Articles written in English

Biogen announced the first results of its pivotal phase 3 VALOR study in tofersen (BIIB067), an experimental antisense oligonucleotide (ASO) under evaluation for people with amyotrophic lateral sclerosis (ALS) who carry a mutation on the SOD1 gene.

The results are depressing.

enter image description here

The VALOR study showed that there was no slowing of disease progression, as measured by the overall score of the ALSFRS-R scale.

However, improvements have appeared on specific points or technical aspects.

In particular, the therapy has achieved its technical goal, although this does not translate into clinical terms. The production of SOD1 protein was indeed reduced, as differences were observed between the Tofersen and placebo groups of 38% and 26% in the faster and slower progressing populations respectively.

Regarding the baseline value of the plasma neurofilament light chain (NfL), a potential marker of neuronal degeneration, differences were observed between the tofersen and placebo groups of 67% and 48% in the more rapidly progressing populations. and slower respectively.

In the fastest growing population, respiratory function evolved somewhat slower than expected (SVC); difference of 7.9%). This is also the case for muscle strength.

However, serious neurological events have been reported in one in twenty patients receiving Tofersen, including 2 cases of myelitis (2.0%). One death was reported in the Tofersen group in the VALOR study, which was determined to be unrelated to Tofersen.

Tofersen binds to SOD1 mRNA, allowing its degradation by RNase-H1 to reduce the synthesis of mutant SOD1 protein production.

The idea that the production of a mutated gene should be reduced is very common among biologists, but it is medically counter-intuitive. Indeed our genes would not have been constantly selected through a billion year if they were useless, and if we could put them "KO" without serious consequences. SOD1 is a gene that is essential for survival. It is present in most organisms. So it's not surprising cases of myelitis appear when SOD1 production was inhibited. It happened as well in other clinical trials.

Moreover, an ASO is only effective for a certain type of mutation, but there are more than a hundred known mutations for SOD1, some with very rapid progression, others on the contrary almost harmless.

If the problem was due to a "gain of function" of the mutated protein, then it was not enough to reduce its production, it had to be corrected, or to increase the production of SOD2. Even the key 1993 article on SOD1 involvement in ALS suggested something similar.

Hopefully this failure will trigger a global strategic reflection at Biogen, which has stopped all research on ALS in general a few years, to concentrate on ALS subsets deemed (at the time) less risky through licenses with Ionis Pharmaceuticals.

This failure is not only that of an ALS therapy, it is the overall failure of research on neurodegenerative diseases which is unable to produce results despite colossal investments (more than 500 unsuccessful clinical trials for ALS, nearly 2,500 unsuccessful clinical trials for Alzheimer's). These numbers are dizzying and insane.


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

Alzheimer may be a comorbidity of ALS

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As observed in other neurodegenerative conditions, mixed pathologies also exist in ALS. In similar fashion to TDP-43 pathology playing a role in Alzheimer disease, Shuangwu Liu, Chuanzhu Yan and colleagues suggest here that Alzheimer disease pathology also plays a role in ALS. Indeed they found alterations at early stage in the subiculum, which is located in the temporal lobe of the brain, a region different from the frontal lobe which hosts the motor cortex which is classically implicated in ALS.

enter image description here Source: Wikipedia. The temporal lobe is shown in green, while the motor area is in the frontal lobe in blue

ALS is now considered a multisystemic disorder in which almost half of patients present with varying degrees of cognitive deficits, yet unfolded TDP-43 aggregates in cytosol are found in most ALS cases.

TDP-43 pathology in ALS can be divided into four stages (Braak stages): it begins focally, and then spreads persistently in sequential and regional patterns that typically originate from the motor cortex and extend to the prefrontal cortex, thalamus and eventually, the hippocampus.

However neuroimaging studies of hippocampal volumes in patients with amyotrophic lateral sclerosis (ALS) have reported inconsistent results. The group of Chinese scientists from 10 institutions, aimed to demonstrate that such discrepancies are largely due to atrophy of different regions of the hippocampus that emerge in different disease stages of ALS and to explore the existence of co-pathology in ALS patients.

They used King’s clinical staging system for ALS to classify patients into different disease stages. The scientists then investigated in vivo hippocampal atrophy patterns across subfields and anterior-posterior segments in different King’s stages using structural MRI in 76 ALS patients and 94 health controls.

The thalamus, corticostriatal tract and perforant path were used as structural controls to compare the sequence of alterations between these structures and the hippocampal subfields.

In summary:

  • ALS patients at King’s stage 1, had lower volumes in the bilateral posterior subiculum and presubiculum;
  • ALS patients at King’s stage 2 exhibited lower volumes in the bilateral posterior subiculum, left anterior presubiculum and left global hippocampus;
  • ALS patients at King’s stage 3 showed significantly lower volumes in the bilateral posterior subiculum, dentate gyrus and global hippocampus. Thalamic atrophy emerged at King’s stage 3.

White matter tracts remained normal in a subset of ALS patients.

In the present study, the authors demonstrated that the earliest hippocampal alterations in ALS patients occurred in the posterior subiculum and presubiculum, and these alterations emerged at King’s stage 1. This indicates that subiculum atrophy occurs earlier and independent of TDP-43 pathology in ALS.

enter image description here Hagmann P, Cammoun L, Gigandet X, Meuli R, Honey CJ, et al. 

Taken together, their data suggest that patients with ALS have additional pathologies that are independent of TDP-43 pathology.

Increasingly, studies have shown that at least 20% of ALS patients present significant Alzheimer disease pathology of both Aβ and tau proteins. Recently, Gómez-Pinedo and colleagues showed that in ALS patients, the amyloid cascade of the amyloid precursor protein is activated in the hippocampus of ALS patients, and cytoplasmic Aβ peptide and pTDP-43 expression levels are moderately correlated.

Thus the motor cortex and subiculum seem to represent two independent centres of ALS during the early stages of the disease, which represent TDP-43 pathology and Alzheimer disease pathology, respectively, and these pathologies may converge as the disease progresses toward advanced stages.

If these findings are confirmed in further studies, they will have a profound effect on the understanding of the aetiology and pathogenic mechanisms underlying ALS and other neurodegenerative diseases.


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

Deep brain stimulation (DBS) is an established therapy for patients with Parkinson's disease. enter image description here In silico computer models for DBS allow to pre-select a set of potentially optimal stimulation parameters. If efficacious, they could further carry insight into the mechanism of action of DBS and foster the development of more efficient stimulation approaches. In recent years, the focus has shifted towards DBS-induced firing in myelinated axons, deemed particularly relevant for the external modulation of neural activity.

The scientists in this new medRxiv publication, use the concept of pathway activation modeling, which incorporates advanced volume conductor models and anatomically authentic fiber trajectories to estimate DBS-induced action potential initiation in anatomically plausible pathways that traverse in close proximity to targeted nuclei.

Then the scientists applied the method on a retrospective dataset with the aim of providing a model-based prediction of clinical improvement following DBS (as measured by the motor part of the Unified Parkinsons Disease Rating Scale).

Based on differences in outcome and activation rates for two DBS protocols in a training cohort, the authors computed a theoretical 100% improvement profile and enhanced it by analyzing the importance of profile matching for individual pathways.

Finally, the authors validated the performance of authors' profile-based predictive model in a test cohort.

As a result, the authors demonstrated the clinical utility of pathway activation modeling in the context of motor symptom alleviation in Parkinsons patients treated with DBS.

Read the original article on medRxiv

Another interesting article was published by Alzforum. Alzforum is a quality news website dedicated to Alzheimer’s disease and other neurodegenerative disorders. It is a subsidiary Fidelity Management & Research. enter image description here In Alzheimer disease, aggregation of Aβ42 peptide into amyloids is conceived as the pathogenic trigger of a cascade leading to tau accumulation into neurofibrillary tangles, neuronal loss, and clinical dementia. However, while most of the 40 anti-amyloid clinical trials over the past two decades have successfully reduced the burden of brain amyloid, corresponding benefits for the patients have never materialized.

Moreover, brain amyloidosis does not invariably predict dementia: by the age of 85, the prevalence of brain amyloidosis is approximately 60% whereas that of dementia is only of 10%.

This new study makes the revolutionary hypothesis that high levels of natively-folded, soluble Aβ42 are associated with normal cognition in the setting of brain amyloidosis.

In a cross-sectional analysis of 598 brain amyloid-positive individuals participating in the Alzheimer's Disease Neuroimaging Initiative, higher levels of soluble Aβ42 were associated with normal cognition.

Higher soluble Aβ42 levels were also associated with better neuropsychological performance and larger hippocampal volume, with a larger effect size yielded by changes in soluble Aβ42 than in insoluble (brain amyloid) Aβ42.

“The main premise on which Alzheimer’s and all neurodegenerative diseases are conceived, is essentially the idea that proteins are toxic. It should end,” Alberto Espay, University of Cincinnati, told Alzforum.

Espay and Ezzat want their findings to inspire a paradigm shift on how we view neurodegenerative disease. “Our key message is that neurodegenerative diseases, in general, are associated with loss of protein,” said Espay. He contends that yes, aggregates accumulate, but total soluble protein goes down and that is what leads to disease. Tau protein levels falls in tauopathies, as synuclein in falls in Parkinson’s, Aβ in Alzheimer's disease, and progranulin in FDD/ALS.

The situation in Parkinson's disease mirrors what the scientists found in Alzheimer's disease. Most cases of Parkinson's disease have no specific known cause. A small proportion of cases, however, can be attributed to known genetic factors. Environmental toxins, herbicides, pesticides, and fungicides, as well as some medical and recreational drugs have been associated with the risk of developing PD. Vascular events such as stroke can cause Parkinson's disease. As for ALS, there are many conditions that look similar to Parkinson's disease. The motor symptoms of the disease result from the death of cells in the substantia nigra, a region of the midbrain.

For several generations of neurologists, the alpha-synuclein protein has been at the center of the Parkinson's disease universe. Alpha-synuclein is exists in the same form since prehistoric genomes. While the function of a protein molecule generally depends on its correct shape, wouldn't adopting an “incorrectly shaped” beta sheet aggregate make it impossible for it to function?

The central event was the discovery in 1997 that autosomal dominant Parkinson's disease was caused by a point mutation in the SNCA gene. Alpha-synuclein aggregates to form insoluble fibrils in pathological conditions characterized by Lewy bodies, such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy.

The elegant work of Braak and colleagues on the brains of patients under 50 with Parkinson's disease has shown that alpha-synuclein aggregates in a stereotypical pattern, conspicuously first appearing in the peripheral nervous system, then into the central nervous system.

As with the beta-amyloid protein in Alzheimer's disease, the elimination of alpha-synuclein in young mice makes no difference and actually protects them from the effects of MPTP, a mitochondrial toxin. Surprisingly, knockout mice, where the SNCA gene has been turned off, develop deficits when they get old!

One of the curious things about Lewy bodies is that the proportion of substantia nigra neurons containing Lewy pathology remains relatively constant regardless of how many neurons are already lost, which invalidates the classic belief that it is Lewy bodies that cause cell death in the substancia nigra.

Is it really the higher level of proteins, normal or mutated, that ultimately leads to neurodegenerative diseases?


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

Modeling neurodegenerative diseases is difficult because of poor access to human samples. Animal models fail to to model the disease due to critical differences between humans and other mammals.

The advent of human-induced pluripotent stem cell (hiPSC) technology now allow disease modeling using human samples that can be used for drug discovery.

Bosutinib and ropinirole are two candidate anti-ALS drugs recently identified in iPSC-based drug screens and are now under clinical investigation.

Bosutinib is a tyrosine kinase inhibitor used for the treatment of chronic myelogenous leukemia.

Bosutinib, an inhibitor of Src/c-Abl, has been found to increase the survival of ALS iPSC-derived MNs by inducing autophagy and reducing misfolded SOD1 and TDP-43 proteins.

Furthermore, bosutinib has been shown to delay disease onset and prolong survival of SOD1-mutant mice.

A Spanish group reported in 2018 that 2 ALS patients in whose Src/c-ABL seemed to have a beneficial effect.

A 12-week phase I dose-escalation open label trial has been initiated in early 2021 in ALS subjects (UMIN000036295) to evaluate the safety and tolerability of bosutinib at 4 levels (100, 200, 300 or 400 mg/day).

The results of this clinical trial had been announced. Some patients may have stopped progressing.

Of the nine patients who drank 100-300 milligrams of bosutinib daily for 12 weeks, five stopped progressing. Of the nine, the remaining four remained progressing at the same pace. Professor Inoue explains, "A phenomenon that is not normally seen has occurred."

Examination of the blood before taking the drug also revealed that the five people who stopped progressing produced biomarkers than the four who where still progressing. It can be an indicator of whether the drug is likely to work.

The results of this clinical trial will be announced online at the "25th World Neurology Conference".

Extreme caution is required, we saw many “breakthrough” announcements in ALS without any concrete result. It's an open label trial (without control arm), with a few patients and for a short time.

And the reason why it was beneficial for some patients and not for others is unknown.

In addition making specific (to avoid side effects) c-Abl inhibitors is a challenging task, and companies have tried and abandoned some past efforts for lack of success.


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

It has been known for several decades that Cu(II)ATSM belongs to a class of molecules with anti-inflammatory and antioxidant effects. enter image description here By Jynto via Wikipedia

In 2016 the synthetic copper-containing compound, CuATSM, was proposed as yet another drug candidate for the treatment of amyotrophic lateral sclerosis (ALS).

Scientists in the Beckman group in Australia, were studying transgenic mice with a double mutation, SOD1 and CCS. They decided to try the compound Cu(II)ATSM in a transgenic mouse, which is unable to stand up at the end of its short lifespan.

The researchers dissolved Cu(II)ATSM in dimethylsulfoxide and spread it on the neck of the little animal, where it was quickly absorbed through the skin. A few hours later, the mouse was again able to move.

The researchers shown that with continuous treatment, the mice can live 18 months, that is to say almost half of the average life of non-transgenic laboratory mice, instead of dying after three months.

The media ans social networks were, as usual, dithyrambic about Cu(II)ATSM.

This 2016 article had an unusual style, for example it nearly suggested that it deserved the Prize4Life.

However, scientific publications, here and there from 2011 and 2013 had already shown the benefits of Cu(II)ATSM for ALS (1 ). In fact Cu(II)ATSM belongs to a class of molecules that have been identified very early as being useful in SOD1-related diseases.

« I'm not sure that this will have an impact on sporadic diseases » said Lucie Bruijn of the ALS Association. Bruijn noted that Cu(II)ATSM-based therapy worked best in mice overexpressing both mSOD1 and CCS, and weakly in animals overexpressing only mSOD1.

The same was true of Jeffrey Rothstein, another prominent ALS scientist.

Beckman said that if Cu(II)ATSM proved to be safe and effective, he considered that it could become a prophylactic drug that a person with a SOD1 mutation could take for decades.

Unscrupulous people then illegally sold on Internet the complex (or a counterfeit compound) to desperate people.

In September 2019, Collaborative Medicinal Development, a company of Cthulhu (sic) Ventures LLC started a clinical trial (NCT04082832) where Cu(II)ATSM is administrated orally as a suspension powder. As results obtained from Phase I clinical trials observed that 8/14 patients receiving the highest dose of CuATSM (> 72 mg/day) exhibited reversible transaminitis (an indicator of liver dysfunction), consequently leading to the recommended Phase II dose set at 72 mg/day (2 bottles) on an empty stomach each day before breakfast. The clinical trial end date was supposed to be December 2020, but as of mid-2021 for obvious reason, no results are yet released.. There are two other clinical trials at Macquarie University.

In this new study Australian scientists assessed CuATSM in SOD1 G93A mice (an ALS animal model), treating at 100 mg/kg/day by gavage, starting at 70 days of age. https://www.nature.com/articles/s41598-021-98317-w

This dose in this specific model has not been assessed previously.

The authors reported that a subset of mice initially administered CuATSM exhibited signs of clinical toxicity, that necessitated euthanasia in extremis after 3-51 days of treatment. It is unclear why only a subset of mice exhibited signs of toxicity. Of the seven CuATSM affected mice, the authors were able to obtain plasma samples for two, which subsequently showed elevated alanine aminotransferase (ALT) levels, which is consistent with what happened to the Phase I patients.

Following a 1-week washout period, the remaining mice resumed treatment at the reduced dose of 60 mg/kg/day.

At this revised dose, treatment with CuATSM slowed disease progression and increased survival relative to vehicle-treated littermates.

This work provides evidence that CuATSM produces positive disease-modifying outcomes in high copy SOD1 G93A mice, which might not mean much for humans, an provides an upper limit for the dose.

This is however an unlikely high dose, as when it is converted to the dose for a human weighting 100kg (220lbs), it means a daily dose of 6.7 mg/kg/day, thus 670 mg per day for this 100kg (220lbs) person.


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

Mitochondria are organelles that have their own genomes, which are small and only encode 13 proteins, compared to around 20,000 for the genome of human cells. enter image description here By National Human Genome Research Institute - via Wikipedia

More than 1000 proteins are used by the mitochondria to perform their functions, the mitochondria therefore rely on the importation of proteins encoded in the nucleus of the host cell. The majority of mitochondrial proteins are synthesized in the cytosol and must be actively transported to the mitochondria, a process that occurs via a sophisticated system.

In many neurodegenerative diseases, there are dysfunctions in the management of proteins. This is called proteopathies. Proteopathies are found in diseases such as Creutzfeldt-Jakob disease and other prion diseases, Alzheimer's disease, Parkinson's disease, ALS and a wide range of other disorders.

Since proteins share a common structure known as the polypeptide backbone, all proteins have the potential to fold badly under certain circumstances. Mitochondrial defects might be responsible in part for those misfolded proteins that accumulate in the cytosol.

However, it is still unclear whether mitochondrial defects appear as a consequence of neurodegeneration, or if they contribute to it, or both. Since the accumulated mitochondrial protein precursors can form toxic aggregates, host cells have a mechanism to respond to and cope with them properly.

In an excellent eLife publication, Urszula Nowicka and colleagues at the University of Warsaw hypothesized that mitoprotein-induced stress induces a general response to precursor proteins which then accumulate in the cytosol and this contributes to the onset and progression neurodegenerative disorders. In this study, the authors propose a new mechanism of proteostasis.

Studies have shown that specific mitochondrial proteins that are functionally related to oxidative phosphorylation are downregulated by transcription in Alzheimer's disease. In the present study, scientists at the University of Warsaw investigated why these proteins are downregulated.

They used yeast homologues of these proteins to show the consequences of this cytosolic accumulation as well as of C. elegans worms. They applied mutations to the import machines, overexpression of mitochondrial proteins and CCCP (a decoupler of oxidative phosphorylation). They studied two disease-relevant aggregation models - α synuclein and Amyloid beta aggregation.

They found that importation of compromised mitochondrial proteins caused overall changes in the levels of transcriptome and proteins, especially chaperones, including Hsp104 and Hsp42, ABC transporters and mitochondrial proteins, which can lead to growth defects. (yeast) and decreased motility (C. elegans).

This new hypothesis complements the recent findings very well that unprocessed (but imported!) Precursor proteins aggregate in the mitochondrial matrix and initiate an mtUPR-like response.

These proteins trigger a molecular chaperone response specific to the host cell that aims to minimize the consequences of protein aggregation. However, when this rescue mechanism is insufficient, these aggregates stimulate cytosolic aggregation of other mitochondrial proteins and lead to downstream aggregation of non-mitochondrial proteins.

The present study showed that a group of mitochondrial proteins that are downregulated in Alzheimer's disease (i.e. Rip1, Atp2, Cox8 and Atp20) can aggregate in the cytosol and that the overexpression of these proteins upregulates Hsp42 and Hsp104, two molecular chaperones. Cellular stress responses induced by mitochondrial proteins mitigate the danger.

Urszula Nowicka's findings indicate why and how metastable mitochondrial proteins can be downregulated during neurodegeneration to minimize the imbalance in cellular protein homeostasis caused by their poor targeting.

Several stress response pathways have recently been identified to counteract import defects in mitochondrial proteins. It is not known, however, whether they act independently or whether simultaneous actions of all of these stress responses are necessary to ensure balanced homeostasis of cellular proteins.

It is likely that the study of the mechanisms of protection against stress, whether at the cellular level or at the mitochondrial level, will make it possible to better understand neurodegenerative diseases and to develop drugs to treat them.


This book retraces the main achievements of ALS research over the last 30 years, presents the drugs under clinical trial, as well as ongoing research on future treatments likely to be able stop the disease in a few years and to provide a complete cure in a decade or two.

A new version of my book on ALS research

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The previous revision of this book was done in February 2021. The new version has fewer pages because it focuses on research and less on clinical trials.

enter image description here

At that time, we were still awaiting the results of clinical trials with Arimoclomol. What a disappointment after that of Nurown! There may be a few lessons in this debacle, that a small molecule cannot help stop the progression of ALS (the corollary being that ALS is not due to single molecular dysfunction like a failed cell receptor) and that a single drug cannot be effective in the face of the diversity of cases encountered in a clinical trial.

There has been little news on the research front in 2021, especially compared to 2020.

On a regulatory front, what is a bit surprising is the turnaround of the FDA decision on AMX0035 under. the pressure of public opinion. AMX0035 is not a cure, during a clinical trial it can extend life expectancy by 6 months, which is both a lot and too little.

The only therapy that would be effective in stopping the progression of most cases of ALS is a TDP-43 therapy. A number of these therapies have been designed in laboratories for a few years, but no company has taken the risk of doing a clinical trial. Instead, companies prefer to bet on new compounds made from existing drugs, which helps speed up the passage of regulatory hurdles. A godsend for any investor including, curiously, some NGOs.

This once again illustrates how disorganized our pharmaceutical industry is. The biotechs care little about academic research, which is of poor quality anyway. Biotechs just want a quick payoff as they are essentially a gamble for investors, but they have a high death rate anyway. Large companies wait for successful biotechs, but generally do not research rare diseases because they are deemed unprofitable.

The new version of the book has also been updated in the last part which deals with the generation of new motor neurons in-vivo. This is the only way to restore health. Yet we have learned that new motor neurons derived from the patient's astrocytes are also carriers of the disease, so there is a phenomenon here that is not well understood.

Perhaps ALS and other neurodegenerative diseases belong to a spectrum of diseases where cells are not functional, for example because they are in a perpetual UPR / ISR state. An Italian clinical trial hints at something like this, let's hope Sephin1 / IFB-088 will be tried soon and give good news.

The French book is still not updated.

Otherwise the best advice ALS patients could be given in 2021 is still to keep their BMI at 27.

Jean-Pierre Le Rouzic Please do not hesitate to send me any feed-back

The ability to generate in-vivo spinal cord motor neurons from human pluripotent stem cells would be a major milestone in motor neuron-based diseases such as ALS. enter image description here

A key step in the design of human pluripotent stem cells differentiation strategies aiming to produce in-vitro motor neurons involves induction of the appropriate anteroposterior (A-P) axial identity, an important factor influencing motor neuron subtype specification, functionality, and disease vulnerability.

The anterior grey column contains motor neurons that affect the skeletal muscles while the posterior grey column receives information regarding touch and sensation. The anterior grey column is the column where the cell bodies of alpha motor neurons are located.

In-vitro generation of neural progenitors from human pluripotent stem cells holds a great promise for the development of cell-therapy-based approaches and the study of the specification of lineages and hence has attracted a considerable amount of research interest.

The protocols reported in literature generally are based on a multistep process that includes multiple neural induction, differentiation and maturation phases. This multistep process last weeks.

Scientists have previously described the generation of neural crest populations corresponding to various levels along the anteroposterior (A-P) axis from human pluripotent stem cells, including vagal neural crest (Frith et al., 2018). Yet stem cell derived motor neurons are often functionally immature.

Neural crest is a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia. The ectoderm is the outermost layer of the three primary germ layers formed in early embryonic development.

To date, differentiation strategies have either implemented human pluripotent stem cells in the presence of EGF, FGF signals (Li et al., 2018; Workman et al., 2017) or employed a monolayer differentiation approach that relies on transforming growth factor β (TGF-β) signaling suppression, bone morphogenetic protein (BMP) signaling regulation and WNT pathway stimulation to generate an neural crest like population (Barber et al., 2019; Lau et al., 2019).

Patterning of the in vitro derived neural crest to a vagal axial identity is routinely achieved by retinoic acid (RA) addition while further commitment has been mediated by co-culture with intestinal/colonic organoids (Lau et al., 2019), gut tissue explants (Li et al., 2018), or further differentiation following culture in neurotrophic medium (Barber et al., 2019; Lau et al., 2019).

An efficient method of directed differentiation, generates progenitors from human pluripotent stem cells via the combined WNT signaling stimulation and TFG-β pathway inhibition together with precise levels of bone morphogenetic protein signaling.

Most current protocols for induction of motor neurons from human pluripotent stem cells produce predominantly cells of a mixed hindbrain/cervical axial identity marked by expression of Hox paralogous group (PG) members 1-5, but are inefficient in generating high numbers of more posterior thoracic/lumbosacral Hox PG(8-13)+ spinal cord motor neurons.

Here, the authors describe a protocol for efficient generation of thoracic spinal cord cells and motor neurons from human pluripotent stem cells. This step-wise protocol relies on the initial generation of a neuromesodermal-potent axial progenitor population, which is differentiated first to produce posterior ventral spinal cord progenitors and subsequently to produce posterior motor neurons exhibiting a predominantly thoracic axial identity.

Replacing defective neurons is an attractive goal in diseases such as Parkinson's disease or ALS, but one that still seemed unrealistic. Recently impressive progress has been made.

Parkinson's disease is a neurodegenerative disorder caused by the selective degeneration of dopaminergic cells in the substantia nigra leading to major problems in the motor system. The substancia nigra is a tiny part of the mid brain. enter image description here Source Wikipedia: FrozenMan - Own work

One futuristic therapeutic approach for Parkinson's disease is dopaminergic cell-replacement therapy, in which dopaminergic precursors are grafted into the striatum to restore the lost dopaminergic neurotransmission.

Previous clinical trials based on foetal dopamine neuron transplantation have shown promising results, but also significant limitations including the survival of grafted dopaminergic neurons, which is very poor.

A major limiting factor for cell therapy in Parkinson's disease is the poor survival and reinnervation capacity of grafted dopaminergic neurons.

Major factors responsible for the high levels of dopaminergic cell loss during the transplantation process and early post-transplantation period have not been totally clarified. However, grafting-related cell trauma, lack of growth factors, poor vascularization, neuroinflammation and other factors have been involved.

MSCs have been effective against several of the above-mentioned factors, and a neuroprotective effect on grafted dopaminergic neurons could be expected. Mesenchymal stromal cells are multipotent cells originally isolated from the stroma of the bone marrow. Different studies have shown their capability to regulate the local environment through the release of immunomodulatory, antiapoptotic and trophic factors. These properties make them an attractive cell source for repairing damaged tissue.

In this work, Jannette Rodriguez-Pallares and colleagues from Spain, investigated whether co-grafting of MSCs could improve the survival and reinnervation ability of dopaminergic precursors transplanted in animal models of Parkinson's disease.

Rats with total unilateral dopaminergic denervation were grafted with a cell suspension of rat dopaminergic precursors (500,000 cells) with or without a high (200,000 cells) or low (25,000 cells) number of MSCs. Eight weeks after grafting, rats were tested for motor behaviour and sacrificed for histological analysis.

Results showed that the survival of dopaminergic neurons and graft-derived striatal dopaminergic innervation was higher in rats that received co-grafts containing a low number of MSCs than in non-co-grafted controls.

Surprisingly, the increase in the number of co-grafted MSCs led to detrimental effects. The mechanisms responsible for this effect are still unclear. A high concentration of MSCs may induce MSC senescence, damaged mitochondrial transfer or dysregulation of pro-inflammatory cytokine production.

In conclusion, co-grafting with MSCs or MSCs-derived products may constitute a useful strategy to improve dopaminergic graft survival and function. However, a tight control of MSCs density or levels of MSCs-derived products is necessary.

Read the original article on Pubmed

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