Disease progression after bone marrow transplantation in a model of multiple sclerosis is associated with chronic microglial and glial progenitor response

Evaluation of treatment of experimentally induced canine model of multiple sclerosis using laser activated non-expanded adipose derived stem cells

Multiple sclerosis (MS) is a progressive demyelinating disease of the central nervous system that destroys oligodendrocytes. This work aims to evaluate the treatment of experimentally induced MS in dogs using laser activated non-expanded adipose derived stem cells. The results showed amelioration of the clinical signs over time confirmed by the resolution of the previous lesions on MRI. Positive migration of the injected cells to the site of lesion, increased remyelination detected by Myelin Basic Proteins, positive differentiation into Olig2 positive oligodendrocytes, prevented the glial scar formation and restored axonal architecture. The study concluded that treatment using laser activated stem cells holds a promising therapeutic option for treatment of MS in a canine model.

Expression of the neuroprotective protein aryl hydrocarbon receptor nuclear translocator 2 correlates with neuronal stress and disability in models of multiple sclerosis

Background

Axonal degeneration and neuronal loss have been described as the major causes of irreversible clinical disability in multiple sclerosis (MS). The aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) protein has been associated with neuroprotection in models of ischemia and neuronal responses to stressors.

Methods

To characterize its potential to influence inflammatory neurodegeneration, we examined ARNT2 expression in the experimental autoimmune encephalomyelitis (EAE) model of MS and characterized mediators that influence ARNT2 expression as well as plausible partners and targets.

Results

Arnt2 message and protein levels dropped significantly in EAE spinal cords as disease developed and were lowest at peak disability. ARNT2 expression is prominent in neuronal cell bodies within the gray matter with some staining in glial fibrillary acidic protein (GFAP)⁺ astrocytes in healthy animals. At peak disease, ARNT2 expression is reduced by 20–50% in gray matter neurons compared to healthy controls. ARNT2 intensity in neurons throughout the EAE spinal cord correlated inversely with the degree of immune cell infiltration (r = − 0.5085, p < 0.01) and axonal damage identified with SMI32 staining (r = − 0.376, p = 0.032). To understand the relationship between ARNT2 expression and neuronal health, we exposed enriched cortical cultures of neurons to hydrogen peroxide (H₂O₂) to mimic oxidative stress. H₂O₂ at lower doses rapidly increased ARNT2 protein levels which returned to baseline within 3–4 h. Exposure to higher doses of H₂O₂) dropped ARNT2 levels below baseline, preceding cytotoxicity measured by morphological changes and lactate dehydrogenase release from cells. Decreases in ARNT2 secondary to staurosporine and H₂O₂ preceded increases in cleaved caspase 3 and associated apoptosis. We also examined expression of neuronal pas 4 (Npas4), whose heterodimerization with ARNT2 drives expression of the neurotrophic factor brain-derived neurotrophic factor (Bdnf). Like ARNT2, Npas4 levels also decline at the onset of EAE and are linked to decreases in Bdnf. In vitro, H₂O₂ exposure drives Npas4 expression that is tied to increases in Bdnf.

Conclusion

Our data support ARNT2 as a neuronal transcription factor whose sustained expression is linked to neuronal and axonal health, protection that may primarily be driven through its partnering with Npas4 to influence BDNF expression.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1290-6) contains supplementary material, which is available to authorized users.

Autologous Bone Marrow Transplantation in Multiple Sclerosis: Biomarker Relevance for Patient Recruitment and Follow up

BACKGROUND

Despite the current availability of disease modifying therapies for the treatment of multiple sclerosis, there are still patients who suffer from severe neurological dysfunction in the relapsing-remitting or early progressive forms of the disease. For these patients autologous hematopoietic stem cell transplant offers an important therapeutic solution to prevent progression to irreversible disability. In spite of multiple studies in the last two decades, patient inclusion criteria, protocols for peripheral blood stem cell mobilization and bone marrow cell conditioning and methodology of follow up for autologous hematopoietic stem cell transplant in multiple sclerosis have not been strictly unified.

METHODS

We reviewed five recent clinical studies that confirmed the positive outcome of transplant in spite of disclosing significant differences in methodology of enrollment including patient disease subtypes, disease duration range, disability, regimens of peripheral blood stem cell mobilization and bone marrow cell conditioning, scheduling of imaging studies after transplant, and absence of laboratory biomarkers consistently applied to these studies.

RESULTS

Therapy with autologous hematopoietic stem cell transplant has shown best results among young individuals with severe relapsing-remitting or early progressive disease through its ability to maintain no evidence of disease activity status in a significantly higher proportion of patients after transplant in comparison to patients treated with disease modifying therapies. Important cross-sectional differences in the reviewed studies were found.

CONCLUSION

A specific and careful selection of biomarkers, based on the current physiopathological mechanisms known to result in multiple sclerosis, will contribute to a better and earlier patient selection for autologous hematopoietic stem cell transplant and follow up process. An objective and measurable response could be obtained with the determination of biomarkers at the onset of treatment and after follow-up on reconstitution of the immune response. The application of such parameters could also help further our understanding of pathogenesis of the disease.

Quantitative Analysis of Cerebrospinal Fluid Brain Derived Neurotrophic Factor in the Patients with Multiple Sclerosis

Multiple sclerosis (MS) is the most common cause of nontraumatic neurological disability in Europe and North America. Growth factor expression could participate in the repair process of the demyelinating disease. Among growth factors, brain derived neurotrophic factors (BDNF) has been demonstrated to play an important role in neuronal and axonal survival. In the central nervous system (CNS), neurons are the main source of BDNF. Another potential source are activated astrocytes, which are present in inflamed areas in the CNS as shown in MS. In this study, total protein concentration (TPC) and BDNF levels in the cerebrospinal fluid (CSF) samples from the patients with MS (n = 48) and control subjects (n = 53) were measured using a Bio-Rad protein assay and enzyme linked immunosorbent assay (ELISA). No significant change in the CSF TPC of patients with MS was seen as compared to normal CSF. The presence of BDNF in the CSF samples was shown by Western blot. Using ELISA, it was shown that the level of BDNF in the MS CSF is higher than in normal CSF. It is concluded that BDNF is a constant component of human CSF. Moreover, it could be implicated in the pathophysiology of MS.

Myeloid cell-based therapies in neurological disorders: How far have we come?

The pathogenesis of neurological disorders such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) is multifactorial and incompletely understood. The development of therapies for these disorders of the central nervous system (CNS) is thus far very challenging. Neuroinflammation is one of the processes that contribute to the pathogenesis of CNS diseases, and therefore represents an important therapeutic target. Myeloid cells derived from the bone marrow are ideal candidates for cell therapy in the CNS as they are capable of targeting the brain and providing neuroprotective and anti-inflammatory effects. In this review, experimental and clinical evidence for the therapeutic potential of myeloid cells in neurological disorders will be discussed. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

Autologous bone marrow transplantation for the treatment of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system and represents one of the leading causes of neurologic disability in young adults. Current treatments for MS have shown limited efficacy in patients with either a progressive or an aggressive disease course. Hematopoietic stem cell transplantation (HSCT) has been proposed to control or even cure refractory cases of MS. Indeed, HSCT is able to temporarily eradicate the autoreactive cells and to reset the aberrant immune response to self-antigens. In the last decade, owing to the growing experience in selecting the most appropriate patients to transplant and the recent advances in chemotherapeutic and support regimens, the transplant-related mortality of autologous HSCT in MS patients dropped down to 1,3 % and the progression-free survival ranges from 47 % to 100 %. Altogether, these data support autologous HSCT as a possible second-line therapy for refractory MS.

Hyaluronic acid and neural stem cells: implications for biomaterial design

While in the past hyaluronic acid (HA) was considered a passive structural component, research over the past few decades has revealed its diverse and complex biological functions resulting in a major ideological shift. This review describes recent advances in biological interactions of HA with neural stem cells, with a focus on leveraging these interactions to develop advanced biomaterials that aid regeneration of the central nervous system.

Autologous hematopoietic stem cell transplantation as a treatment option for aggressive multiple sclerosis

OPINION STATEMENT

Despite the development of several injectable or oral treatments for relapsing-remitting multiple sclerosis (RRMS), it remains difficult to treat patients with aggressive disease, and many of these continue to develop severe disability. During the last two decades autologous hematopoietic stem cell transplantation (aHSCT) has been explored with the goal to eliminate an aberrant immune system and then re-install a healthy and tolerant one from hematopoietic precursor cells that had been harvested from the patient prior to chemotherapy. Clinical studies have shown that aHSCT is able to completely halt disease activity in the majority of patients with aggressive RRMS. Research on the mechanisms of action supports that aHSCT indeed leads to renewal of a healthy immune system. Below we will summarize important aspects of aHSCT and mention the currently best-examined regimen.

Myelin antigen load influences antigen presentation and severity of central nervous system autoimmunity

This study was designed to understand the impact of self-antigen load on manifestation of organ specific autoimmunity. Using a transgenic mouse model characterized by CNS hypermyelination, we show that larger myelin content results in greater severity of experimental autoimmune encephalomyelitis attributable to an increased number of microglia within the hypermyelinated brain. We conclude that a larger self-antigen load affects an increase in number of tissue resident antigen presenting cells (APCs) most likely due to compensatory antigen clearance mechanisms thereby enhancing the probability of productive T cell-APC interactions in an antigen abundant environment and results in enhanced severity of autoimmune disease.

Experimental autoimmune encephalomyelitis (EAE) as a model for multiple sclerosis (MS)

Experimental autoimmune encephalomyelitis (EAE) is the most commonly used experimental model for the human inflammatory demyelinating disease, multiple sclerosis (MS). EAE is a complex condition in which the interaction between a variety of immunopathological and neuropathological mechanisms leads to an approximation of the key pathological features of MS: inflammation, demyelination, axonal loss and gliosis. The counter-regulatory mechanisms of resolution of inflammation and remyelination also occur in EAE, which, therefore can also serve as a model for these processes. Moreover, EAE is often used as a model of cell-mediated organ-specific autoimmune conditions in general. EAE has a complex neuropharmacology, and many of the drugs that are in current or imminent use in MS have been developed, tested or validated on the basis of EAE studies. There is great heterogeneity in the susceptibility to the induction, the method of induction and the response to various immunological or neuropharmacological interventions, many of which are reviewed here. This makes EAE a very versatile system to use in translational neuro- and immunopharmacology, but the model needs to be tailored to the scientific question being asked. While creating difficulties and underscoring the inherent weaknesses of this model of MS in straightforward translation from EAE to the human disease, this variability also creates an opportunity to explore multiple facets of the immune and neural mechanisms of immune-mediated neuroinflammation and demyelination as well as intrinsic protective mechanisms. This allows the eventual development and preclinical testing of a wide range of potential therapeutic interventions.

Intravenous administration of human embryonic stem cell-derived neural precursor cells attenuates cuprizone-induced central nervous system (CNS) demyelination

AIMS

Previous studies have demonstrated the therapeutic potential for human embryonic stem cell-derived neural precursor cells (hES-NPCs) in autoimmune and genetic animal models of demyelinating diseases. Herein, we tested whether intravenous (i.v.) administration of hES-NPCs would impact central nervous system (CNS) demyelination in a cuprizone model of demyelination.

METHODS

C57Bl/6 mice were fed cuprizone (0.2%) for 2 weeks and then separated into two groups that either received an i.v. injection of hES-NPCs or i.v. administration of media without these cells. After an additional 2 weeks of dietary cuprizone treatment, CNS tissues were analysed for detection of transplanted cells and differences in myelination in the region of the corpus callosum (CC).

RESULTS

Cuprizone-induced demyelination in the CC was significantly reduced in mice treated with hES-NPCs compared with cuprizone-treated controls that did not receive stem cells. hES-NPCs were identified within the brain tissues of treated mice and revealed migration of transplanted cells into the CNS. A limited number of human cells were found to express the mature oligodendrocyte marker, O1, or the astrocyte marker, glial fibrillary acidic protein. Reduced apoptosis and attenuated microglial and astrocytic responses were also observed in the CC of hES-NPC-treated mice.

CONCLUSIONS

These findings indicated that systemically administered hES-NPCs migrated from circulation into a demyelinated lesion within the CNS and effectively reduced demyelination. Observed reductions in astrocyte and microglial responses, and the benefit of hES-NPC treatment in this model of myelin injury was not obviously accountable to tissue replacement by exogenously administered cells.

NG2 cells are not a major source of reactive astrocytes after neocortical stab wound injury

NG2 cells are an abundant glial cell type in the adult brain. They are distinct from astrocytes, mature oligodendrocytes, and microglia. NG2 cells generate oligodendrocytes and a subpopulation of protoplasmic astrocytes in the ventral forebrain during development. To determine whether NG2 cells generate reactive astrocytes in the lesioned brain, stab wound injury was created in adult NG2creBAC:ZEG double transgenic mice, in which enhanced green fluorescent protein (EGFP) is expressed in NG2 cells and their progeny, and the phenotype of the EGFP(+) cells was analyzed at 10 and 30 days post lesion (dpl). The majority (>90%) of the reactive astrocytes surrounding the lesion that expressed glial fibrillary acidic protein (GFAP) lacked EGFP expression, and conversely the majority (>90%) of EGFP(+) cells were GFAP-negative. However, 8% of EGFP(+) cells co-expressed GFAP at 10 dpl. Most of these EGFP(+) GFAP(+) cells were morphologically distinct from hypertrophic reactive astrocytes and exhibited weak GFAP expression. NG2 was detected in a fraction of the EGFP(+) GFAP(+) cells found at 10 dpl. By 30 dpl the number of EGFP(+) GFAP(+) cells had decreased more than four-fold from 10 dpl. A similar transient appearance of EGFP(+) GFAP(+) cells with simple morphology was observed in NG2creER™:ZEG double transgenic mice in which EGFP expression had been induced in NG2 cells prior to injury. NG2 cell-specific deletion of the oligodendrocyte lineage transcription factor Olig2 using NG2creER™:Olig2(fl/fl) :ZEG triple transgenic mice did not increase the number of EGFP(+) reactive astrocytes. These findings suggest that NG2 cells are not a major source of reactive astrocytes in the neocortex.

Positron emission tomography imaging in multiple sclerosis-current status and future applications

BACKGROUND

Multiple Sclerosis (MS) is traditionally considered as a central nervous system (CNS) white matter inflammatory disease. However, recent studies have focused on the neurodegenerative aspects of the disease, which occur early in the pathological process, providing an opportunity for therapeutic intervention and application of neuroprotective strategies. The relationship between neural inflammation and cell death remains controversial. The recent development of new radiolabelled ligands provides positron emission tomography (PET) imaging with a role for studying early aspects of the MS pathology.

METHODS

We provide an overview of current PET research in MS, particularly focussing on possible applications of new radioligands for studying inflammation and neurodegenerative processes.

RESULTS

Pathological aspects of neuroinflammation, axonal degeneration and neuronal repair may be explored in vivo with selective PET tracers. Specific radioligands for the cannabinoid system may be applied in MS research to understand the role of this neurotransmitter system in the pathogenesis of the disease.

CONCLUSIONS

PET imaging represents a promising tool for elucidating controversial aspects of MS pathology and for the assessment of selective and potentially neuroprotective therapies.

IRF-1 signaling in central nervous system glial cells regulates inflammatory demyelination

The present study provides evidence that interferon regulatory factor 1 (IRF-1) signaling in glial cells is involved in the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). Using a bone marrow chimera model of EAE, we demonstrated that CNS IRF-1 regulates inflammatory demyelination and disease severity independently of the peripheral immune cells. In addition, we identified Caspase 1, a pro-inflammatory and pro-apoptotic molecule, as an important transcriptional target of IRF-1. The findings of our study indicate that IRF-1 signaling in glial cells serves as a final common pathway of inflammatory demyelination and may have important clinical implications in MS.

Evaluation of bone marrow- and brain-derived neural stem cells in therapy of central nervous system autoimmunity

Adult subventricular zone (SVZ)-derived neural stem cells (NSCs) have therapeutic effects in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, SVZ precursor cells as a source of NSCs are not readily accessible for clinical application. In the present study, we demonstrate that NSCs derived from bone marrow (BM) cells exhibit comparable morphological properties as those derived from SVZ cells and possess a similar ability to differentiate into neurons, astrocytes, and oligodendrocytes both in vitro and in vivo. Importantly, both types of NSCs suppressed chronic experimental autoimmune encephalomyelitis to a comparable extent on transplantation. Mechanisms underlying the therapeutic effects of NSCs include immunomodulation in the periphery and the central nervous system (CNS), neuron/oligodendrocyte repopulation by transplanted cells, and enhanced endogenous remyelination and axonal recovery. Furthermore, we provide evidence for the trans-differentiation of transplanted BM-NSCs into neural cells in the CNS, while no fusion of these cells with host neural cells was detected. This is the first study that directly compares SVZ- versus BM-NSCs with regard to in vivo neural differentiation and anti-inflammatory and therapeutic effects on CNS inflammatory demyelination. Their virtually identical therapeutic potential, greater accessibility, and autologous properties make BM-NSCs a novel and highly applicable substitute for SVZ-NSCs in cell-based multiple sclerosis therapies.

Hematopoietic SCT for the treatment of multiple sclerosis

Multiple sclerosis (MS) is the leading autoimmune indication for autologous hematopoietic SCT (aHSCT). Patient selection criteria and transplant interventions have been refined through a series of cohort and registry studies. High- and low-intensity chemotherapy-based conditioning regimens have been used, creating trade-offs between toxicity and effectiveness. TBI has been associated with greater toxicity and poor outcomes. aHSCT stops MS relapses and lessens the disability in malignant MS, which otherwise rapidly incapacitates patients. Better responses occur in progressive MS earlier in the disease when it has a more inflammatory nature. aHSCT prevents further disability in many patients, but some actually recover from their infirmities. Current regimens and supportive care result in very low morbidity and mortality. MS patients experience unique complications in addition to the expected toxicities. Cytokines used alone for stem-cell mobilization may induce MS flares but are safe to be used in combination with steroids or cytotoxic agents. Urinary tract infections, herpes virus reactivation and an engraftment syndrome may occur early after aHSCT. Rarely secondary autoimmune diseases have been reported late after HSCT. Increasing experience in caring for patients with MS has reduced the frequency and severity of toxicity. Conceived as an opportunity to 'reboot' a tolerant immune system, aHSCT is successful in treating patients with MS that is refractory to conventional immunomodulatory drugs.

Hematopoietic cell transplantation for autoimmune disease: updates from Europe and the United States

Considerable advances have been made in our understanding of the immunobiology of autoimmune disease and its treatment with hematopoietic cell transplantation (HCT). In autoimmune disorders, the reconstituted immune system following lymphoablation and autologous HCT yields qualitative changes in immune defects and modifications in adaptive immune responses. Seminal experiments in animals demonstrated that allogeneic or autologous HCT could prevent progression or reverse organ damage from inherited (genetic) or acquired (antigen induced) autoimmune diseases. Convincing animal and clinical data now show that after HCT, the immune system is normalized and "reset". Following autologous transplantation, this resetting occurs via repertoire replacement. It is currently being studied whether and to what extent suppression of inflammation after HCT is due to reregulation of function or due to the eradication of disease associated T and/or B cell populations. There are now a number of published clinical reports with sufficient follow-up for determinations of safety and efficacy of HCT for autoimmune diseases. On behalf of colleagues in the European League Against Rheumatism (EULAR) and the European Group for Blood and Marrow Transplantation (EBMT), we review the experience with more than 1000 transplants for autoimmune disease in Europe along with the three major multinational randomized trials in for systemic sclerosis (SSc, the ASTIS study), multiple sclerosis (MS, the ASTIMS study), and Crohn's disease (CD, the ASTIC study). Completed phase II studies in the USA of transplantation for severe SSc, SLE and MS yield promising results. For individuals with SSc, there is dramatic improvement/resolution of dermal fibrosis and stabilization/improvement of pulmonary dysfunction reported up to 8 years after lymphoablative conditioning and autologous HCT. Currently, randomized phase III studies are recruiting subjects in the USA with SSc, MS and CD. In addition, 9 other phase I and II trials in the USA are recruiting patients with autoimmune diseases for nonmyeloablative transplants from allogeneic stem cell donors. Research opportunities abound, but recruitment challenges restrict study entry due to organ impairment from advanced autoimmune disease or insurance denial of coverage for HCT. However, within several NIH sponsored trials there are ongoing immunologic, genomic and mechanistic studies to further understand the molecular mechanisms of autoimmunity, immune regulation and response to treatment. These clinical trials will provide basic scientists with insight into immunoregulatory pathways and clinicians with a context to weigh the progress and evidence in this evolving treatment for autoimmune diseases.

Glatiramer acetate in combination with minocycline in patients with relapsing--remitting multiple sclerosis: results of a Canadian, multicenter, double-blind, placebo-controlled trial

Minocycline is proposed as an add-on therapy to improve the efficacy of glatiramer acetate in relapsing-remitting multiple sclerosis. The effect of minocycline plus glatiramer acetate was evaluated in this double-blind, placebo-controlled study by determining the total number of T1 gadolinium-enhanced lesions at months 8 and 9 in patients who were starting glatiramer acetate and had at least one T1 gadolinium-enhanced lesion on screening magnetic resonance imaging. Forty-four participants were randomized to either minocycline 100 mg twice daily or matching placebo for 9 months as add-on therapy. They were assessed at screening and months 1, 3, 6, 8 and 9. Forty participants completed the study. Compared with glatiramer acetate/placebo, glatiramer acetate/minocycline reduced the total number of T1 gadolinium-enhanced lesions by 63% (mean 1.47 versus 2.95; p = 0.08), the total number of new and enlarging T2 lesions by 65% (mean 1.84 versus 5.14; p = 0.06), and the total T2 disease burden (p = 0.10). A higher number of gadolinium-enhanced lesions were present in the glatiramer acetate/minocycline group at baseline; this was incorporated into the analysis of the primary endpoint but makes interpretation of the data more challenging. The risk of relapse tended to be lower in the combination group (0.19 versus 0.41; p = NS). Treatment was safe and well tolerated. We conclude that efficacy endpoints showed a consistent trend favoring combination treatment. As minocycline is a relatively safe oral therapy, further study of this combination is warranted in relapsing-remitting multiple sclerosis.

Androgen depletion increases the efficacy of bone marrow transplantation in ameliorating experimental autoimmune encephalomyelitis

Bone marrow transplantation (BMT) potentially represents a novel therapy for the amelioration and even cure for multiple sclerosis (MS). It has important advantages over immunosuppressive drug treatments because, while effecting broad-based ablation of the immune system and autoreactive cells, it provides an important means for overcoming the resultant immunodeficiency, while possibly restoring self-tolerance. However, both of these benefits are predicated on a functional thymus that undergoes profound age-induced atrophy from puberty. Reversal of thymic atrophy has been achieved by several procedures, including removal of sex steroids by surgical or chemical (LHRH agonist) castration. Using a murine model of MS, experimental autoimmune encephalomyelitis (EAE), we combined BMT with androgen depletion to induce immune regeneration, and investigated the kinetics of increased thymic function on immune reconstitution and disease reduction. We show that androgen depletion significantly increased the efficacy of BMT to ameliorate the clinical signs of EAE while concurrently restoring the periphery with increased naive and regulatory lymphocytic populations. Upon rechallenge, mice with a regenerated thymus had a slower onset of clinical symptoms compared with mice undergoing BMT only. These results suggest that thymic regeneration strategies may be used as a complement to conventional BMT protocols for the treatment of MS.

Autologous haematopoietic stem-cell transplantation in multiple sclerosis

Intense immunosuppression followed by autologous haematopoietic stem-cell transplantation has been assessed over the past few years as a possible new therapeutic strategy in severe forms of multiple sclerosis. Pioneering studies began in 1995, and since then, more than 400 patients worldwide have been treated with this procedure. Small uncontrolled studies show that about 60-70% of treated cases do not progress in the follow-up period of at least 3 years. Transplant-related mortality, which was 5-6% in the first reported series, has reduced in the past 5 years to 1-2%. Relapses dramatically decrease and inflammatory MRI activity is almost completely suppressed. Autologous haematopoietic stem-cell transplantation is associated with qualitative immunological changes in the blood, suggesting that, beyond its immunosuppressive potential, it could also have some beneficial effect for the resetting of the immune system. Patients with severe, rapidly worsening multiple sclerosis who are unresponsive to approved therapies could be candidates for this treatment, but its clinical efficacy has still to be shown in large, prospective, controlled studies.

Autologous and allogeneic hematopoietic stem cell transplantation for Multiple Sclerosis: perspective on mechanisms of action

Multiple Sclerosis (MS) is a frequent demyelinating immune-mediated disease of the central nervous system (CNS) that affects principally young adults and leads to severe physical and cognitive impairment. The current standard treatment makes use of the immune modulators beta-interferon, glatiramer acetate and natalizumab, or immunosuppressants such as mitoxantrone. However, these agents are only partially effective and in a number of patients fail to achieve satisfactory disease control. Autologous hematopoietic stem cell transplantation (HSCT) is being explored in the treatment of severe MS as a means of delivering high-dose immunosuppression followed by 'rescue' of the immuno-hematopoietic system with autologous HSC. The potential therapeutic benefit is based on the concept of so-called 'resetting' the immune system. The use of allogeneic HSCT as a possible therapeutic approach for severe MS is inspired by case reports of MS patients that underwent allogeneic HSCT for a concomitant hematological malignancy, and subsequently is supported by data from rodent models of MS. Allogeneic HSCT may offer specific therapeutic effects, such as the replacement of the autoreactive immune compartment by healthy allogeneic cells and the development of a graft-versus-autoimmunity (GVA) effect. Here, we review the currently available experimental and clinical evidence to support the role of autologous and allogeneic HSCT in MS.

The newly synthesized pool of dopamine determines the severity of methamphetamine-induced neurotoxicity

The neurotransmitter dopamine (DA) has long been implicated as a participant in the neurotoxicity caused by methamphetamine (METH), yet, its mechanism of action in this regard is not fully understood. Treatment of mice with the tyrosine hydroxylase (TH) inhibitor alpha-methyl-p-tyrosine (AMPT) lowers striatal cytoplasmic DA content by 55% and completely protects against METH-induced damage to DA nerve terminals. Reserpine, by disrupting vesicle amine storage, depletes striatal DA by more than 95% and accentuates METH-induced neurotoxicity. l-DOPA reverses the protective effect of AMPT against METH and enhances neurotoxicity in animals with intact TH. Inhibition of MAO-A by clorgyline increases pre-synaptic DA content and enhances METH striatal neurotoxicity. In all conditions of altered pre-synaptic DA homeostasis, increases or decreases in METH neurotoxicity paralleled changes in striatal microglial activation. Mice treated with AMPT, l-DOPA, or clorgyline + METH developed hyperthermia to the same extent as animals treated with METH alone, whereas mice treated with reserpine + METH were hypothermic, suggesting that the effects of alterations in cytoplasmic DA on METH neurotoxicity were not strictly mediated by changes in core body temperature. Taken together, the present data reinforce the notion that METH-induced release of DA from the newly synthesized pool of transmitter into the extracellular space plays an essential role in drug-induced striatal neurotoxicity and microglial activation. Subtle alterations in intracellular DA content can lead to significant enhancement of METH neurotoxicity. Our results also suggest that reactants derived from METH-induced oxidation of released DA may serve as neuronal signals that lead to microglial activation early in the neurotoxic process associated with METH.

Emerging therapies for multiple sclerosis

This review examines the mode of action, safety profile and clinical efficacy of some of the most promising new therapeutic strategies for multiple sclerosis. Autologous hematopoietic stem cell transplantation can regenerate a new and tolerant immune system and is a potentially effective rescue therapy in a subset of patients with aggressive forms of MS refractory to approved immunomodulatory and immunosuppressive agents. High-dose cyclophosphamide without stem cell support is suggested to induce prolonged remissions through similar immunological mechanisms with less toxicity. Fingolimod (FTY720) is a novel oral immunomodulating agent that acts through preventing lymphocyte recirculation from lymphoid organs. Monoclonal antibody therapy has provided scientists and clinicians the opportunity to rationally direct the therapeutic intervention against specific molecules. Targeting molecules of the immune system such as CD52 (alemtuzumab), CD25 (daclizumab), VLA-4 (natalizumab) and CD20 (rituximab) have resulted in potent immunomodulatory effects through sometimes unpredicted mechanisms. The potential of immunoglobulins to induce remyelination in the CNS is being investigated in an attempt to develop therapies promoting tissue repair and functional recovery. The evidence supporting the potential of these emerging immunotherapies suggests that strong progress is being made in the development of effective cures for multiple sclerosis.