Progressive multiple sclerosis: from pathophysiology to therapeutic strategies

Transplantation of induced neural stem cells (iNSCs) into chronically demyelinated corpus callosum ameliorates motor deficits

Multiple Sclerosis (MS) causes neurologic disability due to inflammation, demyelination, and neurodegeneration. Immunosuppressive treatments can modify the disease course but do not effectively promote remyelination or prevent long term neurodegeneration. As a novel approach to mitigate chronic stage pathology, we tested transplantation of mouse induced neural stem cells (iNSCs) into the chronically demyelinated corpus callosum (CC) in adult mice. Male C57BL/6 mice fed 0.3% cuprizone for 12 weeks exhibited CC atrophy with chronic demyelination, astrogliosis, and microglial activation. Syngeneic iNSCs were transplanted into the CC after ending cuprizone and perfused for neuropathology 2 weeks later. Magnetic resonance imaging (MRI) sequences for magnetization transfer ratio (MTR), diffusion-weighted imaging (T2), and diffusion tensor imaging (DTI) quantified CC pathology in live mice before and after iNSC transplantation. Each MRI technique detected progressive CC pathology. Mice that received iNSCs had normalized DTI radial diffusivity, and reduced astrogliosis post-imaging. A motor skill task that engages the CC is Miss-step wheel running, which demonstrated functional deficits from cuprizone demyelination. Transplantation of iNSCs resulted in marked recovery of running velocity. Neuropathology after wheel running showed that iNSC grafts significantly increased host oligodendrocytes and proliferating oligodendrocyte progenitors, while modulating axon damage. Transplanted iNSCs differentiated along astrocyte and oligodendrocyte lineages, without myelinating, and many remained neural stem cells. Our findings demonstrate the applicability of neuroimaging and functional assessments for pre-clinical interventional trials during chronic demyelination and detect improved function from iNSC transplantation. Directly reprogramming fibroblasts into iNSCs facilitates the future translation towards exogenous autologous cell therapies.

Diagnostic uncertainty during the transition to secondary progressive multiple sclerosis: Multicenter study in Argentina

BACKGROUND

A period of diagnostic uncertainty often characterizes the clinical transition from relapsing to secondary progressive multiple sclerosis (SPMS).

OBJECTIVE

The aim of this study was to describe the length of time required to reclassify relapsing-remitting MS (RRMS) patients who have clinically transitioned to SPMS (diagnosis uncertainty).

METHODS

This is a retrospective multicenter cohort study conducted in Argentina, identifying in every center all patients with diagnosis of MS who transitioned from RRMS to SPMS during the follow-up. We identified the dates of the last definitive RRMS and first definitive SPMS diagnoses for diagnostic uncertainty. The time required to reclassify RRMS who transitioned to SPMS and the time from disease onset to reclassify SPMS were calculated using the Kaplan-Meier method.

RESULTS

A total of 170 patients were included, where the mean age at disease onset (first symptom) was 36 ± 6 years; the length of time required to reclassify RRMS patients who transitioned to SPMS was 3.3 ± 1.1 years (range = 1-7 years); and the time from disease onset to classify SPMS was 19.4 ± 8.5 years (range = 16-35 years).

CONCLUSION

A period of diagnostic uncertainty regarding the transition from RRMS to SPMS was present in many of our patients, with a mean time of 3.3 years.

Promising Nanotechnology Approaches in Treatment of Autoimmune Diseases of Central Nervous System

Multiple sclerosis (MS) is a chronic, autoimmune, neurodegenerative disease of the central nervous system (CNS) that yields to neuronal axon damage, demyelization, and paralysis. Although several drugs were designed for the treatment of MS, with some of them being approved in the last few decades, the complete remission and the treatment of progressive forms still remain a matter of debate and a medical challenge. Nanotechnology provides a variety of promising therapeutic tools that can be applied for the treatment of MS, overcoming the barriers and the limitations of the already existing immunosuppressive and biological therapies. In the present review, we explore literature case studies on the development of drug delivery nanosystems for the targeted delivery of MS drugs in the pathological tissues of the CNS, providing high bioavailability and enhanced therapeutic efficiency, as well as nanosystems for the delivery of agents to facilitate efficient remyelination. Moreover, we present examples of tolerance-inducing nanocarriers, being used as promising vaccines for antigen-specific immunotherapy of MS. We emphasize on liposomes, as well as lipid- and polymer-based nanoparticles. Finally, we highlight the future perspectives given by the nanotechnology field toward the improvement of the current treatment of MS and its animal model, experimental autoimmune encephalomyelitis (EAE).

Emerging myelin repair agents in preclinical and early clinical development for the treatment of multiple sclerosis

INTRODUCTION

Remyelination is a highly effective regenerative process that can restore axon function, prevent axonal loss, and reverse clinical deficits after demyelination. Hence, the promotion of remyelination is a logical goal in patients with multiple sclerosis (MS) in which remyelination is often insufficient. However, despite great progress regarding the development of immunomodulatory therapies for MS and an abundance of promising evidence from preclinical experiments so far, no therapy has convincingly demonstrated clinically significant remyelination properties. Therefore, enhancing myelin repair is an urgent and unmet need in MS.

AREAS COVERED

We searched clinicaltrials.gov and pubmed.ncbi.nlm.nih.gov and focused on therapeutic agents in development from the preclinical stage to clinical phase II. We selected agents for which data are available from in vitro experiments and at least one toxic demyelination animal model that reached at least phase I in clinical development in MS patients.

EXPERT OPINION

The evidence to promote remyelination is very promising for several agents, some of which possess anti-muscarinergic properties. Since remyelination is a complex process that involves various coordinated steps, a combination of different therapeutic approaches addressing different aspects of this regenerative mechanism may be reasonable. Furthermore, suitable surrogate markers of remyelination are necessary for proof-of-concept clinical trials.

Could non-invasive brain-stimulation prevent neuronal degeneration upon ion channel re-distribution and ion accumulation after demyelination?

Fast and efficient transmission of electrical signals in the nervous system is mediated through myelinated nerve fibers. In neuronal diseases such as multiple sclerosis, the conduction properties of axons are disturbed by the removal of the myelin sheath, leaving nerve cells at a higher risk of degenerating. In some cases, the protective myelin sheath of axons can be rebuilt by remyelination through oligodendroglial cells. In any case, however, changes in the ion channel organization occur and may help to restore impulse conduction after demyelination. On the other hand, changes in ion channel distribution may increase the energy demand of axons, thereby increasing the probability of axonal degeneration. Many attempts have been made or discussed in recent years to increase remyelination of affected axons in demyelinating diseases such as multiple sclerosis. These approaches range from pharmacological treatments that reduce inflammatory processes or block ion channels to the modulation of neuronal activity through electrical cortical stimulation. However, these treatments either affect the entire organism (pharmacological) or exert a very local effect (electrodes). Current results show that neuronal activity is a strong regulator of oligodendroglial development. To bridge the gap between global and very local treatments, non-invasive transcranial magnetic stimulation could be considered. Transcranial magnetic stimulation is externally applied to brain areas and experiments with repetitive transcranial magnetic stimulation show that the neuronal activity can be modulated depending on the stimulation parameters in both humans and animals. In this review, we discuss the possibilities of influencing ion channel distribution and increasing neuronal activity by transcranial magnetic stimulation as well as the effect of this modulation on oligodendroglial cells and their capacity to remyelinate previously demyelinated axons. Although the physiological mechanisms underlying the effects of transcranial magnetic stimulation clearly need further investigations, repetitive transcranial magnetic stimulation may be a promising approach for non-invasive neuronal modulation aiming at enhancing remyelination and thus reducing neurodegeneration.

Cortical axonal loss is associated with both gray matter demyelination and white matter tract pathology in progressive multiple sclerosis: Evidence from a combined MRI-histopathology study

Background:

Neuroaxonal degeneration is one of the hallmarks of clinical deterioration in progressive multiple sclerosis (PMS).

Objective:

To elucidate the association between neuroaxonal degeneration and both local cortical and connected white matter (WM) tract pathology in PMS.

Methods:

Post-mortem in situ 3T magnetic resonance imaging (MRI) and cortical tissue blocks were collected from 16 PMS donors and 10 controls. Cortical neuroaxonal, myelin, and microglia densities were quantified histopathologically. From diffusion tensor MRI, fractional anisotropy, axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) were quantified in normal-appearing white matter (NAWM) and white matter lesions (WML) of WM tracts connected to dissected cortical regions. Between-group differences and within-group associations were investigated through linear mixed models.

Results:

The PMS donors displayed significant axonal loss in both demyelinated and normal-appearing (NA) cortices (p < 0.001 and p = 0.02) compared with controls. In PMS, cortical axonal density was associated with WML MD and AD (p = 0.003; p = 0.02, respectively), and NAWM MD and AD (p = 0.04; p = 0.049, respectively). NAWM AD and WML AD explained 12.6% and 22.6%, respectively, of axonal density variance in NA cortex. Additional axonal loss in demyelinated cortex was associated with cortical demyelination severity (p = 0.002), explaining 34.4% of axonal loss variance.

Conclusion:

Reduced integrity of connected WM tracts and cortical demyelination both contribute to cortical axonal loss in PMS.

Klotho Pathways, Myelination Disorders, Neurodegenerative Diseases, and Epigenetic Drugs

In this review we outline a rationale for identifying neuroprotectants aimed at inducing endogenous Klotho activity and expression, which is epigenetic action, by definition. Such an approach should promote remyelination and/or stimulate myelin repair by acting on mitochondrial function, thereby heralding a life-saving path forward for patients suffering from neuroinflammatory diseases. Disorders of myelin in the nervous system damage the transmission of signals, resulting in loss of vision, motion, sensation, and other functions depending on the affected nerves, currently with no effective treatment. Klotho genes and their single-pass transmembrane Klotho proteins are powerful governors of the threads of life and death, true to the origin of their name, Fates, in Greek mythology. Among its many important functions, Klotho is an obligatory co-receptor that binds, activates, and/or potentiates critical fibroblast growth factor activity. Since the discovery of Klotho a little over two decades ago, it has become ever more apparent that when Klotho pathways go awry, oxidative stress and mitochondrial dysfunction take over, and age-related chronic disorders are likely to follow. The physiological consequences can be wide ranging, potentially wreaking havoc on the brain, eye, kidney, muscle, and more. Central nervous system disorders, neurodegenerative in nature, and especially those affecting the myelin sheath, represent worthy targets for advancing therapies that act upon Klotho pathways. Current drugs for these diseases, even therapeutics that are disease modifying rather than treating only the symptoms, leave much room for improvement. It is thus no wonder that this topic has caught the attention of biomedical researchers around the world.

Inflammasome and Cognitive Symptoms in Human Diseases: Biological Evidence from Experimental Research

Cognitive symptoms are prevalent in the elderly and are associated with an elevated risk of developing dementia. Disease-driven changes can cause cognitive disabilities in memory, attention, and language. The inflammasome is an innate immune intracellular complex that has a critical role in the host defense system, in that it senses infectious pathogen-associated and endogenous danger-associated molecular patterns. An unbalanced or dysregulated inflammasome is associated with infectious, inflammatory, and neurodegenerative diseases. Due to its importance in such pathological conditions, the inflammasome is an emerging drug target for human diseases. A growing number of studies have revealed links between cognitive symptoms and the inflammasome. Several studies have shown that reducing the inflammasome component mitigates cognitive symptoms in diseased states. Therefore, understanding the inflammasome regulatory mechanisms may be required for the prevention and treatment of cognitive symptoms. The purpose of this review is to discuss the current understanding of the inflammasome and its relationships with cognitive symptoms in various human diseases.

Peroxisomal Dysfunction and Oxidative Stress in Neurodegenerative Disease: A Bidirectional Crosstalk

Peroxisomes are multifunctional organelles best known for their role in cellular lipid and hydrogen peroxide metabolism. In this chapter, we review and discuss the diverse functions of this organelle in brain physiology and neurodegeneration, with a particular focus on oxidative stress. We first briefly summarize what is known about the various nexuses among peroxisomes, the central nervous system, oxidative stress, and neurodegenerative disease. Next, we provide a comprehensive overview of the complex interplay among peroxisomes, oxidative stress, and neurodegeneration in patients suffering from primary peroxisomal disorders. Particular examples that are discussed include the prototypic Zellweger spectrum disorders and X-linked adrenoleukodystrophy, the most prevalent peroxisomal disorder. Thereafter, we elaborate on secondary peroxisome dysfunction in more common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Finally, we highlight some issues and challenges that need to be addressed to progress towards therapies and prevention strategies preserving, normalizing, or improving peroxisome activity in patients suffering from neurodegenerative conditions.

Detecting neurodegenerative pathology in multiple sclerosis before irreversible brain tissue loss sets in

Background

Multiple sclerosis (MS) is a complex chronic inflammatory and degenerative disorder of the central nervous system. Accelerated brain volume loss, or also termed atrophy, is currently emerging as a popular imaging marker of neurodegeneration in affected patients, but, unfortunately, can only be reliably interpreted at the time when irreversible tissue damage likely has already occurred. Timing of treatment decisions based on brain atrophy may therefore be viewed as suboptimal.

Main body

This Narrative Review focuses on alternative techniques with the potential of detecting neurodegenerative events in the brain of subjects with MS prior to the atrophic stage. First, metabolic and molecular imaging provide the opportunity to identify early subcellular changes associated with energy dysfunction, which is an assumed core mechanism of axonal degeneration in MS. Second, cerebral hypoperfusion has been observed throughout the entire clinical spectrum of the disorder but it remains an open question whether this serves as an alternative marker of reduced metabolic activity, or exists as an independent contributing process, mediated by endothelin-1 hyperexpression. Third, both metabolic and perfusion alterations may lead to repercussions at the level of network performance and structural connectivity, respectively assessable by functional and diffusion tensor imaging. Fourth and finally, elevated body fluid levels of neurofilaments are gaining interest as a biochemical mirror of axonal damage in a wide range of neurological conditions, with early rises in patients with MS appearing to be predictive of future brain atrophy.

Conclusions

Recent findings from the fields of advanced neuroradiology and neurochemistry provide the promising prospect of demonstrating degenerative brain pathology in patients with MS before atrophy has installed. Although the overall level of evidence on the presented topic is still preliminary, this Review may pave the way for further longitudinal and multimodal studies exploring the relationships between the abovementioned measures, possibly leading to novel insights in early disease mechanisms and therapeutic intervention strategies.

HIV-1 Tat protein attenuates the clinical course of experimental autoimmune encephalomyelitis (EAE)

A growing body of evidence has shown that the human immunodeficiency virus (HIV) infection is associated with a significantly decreased risk of developing multiple sclerosis (MS) in patients with acquired immunodeficiency virus (AIDS). It is thought that two mechanisms are in charge of protection against MS, which include immunosuppression induced by chronic HIV infection (depletion of CD4 + T cells) and antiretroviral medications. HIV-1 encodes several regulatory (Tat and Rev) and accessory (Vpr, Vif, Vpu, and Nef) proteins that have immunosuppressive and immunomodulatory properties. HIV-1 Tat protein is a strongly immunosuppressive agent and can cross the blood-brain barrier (BBB). In this study, we examined the effect of HIV-1 Tat, which is classified into clade B and C, on inflammation, gliosis, apoptosis, and behavioral function in a murine model of MS called experimental autoimmune encephalomyelitis (EAE). For this aim, mice were immunized with myelin oligodendrocyte glycoprotein 35-55 (MOG35-55), followed by pertussis toxin to induce paralysis in EAE mice. After the induction of EAE in mice, the animals intraperitoneally received serial doses of HIV-1 Tat clade B and C (5, 10, and 20 µg/kg body weight) when the early clinical manifestations of EAE were initiated. The results showed that the administration of both clades of the Tat protein led to a marked decrease in the clinical score of EAE mice, as well as improvement in motor-neuron functions. In line with this, Tat considerably reduced the number of apoptotic cells in the sacral region of the spinal cord through the upregulation expression of the Bcl-2 protein. Besides, proinflammatory cytokines such as, IFN-γ, TNF-α, IL-6, and IL-17 were significantly diminished in the serum and spinal cord of EAE mice receiving HIV-1 Tat clade B and C. Conversely, anti-inflammatory cytokines, including IL-10 and IL-4 were elevated in the serum and spinal cord of EAE mice receiving HIV Tat clade B and C when compared with the control group. The immunohistochemical analysis indicated that HIV-1 Tat clade B and C mitigated microgliosis and astrogliosis. The flow cytometry analysis demonstrated that the number of Th1 and Th17cells was significantly decreased in response to TAT administration while the frequency of Th2 cells was markedly increased in the peripheral blood of mice with EAE without influencing the number of T regulatory cells (CD4 + CD25 + forkhead box protein 3 + ). It seems that HIV-1 Tat could be a bona fide therapeutic protein for the alleviation of MS since it has beneficial roles in the suppression of neuroinflammation in MS pathology.

Progressive multiple sclerosis: latest therapeutic developments and future directions

Multiple sclerosis (MS) is a chronic inflammatory condition of the central nervous system leading to demyelination and neurodegeneration. While the initial presentation is mostly characterized by a relapsing-remitting disease, patients often progress naturally after 10-15 years to a secondary-progressive disease course. Another 10-15% present with an initial, primary-progressive MS course. Pathogenic mechanisms possibly driving progression include continued compartmentalized inflammation by T- and B-lymphocytes and cells of innate immunity, oxidative stress, iron accumulation, and consecutive mitochondrial damage, altogether leading to neurodegeneration with accumulation of disability. Increasing knowledge about pathogenic mechanisms involved in progressive MS helps to design more specific and precise therapeutic approaches. Successful examples are the B-cell targeting monoclonal antibody ocrelizumab, effective in primary progressive MS, and the sphingosine-1-receptor modulator siponimod, effective in active forms of secondary-progressive MS. Apart from that, other medications such as the B-cell targeted antibody ofatumumab, cladribine due to T- and B-cell depletion, and other sphingosine-1-receptor modulators such as ozanimod and ponesimod are under development. Moreover, some therapeutic approaches in preclinical stages are under development. In this review, we will summarize the newest therapeutic development in the field of progressive MS of the last 3 years, and shed light on auspicious substances with similar mechanisms and new developments in the therapeutic pipeline, presumably supporting a bright future for progressive MS treatment.