Trophic factor secreting kidney cell lines: in vitro characterization and functional effects following transplantation in ischemic rats

Behavioral Changes in Combination Therapy of Ethanol and Modafinil on Rats Focal Cerebral Ischemia

Introduction:

Ethanol is considered as an effective agent in reducing brain stroke injury. In this study, we assessed the effects of modafinil along with ethanol as a combination therapy on behavioral function in Wistar rats.

Methods:

The right Middle Cerebral Artery Occlusion (MCAO) was performed and the rats were divided into nine groups (n=8 per group). The animal groups in this study were as follows: 1. MCAO control group (ischemia without treatment); 2. Vehicle group; 3. Modafinil group that was randomly subdivided into three groups receiving different doses of modafinil (10, 30, and 100 mg/kg) for 7 days before MCAO; 4. Ethanol group receiving 1.5 g/kg ethanol at the time of reperfusion; 5. Modafinil + ethanol group that was further subdivided into three groups receiving modafinil at different doses (10, 30, and 100 mg/kg) for 7 days before MCAO and ethanol at the time of reperfusion. The motor behavior was measured using the Garcia test 24, 48, and 72 h after the ischemia, and the elevated body swing test was performed 48 and 72 h after the ischemia. The anxiety and locomotor activity were analyzed by open field test 48 and 72 h post-ischemia.

Results:

The results showed that the neurological deficit score, locomotor activity, and unexpected thigmotaxis (anxiety) in the ethanol, modafinil (in a dose-dependent manner), and ethanol+modafinil treatment groups were significantly higher than the MCAO control group.

Conclusion:

It seems that the combination therapy of modafinil (100 mg/kg) and ethanol (1.5 g/kg) significantly enhanced neuroprotection via an improvement in locomotor activity and neurological functions.

Anti-inflammatory Effects of Traditional Chinese Medicines on Preclinical in vivo Models of Brain Ischemia-Reperfusion-Injury: Prospects for Neuroprotective Drug Discovery and Therapy

Acquired brain ischemia-and reperfusion-injury (IRI), including both Ischemic stroke (IS) and Traumatic Brain injury (TBI), is one of the most common causes of disability and death in adults and represents a major burden in both western and developing countries worldwide. China’s clinical neurological therapeutic experience in the use of traditional Chinese medicines (TCMs), including TCM-derived active compounds, Chinese herbs, TCM formulations and decoction, in brain IRI diseases indicated a trend of significant improvement in patients’ neurological deficits, calling for blind, placebo-controlled and randomized clinical trials with careful meta-analysis evaluation. There are many TCMs in use for brain IRI therapy in China with significant therapeutic effects in preclinical studies using different brain IRI-animal. The basic hypothesis in this field claims that in order to avoid the toxicity and side effects of the complex TCM formulas, individual isolated and identified compounds that exhibited neuroprotective properties could be used as lead compounds for the development of novel drugs. China’s efforts in promoting TCMs have contributed to an explosive growth of the preclinical research dedicated to the isolation and identification of TCM-derived neuroprotective lead compounds. Tanshinone, is a typical example of TCM-derived lead compounds conferring neuroprotection toward IRI in animals with brain middle cerebral artery occlusion (MCAO) or TBI models. Recent reports show the significance of the inflammatory response accompanying brain IRI. This response appears to contribute to both primary and secondary ischemic pathology, and therefore anti-inflammatory strategies have become popular by targeting pro-inflammatory and anti-inflammatory cytokines, other inflammatory mediators, reactive oxygen species, nitric oxide, and several transcriptional factors. Here, we review recent selected studies and discuss further considerations for critical reevaluation of the neuroprotection hypothesis of TCMs in IRI therapy. Moreover, we will emphasize several TCM’s mechanisms of action and attempt to address the most promising compounds and the obstacles to be overcome before they will enter the clinic for IRI therapy. We hope that this review will further help in investigations of neuroprotective effects of novel molecular entities isolated from Chinese herbal medicines and will stimulate performance of clinical trials of Chinese herbal medicine-derived drugs in IRI patients.

Easy and Efficient Cell Tagging with Block Copolymer-Based Contrast Agents for Sensitive MRI Detection in Vivo

Superparamagnetic iron oxide nanoparticles (MNPs) together with magnetic resonance imaging (MRI) are the preferred tools for monitoring the fate and biodistribution of administered cells in stem cell therapy studies. Commercial MNPs need transfection agents and long incubation times for sufficient cell labeling and further in vivo cell detection. In this work, we have synthesized MNPs coated with pluronic F127 and tetronic 908, and validated their applicability as contrast agents for MRI cell detection on two different cell types: rat mesenchymal stem cells (MSCs) and multipotent neural progenitor cell line from mice (C17.2). No transfection agent was needed for a complete MNP internalization, and the uptake was only dependent on MNP concentration in medium and limited on the incubation time. By combining in vivo MRI and ex vivo histology microscopy, we have demonstrated the MRI signal detected corresponded exclusively to labeled cells and not to free particles. Pluronic F127- and tetronic 908-coated MNPs represent promising contrast agents for stem cell tracking due to their ease of use in preparation, their efficiency for cell labeling, and their high sensitivity for in vivo cell detection.

Stem cell transplantation therapy for multifaceted therapeutic benefits after stroke

One of the exciting advances in modern medicine and life science is cell-based neurovascular regeneration of damaged brain tissues and repair of neuronal structures. The progress in stem cell biology and creation of adult induced pluripotent stem (iPS) cells has significantly improved basic and pre-clinical research in disease mechanisms and generated enthusiasm for potential applications in the treatment of central nervous system (CNS) diseases including stroke. Endogenous neural stem cells and cultured stem cells are capable of self-renewal and give rise to virtually all types of cells essential for the makeup of neuronal structures. Meanwhile, stem cells and neural progenitor cells are well-known for their potential for trophic support after transplantation into the ischemic brain. Thus, stem cell-based therapies provide an attractive future for protecting and repairing damaged brain tissues after injury and in various disease states. Moreover, basic research on naïve and differentiated stem cells including iPS cells has markedly improved our understanding of cellular and molecular mechanisms of neurological disorders, and provides a platform for the discovery of novel drug targets. The latest advances indicate that combinatorial approaches using cell based therapy with additional treatments such as protective reagents, preconditioning strategies and rehabilitation therapy can significantly improve therapeutic benefits. In this review, we will discuss the characteristics of cell therapy in different ischemic models and the application of stem cells and progenitor cells as regenerative medicine for the treatment of stroke.

T155g-Immortalized Kidney Cells Produce Growth Factors and Reduce Sequelae of Cerebral Ischemia

Fetal rat kidney cells produce high levels of glial-derived neurotrophic factor (GDNF) and exert neuroprotective effects when transplanted into the brain in animal models of Parkinson's disease and stroke. The purpose of the present experiment was to produce kidney cell lines that secrete GDNF. Genes encoding two truncated N-terminal fragments of SV40 large T antigen, T155g and T155c, which does not code for small t antigen, were used. T155g was transduced into E17 cultured fetal Sprague-Dawley rat kidney cortex cells using a plasmid vector, and T155c was transduced with a plasmid and a retroviral vector. Sixteen clones were isolated from cultures transfected with the T155g-expressing plasmid. No cell lines were obtained with T155c. Four clones produced GDNF at physiological concentrations ranging from 55 to 93 pg/ml of medium. These four clones were transplanted into the ischemic core or penumbra of rats that had undergone middle cerebral artery occlusion (MCAO). Three of the four clones reduced the volume of infarction and the behavioral abnormalities normally resulting from MCAO. Blocking experiments with antibodies to GDNF and platelet-derived growth factor (PDGF) suggested that these growth factors contributed only minimally to the reduction in infarct volume and behavioral abnormality. These cell lines may be useful for intracerebral transplantation in animal models of brain injury, stroke, or Parkinson's disease.

Intracerebral Xenotransplantation of GFP Mouse Bone Marrow Stromal Cells in Intact and Stroke Rat Brain: Graft Survival and Immunologic Response

The present study characterized survival and immunologic response of bone marrow stromal cells (BMSCs) following transplantation into intact and stroke brains. In the first study, intrastriatal transplantation of BMSC (60,000 in 3 μl) or vehicle was performed in normal adult Sprague-Dawley male rats that subsequently received daily cyclosporin A (CsA, 10 mg/kg, IP in 3 ml) or vehicle (olive oil, similar volume) starting on day of surgery up to 3 days posttransplantation. Animals were euthanized at 3 or 30 days posttransplantation and brains were processed either for green fluorescent protein (GFP) microscopy or flow cytometry (FACS). Both GFP epifluorescence and FACS scanning revealed GFP+ BMSCs in both groups of transplanted rats with or without CsA, although significantly increased (1.6- to 3-fold more) survival of GFP+ BMSCs was observed in the immunosuppressed animals. Further histologic examination revealed widespread dispersal of BMSCs away from the graft core accompanied by many long outgrowth processes in non-CsA-transplanted animals, whereas a very dense graft core, with cells expressing only sporadic short outgrowth processes, was observed in CsA-transplanted animals. There were no detectable GFP+ BMSCs in nontrans-planted rats that received CsA or vehicle. Immunologic response via FACS analysis revealed a decreased presence of cytotoxic cells, characterized by near complete absence of CD8+ cells, and lack of activation depicted by low CD69 expression in CsA-treated transplanted animals. In contrast, elevated levels of CD8+ cells and increased activation of CD69 expression were observed in transplanted animals that received vehicle alone. CD4+ helper cells were almost nondetectable in transplanted rats that received CsA, but also only minimally elevated in transplanted rats that received vehicle. Nontransplanted rats that received either CsA or vehicle displayed very minimal detectable levels of all three lymphocyte markers. In the second study, a new set of male Sprague-Dawley rats initially received bilateral stereotaxic intrastriatal transplantation of BMSCs and 3 days after were subjected to unilateral transient occlusion of middle cerebral artery. The animals were allowed to survive for 3 days after stroke without CsA immunosuppression. Epifluorescence microscopy revealed significantly higher (5-fold more) survival of transplanted GFP+ BMSCs in the stroke striatum compared with the intact striatum. The majority of the grafts remained within the original dorsal striatal transplant site, characterized by no obvious migration in intact striatum, but with long-distance migration along the ischemic penumbra in the stroke striatum. Moreover, FACS scanning analyses revealed low levels of immunologic response of grafted BMSCs in both stroke and intact striata. These results, taken together, suggest that xenotransplantation of mouse BMSCs into adult rats is feasible. Immunosuppression therapy can enhance xenograft survival and reduce graft-induced immunologic response; however, in the acute phase posttransplantation, BMSCs can survive in intact and stroke brain, and may even exhibit long-distance migration and increased outgrowth processes without immunosuppression.

Transplantation of Fetal Kidney Cells: Neuroprotection and Neuroregeneration

Various trophic factors in the transforming growth factor-β (TGF-β) superfamily have been reported to have neuroprotective and neuroregenerative effects. Intracerebral administration of glial cell line-derived neurotrophic factor (GDNF) or bone morphogenetic proteins (BMPs), both members of the TGF-β family, reduce ischemia- or 6-hydroxydopamine (6-OHDA)-induced injury in adult rat brain. Because BMPs and GDNF are highly expressed in fetal kidney cells, transplantation of fetal kidney tissue could serve as a cellular reservoir for such molecules and protect against neuronal injury induced by ischemia, neurotoxins, or reactive oxygen species. In this review, we discuss preclinical evidence for the efficacy of fetal kidney cell transplantation in neuroprotection and regeneration models.

Elevated body swing test after focal cerebral ischemia in rodents: methodological considerations

Background

The elevated body swing test (EBST) is a behavioral test used to evaluate experimental stroke in rodents. The basic idea is that when the animal is suspended vertically by the tail, it will swing its head laterally to the left or right depending on lesion side. In a previous study from our lab using the EBST after middle cerebral artery occlusion (MCAo), rats swung contralateral to the infarct day 1 post-MCAo, but ipsilateral day 3 post-MCAo. This shift was unexpected and prompted us to perform the present study. First, the literature was systematically reviewed to elucidate whether a similar shift had been noticed before, and if consensus existed regarding swing direction. Secondly, an experiment was conducted to systematically investigate the suggested behavior. Eighty-three adult male and female Sprague–Dawley rats were subjected to MCAo or sham surgery and the EBST was performed up to 7 days after the lesion.

Results

Both experimentally and through systematic literature review, the present study shows that the direction of biased swing activity in the EBST for rodents after cerebral ischemia can differ and even shift over time in some situations. The EBST curve for females was significantly different from that of males after the same occlusion time (p = 0.023).

Conclusions

This study highlights the importance of adequate reporting of behavioral tests for lateralization and it is concluded that the EBST cannot be recommended as a test for motor asymmetry after MCAo in rats.

Experimental models of brain ischemia: a review of techniques, magnetic resonance imaging, and investigational cell-based therapies

Stroke continues to be a significant cause of death and disability worldwide. Although major advances have been made in the past decades in prevention, treatment, and rehabilitation, enormous challenges remain in the way of translating new therapeutic approaches from bench to bedside. Thrombolysis, while routinely used for ischemic stroke, is only a viable option within a narrow time window. Recently, progress in stem cell biology has opened up avenues to therapeutic strategies aimed at supporting and replacing neural cells in infarcted areas. Realistic experimental animal models are crucial to understand the mechanisms of neuronal survival following ischemic brain injury and to develop therapeutic interventions. Current studies on experimental stroke therapies evaluate the efficiency of neuroprotective agents and cell-based approaches using primarily rodent models of permanent or transient focal cerebral ischemia. In parallel, advancements in imaging techniques permit better mapping of the spatial-temporal evolution of the lesioned cortex and its functional responses. This review provides a condensed conceptual review of the state of the art of this field, from models and magnetic resonance imaging techniques through to stem cell therapies.

ESTROGEN REPLACEMENT THERAPY FOR STROKE

Stroke is the third most common cause of death and severe disability among Western populations. Overall, the incidence of stroke is uniformly higher in men than in women. Stroke is rare in women during the reproductive years, and rapidly increases after menopause, strongly suggesting that estrogen (E2) plays an important role in the prevention of stroke. Ongoing studies are currently evaluating both the benefits and risks associated with E2 replacement therapy and hormone replacement therapy in stroke. Equally important is the role of E2 receptor (ER), as studies indicate that ER populations in several tissue sites may significantly change during stress and aging. Such changes may affect the patient's susceptibility to neurological disorders including stroke, and greatly affect the response to selective E2 receptor modulators (SERMs). Replacement therapies may be inefficient with low ER levels. The goal of this review paper is to discuss an animal model that will allow investigations of the potential therapeutic effects of E2 and its derivatives in stroke. We hypothesize that E2 neuroprotection is, in part, receptor mediated. This hypothesis is a proof of principle approach to demonstrate a role for specific ER subtypes in E2 neuroprotection. To accomplish this, we use a retroviral mediated gene transfer strategy that express subtypes of the ER gene in regions of the rat brain most susceptible to neuronal damage, namely the striatum and cortex. The animal model is exposed to experimental stroke conditions involving middle cerebral artery occlusion (MCAo) method, and eventually the extent of neuronal damage will be evaluated. A reduction in neuronal damage is expected when E2 is administered with specific ER subtypes. From this animal model, an optimal E2 dose and treatment regimen can be determined. The animal model can help identify potential E2-like therapeutics in stroke, and screen for beneficial or toxic additives present in commercial E2 preparations that are currently available. Such studies will be informative in designing drug therapies for stroke.

Role of inflammation and its mediators in acute ischemic stroke

Inflammation plays an important role in the pathogenesis of ischemic stroke and other forms of ischemic brain injury. Increasing evidence suggests that inflammatory response is a double-edged sword, as it not only exacerbates secondary brain injury in the acute stage of stroke but also beneficially contributes to brain recovery after stroke. In this article, we provide an overview on the role of inflammation and its mediators in acute ischemic stroke. We discuss various pro-inflammatory and anti-inflammatory responses in different phases after ischemic stroke and the possible reasons for their failures in clinical trials. Undoubtedly, there is still much to be done in order to translate promising pre-clinical findings into clinical practice. A better understanding of the dynamic balance between pro- and anti-inflammatory responses and identifying the discrepancies between pre-clinical studies and clinical trials may serve as a basis for designing effective therapies.

Transplantation for stroke

Stroke is the most common cause of disability in the United States, and one of the leading causes of mortality and disability in the world. The hope that damage to the CNS can be reversed or at least ameliorated is the central idea behind the research into neural repair. The ultimate repair for the brain should restore the entire lost structure and it's function. However, partial benefit is possible from addressing some of the needs of the injured brain. These partial solutions are the basis of current research into brain repair after stroke. An opportunity arises for two kinds of intervention: (1) replacement of neurons; (2) support of existing neurons, to prevent excessive degeneration and promote rewiring and plasticity. Transplantation for stroke in the rat model was regularly reported starting in 1992, demonstrating graft survival and even evidence of connection with the host brain. These studies determined several parameters for future work in stroke models, but ultimately had limited efficacy and did not progress to clinical experiments. A variety of cell types have been tried for restoration of brain function after stroke, mostly in rodent models. Human fetal cells had shown some promise in clinical studies for the treatment of Parkinson's disease. The technical and ethical difficulties associated with these cells promoted a search for alternatives. These include porcine fetal cells, human cultured stem cells, immortalized cell lines, marrow stromal cells, Sertoli cells pineal cells, and other sources. Human clonal cell lines have few ethical limitations, but some questions remain regarding their safety and efficacy. Autologous somatic stem cells are a very attractive source--there are no ethical concerns and graft rejection is not an issue. However, it is not clear that somatic cells can are plastic enough and can be safely induced to a neural fate. Restorative treatment for stroke is a new field of study. Naturally, new ideas abound and many strategies have been suggested and tried. Methods and controversies abound, and include: local delivery of cells to the area of the stroke versus grafting to an area of the brain far removed form the stroke; cell therapy for reconstitution of structure and function versus use of cell grafts to support intrinsic repair and recovery mechanisms; intravascular administration of bone marrow or other stem cells; and combination grafts, or co-grafting of several cell types or cells and other substances. The various strategies address the issue of restorative treatments form different perspectives. Some interventions occur early after stroke, or are intended to preserve existing neural structures. For example, treatment strategies that aim to provide trophic support may demonstrate early beneficial results. Other strategies aim for growth and integration of new neurons to replace those lost after stroke. In this case, early beneficial results are not likely. Functional integration of grafted neurons, if it can ever happen, is likely to require training and exercise of the appropriate capacities. Further advances in preclinical studies of neural transplantation will require improved animal models with increased sensitivity to subtle behavioral and imaging changes. Non-human primate models have been established and may increase in importance as a phase before clinical trials. The future of brain repair for stroke is likely to require some form of combination therapy designed to replace the lost cells and supporting structure, attract new blood supply, support and enhance intrinsic repair and plasticity mechanisms.

Melatonin-based therapeutics for neuroprotection in stroke

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.

Investigational therapies for ischemic stroke: neuroprotection and neurorecovery

Stroke is one of the leading causes of death and disability worldwide. Current treatment strategies for ischemic stroke primarily focus on reducing the size of ischemic damage and rescuing dying cells early after occurrence. To date, intravenous recombinant tissue plasminogen activator is the only United States Food and Drug Administration approved therapy for acute ischemic stroke, but its use is limited by a narrow therapeutic window. The pathophysiology of stroke is complex and it involves excitotoxicity mechanisms, inflammatory pathways, oxidative damage, ionic imbalances, apoptosis, angiogenesis, neuroprotection, and neurorestoration. Regeneration of the brain after damage is still active days and even weeks after a stroke occurs, which might provide a second window for treatment. A huge number of neuroprotective agents have been designed to interrupt the ischemic cascade, but therapeutic trials of these agents have yet to show consistent benefit, despite successful preceding animal studies. Several agents of great promise are currently in the middle to late stages of the clinical trial setting and may emerge in routine practice in the near future. In this review, we highlight select pharmacologic and cell-based therapies that are currently in the clinical trial stage for stroke.

Transplantation of rat synapsin-EGFP-labeled embryonic neurons into the intact and ischemic CA1 hippocampal region: distribution, phenotype, and axodendritic sprouting

A major limitation of neural transplantation studies is assessing the degree of host-graft interaction. In the present study, rat hippocampal/cortical embryonic neurons (E18) were infected with a lentivirus encoding enhanced green fluorescent protein (GFP) under control of the neuron-specific synapsin promoter, thus permitting robust identification of labeled neurons after in vivo grafting. Two weeks after transient forebrain ischemia or sham-surgery, GFP-expressing neurons were transplanted into CA1 hippocampal regions in immunosuppressed adult Wistar rats. The survival, distribution, phenotype, and axonal projections of GFP-immunoreactive (IR) positive transplanted neurons were evaluated in the sham-operated and ischemia- damaged CA1 hippocampal regions 4, 8, and 12 weeks after transplantation. In both experimental groups, we observed that the main phenotype of host-derived afferents projecting towards grafted GFP-IR neurons as well as transplant-derived GFP-IR efferents were glutamatergic in both animal groups. GFP axonal projections were seen in the nucleus accumbens, septal nuclei, and subiculum-known target areas of CA1 pyramidal neurons. Compared to sham-operated animals, GFP-IR neurons grafted into the ischemia-damaged CA1 migrated more extensively throughout a larger volume of host tissue, particularly in the stratum radiatum. Moreover, enhanced axonal sprouting and neuronal plasticity of grafted cells were evident in the hippocampus, subiculum, septal nuclei, and nucleus accumbens of the ischemia-damaged rats. Our study suggests that the adult rat brain retains some capacity to direct newly sprouting axons of transplanted embryonic neurons to the correct targets and that this capacity is enhanced in previously ischemia-injured forebrain.

Cell-based therapy for stroke

Current treatments for stroke, such as the use of thrombolytic agents, are often limited by a narrow therapeutic time window. However, the regeneration of the brain after damage is still active days even weeks after stroke occurs, which might provide a second window for treatment. Cell-based therapy can be categorized into two strategies. One is transplantation of exogenous cells into the injured brain to replace the lost cells or support the remaining cells. The other strategy is to enhance the proliferation, differentiation, migration of endogenous stem or progenitor cells. Recent development in adult stem cell research and advancement in the induction of pluripotent stem cells from somatic adult cells provide a tremendous opportunity for transplantation therapy. Understanding the mechanisms and regulations involved in the endogenous neurogenesis will also help develop novel therapeutic interventions to promote neurogenesis and functional recovery in stroke. This review describes up-to-date progresses in cell-based therapy for the treatment of stroke.

Changes in Host Blood Factors and Brain Glia Accompanying the Functional Recovery after Systemic Administration of Bone Marrow Stem Cells in Ischemic Stroke Rats

In this study, we examined the effects of systemic administration of rat or human bone marrow stromal stem cells (MSC) at early and later times following middle cerebral artery occlusion (MCAO) on blood cytokines/growth factors, brain glia, and motor behavior in rats. Rats were tail vein injected with rat (r) and human (h) MSCs at 1 or 7 days post-MCAO. In some rats ( N = 4) MSCs isolated from transgenic GFP rats were used to track the migration of cells peripherally and centrally at 2.5 and 28 days. Motor behavior was assessed using the modified Neurological Severity Score/climbing test at various time points before and after MCAO and transplantation. Prior to sacrifice at 1, 7, or 28 days post-MCAO, blood serum was collected for cytokine array analysis. Brains were analyzed for markers of activated microglia (CD11) and reactive astrocytes (GFAP). Administration of either allogeneic (rMSCs) or xenogeneic (hMSCs) stem cells produced a significant recovery of motor behavior after MCAO, with cells delivered at 1 day having greater effect than those at 7 days. Correlated with recovery was an amplification in activated microglia, reactive astrocytes, and new blood vessels in the infarct region, resulting in greater preservation in brain integrity. Concomitantly, expression of blood cytokines/chemokines (IL-13, MMP2, MIP) and growth factors/receptors (VEGF, neuropilin, EPOR, TROY, NGFR, RAGE) were modified following MSC administration. Because only rare GFP-labeled MSCs were observed in the brain, these effects did not depend on the central incorporation of stem cells. The early systemic administration of allogeneic or xenogeneic MSCs soon after experimental stroke produces a structural/functional recovery in the brain which is correlated with an increase in activated brain glia and changes in circulating cytokines and growth factors. Stem cells therefore induce an important neuroprotective and/or regenerative response in the host organism.

Stem cells for ischemic brain injury: a critical review

No effective therapy is currently available to promote recovery following ischemic stroke. Stem cells have been proposed as a potential source of new cells to replace those lost due to central nervous system injury, as well as a source of trophic molecules to minimize damage and promote recovery. We undertook a detailed review of data from recent basic science and preclinical studies to investigate the potential application of endogenous and exogenous stem cell therapies for treatment of cerebral ischemia. To date, spontaneous endogenous neurogenesis has been observed in response to ischemic injury, and can be enhanced via infusion of appropriate cytokines. Exogenous stem cells from multiple sources can generate neural cells that survive and form synaptic connections after transplantation in the stroke-injured brain. Stem cells from multiple sources cells also exhibit neuroprotective properties that may ameliorate stroke deficits. In many cases, functional benefits observed are likely independent of neural differentiation, although the exact mechanisms remain poorly understood. Future studies of neuroregeneration will require the demonstration of function in endogenously born neurons following focal ischemia. Further, methods are currently lacking to demonstrate definitively the therapeutic effect of newly introduced neural cells. Increased plasticity following stroke may facilitate the functional integration of new neurons, but the loss of appropriate guidance cues and supporting architecture in the infarct cavity will likely impede the restoration of lost circuitry. Thus careful investigation of the mechanisms underlying trophic benefits will be essential. Evidence to date suggests that continued development of stem cell therapies may ultimately lead to viable treatment options for ischemic brain injury.

An immortalized rat ventral mesencephalic cell line, RTC4, is protective in a rodent model of stroke

One therapeutic approach to stroke is the transplantation of cells capable of trophic support, reinnervation, and/or regeneration. Previously, we have described the use of novel truncated isoforms of SV40 large T antigen to generate unique cell lines from several primary rodent tissue types. Here we describe the generation of two cell lines, RTC3 and RTC4, derived from primary mesencephalic tissue using a fragment of mutant T antigen, T155c (cDNA) expressed from the RSV promoter. Both lines expressed the glial markers vimentin and S100beta, but not the neuronal markers NeuN, MAP2, or beta-III-tubulin. A screen for secreted trophic factors revealed substantially elevated levels of platelet-derived growth factor (PDGF) in RTC4, but not RTC3 cells. When transplanted into rat cortex, RTC4 cells survived for at least 22 days and expressed PDGF. Because PDGF has been reported to reduce ischemic injury, we examined the protective functions of RTC4 cells in an animal model of stroke. RTC4 or RTC3 cells, or vehicle, were injected into rat cortex 15-20 min prior to a 60-min middle cerebral artery ligation. Forty-eight hours later, animals were sacrificed and the stroke volume was assessed by triphenyl-tetrazolium chloride (TTC) staining. Compared to vehicle or RTC3 cells, transplanted RTC4 cells significantly reduced stroke volume. Overall, we generated a cell line with glial properties that produces PDGF and reduces ischemic injury in a rat model of stroke.

Transplantation of post-mitotic human neuroteratocarcinoma-overexpressing Nurr1 cells provides therapeutic benefits in experimental stroke: in vitro evidence of expedited neuronal differentiation and GDNF secretion

Nurr1 has been implicated as a transcription factor mediating the endogenous neuroprotective mechanism against stroke. We examined the in vivo and in vitro properties of a new human embryonic carcinoma Ntera-2 cell line carrying the human Nurr1 gene (NT2N.Nurr1). Adult Sprague-Dawley rats underwent experimental stroke initially and 14 days later were assigned randomly to receive stereotaxic transplantation of NT2N.Nurr1 cells or infusion of vehicle into their ischemic striatum. Transplantation of NT2N.Nurr1 cells promoted significant attenuation of behavioral impairments over a 56-day period after stroke, characterized by decreased hyperactivity, biased swing activity, and neurologic deficits, as well as significant reduction in ischemic striatal cell loss compared to vehicle-infused stroke animals. Transplanted NT2N.Nurr1 cells survived and expressed neuronal phenotypic markers in the ischemic striatum. In vitro results showed that cultured NT2.Nurr1 cells were already negative for nestin even before retinoic acid treatment, despite strong nestin immunoreactivity in NT2 cells. This indicates Nurr1 triggered a rapid commitment of NT2 cells into a neuronal lineage. Indeed, NT2.Nurr1 cells, at 4 weeks into RA treatment, displayed more abundant tyrosine hydroxylase positive cells than NT2 cells. Parallel ELISA studies showed further that cultured NT2N.Nurr1, but not NT2N cells, secreted glial cell derived neurotrophic factor. The present study shows efficacy of NT2N.Nurr1 cell grafts in ischemic stroke, with in vitro evidence suggesting the cells' excellent neuronal differentiation capability and ability to secrete GDNF as likely mechanisms mediating the observed therapeutic benefits.

Cell transplantation therapy for stroke

No treatment currently exists to restore lost neurological function after stroke. A growing number of studies highlight the potential of stem cell transplantation as a novel therapeutic approach for stroke. In this review we summarize these studies, discuss potential mechanisms of action of the transplanted cells, and emphasize the need to determine parameters that are critical for transplantation success.

Inflammation in stroke and focal cerebral ischemia

BACKGROUND

A growing number of recent investigations have established a critical role for leukocytes in propagating tissue damage after ischemia and reperfusion in stroke. Experimental data obtained from animal models of middle cerebral artery occlusion implicate inflammatory cell adhesion molecules, chemokines, and cytokines in the pathogenesis of this ischemic damage.

METHODS

Data from recent animal and human studies were reviewed to demonstrate that inflammatory events occurring at the blood-endothelium interface of the cerebral capillaries underlie the resultant ischemic tissue damage.

RESULTS

After arterial occlusion, the up-regulated expression of cytokines including IL-1, and IL-6 act upon the vascular endothelium to increase the expression of intercellular adhesion molecule-1, P-selectin, and E-selectin, which promote leukocyte adherence and accumulation. Integrins then serve to structurally modify the basal lamina and extracellular matrix. These inflammatory signals then promote leukocyte transmigration across the endothelium and mediate inflammatory cascades leading to further cerebral infarction.

CONCLUSIONS

Inflammatory interactions that occur at the blood-endothelium interface, involving cytokines, adhesion molecules, chemokines and leukocytes, are critical to the pathogenesis of tissue damage in cerebral infarction. Exploring these pathophysiological mechanisms underlying ischemic tissue damage may direct rational drug design in the therapeutic treatment of stroke.

The choroid plexus: function, pathology and therapeutic potential of its transplantation

The choroid plexus (CP) produces cerebrospinal fluid (CSF) and forms the blood-CSF barrier. However, the CP may have additional functions in the CNS beyond these traditional roles. Preclinical and clinical studies in ageing and neurodegeneration demonstrate anatomical and physiological changes in CP, suggesting roles in normal and pathological conditions and potentially endogenous repair processes following trauma. One of the broadest functions of the CP is establishing and maintaining the extracellular milieu throughout the brain and spinal cord, in part by secreting numerous growth factors into the CSF. The endogenous secretion of growth factors raises the possibility that transplantable CP might enable delivery of these molecules to the brain, while avoiding the conventional molecular and genetic alterations associated with modifying cells to secrete selected products. This review describes some of the anatomical and functional changes of CP in ageing and neurodegeneration, and recent demonstrations of the therapeutic potential of transplanted CP for neural trauma.

Stroke and TGF-beta proteins: glial cell line-derived neurotrophic factor and bone morphogenetic protein

Recent studies have indicated that proteins in the transforming growth factor-beta superfamily alter damage induced by various neuronal injuries. Of these proteins, glial cell line-derived neurotrophic factor (GDNF) and bone morphogenetic protein-7 (BMP-7) have unique protective and regenerative effects in stroke animals. Delivery of GDNF or BMP-7 to brain tissue reduced cerebral infarction and improved motor functions in stroke animals. Pretreatment with these factors reduced caspase-3 activity and DNA fragmentation in the ischemic brain region, suggesting that antiapoptotic effects are involved. Beside the protective effects, BMP-7 given after stroke improves locomotor function. These regenerative effects of BMP-7 may involve the enhancement of dendritic growth and remodeling. In this review, we illustrate the neuroprotective and neuroregenerative properties of GDNF and BMP-7 and emphasize their therapeutic potential for stroke.

Bone marrow grafts restore cerebral blood flow and blood brain barrier in stroke rats

We monitored alterations in cerebral blood flow (CBF) and blood-brain barrier (BBB) permeability following middle cerebral artery occlusion (MCAo) and intrastriatal transplantation of mouse bone marrow stromal cells (BMSCs) or saline infusion in adult Sprague-Dawley rats. Laser Doppler and Evans Blue assay revealed that BMSC grafts dose-dependently restored CBF and BBB to near normal levels at a much earlier period (Days 4-5 post-MCAo) in transplanted stroke animals compared to stroke animals that received saline infusion (Days 11-14 post-MCAo). Xenografted BMSCs survived in the absence of immunosuppression, and elevated levels of transforming growth factor-beta superfamily of neurotrophic factors were detected in transplanted stroke animals. These data suggest that early restoration of CBF and BBB following transplantation of BMSCs could mediate the reported functional outcomes in stroke animals.

Intracerebral Transplantation of Porcine Choroid Plexus Provides Structural and Functional Neuroprotection in a Rodent Model of Stroke

BACKGROUND AND PURPOSE

Choroid plexus (CP) secretes a cocktail of neurotrophic factors. In the present study, CP from neonatal pigs was encapsulated within alginate microcapsules for in vitro and in vivo neuroprotective studies.

METHODS

In vitro studies involved serum deprivation of rat embryonic cortical neurons and treatment with a range of concentrations of conditioned media from CP. For in vivo studies, rats received a 1-hour middle cerebral artery occlusion followed by intracranial transplantation of encapsulated or unencapsulated CP, empty capsules, or no transplant. Behavioral testing was conducted on days 1 to 3 after transplantation. Cerebral infarction was analyzed using 2,3,5-triphenyl-tetrazolium chloride staining at 3 days after transplantation.

RESULTS

Conditioned media from CP produced a significant dose-dependent protection of serum-deprived cortical neurons. Enzyme-linked immunosorbent assay confirmed secretion of GDNF, BDNF, and NGF from CP. Parallel in vivo studies showed that CP transplants improved behavioral performance and decreased the volume of infarction. Both encapsulated and unencapsulated CP transplants were effective; however, more robust benefits accompanied encapsulated transplants.

CONCLUSIONS

These data are the first to demonstrate the neuroprotective potential of transplanted CP and raise the intriguing possibility of using these cells as part of the treatment regimen for stroke and other neurological disorders.

Genetic and Cellular Therapies for Cerebral Infarction

Neurosurgeons, working as surgical scientists, can have a prominent role in developing and implementing genetic and cellular therapies for cerebral ischemia. The rapid emergence of both genetic and cellular therapies for neural regeneration warrants a careful analysis before implementation of human studies to understand the pitfalls and promises of this strategy. In this article, we review the topic of genetic and cellular therapy for stroke to provide a foundation for practicing neurosurgeons and clinical scientists who may become involved in this type of work. In Part 1, we review preclinical approaches with gene transfer, such as 1) improved energy delivery, 2) reduction of intracellular calcium availability, 3) abrogation of effects of reactive oxygen species, 4) reduction of proinflammatory cytokine signaling, 5) inhibition of apoptosis mediators, and 6) restorative gene therapy, that are paving the way to develop new strategies to treat cerebral infarction. In Part 2, we discuss the results of studies that address the possibility of using cellular therapies for stroke in animal models and in human trials by reviewing 1) the basics of stem cell biology, 2) exogenous and 3) and endogenous cell sources for therapy, and 4) clinical considerations in cell therapy applications. These emerging technologies based on the advancements made in recent years in the fields of genetics, therapeutic cloning, neuroscience, stem cell biology, and gene therapy provide significant potential for new therapies for stroke.

Intracerebral transplantation of carotid body in rats with transient middle cerebral artery occlusion

Recent laboratory and clinical studies demonstrate therapeutic efficacy of intracerebral transplantation of carotid body (CB) in Parkinson's disease, possibly through secretion of neurotrophic factors. Here, we examined the role of CB in experimental stroke. In the first experiment, we hypothesized that removal of CB would exacerbate cerebral infarction and stroke-related behavioral deficits. Eight-week-old, male Sprague-Dawley rats were randomly divided into two groups: stroke with intact CB and stroke with surgically removed CB. We used the stroke model of temporary middle cerebral artery occlusion. The ipsilateral CB was removed in animals assigned to treatment group exposed to stroke with surgically removed CB. Behavioral tests, using the elevated body swing test, were conducted at days 1-3 after surgery. Cerebral infarction was visualized by TTC staining on day 3 post-surgery. The data revealed no significant differences in behavioral deficits and infarct volumes between the two groups. In the second experiment, CB cell suspension grafts or control adult tissue grafts were intracerebally transplanted into the ischemic penumbra immediately (within 1 h) after stroke surgery. The results revealed significant reduction of behavioral deficits and infarct volumes, accompanied by increased levels of neurotrophic factors, as detected by ELISA, in transplanted ischemic striatum collected from CB-grafted stroke animals. These observations suggest that surgical resection of CB in the periphery did not alter stroke pathology; however, CB when made available in the CNS, via intracerebral transplantation, could protect against stroke possibly through the synergistic release of neurotrophic factors. The present study extends the use of CB as efficacious graft source for transplantation.

Intracerebral xenografts of mouse bone marrow cells in adult rats facilitate restoration of cerebral blood flow and blood–brain barrier

We examined in the present study alterations in cerebral blood flow (CBF) and blood-brain barrier (BBB) permeability following intrastriatal transplantation of mouse bone marrow stromal cells (BMSCs) or saline infusion in adult Sprague-Dawley rats. Laser Doppler revealed that transplanted animals exhibited near normal cerebral blood flow (CBF, 150 perfusion units) at a much earlier period post-transplantation (day 4) compared to animals that received saline infusion (day 12) (p's<0.05). Similarly, Evans Blue assay demonstrated that transplanted animals exhibited near complete BBB reconstitution at day 5 post-transplantation, whereas animals that received saline infusion continued to display a compromised BBB up to 11 days post-transplantation. Transplanted animals displayed a cell dose-dependent CBF and BBB restoration. Enzyme-linked immunosorbent assay (ELISA) of transplanted BMSCs revealed elevated levels of transforming growth factor-beta superfamily of neurotrophic factors. Moreover, despite the absence of immunosuppression in this cross-species transplantation, at least in the acute phase (12 days post-transplantation), surviving xenografts were detected during periods of restored CBF and BBB permeability. These observations suggest that restoration of CBF and BBB permeability accompanies the reported functional outcomes associated with intracerebral transplantation of BMSCs.

Melatonin-secreting pineal gland: a novel tissue source for neural transplantation therapy in stroke

Chronic systemic melatonin treatment attenuates abnormalities produced by occlusion of middle cerebral artery (MCA) in adult rats. Because the pineal gland secretes high levels of melatonin, we examined in the present study whether transplantation of pineal gland exerted similar protective effects in MCA-occluded adult rats. Animals underwent same-day MCA occlusion and either intrastriatal transplantation of pineal gland (harvested from 2-month-old rats) or vehicle infusion. Behavioral tests (from day of surgery to 3 days posttransplantation) revealed that transplanted stroke rats displayed significantly less motor asymmetrical behaviors than vehicle-infused stroke rats. Histological analysis at 3 days posttransplantation revealed that transplanted stroke rats had significantly smaller cerebral infarction than vehicle-infused rats. Additional experiments showed that pinealectomy affected transplantation outcome, in that transplantation of pineal gland only protected against stroke-induced deficits in stroke animals with intact pineal gland, but not in pinealectomized stroke rats. Interestingly, nonpinealectomized vehicle-infused stroke rats, as well as pinealectomized transplanted stroke rats, had significantly lower melatonin levels in the cerebrospinal fluid than nonpinealectomized transplanted stroke rats. We conclude that intracerebral transplantation of pineal gland, in the presence of host intact pineal gland, protected against stroke, possibly through secretion of melatonin.

AF5, a CNS cell line immortalized with an N-terminal fragment of SV40 large T: growth, differentiation, genetic stability, and gene expression

Central nervous system progenitor cells that are self-renewing in culture and also differentiate under controlled conditions are potentially useful for developmental studies and for cell-based therapies. We characterized growth and plasticity properties and gene expression in a rat mesencephalic cell line, AF5, that was immortalized with an N-terminal fragment of SV40 large T (T155g). For over 150 population doublings in culture, the growth rate of AF5 cells remained steady, the cells remained responsive to bFGF, and telomerase activity and telomere lengths were unchanged. While karyotype analyses revealed some chromosomal abnormalities, these were also unchanged over time; additionally, no mutations in p53 gene sequences were found, and wild-type p53 activation was normal. AF5 cells produced PDGF, TGFbeta1, TGFbeta2, and bFGF. Similar to primary progenitor cells, AF5 cells retained their plasticity in culture; they could be propagated in an undifferentiated state as "neurospheres" in serum-free media or as adherent cultures in serum-containing media, and they differentiated when allowed to become confluent. Adherent subconfluent actively growing cultures expressed a marker for immature neurons, nestin, while few cells expressed the mature neuronal cell marker betaIII-tubulin. Confluent cultures ceased growing, developed differentiated morphologies, contained few or no nestin-expressing cells, and acquired betaIII-tubulin expression. Global gene expression was examined using a 15,000 gene microarray, comparing exponential growth with and without bFGF stimulation, and the differentiated state. The AF5 cell line exhibited stable genetic and growth properties over extended periods of time, while retaining the ability to differentiate in vitro. These data suggest that the AF5 cell line may be useful as an in vitro model system for studies of neural differentiation.

Protective effects of glial cell line-derived neurotrophic factor in ischemic brain injury

Glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-beta (TGF-beta) superfamily, has been shown to have trophic activity on dopaminergic neurons. Recent studies indicate that GDNF can protect the cerebral hemispheres from damage induced by middle cerebral arterial ligation. We found that such neuroprotective effects are mediated through specific GDNF receptor alpha-1 (GFRalpha1). Animals with a deficiency in GFRalpha-1 have less GDNF-induced neuroprotection. Ischemia also enhances nitric oxide synthase (NOS) activity, which can be attenuated by GDNF. These.data suggest that GDNF can protect against ischemic injury through a GFRalpha-1/NOS mechanism. We also found that the receptor for GDNF, GFRalpha1, and its signaling moiety c-Ret were upregulated, starting immediately after ischemia. This upregulation suggests that activation of an endogenous neuroprotective mechanism occurs so that responsiveness of GDNF can be enhanced at very early stages during ischemia.