Tag Archives: neuron

Animal research leads to promising results for first clinical trial of stem cell therapy for stroke

The BBC reported yesterday that a small trial of a stem cell therapy developed by the biotech firm Reneuron has produced promising results, with 5 of the 9 patients enrolled in the trial showing unexpected improvements. The improvements were unexpected because the trial was intended to assess the safety of the technique, and the scientists did not expect to observe any measurable improvement. Larger trials agianst control groups are now planned to determine if the observed effect is indeed due to the stem cell therapy, and if so how much it contributes to the improvement. Behind the statistics are the human stories, for trial participant Frank Marsh, the result was a significant improvement to his quality of life, though he hopes for further improvement over time:

I can now grip things that I couldn’t grip before, like the hand rails at the swimming baths…I’d like to get back to my piano. I’d like to walk a bit steadier and further.”

Studies in rats are playing a key role in stem cell medicine. Image courtesy of Understanding Animal Research.

Studies in rats are playing a key role in stem cell medicine. Image courtesy of Understanding Animal Research.

As the Reneuron website points out animal studies allowed this therapy (ReN001, using the CTX0E03 human neuronal stem cell line) to be evaluated and assessed prior to launching human trials.

Post stroke rehabilitation – the aim of post stroke rehabilitation is to improve both functional and cognitive recovery in the patient some weeks or months after the stroke event.

It is this third treatment stage that our ReN001 stem cell therapy seeks to address. A number of treatments exist or are in development to treat stroke patients in the acute phase. However, there are currently no therapies available for patients who have a stable and fixed neurological deficit following a stroke. Our ReN001 cell therapy for stroke consists of a neural cell line, designated CTX, which has been generated using our proprietary cell expansion and cell selection technologies and then taken through a full manufacturing scale-up and quality-testing process. As such, ReN001 is a standardised, clinical and commercial-grade cell therapy product capable of treating all eligible patients presenting.

ReN001 has been shown to reverse the functional deficits associated with stroke disability when administered several weeks after the stroke event in relevant pre-clinical models. Extensive pre-clinical testing also indicates that the therapy is safe, with no adverse safety effects arising from the administration of the cells. Clinically, the potential of the ReN001 treatment is to engender a degree of recovery of function in disabled stroke patients sufficient to give them an improved quality of life and a reduced reliance on health and social care.”

In particular a study published in 2009 – the year this trial was announced – showed that CTX0E03 cells could restore a high degree of function when injected into the brains of rats 4 weeks after experimentally induced stroke, indicating that they could aid recovery in a time frame that was likely to be achievable in the clinic, where doctors will  – at least until this therapy is more established – wish to wait and assess the degree of functional recovery in stroke patients before deciding on whether or not stem cell therapy might be beneficial.

More recently their animal studies have focused on elucidating the mechanism through which CTX0E03 cells increase neurogenesis by increasing the populations of endogenous cells in the brain rather than directly replacing lost nerve cells, fundamental discoveries that will help scientists to optimise the use of this therapy and the development of future stem cell therapies.

Speaking of Research

Human embryonic stem cells restore hearing in deaf gerbils

Ever since human embryonic stem cells (hESCs) were first cultivated by Dr. James Thompson at the University of Wisconsin, Madison in 1998, they have been at the centre of one of the most promising, and at times controversial, areas of modern medicine.  Recently hESCs have begun to live up to their early promise, as I discussed in a recent post on the launch of a clinical trial of hESC-dericed retinal cells in restoring vision in Stargart’s Macular Dystrophy.

Now a study from the University of Sheffield – published this week in the prestigious scientific journal Nature (1) – indicates that hESCs may be able to restore hearing as well as vision, by showing that auditory nerve cells derived from hESCs could restore hearing in deaf gerbils.  While this is not the first time that auditory nerve cells have been created from hESCs, it is the first time that it has been demonstrated that they can restore the connection between the sensory hair cells that convert sound vibration into electrical signals and the brain, and demonstrated improvements to hearing. A commentary in Nature News discusses the work led by Dr. Marcelo Rivolta:

Rivolta has spent the past decade developing ways to differentiate human embryonic stem cells into the two cell types that are essential for hearing: auditory neurons, and the inner-ear hair cells that translate sound into electrical signals.

He treated human embryonic stem cells with two types of fibroblast growth factor (FGF) — FGF3 and FGF10 — to produce two, visually distinct, groups of primordial sensory cell. Those that had characteristics similar to hair cells were dubbed otic epithelial progenitors (OEPs), and those that looked more like neurons were dubbed otic neural progenitors (ONPs).

His team then transplanted ONPs into the ears of gerbils that had been treated with ouabain, a chemical that damages auditory nerves, but not hair cells. Ten weeks after the procedure, some of the transplanted cells had grown projections that formed connections to the brain stem. Subsequent testing showed that many of the animals could hear much fainter sounds after transplantation, with an overall improvement in hearing of 46%”

Gerbils were used in this study rather than the more usual mice because they hear sounds in the same frequency range as humans, whereas the hearing of mice functions best at higher frequencies.

Human ESC derived optic nerve cells (yellow) repopulate the gerbil cochlea. Credit: Marcelo Rivolta, University of Sheffield.

You can read more about the work on the University of Sheffield website, where Dr. Rivolta has published a discussion of his groups work.

It will be some time before this approach can be evaluated in human trials, as further animal studies will need to be undertaken to both improve the efficiency of the procedure so that greater improvement to hearing results, and to demonstrate efficacy and safety over longer periods of time (this study lasted only 10 weeks). It is also clear that this technique will need to be adapted to address the different causes of deafness, for example deafness may be due to damage to sensory cells, or to the auditory nerve that passes the message to the brain, or to both.

Insertion of the stem cells into the cochlea will require surgery, and the techniques required for this in human patients will need to be developed over the coming years, but over 200,000 people worldwide have now been fitted with cochlear implants, so the technical challenges involved are not insurmountable.  Cochlear implants are used to restore hearing to many deaf people, but require a functioning auditory nerve, so hESC derived auditory neurons could be used alongside cochlear implants to restore hearing to many people who cannot currently benefit from these implants. Indeed the potential of combining cochlear implants with stem cell therapy was a major motivation for concentrating on the auditory nerve in this initial study, as Dr. Rivolta noted in a statement to ScienceNow:

Obviously the ultimate aim is to replace both cell types, but we already have cochlear implants to replace hair cells, so we decided the first priority was to start by targeting the neurons.”

There’s no doubt that this is an exciting piece of research in its own right, and of course another example of how the field of stem cell research is maturing, but what’s also been very refreshing is how Dr. Rivolta and his colleagues at the University of Sheffield have been will to discuss their use of animals in research with the press, with reports appearing in numerous outlets including the BBC, Guardian, ABC news, Times of India, Fox and  Montreal Gazette. It is further evidence – if any is still needed – that when scientists are open about their use of animals in biomedical research they will find that there are many journalists and news editors do understand the value of such work, but it is equally certain that in order to report animal research accurately journalists need scientists and scientific institutes to engage with them and provide the detailed information to inform their articles. The message to the scientific community could not be any clearer; if you wish the public to understand your work, take the time to explain it to them.

Paul Browne

1)      Chen W, Jongkamonwiwat N, Abbas L, Eshtan SJ, Johnson SL, Kuhn S, Milo M, Thurlow JK, Andrews PW, Marcotti W, Moore HD, Rivolta MN. “Restoration of auditory evoked responses by human ES-cell-derived otic progenitors.” Nature. 2012 Sep 12. doi: 10.1038/nature11415. [Epub ahead of print] Pubmed: 22972191

Not Difficult To Grasp

Paralysis can have tremendous negative consequences for a person’s quality of life.  In the US alone, there are more than 200 thousand people living with chronic spinal cord injury, which is a cause of immense suffering to them and their families.  The disease generates economic burden for society as well.   Thus, there has been a lot of interest in using our knowledge of how movement is coded in the brain to allow patients to bypass nerve injuries and communicate directly with the environment.  Moreover, when asked about their priorities in terms of regaining motor function the vast majority of patients rank regaining arm and hand function as most important.

It is thus encouraging to read in Nature today an update on how these efforts by scientists have allowed a paralyzed patient to reach for a cup, bring it to her lips, and drink from it.

Critical milestones in the development of motor prosthesis for paralyzed patients

As explained in a nice News and Views piece by Andrew Jackson that accompanies the article, this type of work builds on decades of previous research on the neural mechanisms that control arm movements (here, here and here) (blue on the Fig above), on the development of chronic multi-electrode arrays (orange), their recording properties in animals, and on feasibility studies of neural interfaces in monkeys (here, here, here and here) (green), which opened the way to clinical studies in humans (here and here) (purple).

The value of animal research should not be difficult to grasp. The knowledge that allows us to “read out” the planned movements of the patient from different brain regions in order to guide the movement of the robot is critical in the design of the system.  And it is an indisputable fact that such knowledge has been (and continues to be) obtained by experiments in awake, behaving monkeys.

And for those that doubt the true motivation of scientists for doing their work, it is worth noting what Dr. Leigh Hochberg (one of the leading authors of the study) had to say about their results — “The smile on her face … was just a wonderful thing to see.”   Do you want to see her smile too?  Watch this:

Of course the BrainGate system used by Dr. Hochberg and Dr. John Donoghue – director of the Institute for Brain Science at Brown University – is not the only brain-machine interface system under development to restore function in paralysis. In 2008 we wrote about a similar brain implant developed by Dr. Andy Schwartz at the University of Pittsburgh which enabled monkeys to manipulate robotic hands with unprecedented dexterity. Last year we wrote about how Dr. Schwartz’s team had used a different technology known as electrocorticography to enable a paralysed man to manipulate a robotic arm, while Dr. Chet Moritz and colleagues at Wachington National Primate Research Centre, have coupled readings from individual nerve cells to a technology called functional electrical stimulation to restore control to temporarily paralysed muscles in monkeys, an approach that may eventually supersede the use of robotic arms in some patients. It will be fascinating to watch this technology progress into more widespread clinical use over the next decade, and thrilling to think that, impressive as it appears today, we have barely begun to tap the potential of brain-machine interface technology to change lives.

From the bench and the bedside; how animal research is taming Multiple Sclerosis

Multiple sclerosis (MS) is one of the most common diseases of the central nervous system – the brain and spinal cord – affecting about one person in every thousand in the USA. It is an inflammatory condition, where the immune system attacks the myelin sheath that surrounds the axons of nerve cells. Myelin is a fatty material that insulates nerves, acting much like the covering of an electric wire and allowing the nerve to transmit its impulses rapidly. It is the speed and efficiency with which these impulses are conducted that permits smooth, rapid and co-ordinated movements to be performed with little conscious effort. Loss of myelin interrupts these impulses, and the nerve cells themselves are also damaged and eventually die. 

The consequences for people with MS can be devastating, and MS is associated with a wide variety of symptoms, including muscle weakness, spasms, ataxia, problems with speech and vision, acute and chronic pain, and fatigue.  MS is a very variable disorder, and the rate at which it progresses varies considerably from one patient to another, but a defining characteristic of it is the lesions that are visible by MRI where the myelin has come under attack. The relapses, attacks of worsening neurological function that are often found in MS, are closely associated appearance of new lesions in the CNS, although not all new lesions cause a relapse.

Until about 20 years ago there were no treatments available that could prevent relapses or slow the progression of MS – known as disease modifying treatments – but thanks to the efforts of scientists working around the word this situation has begun to change.   A number of effective disease modifying treatments are now available, the most recent to receive FDA approval is Fingolimod (known as FTY720 during its development), a drug whose immunosuppressant properties in reducing transplant rejection and as a treatment for MS were evaluated in a range of animal models during its development.

These drugs may soon be joined by another. A couple of years ago I wrote about the crucial role of studies in mice, rats, and dogs in the development of a new disease modifying treatment called Laquinimod, which safely -though relatively modestly conpared to other new therapies – reduced the number of relapses, while slowing progression of disability more that current disease modifying drugs in a Phase III clinical trial. This is good news, and one more step towards turning MS form being an incurable disease to being a manageable disease.

One reason I say manageable rather than curable is that while these treatments are effective in reducing the number of relapses for many patients they do not work for all patients and all forms of MS (particularly for primary progressive MS), and can sometimes have serious side effects that prevent patients from continuing treatment. That is why scientists are continuing to study the biological mechanisms in MS, a disease whose origin is still not fully understood, though clinical and animal research indicates that both genetic and environmental factors play a role, their ultimate goal is to develop treatments that can stop relapses altogether.

Another reason for not referring to disease modifying treatments as “cures” is that they do not directly repair the damaged myelin sheath at the lesions. Spontaneous repair of the damaged myelin sheath in MS lesions does happen and plays an important role in limiting neurological damage, but until now the molecular basis of myelin regeneration by cells called oligodentrocytes, in the central nervous system (CNS) has been poorly understood. The Guardian reports on how scientists at the University of Cambridge have discovered how to promote remyelination in MS lesions by activating a population of stem cells in the CNS called oligodentrocyte precursor cells (1).

The team led by Professor Robin Franklin generated a comprehensive transcriptional profile of 22,000 genes during the separate stages of spontaneous remyelination that follow focal toxin-induced demyelination in the rat CNS, and found that the level of retinoid acid receptor RXR-gamma expression was increased during remyelination. Cells of the oligodendrocyte lineage expressed RXR-gamma in rat tissues that were undergoing remyelination, in both active lesions and in older remyelinated  lesions. By examining post-mortem brain samples from MS patients, they were able to show that RXR-gamma expression was also elevated in oligodendrocyte precursor cells at the active lesion sites, supporting a general role for RXR-gamma in remyelination. Interesting as these findings were they did not demonstrate that RXR-gamma is actually required for remyelination, so they next performed studies to determine whether blocking the function of RXR-gamma would prevent remyelination.

Rats are crucial to many areas of MS research. Image courtesy of Understanding Animal Research.

Knockdown of RXR-gamma by RNA interference or RXR-specific antagonists severely inhibited the differentiation of oligodendrocyte precursor cells into mature oligodendrocytes in culture. In mice that lacked RXR-gamma, adult oligodendrocyte precursor cells efficiently repopulated lesions after demyelination, but showed delayed differentiation into mature oligodendrocytes. The next question was whether increasing the activity of RXR-gamma would speed up remyelination. Administration of the RXR agonist 9-cis-retinoic acid to demyelinated mouse cerebellar slice cultures and then to aged rats in vivo after focal demyelination caused an increase in remyelinated axons. Focal toxin-induced demyelination was used to produce the lesions, rather than an immunity mediated model of demyelination such as experimental autoimmune encephalomyelitis, in order to determine that the increased remyelination was due to promotion of oligodendrocyte differentiation rather than to the anti-inflammatory effects of 9-cis retinoic acid.

The results indicate that RXR-gamma plays an important role in endogenous oligodendrocyte precursor cell differentiation and remyelination, and might be a pharmacological target for regenerative therapy in MS. The discovery that 9-cis-retinoic acid, a compound already in limited clinical use, can be used to stimulate myelin regeneration raises the possibility that within the next decade treatments that repair the neurological damage in MS will begin to enter clinical trials.

For people with MS these scientific and clinical advances are a great source of hope for a better future.

Paul Browne

1)      Huang J.K. et al. “Retinoid X receptor gamma signalling accelerates CNS remyelination” Nature Neuroscience Published Online 05 December 2010 DOI: 10.1038/nn.2702

Of mice and mTOR: Can damaged spinal cords be tought to repair themselves?

There’s an interesting story on the BBC website about new research on nerve cell regeneration after spinal cord damage in mice, work undertaken by a team led by Dr. Zhigang He of the F.M. Kirby Neurobiology Center at Children’s Hospital Boston.

Nerve regeneration in mice requires mTOR. Image courtesy of Understanding Animal Research.

Those of you who follow developments on the field of spinal cord repair may find this story familiar. The study published online in Nature Neuroscience this week (1) follows up on work by the same team published two years ago (2) which examined whether regeneration of the optic nerve of mice could be promoted by using an adenovirus-based vector to locally delete several genes known to suppress cell growth. They found that knocking out gene named PTEN in the optic nerve encouraged regeneration of nerve cells following damage. PTEN inhibits the activity of the enzyme mTOR which is an important promoter of cell growth and survival, so removing PTEN increases mTOR activity and promotes regrowth of damaged nerve tissue. In agreement with this that found that mTOR levels are high in nerve cells of the central nervous system (CNS) in mice seven days after birth, when nerve cells are still naturally capable of regeneration and repair, but far lower two months later when such nerve regeneration is no longer observed. mTOR is a key regulator of cell growth throughout the body, and it’s activity is highly conserved throughout the evolutionary tree.

The latest study demonstrates that nerve regeneration through activation of the mTOR pathway does not only happen at the optic nerve but can also be induced in other parts of the CNS, with obvious implications for repairing spinal cord damage.

As the BBC report points out this is still quite preliminary work; the study demonstrated that the regenerated nervous tissue had all the features of normal nervous tissue, including the ability to form synapses that are needed to transmit signals from one nerve cell to another, but they have yet to show that it improves the function of the damaged nerve tissue. Other factors will need to be used alongside PTEN inhibition to encourage the regenerating cells to form a bridge across the damaged section of the spinal cord. The authors point out several promising approaches to achieving this are currently under development, for example growth factors that guide the growth of regenerating nerve cells to the correct location.

The PTEN knock-out approach used in these two studies, while useful in laboratory studies, is not suitable for the clinic because its effects are permanent. It should, however, be possible to develop a drug, perhaps using RNAi or Morphilinos, to temporarily turn off PTEN activity at the site of injury and promote nerve regeneration. Whatever approach is used it will be important to be able to target the increase in mTOR activity to the site of injury. mTOR is involved in the regulation of cell growth throughout the body and indiscriminate activation of it might have adverse consequences, after all several drugs are under development that turn off mTOR activity in cancer cells.

All in all it is an interesting piece of work, even if it only goes part of the way towards developing a therapy that can repair damaged spinal cords and prevent paralysis. This is an exciting time for research on treating paralysis, with a variety of techniques under development. These range from transplantation of stem cells such as Olfactory ensheathing cells or embryonic stem cells, to the development of robotic limbs controlled through brain-machine interfaces. Such a variety of approaches is entirely justified by the complexity of the problem that needs to be solved, not every technology will be appropriate for every patient, and furthermore it is likely that the regeneration-promoting technique described in this week’s report may help to increase the effectiveness of stem cell transplants.

It’s just another example of how important animal research is to progress in one of today’s most exciting areas of medicine.

Paul Browne

1)      Liu K. et al. “PTEN deletion enhances the regenerative ability of adult corticospinal neurons” Nature Neuroscience, published online 8 August 2010; doi:10.1038/nn.2603

2)      Park K.K. et al. “Promoting axon regeneration in the adult CNS by modulation of the PTEN/mTOR pathway.”  Science, Volume 322(5903), Pages 963-966 (2008) doi:10.1126/science.1161566

Understanding migraines: The blind leading the…err…rats

Chances are that you have either suffered from migraine yourself or have a family member or close friend who have, after all about 1 in 8 of us will suffer from migraine at some stage in our lifetime, and some sufferers experience repeated debilitating episodes over many years . While headache on one side of the brain is typical other symptoms such as nausea are very common, indeed in some migraine victims nausea is the primary symptom of the disorder.  Through a combination of studies in animals and clinical research using techniques such as fMRI and PET scans scientists have learned a lot in recent years about what happens before and during migraine episodes but we do not yet fully understand what ultimately causes the attacks, and debate rages over the relative importance of some mechanisms originating deep in brain regions such as the hypothalamus and others that start in membranes that surround the brain, (1,2).  Current treatments can help prevent migraine, reduce suffering and hasten recovery they do not work for all patients, and a better understanding of what exactly is happening before and during a migraine attack will aid the development of really effective treatments and preventative measures.  A study published in Nature Neuroscience combines clinical research with studies of rats to provide clues about a key characteristic of migraines that has until now remained unexplained, the exacerbation of the pain experienced by sufferers by light (3).

The team, lead by Rami Burnstein of Beth Israel Deaconess Medical Centre in Boston, decided to concentrate of the role of a particular subset of nerve cells in the retina known as intrinsically photosensitive retinal ganglion cells (ipRGCs) which they knew from previous mouse research to be involved in eye functions that are not image forming, such as setting the biological clock to the day night cycle.  The ipRGCs are stimulated by light both indirectly via the rods and cones and directly through a pigment called melanopsin that they themselves contain.  In order to discover if the ipRCGs are important to light sensitivity in migraine they performed a very neat clinical study involving 20 blind patients who also suffered from migraine. Six of these patients lacked any light perception due to removal of their eyes or damage to the optic nerve, while in the remaining 14 the damage to the eyes was less total, affecting the rods and cones but not ipRGCs, so that while they were unable to see images they could detect light. The results were clear, blue and grey light made the headaches of those who retained light sensitivity worse, while having no effect on the six blind individuals who lacked light perception.

Determining that the ipRGCs are involved in the exacerbation of migraine headaches by light is of course only part of the story, and Professor Burnstein’s team next turned to tracing the nerve pathways that are responsible for the increased pain, knowledge that might help to develop new treatments.  This they could not do in human subjects because the available imaging techniques do not have the precision to determine the connections between individual neurons.  In a series of studies they injected labels including Green Fluorescent Protein into particular areas of the eyes and brain, and in some cases even individual nerve cells, of anesthetized rats with and followed the path of the neurons.  They were also able to use tiny electrodes to record the effect of light on the firing of individual nerves in the brain, something that cannot yet be done in human subjects. An exciting observation was that the ipRCGs connected to cells in a region of the brain known as the posterior thalamus, itself part of the trigeminovascular pathway that is strongly implicated in migraine headache through transmission of nerve signals from the irritated outer brain membranes to the deep brain. When they examined the electrical activity of these cells they discovered that the majority of the cells within the posterior thalamus that are involved in mediating migraine pain are also light sensitive.  Finally they demonstrated that the light-sensitive pain-mediating neurons of the posterior hypothalamus connect to nerve cells in several regions of the somatosensory region of the cortex, an intriguing discovery since abnormalities in this region have previously been seen in migraine patients. This discovery is likely to encourage scientists to study the role of the somatosensory cortex in migraine in more detail.

So how important is this study? Well it’s unlikely that this discovery will lead to any treatment breakthrough in the immediate future, though the discovery that grey light can exacerbate migraine headache is new and may help patients to avoid it.  Despite a perhaps natural tendency for the news media to look for “breakthroughs” the majority of scientific papers published are like this one, providing valuable new insights into biology that contribute to our overall understanding of how biological systems work and happens when they go awry but not indicating an easy fix.  I’ve no doubt that this and many similar basic science studies will contribute to better treatments for migraine in the future, but perhaps not tomorrow!

Regards

Paul Browne

1)      Olesen J. et al “Origin of pain in migraine:evidence for peripheral sensitization” The Lancet Neurology Volume 8, Issue 7, Pages 679-690 (2009) doi:10.1016/S1474-4422(09)70090-0

2)      Alstadhaug K.B.  “Migraine and the hypothalamus” Cephalalgia Volume 29, Issue 8, Pages 809-817 doi: 10.1111/j.1468-2982.2008.01814.x

3)      Noseda R. et al. “A neural mechanism for exacerbation of headache by light” Nature neuroscience Advance Publication Online 10 January 2010 doi: 10.1038/nn.2475