A two-year follow-up study of cotransplantation with neural stem/progenitor cells and mesenchymal stromal cells in ischemic stroke patients

Stem cell therapy as a promising approach for ischemic stroke treatment

Ischemia as the most common type of stroke is the main cause of death and disability in the world. However, there are few therapeutic approaches to treat ischemic stroke. The common approach to the treatment of ischemia includes surgery-cum-chemical drugs. Surgery and chemical drugs are used to remove blood clots to prevent the deterioration of the nervous system. Given the surgical hazards and the challenges associated with chemical drugs, these cannot be considered safe approaches to the treatment of brain ischemia. Besides surgery-cum-chemical drugs, different types of stem cells including mesenchymal stem cells and neurological stem cells have been considered to treat ischemic stroke. Therapeutic approaches utilizing stem cells to treat strokes are promising because of their neuroprotective and regenerative benefits. However, the mechanisms by which the transplanted stem cells perform their precisely actions are unknown. The purpose of this study is to critically review stem cell-based therapeutic approaches for ischemia along with related challenges.

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.

Priming and Combined Strategies for the Application of Mesenchymal Stem Cells in Ischemic Stroke: A Promising Approach

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) administration and mechanical thrombectomy are the main treatments but have a narrow time window. Mesenchymal stem cells (MSCs), which are easily scalable in vitro and lack ethical concerns, possess the potential to differentiate into various types of cells and secrete a great number of growth factors for neuroprotection and regeneration. Moreover, MSCs have low immunogenicity and tumorigenic properties, showing safety and preliminary efficacy both in preclinical studies and clinical trials of IS. However, it is unlikely that MSC treatment alone will be sufficient to maximize recovery due to the low survival rate of transplanted cells and various mechanisms of ischemic brain damage in the different stages of IS. Preconditioning was used to facilitate the homing, survival, and secretion ability of the grafted MSCs in the ischemic region, while combination therapies are alternatives that can maximize the treatment effects, focusing on multiple therapeutic targets to promote stroke recovery. In this case, the combination therapy can yield a synergistic effect. In this review, we summarize the type of MSCs, preconditioning methods, and combined strategies as well as their therapeutic mechanism in the treatment of IS to accelerate the transformation from basic research to clinical application.

Allogeneic Stem Cell Therapy for Acute Ischemic Stroke: The Phase 2/3 TREASURE Randomized Clinical Trial

Importance

Cell therapy is a promising treatment approach for stroke and other diseases. However, it is unknown whether MultiStem (HLCM051), a bone marrow-derived, allogeneic, multipotent adult progenitor cell product, has the potential to treat ischemic stroke.

Objective

To assess the efficacy and safety of MultiStem when administered within 18 to 36 hours of ischemic stroke onset.

Design, Setting, and Participants

The Treatment Evaluation of Acute Stroke Using Regenerative Cells (TREASURE) multicenter, double-blind, parallel-group, placebo-controlled phase 2/3 randomized clinical trial was conducted at 44 academic and clinical centers in Japan between November 15, 2017, and March 29, 2022. Inclusion criteria were age 20 years or older, presence of acute ischemic stroke (National Institutes of Health Stroke Scale [NIHSS] score of 8-20 at baseline), confirmed acute infarction involving the cerebral cortex and measuring more than 2 cm on the major axis (determined with diffusion-weighted magnetic resonance imaging), and a modified Rankin Scale (mRS) score of 0 or 1 before stroke onset. Data analysis was performed between May 9 and August 15, 2022.

Exposure

Patients were randomly assigned to either intravenous MultiStem in 1 single unit of 1.2 billion cells or intravenous placebo within 18 to 36 hours of ischemic stroke onset.

Main Outcomes and Measures

The primary end points were safety and excellent outcome at day 90, measured as a composite of a modified Rankin Scale (mRS) score of 1 or less, a NIHSS score of 1 or less, and a Barthel index score of 95 or greater. The secondary end points were excellent outcome at day 365, mRS score distribution at days 90 and 365, and mRS score of 0 to 1 and 0 to 2 at day 90. Statistical analysis of efficacy was performed using the Cochran-Mantel-Haenszel test.

Results

This study included 206 patients (104 received MultiStem and 102 received placebo). Their mean age was 76.5 (range, 35-95) years, and more than half of patients were men (112 [54.4%]). There were no between-group differences in primary and secondary end points. The proportion of excellent outcomes at day 90 did not differ significantly between the MultiStem and placebo groups (12 [11.5%] vs 10 [9.8%], P = .90; adjusted risk difference, 0.5% [95% CI, -7.3% to 8.3%]). The frequency of adverse events was similar between treatment groups.

Conclusions and Relevance

In this randomized clinical trial, intravenous administration of allogeneic cell therapy within 18 to 36 hours of ischemic stroke onset was safe but did not improve short-term outcomes. Further research is needed to determine whether MultiStem therapy for ischemic stroke has a beneficial effect in patients who meet specific criteria, as indicated by the exploratory analyses in this study.

Trial Registration

ClinicalTrials.gov Identifier: NCT02961504.

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.

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.

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.

Engineering optical tools for remotely controlled brain stimulation and regeneration

Neurological disorders are one of the world's leading medical and societal challenges due to the lack of efficacy of the first line treatment. Although pharmacological and non-pharmacological interventions have been employed with the aim of regulating neuronal activity and survival, they have failed to avoid symptom relapse and disease progression in the vast majority of patients. In the last 5 years, advanced drug delivery systems delivering bioactive molecules and neuromodulation strategies have been developed to promote tissue regeneration and remodel neuronal circuitry. However, both approaches still have limited spatial and temporal precision over the desired target regions. While external stimuli such as electromagnetic fields and ultrasound have been employed in the clinic for non-invasive neuromodulation, they do not have the capability of offering single-cell spatial resolution as light stimulation. Herein, we review the latest progress in this area of study and discuss the prospects of using light-responsive nanomaterials to achieve on-demand delivery of drugs and neuromodulation, with the aim of achieving brain stimulation and regeneration.

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.

Nanoparticle and Stem Cell Combination Therapy for the Management of Stroke

Stroke is currently one of the primary causes of morbidity and mortality worldwide. Unfortunately, the available treatments for stroke are still extremely limited. Indeed, stem cell (SC) therapy is a new option for the treatment of stroke that could significantly expand the therapeutic time window of stroke. Some proposed mechanisms for stroke-based SC therapy are the incorporation of SCs into the host brain to replace dead or damaged cells/tissues. Moreover, acute cell delivery can inhibit apoptosis and decrease lesion size, providing immunomudolatory and neuroprotection effects. However, several major SC problems related to SCs such as homing, viability, uncontrolled differentiation, and possible immune response, have limited SC therapy. A combination of SC therapy with nanoparticles (NPs) can be a solution to address these challenges. NPs have received considerable attention in regulating and controlling the behavior of SCs because of their unique physicochemical properties. By reviewing the pathophysiology of stroke and the therapeutic benefits of SCs and NPs, we hypothesize that combined therapy will offer a promising future in the field of stroke management. In this work, we discuss recent literature in SC research combined with NP-based strategies that may have a synergistic outcome after stroke incidence.

Mesenchymal stem cell therapy for neurological disorders: The light or the dark side of the force?

Neurological disorders are recognized as major causes of death and disability worldwide. Because of this, they represent one of the largest public health challenges. With awareness of the massive burden associated with these disorders, came the recognition that treatment options were disproportionately scarce and, oftentimes, ineffective. To address these problems, modern research is increasingly looking into novel, more effective methods to treat neurological patients; one of which is cell-based therapies. In this review, we present a critical analysis of the features, challenges, and prospects of one of the stem cell types that can be employed to treat numerous neurological disorders-mesenchymal stem cells (MSCs). Despite the fact that several studies have already established the safety of MSC-based treatment approaches, there are still some reservations within the field regarding their immunocompatibility, heterogeneity, stemness stability, and a range of adverse effects-one of which is their tumor-promoting ability. We additionally examine MSCs' mechanisms of action with respect to in vitro and in vivo research as well as detail the findings of past and ongoing clinical trials for Parkinson's and Alzheimer's disease, ischemic stroke, glioblastoma multiforme, and multiple sclerosis. Finally, this review discusses prospects for MSC-based therapeutics in the form of biomaterials, as well as the use of electromagnetic fields to enhance MSCs' proliferation and differentiation into neuronal cells.

The role of mesenchymal stem cell transplantation for ischemic stroke and recent research developments

Ischemic stroke is a common cerebrovascular disease that seriously affects human health. However, most patients do not practice self-care and cannot rely on the current clinical treatment for guaranteed functional recovery. Stem cell transplantation is an emerging treatment studied in various central nervous system diseases. More importantly, animal studies show that transplantation of mesenchymal stem cells (MSCs) can alleviate neurological deficits and bring hope to patients suffering from ischemic stroke. This paper reviews the biological characteristics of MSCs and discusses the mechanism and progression of MSC transplantation to provide new therapeutic directions for ischemic stroke.

Neural Stem Cells Therapy for Ischemic Stroke: Progress and Challenges

Ischemic stroke, with its high morbidity and mortality, is the most common cerebrovascular accident and results in severe neurological deficits. Despite advances in medical and surgical intervention, post-stroke therapies remain scarce, which seriously affects the quality of life of patients. Over the past decades, stem cell transplantation has been recognized as very promising therapy for neurological diseases. Neural stem cell (NSC) transplantation is the optimal choice for ischemic stroke as NSCs inherently reside in the brain and can potentially differentiate into a variety of cell types within the central nervous system. Recent research has demonstrated that NSC transplantation can facilitate neural recovery after ischemic stroke, but the mechanisms still remain unclear, and basic/clinical studies of NSC transplantation for ischemic stroke have not yet been thoroughly elucidated. We thus, in this review, provide a futher understanding of the therapeutic role of NSCs for ischemic stroke, and evaluate their prospects for future application in clinical patients of ischemic stroke.

Safety and Clinical Efficacy of Mesenchymal Stem Cell Treatment in Traumatic Spinal Cord Injury, Multiple Sclerosis and Ischemic Stroke - A Systematic Review and Meta-Analysis

Background

Mesenchymal stem cells (MSCs) is an attractive candidate in regenerative research and clinical trials have assessed their therapeutic potential in different neurological conditions with disparate etiologies. In this systematic review, we aimed to assess safety and clinical effect of MSC treatment in traumatic spinal cord injury (TSCI), multiple sclerosis (MS) and ischemic stroke (IS).

Methods

A systematic search was performed 2021-12-10 in MEDLINE, EMBASE, Web of Science and Cochrane where clinical studies assessing MSC treatment in TSCI, MS or IS were included. Studies without control group were excluded for efficacy analysis, but included in the safety analysis. For efficacy, AIS score, EDSS score and mRS were used as clinical endpoints and assessed in a meta-analysis using the random effects model.

Findings

Of 5,548 identified records, 54 studies were included. Twenty-six studies assessed MSC treatment in TSCI, 14 in MS and nine in IS, of which seven, seven and five studies were controlled, respectively. There were seven serious adverse events (SAEs), of which four were related to the surgical procedure and included one death due to complications following the implantation of MSCs. Three SAEs were considered directly related to the MSC treatment and all these had a transient course. In TSCI, a meta-analysis showed no difference in conversion from AIS A to C and a trend toward more patients treated with MSCs improving from AIS A to B as compared to controls (p = 0.05). A subgroup analysis performed per protocol, showed more MSC treated patients improving from AIS A to C in studies including patients within 8 weeks after injury (p = 0.04). In MS and IS, there were no significant differences in clinical outcomes between MSC treated patients and controls as measured by EDSS and mRS, respectively.

Interpretation

MSC-treatment is safe in patients with TSCI, MS and IS, although surgical implantation of MSC led to one fatal outcome in TSCI. There was no clear clinical benefit of MSC treatment, but this is not necessarily a proof of inefficacy due to the low number of controlled studies. Future studies assessing efficacy of MSC treatment should aim to do this in randomized, controlled studies.

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.

Current status of ischemic stroke treatment: From thrombolysis to potential regenerative medicine

Ischemic stroke is a major cause of death and disability worldwide and is expected to increase in the future with the aging population. Currently, there are no clinically available treatments for damage sustained during an ischemic stroke, but much research is being conducted in this area. In this review, we will introduce current ischemic stroke treatments along with their limitations, as well as research on potential short and long-term future treatments. There are advantages and disadvantages in these potential treatments, but our understanding of these methods and their effectiveness in clinical trials are improving. We are confident that some future treatments introduced in this review will become commonly used in clinical settings in the future.

Human Neural Stem Cells for Cell-Based Medicinal Products

Neural stem cells represent an attractive tool for the development of regenerative therapies and are being tested in clinical trials for several neurological disorders. Human neural stem cells can be isolated from the central nervous system or can be derived in vitro from pluripotent stem cells. Embryonic sources are ethically controversial and other sources are less well characterized and/or inefficient. Recently, isolation of NSC from the cerebrospinal fluid of patients with spina bifida and with intracerebroventricular hemorrhage has been reported. Direct reprogramming may become another alternative if genetic and phenotypic stability of the reprogrammed cells is ensured. Here, we discuss the advantages and disadvantages of available sources of neural stem cells for the production of cell-based therapies for clinical applications. We review available safety and efficacy clinical data and discuss scalability and quality control considerations for manufacturing clinical grade cell products for successful clinical application.

Direct differentiation of tonsillar biopsy-derived stem cells to the neuronal lineage

BACKGROUND

Neurological disorders are considered one of the greatest burdens to global public health and a leading cause of death. Stem cell therapies hold great promise for the cure of neurological disorders, as stem cells can serve as cell replacement, while also secreting factors to enhance endogenous tissue regeneration. Adult human multipotent stem cells (MSCs) reside on blood vessels, and therefore can be found in many tissues throughout the body, including palatine tonsils. Several studies have reported the capacity of MSCs to differentiate into, among other cell types, the neuronal lineage. However, unlike the case with embryonic stem cells, it is unclear whether MSCs can develop into mature neurons.

METHODS

Human tonsillar MSCs (T-MSCs) were isolated from a small, 0.6-g sample, of tonsillar biopsies with high viability and yield as we recently reported. Then, these cells were differentiated by a rapid, multi-stage procedure, into committed, post-mitotic, neuron-like cells using defined conditions.

RESULTS

Here we describe for the first time the derivation and differentiation of tonsillar biopsy-derived MSCs (T-MSCs), by a rapid, multi-step protocol, into post-mitotic, neuron-like cells using defined conditions without genetic manipulation. We characterized our T-MSC-derived neuronal cells and demonstrate their robust differentiation in vitro.

CONCLUSIONS

Our procedure leads to a rapid neuronal lineage commitment and loss of stemness markers, as early as three days following neurogenic differentiation. Our studies identify biopsy-derived T-MSCs as a potential source for generating neuron-like cells which may have potential use for in vitro modeling of neurodegenerative diseases or cell replacement therapies.

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.

Mesenchymal Stromal Cells Perspective: New Potential Therapeutic for the Treatment of Neurological Diseases

Several studies have shown that mesenchymal stromal/stem cells (MSCs) exert their neuroprotective and neurorestorative efficacy via the secretion of neurotrophic factors. Based on these studies, many clinical trials using MSCs for the treatment of neurological disorders have been conducted, and results regarding their feasibility and efficacy have been reported. The present review aims to highlight the characteristics and basic research regarding the role of MSCs in neurological disease and to discuss the recent progress in clinical trials using MSCs to treat various neurological disorders.

Mechanism of White Matter Injury and Promising Therapeutic Strategies of MSCs After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke with high disability and high mortality rates, and there is no effective treatment. The predilection site of ICH is in the area of the basal ganglia and internal capsule (IC), where exist abundant white matter (WM) fiber tracts, such as the corticospinal tract (CST) in the IC. Proximal or distal white matter injury (WMI) caused by intracerebral parenchymal hemorrhage is closely associated with poor prognosis after ICH, especially motor and sensory dysfunction. The pathophysiological mechanisms involved in WMI are quite complex and still far from clear. In recent years, the neuroprotection and repairment capacity of mesenchymal stem cells (MSCs) has been widely investigated after ICH. MSCs exert many unique biological effects, including self-recovery by producing growth factors and cytokines, regenerative repair, immunomodulation, and neuroprotection against oxidative stress, providing a promising cellular therapeutic approach for the treatment of WMI. Taken together, our goal is to discuss the characteristics of WMI following ICH, including the mechanism and potential promising therapeutic targets of MSCs, aiming at providing new clues for future therapeutic strategies.

Intra-Arterial Stem Cell Transplantation in Experimental Stroke in Rats: Real-Time MR Visualization of Transplanted Cells Starting With Their First Pass Through the Brain With Regard to the Therapeutic Action

Cell therapy is an emerging approach to stroke treatment with a potential to limit brain damage and enhance its restoration after the acute phase of the disease. In this study we tested directly reprogrammed neural precursor cells (drNPC) derived from adult human bone marrow cells in the rat middle cerebral artery occlusion (MCAO) model of acute ischemic stroke using human placenta mesenchymal stem cells (pMSC) as a positive control with previously confirmed efficacy. Cells were infused into the ipsilateral (right) internal carotid artery of male Wistar rats 24 h after MCAO. The main goal of this work was to evaluate real-time distribution and subsequent homing of transplanted cells in the brain. This was achieved by performing intra-arterial infusion directly inside the MRI scanner and allowed transplanted cells tracing starting from their first pass through the brain vessels. Immediately after transplantation, cells were observed in the periphery of the infarct zone and in the brain stem, 15 min later small numbers of cells could be discovered deep in the infarct core and in the contralateral hemisphere, where drNPC were seen earlier and in greater numbers than pMSC. Transplanted cells in both groups could no longer be detected in the rat brain 48-72 h after infusion. Histological and histochemical analysis demonstrated that both the drNPC and pMSC were localized inside blood vessels in close contact with the vascular wall. No passage of labeled cells through the blood brain barrier was observed. Additionally, the therapeutic effects of drNPC and pMSC were compared. Both drNPC and pMSC induced substantial attenuation of neurological deficits evaluated at the 7th and 14th day after transplantation using the modified neurological severity score (mNSS). Some of the effects of drNPC and pMSC, such as the influence on the infarct volume and the survival rate of animals, differed. The results suggest a paracrine mechanism of the positive therapeutic effects of IA drNPC and pMSC infusion, potentially enhanced by the cell-cell interactions. Our data also indicate that the long-term homing of transplanted cells in the brain is not necessary for the brain's functional recovery.

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.

Research progress on the therapeutic effect of olfactory ensheathing cell transplantation on ischemic stroke

Olfactory ensheathing cells (OECs) are a special type of glial cell in the olfactory system, which exhibit neuroprotective, immunomodulatory, and angiogenic effects. Although many studies have focused on the reversal of demyelination and axonal degeneration (during spinal cord injury) by OECs, few reports have focused on the ability of OECs to repair ischemic nerve injury. This article reviews the protective effects of OEC transplantation in ischemic stroke and provides a theoretical basis and new strategy for OEC transplantation in the treatment of ischemic stroke.

Combined Cell Therapy in the Treatment of Neurological Disorders

Cell therapy of neurological diseases is gaining momentum. Various types of stem/progenitor cells and their derivatives have shown positive therapeutic results in animal models of neurological disorders and in clinical trials. Each tested cell type proved to have its advantages and flaws and unique cellular and molecular mechanism of action, prompting the idea to test combined transplantation of two or more types of cells (combined cell therapy). This review summarizes the results of combined cell therapy of neurological pathologies reported up to this point. The number of papers describing experimental studies or clinical trials addressing this subject is still limited. However, its successful application to the treatment of neurological pathologies including stroke, spinal cord injury, neurodegenerative diseases, Duchenne muscular dystrophy, and retinal degeneration has been reported in both experimental and clinical studies. The advantages of combined cell therapy can be realized by simple summation of beneficial effects of different cells. Alternatively, one kind of cells can support the survival and functioning of the other by enhancing the formation of optimum environment or immunomodulation. No significant adverse events were reported. Combined cell therapy is a promising approach for the treatment of neurological disorders, but further research needs to be conducted.

Revisiting Stem Cell-Based Clinical Trials for Ischemic Stroke

Stroke is the leading cause of serious long-term disability, significantly reducing mobility in almost half of the affected patients aged 65 years and older. There are currently no proven neurorestorative treatments for chronic stroke. To address the complex problem of restoring function in ischemic brain tissue, stem cell transplantation-based therapies have emerged as potential restorative therapies. Aligning with the major cell types found within the ischemic brain, stem-cell-based clinical trials for ischemic stroke have fallen under three broad cell lineages: hematopoietic, mesenchymal, and neural. In this review article, we will discuss the scientific rationale for transplanting cells from each of these lineages and provide an overview of published and ongoing trials using this framework.

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.

Beyond the Hippocampus and the SVZ: Adult Neurogenesis Throughout the Brain

Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.

Safety and Efficacy of Stem Cell Therapy in Patients With Ischemic Stroke

Stem cell therapy is emerging as a promising treatment strategy to treat patients with stroke. While there are established modes of treatment for stroke patients such as thrombolysis and endovascular intervention, most of the stroke patients frequently end up with major residual deficits or even death. The use of stem cells to treat stroke has been found to be beneficial in the animal models but strict evidence for the same in humans is still lacking. We reviewed 13 clinical trials of stem cell therapy in stroke patients conducted between 2014 and 2020 based on the search using the database PubMed, and the clinical trial registry (www.clinicaltrials.gov). We aimed to assess the safety and efficacy of stem cell treatment in stroke patients who participated in the trials. Quality assessment of the clinical trials revealed a sub-optimal score. We found mixed results regarding the efficacy of stem cells in the treatment of ischemic stroke although we could not do a quantitative analysis of the effect outcomes. Assessment for safety revealed promising results as there were only minor side effects related to cell therapy. Although stem cell therapy seems to be a promising strategy to treat stroke patients in the future, we concluded that the field needs more evidence regarding the safety and efficacy of the use of stem cells in stroke patients before we use them in the clinic.

Stem cell homing, tracking and therapeutic efficiency evaluation for stroke treatment using nanoparticles: A systematic review

BACKGROUND

Stroke is the second leading cause of death worldwide. There is a real need to develop treatment strategies for reducing neurological deficits in stroke survivors, and stem cell (SC) therapeutics appear to be a promising alternative for stroke therapy that can be used in combination with approved thrombolytic or thrombectomy approaches. However, the efficacy of SC therapy depends on the SC homing ability and engraftment into the injury site over a long period of time. Nonetheless, tracking SCs from their niche to the target tissues is a complex process.

AIM

To evaluate SC migration homing, tracking and therapeutic efficacy in the treatment of stroke using nanoparticles

METHODS

A systematic literature search was performed to identify articles published prior to November 2019 that were indexed in PubMed and Scopus. The following inclusion criteria were used: (1) Studies that used in vivo models of stroke or ischemic brain lesions; (2) Studies of SCs labeled with some type of contrast agent for cell migration detection; and (3) Studies that involved in vivo cellular homing and tracking analysis.

RESULTS

A total of 82 articles were identified by indexing in Scopus and PubMed. After the inclusion criteria were applied, 35 studies were selected, and the articles were assessed for eligibility; ultimately, only 25 studies were included. Most of the selected studies used SCs from human and mouse bone marrow labeled with magnetic nanoparticles alone or combined with fluorophore dyes. These cells were administered in the stroke model (to treat middle cerebral artery occlusion in 74% of studies and for photothrombotic induction in 26% of studies). Fifty-three percent of studies used xenogeneic grafts for cell therapy, and the migration homing and tracking evaluation was performed by magnetic resonance imaging as well as other techniques, such as near-infrared fluorescence imaging (12%) or bioluminescence assays (12%).

CONCLUSION

Our systematic review provided an up-to-date evaluation of SC migration homing and the efficacy of cellular therapy for stroke treatment in terms of functional and structural improvements in the late stage.

Research trends of stem cells in ischemic stroke from 1999 to 2018: A bibliometric analysis

OBJECTIVE

Many studies have evaluated the safety and efficacy of stem cells as therapeutic agents for ischemic stroke. We aimed to quantitatively assess the research trends of stem cell therapy for ischemic stroke.

PATIENTS AND METHODS

We searched the Web of Science Core Collection to identify relevant publications between 1999 and 2018. We used HistCite to summarize the critical information, including yearly records, authors, countries/regions, and institutions. VOSviewer was applied to map the collaborations between studies. Based on the title and abstract of each publication, MeSH terms were obtained using Medical Text Indexer to demonstrate evolutions of topic hotspots.

RESULTS

From 1999-2018, there were a total of 3,741 publications exploring the prospect of stem cells in ischemic stroke. Annual publication outputs grew from six records to 366 records. Stroke was the most high-profile journal because of its ranking first on the top productive and co-cited journal lists. The United States of America and China were the two most contributive countries of stem-cell research of ischemic stroke. Researchers were supposed to follow studies from productive institutions because of their consistent and systematic investigations in this field. Neural stem cells and mesenchymal stem cells were the most recognized cells for clinical translation.

CONCLUSION

With the growth of publications concerning the role of stem cells in ischemic stroke treatment, bibliometrics helps researchers to get insights of academic collaborations, research trends, and hot topics in the study field.

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.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

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.

Using Dental Pulp Stem Cells for Stroke Therapy

Stroke is a leading cause of permanent disability world-wide, but aside from rehabilitation, there is currently no clinically-proven pharmaceutical or biological agent to improve neurological disability. Cell-based therapies using stem cells, such as dental pulp stem cells, are a promising alternative for treatment of neurological diseases, including stroke. The ischaemic environment in stroke affects multiple cell populations, thus stem cells, which act through cellular and molecular mechanisms, are promising candidates. The most common stem cell population studied in the neurological setting has been mesenchymal stem cells due to their accessibility. However, it is believed that neural stem cells, the resident stem cell of the adult brain, would be most appropriate for brain repair. Using reprogramming strategies, alternative sources of neural stem and progenitor cells have been explored. We postulate that a cell of closer origin to the neural lineage would be a promising candidate for reprogramming and modification towards a neural stem or progenitor cell. One such candidate population is dental pulp stem cells, which reside in the root canal of teeth. This review will focus on the neural potential of dental pulp stem cells and their investigations in the stroke setting to date, and include an overview on the use of different sources of neural stem cells in preclinical studies and clinical trials of stroke.

Tracking Neural Progenitor Cell Migration in the Rodent Brain Using Magnetic Resonance Imaging

The study of neurogenesis and neural progenitor cells (NPCs) is important across the biomedical spectrum, from learning about normal brain development and studying disease to engineering new strategies in regenerative medicine. In adult mammals, NPCs proliferate in two main areas of the brain, the subventricular zone (SVZ) and the subgranular zone, and continue to migrate even after neurogenesis has ceased within the rest of the brain. In healthy animals, NPCs migrate along the rostral migratory stream (RMS) from the SVZ to the olfactory bulb, and in diseased animals, NPCs migrate toward lesions such as stroke and tumors. Here we review how MRI-based cell tracking using iron oxide particles can be used to monitor and quantify NPC migration in the intact rodent brain, in a serial and relatively non-invasive fashion. NPCs can either be labeled directly in situ by injecting particles into the lateral ventricle or RMS, where NPCs can take up particles, or cells can be harvested and labeled in vitro, then injected into the brain. For in situ labeling experiments, the particle type, injection site, and image analysis methods have been optimized and cell migration toward stroke and multiple sclerosis lesions has been investigated. Delivery of labeled exogenous NPCs has allowed imaging of cell migration toward more sites of neuropathology, which may enable new diagnostic and therapeutic opportunities for as-of-yet untreatable neurological diseases.

Exogenous neural stem cell transplantation for cerebral ischemia

Cerebral ischemic injury is the main manifestation of stroke, and its incidence in stroke patients is 70–80%. Although ischemic stroke can be treated with tissue-type plasminogen activator, its time window of effectiveness is narrow. Therefore, the incidence of paralysis, hypoesthesia, aphasia, dysphagia, and cognitive impairment caused by cerebral ischemia is high. Nerve tissue regeneration can promote the recovery of the aforementioned dysfunction. Neural stem cells can participate in the reconstruction of the damaged nervous system and promote the recovery of nervous function during self-repair of damaged brain tissue. Neural stem cell transplantation for ischemic stroke has been a hot topic for more than 10 years. This review discusses the treatment of ischemic stroke with neural stem cells, as well as the mechanisms of their involvement in stroke treatment.

Stand alone or join forces? Stem cell therapy for stroke

INTRODUCTION

Stroke is a major cause of mortality and disability with a narrow therapeutic window. Stem cell therapy may enhance the stroke recovery.

AREAS COVERE

Regenerative medicine via stem cells stands as a novel therapy for stroke. In particular, bone marrow-derived mesenchymal stem cells (MSCs) have neuroprotective and anti-inflammatory properties that improve brain function after stroke. Here, we discuss the safety, efficacy, and mechanism of action underlying the therapeutic effects of bone marrow-derived MSCs. We also examine the discrepant transplant protocols between preclinical studies and clinical trials. Laboratory studies show the safety and efficacy of bone marrow-derived MSCs in stroke models. However, while safe, MSCs remain to be fully evaluated as effective in clinical trials. Furthermore, recognizing the multiple cell death processes associated with stroke, we next discuss the potential therapeutic benefits of a combination therapy. With preliminary results and on-going clinical trials, a careful assessment of dosing, timing, and delivery route regimens will further direct the future of stem cell therapy for neurological disorders, including stroke.

EXPERT OPINION

Bone marrow-derived MSCs appear to be the optimal stem cell source for stroke therapy. Optimizing dosing, timing, and delivery route should guide the clinical application of bone marrow-derived MSCs.

Mesenchymal Stem Cell Therapy in Stroke: A Systematic Review of Literature in Pre-Clinical and Clinical Research

Exogenous stem cell therapy (SCT) has been recognized recently as a promising neuroregenerative strategy to augment recovery in stroke survivors. Mesenchymal stem cells (MSCs) are the primary source of stem cells used in the majority of both pre-clinical and clinical studies in stroke. In the absence of evidence-based guidelines on the use of SCT in stroke patients, understanding the progress of MSC research across published studies will assist researchers and clinicians in better achieving success in translating research. We conducted a systematic review on published literature using MSCs in both pre-clinical studies and clinical trials between 2008 and 2017 using the public databases PubMed and Ovid Medline, and the clinical trial registry ( www.clinicaltrials.gov ). A total of 78 pre-clinical studies and eight clinical studies were identified. While majority of the pre-clinical and clinical studies demonstrated statistically significant effects, the clinical significance of these findings was still unclear. Effect sizes could not be measured mainly due to reporting issues in pre-clinical studies, thus limiting our ability to compare results across studies quantitatively. The overall quality of both pre-clinical and clinical studies was sub-optimal. By conducting a systematic review of both pre-clinical and clinical studies on MSCs therapy in stroke, we assessed the quality of current evidence and identified several issues and gaps in translating animal studies to human trials. Addressing these issues and incorporating changes into future animal studies and human trials may lead to better success of stem cells-based therapeutics in the near future.

Adult Stem Cells for Regenerative Therapy

Cell therapy has been identified as an effective method to regenerate damaged tissue. Adult stem cells, also known as somatic stem cells or resident stem cells, are a rare population of undifferentiated cells, located within a differentiated organ, in a specialized structure, called a niche, which maintains the microenvironments that regulate the growth and development of adult stem cells. The adult stem cells are self-renewing, clonogenic, and multipotent in nature, and their main role is to maintain the tissue homeostasis. They can be activated to proliferate and differentiate into the required type of cells, upon the loss of cells or injury to the tissue. Adult stem cells have been identified in many tissues including blood, intestine, skin, muscle, brain, and heart. Extensive preclinical and clinical studies have demonstrated the structural and functional regeneration capabilities of these adult stem cells, such as bone marrow-derived mononuclear cells, hematopoietic stem cells, mesenchymal stromal/stem cells, resident adult stem cells, induced pluripotent stem cells, and umbilical cord stem cells. In this review, we focus on the human therapies, utilizing adult stem cells for their regenerative capabilities in the treatment of cardiac, brain, pancreatic, and eye disorders.

Mesenchymal stem cell transplantation as an effective treatment strategy for ischemic stroke in Asia: a meta-analysis of controlled trials

Objective

The aim of this study was to evaluate the efficacy and safety of the mesenchymal stem cell (MSC) therapy in patients with ischemic stroke (IS).

Materials and methods

Clinical trials involved in this research were searched from PubMed, Web of Science, Cochrane Library, Embase, Wanfang and CNKI database. Therapeutic effects of MSC therapy were assessed according to National Institutes of Health Stroke Scale (NIHSS), Barthel index (BI), Fugl-Meyer Assessment (FMA) and Functional Independence Measure (FIM), and its safety was evaluated based on adverse events.

Results

This research covered 23 trials including 1,279 IS patients. Based on our analysis, the overall condition of IS patients significantly improved after MSC therapy, indicated by decreased NIHSS and increased BI, FMA and FIM scores. Our analysis also showed that the treatment effects in the MSC transplantation group were superior to those in the control group (routine medication therapy) with statistical significance for NIHSS (1 month after therapy: odds ratio [OR]=-1.92, CI=-3.49 to -0.34, P=0.02; 3 months after therapy: OR=-2.65, CI=-3.40 to -1.90, P<0.00001), BI (1 month after therapy: OR=0.99, CI=0.19-1.79, P=0.02; 6 months after therapy: OR=10.10, CI=3.07-17.14, P=0.005), FMA (3 months after therapy: OR=10.20, CI=3.70-16.70, P=0.002; 6 months after therapy: OR=10.82, CI=6.45-15.18, P<0.00001) and FIM (1 month after therapy: OR=15.61, CI=-0.02 to 31.24, P=0.05; 6 months after therapy: OR=16.56, CI=9.06-24.06, P<0.0001). No serious adverse events were reported during MSC therapy.

Conclusion

MSC therapy is safe and effective in treating IS by improving the neurological deficits, motor function and daily life quality of patients.

Pharmacological approaches promoting stem cell-based therapy following ischemic stroke insults

Stroke can lead to long-term neurological deficits. Adult neurogenesis, the continuous generation of newborn neurons in distinct regions of the brain throughout life, has been considered as one of the appoaches to restore the neurological function following ischemic stroke. However, ischemia-induced spontaneous neurogenesis is not suffcient, thus cell-based therapy, including infusing exogenous stem cells or stimulating endogenous stem cells to help repair of injured brain, has been studied in numerous animal experiments and some pilot clinical trials. While the effects of cell-based therapy on neurological function during recovery remains unproven in randomized controlled trials, pharmacological agents have been administrated to assist the cell-based therapy. In this review, we summarized the limitations of ischemia-induced neurogenesis and stem-cell transplantation, as well as the potential proneuroregenerative effects of drugs that may enhance efficacy of cell-based therapies. Specifically, we discussed drugs that enhance proliferation, migration, differentiation, survival and function connectivity of newborn neurons, which may restore neurobehavioral function and improve outcomes in stroke patients.

A biomaterials approach to influence stem cell fate in injectable cell-based therapies

Background

Numerous stem cell therapies use injection-based administration to deliver high-density cell preparations. However, cell retention rates as low as 1% have been observed within days of transplantation. This study investigated the effects of varying administration and formulation parameters of injection-based administration on cell dose recovery and differentiation fate choice of human mesenchymal stem cells.

Methods

The impact of ejection rate via clinically relevant Hamilton micro-syringes and biomaterial-assisted delivery was investigated. Cell viability, the percentage of cell dose delivered as viable cells, proliferation capacity as well as differentiation behaviour in bipotential media were assessed. Characterisation of the biomaterial-based cell carriers was also carried out.

Results

A significant improvement of in-vitro dose recovery in cells co-ejected with natural biomaterials was observed, with ejections within 2% (w/v) gelatin resulting in 87.5 ± 14% of the cell dose being delivered as viable cells, compared to 32.2 ± 19% of the dose ejected in the commonly used saline vehicle at 10 μl/min. Improvement in cell recovery was not associated with the rheological properties of biomaterials utilised, as suggested by previous studies. The extent of osteogenic differentiation was shown to be substantially altered by choice of ejection rate and cell carrier, despite limited contact time with cells during ejection. Collagen type I and bone-derived extracellular matrix cell carriers yielded significant increases in mineralised matrix deposited at day 21 relative to PBS.

Conclusions

An enhanced understanding of how administration protocols and biomaterials influence cell recovery, differentiation capacity and choice of fate will facilitate the development of improved administration and formulation approaches to achieve higher efficacy in stem cell transplantation.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0789-1) contains supplementary material, which is available to authorized users.

Hydrogels-Assisted Cell Engraftment for Repairing the Stroke-Damaged Brain: Chimera or Reality

The use of advanced biomaterials as a structural and functional support for stem cells-based therapeutic implants has boosted the development of tissue engineering applications in multiple clinical fields. In relation to neurological disorders, we are still far from the clinical reality of restoring normal brain function in neurodegenerative diseases and cerebrovascular disorders. Hydrogel polymers show unique mechanical stiffness properties in the range of living soft tissues such as nervous tissue. Furthermore, the use of these polymers drastically enhances the engraftment of stem cells as well as their capacity to produce and deliver neuroprotective and neuroregenerative factors in the host tissue. Along this article, we review past and current trends in experimental and translational research to understand the opportunities, benefits, and types of tentative hydrogel-based applications for the treatment of cerebral disorders. Although the use of hydrogels for brain disorders has been restricted to the experimental area, the current level of knowledge anticipates an intense development of this field to reach clinics in forthcoming years.

Potential of Stem Cell-Based Therapy for Ischemic Stroke

Ischemic stroke is one of the major health problems worldwide. The only FDA approved anti-thrombotic drug for acute ischemic stroke is the tissue plasminogen activator. Several studies have been devoted to assessing the therapeutic potential of different types of stem cells such as neural stem cells (NSCs), mesenchymal stem cells, embryonic stem cells, and human induced pluripotent stem cell-derived NSCs as treatments for ischemic stroke. The results of these studies are intriguing but many of them have presented conflicting results. Additionally, the mechanism(s) by which engrafted stem/progenitor cells exert their actions are to a large extent unknown. In this review, we will provide a synopsis of different preclinical and clinical studies related to the use of stem cell-based stroke therapy, and explore possible beneficial/detrimental outcomes associated with the use of different types of stem cells. Due to limited/short time window implemented in most of the recorded clinical trials about the use of stem cells as potential therapeutic intervention for stroke, further clinical trials evaluating the efficacy of the intervention in a longer time window after cellular engraftments are still needed.

[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.