Stem cells exert therapeutic effects against ischemic stroke via transplantation of exogenous stem cells or stimulation of endogenous stem cells within the neurogenic niches of subventricular zone and subgranular zone, or recruited from the bone marrow through peripheral circulation. In this paper, we review the different sources of stem cells that have been tested in animal models of stroke. In addition, we discuss specific mechanisms of action, in particular neurovascular repair by endothelial progenitor cells, as key translational research for advancing the clinical applications of stem cells for ischemic stroke.
Cerebral ischemia; Cell-based therapies; Vasculature; Blood brain barrier; Endothelial cells
Stem cell therapy for adult stroke has reached limited clinical trials. Here, we provide translational research guidance on stem cell therapy for neonatal hypoxic-ischemic brain injury requiring a careful consideration of clinically relevant animal models, feasible stem cell sources, and validated safety and efficacy endpoint assays, as well as a general understanding of modes of action of this cellular therapy. To this end, we refer to existing translational guidelines, in particular the recommendations outlined in the consortium of academicians, industry partners and regulators called Stem cell Therapeutics as an Emerging Paradigm for Stroke or STEPS. Although the STEPS guidelines are directed at enhancing the successful outcome of cell therapy in adult stroke, we highlight overlapping pathologies between adult stroke and neonatal hypoxic-ischemic brain injury. We are, however, cognizant that the neonatal hypoxic-ischemic brain injury displays disease symptoms distinct from adult stroke in need of an innovative translational approach that facilitates the entry of cell therapy in the clinic. Finally, insights into combination therapy are provided with the vision that stem cell therapy may benefit from available treatments, such as hypothermia, already being tested in children diagnosed with hypoxic-ischemic brain injury.
cerebral palsy; stem cells; hypothermia; neurorestoration; translational; consortium; combination therapy
We advance Baby STEPS or Stem cell Therapeutics as an Emerging Paradigm for Stroke as a guide in facilitating the critical evaluation in the laboratory of the safety and efficacy of cell therapy for neonatal encephalopathy. The need to carefully consider the clinical relevance of the animal models in mimicking human neonatal brain injury, selection of the optimal stem cell donor, and the application of functional outcome assays in small and large animal models serve as the foundation for preclinical work and beginning to understand the mechanism of this cellular therapy. The preclinical studies will aid our formulation of a rigorous human clinical trial which encompasses not only efficacy testing but also monitoring of safety indices and demonstration of mechanisms of action. This schema forms the basis of Baby STEPS. Our goal is to resonate the urgent call to enhance the successful translation of cell therapy from the laboratory to the clinic.
Long-term consequences of traumatic brain injury (TBI) are closely associated with the development of severe psychiatric disorders, such as post-traumatic stress disorder (PTSD), yet preclinical studies on pathological changes after combined TBI with PTSD are lacking. In the present in vivo study, we assessed chronic neuroinflammation, neuronal cell loss, cell proliferation and neuronal differentiation in specific brain regions of adult Sprague-Dawley male rats following controlled cortical impact model of moderate TBI with or without exposure to PTSD. Eight weeks post-TBI, stereology-based histological analyses revealed no significant differences between sham and PTSD alone treatment across all brain regions examined, whereas significant exacerbation of OX6-positive activated microglial cells in the striatum, thalamus, and cerebral peduncle, but not cerebellum, in animals that received TBI alone and combined TBI-PTSD compared with PTSD alone and sham treatment. Additional immunohistochemical results revealed a significant loss of CA3 pyramidal neurons in the hippocampus of TBI alone and TBI-PTSD compared to PTSD alone and sham treatment. Further examination of neurogenic niches revealed a significant downregulation of Ki67-positive proliferating cells, but not DCX-positive neuronally migrating cells in the neurogenic subgranular zone and subventricular zone for both TBI alone and TBI-PTSD compared to PTSD alone and sham treatment. Comparisons of levels of neuroinflammation and neurogenesis between TBI alone and TBI+PTSD revealed that PTSD did not exacerbate the neuropathological hallmarks of TBI. These results indicate a progressive deterioration of the TBI brain, which, under the conditions of the present approach, was not intensified by PTSD, at least within our time window and within the examined areas of the brain. Although the PTSD manipulation employed here did not exacerbate the pathological effects of TBI, the observed long-term inflammation and suppressed cell proliferation may evolve into more severe neurodegenerative diseases and psychiatric disorders currently being recognized in traumatized TBI patients.
Background and Purpose
Recent evidence has supported the neuroprotective effect of bpV (pic), an inhibitor of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), in models of ischemic stroke. However, whether PTEN inhibitors improve long-term functional recovery after traumatic brain injury (TBI) and whether PTEN affects blood brain barrier (BBB) permeability need further elucidation. The present study was performed to address these issues.
Adult Sprague-Dawley rats were subjected to fluid percussion injury (FPI) after treatment with a well-established PTEN inhibitor bpV (pic) or saline starting 24 h before FPI. Western blotting, real-time quantitative PCR, or immunostaining was used to measure PTEN, p-Akt, or MMP-9 expression. We determined the presence of neuron apoptosis by TUNEL assay. Evans Blue dye extravasation was measured to evaluate the extent of BBB disruption. Functional recovery was assessed by the neurological severity score (NSS), and Kaplan-Meier analysis was used for survival analysis.
PTEN expression was up-regulated after TBI. After bpV (pic) treatment, p-Akt was also up-regulated. We found that bpV (pic) significantly decreased BBB permeability and reduced the number of TUNEL-positive cells. We further demonstrated that PTEN inhibition improved neurological function recovery in the early stage after TBI.
These data suggest that treatment with the PTEN inhibitor bpV (pic) has a neuroprotective effect in TBI rats.
Traumatic brain injury (TBI) has become a signature wound of the wars in Iraq and Afghanistan. Many American soldiers, even those undiagnosed but likely suffering from mild TBI, display Alzheimer's disease (AD)-like cognitive impairments, suggesting a pathological overlap between TBI and AD. This study examined the cognitive and neurohistological effects of TBI in presymptomatic APP/PS1 AD-transgenic mice. AD mice and non-transgenic (NT) mice received an experimental TBI on the right parietal cortex using the controlled cortical impact model. Animals were trained in a water maze task for spatial memory before TBI, and then reevaluated in the same task at two and six weeks post-TBI. The results showed that AD mice with TBI made significantly more errors in the task than AD mice without TBI and NT mice regardless of TBI. A separate group of AD mice and NT mice were evaluated neurohistologically at six weeks after TBI. The number of extracellular beta-amyloid (Aβ)-deposits significantly increased by at least one fold in the cortex of AD mice that received TBI compared to the NT mice that received TBI or the AD and NT mice that underwent sham surgery. A significant decrease in MAP2 positive cells, indicating neuronal loss, was observed in the cortex of both the AD and NT mice that received TBI compared to the AD and NT mice subjected to sham surgery. Similar changes in extracellular Aβ deposits and MAP2 positive cells were also seen in the hippocampus. These results demonstrate for the first time that TBI precipitates cognitive impairment in presymptomatic AD mice, while also confirming extracellular Aβ deposits following TBI. The recognition of this pathological link between TBI and AD should aid in developing novel treatments directed at abrogating cellular injury and extracellular Aβ deposition in the brain.
This study aims to create a convenient reference for both clinicians and researchers so that vis-à-vis comparisons between brain disorders can be made quickly and accurately. We report here the incidence and prevalence of the major adult-onset brain disorders in the United States using a meta-analysis approach.
Material and Methods
Epidemiological figures were collected from the most recent, reliable data available in the research literature. Population statistics were based on the most recent census from the US Census Bureau. Extrapolations were made only when necessary. The most current epidemiological studies for each disorder were chosen. All effort was made to use studies based on national cohorts. Studies reviewed were conducted between 1950 and 2009. The data of the leading studies for several neurological studies was compiled in order to obtain the most accurate extrapolations. Results were compared to commonly accepted values in order to evaluate validity.
It was found that 6.75% of the American adult population is afflicted with brain disorders. This number was eclipsed by the 8.02% of Floridians with brain disorders, which is due to the large aged population residing in the state.
There was a noticeable lack of epidemiological data concerning adult-onset brain disorders. Since approximately 1 out of every 7 households is affected by brain disorders, increased research into this arena is warranted.
Emerging technologies have gained notoriety as a catalyst of socioeconomic progress, but have also inspired a revolution in ethics. Here, we provide an overview of ethics in stem cell-based therapies and offer a compelling argument for a need to establish an Ethics Research Consortium that will be tasked to assemble an interdisciplinary panel of experts who will apply ethical principles to analyze the social merit relative to the economic incentives of this emerging technology. Milestone studies on cell therapy in Parkinson’s disease and stroke over the last two decades were the focus of this commentary. The major criterion for study selection was based on public opinion, scientific discussion, and government reactions generated by these pioneering studies. Original data from the selected studies are presented. Interpretation and discussion of data captured the prevailing views of the public and scientific community, as well as the government regulatory and oversight decisions (i.e., ban on embryonic stem cell research funding). Lessons learned from two decades of cell-based therapies indicate that poor management of the public discourse of ethics concerning emerging technologies might have contributed to misperceptions within both the public and the research community that have hindered the progress of scientific innovation and even delayed the clinical application of potentially life-saving treatments to critically ill patients. We propose the creation of a Consortium that will evaluate how these novel ethical issues in emerging technologies are addressed under current oversight and regulatory structures and where there may be gaps and need for revised or new public policy approaches.
Ethics; Embryonic stem cells; Adult stem cells; Transplantation
Stem cell-based therapies for stroke have expanded substantially over the last decade. The diversity of embryonic and adult tissue sources provides researchers with the ability to harvest an ample supply of stem cells. However, the optimal conditions of stem cell use are still being determined. Along this line of the need for optimization studies, we discuss studies that demonstrate effective dose, timing, and route of stem cells. We recognize that stem cell derivations also provide uniquely individual difficulties and limitations in their therapeutic applications. This review will outline the current knowledge, including benefits and challenges, of the many current sources of stem cells for stroke therapy.
stem cells; stroke; cerebral ischemia; transplantation
In the process of neurogenesis, neural progenitor cells (NPCs) cease dividing and differentiate into postmitotic neurons that grow dendrites and an axon, become excitable, and establish synapses with other neurons. Mitochondrial biogenesis and aerobic metabolism provide energy substrates required to support the differentiation, growth and synaptic activity of neurons. Mitochondria may also serve signaling functions and, in this regard, it was recently reported that mitochondria can generate rapid bursts of superoxide (superoxide flashes), the frequency of which changes in response to environmental conditions and signals including oxygen levels and Ca2+ fluxes. Here we show that the frequency of mitochondrial superoxide flashes increases as embryonic cerebral cortical neurons differentiate from NPCs, and provide evidence that the superoxide flashes serve a signaling function that is critical for the differentiation process. The superoxide flashes are mediated by mitochondrial permeability transition pore (mPTP) opening, and pharmacological inhibition of the mPTP suppresses neuronal differentiation. Moreover, superoxide flashes and neuronal differentiation are inhibited by scavenging of mitochondrial superoxide. Conversely, manipulations that increase superoxide flash frequency accelerate neuronal differentiation. Our findings reveal a regulatory role for mitochondrial superoxide flashes, mediated by mPTP opening, in neuronal differentiation.
In this study, we investigated the dog placenta as a viable source of stem cells for stroke therapy. Immunocytochemical evaluation of phenotypic markers of dog placenta cells (DPCs) cultured in proliferation and differentiation medium revealed that DPCs expressed both stem cell and neural cell markers, respectively. Co-culture with DPCs afforded neuroprotection of rat primary neural cells in a dose-dependent manner against oxygen-glucose deprivation. Subsequent in vivo experiments showed that transplantation of DPCs, in particular intravenous and intracerebral cell delivery, produced significant behavioral recovery and reduced histological deficits in ischemic stroke animals compared to those that received intra-arterial delivery of DPCs or control stroke animals. Furthermore, both in vitro and in vivo studies implicated elevated expression of heat shock protein 27 (Hsp27) as a potential mechanism of action underlying the observed therapeutic benefits of DPCs in stroke. This study supports the use of stem cells for stroke therapy and implicates a key role of Hsp27 signaling pathway in neuroprotection.
Prenatal alcohol exposure can lead to fetal alcohol spectrum disorder (FASD) and associated behavioral impairments that may be linked to disruptions in adult hippocampal neurogenesis. Social and physical enrichment has been proposed as a potential therapeutic approach toward reversing behavioral deficits associated with FASD and is also a potent stimulator of adult hippocampal neurogenesis. In the present study, we utilized a genetic fate mapping approach in nestin-CreERT2/YFP bitransgenic mice to identify the stage-specific impact of prenatal alcohol exposure on the stepwise maturation of adult hippocampal progenitors. Using a limited alcohol access “drinking-in-the-dark” model of FASD, we confirm previous findings that moderate prenatal alcohol exposure has no effect on adult neurogenesis under standard housing conditions, but abolishes the neurogenic response to enriched environment (EE). Furthermore, we demonstrate that this effect is primarily due to failed EE-mediated survival of postmitotic neurons. Finally, we demonstrate that the neurogenic deficit is associated with impaired spatial pattern recognition, as demonstrated by delayed learning of FASD-EE mice in an A–B contextual discrimination task. These results identify a potential maturational stage-specific mechanism(s) underlying impaired neurogenic function in a preclinical model of FASD, and provide a basis for testing regulatory pathways in this model through conditional and inducible manipulation of gene expression in the adult hippocampal progenitor population.
Here, we report that a unique mechanism of action exerted by stem cells in the repair of the traumatically injured brain involves their ability to harness a biobridge between neurogenic niche and injured brain site. This biobridge, visualized immunohistochemically and laser captured, corresponded to an area between the neurogenic subventricular zone and the injured cortex. That the biobridge expressed high levels of extracellular matrix metalloproteinases characterized initially by a stream of transplanted stem cells, but subsequently contained only few to non-detectable grafts and overgrown by newly formed host cells, implicates a novel property of stem cells. The transplanted stem cells manifest themselves as pathways for trafficking the migration of host neurogenic cells, but once this biobridge is formed between the neurogenic site and the injured brain site, the grafted cells disappear and relinquish their task to the host neurogenic cells. Our findings reveal that long-distance migration of host cells from the neurogenic niche to the injured brain site can be achieved through transplanted stem cells serving as biobridges for initiation of endogenous repair mechanisms. This is the first report of a stem cell-paved “biobridge”. Indeed, to date the two major schools of discipline in stem cell repair mechanism primarily support the concept of “cell replacement” and bystander effects of “trophic factor secretion”. The present novel observations of a stem cell seducing a host cell to engage in brain repair advances basic science concepts on stem cell biology and extracellular matrix, as well as provokes translational research on propagating this stem cell-paved biobridge beyond cell replacement and trophic factor secretion for the treatment of traumatic brain injury and other neurological disorders.
In pursuit of neurological therapies, the opioid system, specifically delta opioid receptors and delta opioid peptides, demonstrates promising therapeutic potential for stroke, Parkinson’s disease, and other degenerative neurological conditions. Recent studies offer strong evidence in support of the therapeutic use of delta opioid receptors, and provide insights into the underlying mechanisms of action. Delta opioid receptors have been shown to confer protective effects by mediating ionic homeostasis and activating endogenous neuroprotective pathways. Additionally, delta opioid agonists such as (D-Ala 2, D-Leu 5) enkephalin (DADLE) have been shown to decrease apoptosis and promote neuronal survival. In its entirety, the delta opioid system represents a promising target for neural therapies.
stroke; delta opioid receptors; neuroprotection; DADLE; neuronal death
Wharton’s jelly (WJ) is a gelatinous tissue within the umbilical cord that contains myofibroblast-like stromal cells. A unique cell population of WJ that has been suggested as displaying the stemness phenotype is the mesenchymal stromal cells (MSCs). Because MSCs’ stemness and immune properties appear to be more robustly expressed and functional which are more comparable with fetal than adult-derived MSCs, MSCs harvested from the “young” WJ are considered much more proliferative, immunosuppressive, and even therapeutically active stem cells than those isolated from older, adult tissue sources such as the bone marrow or adipose. The present review discusses the phenotypic characteristics, therapeutic applications, and optimization of experimental protocols for WJ-derived stem cells. MSCs derived from WJ display promising transplantable features, including ease of sourcing, in vitro expandability, differentiation abilities, immune-evasion and immune-regulation capacities. Accumulating evidence demonstrates that WJ-derived stem cells possess many potential advantages as transplantable cells for treatment of various diseases (e.g., cancer, chronic liver disease, cardiovascular diseases, nerve, cartilage and tendon injury). Additional studies are warranted to translate the use of WJ-derived stem cells for clinical applications.
umbilical cord; wharton’s jelly; mesenchymal stem cells; phenotypic characteristics; therapeutic applications; experimental protocol
The present review paper supports the approach to deliver melatonin and to target melatonin receptors for neuroprotection in stroke. We discuss laboratory evidence demonstrating neuroprotective effects of exogenous melatonin treatment and transplantation of melatonin-secreting cells in stroke. In addition, we describe a novel mechanism of action underlying the therapeutic benefits of stem cell therapy in stroke, implicating the role of melatonin receptors. As we envision the clinical entry of melatonin-based therapeutics, we discuss translational experiments that warrant consideration to reveal an optimal melatonin treatment strategy that is safe and effective for human application.
oxidative stress; stroke; neuroprotection; cerebral ischemia; melatonin
Traumatic brain injury (TBI) has become the signature wound of wars in Afghanistan and Iraq. Injury may result from a mechanical force, a rapid acceleration-deceleration movement, or a blast wave. A cascade of secondary cell death events ensues after the initial injury. In particular, multiple inflammatory responses accompany TBI. A series of inflammatory cytokines and chemokines spreads to normal brain areas juxtaposed to the core impacted tissue. Among the repertoire of immune cells involved, microglia is a key player in propagating inflammation to tissues neighboring the core site of injury. Neuroprotective drug trials in TBI have failed, likely due to their sole focus on abrogating neuronal cell death and ignoring the microglia response despite these inflammatory cells’ detrimental effects on the brain. Another relevant point to consider is the veracity of results of animal experiments due to deficiencies in experimental design, such as incomplete or inadequate method description, data misinterpretation, and reporting may introduce bias and give false-positive results. Thus, scientific publications should follow strict guidelines that include randomization, blinding, sample-size estimation, and accurate handling of all data (Landis et al., 2012). A prolonged state of inflammation after brain injury may linger for years and predispose patients to develop other neurological disorders, such as Alzheimer’s disease. TBI patients display progressive and long-lasting impairments in their physical, cognitive, behavioral, and social performance. Here, we discuss inflammatory mechanisms that accompany TBI in an effort to increase our understanding of the dynamic pathological condition as the disease evolves over time and begin to translate these findings for defining new and existing inflammation-based biomarkers and treatments for TBI.
head trauma; microglia; inflammatory response; secondary cell death; anti-inflammatory therapy; brain imaging
Neurological disorders are routinely characterized by loss of cells in response to an injury or a progressive insult. Stem cells could therefore be useful to treat these disorders.
Sources of data
Pubmed searches of recent literature.
Areas of agreement
Stem cells exhibit proliferative capacity making them ideally suited for replacing dying cells. However, instead of cell replacement therapy stem cell transplants frequently appear to work via neurotrophic factor release, immunomodulation and upregulation of endogenous stem cells.
Areas of controversy and areas timely for developing research
Many questions remain with respect to the use of stem cells as a therapy, the answers to which will vary depending on the disorder to be treated and mode of action. Whereas the potential tumorigenic capability of stem cells is a concern, most studies do not support this notion. Further determination of the optimal cell type, and whether to perform allogeneic or autologous transplants warrant investigation before the full potential of stem cells can be realized. In addition, the use of stem cells to develop disease models should not be overlooked.
mesenchymal stem cells; neural stem cells; tumorigenesis; inflammation; neurotrophic factors; cell therapy
Our understanding of biological mechanisms and treatment options for traumatic brain injury (TBI) is limited. Here, we employed quantitative real-time PCR (QRT-PCR) and immunohistochemical analyses to determine the dynamic expression of cell proliferation and apoptosis in an effort to provide insights into the therapeutic window for developing regenerative strategies for TBI. For this purpose, young adult Sprague-Dawley rats were subjected to experimental TBI using a controlled cortical impactor, then euthanized 1-48 hours after TBI for QRT-PCR and immunohistochemistry. QRT-PCR revealed that brains from TBI exposed rats initially displayed nestin mRNA expression that modestly increased as early as 1-hour post-TBI, then significantly peaked at 8 hours, but thereafter reverted to pre-TBI levels. On the other hand, caspase-3 mRNA expression was slightly elevated at 8 hours post-TBI, which did not become significantly upregulated until 48 hours. Immunofluorescent microscopy revealed a significant surge in nestin immunoreactive cells in the cortex, corpus callosum, and subventricular zone at 24 hours post-TBI, whereas a significant increase in the number of active caspase-3 immunoreactive cells was only found in the cortex and not until 48 hours. These results suggest that the injured brain attempts to repair itself via cell proliferation immediately after TBI, but that this endogenous regenerative mechanism is not sufficient to abrogate the secondary apoptotic cell death. Treatment strategies designed to amplify cell proliferation and to prevent apoptosis are likely to exert maximal benefits when initiated at the acute phase of TBI.
cell proliferation; neurogenesis; apoptosis; head trauma; nestin; caspase-3
Accumulating laboratory studies have implicated the mobilization of bone marrow (BM)-derived stem cells in brain plasticity and stroke therapy. This mobilization of bone cells to the brain is an essential concept in regenerative medicine. Over the past ten years, mounting data have shown the ability of bone marrow–derived stem cells to mobilize from BM to the peripheral blood (PB) and eventually enter the injured brain. This homing action is exemplified in BM stem cell mobilization following ischemic brain injury. Various BM-derived cells, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and very small embryonic-like cells (VSELs) have been demonstrated to exert therapeutic benefits in stroke. Here, we discuss the current status of these BM-derived stem cells in stroke therapy, with emphasis on possible cellular and molecular mechanisms of action that mediate the cells’ beneficial effects in the ischemic brain. When possible, we also discuss the relevance of this therapeutic regimen in other central nervous system (CNS) disorders.
stem cells; stroke; endogenous; homing; migration; transplantation; growth factor secretion
Endothelial progenitor cells (EPCs) correspond to a population of cells with novel properties capable of angiogenesis and vasculogenesis, thus they are likely to display unique role in the reconstitution of the blood brain barrier (BBB) after stroke. Laboratory evidence supports safety and efficacy of cell therapy for stroke, with limited clinical trials recently initiated. This lab-to-clinic ascent of cell-based therapeutics has been aided by the establishment of consortium consisting of thought-leaders from academia, industry, National Institutes of Health (NIH) and the United States Food and Drug Administration (FDA). However, there remain unanswered questions prior to realization of large-scale application of cell transplantation in patients. This review article discusses translational challenges associated in cell therapy, emphasizing the need for optimizing both safety and efficacy profiles for advancing the clinical applications of EPC transplantation for stroke patients.
Cerebral ischemia; stem cells; cell transplantation; translational research
The blood-brain barrier (BBB) has been considered as an important regulator of brain homeostasis, and its disturbance has been implicated in the onset and/or evolution of many pathological manifestations of neurodegenerative and inflammatory diseases [1, 2]. In particular, BBB breakdown has been closely associated with the primary insult, as well as the secondary cell death of stroke. Here, we review the pioneering contributions of leading scientists who have vested interest in advancing our understanding of the pivotal role of BBB in stroke, but also exploiting this knowledge in developing novel BBB-based therapeutic regimens to abrogate stroke symptoms. The study of BBB as a fundamental research theme and as a target for clinical applications in stroke can be approached in three main themes namely, basic science research, translational and clinical research, and emerging therapies for BBB repair in stroke. This mini-review captures cutting-edge discoveries establishing BBB as a central target for abetting neuroprotection and neurorestoration in stroke.
A global health problem, traumatic brain injury (TBI) is especially prevalent in the current era of ongoing world military conflicts. Its pathological hallmark is one or more primary injury foci, followed by a spread to initially normal brain areas via cascades of inflammatory cytokines and chemokines resulting in an amplification of the original tissue injury by microglia and other central nervous system immune cells. In some cases this may predispose individuals to later development of Alzheimer’s disease (AD). The inflammatory-based progression of TBI has been shown to be active in humans for up to 17 years post TBI. Unfortunately, all neuroprotective drug trials have failed, and specific treatments remain less than efficacious. These poor results might be explained by too much of a scientific focus on neurons without addressing the functions of microglia in the brain, which are at the center of proinflammatory cytokine generation. To address this issue, we provide a survey of the TBI-related brain immunological mechanisms that may promote progression to AD. We discuss these immune and microglia-based inflammatory mechanisms involved in the progression of post-trauma brain damage to AD. Flavonoid-based strategies to oppose the antigen-presenting cell-like inflammatory phenotype of microglia will also be reviewed. The goal is to provide a rationale for investigations of inflammatory response following TBI which may represent a pathological link to AD. In the end, a better understanding of neuroinflammation could open therapeutic avenues for abrogation of secondary cell death and behavioral symptoms that may mediate the progression of TBI to later AD.
traumatic brain injury; flavonoids; microglia phenotype; Alzheimer’s disease; cytokines
Stroke remains a significant unmet condition in the United States and throughout the world. To date, only approximately 3% of the population suffering an ischemic stroke benefit from the thrombolytic drug tissue Plasminogen Activator, largely due to the drug's narrow therapeutic window. The last decade has witnessed extensive laboratory studies suggesting the therapeutic potential of cell-based therapy for stroke. Limited clinical trials of cell therapy in stroke patients are currently being pursued. Bone marrow-derived stem cells are an attractive, novel transplantable cell source for stroke. There remain many unanswered questions in the laboratory before cell therapy can be optimized for transplantation in the clinical setting. Here, we discuss the various translational hurdles encountered in bringing cell therapy from the laboratory to the clinic, using STEPS (Stem Cell Therapeutics as an Emerging Paradigm for Stroke) as a guiding principle. In particular, we focus on the preclinical studies of cell transplantation in experimental stroke with emphasis on a better understanding of mechanisms of action in an effort to optimize efficacy and to build a safety profile for advancing cell therapy to the clinic. A forward looking strategy of combination therapy involving stem cell transplantation and pharmacologic treatment is also discussed.
Stroke; Endothelial progenitor cells; Cell therapy; Drug treatment; Translational research