Culture system for rodent and human oligodendrocyte specification, lineage progression, and maturation

The use of a SOX10 reporter toward ameliorating oligodendrocyte lineage differentiation from human induced pluripotent stem cells

Oligodendrocytes (OLs) are key players in the central nervous system, critical for the formation and maintenance of the myelin sheaths insulating axons, ensuring efficient neuronal communication. In the last decade, the use of human induced pluripotent stem cells (iPSCs) has become essential for recapitulating and understanding the differentiation and role of OLs in vitro. Current methods include overexpression of transcription factors for rapid OL generation, neglecting the complexity of OL lineage development. Alternatively, growth factor-based protocols offer physiological relevance but struggle with efficiency and cell heterogeneity. To address these issues, we created a novel SOX10-P2A-mOrange iPSC reporter line to track and purify oligodendrocyte precursor cells. Using this reporter cell line, we analyzed an existing differentiation protocol and shed light on the origin of glial cell heterogeneity. Additionally, we have modified the differentiation protocol, toward enhancing reproducibility, efficiency, and terminal maturity. Our approach not only advances OL biology but also holds promise to accelerate research and translational work with iPSC-derived OLs.

Isolation and Propagation of Primary Human and Rodent Embryonic Neural Progenitor Cells and Cortical Neurons

The research on human neural progenitor cells holds great potential for the understanding of the molecular programs that control differentiation of cells of glial and neuronal lineages, as well as pathogenetic mechanisms of neurological diseases. Stem cell technologies also provide opportunities for the pharmaceutical industry to develop new approaches for regenerative medicine. Here, we describe the protocol for the isolation and maintenance of neural progenitor cells and cortical neurons using human fetal brain tissue. This protocol can be successfully adapted for the preparation of rodent neural and oligodendrocyte progenitor cells. While several methods for isolating neural and oligodendrocyte progenitors from rodent brain tissue have been described, including techniques utilizing gene transfer and magnetic resonance beads, few methods are specifically focused on deriving human oligodendrocyte progenitor cells. Development of the human cultures provides the most physiologically relevant system for investigating mechanisms which regulate the function of oligodendrocytes, specifically of human origin.

Phosphodiesterase 10A Inhibition Leads to Brain Region-Specific Recovery Based on Stroke Type

Stroke is the leading cause of adult disability. Recovery of function after stroke involves signaling events that are mediated by cAMP and cGMP pathways, such as axonal sprouting, neurogenesis, and synaptic plasticity. cAMP and cGMP are degraded by phosphodiesterases (PDEs), which are differentially expressed in brain regions. PDE10A is highly expressed in the basal ganglia/striatum. We tested a novel PDE10A inhibitor (TAK-063) for its effects on functional recovery. Stroke was produced in mice in the cortex or the striatum. Behavioral recovery was measured to 9 weeks. Tissue outcome measures included analysis of growth factor levels, angiogenesis, neurogenesis, gliogenesis, and inflammation. TAK-063 improved motor recovery after striatal stroke in a dose-related manner, but not in cortical stroke. Recovery of motor function correlated with increases in striatal brain-derived neurotrophic factor. TAK-063 treatment also increased motor system axonal connections. Stroke affects distinct brain regions, with each comprising different cellular and molecular elements. Inhibition of PDE10A improved recovery of function after striatal but not cortical stroke, consistent with its brain localization. This experiment is the first demonstration of brain region-specific enhanced functional recovery after stroke, and indicates that differential molecular signaling between brain regions can be exploited to improve recovery based on stroke subtype.

Oligodendrocytes: Functioning in a Delicate Balance Between High Metabolic Requirements and Oxidative Damage

The study of the metabolic interactions between myelinating glia and the axons they ensheath has blossomed into an area of research much akin to the elucidation of the role of astrocytes in tripartite synapses (Tsacopoulos and Magistretti in J Neurosci 16:877-885, 1996). Still, unlike astrocytes, rich in cytochrome-P450 and other anti-oxidative defense mechanisms (Minn et al. in Brain Res Brain Res Rev 16:65-82, 1991; Wilson in Can J Physiol Pharmacol. 75:1149-1163, 1997), oligodendrocytes can be easily damaged and are particularly sensitive to both hypoxia and oxidative stress, especially during their terminal differentiation phase and while generating myelin sheaths. In the present review, we will focus in the metabolic complexity of oligodendrocytes, particularly during the processes of differentiation and myelin deposition, and with a specific emphasis in the context of oxidative stress and the intricacies of the iron metabolism of the most iron-loaded cells of the central nervous system (CNS).

Simulated microgravity enhances oligodendrocyte mitochondrial function and lipid metabolism

The primary energy sources of mammalian cells are proteins, fats, and sugars that are processed by well-known biochemical mechanisms that have been discovered and studied in 1G (terrestrial gravity). Here we sought to determine how simulated microgravity (sim-µG) impacts both energy and lipid metabolism in oligodendrocytes (OLs), the myelin-forming cells in the central nervous system. We report increased mitochondrial respiration and increased glycolysis 24 hr after exposure to sim-µG. Moreover, examination of the secretome after 3 days' exposure of OLs to sim-µG increased the Krebs cycle (Krebs and Weitzman, ) flux in sim-µG. The secretome study also revealed a significant increase in the synthesis of fatty acids and complex lipids such as 1,2-dipalmitoyl-GPC (5.67); lysolipids like 1-oleoyl-GPE (4.48) were also increased by microgravity. Although longer-chain lipids were not observed in this study, it is possible that at longer time points OLs would have continued moving forward toward the synthesis of lipids that constitute myelin. For centuries, basic developmental biology research has been the pillar of an array of discoveries that have led to clinical applications; we believe that studies using microgravity will open new avenues to our understanding of the brain in health and disease-in particular, to the discovery of new molecules and mechanisms impossible to unveil while in 1G. © 2016 Wiley Periodicals, Inc.

Efficient Generation of Viral and Integration-Free Human Induced Pluripotent Stem Cell-Derived Oligodendrocytes

Here we document three highly reproducible protocols: (1) a culture system for the derivation of human oligodendrocytes (OLs) from human induced pluripotent stem cells (hiPS) and their further maturation-our protocol generates viral- and integration-free OLs that efficiently commit and move forward in the OL lineage, recapitulating all the steps known to occur during in vivo development; (2) a method for the isolation, propagation and maintenance of neural stem cells (NSCs); and (3) a protocol for the production, isolation, and maintenance of OLs from perinatal rodent and human brain-derived NSCs. Our unique culture systems rely on a series of chemically defined media, specifically designed and carefully characterized for each developmental stage of OL as they advance from OL progenitors to mature, myelinating cells. We are confident that these protocols bring our field a step closer to efficient autologous cell replacement therapies and disease modeling. © 2016 by John Wiley & Sons, Inc.

Shh Signaling through the Primary Cilium Modulates Rat Oligodendrocyte Differentiation

Primary Cilia (PC) are a very likely place for signal integration where multiple signaling pathways converge. Two major signaling pathways clearly shown to signal through the PC, Sonic Hedgehog (Shh) and PDGF-Rα, are particularly important for the proliferation and differentiation of oligodendrocytes, suggesting that their interaction occurs in or around this organelle. We identified PC in rat oligodendrocyte precursor cells (OPCs) and found that, while easily detectable in early OPCs, PC are lost as these cells progress to terminal differentiation. We confirmed the interaction between these pathways, as cyclopamine inhibition of Hedgehog function impairs both PDGF-mediated OPC proliferation and Shh-dependent cell branching. However, we failed to detect PDGF-Rα localization into the PC. Remarkably, ciliobrevin-mediated disruption of PC and reduction of OPC process extension was counteracted by recombinant Shh treatment, while PDGF had no effect. Therefore, while PDGF-Rα-dependent OPC proliferation and survival most probably does not initiate at the PC, still the integrity of this organelle and cilium-centered pathway is necessary for OPC survival and differentiation.

Impact of simulated microgravity on oligodendrocyte development: implications for central nervous system repair

We have recently established a culture system to study the impact of simulated microgravity on oligodendrocyte progenitor cells (OPCs) development. We subjected mouse and human OPCs to a short exposure of simulated microgravity produced by a 3D-Clinostat robot. Our results demonstrate that rodent and human OPCs display enhanced and sustained proliferation when exposed to simulated microgravity as assessed by several parameters, including a decrease in the cell cycle time. Additionally, OPC migration was examined in vitro using time-lapse imaging of cultured OPCs. Our results indicated that OPCs migrate to a greater extent after stimulated microgravity than in normal conditions, and this enhanced motility was associated with OPC morphological changes. The lack of normal gravity resulted in a significant increase in the migration speed of mouse and human OPCs and we found that the average leading process in migrating bipolar OPCs was significantly longer in microgravity treated cells than in controls, demonstrating that during OPC migration the lack of gravity promotes leading process extension, an essential step in the process of OPC migration. Finally, we tested the effect of simulated microgravity on OPC differentiation. Our data showed that the expression of mature oligodendrocyte markers was significantly delayed in microgravity treated OPCs. Under conditions where OPCs were allowed to progress in the lineage, simulated microgravity decreased the proportion of cells that expressed mature markers, such as CC1 and MBP, with a concomitant increased number of cells that retained immature oligodendrocyte markers such as Sox2 and NG2. Development of methodologies aimed at enhancing the number of OPCs and their ability to progress on the oligodendrocyte lineage is of great value for treatment of demyelinating disorders. To our knowledge, this is the first report on the gravitational modulation of oligodendrocyte intrinsic plasticity to increase their progenies.

Isolation and propagation of primary human and rodent embryonic neural progenitor cells and cortical neurons

The research on human neural progenitor cells holds great potential for the understanding the molecular programs that control differentiation of cells of glial and neuronal lineages and pathogenetic mechanisms of neurological diseases. Stem cell technologies provide also opportunities for pharmaceutical industry to develop new approaches for regenerative medicine. Here we describe the protocol for isolation and maintenance of neural progenitor cells and cortical neurons using human fetal brain tissue. This protocol can be successfully adapted for preparation of rodent neural and oligodendrocyte progenitor cells. While several methods for isolation of neural and oligodendrocyte progenitors from rodent brain tissue have been described, including techniques which use gene transfer and magnetic resonance beads, few methods are focused on derivation of human oligodendrocyte progenitor cells. Development of human culture provides the most physiologically relevant system for investigation of mechanisms which regulate function of oligodendrocyte, specifically of human origin.

Polyomavirus JC infection inhibits differentiation of oligodendrocyte progenitor cells

Reactivation of the human polyomavirus JC (JCV) in the CNS results in a fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). The lytic destruction of oligodendrocytes, which occurs at the terminal stage of the viral infection cycle, is considered a critical factor in the development of demyelination and the pathogenesis of PML. However, knowledge is limited about interaction of JCV with oligodendrocytes and its impact on the denudation of axons at the early stage of viral reactivation and prior to the destruction of the infected cells. We have developed an in vitro neuroprogenitor cell culture using human fetal brain that can be differentiated to the oligodendrocyte lineage to investigate interactions of JCV with its host cells. Results show that infection with JCV delays oligodendrocyte maturation as shown by reduced levels of oligodendrocytic markers, including myelin basic protein, proteolipid protein, and platelet-derived growth factor receptor-α. Furthermore, replication of JCV in these cells caused substantial dysregulation of several chemokines, including CCL5/RANTES, GRO, CXCL1/GROα, CXCL16, CXCL8/IL-8, CXCL5/ENA-78, and CXCL10/IP-10, all of which play a role in cell growth and differentiation.

Imaging analysis of neuron to glia interaction in microfluidic culture platform (MCP)-based neuronal axon and glia co-culture system

Proper neuron to glia interaction is critical to physiological function of the central nervous system (CNS). This bidirectional communication is sophisticatedly mediated by specific signaling pathways between neuron and glia(1,2) . Identification and characterization of these signaling pathways is essential to the understanding of how neuron to glia interaction shapes CNS physiology. Previously, neuron and glia mixed cultures have been widely utilized for testing and characterizing signaling pathways between neuron and glia. What we have learned from these preparations and other in vivo tools, however, has suggested that mutual signaling between neuron and glia often occurred in specific compartments within neurons (i.e., axon, dendrite, or soma)(3). This makes it important to develop a new culture system that allows separation of neuronal compartments and specifically examines the interaction between glia and neuronal axons/dendrites. In addition, the conventional mixed culture system is not capable of differentiating the soluble factors and direct membrane contact signals between neuron and glia. Furthermore, the large quantity of neurons and glial cells in the conventional co-culture system lacks the resolution necessary to observe the interaction between a single axon and a glial cell. In this study, we describe a novel axon and glia co-culture system with the use of a microfluidic culture platform (MCP). In this co-culture system, neurons and glial cells are cultured in two separate chambers that are connected through multiple central channels. In this microfluidic culture platform, only neuronal processes (especially axons) can enter the glial side through the central channels. In combination with powerful fluorescent protein labeling, this system allows direct examination of signaling pathways between axonal/dendritic and glial interactions, such as axon-mediated transcriptional regulation in glia, glia-mediated receptor trafficking in neuronal terminals, and glia-mediated axon growth. The narrow diameter of the chamber also significantly prohibits the flow of the neuron-enriched medium into the glial chamber, facilitating probing of the direct membrane-protein interaction between axons/dendrites and glial surfaces.

Colloids as mobile substrates for the implantation and integration of differentiated neurons into the mammalian brain

Neuronal degeneration and the deterioration of neuronal communication lie at the origin of many neuronal disorders, and there have been major efforts to develop cell replacement therapies for treating such diseases. One challenge, however, is that differentiated cells are challenging to transplant due to their sensitivity both to being uprooted from their cell culture growth support and to shear forces inherent in the implantation process. Here, we describe an approach to address these problems. We demonstrate that rat hippocampal neurons can be grown on colloidal particles or beads, matured and even transfected in vitro, and subsequently transplanted while adhered to the beads into the young adult rat hippocampus. The transplanted cells have a 76% cell survival rate one week post-surgery. At this time, most transplanted neurons have left their beads and elaborated long processes, similar to the host neurons. Additionally, the transplanted cells distribute uniformly across the host hippocampus. Expression of a fluorescent protein and the light-gated glutamate receptor in the transplanted neurons enabled them to be driven to fire by remote optical control. At 1-2 weeks after transplantation, calcium imaging of host brain slice shows that optical excitation of the transplanted neurons elicits activity in nearby host neurons, indicating the formation of functional transplant-host synaptic connections. After 6 months, the transplanted cell survival and overall cell distribution remained unchanged, suggesting that cells are functionally integrated. This approach, which could be extended to other cell classes such as neural stem cells and other regions of the brain, offers promising prospects for neuronal circuit repair via transplantation of in vitro differentiated, genetically engineered neurons.

Human induced pluripotent stem cells differentiation into oligodendrocyte progenitors and transplantation in a rat model of optic chiasm demyelination

Background

This study aims to differentiate human induced pluripotent stem cells (hiPSCs) into oligodendrocyte precursors and assess their recovery potential in a demyelinated optic chiasm model in rats.

Methodology/Principal Findings

We generated a cell population of oligodendrocyte progenitors from hiPSCs by using embryoid body formation in a defined medium supplemented with a combination of factors, positive selection and mechanical enrichment. Real-time polymerase chain reaction and immunofluorescence analyses showed that stage-specific markers, Olig2, Sox10, NG2, PDGFRα, O4, A2B5, GalC, and MBP were expressed following the differentiation procedure, and enrichment of the oligodendrocyte lineage. These results are comparable with the expression of stage-specific markers in human embryonic stem cell-derived oligodendrocyte lineage cells. Transplantation of hiPSC-derived oligodendrocyte progenitors into the lysolecithin-induced demyelinated optic chiasm of the rat model resulted in recovery from symptoms, and integration and differentiation into oligodendrocytes were detected by immunohistofluorescence staining against PLP and MBP, and measurements of the visual evoked potentials.

Conclusions/Significance

These results showed that oligodendrocyte progenitors generated efficiently from hiPSCs can be used in future biomedical studies once safety issues have been overcome.

Quantitative temporal proteomic analysis of human embryonic stem cell differentiation into oligodendrocyte progenitor cells

Oligodendrocytes (OLs) are glial cells of the central nervous system, which produce myelin. Cultured OLs provide immense therapeutic opportunities for treating a variety of neurological conditions. One of the most promising sources for such therapies is human embryonic stem cells (ESCs) as well as providing a model to study human OL development. For these purposes, an investigation of proteome level changes is critical for understanding the process of OL differentiation. In this report, an iTRAQ-based quantitative proteomic approach was used to study multiple steps during OL differentiation including neural progenitor cells, glial progenitor cells and oligodendrocyte progenitor cells (OPCs) compared to undifferentiated ESCs. Using a 1% false discovery rate cutoff, ∼3145 proteins were quantitated and several demonstrated progressive stage-specific expression. Proteins such as transferrin, neural cell adhesion molecule 1, apolipoprotein E and wingless-related MMTV integration site 5A showed increased expression from the neural progenitor cell to the OPC stage. Several proteins that have demonstrated evidence or been suspected in OL maturation were also found upregulated in OPCs including fatty acid-binding protein 4, THBS1, bone morphogenetic protein 1, CRYAB, transferrin, tenascin C, COL3A1, TGFBI and EPB41L3. Thus, by providing the first extensive proteomic profiling of human ESC differentiation into OPCs, this study provides many novel proteins that are potentially involved in OL development.

Fibroblast growth factor signaling is required for the generation of oligodendrocyte progenitors from the embryonic forebrain

Fibroblast growth factors (FGFs) comprise a family of developmental regulators implicated in a wide variety of neurological functions. FGF receptors 1, 2, and 3 (Fgfrs) are expressed in the embryonic forebrain, including regions overlapping with ventral sites of oligodendrocyte progenitor (OLP) generation. Although FGF signaling is known to influence the proliferation of OLPs in vitro, functions of different Fgfrs in vivo are lacking. Here, we examined single and double mutants with conditional disruption of Fgfrs, specifically in the embryonic forebrain, to investigate the effect of FGFs on the generation and proliferation of OLPs in vivo. FGF signaling, through cooperation between Fgfr1 and Fgfr2 but not Fgfr3, is required for the initial generation of OLPs in the mouse ventral forebrain, with Fgfr1 being a stronger inducer than Fgfr2. In cultures derived from embryonic mutant forebrains or from normal forebrains grown in the presence of Fgfr inhibitor, a strong attenuation of OLP generation was observed, supporting the role of FGF signaling in vivo. Contrary to in vitro findings, Fgfr1 and Fgfr2 signaling is not required for the proliferation of OLPs in vivo. Finally, failure of OLP generation in the Fgfr mutants occurred without loss of sonic hedgehog (Shh) signaling; and pharmacological inhibition of either Fgfr or hedgehog signaling in parallel cultures strongly inhibited OLP generation, suggesting that Fgfrs cooperate with Shh to generate OLPs. Overall, our results reveal for the first time an essential role of FGF signaling in vivo, where the three Fgfrs differentially control the normal generation of OLPs from the embryonic ventral forebrain.