Bone marrow mononuclear cells protect neurons and modulate microglia in cell culture models of ischemic stroke

Autologous bone marrow mononuclear cells to treat severe traumatic brain injury in children

Autologous bone marrow mononuclear cells (BMMNCs) infused after severe traumatic brain injury have shown promise for treating the injury. We evaluated their impact in children, particularly their hypothesized ability to preserve the blood-brain barrier and diminish neuroinflammation, leading to structural CNS preservation with improved outcomes. We performed a randomized, double-blind, placebo-sham-controlled Bayesian dose-escalation clinical trial at two children's hospitals in Houston, TX and Phoenix, AZ, USA (NCT01851083). Patients 5-17 years of age with severe traumatic brain injury (Glasgow Coma Scale score ≤ 8) were randomized to BMMNC or placebo (3:2). Bone marrow harvest, cell isolation and infusion were completed by 48 h post-injury. A Bayesian continuous reassessment method was used with cohorts of size 3 in the BMMNC group to choose the safest between two doses. Primary end points were quantitative brain volumes using MRI and microstructural integrity of the corpus callosum (diffusivity and oedema measurements) at 6 months and 12 months. Long-term functional outcomes and ventilator days, intracranial pressure monitoring days, intensive care unit days and therapeutic intensity measures were compared between groups. Forty-seven patients were randomized, with 37 completing 1-year follow-up (23 BMMNC, 14 placebo). BMMNC treatment was associated with an almost 3-day (23%) reduction in ventilator days, 1-day (16%) reduction in intracranial pressure monitoring days and 3-day (14%) reduction in intensive care unit (ICU) days. White matter volume at 1 year in the BMMNC group was significantly preserved compared to placebo [decrease of 19 891 versus 40 491, respectively; mean difference of -20 600, 95% confidence interval (CI): -35 868 to -5332; P = 0.01], and the number of corpus callosum streamlines was reduced more in placebo than BMMNC, supporting evidence of preserved corpus callosum connectivity in the treated groups (-431 streamlines placebo versus -37 streamlines BMMNC; mean difference of -394, 95% CI: -803 to 15; P = 0.055), but this did not reach statistical significance due to high variability. We conclude that autologous BMMNC infusion in children within 48 h after severe traumatic brain injury is safe and feasible. Our data show that BMMNC infusion led to: (i) shorter intensive care duration and decreased ICU intensity; (ii) white matter structural preservation; and (iii) enhanced corpus callosum connectivity and improved microstructural metrics.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Mononuclear cell therapy of neonatal hypoxic-ischemic encephalopathy in preclinical versus clinical studies: a systematic analysis of therapeutic efficacy and study design

Background

Hypoxic-ischemic encephalopathy (HIE) is a devastating condition affecting around 8.5 in 1000 newborns globally. Therapeutic hypothermia (TH) can reduce mortality and, to a limited extent, disability after HIE. Nevertheless, there is a need for new and effective treatment strategies. Cell based treatments using mononuclear cells (MNC), which can be sourced from umbilical cord blood, are currently being investigated. Despite promising preclinical results, there is currently no strong indicator for clinical efficacy of the approach. This analysis aimed to provide potential explanations for this discrepancy.

Methods

A systematic review and meta-analysis was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. Preclinical and clinical studies were retrieved from PubMed, Web of Science, Scopus, and clinicaltrials.gov using a predefined search strategy. A total of 17 preclinical and 7 clinical studies were included. We analyzed overall MNC efficacy in preclinical trials, the methodological quality of preclinical trials and relevant design features in preclinical versus clinical trials.

Results

There was evidence for MNC therapeutic efficacy in preclinical models of HIE. The methodological quality of preclinical studies was not optimal, and statistical design quality was particularly poor. However, methodological quality was above the standard in other fields. There were significant differences in preclinical versus clinical study design including the use of TH as a baseline treatment (only in clinical studies) and much higher MNC doses being applied in preclinical studies.

Conclusions

Based on the analyzed data, it is unlikely that therapeutic effect size is massively overestimated in preclinical studies. It is more plausible that the many design differences between preclinical and clinical trials are responsible for the so far lacking proof of efficacy of MNC treatments in HIE. Additional preclinical and clinical research is required to optimize the application of MNC for experimental HIE treatment.

Cell transplantation therapies for spinal cord injury focusing on bone marrow mesenchymal stem cells: Advances and challenges

Spinal cord injury (SCI) is a devastating condition with complex pathological mechanisms that lead to sensory, motor, and autonomic dysfunction below the site of injury. To date, no effective therapy is available for the treatment of SCI. Recently, bone marrow-derived mesenchymal stem cells (BMMSCs) have been considered to be the most promising source for cellular therapies following SCI. The objective of the present review is to summarize the most recent insights into the cellular and molecular mechanism using BMMSC therapy to treat SCI. In this work, we review the specific mechanism of BMMSCs in SCI repair mainly from the following aspects: Neuroprotection, axon sprouting and/or regeneration, myelin regeneration, inhibitory microenvironments, glial scar formation, immunomodulation, and angiogenesis. Additionally, we summarize the latest evidence on the application of BMMSCs in clinical trials and further discuss the challenges and future directions for stem cell therapy in SCI models.

Microglia-mediated neuroinflammation and neuroplasticity after stroke

Stroke remains a major cause of long-term disability and mortality worldwide. The immune system plays an important role in determining the condition of the brain following stroke. As the resident innate immune cells of the central nervous system, microglia are the primary responders in a defense network covering the entire brain parenchyma, and exert various functions depending on dynamic communications with neurons, astrocytes, and other neighboring cells under both physiological or pathological conditions. Microglia activation and polarization is crucial for brain damage and repair following ischemic stroke, and is considered a double-edged sword for neurological recovery. Microglia can exist in pro-inflammatory states and promote secondary brain damage, but they can also secrete anti-inflammatory cytokines and neurotrophic factors and facilitate recovery following stroke. In this review, we focus on the role and mechanisms of microglia-mediated neuroinflammation and neuroplasticity after ischemia and relevant potential microglia-based interventions for stroke therapy.

Communications Between Peripheral and the Brain-Resident Immune System in Neuronal Regeneration After Stroke

Cerebral ischemia may cause irreversible neural network damage and result in functional deficits. Targeting neuronal repair after stroke potentiates the formation of new connections, which can be translated into a better functional outcome. Innate and adaptive immune responses in the brain and the periphery triggered by ischemic damage participate in regulating neural repair after a stroke. Immune cells in the blood circulation and gut lymphatic tissues that have been shaped by immune components including gut microbiota and metabolites can infiltrate the ischemic brain and, once there, influence neuronal regeneration either directly or by modulating the properties of brain-resident immune cells. Immune-related signalings and metabolites from the gut microbiota can also directly alter the phenotypes of resident immune cells to promote neuronal regeneration. In this review, we discuss several potential mechanisms through which peripheral and brain-resident immune components can cooperate to promote first the resolution of neuroinflammation and subsequently to improved neural regeneration and a better functional recovery. We propose that new insights into discovery of regulators targeting pro-regenerative process in this complex neuro-immune network may lead to novel strategies for neuronal regeneration.

Influence of Bone Marrow-Derived Mesenchymal Stem Cell Therapy on Oxidative Stress Intensity in Minimally Conscious State Patients

Neurological disorders, including minimally conscious state (MCS), may be associated with the presence of high concentrations of reactive oxygen species within the central nervous system. Regarding the documented role of mesenchymal stem cells (MSCs) in oxidative stress neutralization, the aim of this study is to evaluate the effect of bone marrow-derived MSC (BM-MSC) transplantation on selected markers of oxidative stress in MCS patients. Antioxidant capacity was measured in cerebrospinal fluid (CSF) and plasma collected from nine patients aged between 19 and 45 years, remaining in MCS for 3 to 14 months. Total antioxidant capacity, ascorbic acid and ascorbate concentrations, superoxide dismutase, catalase, and peroxidase activity were analyzed and the presence of tested antioxidants in the CSF and plasma was confirmed. Higher ascorbic acid (AA) content and catalase (CAT) activity were noted in CSF relative to plasma, whereas superoxide dismutase (SOD) activity and total antioxidant capacity were higher in plasma relative to CSF. Total antioxidant capacity measured in CSF was greater after BM-MSC transplantations. The content of ascorbates was lower and CAT activity was higher both in CSF and plasma after the administration of BM-MSC. The above results suggest that MSCs modulate oxidative stress intensity in MCS patients, mainly via ascorbates and CAT activity.

Loss of RHBDF2 results in an early-onset spontaneous murine colitis

Inflammatory bowel disease (IBD) is a heterogeneous group of inflammation-mediated pathologies that include Crohn's disease and ulcerative colitis and primarily affects the colon and small intestine. Previous studies have shown that a disintegrin and metalloprotease (ADAM) 17, a membrane-bound sheddase, capable of cleaving the proinflammatory cytokine TNF and epidermal growth factor receptor ligands, plays a critical role in maintaining gut homeostasis and modulating intestinal inflammation during IBD. Rhomboid 5 homolog 2 (RHBDF2), a catalytically inactive member of the rhomboid family of intramembrane serine proteases, was recently identified as a crucial regulator of ADAM17. Here, we assessed the role of RHBDF2 in the development of colitis in the context of IL10 deficiency. Il10^-/- /Rhbdf2^-/- mice developed spontaneous colitis and experienced severe weight loss starting at 8 wk of age, without the need for exogenous triggers. Severity of disease pathology in Il10^-/- /Rhbdf2^-/- mice correlated with a dysbiotic gut microbiota and elevated Th1-associated immune responses with increased interferon gamma and IL2 production. In addition, Il10^-/- /Rhbdf2^-/- mice failed to maintain their epithelial cell homeostasis, although the intestinal epithelial barrier of Rhbdf2^-/- mice is intact and loss of Rhbdf2 did not significantly exacerbate sensitivity to dextran sulfate sodium-induced colitis, suggesting differences in the underlying disease pathway of intestinal inflammation in this model. Taken together, our results demonstrate a critical regulatory role for RHBDF2 in the maintenance of the unique homeostasis between intestinal microbiota and host immune responses in the gut that is dysregulated during the pathogenesis of IBD.

Protective Effects of Autologous Bone Marrow Mononuclear Cells After Administering t-PA in an Embolic Stroke Model

Tissue plasminogen activator (t-PA) is the only FDA-approved drug for acute ischemic stroke but poses risk for hemorrhagic transformation (HT). Cell therapy has been investigated as a potential therapy to improve recovery after stroke by the modulation of inflammatory responses and the improvement of blood-brain barrier (BBB) integrity, both of which are associated with HT after t-PA. In our present study, we studied the effect of autologous bone marrow mononuclear cells (MNCs) in an embolic stroke model. We administered MNCs in a rat embolic stroke 2 h after administering t-PA. We observed that even though autologous MNCs did not alter the incidence of HT, they decreased the severity of HT and reduced BBB permeability. One possible mechanism could be through the inhibition of MMP3 released by astrocytes via JAK/STAT pathway as shown by our in vitro cell interaction studies.

Treatment of Severe Adult Traumatic Brain Injury Using Bone Marrow Mononuclear Cells

Preclinical studies using bone marrow derived cells to treat traumatic brain injury have demonstrated efficacy in terms of blood-brain barrier preservation, neurogenesis, and functional outcomes. Phase 1 clinical trials using bone marrow mononuclear cells infused intravenously in children with severe traumatic brain injury demonstrated safety and potentially a central nervous system structural preservation treatment effect. This study sought to confirm the safety, logistic feasibility, and potential treatment effect size of structural preservation/inflammatory biomarker mitigation in adults to guide Phase 2 clinical trial design. Adults with severe traumatic brain injury (Glasgow Coma Scale 5-8) and without signs of irreversible brain injury were evaluated for entry into the trial. A dose escalation format was performed in 25 patients: 5 controls, followed 5 patients in each dosing cohort (6, 9, 12 ×106 cells/kg body weight), then 5 more controls. Bone marrow harvest, cell processing to isolate the mononuclear fraction, and re-infusion occurred within 48 hours after injury. Patients were monitored for harvest-related hemodynamic changes, infusional toxicity, and adverse events. Outcome measures included magnetic resonance imaging-based measurements of supratentorial and corpus callosal volumes as well as diffusion tensor imaging-based measurements of fractional anisotropy and mean diffusivity of the corpus callosum and the corticospinal tract at the level of the brainstem at 1 month and 6 months postinjury. Functional and neurocognitive outcomes were measured and correlated with imaging data. Inflammatory cytokine arrays were measured in the plasma pretreatment, posttreatment, and at 1 and 6 month follow-up. There were no serious adverse events. There was a mild pulmonary toxicity of the highest dose that was not clinically significant. Despite the treatment group having greater injury severity, there was structural preservation of critical regions of interest that correlated with functional outcomes. Key inflammatory cytokines were downregulated. Treatment of severe, adult traumatic brain injury using an intravenously delivered autologous bone marrow mononuclear cell infusion is safe and logistically feasible. There appears to be a treatment signal as evidenced by central nervous system structural preservation, consistent with previous pediatric trial data. Inflammatory biomarkers are downregulated after cell infusion. Stem Cells 2016 Video Highlight: https://youtu.be/UiCCPIe-IaQ Stem Cells 2017;35:1065-1079.

Paracrine Mechanisms of Intravenous Bone Marrow-Derived Mononuclear Stem Cells in Chronic Ischemic Stroke

Background

The emerging role of stem cell technology and transplantation has helped scientists to study their potential role in neural repair and regeneration. The fate of stem cells is determined by their niche, consisting of surrounding cells and the secreted trophic growth factors. This interim report evaluates the safety, feasibility and efficacy (if any) of bone marrow-derived mononuclear stem cells (BM-MNC) in chronic ischemic stroke by studying the release of serum vascular endothelial growth factor (VEGF) and brain-derived neurotrophic growth factor (BDNF).

Methods

Twenty stroke patients and 20 age-matched healthy controls were recruited with the following inclusion criteria: 3 months to 1.5 years from the index event, Medical Research Council (MRC) grade of hand muscles of at least 2, Brunnstrom stage 2-5, conscious, and comprehendible. They were randomized to one group receiving autologous BM-MNC (mean 60-70 million) and to another group receiving saline infusion (placebo). All patients were administered a neuromotor rehabilitation regime for 8 weeks. Clinical assessments [Fugl Meyer scale (FM), modified Barthel index (mBI), MRC grade, Ashworth tone scale] were carried out and serum VEGF and BDNF levels were assessed at baseline and at 8 weeks.

Results

No serious adverse events were observed during the study. There was no statistically significant clinical improvement between the groups (FM: 95% CI 15.2-5.35, p = 0.25; mBI: 95% CI 14.3-4.5, p = 0.31). VEGF and BDNF expression was found to be greater in group 1 compared to group 2 (VEGF: 442.1 vs. 400.3 pg/ml, p = 0.67; BDNF: 21.3 vs. 19.5 ng/ml) without any statistically significant difference.

Conclusion

Autologous mononuclear stem cell infusion is safe and tolerable by chronic ischemic stroke patients. The released growth factors (VEGF and BDNF) in the microenvironment could be due to the paracrine hypothesis of stem cell niche and neurorehabilitation regime.

Systematic Review and Meta-Analysis of Bone Marrow-Derived Mononuclear Cells in Animal Models of Ischemic Stroke

BACKGROUND AND PURPOSE

Bone marrow-derived mononuclear cells (BMMNCs) offer the promise of augmenting poststroke recovery. There is mounting evidence of safety and efficacy of BMMNCs from preclinical studies of ischemic stroke; however, their pooled effects have not been described.

METHODS

Using Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines, we conducted a systematic review of preclinical literature for intravenous use of BMMNCs followed by meta-analyses of histological and behavioral outcomes. Studies were selected based on predefined criteria. Data were abstracted by 2 independent investigators. After quality assessment, the pooled effects were generated using mixed-effect models. Impact of possible biases on estimated effect size was evaluated.

RESULTS

Standardized mean difference and 95% confidence interval for reduction in lesion volume was significantly beneficial for BMMNC treatment (standardized mean difference: -3.3; 95% confidence interval, -4.3 to -2.3). n=113 each for BMMNC and controls. BMMNC-treated animals (n=161) also had improved function measured by cylinder test (standardized mean difference: -2.4; 95% confidence interval, -3.1 to -1.6), as compared with controls (n=205). A trend for benefit was observed for adhesive removal test and neurological deficit score. Study quality score (median: 6; Q1-Q3: 5-7) was correlated with year of publication. There was funnel plot asymmetry; however, the pooled effects were robust to the correction of this bias and remained significant in favor of BMMNC treatment.

CONCLUSIONS

BMMNCs demonstrate beneficial effects across histological and behavioral outcomes in animal ischemic stroke models. Although study quality has improved over time, considerable degree of heterogeneity calls for standardization in the conduct and reporting of experimentation.

Various Cell Populations Within the Mononuclear Fraction of Bone Marrow Contribute to the Beneficial Effects of Autologous Bone Marrow Cell Therapy in a Rodent Stroke Model

Cell-based therapies including bone-marrow derived mononuclear cells (MNCs) are now widely being studied because of their pleotropic effects and promising results to improve recovery after stroke in animal models. Unlike other types of cell therapies, MNCs is a mixture of lymphoid, myeloid, erythroid, and stem cell populations. Which cell population(s) accounts for the beneficial effects of MNCs in stroke recovery is unclear. In this paper, we employed a mouse stroke model with middle cerebral artery occlusion (MCAo), and used positively and negatively sorted autologous MNCs by MACs to determine which fractions of the MNCs contribute to their beneficial effects. We evaluated the benefits of neurofunctional recovery produced by individual cell lineages within MNCs in a long-term observation study up to 28 days after stroke. Mortality and modulation of inflammation were also compared among different sub-populations. We further studied the impact of neurotoxicity posed by activated microglia in the presence of different cell lineages within MNCs. We concluded that myeloid cell lineage and stem cell/progenitors appeared to be important components within MNCs that contribute to improved outcomes after stroke.

Preconditioning with VEGF Enhances Angiogenic and Neuroprotective Effects of Bone Marrow Mononuclear Cell Transplantation in a Rat Model of Chronic Cerebral Hypoperfusion

Bone marrow mononuclear cell (BMMNC) transplantation is a promising therapy for brain ischemia. However, BMMNCs are few in number, and a limited time window is available during which they can penetrate the blood-brain barrier (BBB) and migrate to the brain. We investigated whether vascular endothelial growth factor (VEGF) can facilitate BMMNC migration into the ischemic brain and enhance their therapeutic effect in a rat model of chronic cerebral hypoperfusion. First, we assessed the impact of VEGF on the BBB of rats that had undergone permanent bilateral occlusion of the common carotid arteries (2VO). Then, we transplanted BMMNCs into 2VO rats pretreated with intracerebroventricular VEGF or vehicle. We examined cognitive function with the Morris water maze test, BMMNC migration by immunofluorescence analysis, and cytokine levels in the peripheral blood by enzyme-linked immunosorbent assay (ELISA). Angiogenesis and neural degeneration were evaluated by staining tissue with Ki67/lectin or Fluoro-Jade B. We found that at a dose of 0.2 μg/rat, VEGF significantly increased BBB permeability without causing brain edema in 2VO rats. VEGF + BMMNC-treated rats had more BMMNC migration in the ischemic brain, better learning and memory, greater proliferation of vessels, and fewer degenerating neurons than did BMMNC-treated rats. Pretreatment with VEGF receptor inhibitor SU5416 significantly decreased BMMNC migration and abolished the therapeutic effect of BMMNC transplantation. We conclude that preconditioning with an appropriate dose of VEGF can enhance the therapeutic efficacy of BMMNC transplantation in 2VO rats, possibly by facilitating BMMNC migration into the ischemic brain.

The effect of autologous bone marrow mononuclear cell transplantation on the survival duration in Amyotrophic Lateral Sclerosis - a retrospective controlled study

Amyotrophic Lateral Sclerosis (ALS) is a rapidly progressive neurodegenerative disorder with fatal prognosis. Cellular therapy has been studied for ALS in various animal models and these advances have highlighted its potential to be a treatment modality. This is a retrospective controlled cohort study of total 57 patients. Out of these, 37 patients underwent autologous bone marrow mononuclear cell transplantation in addition to standard rehabilitation and Riluzole. Control group consisted of 20 patients who did not receive cell transplantation. The survival duration since the onset of the disease for both the groups was computed using a Kaplan-Meier Survival analysis and compared using log-rank test. Effect of age at onset, type of onset and lithium on survival duration in the intervention group was analyzed. Mean survival duration of patients in intervention group was 87.76 months which was higher than the control group mean survival duration of 57.38 months. Survival duration was significantly (p = 0.039) higher in people with the onset of the disease below 50 years of age. Limb onset and lithium also showed positive influence on the survival duration. Mean survival duration of the intervention group was also higher than the survival duration of ALS patients in previous epidemiological studies. In addition to the standard treatment with Riluzole, early intervention with combination of BMMNCs transplantation and Lithium may have a positive effect on the survival duration in ALS. Prospective randomized controlled studies with a larger sample size and rigorous methodology are required for conclusive findings.

CXCR4(+)CD45(-) BMMNC subpopulation is superior to unfractionated BMMNCs for protection after ischemic stroke in mice

Cell-based therapy is considered to be a promising therapeutic strategy for stroke treatment. Although unfractionated bone marrow mononuclear cells (BMMNCs) have been tried in both preclinical and clinical trials, the effective subpopulations need to be identified. In this study, we used fluorescence-activated cell sorting to harvest the CXCR4(+)CD45(+) and CXCR4(+)CD45(-) BMMNC subpopulations from transgenic mice that express enhanced green fluorescent protein. We then allogeneically grafted unfractionated BMMNCs or a subpopulation into mice subjected to transient middle cerebral artery occlusion (tMCAO) and compared the effects on stroke outcomes. We found that CXCR4(+)CD45(-) BMMNCs, but not CXCR4(+)CD45(+) BMMNCs, more effectively reduced infarction volume and neurologic deficits than did unfractionated BMMNCs. Brain tissue from the ischemic hemisphere of mice treated with CXCR4(+)CD45(-) BMMNCs had higher levels of vascular endothelial growth factor and lower levels of TNF-α than did tissue from mice treated with unfractionated BMMNCs. In contrast, CXCR4(+)CD45(+) BMMNCs showed an increase in TNF-α. Additionally, CXCR4(+)CD45(+) and CXCR4(+)CD45(-) populations exhibited more robust migration into the lesion areas and were better able to express cell-specific markers of different linages than were the unfractionated BMMNCs. Endothelial and astrocyte cell markers did not colocalize with eGFP(+) cells in the brains of tMCAO mice that received CXCR4(+)CD45(+) BMMNCs. In vitro, the CXCR4(+)CD45(-) BMMNCs expressed significantly more Oct-4 and Nanog mRNA than did the unfractionated BMMNCs. However, we did not detect gene expression of these two pluripotent markers in CXCR4(+)CD45(+) BMMNCs. Taken together, our study shows for the first time that the CXCR4(+)CD45(-) BMMNC subpopulation is superior to unfractionated BMMNCs in ameliorating cerebral damage in a mouse model of tMCAO and could represent a new therapeutic approach for stroke treatment.

Bone marrow-derived mononuclear cells do not exert acute neuroprotection after stroke in spontaneously hypertensive rats

Bone marrow-derived mononuclear cells (BM-MNCs) were shown to improve the outcome in animal stroke models and clinical pilot studies on BM-MNCs for stroke patients were already conducted. However, relevant aspects of pre-clinical evaluation, such as the use of animals with comorbidities and dose-response studies, were not thoroughly addressed so far. We therefore investigated different BM-MNC doses in the clinical meaningful stroke model of spontaneously hypertensive (SH) rats. Three hours after the onset of transient middle cerebral artery occlusion (MCAO) animals received either one of three syngeneic BM-MNC doses or placebo intravenously. The primary endpoint was the infarct size. Secondary endpoints included functional outcome, mortality, inflammatory processes, and the dose-response relationship. In contrast to previous studies which used healthy animals no beneficial effect of BM-MNCs was found. Infarct volumes, mortality, behavioral outcomes, and the extent of the inflammatory response to cerebral ischemia were comparable in all groups. In conclusion, we could not demonstrate that early BM-MNC treatment improves the outcome after stroke in SH rats. Whether BM-MNCs improve neurological recovery after delayed treatment initiation was not investigated in the present study, but our data indicates that this should be determined in co-morbid animal stroke models before moving to large-scale clinical studies. Future preclinical stroke studies on co-morbid animals should also include groups of healthy animals in order to determine whether negative results can be attributed to the comorbid condition.

Early transplantation of bone marrow mononuclear cells promotes neuroprotection and modulation of inflammation after status epilepticus in mice by paracrine mechanisms

Status epilepticus (SE) is a severe clinical manifestation of epilepsy associated with intense neuronal loss and inflammation, two key factors involved in the pathophysiology of temporal lobe epilepsy. Bone marrow mononuclear cells (BMMC) attenuated the consequences of pilocarpine-induced SE, including neuronal loss, in addition to frequency and duration of seizures. Here we investigated the effects of BMMC transplanted early after the onset of SE in mice, as well as the involvement of soluble factors produced by BMMC in the effects of the cell therapy. Mice were injected with pilocarpine for SE induction and randomized into three groups: transplanted intravenously with 1 × 10(7) BMMC isolated from GFP transgenic mice, injected with BMMC lysate, and saline-treated controls. Cell tracking, neuronal counting in hippocampal subfields and cytokine analysis in the serum and brain were performed. BMMC were found in the brain 4 h following transplantation and their numbers progressively decreased until 24 h following transplantation. A reduction in hippocampal neuronal loss after SE was found in mice treated with live BMMC and BMMC lysate when compared to saline-treated, SE-induced mice. Moreover, the expression of inflammatory cytokines IL-1β, TNF-α, IL-6 was decreased after injection of live BMMC and to a lesser extent, of BMMC lysate, when compared to SE-induced controls. In contrast, IL-10 expression was increased. Analysis of markers for microglia activation demonstrated a reduction of the expression of genes related to type 1-activation. BMMC transplantation promotes neuroprotection and mediates anti-inflammatory effects following SE in mice, possibly through the secretion of soluble factors.

Bone marrow-derived microglia infiltrate into the paraventricular nucleus of chronic psychological stress-loaded mice

Background

Microglia of the central nervous system act as sentinels and rapidly react to infection or inflammation. The pathophysiological role of bone marrow-derived microglia is of particular interest because they affect neurodegenerative disorders and neuropathic pain. The hypothesis of the current study is that chronic psychological stress (chronic PS) induces the infiltration of bone marrow-derived microglia into hypothalamus by means of chemokine axes in brain and bone marrow.

Methods and Findings

Here we show that bone marrow-derived microglia specifically infiltrate the paraventricular nucleus (PVN) of mice that received chronic PS. Bone marrow derived-microglia are CX₃CR1^lowCCR2⁺CXCR4^high, as distinct from CX₃CR1^highCCR2^-CXCR4^low resident microglia, and express higher levels of interleukin-1β (IL-1β) but lower levels of tumor necrosis factor-α (TNF-α). Chronic PS stimulates the expression of monocyte chemotactic protein-1 (MCP-1) in PVN neurons, reduces stromal cell-derived factor-1 (SDF-1) in the bone marrow and increases the frequency of CXCR4⁺ monocytes in peripheral circulation. And then a chemokine (C-C motif) receptor 2 (CCR2) or a β₃-adrenoceptor blockade prevents infiltration of bone marrow-derived microglia in the PVN.

Conclusion

Chronic PS induces the infiltration of bone marrow-derived microglia into PVN, and it is conceivable that the MCP-1/CCR2 axis in PVN and the SDF-1/CXCR4 axis in bone marrow are involved in this mechanism.

Bone marrow mononuclear cells exert long-term neuroprotection in a rat model of ischemic stroke by promoting arteriogenesis and angiogenesis

Transplanted bone marrow-derived mononuclear cells (BMMNCs) can promote arteriogenesis and angiogenesis by incorporating into vascular walls and differentiating into smooth muscle cells (SMCs) and endothelial cells (ECs). Here, we explored whether BMMNCs can enhance arteriogenesis and angiogenesis and promote long-term functional recovery in a rat model of permanent middle cerebral artery occlusion (pMCAO). Sprague-Dawley rats were injected with vehicle or 1×10(7) BMMNCs labeled with BrdU via femoral vein 24 h after induction of pMCAO. Functional deficits were assessed weekly through day 42 after pMCAO, and infarct volume was assessed on day 7. We visualized the angioarchitecture by latex perfusion on days 14 and 42. BMMNC transplantation significantly reduced infarct volume and neurologic functional deficits compared with untreated or vehicle-treated ischemic groups. In BMMNC-treated rats, BrdU-positive cells were widely distributed in the infarct boundary zone, were incorporated into vessel walls, and enhanced the growth of leptomeningeal anastomoses, the circle of Willis, and basilar arteries. BMMNCs were shown to differentiate into SMCs and ECs from day 14 after stroke and preserved vascular repair function for at least 6 weeks. Our data indicate that BMMNCs can significantly enhance arteriogenesis and angiogenesis, reduce infarct volume, and promote long-term functional recovery after pMCAO in rats.

Microglial responses after ischemic stroke and intracerebral hemorrhage

Stroke is a leading cause of death worldwide. Ischemic stroke is caused by blockage of blood vessels in the brain leading to tissue death, while intracerebral hemorrhage (ICH) occurs when a blood vessel ruptures, exposing the brain to blood components. Both are associated with glial toxicity and neuroinflammation. Microglia, as the resident immune cells of the central nervous system (CNS), continually sample the environment for signs of injury and infection. Under homeostatic conditions, they have a ramified morphology and phagocytose debris. After stroke, microglia become activated, obtain an amoeboid morphology, and release inflammatory cytokines (the M1 phenotype). However, microglia can also be alternatively activated, performing crucial roles in limiting inflammation and phagocytosing tissue debris (the M2 phenotype). In rodent models, microglial activation occurs very early after stroke and ICH; however, their specific roles in injury and repair remain unclear. This review summarizes the literature on microglial responses after ischemic stroke and ICH, highlighting the mediators of microglial activation and potential therapeutic targets for each condition.

Effects of bone marrow stromal cell transplantation through CSF on the subacute and chronic spinal cord injury in rats

It has been demonstrated that the infusion of bone marrow stromal cells (BMSCs) through the cerebrospinal fluid (CSF) has beneficial effects on acute spinal cord injury (SCI) in rats. The present study examined whether BMSC infusion into the CSF is effective for subacute (1- and 2-week post-injury), and/or chronic (4-week post-injury) SCI in rats. The spinal cord was contused by dropping a weight at the thoracic 8-9 levels. BMSCs cultured from GFP-transgenic rats of the same strain were injected three times (once weekly) into the CSF through the fourth ventricle, beginning at 1, 2 and 4 weeks post-injury. At 4 weeks after initial injection, the average BBB score for locomotor assessment increased from 1.0–3.5 points before injection to 9.0-10.9 points in the BMSC-injection subgroups, while, in the PBS (vehicle)-injection subgroups, it increased only from 0.5–4.0 points before injection to 3.0-5.1 points. Numerous axons associated with Schwann cells extended longitudinally through the connective tissue matrices in the astrocyte-devoid lesion without being blocked at either the rostral or the caudal borders in the BMSC-injection subgroups. A small number of BMSCs were found to survive within the spinal cord lesion in SCI of the 1-week post-injury at 2 days of injection, but none at 7 days. No BMSCs were found in the spinal cord lesion at 2 days or at 7 days in the SCI of the 2-week and the 4-week post-injury groups. In an in vitro experiment, BMSC-injected CSF promoted the survival and the neurite extension of cultured neurons more effectively than did the PBS-injected CSF. These results indicate that BMSCs had beneficial effects on locomotor improvement as well as on axonal regeneration in both subacute and chronic SCI rats, and the results also suggest that BMSCs might function as neurotrophic sources via the CSF.

Comparison of the therapeutic effects of bone marrow mononuclear cells and microglia for permanent cerebral ischemia

In this study we transplanted bone marrow mononuclear cells (BM-MNCs) or microglia into rats that had undergone permanent cerebral ischemia and observed the distribution or morphology of transplanted cells in vivo. In addition, we compared the effects of BM-MNCs and microglia on infarct volume, brain water content, and functional outcome after permanent cerebral ischemia. BM-MNCs and microglia were obtained from femur and brain, respectively, of newborn rats. Adult rats were injected with vehicle or 3 million BM-MNCs or microglia via the tail vein 24h after permanent middle cerebral artery occlusion (pMCAO). The distribution or morphologic characteristics of transplanted BM-MNCs (double stained with BrdU/Cd34 or BrdU/CD45) and microglia (double stained with BrdU/Iba-1) were detected with immunofluorescent staining at 3 or 7 and 14 days after pMCAO. Functional deficits were assessed by the modified neurologic severity score at 1, 3, 7 and 14 days after pMCAO. Brain water content was assessed at 3 days, and infarct volume was determined at 14 days. We observed more BrdU/CD45 and BrdU/Iba-1 double-stained cells than BrdU/CD34 double-stained cells around the infarcted area. Some infused microglia showed the morphology of innate microglia at 7 days after pMCAO, and the number increased at 14 days. BM-MNC-treated rats showed significantly reduced infarct volume and brain water content compared to vehicle- and microglia-treated rats. In addition, BM-MNC treatment reduced neurologic deficit scores compared to those in the other groups. The results provide evidence that infusion of BM-MNCs, but not microglia, is neuroprotective after permanent cerebral ischemia.

Clinical significance of metallothioneins in cell therapy and nanomedicine

Mammalian metallothioneins (MTs) are low molecular weight (6–7 kDa) cysteine-rich proteins that are specifically induced by metal nanoparticles (NPs). MT induction in cell therapy may provide better protection by serving as antioxidant, anti-inflammatory, antiapoptotic agents, and by augmenting zinc-mediated transcriptional regulation of genes involved in cell proliferation and differentiation. Liposome-encapsulated MT-1 promoter has been used extensively to induce growth hormone or other genes in culture and gene-manipulated animals. MTs are induced as a defensive mechanism in chronic inflammatory conditions including neurodegenerative diseases, cardiovascular diseases, cancer, and infections, hence can serve as early and sensitive biomarkers of environmental safety and effectiveness of newly developed NPs for clinical applications. Microarray analysis has indicated that MTs are significantly induced in drug resistant cancers and during radiation treatment. Nutritional stress and environmental toxins (eg, kainic acid and domoic acid) induce MTs and aggregation of multilamellar electron-dense membrane stacks (Charnoly body) due to mitochondrial degeneration. MTs enhance mitochondrial bioenergetics of reduced nicotinamide adenine dinucleotide–ubiquinone oxidoreductase (complex-1), a rate-limiting enzyme complex involved in the oxidative phosphorylation. Monoamine oxidase-B inhibitors (eg, selegiline) inhibit α-synuclein nitration, implicated in Lewy body formation, and inhibit 1-methyl 4-phenylpyridinium and 3-morpholinosydnonimine-induced apoptosis in cultured human dopaminergic neurons and mesencephalic fetal stem cells. MTs as free radical scavengers inhibit Charnoly body formation and neurodegenerative α-synucleinopathies, hence Charnoly body formation and α-synuclein index may be used as early and sensitive biomarkers to assess NP effectiveness and toxicity to discover better drug delivery and surgical interventions. Furthermore, pharmacological interventions augmenting MTs may facilitate the theranostic potential of NP-labeled cells and other therapeutic agents. These unique characteristics of MTs might be helpful in the synthesis, characterization, and functionalization of emerging NPs for theranostic applications. This report highlights the clinical significance of MTs and their versatility as early, sensitive biomarkers in cell-based therapy and nanomedicine.

MyD88 is a critical regulator of hematopoietic cell-mediated neuroprotection seen after stroke

Neuroinflammation is critical in the neural cell death seen in stroke. It has been shown that CNS and peripheral responses drive this neuroinflammatory response in the brain. The Toll-like receptors (TLRs) are important regulators of inflammation in response to both exogenous and endogenous stressors. Taking advantage of a downstream adapter molecule that controls the majority of TLR signalling, this study investigated the role of the TLR adaptor protein myeloid differentiation factor 88 (MyD88) in the control of CNS and peripheral inflammation. Reversible middle-cerebral artery occlusion was used as the model of stroke in vivo; in vitro primary cultured neurons and glia were subject to four hours of oxygen and glucose deprivation (OGD). Both in vitro and in vivo Myd88^−/− animals or cells were compared with wild type (WT). We found that after stroke Myd88^−/− animals have a larger infarct volume compared to WT animals. Interestingly, in vitro there was no difference between the survival of Myd88^−/− and WT cells following OGD, suggesting that peripheral responses were influencing stroke outcome. We therefore generated bone marrow chimeras and found that Myd88^−/− animals have a smaller stroke infarct than their radiation naive counterparts if their hematopoietic cells are WT. Furthermore, WT animals have a larger stroke than their radiation naive counterparts if the hematopoietic cells are Myd88^−/−. We have demonstrated that MyD88-dependent signalling in the hematopoietic cell lineage reduces infarct size following stroke and that infiltrating cells to the site of neuroinflammation are neuroprotective following stroke.

High glucose induces apoptosis and suppresses proliferation of adult rat neural stem cells following in vitro ischemia

Background

Post-stroke hyperglycemia appears to be associated with poor outcome from stroke, greater mortality, and reduced functional recovery. Focal cerebral ischemia data support that neural stem cells (NSCs) play an important role in post-ischemic repair. Here we sought to evaluate the negative effects of hyperglycemia on the cellular biology of NSCs following anoxia, and to test whether high glucose affects NSC recovery from ischemic injury.

Results

In this study, we used immortalized adult neural stem cells lines and we induced in vitro ischemia by 6 h oxygen and glucose deprivation (OGD) in an anaerobic incubator. Reperfusion was performed by returning cells to normoxic conditions and the cells were then incubated in experimental medium with various concentrations of glucose (17.5, 27.75, 41.75, and 83.75 mM) for 24 h. We found that high glucose (≥27.75 mM) exposure induced apoptosis of NSCs in a dose-dependent manner after exposure to OGD, using an Annexin V/PI apoptosis detection kit. The cell viability and proliferative activity of NSCs following OGD in vitro, evaluated with both a Cell Counting kit-8 (CCK-8) assay and a 5-ethynyl-2’-deoxyuridine (EdU) incorporation assay, were inhibited by high glucose exposure. Cell cycle analysis showed that high glucose exposure increased the percentage of cells in G0/G1-phase, and reduced the percentage of cells in S-phase. Furthermore, high glucose exposure was found to significantly induce the activation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) and suppress extracellular signal-regulated kinase 1/2 (ERK1/2) activity.

Conclusions

Our results demonstrate that high glucose induces apoptosis and inhibits proliferation of NSCs following OGD in vitro, which may be associated with the activation of JNK/p38 MAPK pathways and the delay of G1-S transition in the cells.

The potential benefit of stem cell therapy after stroke: an update

Stroke is a leading cause of death and disability worldwide. Stem cell therapy is an emerging therapeutic modality with evidence of significant benefits in preclinical stroke models. A number of phase I and II clinical trials have now been completed, with several more currently under way. Translation to the bedside, however, remains a long way off, and there are many questions that remain unanswered. This review will summarize the current evidence and ongoing clinical trials worldwide, and explore the challenges to making this a realistic treatment option for the future.

Impact of age on the efficacy of bone marrow mononuclear cell transplantation in experimental stroke

Bone marrow-derived mononuclear cells (BM MNC) have been effectively used to treat experimental stroke. Most of the preclinical trials have been performed in young and healthy laboratory animals, even though age and hypertension are major risk factors for stroke. To determine the influence of age on the properties of BM MNCs after cerebral ischemia, we compared the efficacy of aged and young BM MNC in an in vitro model of cerebral hypoxia and in an adapted in vivo model of stroke. Human BM MNCs were obtained from healthy young or aged donors and either co-cultured with rat hippocampal slices exposed to oxygen glucose deprivation (OGD), or transplanted intravenously 24 h after permanent middle cerebral artery occlusion in aged (18 months) spontaneously hypertensive rats (SHR). Efficacy was examined by quantification of hippocampal cell death, or respectively, by neurofunctional tests and MR investigations. Co-cultivation with young, but not with aged BM MNCs significantly reduced the hippocampal cell death after OGD. Transplantation of both young and old BM MNCs did not reduce functional deficits or ischemic lesion volume after stroke in aged SHR. These results suggest a significant impact of age on the therapeutic efficacy of BM MNCs after cerebral ischemia.

Ischemic stroke may activate bone marrow mononuclear cells to enhance recovery after stroke

Bone marrow-derived mononuclear cells (MNCs) enhance recovery in rodent stroke models. Since stroke activates the bone marrow, there may be biological differences of autologous MNCs derived poststroke compared with the prestroke setting. We analyzed MNCs harvested from the same Long Evans rats 1 day before and 1 day after ischemic stroke or sham stroke. Stroke was induced by suture occlusion of the middle cerebral artery for 90 min. MNCs were characterized by flow cytometry to identify differences in the percentages of different cell subpopulations. MNCs were also placed in culture and cytokines were measured in the media. In separate experiments, Long Evans rats received 24 h after stroke an intracarotid injection of saline or autologous MNCs, prepared from the same animal, either 1 day before or 1 day after stroke. The rats were then followed on the cylinder and corner tests for 28 days. In poststroke MNCs compared with prestroke MNCs, there was a significant reduction in T and mesenchymal stem cells and a significant increase in CD34+ and natural killer cells. Postsham MNCs showed an elevation in CD11b and CD45R cells compared with presham MNCs. The concentrations of IL-10, IL-6, MCP-1, vascular endothelial growth factor (VEGF), and tumor necrosis factor-α were significantly increased in poststroke MNCs compared with prestroke MNCs. Postsham MNCs showed a decrease in VEGF. Poststroke MNCs in comparison with prestroke MNCs led to a greater recovery on neurological testing and reduced lesion size. Autologous MNCs exert different biological responses when derived from the poststroke setting compared with normal animals.

The potential of stem cell therapy for stroke: is PISCES the sign?

Substantial developments in the field of stem cell research point toward novel therapies for the treatment of diseases such as stroke. This review covers the establishment of tissue damage in stroke and the status of current therapies. We evaluate stem cell therapy with respect to other treatments, including clinical, preclinical, and failed, and provide a comprehensive account of stem cell clinical trials for stroke therapy currently underway. Finally, we describe mechanisms through which stem cells improve outcome in experimental stroke as well as potential pitfalls this basic research has identified.

Histopathological Investigation of Different MCAO Modalities and Impact of Autologous Bone Marrow Mononuclear Cell Administration in an Ovine Stroke Model

Translational researchers and clinicians recommend the use of large animal models in preclinical stroke research. This represents an important part of a strategy aiming to prevent past translational failures in future therapeutic developments. Thirty-five Merino rams were subjected to sham surgery (n = 3), one-branch middle cerebral artery occlusion (MCAO, n = 8) or total MCAO (n = 24). Twelve animals from the latter group received intravenous administration of 4 × 10⁶ autologous mononuclear bone marrow cells (BM MNC) per kilogram 24 h after total MCAO. Animals were sacrificed at day 49 post MCAO. Histological investigations were performed to reveal (1) the impact of different MCAO modalities on a cellular level and (2) the influence of BM MNC therapy following stroke. Clear differences between one-branch and total MCAO were observed histologically with results being comparable to those seen in human patients. BM MNC treatment reduced final lesion extension, lymphocytic infiltration and axonal degeneration after MCAO. The sheep model may represent a feasible tool for translational stroke research as pathohistological findings mimic the situation in humans. Histological evidence was found for beneficial impact of autologous BM MNC therapy. Further studies are needed to assess the neurofunctional impact of the approach in the gyrencephalic brain.

Potential benefits of allogeneic bone marrow mesenchymal stem cells for wound healing

INTRODUCTION

It is becoming increasingly evident that select adult stem cells have the capacity to participate in repair and regeneration of damaged and/or diseased tissues. Mesenchymal stem cells have been among the most studied adult stem cells for the treatment of a variety of conditions, including wound healing.

AREAS COVERED

Mesenchymal stem cell features potentially beneficial to cutaneous wound healing applications are reviewed.

EXPERT OPINION

Given their potential for in vitro expansion and immune modulatory effects, both autologous and allogeneic mesenchymal stem cells appear to be well suited as wound healing therapies. Allogeneic mesenchymal stem cells derived from young healthy donors could have particular advantage over autologous sources where age and systemic disease can be significant factors.

Central nervous system agents for ischemic stroke: neuroprotection mechanisms

Stroke is the third leading cause of mortality and disability in the United States. Ischemic stroke constitutes 85% of all stroke cases. However, no effective treatment has been found to prevent damage to the brain in such cases except tissue plasminogen activator with narrow therapeutic window, and there is an unmet need to develop therapeutics for neuroprotection from ischemic stroke. Studies have shown that mechanisms including apoptosis, necrosis, inflammation, immune modulation, and oxidative stress and mediators such as excitatory amino acids, nitric oxide, inflammatory mediators, neurotransmitters, reactive oxygen species, and withdrawal of trophic factors may lead to the development of the ischemic cascade. Hence, it is essential to develop neuroprotective agents targeting either the mechanisms or the mediators leading to development of ischemic stroke. This review focuses on central nervous system agents targeting these biochemical pathways and mediators of ischemic stroke, mainly those that counteract apoptosis, inflammation, and oxidation, and well as glutamate inhibitors which have been shown to provide neuroprotection in experimental animals. All these agents have been shown to improve neurological outcome after ischemic insult in experimental animals in vivo, organotypic brain slice/acute slice ex vivo, and cell cultures in vitro and may therefore aid in preventing long-term morbidity and mortality associated with ischemic stroke.