Intravenous Bone Marrow Mononuclear Cells for Acute Ischemic Stroke: Safety, Feasibility, and Effect Size from a Phase I Clinical Trial

Efficacy and safety of mesenchymal stem cell therapies for ischemic stroke: a systematic review and meta-analysis

BACKGROUND

The efficacy and safety of mesenchymal stem cells (MSCs) in the treatment of ischemic stroke (IS) remains controversial. Therefore, this study aimed to evaluate the efficacy and safety of MSCs for IS.

METHODS

A literature search until May 23, 2023, was conducted using PubMed, EMBASE, the Cochrane Library, and the Web of Science to identify studies on stem cell therapy for IS. Interventional and observational clinical studies of MSCs in patients with IS were included, and the safety and efficacy were assessed. Two reviewers extracted data and assessed the quality independently. The meta-analysis was performed using RevMan5.4.

RESULTS

Fifteen randomized controlled trials (RCTs) and 15 non-randomized trials, including 1217 patients (624 and 593 in the intervention and control arms, respectively), were analyzed. MSCs significantly improved patients' activities of daily living according to the modified Rankin scale (mean difference [MD]: -0.26; 95% confidence interval [CI]: -0.50 to -0.01; P = .04) and National Institutes of Health Stroke Scale score (MD: -1.69; 95% CI: -2.66 to -0.73; P < .001) in RCTs. MSC treatment was associated with lower mortality rates in RCTs (risk ratio: 0.44; 95% CI: 0.28-0.69; P < .001). Fever and headache were among the most reported adverse effects.

CONCLUSIONS

Based on our review, MSC transplantation improves neurological deficits and daily activities in patients with IS. In the future, prospective studies with large sample sizes are needed for stem cell studies in ischemic stroke. This meta-analysis has been registered at PROSPERO with CRD42022347156.

Cell Therapy and Functional Recovery of Stroke

Stroke is the most common cause of disability. Brain repair mechanisms are often insufficient to allow a full recovery. Stroke damage involve all brain cell type and extracellular matrix which represent the crucial "glio-neurovascular niche" useful for brain plasticity. Regenerative medicine including cell therapies hold great promise to decrease post-stroke disability of many patients, by promoting both neuroprotection and neural repair through direct effects on brain lesion and/or systemic effects such as immunomodulation. Mechanisms of action vary according to each grafted cell type: "peripheral" stem cells, such as mesenchymal stem cells (MSC), can provide paracrine trophic support, and neural stem/progenitor cells (NSC) or neurons can act as direct cells' replacements. Optimal time window, route, and doses are still debated, and may depend on the chosen medicinal product and its expected mechanism such as neuroprotection, delayed brain repair, systemic effects, or graft survival and integration in host network. MSC, mononuclear cells (MNC), umbilical cord stem cells and NSC are the most investigated. Innovative approaches are implemented concerning combinatorial approaches with growth factors and biomaterials such as injectable hydrogels which could protect a cell graft and/or deliver drugs into the post-stroke cavity at chronic stages. Through main publications of the last two decades, we provide in this review concepts and suggestions to improve future translational researches and larger clinical trials of cell therapy in stroke.

Revolutionizing Stroke Recovery: Unveiling the Promise of Stem Cell Therapy

Stem cells, renowned for their unique regenerative capabilities, present significant hope in treating stroke, a major cause of disability globally. This review offers a detailed analysis of stem cell applications in stroke (ischemic and hemorrhagic) recovery. It examines therapies based on autologous (patient-derived), allogeneic (donor-derived), and Granulocyte-Colony Stimulating Factor (G-CSF) based stem cells, focusing on cell types such as Mesenchymal Stem/Stromal Cells (MSCs), Bone Marrow Mononuclear Stem Cells (BMMSCs), and Neural Stem/Progenitor Cells (NSCs). The paper compiles clinical trial data to evaluate their effectiveness and safety and addresses the ethical concerns of these innovative treatments. By explaining the mechanisms of stem cell-induced neurological repair, this review underscores stem cells' potential in revolutionizing stroke rehabilitation and suggests avenues for future research.

Safety and Efficacy of Bone Marrow and Adipose Tissue-Derived Mesenchymal Stem Cells for the Treatment of Ischemic Stroke: A Systematic Review

Neurological diseases, including ischemic stroke, are considered a big challenge for public health due to their high prevalence and lack of definitive and effective treatments. Addressing these issues requires innovative therapeutic approaches and among the limited methods available, stem cells have shown promise in improving central nervous system repair by enhancing myelin regeneration and neuronal recovery. To advance this field of research, this systematic review aims to assess the safety and effectiveness of mesenchymal stem cells (MSCs) derived from both bone marrow and adipose tissue for the treatment of ischemic stroke. This study conducted a systematic review in the electronic databases PubMed, Scopus, Web of Science, Embase, ScienceDirect, and Google Scholar to assess the efficacy and safety of MSCs generated from bone marrow and adipose tissue for the treatment of ischemic stroke. It was extracted without a time limit until April 2023. The studies were then transferred to the information management program (EndNote) and duplicates were eliminated. The remaining studies were then examined using the entry and exit criteria and the 3 stages of primary, secondary, and qualitative evaluation, and finally, the results of the final studies were extracted. According to the initial search in the desired databases, 1028 possible related articles were identified and transferred to the information management software (EndNote). After removing 390 duplicate studies, 608 studies were excluded based on inclusion and exclusion criteria. Finally, 37 final studies were included in the systematic review process. Based on the investigations, it was evident that the administration of MSCs derived from both bone marrow and adipose tissue holds significant promise as an effective and safe treatment approach for ischemic stroke. The results consistently showed acceptable outcomes in the studies and this evidence can be recommended for the clinical application of this treatment. Also, the findings of this study report that the use of adipose tissue and bone marrow MSCs in the treatment of ischemic stroke can be used as a practical method.

Mesenchymal Stem Cell-Induced Neuroprotection in Pediatric Neurological Diseases: Recent Update of Underlying Mechanisms and Clinical Utility

Pediatric neurological diseases refer to a group of disorders that affect the nervous system in children. These conditions can have a significant impact on a child's development, cognitive function, motor skills, and overall quality of life. Stem cell therapy is a new and innovative approach to treat various neurological conditions by repairing damaged neurons and replacing those that have been lost. Mesenchymal stem cells (MSCs) have gained significant recognition in this regard due to their ability to differentiate into different cell types. MSCs are multipotent self-replicating stem cells known to render promising results in the treatment of stroke and spinal cord injury in adults. When delivered to the foci of damage in the central nervous system, stem cells begin to differentiate into neural cells under the stimulation of paracrine factors and secrete various neurotrophic factors (NTFs) like nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) that expedite the repair process in injured neurons. In the present review, we will focus on the therapeutic benefits of the MSC-based therapies in salient pediatric neurological disorders including cerebral palsy, stroke, and autism.

A review and meta-analysis of stem cell therapies in stroke patients: effectiveness and safety evaluation

PURPOSE

Stem cells have been extensively used during the last decade to improve clinical outcomes after stroke. The dramatic increase in trials in this field has led us to perform a systematic review and meta-analysis to understand the safety, effectiveness, and relative limitations of this type of intervention.

METHOD

This review summarizes the current evidence pooled from PubMed (Medline), EMBASE, EBSCOhost, http://clinicaltrials.gov , Scopus (Elsevier), Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science (Science Citation Index Expanded) databases for the use of stem cell therapies in stroke patients without combinations with other treatment modalities. The National Institutes of Health Stroke, modified Rankin Scales, and Barthel Index scores after external stem cell administration have been evaluated on the 3rd, 6th, and 12th months after treatment. The random effect analysis was performed using the Review Manager 5.4.1. The characteristics of stem cell sources and their adverse effects have been discussed as well.

FINDINGS

Although reasonably safe, the effectiveness evidence fluctuated to a large extent due to the heterogeneity of the clinical trials and the absence of a systematic approach. The stem cell sources and the administration window were not strongly associated with clinical outcomes.

CONCLUSION

Further studies should be conducted to understand the deep discrepancy between preclinical and clinical trials and to execute phase 3 clinical trials with robust control of study characteristics and outcomes.

Stem cell-based interventions for the treatment of stroke in newborn infants

BACKGROUND

Perinatal stroke refers to a diverse but specific group of cerebrovascular diseases that occur between 20 weeks of fetal life and 28 days of postnatal life. Acute treatment options for perinatal stroke are limited supportive care, such as controlling hypoglycemia and seizures. Stem cell-based therapies offer a potential therapeutic approach to repair, restore, or regenerate injured brain tissue. Preclinical findings have culminated in ongoing human neonatal studies.

OBJECTIVES

To evaluate the benefits and harms of stem cell-based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem-cell based interventions of a different type or source.

SEARCH METHODS

We searched CENTRAL, PubMed, Embase, and three trials registries in February 2023. We planned to search the reference lists of included studies and relevant systematic reviews for studies not identified by the database searches.

SELECTION CRITERIA

We attempted to include randomized controlled trials, quasi-randomized controlled trials, and cluster trials that evaluated any of the following comparisons. • Stem cell-based interventions (any type) versus control (placebo or no treatment) • Mesenchymal stem/stromal cells (MSCs) of a specifictype (e.g. number of doses or passages) or source (e.g. autologous/allogeneic or bone marrow/cord) versus MSCs of another type or source • Stem cell-based interventions (other than MSCs) of a specific type (e.g. mononuclear cells, oligodendrocyte progenitor cells, neural stem cells, hematopoietic stem cells, or induced pluripotent stem cell-derived cells) or source (e.g. autologous/allogeneic or bone marrow/cord) versus stem cell-based interventions (other than MSCs) of another type or source • MSCs versus stem cell-based interventions other than MSCs We planned to include all types of transplantation regardless of cell source (bone marrow, cord blood, Wharton's jelly, placenta, adipose tissue, peripheral blood), type of graft (autologous or allogeneic), and dose.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all-cause neonatal mortality, major neurodevelopmental disability, and immune rejection or any serious adverse event. Our secondary outcomes included all-cause mortality prior to first hospital discharge, seizures, adverse effects, and death or major neurodevelopmental disability at 18 to 24 months of age. We planned to use GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We identified no completed or ongoing randomized trials that met our inclusion criteria. We excluded three studies: two were phase 1 trials, and one included newborn infants with conditions other than stroke (i.e. cerebral ischemia and anemia). Among the three excluded studies, we identified the first phase 1 trial on the use of stem cells for neonatal stroke. It reported that a single intranasal application of bone marrow-derived MSCs in term neonates with a diagnosis of perinatal arterial ischemic stroke (PAIS) was feasible and apparently not associated with severe adverse events. However, the trial included only 10 infants, and follow-up was limited to three months.

AUTHORS' CONCLUSIONS

No evidence is currently available to evaluate the benefits and harms of stem cell-based interventions for treatment of stroke in newborn infants. We identified no ongoing studies. Future clinical trials should focus on standardizing the timing and method of cell delivery and cell processing to optimize the therapeutic potential of stem cell-based interventions and safety profiles. Phase 1 and large animal studies might provide the groundwork for future randomized trials. Outcome measures should include all-cause mortality, major neurodevelopmental disability and immune rejection, and any other serious adverse events.

Bone Marrow-Derived Mononuclear Cells in the Treatment of Neurological Diseases: Knowns and Unknowns

Bone marrow-derived mononuclear cells (BMMNCs) have been used for decades in preclinical and clinical studies to treat various neurological diseases. However, there is still a knowledge gap in the understanding of the underlying mechanisms of BMMNCs in the treatment of neurological diseases. In addition, prerequisite factors for the efficacy of BMMNC administration, such as the optimal route, dose, and number of administrations, remain unclear. In this review, we discuss known and unknown aspects of BMMNCs, including the cell harvesting, administration route and dose; mechanisms of action; and their applications in neurological diseases, including stroke, cerebral palsy, spinal cord injury, traumatic brain injury, amyotrophic lateral sclerosis, autism spectrum disorder, and epilepsy. Furthermore, recommendations on indications for BMMNC administration and the advantages and limitations of BMMNC applications for neurological diseases are discussed. BMMNCs in the treatment of neurological diseases. BMMNCs have been applied in several neurological diseases. Proposed mechanisms for the action of BMMNCs include homing, differentiation and paracrine effects (angiogenesis, neuroprotection, and anti-inflammation). Further studies should be performed to determine the optimal cell dose and administration route, the roles of BMMNC subtypes, and the indications for the use of BMMNCs in neurological conditions with and without genetic abnormalities.

Comparison of the Administration Route of Stem Cell Therapy for Ischemic Stroke: A Systematic Review and Meta-Analysis of the Clinical Outcomes and Safety

Stem cell treatment is emerging as an appealing alternative for stroke patients, but there still needs to be an agreement on the protocols in place, including the route of administration. This systematic review aimed to assess the efficacy and safety of the administration routes of stem cell treatment for ischemic stroke. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A comprehensive literature search was undertaken using the PubMed, Scopus, and Cochrane databases. A total of 21 publications on stem cell therapy for ischemic stroke were included. Efficacy outcomes were measured using the National Institutes of Health Stroke Scale (NIHSS), the modified Rankin Scale (mRS), and the Barthel index (BI). Intracerebral administration showed a better outcome than other routes, but a greater number of adverse events followed due to its invasiveness. Adverse events were shown to be related to the natural history of stroke not to the treatment. However, further investigation is required, since studies have yet to compare the different administration methods directly.

Research progress in clinical trials of stem cell therapy for stroke and neurodegenerative diseases

The incidence of stroke and neurodegenerative diseases is gradually increasing in modern society, but there is still no treatment that is effective enough. Stem cells are cells that can reproduce (self-renew) and differentiate into the body, which have shown significance in basic research, while doctors have also taken them into clinical trials to determine their efficacy and safety. Existing clinical trials mainly include middle-aged and elderly patients with stroke or Parkinson's disease (mostly 40-80 years old), mainly involving injection of mesenchymal stem cells and bone marrow mesenchymal stem cells through the veins and the putamen, with a dosage of mostly 106-108 cells. The neural and motor functions of the patients were restored after stem cell therapy, and the safety was found to be good during the follow-up period of 3 months to 5 years. Here, we review all clinical trials and the latest advances in stroke, Alzheimer's disease, and Parkinson's disease, with the hope that stem cell therapy will be used in the clinic in the future to achieve effective treatment rates and benefit patients.

Stem cell‐based interventions for the treatment of stroke in newborn infants

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To evaluate the benefits and harms of stem cell‐based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem‐cell based interventions of a different type or source.

Mesenchymal stem cells for regenerative medicine in central nervous system

Mesenchymal stem cells (MSCs) are multipotent stem cells, whose paracrine and immunomodulatory potential has made them a promising candidate for central nervous system (CNS) regeneration. Numerous studies have demonstrated that MSCs can promote immunomodulation, anti-apoptosis, and axon re-extension, which restore functional neural circuits. The therapeutic effects of MSCs have consequently been evaluated for application in various CNS diseases including spinal cord injury, cerebral ischemia, and neurodegenerative disease. In this review, we will focus on the research works published in the field of mechanisms and therapeutic effects of MSCs in CNS regeneration.

Clinical outcome and safety of stem cell therapy for ischemic stroke: A systematic review and meta-analysis

Background

Several reports on stem cell administration have emerged proving it to be an ideal therapeutic approach for improving neurological functions in ischemic stroke patients. However, some studies also show disappointing results, with some reporting no statistically significant improvements among several different parameters. Several challenges also arise relating to safety and nonscientific aspects, such as ethics.

Methods

We performed a systematic review and meta-analysis to evaluate the effect of stem cell therapy on the clinical outcomes of ischemic stroke patients. A systematic review and meta-analysis were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A thorough literature search was conducted on PubMed, Scopus, and Cochrane databases. Articles were selected systematically based on the PRISMA protocol and reviewed completely. A total of 19 publications pertaining to stem cell therapy on the ischemic route were included and reviewed. Efficacy outcomes were measured with the National Institutes of Health Stroke Scale, modified Rankin Scale, or Barthel Index.

Results

The results of the meta-analysis indicate that the efficacy outcomes suggest favorable results after stem cell therapy, although not all study results are statistically significant. Stem cell therapy in stroke cases showed a better outcome than standard conservative therapy alone, although our analysis shows that many factors can influence this outcome, and significant effects can only be seen after several months.

Conclusion

The results of this study show promising and satisfying efficacy and a relatively low rate of serious adverse events.

Perioperative stroke: A perspective on challenges and opportunities for experimental treatment and diagnostic strategies

Perioperative stroke is an ischemic or hemorrhagic cerebral event during or up to 30 days after surgery. It is a feared condition due to a relatively high incidence, difficulties in timely detection, and unfavorable outcome compared to spontaneously occurring stroke. Recent preclinical data suggest that specific pathophysiological mechanisms such as aggravated neuroinflammation contribute to the detrimental impact of perioperative stroke. Conventional treatment options are limited in the perioperative setting due to difficult diagnosis and medications affecting coagulation in may cases. On the contrary, the chance to anticipate cerebrovascular events at the time of surgery may pave the way for prevention strategies. This review provides an overview on perioperative stroke incidence, related problems, and underlying pathophysiological mechanisms. Based on this analysis, we assess experimental stroke treatments including neuroprotective approaches, cell therapies, and conditioning medicine strategies regarding their potential use in perioperative stroke. Interestingly, the specific aspects of perioperative stroke might enable a more effective application of experimental treatment strategies such as classical neuroprotection whereas others including cell therapies may be of limited use. We also discuss experimental diagnostic options for perioperative stroke augmenting classical clinical and imaging stroke diagnosis. While some experimental stroke treatments may have specific advantages in perioperative stroke, the paucity of established guidelines or multicenter clinical research initiatives currently limits their thorough investigation.

Final Results of Allogeneic Adipose Tissue-Derived Mesenchymal Stem Cells in Acute Ischemic Stroke (AMASCIS): A Phase II, Randomized, Double-Blind, Placebo-Controlled, Single-Center, Pilot Clinical Trial

Acute ischemic stroke is currently a major cause of disability despite improvement in recanalization therapies. Stem cells represent a promising innovative strategy focused on reduction of neurologic sequelae by enhancement of brain plasticity. We performed a phase IIa, randomized, double-blind, placebo-controlled, single-center, pilot clinical trial. Patients aged ≥60 years with moderate to severe stroke (National Institutes of Health Stroke Scale [NIHSS] 8–20) were randomized (1:1) to receive intravenous adipose tissue–derived mesenchymal stem cells (AD-MSCs) or placebo within the first 2 weeks of stroke onset. The primary outcome was safety, evaluating adverse events (AEs), neurologic and systemic complications, and tumor development. The secondary outcome evaluated treatment efficacy by measuring modified Rankin Scale (mRS), NIHSS, infarct size, and blood biomarkers. We report the final trial results after 24 months of follow-up. Recruitment began in December 2014 and stopped in December 2017 after 19 of 20 planned patients were included. Six patients did not receive study treatment: two due to technical issues and four for acquiring exclusion criteria after randomization. The final study sample was composed of 13 patients (4 receiving AD-MSCs and 9 placebo). One patient in the placebo group died within the first week after study treatment delivery due to sepsis. Two non-treatment-related serious AEs occurred in the AD-MSC group and nine in the placebo group. The total number of AEs and systemic or neurologic complications was similar between the study groups. No injection-related AEs were registered, nor tumor development. At 24 months of follow-up, patients in the AD-MSC group showed a nonsignificantly lower median NIHSS score (interquartile range, 3 [3–5.5] vs 7 [0–8]). Neither treatment group had differences in mRS scores throughout follow-up visits up to month 24. Therefore, intravenous treatment with AD-MSCs within the first 2 weeks from ischemic stroke was safe at 24 months of follow-up.

A contemporary review of therapeutic and regenerative management of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) remains a common and debilitating form of stroke. This neurological emergency must be diagnosed and treated rapidly yet effectively. In this article, we review the medical, surgical, repair, and regenerative treatment options for managing ICH. Topics of focus include the management of blood pressure, intracranial pressure, coagulopathy, and intraventricular hemorrhage, as well as the role of surgery, regeneration, rehabilitation, and secondary prevention. Results of various phase II and III trials are incorporated. In summary, ICH patients should undergo rapid evaluation with neuroimaging, and early interventions should include systolic blood pressure control in the range of 140 mmHg, correction of coagulopathy if indicated, and assessment for surgical intervention. ICH patients should be managed in dedicated neurosurgical intensive care or stroke units where continuous monitoring of neurological status and evaluation for neurological deterioration is rapidly possible. Extravasation of hematoma may be helpful in patients with intraventricular extension of ICH. The goal of care is to reduce mortality and enable multimodal rehabilitative therapy.

Modulating poststroke inflammatory mechanisms: Novel aspects of mesenchymal stem cells, extracellular vesicles and microglia

Inflammation plays an important role in the pathological process of ischemic stroke, and systemic inflammation affects patient prognosis. As resident immune cells in the brain, microglia are significantly involved in immune defense and tissue repair under various pathological conditions, including cerebral ischemia. Although the differentiation of M1 and M2 microglia is certainly oversimplified, changing the activation state of microglia appears to be an intriguing therapeutic strategy for cerebral ischemia. Recent evidence indicates that both mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (EVs) regulate inflammation and modify tissue repair under preclinical stroke conditions. However, the precise mechanisms of these signaling pathways, especially in the context of the mutual interaction between MSCs or MSC-derived EVs and resident microglia, have not been sufficiently unveiled. Hence, this review summarizes the state-of-the-art knowledge on MSC- and MSC-EV-mediated regulation of microglial activity under ischemic stroke conditions with respect to various signaling pathways, including cytokines, neurotrophic factors, transcription factors, and microRNAs.

Clinical neurorestorative cell therapies for stroke

Clinical neurorestorative cell therapies for stroke have been explored for over 20 years. Majority cell therapies have shown neurorestorative effects for stroke on non-double-blind studies. In this review, we summarize types of cell transplantation, transplanted routes, therapeutic time windows, dosage, results of exploring trials or clinical studies, results of multicenter, double-blind or observing-blind, randomized, placebo-controlled clinical trials. The clinical application prospects of majority cell therapies for stroke need to prove their neurorestorative effects through trials with higher-level evidence-based medical evidence. Currently olfactory ensheathing cell is only one kind of cell to show neurorestorative effects through multicenter, double-blind, randomized, placebo-controlled clinical trials, which should be explored to optimize themselves effects and combination with others.

Comparisons of Neurotrophic Effects of Mesenchymal Stem Cells Derived from Different Tissues on Chronic Spinal Cord Injury Rats

Cell-based therapies with mesenchymal stem cells (MSCs) are considered as promising strategies for spinal cord injury (SCI). MSCs have unique characteristics due to differences in the derived tissues. However, relatively few studies have focused on differences in the therapeutic effects of MSCs derived from different tissues. In this study, the therapeutic effects of adipose tissue-derived MSCs, bone marrow-derived MSCs, and cranial bone-derived MSCs (cMSCs) on chronic SCI model rats were compared. MSCs were established from the collected adipose tissue, bone marrow, and cranial bone. Neurotrophic factor expression of each MSC type was analyzed by real-time PCR. SCI rats were established using the weight-drop method and transplanted intravenously with MSCs at 4 weeks after SCI. Hindlimb motor function was evaluated from before injury to 4 weeks after transplantation. Endogenous neurotrophic factor and neural repair factor expression in spinal cord (SC) tissue were examined by real-time PCR and western blot analyses. Although there were no differences in the expression levels of cell surface markers and multipotency, expression of Bdnf, Ngf, and Sort1 (Nt-3) was relatively higher in cMSCs. Transplantation of cMSCs improved motor function of chronic SCI model rats. Although there was no difference in the degree of engraftment of transplanted cells in the injured SC tissue, transplantation of cMSCs enhanced Bdnf, TrkB, and Gap-43 messenger RNA expression and synaptophysin protein expression in injured SC tissue. As compared with MSCs derived other tissues, cMSCs highly express many neurotrophic factors, which improved motor function in chronic SCI model rats by promoting endogenous neurotrophic and neural plasticity factors. These results demonstrate the efficacy of cMSCs in cell-based therapy for chronic SCI.

Longitudinal neuroimaging evaluation of the corticospinal tract in patients with stroke treated with autologous bone marrow cells

Bone marrow mononuclear cells (MNCs) attenuate secondary degeneration and enhance recovery in stroke animal models. In a nonrandomized clinical trial, we imaged 37 patients with stroke: 17 patients treated with MNCs (treated) and 20 patients who received standard of care (nontreated) at 1, 3, and 12 months onset of stroke on 3.0T MRI system. Three-dimensional anatomical and diffusion tensor images were obtained. The integrity of the corticospinal tract was assessed by measuring absolute and relative fractional anisotropy (FA) and mean diffusivity (MD) in the rostral pons (RP), posterior limb of the internal capsule, and corona radiata by drawing regions of interest. Infarct volume and stroke severity, which was assessed via the NIH Stroke Scale (NIHSS), were higher in the MNC group compared with the nontreated patients, which is a major limitation. Overall, the relative FA (rFA) of the nontreated patients exhibited continued reduction and an increase in relative MD (rMD) from 1 to 12 months, whereas despite larger infarcts and higher severity, treated patients displayed an increase in rFA from 3 to 12 months and no change in rMD. Contrary to the nontreated group, the treated patients' rFA was also significantly correlated (P < .05) with NIHSS score in the RP at all time points, whereas rMD at the last two.

Are We Ready for Cell Therapy to Treat Stroke?

Clinical trials of cell therapies that target stroke started at the beginning of this century and they have experienced a significant boost in recent years as a result of promising data from basic research studies. The increase in the information available has paved the way to carry out more innovative and varied human studies. Efforts have focused on the search for a safe and effective treatment to stimulate neuro-regeneration in the brain and to reduce the sequelae of stroke in patients. Therefore, this review aims to evaluate the clinical trials using cell therapy to treat stroke published to date and assess their limitations. From 2000 to date, most of the published clinical trials have focused on phases I or II, and the vast majority of them demonstrate that stem cells are essentially safe to use when administered by different routes, with transient and mild adverse events that do not generally have severe consequences for health. In general, there is considerable variation in the trials in terms of statistical design, sample size, the cells used, the routes of administration, and the functional assessments (both at baseline and follow-up), making it difficult to compare the studies. From this general description, possibly the experimental protocol is the main element to improve in future studies. Establishing an adequate experimental and statistical design will be essential to obtain favorable and reliable results when conducting phase III clinical trials. Thus, it is necessary to standardize the criteria used in these clinical trials in order to aid comparison. Shortly, cell therapy will be a key approach in the treatment of stroke if adequate and comprehensive levels of recovery are to be achieved.

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.

Stem Cell Therapies for Ischemic Stroke: A Systematic Review

Stroke is one of the leading causes of death and disability worldwide. It is associated with a high economic burden, causing an increasing demand for highly effective, curative, and long-lasting therapies. Stem cells are unique human cells that have the capacity for developing into specialized cell types with the potential for facilitating regeneration and repair of damaged tissues. Therefore, many preclinical studies have shown the feasibility, safety, and efficacy of stem cell-based therapies; however, the evidence is still inadequate for their therapeutic use in humans. We employed a systematic approach to search published data from 2000 to 2020 on five main databases: PubMed, PubMed Central, Google Scholar, ScienceDirect, and Medline. Two research registries were also searched: the Cochrane Registry and clinicaltrial.gov. Data was collected after applying inclusion and exclusion criteria and studies were appraised critically. Both Medical Subject Headings (MeSH) and regular keyword search strategies were employed. The findings of this study are in line with previously reported studies in which stem cell-based therapies were found to be relatively safe, feasible, and effective.

Neurotrophin-3 upregulation associated with intravenous transplantation of bone marrow mononuclear cells induces axonal sprouting and motor functional recovery in the long term after neocortical ischaemia

Bone marrow mononuclear cells (BMMCs) have been identified as a relevant therapeutic strategy for the treatment of several chronic diseases of the central nervous system. The aim of this work was to evaluate whether intravenous treatment with BMMCs facilitates the reconnection of lesioned cortico-cortical and cortico-striatal pathways, together with motor recovery, in injured adult Wistar rats using an experimental model of unilateral focal neocortical ischaemia. Animals with cerebral cortex ischaemia underwent neural tract tracing for axonal fibre analysis, differential expression analysis of genes involved in apoptosis and neuroplasticity by RT-qPCR, and motor performance assessment by the cylinder test. Quantitative and qualitative analyses of axonal fibres labelled by an anterograde neural tract tracer were performed. Ischaemic animals treated with BMMCs showed a significant increase in axonal sprouting in the ipsilateral neocortex and in the striatum contralateral to the injured cortical areas compared to untreated rodents. In BMMC-treated animals, there was a trend towards upregulation of the Neurotrophin-3 gene compared to the other genes, as well as modulation of apoptosis by BMMCs. On the 56th day after ischaemia, BMMC-treated animals showed significant improvement in motor performance compared to untreated rats. These results suggest that in the acute phase of ischaemia, Neurotrophin-3 is upregulated in response to the lesion itself. In the long run, therapy with BMMCs causes axonal sprouting, reconnection of damaged neuronal circuitry and a significant increase in motor performance.

Stem Cell Treatment for Ischemic Stroke Recovery

The role of cellular transplantation to promote functional recovery after stroke has been evaluated over the last two decades. Preclinical studies first established the potential for cultured neuronal cells derived from a teratocarcinoma cell line to be tested for safety and efficacy in the treatment of human stroke. In animal models of stroke that caused reproducible learning and motor deficits, injection of neuronal cells resulted in a return of learning behavior, retention time, and motor function. Clinical trials followed. Additional work with cells derived from a bone marrow neuroprogenitor line, fetal cortical stem cells, and other cell sources showed promise in preclinical studies and then these cells were tested in clinical studies. This report reviews the different biological repair approaches using cell implants, discusses clinical trial design and surgical methods, and the current state of research.

The Next Step in the Treatment of Stroke

Although many patients do not receive reperfusion therapy because of delayed presentation and/or severity and location of infarct, new reperfusion approaches are expanding the window of intervention. Novel application of neuroprotective agents in combination with the latest methods of reperfusion provide a path to improved stroke intervention outcomes. We examine why neuroprotective agents have failed to translate to the clinic and provide suggestions for new approaches. New developments in recanalization therapy in combination with therapeutics evaluated in parallel animal models of disease will allow for novel, intra-arterial deployment of therapeutic agents over a vastly expanded therapeutic time window and with greater likelihood success. Although the field of neuronal, endothelial, and glial protective therapies has seen numerous large trials, the application of therapies in the context of newly developed reperfusion strategies is still in its infancy. Given modern imaging developments, evaluation of the penumbra will likely play a larger role in the evolving management of stroke. Increasingly more patients will be screened with neuroimaging to identify patients with adequate collateral blood supply allowing for delayed rescue of the penumbra. These patients will be ideal candidates for therapies such as reperfusion dependent therapeutic agents that pair optimally with cutting-edge reperfusion techniques.

Intravenous Bone Marrow Mononuclear Cells Transplantation Improves the Effect of Training in Chronic Stroke Mice

There is no effective treatment for chronic stroke if the acute or subacute phase is missed. Rehabilitation alone cannot easily achieve a dramatic recovery in function. In contrast to significant therapeutic effects of bone marrow mononuclear cells (BM-MNC) transplantation for acute stroke, mild and non-significant effects have been shown for chronic stroke. In this study, we have evaluated the effect of a combination of BM-MNC transplantation and neurological function training in chronic stroke. The effect of BM-MNC on neurological functional was tested four weeks after permanent middle cerebral artery occlusion (MCAO) insult in mice. BM-MNC (1 × 10⁵cells in 100 μl PBS) were injected into the vein of MCAO model mice, followed by behavioral tests as functional evaluations. Interestingly, there was a significant therapeutic effect of BM-MNC only when repeated training was performed. This suggested that cell therapy alone was not sufficient for chronic stroke treatment; however, training with cell therapy was effective. The combination of these differently targeted therapies provided a significant benefit in the chronic stroke mouse model. Therefore, targeted cell therapy via BM-MNC transplantation with appropriate training presents a promising novel therapeutic option for patients in the chronic stroke period.

Stroke treatment: Is exosome therapy superior to stem cell therapy?

Stroke is one of the most common causes of disability and death, and currently, ideal clinical treatment is lacking. Stem cell transplantation is a widely-used treatment approach for stroke. When compared with other types of stem cells, bone marrow mesenchymal stem cells (BMSCs) have been widely studied because of their many advantages. The paracrine effect is the primary mechanism for stem cells to play their role, and exosomes play an essential role in the paracrine effect. When compared with cell therapy, cell-free exosome therapy can prevent many risks and difficulties, and therefore, represents a promising and novel approach for treatment. In this study, we reviewed the research progress in the application of BMSCs-derived exosomes (BMSCs-exos) and BMSCs in the treatment of stroke. In addition, the advantages and disadvantages of cell therapy and cell-free exosome therapy were described, and the possible factors that hinder the introduction of these two treatments into the clinic were analyzed. Furthermore, we reviewed the current optimization methods of cell therapy and cell-free exosome therapy. Taken together, we hypothesize that cell-free exosome therapy will have excellent research prospects in the future, and therefore, it is worth further exploring. There are still some issues that need to be further addressed. For example, differences between the in vivo microenvironment and in vitro culture conditions will affect the paracrine effect of stem cells. Most importantly, we believe that more preclinical and clinical design studies are required to compare the efficacy of stem cells and exosomes.

Optimizing Stem Cell Therapy after Ischemic Brain Injury

Stem cells have been used for regenerative and therapeutic purposes in a variety of diseases. In ischemic brain injury, preclinical studies have been promising, but have failed to translate results to clinical trials. We aimed to explore the application of stem cells after ischemic brain injury by focusing on topics such as delivery routes, regeneration efficacy, adverse effects, and in vivo potential optimization. PUBMED and Web of Science were searched for the latest studies examining stem cell therapy applications in ischemic brain injury, particularly after stroke or cardiac arrest, with a focus on studies addressing delivery optimization, stem cell type comparison, or translational aspects. Other studies providing further understanding or potential contributions to ischemic brain injury treatment were also included. Multiple stem cell types have been investigated in ischemic brain injury treatment, with a strong literature base in the treatment of stroke. Studies have suggested that stem cell administration after ischemic brain injury exerts paracrine effects via growth factor release, blood-brain barrier integrity protection, and allows for exosome release for ischemic injury mitigation. To date, limited studies have investigated these therapeutic mechanisms in the setting of cardiac arrest or therapeutic hypothermia. Several delivery modalities are available, each with limitations regarding invasiveness and safety outcomes. Intranasal delivery presents a potentially improved mechanism, and hypoxic conditioning offers a potential stem cell therapy optimization strategy for ischemic brain injury. The use of stem cells to treat ischemic brain injury in clinical trials is in its early phase; however, increasing preclinical evidence suggests that stem cells can contribute to the down-regulation of inflammatory phenotypes and regeneration following injury. The safety and the tolerability profile of stem cells have been confirmed, and their potent therapeutic effects make them powerful therapeutic agents for ischemic brain injury patients.

Cell Therapies under Clinical Trials and Polarized Cell Therapies in Pre-Clinical Studies to Treat Ischemic Stroke and Neurological Diseases: A Literature Review

Stroke remains a major cause of serious disability because the brain has a limited capacity to regenerate. In the last two decades, therapies for stroke have dramatically changed. However, half of the patients cannot achieve functional independence after treatment. Presently, cell-based therapies are being investigated to improve functional outcomes. This review aims to describe conventional cell therapies under clinical trial and outline the novel concept of polarized cell therapies based on protective cell phenotypes, which are currently in pre-clinical studies, to facilitate functional recovery after post-reperfusion treatment in patients with ischemic stroke. In particular, non-neuronal stem cells, such as bone marrow-derived mesenchymal stem/stromal cells and mononuclear cells, confer no risk of tumorigenesis and are safe because they do not induce rejection and allergy; they also pose no ethical issues. Therefore, recent studies have focused on them as a cell source for cell therapies. Some clinical trials have shown beneficial therapeutic effects of bone marrow-derived cells in this regard, whereas others have shown no such effects. Therefore, more clinical trials must be performed to reach a conclusion. Polarized microglia or peripheral blood mononuclear cells might provide promising therapeutic strategies after stroke because they have pleiotropic effects. In traumatic injuries and neurodegenerative diseases, astrocytes, neutrophils, and T cells were polarized to the protective phenotype in pre-clinical studies. As such, they might be useful therapeutic targets. Polarized cell therapies are gaining attention in the treatment of stroke and neurological diseases.

Application of Stem Cells in Stroke: A Multifactorial Approach

Stroke has a debilitating effect on the human body and a serious negative effect on society, with a global incidence of one in every six people. According to the World Health Organization, 15 million people suffer stroke worldwide each year. Of these, 5 million die and another 5 million are permanently disabled. Motor and cognitive deficits like hemiparesis, paralysis, chronic pain, and psychomotor and behavioral symptoms can persist long term and prevent the patient from fully reintegrating into society, therefore continuing to add to the costly healthcare burden of stroke. Regenerative medicine using stem cells seems to be a panacea for sequelae after stroke. Stem cell-based therapy aids neuro-regeneration and neuroprotection for neurological recovery in patients. However, the use of stem cells as a therapy in stroke patients still needs a lot of research at both basic and translational levels. As well as the mode of action of stem cells in reversing the symptoms not being clear, there are several clinical parameters that need to be addressed before establishing stem cell therapy in stroke, such as the type of stem cells to be administered, the number of stem cells, the timing of dosage, whether dose-boosters are required, the route of administration, etc. There are upcoming prospects of cell-free therapy also by using exosomes derived from stem cells. There are several ongoing pre-clinical studies aiming to answer these questions. Despite still being in the development stage, stem cell therapy holds great potential for neurological rehabilitation in patients suffering from stroke.

The 2019 yearbook of Neurorestoratology

Time is infinite movement in constant motion. We are glad to see that Neurorestoratology, a new discipline, has grown into a rich field involving many global researchers in recent years. In this 2019 yearbook of Neurorestoratology, we introduce the most recent advances and achievements in this field, including findings on the pathogenesis of neurological diseases, neurorestorative mechanisms, and clinical therapeutic achievements globally. Many patients have benefited from treatments involving cell therapies, neurostimulation/neuromodulation, brain–computer interface, neurorestorative surgery or pharmacy, and many others. Clinical physicians can refer to this yearbook with the latest knowledge and apply it to clinical practice.

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.