under certain physiological and pathological conditions, differentiate into fully functional mature neurons, even in adults. In both experimental and clinical settings, oxygen is one of the main factors influencing NSCs. In particular, the physiological condition of mild hypoxia (2.5-5.0% O(2)) typical of neural tissues promotes NSC self-renewal; it also favors the success of engraftment when in vitro-expanded NSCs are transplanted into brain of experimental animals. In this review, we analyze how O(2) and specifically hypoxia impact on NSC self-renewal, differentiation, maturation, and homing in various in vitro and in vivo settings, including cerebral ischemia, so as to define the O(2) conditions for successful cell replacement therapy in the treatment of brain injury and neurodegenerative diseases.

Isolation of neural stem cells from neural tissues using the neurosphere technique

This unit describes protocols for the derivation, characterization, and expansion of neural stem cell (NSC) lines from the adult mouse subventricular zone (mNSCs), embryonic mouse brain and from the human fetal brain (hNSCs). NSCs can be isolated by enzymatic digestion of specific regions (NSCs niches) of the central nervous system (CNS) and grown in suspension. By using this methodology, NSCs form spherical clusters called neurospheres, which are mechanically dissociated to a single-cell suspension and replated in the selective culture medium. Removal of growth factors and plating cells on an adherent substrate allows cells to differentiate into neurons, astrocytes, and oligodendrocytes, the main cell type of the CNS. Correct culturing of NSCs, according to this methodology, will allow cells to expand over 100 passages without alteration of cell karyotype, growth ability, and differentiation potential.

Reviewing once more the c-myc and Ras collaboration: converging at the cyclin D1-CDK4 complex and challenging basic concepts of cancer biology

The c-myc is a proto-oncogene that manifests aberrant expression at high frequencies in most types of human cancer. C-myc gene amplifications are often observed in various cancers as well. Ample studies have also proved that c-myc has a potent oncogenicity, which can be further enhanced by collaborations with other oncogenes such as Bcl-2 and activated Ras. Studies on the collaborations of c-myc with Ras or other genes in oncogenicity have established several basic concepts and have disclosed their underlying mechanisms of tumor biology, including "immortalization" and "transformation". In many cases, these collaborations may converge at the cyclin D1-CDK4 complex. In the meantime, however, many results from studies on the c-myc, Ras and cyclin D1-CDK4 also challenge these basic concepts of tumor biology and suggest to us that the immortalized status of cells should be emphasized. Stricter criteria and definitions for a malignantly transformed status and a benign status of cells in culture also need to be established to facilitate our study of the mechanisms for tumor formation and to better link up in vitro data with animal results and eventually with human cancer pathology.

The Oncogenic Potential of Mesenchymal Stem Cells in the Treatment of Cancer: Directions for Future Research

Mesenchymal stem cells (MSCs) represent a promising new approach to the treatment of several diseases that are associated with dismal outcomes. These include myocardial damage, graft versus host disease, and possibly cancer. Although the potential therapeutic aspects of MSCs continue to be well-researched, the possible hazards of MSCs, and in particular their oncogenic capacity are poorly understood. This review addresses the oncogenic and tumor-supporting potential of MSCs within the context of cancer treatment. The risk for malignant transformation is discussed for each stage of the clinical lifecycle of MSCs. This includes malignant transformation in vitro during production phases, during insertion of potentially therapeutic transgenes, and finally in vivo via interactions with tumor stroma. The immunosuppressive qualities of MSCs, which may facilitate evasion of the immune system by a tumor, are also addressed. Limitations of the methods employed in clinical trials to date are reviewed, including the absence of long term follow-up and lack of adequate screening methods to detect formation of new tumors. Through discussions of the possible oncogenic and tumor-supporting mechanisms of MSCs, directions for future research are identified which may eventually facilitate the future clinical translation of MSCs for the treatment of cancer and other diseases.

Robust generation of oligodendrocyte progenitors from human neural stem cells and engraftment in experimental demyelination models in mice

BACKGROUND

Cell-based therapy holds great promises for demyelinating diseases. Human-derived fetal and adult oligodendrocyte progenitors (OPC) gave encouraging results in experimental models of dysmyelination but their limited proliferation in vitro and their potential immunogenicity might restrict their use in clinical applications. Virtually unlimited numbers of oligodendroglial cells could be generated from long-term self-renewing human (h)-derived neural stem cells (hNSC). However, robust oligodendrocyte production from hNSC has not been reported so far, indicating the need for improved understanding of the molecular and environmental signals controlling hNSC progression through the oligodendroglial lineage. The aim of this work was to obtain enriched and renewable cultures of hNSC-derived oligodendroglial cells by means of epigenetic manipulation.

METHODOLOGY/PRINCIPAL FINDINGS

We report here the generation of large numbers of hNSC-derived oligodendroglial cells by concurrent/sequential in vitro exposure to combinations of growth factors (FGF2, PDGF-AA), neurotrophins (NT3) and hormones (T3). In particular, the combination FGF2+NT3+PDGF-AA resulted in the maintenance and enrichment of an oligodendroglial cell population displaying immature phenotype (i.e., proliferation capacity and expression of PDGFRalpha, Olig1 and Sox10), limited self-renewal and increased migratory activity in vitro. These cells generate large numbers of oligodendroglial progeny at the early stages of maturation, both in vitro and after transplantation in models of CNS demyelination.

CONCLUSIONS/SIGNIFICANCE

We describe a reliable method to generate large numbers of oligodendrocytes from a renewable source of somatic, non-immortalized NSC from the human foetal brain. We also provide insights on the mechanisms underlying the pro-oligodendrogenic effect of the treatments in vitro and discuss potential issues responsible for the limited myelinating capacity shown by hNSC-derived oligodendrocytes in vivo.

c-MycERTAM transgene silencing in a genetically modified human neural stem cell line implanted into MCAo rodent brain

Background

The human neural stem cell line CTX0E03 was developed for the cell based treatment of chronic stroke disability. Derived from fetal cortical brain tissue, CTX0E03 is a clonal cell line that contains a single copy of the c-mycER^TAM transgene delivered by retroviral infection. Under the conditional regulation by 4-hydroxytamoxifen (4-OHT), c-mycER^TAM enabled large-scale stable banking of the CTX0E03 cells. In this study, we investigated the fate of this transgene following growth arrest (EGF, bFGF and 4-OHT withdrawal) in vitro and following intracerebral implantation into a mid-cerebral artery occluded (MCAo) rat brain. In vitro, 4-weeks after removing growth factors and 4-OHT from the culture medium, c-mycER^TAM transgene transcription is reduced by ~75%. Furthermore, immunocytochemistry and western blotting demonstrated a concurrent decrease in the c-MycER^TAM protein. To examine the transcription of the transgene in vivo, CTX0E03 cells (450,000) were implanted 4-weeks post MCAo lesion and analysed for human cell survival and c-mycER^TAM transcription by qPCR and qRT-PCR, respectively.

Results

The results show that CTX0E03 cells were present in all grafted animal brains ranging from 6.3% to 39.8% of the total cells injected. Prior to implantation, the CTX0E03 cell suspension contained 215.7 (SEM = 13.2) copies of the c-mycER^TAM transcript per cell. After implantation the c-mycER^TAM transcript copy number per CTX0E03 cell had reduced to 6.9 (SEM = 3.4) at 1-week and 7.7 (SEM = 2.5) at 4-weeks. Bisulfite genomic DNA sequencing of the in vivo samples confirmed c-mycER^TAM silencing occurred through methylation of the transgene promoter sequence.

Conclusion

In conclusion the results confirm that CTX0E03 cells downregulated c-mycER^TAM transgene expression both in vitro following EGF, bFGF and 4-OHT withdrawal and in vivo following implantation in MCAo rat brain. The silencing of the c-mycER^TAM transgene in vivo provides an additional safety feature of CTX0E03 cells for potential clinical application.

Transplantation of GABA-producing cells for seizure control in models of temporal lobe epilepsy

A high percentage of patients with temporal lobe epilepsy (TLE) are refractory to conventional pharmacotherapy. The progressive neurodegenerative processes associated with a lifetime of uncontrolled seizures mandate the development of alternative approaches to treat this disease. Transplantation of inhibitory cells has been suggested as a potential therapeutic strategy to achieve seizure suppression in humans with intractable TLE. Preclinical investigations over 20 years have demonstrated that multiple cell types from several sources can produce anticonvulsant, and antiepileptogenic, effects in animal models of TLE. Transplanting GABA-producing cells, in particular, has been shown to reduce seizures in several well-established models. This review addresses experimentation using different sources of transplantable GABAergic cells, highlighting progress with fetal tissue, neural cell lines, and stem cells. Regardless of the source of the GABAergic cells used in seizure studies, common challenges have emerged. Several variables influence the anticonvulsant potential of GABA-producing cells. For example, tissue availability, graft survival, immunogenicity, tumorigenicity, and varying levels of cell migration, differentiation, and integration into functional circuits and the microenvironment provided by sclerotic tissue all contribute to the efficacy of transplanted cells. The challenge of understanding how all of these variables work in concert, in a disease process that has no well-established etiology, suggests that there is still much basic research to be done before rational cell-based therapies can be developed for TLE.