Granagard administration prolongs the survival of human mesenchymal stem cells transplanted into a mouse model of multiple sclerosis.

The clinical effect of human Mesenchymal stem cells (hMSCs) transplanted into EAE mice/MS patients is short lived due to poor survival of the transplanted cells. Since Granagard, a nanoformulation of pomegranate seed oil, extended the presence of Neuronal Stem cells transplanted into CJD mice brains, we tested whether this safe food supplement can also elongate the survival of hMSCs transplanted into EAE mice. Indeed, pathological studies 60 days post transplantation identified human cells only in brains of Granagard treated mice, concomitant with increased clinical activity. We conclude that Granagard may prolong the activity of stem cell transplantation in neurological diseases.

Effects of Mesenchymal Stem Cell Transplantation on Cerebrospinal Fluid Biomarkers in Progressive Multiple Sclerosis.

BACKGROUND: Neurofilament light chains (NF-L) were shown to serve as a reliable biomarker of neurodegeneration in multiple sclerosis (MS). The chemokine receptor CXCL13 was shown to correlate with CNS inflammatory activity and to predict the future progression of MS. OBJECTIVE: To evaluate the levels of NF-L and CXCL13 in the cerebrospinal fluid (CSF) following treatment with mesenchymal stem cells (MSC) in patients with progressive MS. METHODS: The CSF samples were obtained from 48 patients with progressive MS who participated in a double-blind randomized phase II clinical trial that tested the effects of intrathecal (IT) or intravenous (IV) transplantation of mesenchymal stem cells (MSC), at baseline (before the first injection of the MSC) and at 6 months following treatment with MSC, or sham treatment. The CSF specimens were tested in a blinded way, using a single-molecule array (SIMOA) technique. FINDINGS: The CSF levels of NF-L were significantly lower at 6 months following treatment with MSC-IT when compared with the baseline, pre-treatment measurements (P = .026, Wilcoxon paired test). Nine out of 15 tested patients in the MSC-IT group had a reduction in NF-L levels of more than 50% (median decrease: -4449 pg/mL) when compared with 5/15 in the MSC-IV group (median decrease: -151 pg/mL) and 1/15 in the placebo group (median increase: +2450 pg/mL) (P = .001 for MSC-IT vs. placebo, chi-square test). CXCL13 levels were also reduced at 6 months following MSC-IT treatment but not to a statistically significant level. CONCLUSIONS: Our findings indicate possible neuroprotective effects of MSC transplantation in patients with MS. CLINICAL TRIAL REGISTRATION: NCT02166021.

A phase II clinical trial with repeated intrathecal injections of autologous mesenchymal stem cells in patients with amyotrophic lateral sclerosis.

Background: Mesenchymal stem cells (MSC) were shown to induce beneficial effects in animal models of neurodegeneration and in pilot human trials in multiple sclerosis and amyotrophic lateral sclerosis (ALS). Aim: An open-label, clinical trial to evaluate the safety and efficacy of repeated intrathecal administrations of autologous-MSC in ALS-patients. Methods: The study included 20 subjects (age: 20-70) with definite diagnosis of ALS and Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R) score of >20. The patients were treated with 1-4 intrathecal injections of MSC, at intervals of 3-6 months. The primary endpoints were safety and tolerability. Efficacy measurements including ALSFRS-R score and forced vital capacity (FVC), were assessed as secondary endpoints. Results: No serious adverse events were observed during the whole period of the trial. One patient withdrew from the study before the first injection. The monthly rate of progression in ALSFRS-R was ameliorated by more than 25% in 15/19 patients between the 1st and 2nd injection (mean improvement of 107.1%); in 11/12 between the 2nd and 3rd injection and in 8/10 between the 3rd and 4th injection. Overall, during the whole period till the last transplantation 13 patients had a >25% improvement in the slope of progression of ALSFRS-R (mean improvement of 47.4%, p < 0.0038, Wilcoxon rank signed test). 7 out of 19 patients actually improved clinically (range of increase in ALSFRS-R: +1 to +4 degrees) after the first transplantation and 5 remained improved after the second cycle. The response rate correlated with the time-intervals between the injections. Conclusion: The results of our study show that repeated intrathecal injections of autologous MSC was safe in patients with ALS and provide indications of medium-term clinical benefits that were related to the intervals between the administrations of the cells. Larger studies are needed to confirm these observations.

Long-Term Clinical and Immunological Effects of Repeated Mesenchymal Stem Cell Injections in Patients With Progressive Forms of Multiple Sclerosis.

Background: Mesenchymal stem cells (MSC) were shown to possess immunomodulatory and neurotrophic effects. Our previous trials, have shown that intrathecal (IT) and intravenous (IV) administration of MSCs were safe and provided indications of beneficial clinical effects. Methods: This is an open prospective study to evaluate the safety and the long-term clinical and immunological effects of multiple injections of autologous MSCs in 24 patients with active-progressive MS. At inclusion, the mean age of the patients was 47.0 ± 9.22, and the mean EDSS score was 6.75 ± 0.68 (range: 5.5-7.5). Patients were initially treated with 1 ×106 MSCS/kg of body weight (IT + IV) and subsequently with up to additional eight courses of MSCs, at intervals of 6-12 months. The duration of the trial was 4 years. Results: No serious, treatment-related adverse events were observed during the follow-up period. Twenty-two of the 24 patients were either stable or improved at the last follow-up visit. Ten patients had a lower than baseline EDSS at the last follow-up (nine were among those who received >2 treatments and one in the subgroup of ≤ 2 treatments, p = 0.04). The mean EDSS score reduced from 6.75 ± 0.68 at baseline to 6.42 ± 0.84 at the last visit, during a median follow-up period of 27.8 months (p = 0.028). Immunological follow-up showed a transient upregulation of CD4+CD25+FoxP3+ cells and downregulation of the proliferative ability of lymphocytes. Conclusions: Repeated MSC treatments in patients with progressive MS were shown safe at the short/intermediate term and induced clinical benefits (especially in patients treated with >2 injections) that lasted for up to 4 years, paralleled by short-term immunomodulatory effects. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT04823000.

Synergistic neuroprotective effects of Fingolimod and mesenchymal stem cells (MSC) in experimental autoimmune encephalomyelitis.

Fingolimod (Gilenya™) is an effective oral medication approved for relapsing-remitting multiple sclerosis (MS), albeit less effective in chronic disease. Its main mechanism of action is through peripheral immunomodulation but neuroprotective effects may also be involved. Mesenchymal stem cells (MSC) were shown to exert immunomodulatory and neurotrophic effects in the model of multiple sclerosis (experimental autoimmune encephalomyelitis-EAE). The use of combination treatments in chronic diseases such as MS, has long been advocated and may result in improvement of the beneficial effects of each one of them. We tested the in vitro effects of Fingolimod (FTY720) on MSC and the in vivo effect of such combination treatment in the model of EAE. Fingolimod did not affect in any detrimental way the basic features of MSCs and it promoted their migration and proliferation ability .Moreover, Fingolimod induced neurotrophic factors secretion and suppressed the production of pro-inflammatory cytokines from astrocytes and microglia, in vitro. In vivo, the combined treatment of FTY720 and MSC (either by the intravenous or the intra-cerebroventricular route of administration) resulted in synergistic clinical beneficial effects compared to FTY720 or MSC alone, paralleled by a significant reduction of inflammatory CNS infiltrations and of axonal loss. These data may indicate a synergism of fingolimod with MSC and may support future combinations of immunomodulatory drugs with cellular therapies for the improvement of the benefits in progressive forms of MS.

Beneficial effects of autologous mesenchymal stem cell transplantation in active progressive multiple sclerosis.

In this study (trial registration: NCT02166021), we aimed to evaluate the optimal way of administration, the safety and the clinical efficacy of mesenchymal stem cell (MSC) transplantation in patients with active and progressive multiple sclerosis. Forty-eight patients (28 males and 20 females) with progressive multiple sclerosis (Expanded Disability Status Scale: 3.0-6.5, mean : 5.6 ± 0.8, mean age: 47.5 ± 12.3) and evidence of either clinical worsening or activity during the previous year, were enrolled (between 2015 and 2018). Patients were randomized into three groups and treated intrathecally (IT) or intravenously (IV) with autologous MSCs (1 × 106/kg) or sham injections. After 6 months, half of the patients from the MSC-IT and MSC-IV groups were retreated with MSCs, and the other half with sham injections. Patients initially assigned to sham treatment were divided into two subgroups and treated with either MSC-IT or MSC-IV. The study duration was 14 months. No serious treatment-related safety issues were detected. Significantly fewer patients experienced treatment failure in the MSC-IT and MSC-IV groups compared with those in the sham-treated group (6.7%, 9.7%, and 41.9%, respectively, P = 0.0003 and P = 0.0008). During the 1-year follow-up, 58.6% and 40.6% of patients treated with MSC-IT and MSC-IV, respectively, exhibited no evidence of disease activity compared with 9.7% in the sham-treated group (P < 0.0001 and P < 0.0048, respectively). MSC-IT transplantation induced additional benefits on the relapse rate, on the monthly changes of the T2 lesion load on MRI, and on the timed 25-foot walking test, 9-hole peg test, optical coherence tomography, functional MRI and cognitive tests. Treatment with MSCs was well-tolerated in progressive multiple sclerosis and induced short-term beneficial effects regarding the primary end points, especially in the patients with active disease. The intrathecal administration was more efficacious than the intravenous in several parameters of the disease. A phase III trial is warranted to confirm these findings.

Cerebrospinal Fluid (CSF) Exchange Therapy with Artificial CSF Enriched with Mesenchymal Stem Cell Secretions Ameliorates Cognitive Deficits and Brain Pathology in Alzheimer's Disease Mice.

BACKGROUND: The high complexity of neurodegenerative diseases, including Alzheimer's disease (AD), and the lack of effective treatments point to the need for a broader therapeutic approach to target multiple components involved in the disease pathogenesis. OBJECTIVE: To test the efficacy of 'cerebrospinal fluid (CSF) exchange therapy' in AD-mice. This novel therapeutic approach we recently proposed is based on the exchange of the endogenous pathogenic CSF with a new and healthy one by drainage of the endogenous CSF and its continuous replacement with artificial CSF (aCSF) enriched with secretions from human mesenchymal stem cells (MSCs). METHODS: We treated AD-mice (amyloid-beta injected) with MSC secretions-enriched-aCSF using an intracerebroventricular CSF exchange procedure. Cognitive and histological analysis were performed. RESULTS: We show that the MSC secretions enriched CSF exchange therapy improved cognitive performance, paralleled with increased neuronal counts (NeuN positive cells), reduced astrocytic burden (GFAP positive cells), and increased cell proliferation and neurogenesis (Ki67 positive cells and DCX positive cells) in the hippocampus. This beneficial effect was noted on days 5-10 following 3-consecutive daily exchange treatments (3 hours a day). A stronger effect was noted using a more prolonged CSF exchange protocol (3-consecutive daily exchange treatments with 3 additional treatments twice weekly), with cognitive follow-up performed as early as 2-3 days after treatment. Some increase in hippocampal cell proliferation, but no change in the other histological parameters, was noticed when performing CSF exchange therapy using unenriched aCSF relative to untreated AD-mice, yet smaller than with the enriched aCSF treatment. CONCLUSION: These findings point to the therapeutic potential of the CSF exchange therapy using MSC secretions-enriched aCSF in AD, and might be applied to other neurodegenerative and dementia diseases.

Neuralized mesenchymal stem cells (NMSC) exhibit phenotypical, and biological evidence of neuronal transdifferentiation and suppress EAE more effectively than unmodified MSC.

In the last decade several studies employing stem cells-based therapies have been investigated as an optional treatment for multiple sclerosis. Several preclinical and few clinical studies tested the efficacy of mesenchymal stem cells as a potent candidate for such therapies. Here we suggest the option of "neuralization" of classical mesenchymal stem cells as a cellular structure that resembles neural stem cells as well as there differentiation by a unique procedure towards terminally differentiated neural cells suggesting that this cell population may be appropriate for clinical application in the CNS. We investigated whether neuralized MSC (NMSC) could promote repair and recovery after injection into mice with EAE. Injection of NMSC and differentiated NMSC starting at the onset of the chronic phase of disease improved neurological function compared to controls as well as compared to naïve MSC. Injection of NMSC and mainly differentiated correlated with a reduction in the inflammation as well as in the axonal loss/damage and reduced area of demyelination. These observations suggest that NMSC and differentiated NMSC may suggest a more potent cell-based therapy that naïve MSC in the treatment arsenal of multiple sclerosis.

Cerebrospinal Fluid (CSF) Exchange with Artificial CSF Enriched with Mesenchymal Stem Cell Secretions Ameliorates Experimental Autoimmune Encephalomyelitis.

The complexity of central nervous system (CNS) degenerative/inflammatory diseases and the lack of substantially effective treatments point to the need for a broader therapeutic approach to target multiple components involved in the disease pathogenesis. We suggest a novel approach directed for the elimination of pathogenic agents from the CNS and, in parallel, its enrichment with an array of neuroprotective substances, using a "cerebrospinal fluid (CSF) exchange" procedure, in which endogenous (pathogenic) CSF is removed and replaced by artificial CSF (aCSF) enriched with secretions of human mesenchymal stem cells (MSCs). MSCs produce a variety of neuroprotective agents and have shown beneficial effects when cells are transplanted in animals and patients with CNS diseases. Our data show that MSCs grown in aCSF secrete neurotrophic factors, anti-inflammatory cytokines, and anti-oxidant agents; moreover, MSC-secretions-enriched-aCSF exerts neuroprotective and immunomodulatory effects in neuronal cell lines and spleen lymphocytes. Treatment of experimental-autoimmune-encephalomyelitis (EAE) mice with this enriched-aCSF using an intracerebroventricular (ICV) CSF exchange procedure ("CSF exchange therapy") caused a significant delay in the onset of EAE and amelioration of the clinical symptoms, paralleled by a reduction in axonal damage and demyelination. These findings point to the therapeutic potential of the CSF exchange therapy using MSC-secretions-enriched-aCSF in inflammatory/degenerative diseases of the CNS.

Development of a Novel Backbone Cyclic Peptide Inhibitor of the Innate Immune TLR/IL1R Signaling Protein MyD88.

MyD88 is a cytoplasmic adaptor protein that plays a central role in signaling downstream of the TLRs and the IL1R superfamily. We previously demonstrated that MyD88 plays a critical role in EAE, the murine model of multiple sclerosis, and showed that the MyD88 BB-loop decoy peptide RDVLPGT ameliorates EAE. We now designed and screened a library of backbone cyclized peptides based on the linear BB loop peptide, to identify a metabolically stable inhibitor of MyD88 that retains the binding properties of the linear peptide. We identified a novel cyclic peptide protein mimetic that inhibits inflammatory responses to TLR ligands, and NFκB activation in response to IL-1 activation. The inhibitor, c(MyD 4-4), is metabolically stable in comparison to the linear peptide, blocks MyD88 in a specific manner, and inhibits MyD88 function by preventing MyD88 dimerization. Finally, treatment of mice with c(MyD 4-4) reduced the severity of clinical disease in the murine EAE model of multiple sclerosis. Thus, modulation of MyD88-dependent signaling using c(MyD 4-4) is a potential therapeutic strategy to lower innate immune inflammation in autoimmune CNS disease.

T-cell responses to distinct AQP4 peptides in patients with neuromyelitis optica (NMO).

BACKGROUND: Although antibodies to aquaporin-4(AQP4) are strongly associated with Neuromyelitis optica (NMO), the sole transfer of these antibodies is not sufficient to induce an NMO-like disease in experimental animals and T-cells and complement are also needed. Initial data indicating the presence of T-cell responses to AQP4 in patients with NMO, have beeen recently reported. OBJECTIVE: To evaluate the T-cell responses to specific AQP4 peptides/epitopes in patients with NMO and multiple sclerosis (MS). METHODS: Peripheral blood mononuclear cells (PBMCs) were obtained from 14 patients fulfilling the criteria for definite NMO and the proliferation responses to one of 15 distinct pentadecapeptides of AQP4, spanning the whole protein (except of its transmembrane parts) were tested by a standard [H3]-thymidine uptake assay and compared with those of 9 healthy controls and 7 MS patients. A cytometric bead array assay (CBA) and flow cytometry were used to evaluate cytokine (IFNγ, IL17, IL2, IL4, IL5, IL10 and TNFα) and chemokine (CXCL8, CCL5, CXCL10, CXCL9, CCL2) secretion by PHA-stimulated PBMCs and AQP4-specific T-cell lines. RESULTS: Four main immunodominant epitopes of the AQP4 protein (p137-151, p222-236, p217-231 and the p269-283) were identified in the NMO group. The first two epitopes (assigned as peptides 3 and 9) showed the highest sensitivity (~60% positivity), whereas the latter two (assigned as peptides 8 and 11), the higher specificity. Longitudinal follow up of 5 patients revealed changes in the epitope-specificities during the course of NMO. T-cell lines specific for the AQP4 peptides, produced from NMO patients (but not healthy donors) secreted mainly IL-17 and IL-10 and less IFNγ. CONCLUSIONS: Our findings indicate that T-cells bearing characteristics of both Th1 and Th17 T-cells and targeting specific immunodominant epitopes of the AQP4 protein might be involved in the pathogenesis of NMO.

Safety and Clinical Effects of Mesenchymal Stem Cells Secreting Neurotrophic Factor Transplantation in Patients With Amyotrophic Lateral Sclerosis: Results of Phase 1/2 and 2a Clinical Trials.

IMPORTANCE: Preclinical studies have shown that neurotrophic growth factors (NTFs) extend the survival of motor neurons in amyotrophic lateral sclerosis (ALS) and that the combined delivery of these neurotrophic factors has a strong synergistic effect. We have developed a culture-based method for inducing mesenchymal stem cells (MSCs) to secrete neurotrophic factors. These MSC-NTF cells have been shown to be protective in several animal models of neurodegenerative diseases. OBJECTIVE: To determine the safety and possible clinical efficacy of autologous MSC-NTF cells transplantation in patients with ALS. DESIGN, SETTING, AND PARTICIPANTS: In these open-label proof-of-concept studies, patients with ALS were enrolled between June 2011 and October 2014 at the Hadassah Medical Center in Jerusalem, Israel. All patients were followed up for 3 months before transplantation and 6 months after transplantation. In the phase 1/2 part of the trial, 6 patients with early-stage ALS were injected intramuscularly (IM) and 6 patients with more advanced disease were transplanted intrathecally (IT). In the second stage, a phase 2a dose-escalating study, 14 patients with early-stage ALS received a combined IM and IT transplantation of autologous MSC-NTF cells. INTERVENTIONS: Patients were administered a single dose of MSC-NTF cells. MAIN OUTCOMES AND MEASURES: The primary end points of the studies were safety and tolerability of this cell therapy. Secondary end points included the effects of the treatment on various clinical parameters, such as the ALS Functional Rating Scale-Revised score and the respiratory function. RESULTS: Among the 12 patients in the phase 1/2 trial and the 14 patients in the phase 2a trial aged 20 and 75 years, the treatment was found to be safe and well tolerated over the study follow-up period. Most of the adverse effects were mild and transient, not including any treatment-related serious adverse event. The rate of progression of the forced vital capacity and of the ALS Functional Rating Scale-Revised score in the IT (or IT+IM)-treated patients was reduced (from -5.1% to -1.2%/month percentage predicted forced vital capacity, P < .04 and from -1.2 to 0.6 ALS Functional Rating Scale-Revised points/month, P = .052) during the 6 months following MSC-NTF cell transplantation vs the pretreatment period. Of these patients, 13 (87%) were defined as responders to either ALS Functional Rating Scale-Revised or forced vital capacity, having at least 25% improvement at 6 months after treatment in the slope of progression. CONCLUSIONS AND RELEVANCE: The results suggest that IT and IM administration of MSC-NTF cells in patients with ALS is safe and provide indications of possible clinical benefits, to be confirmed in upcoming clinical trials. TRIAL REGISTRATION: clinicaltrials.gov Identifiers: NCT01051882 and NCT01777646.

Mesenchymal stem cells (MSC) derived from mice with experimental autoimmune encephalomyelitis (EAE) suppress EAE and have similar biological properties with MSC from healthy donors.

Several animal studies and few pilot clinical trials have tested the therapeutic potential of mesenchymal stem cells (MSC) in experimental autoimmune encephalomyelitis (EAE) and in multiple sclerosis (MS). In almost all of the preclinical studies, healthy animals (or humans) served as donors of the MSCs. This setting does not accurately simulate the clinical situation of autologous transplantation in patients with MS. In the current research we used MSC isolated from mice with EAE in order to mimic human autologous transplantation and to test if the inflammatory process affects the functional properties of MSC. MSC(EAE) were found to retain their mesodermal features (as evidenced by the expression of surface cell markers and their ability to differentiate toward cells of the mesodermal lineage). Moreover, MSC(EAE) were able to support neurite outgrowth in the N2A cell line and to suppress the proliferation of lymphocytes induced by the mitogen phytohaemagglutinin (PHA). Intravenous administration of MSC(EAE) suppressed the clinical course of EAE (0% mortality, disease score 1.09±0.22 vs. 40% mortality and 2.95±0.31 EAE score in saline-treated controls), paralleled by a strong reduction of CNS inflammation and demyelination (9.7±2.79 perivascular cuffs in the treated mice, as compared to 25.8±7.4 in the controls; demyelination area: 1.73±0.3 in MSC(EAE)-treated animals vs. 3.8±0.26 in the controls) and by a significant protection of the axons (axonal density: 1.26±0.24 in the MSC(EAE)-treated animals vs. 3.06±0.38 in the control group). All these beneficial effects were indistinguishable from the effects induced by MSC obtained from healthy syngeneic donors. These data demonstrate that the inflammatory process in EAE does not exert any deleterious effect on the functional/biological properties of the MSC and provide additional support for the use of autologous MSC that are obtained from MS-patients, in future clinical applications.

Characterization of human sporadic ALS biomarkers in the familial ALS transgenic mSOD1(G93A) mouse model.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of motor neurons. Although most cases of ALS are sporadic (sALS) and of unknown etiology, there are also inherited familial ALS (fALS) cases that share a phenotype similar to sALS pathological and clinical phenotype. In this study, we have identified two new potential genetic ALS biomarkers in human bone marrow mesenchymal stem cells (hMSC) obtained from sALS patients, namely the TDP-43 (TAR DNA-binding protein 43) and SLPI (secretory leukocyte protease inhibitor). Together with the previously discovered ones-CyFIP2 and RbBP9, we investigated whether these four potential ALS biomarkers may be differentially expressed in tissues obtained from mutant SOD1(G93A) transgenic mice, a model that is relevant for at least 20% of the fALS cases. Quantitative real-time PCR analysis of brain, spinal cord and muscle tissues of the mSOD1(G93A) and controls at various time points during the progression of the neurological disease showed differential expression of the four identified biomarkers in correlation with (i) the tissue type, (ii) the stage of the disease and (iii) the gender of the animals, creating thus a novel spatiotemporal molecular signature of ALS. The biomarkers detected in the fALS animal model were homologous to those that were identified in hMSC of our sALS cases. These results support the possibility of a molecular link between sALS and fALS and may indicate common pathogenetic mechanisms involved in both types of ALS. Moreover, these results may pave the path for using the mSOD1(G93A) mouse model and these biomarkers as molecular beacons to evaluate the effects of novel drugs/treatments in ALS.

Repeated immunization of mice with phosphorylated-tau peptides causes neuroinflammation.

The recent studies of others and of us showing robust efficacy of anti-tangle immunotherapy, directed against phosphorylated (phos)-tau protein, may pave the way to clinical trials of phos-tau immunotherapy in Alzheimer's-disease and other tauopathies. At this stage addressing the safety of the phos-tau-immunotherapy is highly needed, particularly since we have previously shown the neurotoxic potential of tau-immunotherapy, specifically of full-length unphosphorylated-tau vaccine under a CNS-proinflammatory milieu [induced by emulsification in complete-Freund's-adjuvant (CFA) and pertussis-toxin (PT)] in young wild-type (WT)-mice. The aim of our current study was to address safety aspects of the phos-tau-immunotherapy in both neurofibrillary-tangle (NFT)-mice as well as in WT-mice, under challenging conditions of repeated immunizations with phos-tau peptides under a CNS-proinflammatory milieu. NFT- and WT-mice were repeatedly immunized (7 injections in adult-, 4 in aged-mice) with phos-tau peptides emulsified in CFA-PT. A paralytic disease was evident in the phos-tau-immunized adult NFT-mice, developing progressively to 26.7% with the number of injections. Interestingly, the WT-mice were even more prone to develop neuroinflammation following phos-tau immunization, affecting 75% of the immunized mice. Aged mice were less prone to neuroinflammatory manifestations. Anti-phos-tau antibodies, detected in the serum of immunized mice, partially correlated with the neuroinflammation in WT-mice. This points that repeated phos-tau immunizations in the frame of a proinflammatory milieu may be encephalitogenic to tangle-mice, and more robustly to WT-mice, indicating that - under certain conditions - the safety of phos-tau immunotherapy is questionable.

Hematopoietic stem cell transplantation in multiple sclerosis.

It is widely accepted that the main common pathogenetic pathway in multiple sclerosis (MS) involves an immune-mediated cascade initiated in the peripheral immune system and targeting CNS myelin. Logically, therefore, therapeutic approaches to the disease include modalities aiming at downregulation of the various immune elements that are involved in this immunological cascade. Since the introduction of interferons in 1993, more specific immunoactive drugs have been introduced, but still most of them can, at best, effectively modulate only the early relapsing phases of MS. The more progressed phases of the disease are not efficiently amendable by the existing immunomodulatory drugs. Moreover, localized and compartmentized inflammation in the CNS, which seems to be mostly responsible for the chronic axonal damage and resulting progression of disability, is less affected by the current drugs. A more radical approach to suppress all the inflammation in MS, including that into the CNS, could theoretically be achieved with high-dose immunosuppression using strong cytotoxic medications and resetting of the immune system by hematopoietic stem cell transplantation (HSCT). HSCT, both allogeneic and autologous, has been tried as a novel therapeutic approach in various autoimmune diseases. During the last 15 years several (mostly open) clinical studies evaluated the effect of HSTC on MS patients; the published papers showed that a high proportion of the HSCT-treated MS patients were stabilized, or even improved after the transplantation and have generally indicated a beneficial effect on disease progression. In this review, the rationale of HSCT and the summary of the results of the existing clinical trials are presented. Despite the fact that it is difficult to collectively summarize the results of all the trials, due to lack of uniformity in the conditioning and treatment protocols and of completed controlled studies, these clinical studies have provided a strong 'proof of concept' for HSCT in MS and have significantly contributed to our understanding of the advantages and disadvantages of each approach and HSCT protocol.

Clinical experience with stem cells and other cell therapies in neurological diseases.

To overcome the limited capacity of the CNS for regeneration, the theoretical alternative would be to use stem cells for more effective management of chronic degenerative and inflammatory neurological conditions, and also of acute neuronal damage from injuries or cerebrovascular diseases. Although the adult brain contains small numbers of stem cells in restricted areas, this intrinsic stem cell repertoire is small and does not measurably contribute to functional recovery. Embryonic cells carrying pluripotent and self-renewal properties represent the stem cell prototype, but there are additional somatic stem cells that may be harvested and expanded from various tissues during adult life. Stem cell transplantation is based on the assumption that such cells may have the potential to regenerate or support the survival of the existing, partially damaged cells. This review summarizes the state-of-the-art and the clinical worldwide experience with the use of various types of stem cells in neurological diseases.