Multimodal Approaches for Regenerative Stroke Therapies: Combination of Granulocyte Colony-Stimulating Factor with Bone Marrow Mesenchymal Stem Cells is Not Superior to G-CSF Alone

Grafts of hydrogel-embedded electrically stimulated subventricular stem cells into the stroke cavity improves functional recovery of mice

JOURNAL/nrgr/04.03/01300535-202602000-00039/figure1/v/2025-05-05T160104Z/r/image-tiff The major aim of stroke therapy is to stimulate brain repair and improve behavioral recovery after cerebral ischemia. One option is to stimulate endogenous neurogenesis in the subventricular zone and direct the newly formed neurons to the damaged area. However, only a small percentage of these neurons survive, and many do not reach the damaged area, possibly because the corpus callosum impedes the migration of subventricular zone-derived stem cells into the lesioned cortex. A second major obstacle to stem cell therapy is the strong inflammatory reaction induced by cerebral ischemia, whereby the associated phagocytic activity of brain macrophages removes both therapeutic cells and/or cell-based drug carriers. To address these issues, neurogenesis was electrically stimulated in the subventricular zone, followed by isolation of proliferating cells, including newly formed neurons, which were subsequently mixed with a nutritional hydrogel. This mixture was then transferred to the stroke cavity of day 14 post-stroke mice. We found that the performance of the treated animals improved in behavioral tests, including novel object, open field, hole board, grooming, and "time-to-feel" adhesive tape tests. Furthermore, immunostaining revealed that the stem cell marker nestin, the neuroepithelial marker Mash1, and the immature neuronal marker doublecortin-positive cells survived in the transplanted area for 2 weeks, possibly due to reduced phagocytic activity and supportive angiogenesis. These results clearly indicate that the transplantation of committed subventricular zone stem cells combined with a protective nutritional gel directly into the infarct cavity after the peak of stroke-induced neuroinflammation represents a feasible approach to improve neurorestoration after cerebral ischemia.

Advances in clinical translation of stem cell-based therapy in neurological diseases

Stem cell-based therapies have raised considerable interest to develop regenerative treatment for neurological disorders with high disability. In this review, we focus on recent preclinical and clinical evidence of stem cell therapy in the treatment of degenerative neurological diseases and discuss different cell types, delivery routes and biodistribution of stem cell therapy. In addition, recent advances of mechanistic insights of stem cell therapy, including functional replacement by exogenous cells, immunomodulation and paracrine effects of stem cell therapies are also demonstrated. Finally, we also highlight the adjunction approaches that has been implemented to augment their reparative function, survival and migration to target specific tissue, including stem cell preconditioning, genetical engineering, co-transplantation and combined therapy.

Advancing Post-Stroke Depression Research: Insights from Murine Models and Behavioral Analyses

Post-stroke depression (PSD) represents a significant neuropsychiatric complication that affects between 39% and 52% of stroke survivors, leading to impaired recovery, decreased quality of life, and increased mortality. This comprehensive review synthesizes our current knowledge of PSD, encompassing its epidemiology, risk factors, underlying neurochemical mechanisms, and the existing tools for preclinical investigation, including animal models and behavioral analyses. Despite the high prevalence and severe impact of PSD, challenges persist in accurately modeling its complex symptomatology in preclinical settings, underscoring the need for robust and valid animal models to better understand and treat PSD. This review also highlights the multidimensional nature of PSD, where both biological and psychosocial factors interplay to influence its onset and course. Further, we examine the efficacy and limitations of the current animal models in mimicking the human PSD condition, along with behavioral tests used to evaluate depressive-like behaviors in rodents. This review also sets a new precedent by integrating the latest findings across multidisciplinary studies, thereby offering a unique and comprehensive perspective of existing knowledge. Finally, the development of more sophisticated models that closely replicate the clinical features of PSD is crucial in order to advance translational research and facilitate the discovery of future effective therapies.

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.

The post-stroke young adult brain has limited capacity to re-express the gene expression patterns seen during early postnatal brain development

The developmental origins of the brain's response to injury can play an important role in recovery after a brain lesion. In this study, we investigated whether the ischemic young adult brain can re-express brain plasticity genes that were active during early postnatal development. Differentially expressed genes in the cortex of juvenile post-natal day 3 and the peri-infarcted cortical areas of young, 3-month-old post-stroke rats were identified using fixed-effects modeling within an empirical Bayes framework through condition-specific comparison. To further analyze potential biological processes, upregulated and downregulated genes were assessed for enrichment using GSEA software. The genes showing the highest expression changes were subsequently verified through RT-PCR. Our findings indicate that the adult brain partially recapitulates the gene expression profile observed in the juvenile brain but fails to upregulate many genes and pathways necessary for brain plasticity. Of the upregulated genes in post-stroke brains, specific roles have not been assigned to Apobec1, Cenpf, Ect2, Folr2, Glipr1, Myo1f, and Pttg1. New genes that failed to upregulate in the adult post-stroke brain include Bex4, Cd24, Klhl1/Mrp2, Trim67, and St8sia2. Among the upregulated pathways, the largest change was observed in the KEGG pathway "One carbon pool of folate," which is necessary for cellular proliferation, followed by the KEGG pathway "Antifolate resistance," whose genes mainly encode the family of ABC transporters responsible for the efflux of drugs that have entered the brain. We also noted three less-described downregulated KEGG pathways in experimental models: glycolipid biosynthesis, oxytocin, and cortisol pathways, which could be relevant as therapeutic targets. The limited brain plasticity of the adult brain is illustrated through molecular and histological analysis of the axonal growth factor, KIF4. Collectively, these results strongly suggest that further research is needed to decipher the complex genetic mechanisms that prevent the re-expression of brain plasticity-associated genes in the adult brain.

Beam narrowing test: a motor index of post-stroke motor evaluation in an aged rat model of cerebral ischemia

Each year, 15 million people worldwide suffer from strokes. Consequently, researchers face increasing pressure to develop reliable behavioural tests for assessing functional recovery after a stroke. Our aim was to establish a new motor performance index that can be used to evaluate post-stroke recovery in both young and aged animals. Furthermore, we validate the proposed procedure and recommend the necessary number of animals for experimental stroke studies. Young (n = 20) and aged (n = 27) Sprague-Dawley rats were randomly assigned to receive either sham or stroke surgery. The newly proposed performance index was calculated for the post-stroke acute, subacute and chronic phases. The advantage of using our test over current tests lies in the fact that the newly proposed motor index test evaluates not only the performance of the unaffected side in comparison to the affected one but also assesses overall performance by taking into account speed and coordination. Moreover, it reduces the number of animals needed to achieve a statistical power of 80%. This aspect is particularly crucial when studying aged rodents. Our approach can be used to monitor and assess the effectiveness of stroke therapies in experimental models using aged animals.

Cerebrolysin Use in Patients with Liver Damage-A Translational Study

The treatment of acute life-threatening events in patients suffering from chronic pathologies is problematic, as physicians need to consider multisystemic drug effects. Regarding Cerebrolysin, a Sonic Hedgehog signaling pathway amplifier and one of the few approved neurotrophic treatments for stroke patients, concerns of excessive Hedgehog pathway activation that could accelerate NAFLD progression to cirrhosis seem valid. We investigated stroke patients treated with Cerebrolysin that presented elevated levels of aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT). We also investigated the efficiency of Cerebrolysin in reversing the neurogenesis inhibition within the hippocampus in a mouse model of NAFLD by evaluating behavior and histological outcomes. NeuN, BrdU and Iba1 positive signals in the cortex and hippocampus of the animals were also observed. Clinically, Cerebrolysin improved AST levels in a majority of stroke patients with hepatic damage. The same treatment in an experimental setup was able to reverse anxiety-like behavior in MCD mice, reducing their freezing time from 333.61 ± 21.81 s in MCD animals to 229.17 ± 26.28 in treated ones. The use of Cerebrolysin did not improve short-term memory nor rescued cell multiplication in the hippocampus after MCD food intake. Understanding the neuroprotective and neurotrophic effects that drugs have on NAFLD patients can significantly contribute to a suitable therapeutic approach.

Functional status and its related factors among stroke survivors in rehabilitation departments of hospitals in Shenzhen, China: a cross-sectional study

Background

Many stroke survivors have multiple chronic diseases and complications coupled with various other factors which may affect their functional status. We aimed to investigate the factors associated with poor functional status in hospitalized patients with stroke in Shenzhen, China.

Methods

In this cross-sectional study, four urban hospitals were selected using convenient sampling, and all stroke patients in these four hospitals were included using cluster sampling. The functional status of stroke survivors was evaluated using Longshi Scale. Explanatory variables (factors affecting functional status comprising age, sex, body mass index, smoking, alcohol consumption, complications, and chronic conditions) were collected. Ordinal logistic regression was used to examine which factors were associated with poor functional status.

Results

Stroke survivors with poor functional status accounted for 72.14% and were categorised as the bedridden group based on Longshi scale, 21.67% of patients with moderate functional limitation were categorised as the domestic group, and 6.19% of the patients with mild functional restriction were categorised as the community group. The highest dependence scores were noted for feeding (73.39%), bowel and bladder management (69.74%) and entertainment (69.53%) among the bedridden group, and housework (74.29%) among the domestic group. In the adjusted model, the odds of poor functional status were higher among stroke patients with older age (odds ratio [OR] = 2.39, 95% CI: 1.55–3.80), female sex (OR = 1.73, 95% CI: 1.08–2.77), duration of stroke more than 12 months (OR = 1.94, 95% CI: 1.28–2.95), with pulmonary infection (OR = 10.91, 95% CI: 5.81–20.50), and with deep venous thrombosis (OR = 3.00, 95% CI: 1.28–7.04).

Conclusions

Older adults (age ≥ 60 years) and women were more likely to exhibit poor functional status post-stroke. Pulmonary infection and deep venous thrombosis were related to an increased risk of being dependent on activities of daily living. Therefore, clinical and rehabilitation interventions aimed at preventing or treating these common complications should be addressed to deal with subsequent dysfunction post-stroke. Since all data were obtained in metropolitan areas where the economy is well developed, future studies should be conducted in rural areas and economically less developed cities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02696-0.

G-CSF augments the neuroprotective effect of conditioned medium of dental pulp stem cells against hypoxic neural injury in SH-SY5Y cells

Objective(s):

Dental pulp stem cells (DPSCs) can differentiate into functional neurons and have the potential for cell therapy in neurological diseases. Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein family shown neuroprotective effect in models of nerve damage.

we evaluated the protective effects of G-CSF, conditioned media from DPSCs (DPSCs-CM) and conditioned media from transfected DPSCs with plasmid encoding G-CSF (DPSC-CMT) on SH-SY5Y exposed to CoCl₂ as a model of hypoxia-induced neural damage.

Materials and Methods:

SH-SY5Y exposed to CoCl₂ were treated with DPSCs-CM, G-CSF, simultaneous combination of DPSCs-CM and G-CSF and finally DPSC-CMT. Cell viability and apoptosis were determined by resazurin (or lactate dehydrogenase (LDH) assay alternatively) and propidium iodide (PI) staining. Western blot analysis was performed to detect changes in apoptotic protein levels. The interleukin-6 and interleukin-10 IL6/IL10 levels were measured with Enzyme-Linked Immunosorbent Assay (ELISA).

Results:

DPSCs-CM and G-CSF were able to significantly protect SH-SY5Y against neural cell damage caused by CoCl₂ according to resazurin and LDH analysis. Also, the percentage of apoptotic cells decreased when SH-SY5Y were treated with DPSCs-CM and G-CSF simultaneously. After transfection of DPSCs with G-CSF plasmid, DPSC-CMT could significantly improve the protection. The amount of β-catenin, cleaved PARP and caspase-3 were significantly decreased and the expression of survivin was considerably increased when hypoxic SH-SY5Y treated with DPSCs-CM plus G-CSF according to Western blot. Decreased level of IL-6/IL-10, which exposed to CoCl₂, after treatment with DPSCs-CM indicated the suppression of inflammatory mediators.

Conclusion:

Combination therapy of G-CSF and DPSCs-CM improved the protective activity.

Mesenchymal stromal cell-derived small extracellular vesicles promote neurological recovery and brain remodeling after distal middle cerebral artery occlusion in aged rats

Small extracellular vesicles (sEVs) obtained from mesenchymal stromal cells (MSCs) promote neurological recovery after middle cerebral artery occlusion (MCAO) in young rodents. Ischemic stroke mainly affects aged humans. MSC-sEV effects on stroke recovery in aged rodents had not been assessed. In a head-to-head comparison, we exposed young (4-5 months) and aged (19-20 months) male Sprague-Dawley rats to permanent distal MCAO. At 24 h, 3 and 7 days post-stroke, vehicle or MSC-sEVs (2 × 10⁶ or 2 × 10⁷ MSC equivalents/kg) were intravenously administered. Neurological deficits, ischemic injury, brain inflammatory responses, post-ischemic angiogenesis, and endogenous neurogenesis were evaluated over 28 days. Post-MCAO, aged vehicle-treated rats exhibited more severe motor-coordination deficits evaluated by rotating pole and cylinder tests and larger brain infarcts than young vehicle-treated rats. Although infarct volume was not influenced by MSC-sEVs, sEVs at both doses effectively reduced motor-coordination deficits in young and aged rats. Brain macrophage infiltrates in periinfarct tissue, which were evaluated as marker of a recovery-aversive inflammatory environment, were significantly stronger in aged than young vehicle-treated rats. sEVs reduced brain macrophage infiltrates in aged, but not young rats. The tolerogenic shift in immune balance paved the way for structural brain tissue remodeling. Hence, sEVs at both doses increased periinfarct angiogenesis evaluated by CD31/BrdU immunohistochemistry in young and aged rats, and low-dose sEVs increased neurogenesis in the subventricular zone examined by DCX/BrdU immunohistochemistry. Our study provides robust evidence that MSC-sEVs promote functional neurological recovery and brain tissue remodeling in aged rats post-stroke. This study encourages further proof-of-concept studies in clinic-relevant stroke settings.

The Need for New Biomarkers to Assist with Stroke Prevention and Prediction of Post-Stroke Therapy Based on Plasma-Derived Extracellular Vesicles

The risk of having a stroke event doubles each decade after the age of 55. Therefore, it is of great interest to develop neurorestorative therapies of stroke which occurs mostly in elderly people. However, to date, patients at risk for these sequels of stroke are not duly diagnosed and treated due to the lack of reliable biomarkers. Extracellular vesicles (EVs) are lipid bilayer-delimited particles that are shed by the brain cells and are able to cross the blood–brain barrier and enter the blood stream; thus, they may be used to interrogate molecular and cellular events in the brain damaged area. In this review, we summarize the major molecular and cellular responses of astroglia and neurons to cerebral ischemia and assess their impact on post-stroke recovery and rehabilitation. In particular, we ask if EVs secreted by brain cells are responses to cerebral ischemia, and they may shed new light on the interplay between exosomes-mediated interactions between brain cells and the question of how to exploit it in order to predict the individual course of the disease and to introduce specific preventive or therapeutic strategies. Given these findings, we are left with two options: either to (i) transplant neuronal precursors into the damaged cortical area or (ii) to covert abundantly present proliferating astrocytes in the perilesional area into neurons by using recently developed genetic technologies. However, given the complexity of molecular and cellular responses to cerebral ischemia and our limited capabilities to restore brain structure and function, we are left with only one realistic aim: to invest more in prevention.

Effect of environmental enrichment and isolation on behavioral and histological indices following focal ischemia in old rats

Stroke is a disease of aging. In stroke patients, the enriched group that received stimulating physical, eating, socializing, and group activities resulted in higher activity levels including spending more time on upper limb, communal socializing, listening and iPad activities. While environmental enrichment has been shown to improve the behavioral outcome of stroke in young animals, the effect of an enriched environment on behavioral recuperation and histological markers of cellular proliferation, neuroinflammation, and neurogenesis in old subjects is not known. We used behavioral testing and immunohistochemistry to assess the effect of environment on post-stroke recovery of young and aged rats kept either in isolation or stimulating social, motor, and sensory environment (( +)Env). We provide evidence that post-stroke animals environmental enrichment ( +)Env had a significant positive effect on recovery on the rotating pole, the inclined plane, and the labyrinth test. Old age exerted a small but significant effect on lesion size, which was independent of the environment. Further, a smaller infarct volume positively correlated with better recovery of spatial learning based on positive reinforcement, working and reference memory of young, and to a lesser extent, old animals kept in ( +)Env. Histologically, isolation/impoverishment was associated with an increased number of proliferating inflammatory cells expressing ED1 cells in the peri-infarcted area of old but not young rats. Further, ( +)Env and young age were associated with an increased number of neuroepithelial cells expressing nestin/BrdU as well as beta III tubulin cells in the damaged brain area which correlated with an increased performance on the inclined plane and rotating pole. Finally, ( +)Env and an increased number of neurons expressing doublecortin/BrdU cells exerted a significant effect on performance for working memory and performance on the rotating pole in both age groups. A stimulating social, motor and sensory environment had a limited beneficial effect on behavioral recovery (working memory and rotating pole) after stroke in old rats by reducing neuroinflammation and increasing the number of neuronal precursors expressing doublecortin. Old age however, exerted a small but significant effect on lesion size, which was independent of the environment.

Label-Free Quantitative Proteome Profiling of Cerebrospinal Fluid from a Rat Stroke Model with Stem Cell Therapy

Human adipose-derived mesenchymal stem cells (hAMSCs) are capable of immunomodulation and regeneration after neural injury. For these reasons, hAMSCs have been investigated as a promising stem cell candidate for stroke treatment. However, noninvasive experiments studying the effects of grafted stem cells in the host brain have not yet been reported. Cerebrospinal fluid (CSF), which can be collected without sacrificing the subject, is involved in physiological control of the brain and reflects the pathophysiology of various neurological disorders of the central nervous system (CNS). Following stem cell transplantation in a stroke model, quantitative analysis of CSF proteome changes can potentially reveal the therapeutic effect of stem cells on the host CNS. We examined hAMSC-secreted proteins obtained from serum-free culture medium by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which identified several extracellular matrix proteins, supporting the well-known active paracrine function of hAMSCs. Subsequently, we performed label-free quantitative proteomic analysis on CSF samples from rat stroke models intravenously injected with hAMSC (experimental) or phosphate buffered saline (control). In total, 524 proteins were identified; among them, 125 and 91 proteins were increased and decreased with hAMSC treatment, respectively. Furthermore, gene set enrichment analysis revealed three proteins, 14-3-3 theta, MAG, and neurocan, that showed significant increases in the hAMSC-treated model; these proteins are core members of neurotrophin signaling, nerve growth factor (NGF) signaling, and glycosaminoglycan metabolism, respectively. Subsequent histological and neurologic function experiments validated proliferative neurogenesis in the hAMSC-treated stroke model. We conclude that (i) intravenous injection of hAMSCs can induce neurologic recovery in a rat stroke model and (ii) CSF may reflect the therapeutic effect of hAMSCs. Additionally, proteins as 14-3-3 theta, MAG, and neurocan could be considered as potential CSF biomarkers of neuroregeneration. These CSF proteome profiling results would be utilized as valuable resource in further stroke studies.

p5 Peptide-Loaded Human Adipose-Derived Mesenchymal Stem Cells Promote Neurological Recovery After Focal Cerebral Ischemia in a Rat Model

Adipose-derived mesenchymal stem cells markedly attenuated brain infarct size and improved neurological function in rats. The mechanisms for neuronal cell death have previously been defined in stress states to suggest that an influx of calcium ions into the neurons activates calpain cleavage of p35 into p25 forming a hyperactive complex that induces cell death. Now we report that p5, a 24-residue peptide derived from p35, offers protection to neurons and endothelial cells in vitro. In vivo administration of human adipose-derived mesenchymal stem cells (hADMSCs) loaded with this therapeutic peptide to post-stroke rats had no effect on the infarct volume. Nevertheless, the treatment led to improvement in functional recovery in spatial learning and memory (water maze), bilateral coordination and sensorimotor function (rotating pole), and asymmetry of forelimb usage (cylinder test). However, the treatment may not impact on cutaneous sensitivity (adhesive tape removal test). In addition, the double immunofluorescence with human cell-specific antibodies revealed that the number of surviving transplanted cells was higher in the peri-infarcted area of animals treated with hADMSCs + P5 than that in hADMSC-treated or control animals, concomitant with reduced number of phagocytic, annexin3-positive cells in the peri-infarcted region. However, the combination therapy did not increase the vascular density in the peri-infarcted area after stroke. In conclusion, administration of hADMSC-loaded p5 peptide to post-stroke rats created conditions that supported survival of drug-loaded hADMSCs after cerebral ischemia, suggesting its therapeutic potential in patients with stroke.

Genetic Aspects of Inflammation and Immune Response in Stroke

Genetic determinants play important role in the complex processes of inflammation and immune response in stroke and could be studied in different ways. Inflammation and immunomodulation are associated with repair processes in ischemic stroke, and together with the concept of preconditioning are promising modes of stroke treatment. One of the important aspects to be considered in the recovery of patients after the stroke is a genetic predisposition, which has been studied extensively. Polymorphisms in a number of candidate genes, such as IL-6, BDNF, COX2, CYPC19, and GPIIIa could be associated with stroke outcome and recovery. Recent GWAS studies pointed to the variant in genesPATJ and LOC as new genetic markers of long term outcome. Epigenetic regulation of immune response in stroke is also important, with mechanisms of histone modifications, DNA methylation, and activity of non-coding RNAs. These complex processes are changing from acute phase over the repair to establishing homeostasis or to provoke exaggerated reaction and death. Pharmacogenetics and pharmacogenomics of stroke cures might also be evaluated in the context of immuno-inflammation and brain plasticity. Potential novel genetic treatment modalities are challenged but still in the early phase of the investigation.

Animal models of cerebral ischemia: A review

Stroke seriously threatens human health because of its characteristics of high morbidity, disability, recurrence, and mortality, thus representing a heavy financial and mental burden to affected families and society. Many preclinical effective drugs end in clinical-translation failure. Animal models are an important approach for studying diseases and drug effects, and play a central role in biomedical research. Some details about animal models of cerebral ischemia have not been published, such as left-/right-sided lesions or permanent cerebral ischemia/cerebral ischemia-reperfusion. In this review, ischemia in the left- and right-hemisphere in patients with clinical stroke and preclinical studies were compared for the first time, as were the mechanisms of permanent cerebral ischemia and cerebral ischemia-reperfusion in different phases of the disease. The results showed that stroke in the left hemisphere was more common in clinical patients, and that most patients with stroke failed to achieve successful recanalization. Significant differences were detected between permanent cerebral ischemia and cerebral ischemia-reperfusion models in the early, subacute, and recovery phases. Therefore, it is recommended that, with the exception of the determined experimental purpose or drug mechanism, left-sided permanent cerebral ischemia animal models should be prioritized, as they would be more in line with the clinical scenario and would promote clinical translation. In addition, other details regarding the preoperative management, surgical procedures, and postoperative care of these animals are provided, to help establish a precise, effective, and reproducible model of cerebral ischemia model and establish a reference for researchers in this field.

Combination therapy of the granulocyte colony stimulating factor and intravenous lipid emulsion protect the hippocampus after global ischemia in rat: focusing on CA1 region

Brain stroke is one of the causes of human death and disability worldwide. Global ischemia results in the accumulation of free radicals in the neurons. It leads to histologically brain damage. The CA1 region of the hippocampus is a sensitive area for free radicals. This study investigated the combined therapy of the Granulocyte colony stimulating factor (G-CSF) and the Intravenous lipid emulsion (ILE). These neuroprotective agents play a role in the regeneration of neurons. They improve the learning ability and memory in rats induced global ischemia. We divided 35 rats into five groups. The groups were sham group, ischemia group, G-CSF group, ILE group, and G-CSF plus ILE group. Ischemia was induced by occlusion of the bilateral common carotid about 10 min. The drugs applied on days 1, 3 and 7. The treated groups received subcutaneous injection of 20 μg/kg G-CSF and intravenous injection of 5 ml/kg ILE. After two weeks, the memory and learning ability of the rats was evaluated by the shuttle box. Hematoxylin and Eosin and Nissl and TUNEL stainings were used to determine the necrosis, normal and apoptotic cells. The combined therapy increased normal cells compared to the ischemia group. They decreased the number of necrotic and apoptosis cells in other groups. The combined group improved the passive avoidance test compared to the other groups. The combination therapy of G-CSF plus ILE is more effective than each alone.

Neuro-regenerative potential of dental stem cells: a concise review

This review will summarize the research information regarding the regenerative potential of dental stem cells for the treatment of neurodegenerative disorders. As compared to existing treatment modalities, the stem cell therapy seems promising, and accumulating evidences about the differentiation of stem cells into various lineages are proving it. The incidence of neurodegenerative diseases such as Alzheimer's, Parkinson's, stroke, and peripheral neuropathy is increasing due to the rise in life expectancies of people which have put a huge burden on economies. Finding a promising treatment could benefit not only the patients but also the communities. Dental stem cells hold a great potential to differentiate into neuronal cells. Many studies have reported the differentiation potential of the dental stem cells with the presence of neuronal lineage markers. In this review, we conferred how the use of dental stem cells can benefit the above-mentioned bedridden diseases.

Ageing as a risk factor for cerebral ischemia: Underlying mechanisms and therapy in animal models and in the clinic

Age is the only one non-modifiable risk of cerebral ischemia. Advances in stroke medicine and behavioral adaptation to stroke risk factors and comorbidities was successful in decreasing stroke incidence and increasing the number of stroke survivors in western societies. Comorbidities aggravates the outcome after cerebral ischemia. However, due to the increased in number of elderly, the incidence of stroke has increased again paralleled by an increase in the number of stroke survivors, many with severe disabilities, that has led to an increased economic and social burden in society. Animal models of stroke often ignore age and comorbidities frequently associated with senescence. This might explain why drugs working nicely in animal models fail to show efficacy in stroke survivors. Since stroke afflicts mostly the elderly comorbid patients, it is highly desirable to test the efficacy of stroke therapies in an appropriate animal stroke model. Therefore, in this review, we make parallels between animal models of stroke und clinical data and summarize the impact of ageing and age-related comorbidities on stroke outcome.

Electric Stimulation of Neurogenesis Improves Behavioral Recovery After Focal Ischemia in Aged Rats

The major aim of stroke therapies is to stimulate brain repair and to improve behavioral recuperation after cerebral ischemia. Despite remarkable advances in cell therapy for stroke, stem cell-based tissue replacement has not been achieved yet stimulating the search for alternative strategies for brain self-repair using the neurogenic zones of the brain, the dentate gyrus and the subventricular zone (SVZ). However, during aging, the potential of the hippocampus and the SVZ to generate new neuronal precursors, declines. We hypothesized that electrically stimulation of endogenous neurogenesis in aged rats could increase the odds of brain self-repair and improve behavioral recuperation after focal ischemia. Following stroke in aged animals, the rats were subjected to two sessions of electrical non-convulsive stimulation using ear-clip electrodes, at 7- and 24 days after MCAO. Animal were sacrificed after 48 days. We report that electrical stimulation (ES) stimulation of post-stroke aged rats led to an improved functional recovery of spatial long-term memory (T-maze) but not on the rotating pole or the inclined plane, both tests requiring complex sensorimotor skills. Surprisingly, ES had a detrimental effect on the asymmetric sensorimotor deficit. Histologically, there was a robust increase in the number of doublecortin-positive cells in the dentate gyrus and SVZ of the infarcted hemisphere and the presence of a considerable number of neurons expressing tubulin beta III in the infarcted area. Among the gene that were unique to ES, we noted increases in the expression of seizure related 6 homolog like which is one of the physiological substrate of the β-secretase BACE1 involved in the pathophysiology of the Alzheimer’s disease and Igfbp3 and BDNF receptor mRNAs which has been shown to have a neuroprotective effect after cerebral ischemia. However, ES was associated with a long-term down regulation of cortical gene expression after stroke in aged rats suggesting that gene expression in the peri-infarcted cortical area may not be related to electrical stimulation induced-neurogenesis in the subventricular zone and hippocampus.

Targeting Oxidative Stress and Inflammation to Prevent Ischemia-Reperfusion Injury

The cerebral ischemia injury can result in neuronal death and/or functional impairment, which leads to further damage and dysfunction after recovery of blood supply. Cerebral ischemia/reperfusion injury (CIRI) often causes irreversible brain damage and neuronal injury and death, which involves many complex pathological processes including oxidative stress, amino acid toxicity, the release of endogenous substances, inflammation and apoptosis. Oxidative stress and inflammation are interactive and play critical roles in ischemia/reperfusion injury in the brain. Oxidative stress is important in the pathological process of ischemic stroke and is critical for the cascade development of ischemic injury. Oxidative stress is caused by reactive oxygen species (ROS) during cerebral ischemia and is more likely to lead to cell death and ultimately brain death after reperfusion. During reperfusion especially, superoxide anion free radicals, hydroxyl free radicals, and nitric oxide (NO) are produced, which can cause lipid peroxidation, inflammation and cell apoptosis. Inflammation alters the balance between pro-inflammatory and anti-inflammatory factors in cerebral ischemic injury. Inflammatory factors can therefore stimulate or exacerbate inflammation and aggravate ischemic injury. Neuroprotective therapies for various stages of the cerebral ischemia cascade response have received widespread attention. At present, neuroprotective drugs mainly include free radical scavengers, anti-inflammatory agents, and anti-apoptotic agents. However, the molecular mechanisms of the interaction between oxidative stress and inflammation, and their interplay with different types of programmed cell death in ischemia/reperfusion injury are unclear. The development of a suitable method for combination therapy has become a hot topic.

Recent Advances in Mono- and Combined Stem Cell Therapies of Stroke in Animal Models and Humans

Following the failure of acute neuroprotection therapies, major efforts are currently made worldwide to promote neurological recovery and brain plasticity in the subacute and post-acute phases of stroke. Currently, there is hope that stroke recovery might be promoted by cell-based therapies. The field of stem cell therapy for cerebral ischemia has made significant progress in the last five years. A variety of stem cells have been tested in animal models and humans including adipose stem cells, human umbilical cord blood-derived mesenchymal stem cells, human amnion epithelial cells, human placenta amniotic membrane-derived mesenchymal stem cells, adult human pluripotent-like olfactory stem cells, human bone marrow endothelial progenitor cells, electrically-stimulated human neuronal progenitor cells, or induced pluripotent stem cells (iPSCs) of human origin. Combination therapies in animal models include a mix of two or more therapeutic factors consisting of bone marrow stromal cells, exercise and thyroid hormones, endothelial progenitor cells overexpressing the chemokine CXCL12. Mechanisms underlying the beneficial effects of transplanted cells include the “bystander” effects, paracrine mechanisms, or extracellular vesicles-mediated restorative effects. Mitochondria transfer also appears to be a powerful strategy for regenerative processes. Studies in humans are currently limited to a small number of studies using autologous stem cells mainly aimed to assess tolerability and side-effects of human stem cells in the clinic.

Successes and Hurdles in Stem Cells Application and Production for Brain Transplantation

Brain regenerative strategies through the transplantation of stem cells hold the potential to promote functional rescue of brain lesions caused either by trauma or neurodegenerative diseases. Most of the positive modulations fostered by stem cells are fueled by bystander effects, namely increase of neurotrophic factors levels and reduction of neuroinflammation. Nevertheless, the ultimate goal of cell therapies is to promote cell replacement. Therefore, the ability of stem cells to migrate and differentiate into neurons that later become integrated into the host neuronal network replacing the lost neurons has also been largely explored. However, as most of the preclinical studies demonstrate, there is a small functional integration of graft-derived neurons into host neuronal circuits. Thus, it is mandatory to better study the whole brain cell therapy approach in order to understand what should be better comprehended concerning graft-derived neuronal and glial cells migration and integration before we can expect these therapies to be ready as a viable solution for brain disorder treatment. Therefore, this review discusses the positive mechanisms triggered by cell transplantation into the brain, the limitations of adult brain plasticity that might interfere with the neuroregeneration process, as well as some strategies tested to overcome some of these limitations. It also considers the efforts that have been made by the regulatory authorities to lead to better standardization of preclinical and clinical studies in this field in order to reduce the heterogeneity of the obtained results.

Intracortical Administration of the Complement C3 Receptor Antagonist Trifluoroacetate Modulates Microglia Reaction after Brain Injury

Worldwide, millions of individuals suffer an ischemic stroke each year, causing major disability, especially in the elderly, where stroke is the number one cause of disability. However, to date, no effective therapy exists that targets the functional recovery after stroke. After necrosis, neuroinflammation is a common feature of the acute stroke and a major obstacle to tissue restoration. In the lesioned area, the dying neurons release chemotactic signals, such as fractalkine/CX3CL1, which evoke “eat-me” signals that are recognized by microglia expressing complement C3a receptor (C3aR), resulting in phagocytosis of the dying but still viable neurons, known as secondary phagocytosis. Using a mouse model of stroke and two-photon microscopy, we aimed to attenuate poststroke phagocytosis of the dying but still viable neurons by using SB 290157, an antagonist of C3aR. We found that intracortical administration of SB 290157 reduced the number of inflammatory microglial cells expressing ED1 and Iba1 antigens at the lesion site. We could show, in vivo, that two days after a needle-induced cortical lesion there were less microglial cells present around the injury site, displaying less high-order branches and an increase in the lower order ones, suggesting an attenuated phagocytic phenotype in treated animals as compared with controls. We conclude that the C3aR antagonist, SB 290157, may be used in the future to limit the neuronal death by limiting secondary phagocytosis after stroke.

Drug-like delivery methods of stem cells as biologics for stroke

Introduction: Stem cell therapy is an experimental treatment for brain disorders. Although a cellular product, stem cells can be classified as biologics based on the cells' secretion of therapeutic substances. Treatment with stem cell biologics may appeal to stroke because of the secondary cell death mechanisms, especially neuroinflammation, that are rampant from the onset and remain elevated during the progressive phase of the disease requiring multi-pronged biological targets to effectively abrogate the neurodegenerative pathology. However, the optimal delivery methods, among other logistical approaches (i.e. cell doses and timing of intervention), for stem cell therapy will need to be refined before stem cell biologics can be successfully utilized for stroke in large scale clinical trials. Areas covered: In this review, we discuss how the innate qualities of stem cells characterize them as biologics, how stem cell transplantation may be an ideal treatment for stroke, and the various routes of stem cell administration that have been employed in various preclinical and clinical investigations. Expert opinion: There is a need to optimize the delivery of stem cell biologics for stroke in order to guide the safe and effective translation of this therapy from the laboratory to the clinic.

Genetic conversion of proliferative astroglia into neurons after cerebral ischemia: a new therapeutic tool for the aged brain?

Ischemic stroke represents the 2nd leading cause of death worldwide and the leading cause for long-term disabilities, for which no cure exists. After stroke, neurons are frequently lost in the infarct core. On the other hand, other cells such as astrocytes become reactive and proliferative, disrupting the neurovascular unit in the lesioned area, especially in the aged brain. Therefore, restoring the balance between neurons and nonneuronal cells within the perilesional area is crucial for post stroke recovery. In addition, the aged post stroke brain mounts a fulminant proliferative astroglial response leading to the buildup of gliotic scars that prevent neural regeneration. Therefore, "melting" glial scars has been attempted for decades, albeit with little success. Alternative strategies include transforming inhibitory gliotic tissue into an environment conducive to neuronal regeneration and axonal growth by genetic conversion of astrocytes into neurons. The latter idea has gained momentum following the discovery that in vivo direct lineage reprogramming in the adult mammalian brain is a feasible strategy for reprogramming nonneuronal cells into neurons. This exciting new technology emerged as a new approach to circumvent cell transplantation for stroke therapy. However, the potential of this new methodology has not been yet tested to improve restoration of structure and function in the hostile environment caused by the fulminant inflammatory reaction in the brains of aged animals.

World-Wide Efficacy of Bone Marrow Derived Mesenchymal Stromal Cells in Preclinical Ischemic Stroke Models: Systematic Review and Meta-Analysis

Background: Following extensive, positive results in pre-clinical experiments, Bone Marrow Derived-Mesenchymal Stromal Cells (BM-MSCs) are now being tested as a novel therapy for ischemic stroke in ongoing clinical trials. However, multiple critical questions relating to their translational application remain to be clarified. We performed a comprehensive, systematic review and meta-analysis of pre-clinical studies to evaluate the efficacy of BM-MSCs on functional outcomes after ischemic stroke, as well as the independent role of translational factors on their effect size.

Methods: We systematically reviewed the literature and identified articles using BM-MSCs in animal models of focal ischemic stroke. After abstraction of all relevant data, we performed a meta-analysis to estimate the combined effect size of behavioral endpoints after BM-MSC administration. To describe the effect size across many behavioral outcomes, we divided these outcomes into four categories: (1) Composite scores, (2) Motor Tests, (3) Sensorimotor Tests, and (4) Cognitive Tests. We also performed a meta-regression analysis for measuring the effect of individual characteristics of BM-MSC administration on the effect size.

Results: Our results from 141 articles indicate a significant beneficial effect on composite, motor, and sensorimotor outcomes after treatment with BM-MSCs compared to control groups. We found no major differences in treatment effect based on delivery route, dose, fresh vs. frozen preparation, or passage number. There were no consistent findings supporting a difference in treatment effect based on time windows from acute periods (0–6 h) vs. later windows (2–7 days). Furthermore, these positive treatment effects on functional outcome were consistent across different labs in different parts of the world as well as over the last 18 years. There was a negative correlation between publication year and impact factor.

Conclusions: Our results show worldwide efficacy of BM-MSCs in improving functional outcomes in pre-clinical animal models of stroke and support testing these cells in clinical trials in various ranges of time windows using different delivery routes. The continued growing number of publications showing functional benefit of BM-MSCs are now adding limited value to an oversaturated literature spanning 18 years. Researchers should focus on identifying definitive mechanisms on how BM-MSCs lead to benefit in stroke models.

Cell-Based Therapies for Stroke: Promising Solution or Dead End? Mesenchymal Stem Cells and Comorbidities in Preclinical Stroke Research

Stroke is a major health problem worldwide. It has been estimated that 90% of the population attributable risk of stroke is due to risk factors such as aging, hypertension, hyperglycemia, diabetes mellitus and obesity, among others. However, most animal models of stroke use predominantly healthy and young animals. These models ignore the main comorbidities associated with cerebrovascular disease, which could be one explanation for the unsuccessful bench-to-bedside translation of protective and regenerative strategies by not taking the patient's situation into account. This lack of success makes it important to incorporate comorbidities into animal models of stroke in order to study the effects of the various therapeutic strategies tested. Regarding cell therapy, the administration of stem cells in the acute and chronic phases has been shown to be safe and effective in experimental animal models of stroke. This review aims to show the results of studies with promising new therapeutic strategies such as mesenchymal stem cells, which are being tested in preclinical models of stroke associated with comorbidities and in elderly animals.

Multicellular Crosstalk Between Exosomes and the Neurovascular Unit After Cerebral Ischemia. Therapeutic Implications

Restorative strategies after stroke are focused on the remodeling of cerebral endothelial cells and brain parenchymal cells. The latter, i.e., neurons, neural precursor cells and glial cells, synergistically interact with endothelial cells in the ischemic brain, providing a neurovascular unit (NVU) remodeling that can be used as target for stroke therapies. Intercellular communication and signaling within the NVU, the multicellular brain-vessel-blood interface, including its highly selective blood-brain barrier, are fundamental to the central nervous system homeostasis and function. Emerging research designates cell-derived extracellular vesicles and especially the nano-sized exosomes, as a complex mean of cell-to-cell communication, with potential use for clinical applications. Through their richness in active molecules and biological information (e.g., proteins, lipids, genetic material), exosomes contribute to intercellular signaling, a condition particularly required in the central nervous system. Cerebral endothelial cells, perivascular astrocytes, pericytes, microglia and neurons, all part of the NVU, have been shown to release and uptake exosomes. Also, exosomes cross the blood-brain and blood-cerebrospinal fluid barriers, allowing communication between periphery and brain, in normal and disease conditions. As such exosomes might be a powerful diagnostic tool and a promising therapeutic shuttle of natural nanoparticles, but also a means of disease spreading (e.g., immune system modulation, pro-inflammatory action, propagation of neurodegenerative factors). This review highlights the importance of exosomes in mediating the intercellular crosstalk within the NVU and reveals the restorative therapeutic potential of exosomes harvested from multipotent mesenchymal stem cells in ischemic stroke, a frequent neurologic condition lacking an efficient therapy.

Mechanisms underlying dental-derived stem cell-mediated neurorestoration in neurodegenerative disorders

BACKGROUND

Neurodegenerative disorders have a complex pathology and are characterized by a progressive loss of neuronal architecture in the brain or spinal cord. Neuroprotective agents have demonstrated promising results at the preclinical stage, but this has not been confirmed at the clinical stage. Thus far, no neuroprotective drug that can prevent neuronal degeneration in patients with neurodegenerative disorders is available.

MAIN BODY

Recent studies have focused on neurorestorative measures, such as cell-based therapy, rather than neuroprotective treatment. The utility of cell-based approaches for the treatment of neurodegenerative disorders has been explored extensively, and the results have been somewhat promising with regard to reversing the outcome. Because of their neural crest origin, ease of harvest, accessibility, ethical suitability, and potential to differentiate into the neurogenic lineage, dental-derived stem cells (DSCs) have become an attractive source for cell-based neurorestoration therapies. In the present review, we summarize the possible use of DSC-based neurorestoration therapy as an alternative treatment for neurodegenerative disorders, with a particular emphasis on the mechanism underlying recovery in neurodegenerative disorders.

CONCLUSION

Transplantation research in neurodegenerative diseases should aim to understand the mechanism providing benefits both at the molecular and functional level. Due to their ease of accessibility, plasticity, and ethical suitability, DSCs hold promise to overcome the existing challenges in the field of neurodegeneration through multiple mechanisms, such as cell replacement, bystander effect, vasculogenesis, synaptogenesis, immunomodulation, and by inhibiting apoptosis.

Transplantation of human bone marrow stem cells into symptomatic ALS mice enhances structural and functional blood-spinal cord barrier repair

Accumulating evidence shows alterations in the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) in ALS patients and in animal models of disease, mainly by endothelial cell (EC) damage. Repair of the altered barrier in the CNS by replacement of ECs via cell transplantation may be a new therapeutic approach for ALS. Recently, we demonstrated positive effects towards BSCB repair by intravenous administration of unmodified human bone marrow CD34⁺ (hBM34⁺) cells at different doses into symptomatic ALS mice. However, particular benefits of these transplanted cells on microvascular integrity in symptomatic ALS mice are still unclear. The aim of the present study was to determine the structural and functional spinal cord capillary integrity in symptomatic ALS mice after intravenous administration of hBM34⁺ cells. The G93A mice at 13 weeks of age intravenously received one of three different cell doses (5 × 10⁴, 5 × 10⁵, or 1 × 10⁶) and were euthanized at 17 weeks of age (4 weeks post-transplant). Control groups were media-treated and non-carrier mutant SOD1 gene mice. Capillary ultrastructural (electron microscopy), immunohistochemical (laminin and HuNu), and histological (myelin and capillary density) analyses were performed in the cervical and lumbar spinal cords. Capillary permeability in the spinal cords was determined by Evans Blue (EB) injection. Results showed significant restoration of ultrastructural capillary morphology, improvement of basement membrane integrity, enhancement of axonal myelin coherence, and stabilization of capillary density in the spinal cords primarily of ALS mice receiving the high dose of 1 × 10⁶ cells. Moreover, substantial reduction of parenchymal EB levels was determined in these mice, confirming our previous results on capillary permeability. Additionally, transplanted cells were detected in blood smears of sacrificed late symptomatic mice by HuNu marker. Altogether, these results provide novel evidence that unmodified bone marrow hematopoietic stem cell treatment at optimal dose might be beneficial for structural and functional repair of the damaged BSCB in advanced stage of ALS, potentially resulting in delayed disease progression by increased motor neuron survival.

Extension of Tissue Plasminogen Activator Treatment Window by Granulocyte-Colony Stimulating Factor in a Thromboembolic Rat Model of Stroke

When given beyond 4.5 h of stroke onset, tissue plasminogen activator (tPA) induces deleterious side effects in the ischemic brain, notably, hemorrhagic transformation (HT). We examined the efficacy of granulocyte-colony stimulating factor (G-CSF) in reducing delayed tPA-induced HT, cerebral infarction, and neurological deficits in a thromboembolic (TE) stroke model, and whether the effects of G-CSF were sustained for longer periods of recovery. After stroke induction, rats were given intravenous saline (control), tPA (10 mg/kg), or G-CSF (300 μg/kg) + tPA 6 h after stroke. We found that G-CSF reduced delayed tPA-associated HT by 47%, decreased infarct volumes by 33%, and improved motor and neurological deficits by 15% and 25%, respectively. It also prevented delayed tPA treatment-induced mortality by 46%. Immunohistochemistry showed 1.5- and 1.8-fold enrichment of the endothelial progenitor cell (EPC) markers CD34+ and VEGFR2 in the ischemic cortex and striatum, respectively, and 1.7- and 2.8-fold increases in the expression of the vasculogenesis marker von Willebrand factor (vWF) in the ischemic cortex and striatum, respectively, in G-CSF-treated rats compared with tPA-treated animals. Flow cytometry revealed increased mobilization of CD34+ cells in the peripheral blood of rats given G-CSF. These results corroborate the efficacy of G-CSF in enhancing the therapeutic time window of tPA for stroke treatment via EPC mobilization and enhancement of vasculogenesis.

Enhancing endogenous capacity to repair a stroke-damaged brain: An evolving field for stroke research

Stroke represents a severe medical condition that causes stroke survivors to suffer from long-term and even lifelong disability. Over the past several decades, a vast majority of stroke research targets neuroprotection in the acute phase, while little work has been done to enhance stroke recovery at the later stage. Through reviewing current understanding of brain plasticity, stroke pathology, and emerging preclinical and clinical restorative approaches, this review aims to provide new insights to advance the research field for stroke recovery. Lifelong brain plasticity offers the long-lasting possibility to repair a stroke-damaged brain. Stroke impairs the structural and functional integrity of entire brain networks; the restorative approaches containing multi-components have great potential to maximize stroke recovery by rebuilding and normalizing the stroke-disrupted entire brain networks and brain functioning. The restorative window for stroke recovery is much longer than previously thought. The optimal time for brain repair appears to be at later stage of stroke rather than the earlier stage. It is expected that these new insights will advance our understanding of stroke recovery and assist in developing the next generation of restorative approaches for enhancing brain repair after stroke.

Cellular and Molecular Mechanisms Underlying Non-Pharmaceutical Ischemic Stroke Therapy in Aged Subjects

The incidence of ischemic stroke in humans increases exponentially above 70 years both in men and women. Comorbidities like diabetes, arterial hypertension or co-morbidity factors such as hypercholesterolemia, obesity and body fat distribution as well as fat-rich diet and physical inactivity are common in elderly persons and are associated with higher risk of stroke, increased mortality and disability. Obesity could represent a state of chronic inflammation that can be prevented to some extent by non-pharmaceutical interventions such as calorie restriction and hypothermia. Indeed, recent results suggest that H₂S-induced hypothermia in aged, overweight rats could have a higher probability of success in treating stroke as compared to other monotherapies, by reducing post-stroke brain inflammation. Likewise, it was recently reported that weight reduction prior to stroke, in aged, overweight rats induced by caloric restriction, led to an early re-gain of weight and a significant improvement in recovery of complex sensorimotor skills, cutaneous sensitivity, or spatial memory.

CONCLUSION

animal models of stroke done in young animals ignore age-associated comorbidities and may explain, at least in part, the unsuccessful bench-to-bedside translation of neuroprotective strategies for ischemic stroke in aged subjects.

Therapeutic potential of mesenchymal stromal cells for hypoxic ischemic encephalopathy: A systematic review and meta-analysis of preclinical studies

INTRODUCTION

Neonatal hypoxic ischemic encephalopathy (HIE) is a devastating neurologic condition with high mortality rates and long-term complications for surviving infants. Mesenchymal stem/stromal cells (MSCs) have emerged as novel therapeutic agents with promising results in experimental studies of HIE. The purpose of this study is to (a) methodically review the current preclinical literature describing MSC therapy in animal models of HIE, (b) quantify the effect size in regards to functional neurologic outcome, and (c) identify research gaps/limitations that should be addressed prior to future preclinical and clinical studies.

METHODS

Adhering to the Systematic Review Protocol for Animal Intervention Studies, a systematic search of English articles was performed. Eligible studies were identified and data regarding study characteristics and outcome measures was extracted. After quality assessment, meta-analysis and meta-regression were performed to generate random effect size using standardized mean difference (SMD). Funnel plots and Egger's tests were utilized to evaluate for the presence of publication bias.

RESULTS

A total of 19 studies met inclusion in the current systematic review. Meta-analysis revealed that MSCs have a significant positive effect on neurobehavioral outcome following HIE injury. Sensorimotor function was improved by 2.25 SMD (95% CI; 2.04-2.46) in cylinder rearing and 2.97 SMD (95% CI; 2.56-3.38) in rotarod. Likewise, cognitive function was improved by 2.76 SMD (95% CI; 2.53-2.98) on the water maze and 2.97 SMD (95% CI; 2.58-3.35) in object recognition. Stratification demonstrated an increased effect size depending on various study characteristics.

CONCLUSIONS

Overall, these results suggest a promising role for MSCs in preclinical studies of HIE. MSC treatment demonstrates improved functional outcomes that are encouraging for future translational studies. While risk of bias and heterogeneity limited the strength of our meta-analysis, our results are consistent with those seen in this field of research.

Caloric restriction stabilizes body weight and accelerates behavioral recovery in aged rats after focal ischemia

Obesity and hyperinsulinemia are risk factors for stroke. We tested the hypothesis that caloric restriction, which reduces the incidence of age‐related obesity and metabolic syndrome, may represent an efficient and cost‐effective strategy for preventing stroke and its devastating consequences. To this end, we placed aged, obese Sprague‐Dawley aged rats on a calorie‐restricted diet for 8 weeks prior to the experimental infarction. Stroke in this animal model caused a progressive decrease in weight that reached a minimum at day 6 for the young rats, and at day 10 for the aged, ad libitum‐fed rats. However, in aged animals that were calorie‐restricted prior to stroke, body weight did not decrease after stroke, but we noted accelerated body weight gain shortly thereafter starting at day 5 poststroke. Moreover, calorie‐restricted aged animals showed improved behavioral recovery in tasks requiring complex sensorimotor skills, or in tasks requiring cutaneous sensitivity and sensorimotor integration or spatial memory. Likewise, calorie‐restricted aged rats showed significant poststroke increases in serum glucose, insulin, and IGF1 levels, as well as CR‐specific changes in the expression of gene transcripts involved in glycogen metabolism, IGF signaling, apoptosis, arteriogenesis, and hypoxia. In conclusion, our study shows that recovery from stroke is enhanced in aged rats by a dietary regimen that reduces body weight prior to infarct.

Granulocyte-colony stimulating factor and umbilical cord blood cell transplantation: Synergistic therapies for the treatment of traumatic brain injury

Traumatic brain injury (TBI) is now characterized as a progressive, degenerative disease and continues to stand as a prevalent cause of death and disability. The pathophysiology of TBI is complex, with a variety of secondary cell death pathways occurring which may persist chronically following the initial cerebral insult. Current therapeutic options for TBI are minimal, with surgical intervention or rehabilitation therapy existing as the only viable treatments. Considering the success of stem-cell therapies in various other neurological diseases, their use has been proposed as a potential potent therapy for patients suffering TBI. Moreover, stem cells are highly amenable to adjunctive use with other therapies, providing an opportunity to overcome the inherent limitations of using a single therapeutic agent. Our research has verified this additive potential by demonstrating the efficacy of co-delivering human umbilical cord blood (hUCB) cells with granulocyte-colony stimulating factor (G-CSF) in a murine model of TBI, providing encouraging results which support the potential of this approach to treat patients suffering from TBI. These findings justify ongoing research toward uncovering the mechanisms which underlie the functional improvements exhibited by hUCB + G-CSF combination therapy, thereby facilitating its safe and effect transition into the clinic. This paper is a review article. Referred literature in this paper has been listed in the reference section. The datasets supporting the conclusions of this article are available online by searching various databases, including PubMed. Some original points in this article come from the laboratory practice in our research center and the authors’ experiences.

Integrin α4 Overexpression on Rat Mesenchymal Stem Cells Enhances Transmigration and Reduces Cerebral Embolism After Intracarotid Injection

BACKGROUND AND PURPOSE

Very late antigen-4 (integrin α4β1)/vascular cell adhesion molecule-1 mediates leukocyte trafficking and transendothelial migration after stroke. Mesenchymal stem cells (MSCs) typically express integrin β1 but insufficient ITGA4 (integrin α4), which limits their homing after intravascular transplantation. We tested whether ITGA4 overexpression on MSCs increases cerebral homing after intracarotid transplantation and reduces MSC-borne cerebral embolism.

METHODS

Rat MSCs were lentivirally transduced to overexpress ITGA4. In vitro transendothelial migration was assessed using a Boyden chamber assay. Male Wistar rats intracarotidly received 0.5×10⁶ control or modified MSCs 24 hours after sham or stroke surgery. In vivo behavior of MSCs in the cerebral vasculature was observed by intravital microscopy and single-photon emission computed tomography for up to 72 hours.

RESULTS

Transendothelial migration of ITGA4-overexpressing MSCs was increased in vitro. MSCs were passively entrapped in microvessels in vivo and occasionally formed large cell aggregates causing local blood flow interruptions. MSCs were rarely found in perivascular niches or parenchyma at 72 hours post-transplantation, but ITGA4 overexpression significantly decreased cell aggregation and ameliorated the evoked cerebral embolism in stroke rats.

CONCLUSIONS

ITGA4 overexpression on MSCs enhances transendothelial migration in vitro, but not in vivo, although it improves safety after intracarotid transplantation into stroke rats.

Effects of the combined treatment of bone marrow stromal cells with mild exercise and thyroid hormone on brain damage and apoptosis in a mouse focal cerebral ischemia model

This study examined whether post-stroke bone marrow stromal cells (BMSCs) therapy combined with exercise (EX) and/or thyroid hormone (TH) could reduce brain damage in an experimental ischemic stroke in mice. Focal cerebral ischemia was induced under Laser Doppler Flowmetry (LDF) guide by 45 min of middle cerebral artery occlusion (MCAO), followed by 7 days of reperfusion in albino mice. BMSCs were injected into the right cerebral ventricle 24 h after MCAO, followed by daily injection of T3 (20 μg/100 g weight S.C) and 6 days of running on a treadmill. Infarct size, neurobehavioral test, TUNEL and BrdU positive cells were evaluated at 7 days after MCAO. Treatment with BMSCs and mild EX alone significantly reduced the infarct volume by 23% and 44%, respectively (both, p < 0.001). The BMSCs + TH, BMSCs + EX, and BMSCs + EX + TH combination therapies significantly reduced the infarct volume by 26%, 51%, and 70%, respectively (all, p < 0.001). A significant improvement in the neurobehavioral functioning was observed in the EX, BMSCs + EX, and BMSCs + EX+ TH groups (p < 0.001). The number of TUNEL-positive cells (a marker of apoptosis) was significantly reduced in the EX, BMSCs, BMSCs + EX, BMSCs + TH, and BMSCs + EX + TH groups (all, p < 0.001). Moreover, the combination therapy considerably increased BrdU-labeled cells in the subventricular zone (SVZ) (p < 0.01). Our findings indicated that the combined treatment of BMSCs with mild EX and TH more efficiently reduces the cerebral infarct size after stroke. More likely, these effects mediate via enchaining generation of new neuronal cells and the attenuation of apoptosis in ischemia stroke in young mice.

Transplantation of mesenchymal stem cells reverses behavioural deficits and impaired neurogenesis caused by prenatal exposure to valproic acid

Neurodevelopmental impairment can affect lifelong brain functions such as cognitive and social behaviour, and may contribute to aging-related changes of these functions. In the present study, we hypothesized that bone marrow-derived mesenchymal stem cells (MSC) administration may repair neurodevelopmental behavioural deficits by modulating adult hippocampal neurogenesis. Indeed, postnatal intracerebral transplantation of MSC has restored cognitive and social behaviour in mice prenatally exposed to valproic acid (VPA). MSC transplantation also restored post-developmental hippocampal neurogenesis, which was impaired in VPA-exposed mice displaying delayed differentiation and maturation of newly formed neurons in the granular cell layer of the dentate gyrus. Importantly, a statistically significant correlation was found between neuronal differentiation scores and behavioural scores, suggesting a mechanistic relation between the two. We thus conclude that post-developmental MSC administration can overcome prenatal neurodevelopmental deficits and restore cognitive and social behaviours via modulation of hippocampal adult neurogenesis.

Stem cell therapies in preclinical models of stroke. Is the aged brain microenvironment refractory to cell therapy?

Stroke is a devastating disease demanding vigorous search for new therapies. Initial enthusiasm to stimulate restorative processes in the ischemic brain by means of cell-based therapies has meanwhile converted into a more balanced view recognizing impediments that may be related to unfavorable age-associated environments. Recent results using a variety of drug, cell therapy or combination thereof suggest that, (i) treatment with Granulocyte-Colony Stimulating Factor (G-CSF) in aged rats has primarily a beneficial effect on functional outcome most likely via supportive cellular processes such as neurogenesis; (ii) the combination therapy, G-CSF with mesenchymal cells (G-CSF+BM-MSC or G-CSF+BM-MNC) did not further improve behavioral indices, neurogenesis or infarct volume as compared to G-CSF alone in aged animals; (iii) better results with regard to integration of transplanted cells in the aged rat environment have been obtained using iPS of human origin; (iv) mesenchymal cells may be used as drug carriers for the aged post-stroke brains.

CONCLUSION

While the middle aged brain does not seem to impair drug and cell therapies, in a real clinical practice involving older post-stroke patients, successful regenerative therapies would have to be carried out for a much longer time.

Granulocyte-Colony Stimulating Factor (G-CSF) for stroke: an individual patient data meta-analysis

Granulocyte colony stimulating factor (G-CSF) may enhance recovery from stroke through neuroprotective mechanisms if administered early, or neurorepair if given later. Several small trials suggest administration is safe but effects on efficacy are unclear. We searched for randomised controlled trials (RCT) assessing G-CSF in patients with hyperacute, acute, subacute or chronic stroke, and asked Investigators to share individual patient data on baseline characteristics, stroke severity and type, end-of-trial modified Rankin Scale (mRS), Barthel Index, haematological parameters, serious adverse events and death. Multiple variable analyses were adjusted for age, sex, baseline severity and time-to-treatment. Individual patient data were obtained for 6 of 10 RCTs comprising 196 stroke patients (116 G-CSF, 80 placebo), mean age 67.1 (SD 12.9), 92% ischaemic, median NIHSS 10 (IQR 5–15), randomised 11 days (interquartile range IQR 4–238) post ictus; data from three commercial trials were not shared. G-CSF did not improve mRS (ordinal regression), odds ratio OR 1.12 (95% confidence interval 0.64 to 1.96, p = 0.62). There were more patients with a serious adverse event in the G-CSF group (29.6% versus 7.5%, p = 0.07) with no significant difference in all-cause mortality (G-CSF 11.2%, placebo 7.6%, p = 0.4). Overall, G-CSF did not improve stroke outcome in this individual patient data meta-analysis.

Bone Marrow Stromal Cells Combined With Sodium Ferulate and n-Butylidenephthalide Promote the Effect of Therapeutic Angiogenesis via Advancing Astrocyte-Derived Trophic Factors After Ischemic Stroke

Being a potential candidate for stroke treatment, bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs) have been demonstrated to be able to enhance angiogenesis and proliferation of reactive astrocytes, which subsequently leads to the amelioration of neurological injury. Increasing evidence further indicates that combining BM-MSCs with certain agents, such as simvastatin, may improve therapeutic effects. Sodium ferulate (SF) and n-butylidenephthalide (BP), two main components of Radix Angelica Sinensis, are proven to be important regulators of stem cells in cell migration, differentiation, and pluripotency maintenance. This study aimed to investigate whether combining BM-MSCs with SF and BP had better therapeutic effect in the treatment of stroke, and the underlying molecular basis for the therapeutic effects was also investigated. The results showed that combination treatment notably reduced neurological injury after stroke and increased the expression of astrocyte-derived vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and von Willebrand factor-positive vascular density in the ischemic boundary zone as evaluated by immunofluorescence staining. After treatment with BM-MSCs plus SF and BP, astrocytes showed increased expression of VEGF and BDNF by upregulating protein kinase B/mammalian target of rapamycin (AKT/mTOR) expression in an oxygen- and glucose-deprived (OGD) environment. Human umbilical vein endothelial cells (HUVECs) incubated with the conditioned medium (CM) derived from OGD astrocytes treated with BM-MSCs plus SF and BP showed significantly increased migration and tube formation compared with those incubated with the CM derived from OGD astrocytes treated with BM-MSCs alone. These results demonstrate that combination treatment enhances the expression of astrocyte-derived VEGF and BDNF, which contribute to angiogenesis after cerebral ischemia, and the underlying mechanism is associated with activation of the astrocytic AKT/mTOR signaling pathway. Our study provides a potential therapeutic approach for ischemic stroke.

Translating G-CSF as an Adjunct Therapy to Stem Cell Transplantation for Stroke

Among recently investigated stroke therapies, stem cell treatment holds great promise by virtue of their putative ability to replace lost cells, promote endogenous neurogenesis,and produce behavioral and functional improvement through their "bystander effects." Translating stem cell in the clinic, however, presents a number of technical difficulties. A strategy suggested to enhance therapeutic utility of stem cells is combination therapy, i.e., co-transplantation of stem cells or adjunct treatment with pharmacological agents and substrates,which is assumed to produce more profound therapeutic benefits by circumventing limitations of individual treatments and facilitating complementary brain repair processes. We previously demonstrated enhanced functional effects of cotreatment with granulocyte-colony stimulating factor (GCSF)and human umbilical cord blood cell (hUCB) transplantation in animal models of traumatic brain injury (TBI). Here,we suggest that the aforementioned combination therapy may also produce synergistic effects in stroke. Accordingly, G-CSF treatment may reduce expression of pro-inflammatory cytokines and enhance neurogenesis rendering a receptive microenvironment for hUCB engraftment. Adjunct treatment of GCSF with hUCB may facilitate stemness maintenance and guide neural lineage commitment of hUCB cells. Moreover, regenerative mechanisms afforded by G-CSF-mobilized endogenous stem cells, secretion of growth factors by hUCB grafts and G-CSF-recruited endothelial progenitor cells(EPCs), as well as the potential graft–host integration that may promote synaptic circuitry re-establishment could altogether produce more pronounced functional improvement in stroked rats subjected to a combination G-CSF treatment and hUCB transplantation. Nevertheless, differences in pathology and repair processes underlying TBI and stroke deserve consideration when testing the effects of combinatorial G-CSF and hUCB cell transplantation for stroke treatment. Further studies are also required to determine the safety and efficacy of this intervention in both preclinical and clinical stroke studies.

Stem Cell Therapy and Administration Routes After Stroke

Cell-based therapy has demonstrated safety and efficacy in experimental animal models of stroke, as well as safety in stroke patients. However, various questions remain regarding the therapeutic window, dosage, route of administration, and the most appropriate cell type and source, as well as mechanisms of action and immune-modulation to optimize treatment based on stem cell therapy. Various delivery routes have been used in experimental stroke models, including intracerebral, intraventricular, subarachnoid, intra-arterial, intraperitoneal, intravenous, and intranasal routes. From a clinical point of view, it is necessary to demonstrate which is the most feasible, safest, and most effective for use with stroke patients. Therefore, further experimental studies concerning the safety, efficacy, and mechanisms of action involved in these therapeutic effects are required to determine their optimal clinical use.

Translational Hurdles in Stroke Recovery Studies

Emerging understanding of brain plasticity has opened new avenues for the treatment of stroke. The promising preclinical evidence with neuroprotective drugs has not been confirmed in clinical trials, thus nowadays, researchers, pharmaceutical companies, and funding bodies hesitate to initiate these expensive trials with restorative therapies. Since many of the previous failures can be traced to low study quality, a number of guidelines such as STAIR and STEPS were introduced to rectify these shortcomings. However, these guidelines stem from the study design for neuroprotective drugs and one may question whether they are appropriate for restorative approaches, which rely heavily on behavioral testing. Most of the recovery studies conducted in stroke patients have been small-scale, proof-of-concept trials. Consequently, the overall effect sizes of pooled phase II trials have proved unreliable and unstable in most meta-analyses. Although the methodological quality of trials in humans is improving, most studies still suffer from methodological flaws and do not meet even the minimum of evidence-based standards for reporting randomized controlled trials. The power problem of most phase II trials is mostly attributable to a lack of proper stratification with robust prognostic factors at baseline as well as the incorrect assumption that all patients will exhibit the same proportional amount of spontaneous neurological recovery poststroke. In addition, most trials suffer from insufficient treatment contrasts between the experimental and control arm and the outcomes have not been sufficiently responsive to detect small but clinically relevant changes in neurological impairments and activities. This narrative review describes the main factors that bias recovery studies, both in experimental animals and stroke patients.

Therapy Effects of Bone Marrow Stromal Cells on Ischemic Stroke

Stroke is the second most common cause of death and major cause of disability worldwide. Recently, bone marrow stromal cells (BMSCs) have been shown to improve functional outcome after stroke. In this review, we will focus on the protective effects of BMSCs on ischemic brain and the relative molecular mechanisms underlying the protective effects of BMSCs on stroke.