Intrathecal Administration of Autologous CD34 Positive Cells in Patients with Past Cerebral Infarction: A Safety Study

The Role of Stem Cells as Therapeutics for Ischaemic Stroke

Stroke remains one of the leading causes of death and disability worldwide. Current reperfusion treatments for ischaemic stroke are limited due to their narrow therapeutic window in rescuing ischaemic penumbra. Stem cell therapy offers a promising alternative. As a regenerative medicine, stem cells offer a wider range of treatment strategies, including long-term intervention for chronic patients, through the reparation and replacement of injured cells via mechanisms of differentiation and proliferation. The purpose of this review is to evaluate the therapeutic role of stem cells for ischaemic stroke. This paper discusses the pathology during acute, subacute, and chronic phases of cerebral ischaemic injury, highlights the mechanisms involved in mesenchymal, endothelial, haematopoietic, and neural stem cell-mediated cerebrovascular regeneration, and evaluates the pre-clinical and clinical data concerning the safety and efficacy of stem cell-based treatments. The treatment of stroke patients with different types of stem cells appears to be safe and efficacious even at relatively higher concentrations irrespective of the route and timing of administration. The priming or pre-conditioning of cells prior to administration appears to help augment their therapeutic impact. However, larger patient cohorts and later-phase trials are required to consolidate these findings.

Editing a gateway for cell therapy across the blood-brain barrier

Stem cell therapy has been shown to improve stroke outcomes in animal models and is currently advancing towards clinical practice. However, uncertainty remains regarding the optimal route for cell delivery to the injured brain. Local intracerebral injections are effective in precisely delivering cells into the stroke cavity but carry the risk of damaging adjacent healthy tissue. Systemic endovascular injections, meanwhile, are minimally invasive, but most injected cells do not cross CNS barriers and become mechanically trapped in peripheral organs. Although the blood-brain barrier and the blood-CSF barrier tightly limit the entrance of cells and molecules into the brain parenchyma, immune cells can cross these barriers especially under pathological conditions, such as stroke. Deciphering the cell surface signature and the molecular mechanisms underlying this pathophysiological process holds promise for improving the targeted delivery of systemic injected cells to the injured brain. In this review, we describe experimental approaches that have already been developed in which (i) cells are either engineered to express cell surface proteins mimicking infiltrating immune cells; or (ii) cell grafts are preconditioned with hypoxia or incubated with pharmacological agents or cytokines. Modified cell grafts can be complemented with strategies to temporarily increase the permeability of the blood-brain barrier. Although these approaches could significantly enhance homing of stem cells into the injured brain, cell entrapment in off-target organs remains a non-negligible risk. Recent developments in safety-switch systems, which enable the precise elimination of transplanted cells on the administration of a drug, represent a promising strategy for selectively removing stem cells stuck in untargeted organs. In sum, the techniques described in this review hold great potential to substantially improve efficacy and safety of future cell therapies in stroke and may be relevant to other brain diseases.

Potential Mechanisms and Perspectives in Ischemic Stroke Treatment Using Stem Cell Therapies

Ischemic stroke (IS) remains one of the major causes of death and disability due to the limited ability of central nervous system cells to regenerate and differentiate. Although several advances have been made in stroke therapies in the last decades, there are only a few approaches available to improve IS outcome. In the acute phase of IS, mechanical thrombectomy and the administration of tissue plasminogen activator have been widely used, while aspirin or clopidogrel represents the main therapy used in the subacute or chronic phase. However, in most cases, stroke patients fail to achieve satisfactory functional recovery under the treatments mentioned above. Recently, cell therapy, especially stem cell therapy, has been considered as a novel and potential therapeutic strategy to improve stroke outcome through mechanisms, including cell differentiation, cell replacement, immunomodulation, neural circuit reconstruction, and protective factor release. Different stem cell types, such as mesenchymal stem cells, marrow mononuclear cells, and neural stem cells, have also been considered for stroke therapy. In recent years, many clinical and preclinical studies on cell therapy have been carried out, and numerous results have shown that cell therapy has bright prospects in the treatment of stroke. However, some cell therapy issues are not yet fully understood, such as its optimal parameters including cell type choice, cell doses, and injection routes; therefore, a closer relationship between basic and clinical research is needed. In this review, the role of cell therapy in stroke treatment and its mechanisms was summarized, as well as the function of different stem cell types in stroke treatment and the clinical trials using stem cell therapy to cure stroke, to reveal future insights on stroke-related cell therapy, and to guide further studies.

Clinical Trials of Stem Cell Therapy for Cerebral Ischemic Stroke

Despite recent developments in innovative treatment strategies, stroke remains one of the leading causes of death and disability worldwide. Stem cell therapy is currently attracting much attention due to its potential for exerting significant therapeutic effects on stroke patients. Various types of cells, including bone marrow mononuclear cells, bone marrow/adipose-derived stem/stromal cells, umbilical cord blood cells, neural stem cells, and olfactory ensheathing cells have enhanced neurological outcomes in animal stroke models. These stem cells have also been tested via clinical trials involving stroke patients. In this article, the authors review potential molecular mechanisms underlying neural recovery associated with stem cell treatment, as well as recent advances in stem cell therapy, with particular reference to clinical trials and future prospects for such therapy in treating stroke.

Clinical neurorestorative cell therapies: Developmental process, current state and future prospective

Clinical cell therapies (CTs) for neurological diseases and cellular damage have been explored for more than 2 decades. According to the United States Food and Drug Administration, there are 2 types of cell categories for therapy, namely stem cell-derived CT products and mature/functionally differentiated cell-derived CT products. However, regardless of the type of CT used, the majority of reports of clinical CTs from either small sample sizes based on single-center phase 1 or 2 unblinded trials or retrospective clinical studies showed effects on neurological improvement and the ability to either partially or temporarily thwart the deteriorating cellular processes of the neurodegenerative diseases. There have been only a few prospective, multicenter, randomized, double- blind placebo-control clinical trials of CTs so far in this developing novel area that have shown negative results, and more clinical trials are needed. This will expand our knowledge in exploring the type of cells that yield promising results and restore damaged neurological structure and functions of the central nervous system based on higher level evidence-based medical data. In this review, we briefly introduce the developmental process, current state, and future prospective for clinical neurorestorative CT.

Clinical diagnostic and therapeutic guidelines of stroke neurorestoration (2020 China version)

Stroke is the main cause of death and disability among Chinese, and neurorestoration is an effective therapeutic strategy for patients with stroke. In recent years, many achievements have been made in stroke neurorestoration, but viewpoints for managing stroke vary per discipline. In order to promote standardization of diagnosis and treatment for stroke neurorestoration, the Chinese Association of Neurorestoratology (CANR; Preparatory) and China Committee of International Association of Neurorestoratology (IANR-China Committee) organized professional experts in the field to integrate fragmented neurorestorative methods and establish clinical diagnostic and therapeutic guidelines for stroke neurorestoration. This guideline includes the diagnosis and staging of stroke and therapeutic recommendations for neurorestoration at different stages of stroke in order to improve survival and quality of life of stroke patients.

Stem cell transplantation for ischemic stroke

BACKGROUND

Stroke is a leading cause of morbidity and mortality worldwide, with very large healthcare and social costs, and a strong demand for alternative therapeutic approaches. Preclinical studies have shown that stem cells transplanted into the brain can lead to functional improvement. However, to date, evidence for the benefits of stem cell transplantation in people with ischemic stroke is lacking. This is the first update of the Cochrane review published in 2010.

OBJECTIVES

To assess the efficacy and safety of stem cell transplantation compared with control in people with ischemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched August 2018), CENTRAL (last searched August 2018), MEDLINE (1966 to August 2018), Embase (1980 to August 2018), and BIOSIS (1926 to August 2018). We handsearched potentially relevant conference proceedings, screened reference lists, and searched ongoing trials and research registers (last searched August 2018). We also contacted individuals active in the field and stem cell manufacturers (last contacted August 2018).

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that recruited people with ischemic stroke, in any phase of the disease (acute, subacute or chronic), and an ischemic lesion confirmed by computerized tomography or magnetic resonance imaging scan. We included all types of stem cell transplantation, regardless of cell source (autograft, allograft, or xenograft; embryonic, fetal, or adult; from brain or other tissues), route of cell administration (systemic or local), and dosage. The primary outcome was efficacy (assessed as neurologic impairment or functional outcome) at longer term follow-up (minimum six months). Secondary outcomes included post-procedure safety outcomes (death, worsening of neurological deficit, infections, and neoplastic transformation).

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria, assessed trial quality and risk of bias, and extracted data. If needed, we contacted study authors for additional information. We performed random effects meta-analyses when two or more RCTs were available for any outcome. We assessed the certainty of the evidence by using the GRADE approach.

MAIN RESULTS

In this updated review, we included seven completed RCTs with 401 participants. All tested adult human non-neural stem cells; cells were transplanted during the acute, subacute, or chronic phase of ischemic stroke; administered intravenously, intra-arterially, intracerebrally, or into the lumbar subarachnoid space. Follow-up ranged from six months to seven years. Efficacy outcomes were measured with the National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), or Barthel Index (BI). Safety outcomes included case fatality, and were measured at the end of the trial.Overall, stem cell transplantation was associated with a better clinical outcome when measured with the NIHSS (mean difference [MD] -1.49, 95% confidence interval [CI] -2.65 to -0.33; five studies, 319 participants; low-certainty evidence), but not with the mRS (MD -0.42, 95% CI -0.86 to 0.02; six studies, 371 participants; very low-certainty evidence), or the BI (MD 14.09, 95% CI -1.94 to 30.13; three studies, 170 participants; very low-certainty evidence). The studies in favor of stem cell transplantation had, on average, a higher risk of bias, and a sample size of 32 or fewer participants.No significant safety concerns associated with stem cell transplantation were raised with respect to death (risk ratio [RR] 0.66, 95% CI 0.39 to 1.14; six studies, participants; low-certainty evidence).We were not able to perform the sensitivity analysis according to the quality of studies, because all of them were at high risk of bias.

AUTHORS' CONCLUSIONS

Overall, in participants with ischemic stroke, stem cell transplantation was associated with a reduced neurological impairment, but not with a better functional outcome. No obvious safety concerns were raised. However, these conclusions came mostly from small RCTs with high risk of bias, and the certainty of the evidence ranged from low to very low. More well-designed trials are needed.

Promoting Brain Repair and Regeneration After Stroke: a Plea for Cell-Based Therapies

PURPOSE OF REVIEW

After decades of hype, cell-based therapies are emerging into the clinical arena for the purposes of promoting recovery after stroke. In this review, we discuss the most recent science behind the role of cell-based therapies in ischemic stroke and the efforts to translate these therapies into human clinical trials.

RECENT FINDINGS

Preclinical data support numerous beneficial effects of cell-based therapies in both small and large animal models of ischemic stroke. These benefits are driven by multifaceted mechanisms promoting brain repair through immunomodulation, trophic support, circuit reorganization, and cell replacement. Cell-based therapies offer tremendous potential for improving outcomes after stroke through multimodal support of brain repair. Based on recent clinical trials, cell-based therapies appear both feasible and safe in all phases of stroke. Ongoing translational research and clinical trials will further refine these therapies and have the potential to transform the approach to stroke recovery and rehabilitation.

The spleen may be an important target of stem cell therapy for stroke

Stroke is the most common cerebrovascular disease, the second leading cause of death behind heart disease and is a major cause of long-term disability worldwide. Currently, systemic immunomodulatory therapy based on intravenous cells is attracting attention. The immune response to acute stroke is a major factor in cerebral ischaemia (CI) pathobiology and outcomes. Over the past decade, the significant contribution of the spleen to ischaemic stroke has gained considerable attention in stroke research. The changes in the spleen after stroke are mainly reflected in morphology, immune cells and cytokines, and these changes are closely related to the stroke outcomes. Autonomic nervous system (ANS) activation, release of central nervous system (CNS) antigens and chemokine/chemokine receptor interactions have been documented to be essential for efficient brain-spleen cross-talk after stroke. In various experimental models, human umbilical cord blood cells (hUCBs), haematopoietic stem cells (HSCs), bone marrow stem cells (BMSCs), human amnion epithelial cells (hAECs), neural stem cells (NSCs) and multipotent adult progenitor cells (MAPCs) have been shown to reduce the neurological damage caused by stroke. The different effects of these cell types on the interleukin (IL)-10, interferon (IFN), and cholinergic anti-inflammatory pathways in the spleen after stroke may promote the development of new cell therapy targets and strategies. The spleen will become a potential target of various stem cell therapies for stroke represented by MAPC treatment.

[Cell therapy for ischemic stroke. Results of clinical trials and perspectives of clinical application in the Russian Federation]

The first part of the review summarized the results of preclinical animal studies using stroke models that demonstrated the efficacy of cell therapy. The second part presents the proposed mechanisms of action of stem cells, optimal therapeutic window for cell transplantation, the results of completed clinical trials on humans in the period from 2010 to 2017, as well as the legal aspects of the use of cell technologies in the Russian Federation.

Neurorestorative effect of olfactory ensheathing cells and Schwann cells by intranasal delivery for patients with ischemic stroke: design of a multicenter randomized double-blinded placebo-controlled clinical study

Introduction:

There have been many clinical studies or trials for patients with ischemic stroke by cell therapy, which includes olfactory ensheathing cell (OEC), mononuclear cell, mesenchymal stromal cell, fetal neural cell or products of varying stem cells, etc. Those cells through different transplanting ways have showed moderate neurorestorative effect in patients with ischemic stroke, but majority were not multicenter randomized, double-blinded, placebo-controlled studies or trials. OEC transplantation has shown a more effective to restore neurological damage in central nervous system (CNS). We hypothesize that OEC through intra-olfactory mucosa transplantation can migrate into the ischemic stroke area around and restore neurological deficit caused from this disaster.

Objective of the study:

This is a multicenter, randomized, double-blinded, placebo- controlled 12 month clinical study of OECs and Schwann cells (SCs) for patients with sub-acute ischemic stroke and chronic ischemic stroke, to test which kind of cell has more neurorestorative effect for patients with ischemic stroke relative to placebo.

Design of the study:

This study is involved two groups of patients with sub-acute ischemic stroke and chronic ischemic stroke. Each group enrolls 30 patients. The experimental intervention consists in using OECs and SCs through intra-olfactory mucosa transplantation in participating patients. This will be compared with using placebo (injecting cell culture medium). Participating patients in groups of sub-acute ischemic stroke and chronic ischemic stroke are randomized in natural order to divide into A, B, or C groups and get one of experimental treatment procedures. Patients, operating physicians, and assessing physicians are left unaware of what cells or medium will be injected to participating patients. All patients will be assessed before treatment and after one month, three months, six months, and one year.

Ethics and dissemination:

The clinical study protocol and consent form were approved by Chinese Association of Neurorestoratology and the ethics committees of the hospitals which joined this clinical study. Findings will be published in peer-reviewed journals.

Bone marrow mononuclear cell therapy in ischaemic stroke: a systematic review

Bone marrow mononuclear cell (BM-MNC) therapy has emerged as a potential therapy for the treatment of stroke. We performed a systematic review of published studies using BM-MNC therapy in patients with ischaemic stroke (IS). Literature was searched using MEDLINE, PubMed, EMBASE, Trip Database, Cochrane library and clinicaltrial.gov to identify studies on BM-MNC therapy in IS till June, 2016. Data were extracted independently by two reviewers. STATA version 13 was used for carrying out meta-analysis. We included non-randomized open-label, single-arm and non-randomized comparative studies or randomized controlled trials (RCTs) if BM-MNCs were used to treat patients with IS in any phase after the index stroke. One randomized trial, two non-randomized comparative trials and four single-arm open-label trials (total seven studies) involving 227 subjects (137 patients and 90 controls) were included in the systematic review and meta-analysis. The pooled proportion for favourable clinical outcome (modified Rankin Scale score ≤2) in six studies involving 122 subjects was 29% (95% CI 0.16-0.43) who were exposed to BM-MNCs and pooled proportion for favourable clinical outcome of 69 subjects (taken from two trials) who did not receive BM-MNCs was 20% (95% CI 0.12-0.32). The pooled difference in the safety outcomes was not significant between both the groups. Our systematic review suggests that BM-MNC therapy is safe up to 1 year post-intervention and is feasible; however, its efficacy in the case of IS patients is debatable. Well-designed randomized controlled trials are required to provide more information on the efficacy of BM-MNC transplantation in patients with IS.

Safety and Therapeutic Potential of M2 Macrophages in Stroke Treatment

Our objective was to evaluate the safety and clinical efficacy of autologous M2 macrophage transplantation in nonacute stroke patients. We also evaluated whether the intrathecal administration of macrophages influences the production of cytokines by peripheral blood cells and whether the levels of cytokines correlate with stroke severity and responsiveness to cell therapy. In this study, 13 patients (12 males and 1 female with a median age of 63 years) diagnosed with ischemic (n = 10) or hemorrhagic (n = 3) stroke were subjected to cell transplantation therapy (study group). On average, 21.9 × 10(6) autologous M2 macrophages were injected intrathecally. Thirteen matched case-control stroke patients who did not receive cell therapy comprised the control group. We did not observe any serious adverse events (i.e., intrahospital mortality, neurological worsening, and seizures) related to the cell injection. One patient in the study group and two patients in the control group died during the 6-month follow-up period due to recurrent stroke. In the study group, the NIHSS score decreased from 11 to 6 (p = 0.007) in 6 months after the therapy, whereas the patients in the control group showed a less pronounced neurological improvement (the NIHSS score decreased from 11 to 8, p = 0.07). The obvious positive response (the improvement of the NIHSS score ≥3) in the study group was observed in 75% versus 18% in the control group (pFET = 0.03). M2 cell introduction did not significantly affect the production of various cytokines. Nevertheless, pretreated levels of IL-8, IL-10, and IL-4 correlated with stroke severity. Moreover, responder patients had lower spontaneous production of IL-10, FGF-β, PDGF, VEGF, and higher stimulation indexes of IL-1β, TNF-α, IFN-γ, and IL-6 than nonresponders. These findings suggest that the intrathecal administration of autologous M2 cells in stroke patients is safe and leads to a better neurological recovery, which could be mediated through the immunomodulatory activity of M2 macrophages.

The Dark Side of the Force - Constraints and Complications of Cell Therapies for Stroke

Cell therapies are increasingly recognized as a promising option to augment the limited therapeutic arsenal available to fight ischemic stroke. During the last two decades, cumulating preclinical evidence has indicated a substantial efficacy for most cell treatment paradigms and first clinical trials are currently underway to assess safety and feasibility in patients. However, the strong and still unmet demand for novel stroke treatment options and exciting findings reported from experimental studies may have drawn our attention away from potential side effects related to cell therapies and the ways by which they are commonly applied. This review summarizes common and less frequent adverse events that have been discovered in preclinical and clinical investigations assessing cell therapies for stroke. Such adverse events range from immunological and neoplastic complications over seizures to cell clotting and cell-induced embolism. It also describes potential complications of clinically applicable administration procedures, detrimental interactions between therapeutic cells, and the pathophysiological environment that they are placed into, as well as problems related to cell manufacturing. Virtually each therapeutic intervention comes at a certain risk for complications. Side effects do therefore not generally compromise the value of cell treatments for stroke, but underestimating such complications might severely limit therapeutic safety and efficacy of cell treatment protocols currently under development. On the other hand, a better understanding will provide opportunities to further improve existing therapeutic strategies and might help to define those circumstances, under which an optimal effect can be realized. Hence, the review eventually discusses strategies and recommendations allowing us to prevent or at least balance potential complications in order to ensure the maximum therapeutic benefit at minimum risk for stroke patients.

Efficacy and safety of stem cell therapies for patients with stroke: a systematic review and single arm meta-analysis

BACKGROUND AND OBJECTIVES

Stem cell-based therapy is a potential new approach in the treatment of stroke. However, the efficacy and safety of these treatments are not yet fully understood. Therefore, we performed a meta-analysis of available single-arm studies using stem cell-based therapy in patients with stroke.

METHODS

We searched MEDLINE, EMBASE, and the Cochrane database for studies of stem cell therapy in patients with stroke from its inception through July 2014. The articles included in the search were restricted to the English language, studies with at least 5 patients, and those using cell-based therapies for treating stroke.

RESULTS

Fourteen studies included in the meta-analysis. The pooled mean difference in National Institutes of Health Stroke Scale (NIHSS) scores from baseline to follow-up points was 5.7 points (95%CI: -8.2 to -3.2, I(2) =91.5%) decreased. Also the pooled mean difference in modified Bathel index (BI) score was increased by 31.5 points (95%CI: 35.6∼14.9, I(2) =52.7%) and the pooled incidence rate to achieve on modified Rankin score (mRS)≤2 was 40% (95% CI: 30%∼51%, I(2) =35.4%) at follow-up points. The pooled incidence rates of death, seizure, and infection were 13% (95%CI, 8∼23%), 15% (95%CI, 8∼25%), and 15% (95%CI, 8∼23%), respectively.

CONCLUSIONS

The published data suggest that stem cell-based therapy for patients with stroke can be judged as effective based on single arm clinical studies. However, clinical benefits of stem cell therapy for patients with stroke need further investigation and reevaluation to test the clinical efficacy.

Diffuse axonal injury after traumatic cerebral microbleeds: an evaluation of imaging techniques

Previous neuropathological studies regarding traumatic brain injury have primarily focused on changes in large structures, for example, the clinical prognosis after cerebral contusion, intracerebral hematoma, and epidural and subdural hematoma. In fact, many smaller injuries can also lead to severe neurological disorders. For example, cerebral microbleeds result in the dysfunction of adjacent neurons and the disassociation between cortex and subcortical structures. These tiny changes cannot be adequately visualized on CT or conventional MRI. In contrast, gradient echo sequence-based susceptibility-weighted imaging is very sensitive to blood metabolites and microbleeds, and can be used to evaluate traumatic cerebral microbleeds with high sensitivity and accuracy. Cerebral microbleed can be considered as an important imaging marker for diffuse axonal injury with potential relevance for prognosis. For this reason, based on experimental and clinical studies, this study reviews the role of imaging data showing traumatic cerebral microbleeds in the evaluation of cerebral neuronal injury and neurofunctional loss.