Differentiation of embryonic stem cells into oligodendrocyte precursors

A review of possible therapies for multiple sclerosis

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system with a wide range of symptoms, like executive function defect, cognitive dysfunction, blurred vision, decreased sensation, spasticity, fatigue, and other symptoms. This neurological disease is characterized by the destruction of the blood-brain barrier, loss of myelin, and damage to neurons. It is the result of immune cells crossing the blood-brain barrier into the central nervous system and attacking self-antigens. Heretofore, many treatments proved that they can retard the progression of the disease even though there is no cure. Therefore, treatments aimed at improving patients' quality of life and reducing adverse drug reactions and costs are essential. In this review, the treatment approaches to alleviate the progress of MS include the following: pharmacotherapy, antibody therapy, cell therapy, gene therapy, and surgery. The current treatment methods of MS are described in terms of the prevention of myelin shedding, the promotion of myelin regeneration, and the protection of neurons.

Sirt2 Regulates Radiation-Induced Injury

Sirtuin 2 (SIRT2) plays a major role in aging, carcinogenesis and neurodegeneration. While it has been shown that SIRT2 is a mediator of stress-induced cell death, the mechanism remains unclear. In this study, we report the role of SIRT2 in mediating radiation-induced cell death and DNA damage using mouse embryonic fibroblasts (MEFs), progenitor cells and tissues from Sirt2 wild-type and genomic knockout mice, and human tumor and primary cell lines as models. The presence of Sirt2 in cells and tissues significantly enhanced the cell's sensitivity to radiation-induced cytotoxicity by delaying the dispersion of radiation-induced γ-H2AX and 53BP1 foci. This enhanced cellular radiosensitivity correlated with reduced expression of pro-survival and DNA repair proteins, and decreased DNA repair capacities involving both homologous repair and non-homologous end joining DNA repair mechanisms compared to those in Sirt2 knockout (KO) and knockdown (KD) phenotypes. Together, these data suggest SIRT2 plays a critical role in mediating the radiation-induced DNA damage response, thus regulating radiation-induced cell death and survival.

Alginate Hydrogel Modified with a Ligand Interacting with α3β1 Integrin Receptor Promotes the Differentiation of 3D Neural Spheroids toward Oligodendrocytes in Vitro

In this study, we established a long-term three-dimensional (3D) culture system by using integrin ligand modified alginate hydrogels to encapsulate and differentiate neural progenitor cells (NPCs) toward oligodendrocyte (OL) lineage cells. The porosity of the hydrogel was optimized by varying the alginate concentrations and then characterized by scanning electronic microscopy (SEM). The surface plasmon resonance (SPR) test was used to confirm the ligand-integrin interactions indicating adherence between the NPC surfaces and the hydrogels. Following encapsulation in the hydrogels, both mouse and human NPC sphere cultures could be maintained up to 90 days. Mouse NPC spheres were differentiated into viable neurons, astrocytes and mature OLs by day 60 in all groups whereas human NPC spheres were differentiated into neurons and later into GFAP positive astrocytes and O4 positive pre-OL within 90 days. The species difference in the timeline of OL development between mouse and human was reflected in this system. The ligand LXY30 interacting with the α3β1 integrin receptor was more effective in promoting the differentiation of hNPCs to OL lineage cells compared with the ligand LXW64 interacting with the αvβ3 integrin receptor, hyaluronic acid interacting with CD44 receptor or without any ligand. This study is the first to differentiate O4⁺ pre-OLs from hNPCs in a LXY30-α3β1 (integrin-ligand) modified alginate 3D hydrogel culture. This 3D platform could serve as a valuable tool in disease modeling, drug discovery, and NPC transplantation.

The Tumor Suppressor CIC Directly Regulates MAPK Pathway Genes via Histone Deacetylation

Oligodendrogliomas are brain tumors accounting for approximately 10% of all central nervous system cancers. CIC is a transcription factor that is mutated in most patients with oligodendrogliomas; these mutations are believed to be a key oncogenic event in such cancers. Analysis of the Drosophila melanogaster ortholog of CIC, Capicua, indicates that CIC loss phenocopies activation of the EGFR/RAS/MAPK pathway, and studies in mammalian cells have demonstrated a role for CIC in repressing the transcription of the PEA3 subfamily of ETS transcription factors. Here, we address the mechanism by which CIC represses transcription and assess the functional consequences of CIC inactivation. Genome-wide binding patterns of CIC in several cell types revealed that CIC target genes were enriched for MAPK effector genes involved in cell-cycle regulation and proliferation. CIC binding to target genes was abolished by high MAPK activity, which led to their transcriptional activation. CIC interacted with the SIN3 deacetylation complex and, based on our results, we suggest that CIC functions as a transcriptional repressor through the recruitment of histone deacetylases. Independent single amino acid substitutions found in oligodendrogliomas prevented CIC from binding its target genes. Taken together, our results show that CIC is a transcriptional repressor of genes regulated by MAPK signaling, and that ablation of CIC function leads to increased histone acetylation levels and transcription at these genes, ultimately fueling mitogen-independent tumor growth.Significance: Inactivation of CIC inhibits its direct repression of MAPK pathway genes, leading to their increased expression and mitogen-independent growth.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/15/4114/F1.large.jpg Cancer Res; 78(15); 4114-25. ©2018 AACR.

High Yield of Adult Oligodendrocyte Lineage Cells Obtained from Meningeal Biopsy

Oligodendrocyte loss can lead to cognitive and motor deficits. Current remyelinating therapeutic strategies imply either modulation of endogenous oligodendrocyte precursors or transplantation of in vitro expanded oligodendrocytes. Cell therapy, however, still lacks identification of an adequate source of oligodendrocyte present in adulthood and able to efficiently produce transplantable cells. Recently, a neural stem cell-like population has been identified in meninges. We developed a protocol to obtain high yield of oligodendrocyte lineage cells from one single biopsy of adult rat meningeal tissue. From 1 cm2 of adult rat spinal cord meninges, we efficiently expanded a homogenous culture of 10 millions of meningeal-derived oligodendrocyte lineage cells in a short period of time (approximately 4 weeks). Meningeal-derived oligodendrocyte lineage cells show typical mature oligodendrocyte morphology and express specific oligodendrocyte markers, such as galactosylceramidase and myelin basic protein. Moreover, when transplanted in a chemically demyelinated spinal cord model, meningeal-derived oligodendrocyte lineage cells display in vivo-remyelinating potential. This oligodendrocyte lineage cell population derives from an accessible and adult source, being therefore a promising candidate for autologous cell therapy of demyelinating diseases. In addition, the described method to differentiate meningeal-derived neural stem cells into oligodendrocyte lineage cells may represent a valid in vitro model to dissect oligodendrocyte differentiation and to screen for drugs capable to promote oligodendrocyte regeneration.

Transplanted miR-219-overexpressing oligodendrocyte precursor cells promoted remyelination and improved functional recovery in a chronic demyelinated model

Oligodendrocyte precursor cells (OPCs) have the ability to repair demyelinated lesions by maturing into myelin-producing oligodendrocytes. Recent evidence suggests that miR-219 helps regulate the differentiation of OPCs into oligodendrocytes. We performed oligodendrocyte differentiation studies using miR-219-overexpressing mouse embryonic stem cells (miR219-mESCs). The self-renewal and multiple differentiation properties of miR219-mESCs were analyzed by the expression of the stage-specific cell markers Nanog, Oct4, nestin, musashi1, GFAP, Tuj1 and O4. MiR-219 accelerated the differentiation of mESC-derived neural precursor cells (NPCs) into OPCs. We further transplanted OPCs derived from miR219-mESCs (miR219-OPCs) into cuprizone-induced chronically demyelinated mice to observe remyelination, which resulted in well-contained oligodendrocyte grafts that migrated along the corpus callosum and matured to express myelin basic protein (MBP). Ultrastructural studies further confirmed the presence of new myelin sheaths. Improved cognitive function in these mice was confirmed by behavioral tests. Importantly, the transplanted miR219-OPCs induced the proliferation of endogenous NPCs. In conclusion, these data demonstrate that miR-219 rapidly transforms mESCs into oligodendrocyte lineage cells and that the transplantation of miR219-OPCs not only promotes remyelination and improves cognitive function but also enhances the proliferation of host endogenous NPCs following chronic demyelination. These results support the potential of a therapeutic role for miR-219 in demyelinating diseases.

In vitro myelin formation using embryonic stem cells

Myelination in the central nervous system is the process by which oligodendrocytes form myelin sheaths around the axons of neurons. Myelination enables neurons to transmit information more quickly and more efficiently and allows for more complex brain functions; yet, remarkably, the underlying mechanism by which myelination occurs is still not fully understood. A reliable in vitro assay is essential to dissect oligodendrocyte and myelin biology. Hence, we developed a protocol to generate myelinating oligodendrocytes from mouse embryonic stem cells and established a myelin formation assay with embryonic stem cell-derived neurons in microfluidic devices. Myelin formation was quantified using a custom semi-automated method that is suitable for larger scale analysis. Finally, early myelination was followed in real time over several days and the results have led us to propose a new model for myelin formation.

Generation and characterization of spiking and nonspiking oligodendroglial progenitor cells from embryonic stem cells

Pluripotent stem cells (PSCs) have been differentiated into oligodendroglial progenitor cells (OPCs), providing promising cell replacement therapies for many central nervous system disorders. Studies from rodents have shown that brain OPCs express a variety of ion channels, and that a subset of brain OPCs express voltage-gated sodium channel (NaV ), mediating the spiking properties of OPCs. However, it is unclear whether PSC-derived OPCs exhibit electrophysiological properties similar to brain OPCs and the role of NaV in the functional maturation of OPCs is unknown. Here, using a mouse embryonic stem cell (mESC) green fluorescent protein (GFP)-Olig2 knockin reporter line, we demonstrated that unlike brain OPCs, all the GFP(+) /Olig2(+) mESC-derived OPCs (mESC-OPCs) did not express functional NaV and failed to generate spikes (hence termed "nonspiking mESC-OPCs"), while expressing the delayed rectifier and inactivating potassium currents. By ectopically expressing NaV 1.2 α subunit via viral transduction, we successfully generated mESC-OPCs with spiking properties (termed "spiking mESC-OPCs"). After transplantation into the spinal cord and brain of myelin-deficient shiverer mice, the spiking mESC-OPCs demonstrated better capability in differentiating into myelin basic protein expressing oligodendrocytes and in myelinating axons in vivo than the nonspiking mESC-OPCs. Thus, by generating spiking and nonspiking mESC-OPCs, this study reveals a novel function of NaV in OPCs in their functional maturation and myelination, and sheds new light on ways to effectively develop PSC-derived OPCs for future clinical applications.

Human embryonic stem cell-derived oligodendrocytes: protocols and perspectives

Oligodendrocytes play a fundamental supportive role in the mammalian central nervous system (CNS) as the myelinating-glial cells. Disruption of fast axonal transport mechanisms can occur as a consequence of mature oligodendrocyte loss following spinal cord injury, stroke, or due to neuroinflammatory conditions, such as multiple sclerosis. As a result of the limited remyelination ability in the CNS after injury or disease, human embryonic stem cells (hESCs) may prove to be a promising option for the generation and replacement of mature oligodendrocytes. Moreover, hESC-derived oligodendrocytes may be experimentally utilized to unravel fundamental questions of oligodendrocyte development, along with their therapeutic potential through growth factor support of axons and neurons. However, an intensive characterization and examination of hESC-derived oligodendrocytes prior to preclinical or clinical trials is required to facilitate greater success in their integration following cellular replacement therapy (CRT). Currently, the protocols utilized to derive oligodendrocytes from hESCs consist of significant variations in culture style, time-length of differentiation, and the provision of growth factors in culture. Further, these differing protocols also report disparate patterns in the expression of oligodendroglial markers by these derived oligodendrocytes, throughout their differentiation in culture. We have comprehensively reviewed the published protocols describing the derivation of oligodendrocytes from hESCs and the studies that examine their efficacy to remyelinate, along with the fundamental issues of their safety as a viable CRT. Additionally, this review will highlight particular issues of concern and suggestions for troubleshooting to provide investigators critical information for the future improvement of establishing in vitro hESC-derived oligodendrocytes.

Drugging Hedgehog: signaling the pathway to translation

First discovered in Drosophila, the Hedgehog signaling pathway controls a wide range of developmental processes and is implicated in a variety of cancers. The success of a screen for chemical modulators of this pathway, published in 2002, opened a new chapter in the quest to translate the results of basic developmental biology research into therapeutic applications. Small molecule pathway agonists are now used to program stem cells, whilst antagonists are proving effective as anti-cancer therapies.

Brain involvement in Alström syndrome

BACKGROUND

Alström Syndrome (AS) is a rare ciliopathy characterized by cone-rod retinal dystrophy, sensorineural hearing loss, obesity, type 2 diabetes mellitus and cardiomyopathy. Most patients do not present with neurological issues and demonstrate normal intelligence, although delayed psychomotor development and psychiatric disorders have been reported. To date, brain Magnetic Resonance Imaging (MRI) abnormalities in AS have not been explored.

METHODS

We investigated structural brain changes in 12 genetically proven AS patients (mean-age 22 years; range: 6-45, 6 females) and 19 matched healthy and positive controls (mean-age 23 years; range: 6-43; 12 females) using conventional MRI, Voxel-Based Morphometry (VBM) and Diffusion Tensor Imaging (DTI).

RESULTS

6/12 AS patients presented with brain abnormalities such as ventricular enlargement (4/12), periventricular white matter abnormalities (3/12) and lacune-like lesions (1/12); all patients older than 30 years had vascular-like lesions. VBM detected grey and white matter volume reduction in AS patients, especially in the posterior regions. DTI revealed significant fractional anisotropy decrease and radial diffusivity increase in the supratentorial white matter, also diffusely involving those regions that appeared normal on conventional imaging. On the contrary, axial and mean diffusivity did not differ from controls except in the fornix.

CONCLUSIONS

Brain involvement in Alström syndrome is not uncommon. Early vascular-like lesions, gray and white matter atrophy, mostly involving the posterior regions, and diffuse supratentorial white matter derangement suggest a role of cilia in endothelial cell and oligodendrocyte function.

Oligodendrocyte progenitor cells derived from mouse embryonic stem cells give rise to type-1 and type-2 astrocytes in vitro

Oligodendrocyte progenitor cells (OPCs) in primary culture can give rise to mature oligodendrocytes and type-2, but not type-1 astrocytes depending on the culture conditions. The OPCs thus are called oligodendrocyte-type-2 astrocyte (O2-A) progenitor cells. Mouse embryonic stem cells (mESCs) have been efficiently differentiated into OPCs; however, the fate plasticity of mESC-derived OPCs is not well characterized. In the present study, using GFP-Olig2 mESC line, we showed that the Olig2(+)/GFP(+)/A2B5(+)/NG2(+) OPCs derived from GFP-Olig2 mESCs can mature into oligodendrocytes when co-cultured with mESC-derived neurons. Interestingly, when induced to astrocytic differentiation by bone morphogenetic protein-4, these mESC-derived OPCs can not only generate type-2 astrocytes, but also type-1 astrocytes. These results challenge the dogma that OPCs in culture can only generate type-2, but not type-1 astrocytes, and support the in vivo finding that during perinatal development, OPCs can give rise to a subset of type-1 astrocytes.

OLIG gene targeting in human pluripotent stem cells for motor neuron and oligodendrocyte differentiation

Pluripotent stem cells can be genetically labeled to facilitate differentiation studies. In this paper, we describe a gene-targeting protocol to knock in a GFP cassette into key gene loci in human pluripotent stem cells (hPSCs), and then use the genetically tagged hPSCs to guide in vitro differentiation, immunocytochemical and electrophysiological profiling and in vivo characterization after cell transplantation. The Olig transcription factors have key roles in the transcription regulatory pathways for the genesis of motor neurons (MNs) and oligodendrocytes (OLs). We have generated OLIG2-GFP hPSC reporter lines that reliably mark MNs and OLs for monitoring their sequential differentiation from hPSCs. The expression of the GFP reporter recapitulates the endogenous expression of OLIG genes. The in vitro characterization of fluorescence-activated cell sorting-purified cells is consistent with cells of the MN or OL lineages, depending on the stages at which they are collected. This protocol is efficient and reliable and usually takes 5-7 months to complete. The genetic tagging-differentiation methodology used herein provides a general framework for similar work for differentiation of hPSCs into other lineages.

Impact of induced pluripotent stem cells on the study of central nervous system disease

The derivation of pluripotent stem cells from somatic tissues has provided researchers with a source of patient-specific stem cells. The potential applications of this technology are truly momentous, and include cellular modeling of disease processes, drug discovery, and cell-based therapy. Here, we review the use of induced pluripotent stem cells (iPSCs) to study CNS disease. Since the iPSC field is still in its infancy, we also discuss some of the challenges that will need to be overcome before the potential of this technology to study and to treat neurological and psychiatric disorders can be fully harnessed.