Inhibition of Gli1 Enhances Remyelination Abilities of Endogenous Stem Cell Populations


Nerve cells, otherwise known as neurons, have long extensions called axons. Nerve impulses travel down these axons, away from the cell body towards another neuron that is connected to the neuron. The axons of some neurons are insulated with a special substance called myelin the layer of myelin that surrounds the axon. This “myelin sheath” acts as a protective covering composed of protein and lipids.

myelin_sheath

Axons can vary in length from anywhere to 1 millimeter or less to 1 meter. Sometimes, axons are bundled together to form nerves that transmit electrical nerve impulses across the body.

While myelin protects and insulates axons, it also enhances the speed at which nerve impulses are transmitted through the axon. Axons without myelin sheaths conduct nerve impulses continuously throughout the axon. However, myelinated axons have small, uncovered gaps in the myelin sheath called nodes of Ranvier. Myelinated axons can only conduct nerve impulse at the nodes of Ranvier. Consequently, the nerve impulse jumps from node to node, greatly increasing the speed of nerve impulse conduction.

nodes_of_ranvier

If myelin is damaged, the speed of nerve impulse transmission slows substantially. Multiple sclerosis is one example of a disease that causes systematic loss of the myelin sheath. Inflammatory demyelinating diseases also cause progressive damage and loss of the myelin sheath. Regenerating the myelin sheath in these patients is one of the goals of regenerative medicine.

A good deal of data tells us that endogenous remyelination does occur. Unfortunately, this process is overwhelmed by the degree of demyelination in these diseases. A stem cell population called the parenchymal oligodendrocyte progenitor cells and endogenous adult neural stem cells in the brain are known to remyelinate demyelinated axons.

The Salzer laboratory at the New York Neuroscience Institute examined the ability of a specific adult neural stem cell population to remyelinate axons. These stem cells expressed the transcription factor Gli1.

Salzer and his team showed that this subventricular zone-specific group of neural stem cells were efficiently recruited to demyelinated portions of the brain. This same neural stem cell population was never observed entering healthy axon tracts. This finding shows that these cells seem to specialize in making new myelin sheaths for damaged axon tracts.

Since these neural stem cells expressed Gli1, and since there are drugs that can inhibit Gli1 activity, Salzer’s group wanted to show that Gli1 was a necessary factor for neural stem cell activity. Surprisingly, differentiation of these neural stem cells into oligodendrocytes (which make myelin and remyelinate axons) is significantly enhanced by inhibition of Gli1.

A specific signaling pathway called the hedgehog pathway is known to activate Gli1 and other members of the Gli gene family. However, when the hedgehog pathway in these neural stem cells was completely inhibited, it did not have the same effect and Gli1 inhibition. This suggests that Gli1 is doing more than responding to the hedgehog pathway in these neural stem cells.

Salzer and his colleagues showed that Gli1 inhibition improved myelin deposition in an animal model of experimental autoimmune encephalomyelitis; an inflammatory demyelination disease. Thus, inhibition of Gli1 activity in this preclinical model system increase regeneration of the myelin sheath in demyelinated neurons.

This work elegantly showed that endogenous neural stem cells that can remyelinate axons are present and can be activated by inhibiting Gli1. Furthermore, this activation will nicely enhance the therapeutic capacity of these endogenous cells. This potentially identifies a new therapeutic avenue for the treatment of demyelinating disorders.

This work was published in Nature. 2015 Oct 15;526(7573):448-52. doi: 10.1038/nature14957.

Using Drugs to Stimulate your Own Stem Cells to Treat Multiple Sclerosis


Paul Tesar from Case Western Reserve in Cleveland. Ohio and his colleagues have discovered that two different drugs, miconazole and clobetasol, can reverse the symptoms of multiple sclerosis in laboratory animals. Furthermore, these drugs do so by stimulating the animals’ own native stem cell population that insulates nerves.

Multiple sclerosis (MS) is a member of the “demyelinating disorders.” The cause of MS remains unknown, but all of our available evidence strongly suggests that MS is an autoimmune disease in which the body’s immune system attacks its own tissues. In MS the immune system attacks and destroys myelin — the fatty substance that coats and protects nerve fibers in the brain and spinal cord. We can compare myelin to the insulation that surrounds electrical wires. When myelin is damaged, the nerve impulses that travel along that nerve may be slowed or blocked.

The myelin sheath is made by cells known as “oligodendrocytes,” and oligodendrocytes are derived from a stem cell population known as OPCs, which stands for oligodendrocyte progenitor cells. If this stem cell population could be stimulated, then perhaps the damaged myelin sheath could be repaired and the symptoms of MS ameliorated.

In a paper that appeared in the journal Nature (522, 2015 216-220), Tesar and the members of his research team, and his collaborators used a pluripotent mouse stem cell line and differentiated them into OPCs. Thyroid hormone is a known inducer of OPC differentiation. Therefore, Tesar and others screened a battery of drugs to determine if any of these compounds could induce OPC differentiation as cell as thyroid hormone. From this screen using cultured OPCs, two drugs, the antifungal drug miconazole and clobetasol, a corticosteroid of the glucocorticoid class, proved to do a better job of inducing OPC differentiation than thyroid hormone.

Was this an experimental artifact? Tesar and others devised an ingenious assay to measure the effectiveness of these two drugs. They used brain slices from fetal mice that were taken from animals whose brains had yet to synthesize myelin and applied OPCs to these slices with and without the drugs. With OPCs, no myelin was made because the OPCs did not receive any signal to differentiate into mature oligodendrocytes and synthesize myelin. However in the presence of either miconazole or clobetasol, the OPCs differentiated and successfully myelinated the brain slices.

Experiments in tissue culture are a great start, but do they demonstrate a biological reality within a live animal? To answer this question, Tesar and his crew injected laboratory mice with purified myelin. The immune systems of these mice generated a robust immune response against myelin that eroded the myelin sheath from their nerves. This condition mimics human MS and is called experimental autoimmune encephalitis, and it is an excellent model system for studying MS. When mice with experimental autoimmune encephalitis (EAE) were treated with either miconazole or clobetasol, the EAE mice showed a remarkable reversal of symptoms and a solid attenuation of demyelination. Tissue samples established that these reversals were due to increased OPC activity.

When the mechanisms of these drugs were examined in detail, it became clear that the two drugs worked through distinct biochemical mechanisms. Miconazole, for example, activated the mitogen-activated protein kinase (MAPK) pathway, but clobetasol worked through the glucocorticoid receptor signaling pathway. Both of these signaling pathways converge, however, to increase OPC differentiation.

Both miconazole and clobetasol are only approved for topical administration. However, the fact that these drugs can cross the blood-brain barrier and effect changes in the brain is very exciting. Furthermore, this work establishes the template for screening new compounds that might be efficacious in human patients.

In the meantime, human patients might benefit from a clinical trial that determines if the symptoms and neural damage caused by MS can be reversed by the administration of these drugs or derivatives of these drugs.

Human Stem Cells Repair Radiation Damage in Rat Brains


Radiation is a powerful treatment for brain cancer, but this potentially life-saving treatment comes with a heavy cost, which is permanent damage to the brain.

Preclinical work at Memorial Sloan Kettering Cancer Center has shown that human stem cells can be used to make cells that repair radiation-induced damage in the brain.

When rats were treated with radiation and then given cocktails to the human stem cells, they regained the cognitive and motor functions that were lost after brain irradiation.

In the brain, stem cells called OPCs or oligodendrocyte progenitor cells mature into oligodendrocytes that produce the protective myelin coating that surrounds axons in the central nervous system. During radiation treatment, OPCs die off and are depleted. Because OPCs help shield and repair the myelin sheath throughout the life of the organism, depletion of them threatens the integrity of the myelin sheath, which threatens the proper transmission of neural impulses throughout the brain.

A research project led by neurosurgeon Viviane Tabar and her research associate Jinghua Piao wanted to use stem cells to replace these lost OPCs. They used human embryonic stem cells and human induced pluripotent stem cells to make cultured OPCs.

In the next phase of the experiment, Taba, Piao and their coworkers treated rats whose brains had been irradiated with their cultured OPCs. After injection of the stem cell-derived OPCs, brain repair was evident and the rats regained their cognitive and motor function that they had previously lost as a consequence of radiation exposure.

The treatment appeared quite safe since none of the animals developed any tumors or aberrant growths.

The ability to repair radiation damage could mean that the quality of cancer survivors could be greatly improved and it could also expand the therapeutic window of radiation, according to Tabor.

“This will have to be proven further, but if we can repair the brain effectively, we could be bolder with our radiation dosing, within limits,” said Tabor.

Such a treatment scheme could also be very important in children, for whom physicians must use lower doses of radiation to limit brain damage.

Cells from placentas safe for patients with multiple sclerosis


A new Phase I clinical trial has demonstrated that Multiple Sclerosis (MS) patients were able to safely tolerate treatment with cells cultured from human placental tissue.  The results of this study were recently published in the journal Multiple Sclerosis and Related Disorders.  This pioneering study was conducted by researchers at Mount Sinai, Celgene Cellular Therapeutics, which is a subsidiary of Celgene Corporation, and collaborators at several other institutions, including the Swedish Neuroscience Institute in Seattle, WA, MultiCare Health System-Neuroscience Center of Washington, London Health Sciences Centre at University Hospital in London, the Clinical Neuroscience Research Unit at the University of Minnesota, the University of Colorado Denver, The Ottawa Hospital Multiple Sclerosis Clinic, and the MS Comprehensive Care Center at SUNY.

Even though this clinical trial was designed solely to determine the safety of this treatment, the data collected from the participating patients suggested that a preparation of cultured cells called PDA-001 may repair damaged nerve tissues in patients with MS.  PDA-001 cells resemble “mesenchymal,” stromal stem cells, which are found in many tissues of the body.  However, in this study, the cells were grown in cell culture systems, which means that one donor was able to supply enough cells for several patients.

“This is the first time placenta-derived cells have been tested as a possible therapy for multiple sclerosis,” said Fred Lublin, MD, Director of the Corinne Goldsmith Dickinson Center for Multiple Sclerosis, Professor of Neurology at Icahn School of Medicine at Mount Sinai and the lead investigator of the study. “The next step will be to study larger numbers of MS patients to assess efficacy of the cells, but we could be looking at a new frontier in treatment for the disease.”

MS is a chronic autoimmune disease.  The body’s immune system attacks the insulating myelin sheath that surrounds and protectively coats the nerve fibers in the central nervous system.  The myelin sheath greatly improves the speed at which nerve impulses pass through these nerves and without the myelin sheath, nerve impulse conduction becomes sluggish, and the nerves also eventually die off.  Long-term, MS causes extensive nerve malfunction and can lead to paralysis and blindness.  MS usually begins as an episodic condition called “relapsing-remitting MS” or RRMS.  Patients will have occasional outbreaks of nerve malfunction, pain, or numbness.  However, many MS patients will see their condition evolves into a chronic condition with worsening disability called “secondary progressive MS” or SPMS.

This Phase I trial examined 16 MS patients, 10 of whom had  RRMS and six of whom were diagnosed with SPMS and were between the ages of 18 and 65.  Six patients were given a high dose of the placental-based cell line PDA-001, and another six were given a lower dose.  The remaining four patients were given placebos.  Dr. Lubin noted that alteration of the immune system by any means can cause MS to worsen in some patients.  Therefore, all participating subjects were given monthly brain scans over a six-month period to ensure they did not acquire any new or enlarging brain lesions, which are indicative of worsening MS activity.  However, none of the subjects in this study showed any paradoxical worsening on MRI and after one year.  The majority had stable or improved levels of disability.

“We’re hoping to learn more about how placental stromal cells contribute to myelin repair,” said Dr. Lublin. “We suspect they either convert to a myelin making cell, or they enhance the environment of the area where the damage is to allow for natural repair. Our long-term goal is to develop strategies to facilitate repair of the damaged nervous system.”

One Step Closer To Stem Cell Treatment for Multiple Sclerosis


Valentina Fossati and her colleague Panagiotis Douvaras from the New York Stem Cell Foundation (NYSCF) Research Institute have brought us one step closer to creating a viable stem cell-based therapy for multiple sclerosis from a patient’s own cells.

Valentina Fossati, Ph.D.
Valentina Fossati, Ph.D.

NYSCF scientists have, for the first time, produced induced pluripotent stem cell (iPSCs) lines from skin samples of patients who suffer from primary progressive multiple sclerosis. Fossati, Douvaras and colleagues also developed an accelerated protocol to differentiate iPSCs into oligodendrocytes, which are the myelin-making cells that insulate axons of central nervous system neurons. Destruction of the insulating myelin sheath is one of the hallmarks of multiple sclerosis, and oligodendrocyte progenitor cells or OPCs can replace damaged myelin sheath material.

Previously, producing oligodendrocytes from pluripotent stem cells required almost half a year to produce, which limited research on these cells and the development of treatments. This present study, however, has reduced the time required to make oligodendrocytes by half. This increases the feasibility of making these cells and using them in research and, potentially, for treatments.

Oligodendrocytes

By making oligodendrocytes from multiple sclerosis patients, researchers can use these cells to observe, in a culture dish, how multiple sclerosis develops and progresses. The improved protocol for deriving oligodendrocytes from iPSCs will also provide a platform for disease modeling, drug screening, and for replacing the damaged cells in the brain with healthy cells generated using this method.

“We are so close to finding new treatments and even cures for MS. The enhanced ability to derive the cells implicated in the disease will undoubtedly accelerate research for MS and many other diseases” said Susan L. Solomon, NYSCF Chief Executive Officer.

Valentina Fossati, NYSCF – Helmsley Investigator and senior author on the paper, said, “We believe that this protocol will help the MS field and the larger scientific community to better understand human oligodendrocyte biology and the process of myelination. This is the first step towards very exciting studies: the ability to generate human oligodendrocytes in large amounts will serve as an unprecedented tool for developing remyelinating strategies and the study of patient-specific cells may shed light on intrinsic pathogenic mechanisms that lead to progressive MS.”

NYSCF scientists established in this study that their improved the protocol for making myelin-forming cells worked and that the oligodendrocytes derived from the skin of these patients are functional, and able to form their own myelin when put into a mouse model. This is a definite step towards developing future autologous cell transplantation therapies in multiple sclerosis patients. These results also present new research venues to study multiple sclerosis and other diseases, since oligodendrocytes are implicated in many disorders. Therefore, Fossati and others have not only moved multiple sclerosis research forward, but also research on all demyelinating and central nervous system disorders.

“Oligodendrocytes are increasingly recognized as having an absolutely essential role in the function of the normal nervous system, as well as in the setting of neurodegenerative diseases, such as multiple sclerosis. The new work from the NYSCF Research Institute will help to improve our understanding of these important cells. In addition, being able to generate large numbers of patient-specific oligodendrocytes will support both cell transplantation therapeutics for demyelinating diseases and the identification of new classes of drugs to treat such disorders,” said Dr. Lee Rubin, NYSCF Scientific Advisor and Director of Translational Medicine at the Harvard Stem Cell Institute.

Multiple sclerosis is a chronic, inflammatory, demyelinating disease of the central nervous system, distinguished by recurrent episodes of demyelination and the consequent neurological symptoms. Primary progressive multiple sclerosis is the most severe form of multiple sclerosis, characterized by a steady neurological decline from the onset of the disease. Currently, there are no effective treatments or cures for primary progressive multiple sclerosis and treatments rely merely on symptom management.

Skin Tissue as a Treatment for Multiple Sclerosis


Italian researchers have derived stem cells from skin cells that can reduce the damage to the nervous system cause by a mouse version of multiple sclerosis. This experiment provides further evidence that stem cells from patients might be a feasible source of material to treat their own maladies.

The principal investigators in this work, Cecilia Laterza and Gianvito Martino, are from the San Raffaele Scientific Institute, Milan and the University of Milan, respectively.

Because multiple sclerosis results from the immune system attacking the myelin sheath that surrounds nerves, most treatments for this disease consist of agents that suppress the immune response against the patient’s own nerves. Unfortunately, these treatments have pronounced side effects, and are not effective in the progressive phases of the disease when damage to the myelin sheath might be widespread.

The symptoms of loss of the myelin sheath might one or more of the following: problems with touch or other such things, muscle cramping and muscle spasms, bladder, bowel, and sexual dysfunction, difficulty saying words because of problems with the muscles that help you talk (dysarthria), lack of voluntary coordination of muscle movements (ataxia), and shaking (tremors), facial weakness or irregular twitching of the facial muscles, double vision, heat intolerance, fatigue and dizziness; exertional exhaustion due to disability, pain, or poor attention span, concentration, memory, and judgment.

Clinically, multiple sclerosis is divided into the following categories on the basis of the frequency of clinical relapses, time to disease progression, and size of the lesions observed on MRI.  These classifications are:

A)         Relapsing-remitting MS (RRMS): Approximately 85% of cases and there are two types – Clinically isolated syndrome (CIS): A single episode of neurologic symptoms, and Benign MS or MS with almost complete remission between relapses and little if any accumulation of physical disability over time.

B)         Secondary progressive MS (SPMS)

C)         Primary progressive MS (PPMS)

D)        Progressive-relapsing MS (PRMS)

The treatment of MS has 2 aspects: immunomodulatory therapy (IMT) for the underlying immune disorder and therapies to relieve or modify symptoms.

To treat acute relapses:

A)    Methylprednisolone (Solu-Medrol) can hasten recovery from an acute exacerbation of MS.

B)    Plasma exchange (plasmapheresis) for severe attacks if steroids are contraindicated or ineffective (short-term only).

C)    Dexamethasone is commonly used for acute transverse myelitis and acute disseminated encephalitis.

For relapsing forms of MS, the US Food and Drug Administration (FDA) include the following:

A)    Interferon beta-1a (Avonex, Rebif)

B)    Interferon beta-1b (Betaseron, Extavia)

C)    Glatiramer acetate (Copaxone)

D)    Natalizumab (Tysabri)

E)    Mitoxantrone

F)    Fingolimod (Gilenya)

G)    Teriflunomide (Aubagio)

H)    Dimethyl fumarate (Tecfidera)

For aggressive MS:

A)    High-dose cyclophosphamide (Cytoxan).

B)    Mitoxantrone

In order to treat multiple sclerosis, restoring the damaged myelin sheath is essential for returning patients to their former wholeness.

In this study, this research team reprogrammed mouse skin cells into induced pluripotent skin cells (iPSCs), and then differentiated them into neural stem cells. Neural stem cells can differentiate into any cell type in the central nervous system.

(a) Bright field image of miPSC-NPCs obtained from miPSC Sox2βgeo. Scale bar, 50 μm. (b) GFP expression on miPSC-NPCs upon LV infection. Scale bar, 50 μm. (c–h) Immunostaining for Nestin (c), Vimentin (d), Olig2 (e), Mash1 (f), Sox2 (g) and GLAST (h). Scale bar, 50 μm. (i) Growth curve of miPSC-NPC. (j–l) Differentiation of miPSC-NPCs in three neural-derived cell populations, neurons (j), astrocytes (k) and oligodendrocytes (l). Scale bar, 50 μm. (m–o) Expression of the adhesion molecule CD44 (m), the chemokine receptor CXCR4 (n) and the integrin VLA-4 (o) on in vitro cultured miPSC-NPCs analysed by flow-activated cell sorting (FACS). Grey line represents the isotype control, whereas red line indicates the stained cells.
(a) Bright field image of miPSC-NPCs obtained from miPSC Sox2βgeo. Scale bar, 50 μm. (b) GFP expression on miPSC-NPCs upon LV infection. Scale bar, 50 μm. (c–h) Immunostaining for Nestin (c), Vimentin (d), Olig2 (e), Mash1 (f), Sox2 (g) and GLAST (h). Scale bar, 50 μm. (i) Growth curve of miPSC-NPC. (j–l) Differentiation of miPSC-NPCs in three neural-derived cell populations, neurons (j), astrocytes (k) and oligodendrocytes (l). Scale bar, 50 μm. (m–o) Expression of the adhesion molecule CD44 (m), the chemokine receptor CXCR4 (n) and the integrin VLA-4 (o) on in vitro cultured miPSC-NPCs analysed by flow-activated cell sorting (FACS). Grey line represents the isotype control, whereas red line indicates the stained cells.

Next, Laterza and her colleagues administered these neural stem/progenitor cells “intrathecally,” which simply means that they were injected into the spinal cord underneath the meninges that cover the brain and spinal cord to mice that had a rodent version of multiples sclerosis called EAE or experimental autoimmune encephalomyelitis.

EAE mice are made by injecting them with an extract of myelin sheath. The mouse immune system mounts and immune response against this injected material and attacks the myelin sheath that surrounds the nerves. EAE does not exactly mirror multiple sclerosis in humans, but it comes pretty close. While multiple sclerosis does not usually kill its patients, EAE either kills animals or leaves them with permanent disabilities. Animals with EAE also suffer severe nerve inflammation, which is distinct from multiple sclerosis in humans in which some nerves suffer inflammation and others do not. Finally, the time course of EAE is entirely different from multiple sclerosis. However, both conditions are caused by an immune response against the myelin sheath that strips the myelin sheath from the nerves.

The transplanted neural stem cells reduced the inflammation within the central nervous system. Also, they promoted healing and the production of new myelin. However, most of the new myelin was not made by the injected stem cells. Instead the injected stem cells secreted a compound called “leukemia inhibitory factor” that promotes the survival, differentiation and the remyelination capacity of both internal oligodendrocyte precursors and mature oligodendrocytes (these are the cells that make the myelin sheath). The early preservation of tissue integrity in the spinal cord limited the damage to the blood–brain barrier damage. Damage to the blood-brain barrier allows immune cells to infiltrate the central nervous system and destroy nerves. By preserving the integrity of the blood-brain barrier, the injected neural stem cells prevented infiltration of blood-borne of the white blood cells that are ultimately responsible for demyelination and axonal damage.

(a) EAE clinical score of miPSC-NPC- (black dots) and sham-treated mice (white dots). Each point represents the mean disease score of at least 10 mice per group (±s.e.m.); two-way ANOVA; *P<0.05; **P<0.01. (b) Quantification of spinal cord demyelination and axonal damage at 80 dpi in miPSC-NPC- (black bars) versus sham-treated (white bars) EAE mice (N=6 per group). Data (mean values ±s.e.m.) represent the percentage of damage. Student’s t-test; *P<0.05; **P<0.01. (c,d) Representative images of spinal cord sections stained with Luxol Fast Blue (c) and Bielschowsky (d). Red dotted lines represent areas of damage. Scale bar, 200 μm. (e) Quantitative analysis of the localization of miPSC-NPCs upon transplantation into EAE mice (N=3). (f–k) Immunostaining for CD45, MBP, Nestin, Ki67, Olig2, GFAP, βIII tubulin and GFP shows accumulation of transplanted cells (arrowheads) within perivascular spinal cord damaged areas. Dotted lines represent vessels. Nuclei are visualized with DAPI. Scale bars, 50 μm. (l) Percentage (±s.e.m.) of the miPSC-NPCs expressing the different neural differentiation markers upon transplantation into EAE mice; the majority of transplanted miPSC-NPCs remained undifferentiated. (N=3 mice per group).
(a) EAE clinical score of miPSC-NPC- (black dots) and sham-treated mice (white dots). Each point represents the mean disease score of at least 10 mice per group (±s.e.m.); two-way ANOVA; *P<0.05; **P

“Our discovery opens new therapeutic possibilities for multiple sclerosis patients because it might target the damage to myelin and nerves itself,” said Martino.

Timothy Coetzee, chief research officer of the National Multiple Sclerosis Society, said of this work: “This is an important step for stem cell therapeutics. The hope is that skin or other cells from individuals with MS could one day be used as a source for reparative stem cells, which could then be transplanted back into the patient without the complications of graft rejection.”

Obviously, more work is needed, but this type of research demonstrates the safety and feasibility of regenerative treatments that might help restore lost function.

Martino added, “There is still a long way to go before reaching clinical applications but we are getting there. We hope that our work will contribute to widen the therapeutic opportunities stem cells can offer to patients with multiple sclerosis.”

See Cecilia Laterza, et al. iPSC-derived neural precursors exert a neuroprotective role in immune-mediated demyelination via the secretion of LIF. NATURE COMMUNICATIONS 4, 2597: doi:10.1038/ncomms3597.

Spiking Stem Cells to Generate Myelin


Regenerating damaged nerve tissue represents a unique challenge for regenerative medicine. Nevertheless, some experiments have shown that it is possible to regenerate the myelin sheath that surrounds particular nerves.

Myelin is a fatty, insulating sheath that surrounds particular nerves and accelerates the transmission of nerve impulses. The myelin sheath also helps neurons survive, and the myelin sheath is attacked and removed in multiple sclerosis, a genetic disease called Charcot-Marie-Tooth disease, and spinal cord injuries. Being able to regenerate the myelin sheath is an essential goal of regenerative medicine.

Fortunately, a new study from a team of UC Davis (my alma mater) scientists have brought this goal one step closer. Wenbig Deng, principal investigator of this study and associate professor of biochemistry and molecular medicine, said, “Our findings represent an important conceptual advance in stem cell research. We have bioengineered the first generation of myelin-producing cells with superior regenerative capacity.”

The brain contains two main cell types; neurons and glial cells. Neurons make and transmit nerve impulses whereas glial cells support, nourish and protect neurons. One particular subtype of glial cells, oligodendrocytes, make the myelin sheath that surrounds the axons of many neurons. Deng and his group developed a novel protocol to induce embryonic stem cells (ESCs) to differentiate into oligodendrocyte precursor cells or OPCs. Even though other researchers have made oligodenrocytes from ESCs, Deng’s method results in purer populations of OPCs than any other available method.

Making OPCs from ESCs is one thing, but can these laboratory OPCs do everything native can do? When Deng and his team tested the electrophysiological properties of their laboratory-made OPCs, they discovered that their cells lacked an important component; they did not express sodium channels. When the lab-made OPCs were genetically engineered to express sodium channels, they generated the characteristic electrical spikes that are common to native OPCs. According to Deng, this is the first time anyone has made OPCs in the laboratory with spiking properties. Is this significant?

Deng and his colleagues compared the spiking OPCs to non-spiking OPCs in the laboratory. Not only did the spiking OPCs communicate with neurons, but they also did a better job of maturing into oligodentrocytes.

Transplantation of these two OPC populations into the spinal cord and brains of mice that are genetically unable to produce myelin also showed differences. Both types of OPCs were able to mature into oligodendrocytes and produce myelin sheaths, but only the spiking OPCs had the ability to produce longer and thicker myelin sheaths.

Said Deng, “We actually developed ‘super cells’ with an even greater capacity to spike than natural cells. This appears to give them an edge for maturing into oligodendrocytes and producing better myelin.

Human neural tissue has a poor capacity to regenerate and even though OPCs are present, they do not regenerate tissue effectively when disease or injury damages the myelin sheath. Deng believes that replacing glial cells with the enhanced spiking OPCs to treat injuries and diseases has the potential to be a better strategy than replacing neurons, since neurons are so problematic to work with in the laboratory. Instead providing the proper structure and environment for neurons to live might be the best approach to regenerate healthy neural tissue. Deng also said that many diverse conditions that have not been traditionally considered to be myelin-based diseases (schizophrenia, epilepsy, and amyotrophic lateral sclerosis) are actually now recognized to involve defective myelin.

On that one, I think Deng is dreaming. ALS is caused by the death of motor neurons due to mechanisms that are intrinsic to the neurons themselves. Giving them all the myelin in the world in not going to help them. Also, OPCs made from ESCs will be rejected out of hand by the immune system if they are used to regenerate myelin in the peripheral nervous system. The only hope is to keep them in the central nervous system, but even there, any immune response in the brain will be fatal to the OPCs. This needs to be tested with iPSCs before it can be considered for clinical purposes.