Intravenous administration of human umbilical cord blood cells in a mouse model of amyotrophic lateral sclerosis: distribution, migration, and differentiation

Umbilical cord blood transfusions for prevention of progressive brain injury and induction of neural recovery: an immunological perspective

One of the most promising treatments for neurodegenerative diseases appears to be human umbilical cord blood cell transplantation. A variety of studies demonstrate some benefit of this method of treatment in a number of different animal models and case studies. However, before the methodologies and results of these animal studies and case studies can be translated into successful widespread treatments, aspects relating to the immunological properties of the transplanted cells must be considered. In this perspective, we discuss the benefit of the cellular immaturity of these cells with respect to the immune response, and compare cord blood transplantation to blood transfusions, as well as discussing what future studies should entail.

Grafted neural stem cells increase the life span and protect motoneurons in pmn mice

In this study, we have grafted neural stem cells (NSCs) into the lumbar spinal cord of a mouse mutant that has a specific loss of motoneurons (progressive motor neuronopathy/pmn). A small number of grafted cells ( approximately 3000) increased the life span of the mice by 56%. The improved survival was accompanied by a rescue of host motoneurons, a stabilization in the weight and an increase in the size of the muscle fibers. The grafted NSCs were small and round and exhibited no neural markers, suggesting that they remained in an undifferentiated state. Thus grafting of NSCs in a mouse model with motoneuron degeneration exerts a neuroprotective effect.

Proliferation, differentiation, and cytokine secretion of human umbilical cord blood-derived mononuclear cells in vitro

OBJECTIVE

Human umbilical cord blood (hUCB)-derived mononuclear cells were previously shown to exert therapeutic effects in a number of animal models of nervous system impairment. However, the mechanisms underlying the structural and functional improvements are still unclear. As cell replacement seems to be a rare or absent event in vivo, we suggest secondary mechanisms, by which the therapeutic effect of transplanted mononuclear cells might be mediated. We investigated the potential of hUCB-derived mononuclear cells in vitro to proliferate, differentiate, and to secrete factors possibly beneficial for the host brain tissue in vivo.

METHODS

Using a succession of distinct culture media, mononuclear cells were stimulated by growth factor combinations, e.g., epidermal growth factor (EGF)/fibroblast growth factor-2 (FGF-2) or nerve growth factor (NGF)/retinoic acid (RA). Expression of hematological and neural marker proteins was investigated by immunoblotting, immunocytochemistry, and fluorescence-activated cell analysis. Secretion of proteins was assayed using a human cytokine antibody array, and quantified via enzyme-linked immunosorbent assay.

RESULTS

Mononuclear cells were shown to undergo proliferation in the presence of EGF/FGF-2. When cells were cultured in NGF/RA-containing medium, neuronal and glial marker proteins were expressed, indicating differentiation. In the presence of either growth factor combination, cells in vitro secrete interleukins, growth factors, and chemotactic proteins.

CONCLUSION

Although capable of incipient differentiation, cytokine secretion of hUCB-derived mononuclear cells envisages the potential of an indirect effect in vivo. Most factors detected in conditioned medium are renowned for their anti-inflammatory, neuroprotective, angiogenic, or chemotactic actions, thus, providing the means for a therapeutic outcome mediated by secondary effects.

Experimental concepts for toxicity prevention and tissue restoration after central nervous system irradiation

Several experimental strategies of radiation-induced central nervous system toxicity prevention have recently resulted in encouraging data. The present review summarizes the background for this research and the treatment results. It extends to the perspectives of tissue regeneration strategies, based for example on stem and progenitor cells. Preliminary data suggest a scenario with individually tailored strategies where patients with certain types of comorbidity, resulting in impaired regeneration reserve capacity, might be considered for toxicity prevention, while others might be "salvaged" by delayed interventions that circumvent the problem of normal tissue specificity. Given the complexity of radiation-induced changes, single target interventions might not suffice. Future interventions might vary with patient age, elapsed time from radiotherapy and toxicity type. Potential components include several drugs that interact with neurodegeneration, cell transplantation (into the CNS itself, the blood stream, or both) and creation of reparative signals and a permissive microenvironment, e.g., for cell homing. Without manipulation of the stem cell niche either by cell transfection or addition of appropriate chemokines and growth factors and by providing normal perfusion of the affected region, durable success of such cell-based approaches is hard to imagine.

Intrathecal application of neuroectodermally converted stem cells into a mouse model of ALS: limited intraparenchymal migration and survival narrows therapeutic effects

Stem and progenitor cells provide a promising therapeutic strategy for amyotrophic lateral sclerosis (ALS). To comparatively evaluate the therapeutic potentials of human bone marrow-derived mesodermal stromal cells (hMSCs) and umbilical cord blood cells (hUBCs) in ALS, we transplanted hMSCs and hUBCs and their neuroectodermal derivatives (hMSC-NSCs and hUBC-NSCs) into the ALS mouse model over-expressing the G93A mutant of the human SOD1 gene. We used a standardized protocol similar to clinical studies by performing a power calculation to estimate sample size prior to transplantation, matching the treatment groups for gender and hSOD-G93A gene content, and applying a novel method for directly injecting 100,000 cells into the CSF (the cisterna magna). Ten days after transplantation we found many cells within the subarachnoidal space ranging from frontal basal cisterns back to the cisterna magna, but only a few cells around the spinal cord. hMSCs and hMSC-NSCs were also located within the Purkinje cell layer. Intrathecal cell application did not affect survival times of mice compared to controls. Consistently, time of disease onset and first pareses, death weight, and motor neuron count in lumbar spinal cord did not vary between treatment groups. Interestingly, transplantation of hMSCs led to an increase of pre-symptomatic motor performance compared to controls in female animals. The negative outcome of the present study is most likely due to insufficient cell numbers within the affected brain regions (mainly the spinal cord). Further experiments defining the optimal cell dose, time point and route of application and particularly strategies to improve the homing of transplanted cells towards the CNS region of interest are warranted to define the therapeutic potential of mesodermal stem cells for the treatment of ALS.

Amyotrophic lateral sclerosis – The tools of the trait

The aim of this review is to analyze how our knowledge on the etiology, pathology, and treatment of amyotrophic lateral sclerosis (ALS) has profited from the application of biotechnology tools for the identification of disease markers, the development of animal disease models, and the design of innovative therapeutics. In humans, ALS-specific clinical, genetic or protein biomarkers, or panels of biomarkers stemming from genomics and proteomics analyses can be critical for early diagnosis, monitoring of disease progression, drug validation in clinical trials, and identification of therapeutic targets for subsequent drug development. At the same time, animal models representing a number of human superoxide dismutase 1 mutations, intermediate-filament disorganization or axonal-transport defects have been invaluable in unraveling aspects of the pathophysiology of the disease; in each case, these only represent a small proportion of all ALS patients. Preclinical and clinical trials, although at present heavily concentrating on pharmacological approaches, are embracing the emerging alternative strategies of stem-cell and gene therapy. In combination with a further subcategorization of patients and the development of corresponding model systems for functional analyses, they will significantly influence the already changing face of ALS therapy.

Neuroprotective effect of adult hematopoietic stem cells in a mouse model of motoneuron degeneration

Degenerative spinal motor diseases, like amyotrophic lateral sclerosis, are produced by progressive degeneration of motoneurons. Their clinical manifestations include a progressive muscular weakness and atrophy, which lead to paralysis and premature death. Current pharmacological therapies fail to stop the progression of motor deficits or to restore motor function. The purpose of our study was to explore the possible beneficial effect of mouse adult hematopoietic stem cells (hSCs) transplanted into the spinal cord of a mouse model of motoneuron degeneration. Our results show that grafted hSCs survive in the spinal cord. In addition, the number of motoneurons in the transplanted spinal cord is larger than in non-transplanted mdf mice at the same spinal cord segments and importantly, motor function significantly improves. These effects can be explained by the increased levels of glial cell line derived neurotrophic factor (GDNF) around host motoneurons produced by the grafted cells. Thus, these experiments demonstrate the neuroprotective effect of adult hSCs in the model employed and indicate that this cell type may contribute to ameliorating motor function in degenerative spinal motor diseases.

Ultrastructure of blood-brain barrier and blood-spinal cord barrier in SOD1 mice modeling ALS

The purpose of this study was to determine the ultrastructure of the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) in G93A SOD1 mice modeling ALS at different stages of disease. Electron microscope examination of brainstem, cervical and lumbar spinal cords was performed in ALS mice at early and late stages of disease. Our results show disorganized mitochondrial cristae and degenerating mitochondria in endothelial cells and neuropil, swollen astrocyte foot processes, swollen and degenerating capillary endothelial cells, astrocytes and motor neurons and extensive extracellular edema. In spite of progressive extracellular edema in neural tissue, capillary endothelial cell tight junctions appeared to remain intact in early and late symptomatic animals. Results show that disruption of BBB and BSCB was evident in areas of motor neuron degeneration in G93A mice at both early and late stages of disease. Capillary rupture was observed in brainstem in early symptomatic G93A mice. Capillary ultrastructure revealed that endothelial cell membrane and/or basement membrane damage occurred, followed by vascular leakage.

Neural stem cells LewisX+ CXCR4+ modify disease progression in an amyotrophic lateral sclerosis model

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease characterized by the degeneration of the motor neurons. We tested whether treatment of superoxide dismutase (SOD1)-G93A transgenic mouse, a model of ALS, with a neural stem cell subpopulation double positive for Lewis X and the chemokine receptor CXCR4 (LeX+CXCR4+) can modify the disease's progression. In vitro, after exposure to morphogenetic stimuli, LeX+CXCR4+ cells generate cholinergic motor neuron-like cells upon differentiation. LeX+CXCR4+ cells deriving from mice expressing Green Fluorescent Protein in all tissues or only in motor neurons, after a period of priming in vitro, were grafted into spinal cord of SOD1-G93A mice. Transplanted transgenic mice exhibited a delayed disease onset and progression, and survived significantly longer than non-treated animals by 23 days. Examination of the spinal cord revealed integration of donor-derived cells that differentiated mostly in neurons and in a lower proportion in motor neuron-like cells. Quantification of motor neurons of the spinal cord suggests a significant neuroprotection by LeX+CXCR4+ cells. Both VEGF- and IGF1-dependent pathways were significantly modulated in transplanted animals compared to controls, suggesting a role of these neurotrophins in MN protection. Our results support the therapeutic potential of neural stem cell fractions through both neurogenesis and growth factors release in motor neuron disorders.

Trophic factor induction of human umbilical cord blood cells in vitro and in vivo

The mononuclear fraction of human umbilical cord blood (HUCBmnf) is a mixed cell population that multiple research groups have shown contains cells that can express neural proteins. In these studies, we have examined the ability of the HUCBmnf to express neural antigens after in vitro exposure to defined media supplemented with a cocktail of growth and neurotrophic factors. It is our hypothesis that by treating the HUCBmnf with these developmentally-relevant factors, we can expand the population, enhance the expression of neural antigens and increase cell survival upon transplantation. Prior to growth factor treatment in culture, expression of stem cell antigens is greater in the non-adherent HUCBmnf cells compared to the adherent cells (p < 0.05). Furthermore, treatment of the non-adherent cells with growth factors, increases BrdU incorporation, especially after 14 days in vitro (DIV). In HUCBmnf-embryonic mouse striata co-culture, a small number of growth factor treated HUCBmnf cells were able to integrate into the growing neural network and express immature (nestin and TuJ1) and mature (GFAP and MAP2) neural markers. Treated HUCBmnf cells implanted in the subventricular zone predominantly expressed GFAP although some grafted HUCBmnf cells were MAP2 positive. While short-term treatment of HUCBmnf cells with growth and neurotrophic factors enhanced proliferative capacity in vitro and survival of the cells in vivo, the treatment regimen employed was not enough to ensure long-term survival of HUCBmnf-derived neurons necessary for cell replacement therapies for neurodegenerative diseases.

Stem Cell Therapy—Present Status

Stem cell research is a new field that is advancing at an incredible pace with new discoveries being reported from all over the world. Scientists have for years looked for ways to use stem cells to replace cells and tissues that are damaged or diseased. Stem cells are the foundation cells for every organ, tissue, and cell in the body. Stem cells are undifferentiated, "blank" cells that do not yet have a specific function. Under proper conditions, stem cells begin to develop into specialized tissues and organs. They are self-sustaining and can replicate themselves for long periods of time. Embryonic stem cells are pluripotent cells, isolated from the inner cell mass of the blastocyst-stage mammalian embryo. They have the ability to differentiate into several somatic or somatic-like functional cells such as neurons, hepatocytes, cardiomyocytes, and others. Adult stem cells are specialized cells found within many tissues of the body where they function in tissue homeostasis and repair. They are precursor cells capable of differentiation into several different cells. The knowledge of stem cells from various sources offered a new hope for the treatment of various diseases.

Autotransplantation of bone marrow-derived stem cells as a therapy for neurodegenerative diseases

Neurodegenerative diseases are characterized by a progressive degeneration of selective neural populations. This selective hallmark pathology and the lack of effective treatment modalities make these diseases appropriate candidates for cell therapy. Bone marrow-derived mesenchymal stem cells (MSCs) are self-renewing precursors that reside in the bone marrow and may further be exploited for autologous transplantation. Autologous transplantation of MSCs entirely circumvents the problem of immune rejection, does not cause the formation of teratomas, and raises very few ethical or political concerns. More than a few studies showed that transplantation of MSCs resulted in clinical improvement. However, the exact mechanisms responsible for the beneficial outcome have yet to be defined. Possible rationalizations include cell replacement, trophic factors delivery, and immunomodulation. Cell replacement theory is based on the idea that replacement of degenerated neural cells with alternative functioning cells induces long-lasting clinical improvement. It is reasoned that the transplanted cells survive, integrate into the endogenous neural network, and lead to functional improvement. Trophic factor delivery presents a more practical short-term approach. According to this approach, MSC effectiveness may be credited to the production of neurotrophic factors that support neuronal cell survival, induce endogenous cell proliferation, and promote nerve fiber regeneration at sites of injury. The third potential mechanism of action is supported by the recent reports claiming that neuroinflammatory mechanisms play an important role in the pathogenesis of neurodegenerative disorders. Thus, inhibiting chronic inflammatory stress might explain the beneficial effects induced by MSC transplantation. Here, we assemble evidence that supports each theory and review the latest studies that have placed MSC transplantation into the spotlight of biomedical research.

Adult stem cell therapy: Dream or reality?

Adult stem cells may be an invaluable source of plastic cells for tissue regeneration. The bone marrow contains different subpopulations of adult stem cells easily accessible for transplantation. However the therapeutic value of adult stem cell is a question of debate in the scientific community. We have investigated the potential benefits of adult hematopoietic stem cell transplantation in animal models of demyelinating and motor neuron diseases. Our results suggest that transplantation of HSC have direct and indirect neuroregenerative and neuroprotective effects.

ALS: a disease of motor neurons and their nonneuronal neighbors

Amyotrophic lateral sclerosis is a late-onset progressive neurodegenerative disease affecting motor neurons. The etiology of most ALS cases remains unknown, but 2% of instances are due to mutations in Cu/Zn superoxide dismutase (SOD1). Since sporadic and familial ALS affects the same neurons with similar pathology, it is hoped that therapies effective in mutant SOD1 models will translate to sporadic ALS. Mutant SOD1 induces non-cell-autonomous motor neuron killing by an unknown gain of toxicity. Selective vulnerability of motor neurons likely arises from a combination of several mechanisms, including protein misfolding, mitochondrial dysfunction, oxidative damage, defective axonal transport, excitotoxicity, insufficient growth factor signaling, and inflammation. Damage within motor neurons is enhanced by damage incurred by nonneuronal neighboring cells, via an inflammatory response that accelerates disease progression. These findings validate therapeutic approaches aimed at nonneuronal cells.

Complexity of astrocyte-motor neuron interactions in amyotrophic lateral sclerosis

Neurons and surrounding glial cells compose a highly specialized functional unit. In amyotrophic lateral sclerosis (ALS) astrocytes interact with motor neurons in a complex manner to modulate neuronal survival. Experiments using chimeric mice expressing ALS-linked mutations to Cu,Zn superoxide dismutase (SOD-1) suggest a critical modulation exerted by neighboring non-neuronal cell types on disease phenotype. When perturbed by primary neuronal damage, e.g. expression of SOD-1 mutations, neurons can signal astrocytes to proliferate and become reactive. Fibroblast growth factor-1 (FGF-1) can be released by motor neurons in response to damage to induce astrocyte activation by signaling through the receptor FGFR1. FGF-1 stimulates nerve growth factor (NGF) expression and secretion, as well as activity of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor. Nrf2 leads to the expression of antioxidant and cytoprotective enzymes such as heme oxygenase-1 and a group of enzymes involved in glutathione metabolism that prevent motor neuron degeneration. However, prolonged stimulation with FGF-1 or SOD-mediated oxidative stress in astrocytes may disrupt the normal neuron-glia interactions and lead to progressive neuronal degeneration. The re-expression of p75 neurotrophin receptor and neuronal NOS in motor neurons in parallel with increased NGF secretion by reactive astrocytes may be a mechanism to eliminate critically damaged neurons. Consequently, astrocyte activation in ALS may have a complex pathogenic role.

Transplantation of a novel cell line population of umbilical cord blood stem cells ameliorates neurological deficits associated with ischemic brain injury

Umbilical cord blood (UCB) is a rich source of hematopoetic stem cells (HSCs). We have isolated a novel cell line population of stem cells from human UCB that exhibit properties of self-renewal, but do not have cell-surface markers that are typically found on HSCs. Analysis of transcripts revealed that these cells express transcription factors Oct-4, Rex-1, and Sox-2 that are typically expressed by stem cells. We refer to these novel cells as nonhematopoietic umbilical cord blood stem cells (nh-UCBSCs). Previous studies have shown that the intravenous infusion of UCBCs can ameliorate neurological deficits arising from ischemic brain injury. The identity of the cells that mediate this restorative effect, however, has yet to be determined. We postulate that nh-UCBSCs may be a source of the UCB cells that can mediate these effects. To test this hypothesis, we intravenously injected one million human nh-UCBSCs into rats 48 h after transient unilateral middle cerebral artery occlusion. Animals in other experimental groups received either saline injections or injections of RN33b neural stem cells. Animals were tested for neurological function before the infusion of nh-UCBSCs and at various time periods afterwards using a battery of behavioral tests. In limb placement tests, animals treated with nh-UCBSCs exhibited mean scores that were significantly better than animals treated with RN33b neural stem cells or saline. Similarly, in stepping tests, nh-UCBSC-treated animals again exhibited significantly better performance than the other experimental groups of animals. Analysis of infarct volume revealed that ischemic animals treated with nh-UCBSCs exhibited a 50% reduction in lesion volume in comparison to saline-treated controls. Histological analysis of brain tissue further revealed the presence of cells that stained for human nuclei. Some human nuclei-positive cells were also co-labeled for NeuN, indicating that the transplanted cells expressed markers of a neuronal phenotype. Cells expressing the human nuclei marker within the brain, however, were rather scant, suggesting that the restorative effects of nh-UCBSCs may be mediated by mechanisms other than cell replacement. To test this hypothesis, nh-UCBSCs were directly transplanted into the brain parenchyma after ischemic brain injury. Sprouting of nerve fibers from the nondamaged hemisphere into the ischemically damaged side of the brain was assessed by anterograde tracing using biotinylated dextran amine (BDA). Animals with nh-UCBSC transplants exhibited significantly greater densities of BDA-positive cells in the damaged side of the brain compared to animals with intraparenchymal saline injections. These results suggest that restorative effects observed with nh-UCBSC treatment following ischemic brain injury may be mediated by trophic actions that result in the reorganization of host nerve fiber connections within the injured brain.

Targets in ALS: designing multidrug therapies

Amyotrophic lateral sclerosis (ALS) is an incurable disease that arises from the progressive loss of motoneurons. Even when caused by a single gene defect, as in the case of mutations in the enzyme Cu-Zn superoxide dismutase (SOD1), ALS is the result of a complex cascade that involves crosstalk among motoneurons, glia and muscles, and evolves through the action of converging toxic mechanisms. Transgenic rodents that express human mutant SOD1 and develop a progressive paralytic disease are widely used to screen potential therapeutics. Treatments that interfere with a specific event in the neurotoxic cascade have been reported to produce a modest increase in rodent lifespan. Multi-intervention approaches, including novel methods to intercept the damage and to deliver molecules to vulnerable cells, have recently been shown to be more effective. Thus, new avenues for promising therapeutic approaches can be derived from multidrug treatments and/or the delivery of growth factors by viral vectors, in combination with exercise and/or diet regimens.

Umbilical cord blood-derived stem cells and brain repair

Human umbilical cord blood (HUCB) is now considered a valuable source for stem cell-based therapies. HUCB cells are enriched for stem cells that have the potential to initiate and maintain tissue repair. This potential is especially attractive in neural diseases for which no current cure is available. Furthermore, HUCB cells are easily available and less immunogenic compared to other sources for stem cell therapy such as bone marrow. Accordingly, the number of cord blood transplants has doubled in the last year alone, especially in the pediatric population. The therapeutic potential of HUCB cells may be attributed to inherent ability of stem cell populations to replace damaged tissues. Alternatively, various cell types within the graft may promote neural repair by delivering neural protection and secretion of neurotrophic factors. In this review, we evaluate the preclinical studies in which HUCB was applied for treatment of neurodegenerative diseases and for traumatic and ischemic brain damage. We discuss how transplantation of HUCB cells affects these disorders and we present recent clinical studies with promising outcome.

Cord blood rescues stroke-induced changes in splenocyte phenotype and function

The neuroprotective mechanism of human umbilical cord blood cells (HUCBC) in the rat middle cerebral artery occlusion (MCAO) stroke model remains uncertain. Given the inflammatory sequelae that occur following stroke, we investigated whether HUCBC protection could be derived from the modulation of this immuno-inflammatory event, suggested by the attraction of the HUCBC to the spleen. We found that, following MCAO, rat spleen size was reduced concomitantly with their CD8+ T-cell counts. Interestingly, MCAO-induced spleen size reduction correlated with the extent of ischemic damage, however, HUCBC treatment rescued the spleen weight, splenic CD8+ T-cell counts, as well as the amount of brain injury. Additionally, splenocyte proliferation assays demonstrated that HUCBC treatment opposed MCAO-associated T-cell proliferation by increasing the production of IL-10 while decreasing IFN-gamma. Taken together, these results suggest a novel immunomodulatory mechanism by which HUCBC mediate protection in the rat MCAO model of stroke.

Cytokines produced by cultured human umbilical cord blood (HUCB) cells: Implications for brain repair

The potential therapeutic benefits from human umbilical cord blood (HUCB) cells for the treatment of injuries, diseases, and neurodegeneration are becoming increasingly recognized. The transplantation or infusion of cord blood cells in various animal models, such as ischemia/stroke, traumatic brain injury, myocardial infarction, Parkinson's disease, and amyotropic lateral sclerosis, has resulted in amelioration of behavioral deficits, and with some diseases, a prolonged lifespan decreased neuropathology. Previously, we reported the migration of HUCB cells to ischemic brain supernatant (tissue extracts) is time-dependent, and the expression of specific chemokines responds to this migration pattern. The mechanism(s) responsible for these effects are unknown. The expression of cytokines and chemokines produced by HUCB cells (under various culturing conditions) was investigated in this study. IL-8, MCP-1, and IL-1alpha were consistently expressed by the HUCB mononuclear cells regardless of the culture condition. These results provide insights to factors that may be partially responsible for the functional improvements seen in the animal models of injury investigating the therapeutic use of HUCB cells.

Neural stem cell systems: diversities and properties after transplantation in animal models of diseases

Currently available effective treatments of the diseased or damaged central nervous system (CNS) are restricted to a limited pharmacological relief of symptoms or those given to avoid further damage. Therefore the search is on for treatments that can restore function in the CNS. During recent years replacement of damaged neurons by cell transplantation is being enthusiastically explored as a potential treatment for many neurodegenerative diseases, stroke and traumatic brain injury. Several references in both scientific journals and popular newspapers concerning different types of cultured stem cells, potentially exploitable to treat pathological conditions of the brain, raise important questions pertinent to the fundamental and realistic differences between grafts of primary neural cells and the transplantation of in vitro expanded neural stem cells (NSCs). Our aim is to review the available information on the grafting of different NSC types into the adult rodent brain, focusing on critical aspects for the development of clinical therapies to replace damaged neurons.

Relevance of motoneuron specification and programmed cell death in embryos to therapy of ALS

The molecular cues that generate spinal motoneurons in early embryonic development are well defined. Motoneurons are generated in excess and consequently undergo a natural period of programmed cell death. Although it is not known exactly how motoneurons compete for survival in embryonic development, it is hypothesized that they rely on the ability to access limited amounts of trophic factors from peripheral tissues, a process that is tightly regulated by skeletal muscle activity. Attempts to elucidate the molecular mechanisms that underlie motoneuron generation and programmed cell death in embryos have led to various effective strategies for treating injury and disease in animal models. Such studies provide great hope for the amelioration of human amyotrophic lateral sclerosis (ALS), a devastating progressive motoneuron degenerative disease. Here we review the clinical relevance of studying motoneuron specification and death during embryonic development.

Development of a rat model of spinal cord injury and cellular transplantation

BACKGROUND AND PURPOSE

Intravenously or intraspinally delivered human umbilical cord blood (UCB) cells and mesenchymal stem cells have been previously shown to improve the functional recovery of spinal cord-injured rats. Obtaining an animal model in the laboratory setting is critical for the development of experimental therapies. We have established a rat model of spinal cord injury (SCI) with basic histological and functional evaluations, ready to use for cell transplantation experiments.

METHODS

In the first phase 10 Sprague-Dawley (SD) rats were used to standardize the laminectomy at D9-D10 without secondary lesions. In a second phase, 28 SD rats were laminectomized and injured at D9 by spinal cord compression for 3 to 5 seconds with an aneurysmal clip. Open-field behavior was assessed at days 2 and 7 postoperatively, and weekly until their sacrifice, using the Basso, Beattie, and Bresnahan locomotor rating scale. Two weeks postinjury, 14 immunosuppressed rats received a double intraspinal cell transplant of previously frozen UCB mononuclear cells (MNCs). Using a Hamilton syringe, 2.5 x 10(5) unlabelled MNCs in 10 microL medium were transplanted, rostrally and caudally to the lesion site. Rats were sacrificed at 4 weeks posttransplant by transcardial perfusion with 4% paraformaldehyde, and spinal cords were dissected and further fixated for histological analysis.

RESULTS

No wound infections were observed. Thirteen rats developed urinary tract infections and two animals showed autophagia grade 3. We observed a common spontaneous mobility improvement until a certain limit, depending on the degree of lesion and intrinsic characteristics of the animal.

CONCLUSIONS

An animal model of SCI has been established. Critical parameters in the survival and correct functional analysis are continuous animal care postinjury, urinary tract infections, autophagia, and weight loss. In addition, electrophysiological measures might be necessary to properly assess functional modifications.

Anti-inflammatory effects of human cord blood cells in a rat model of stroke

When human umbilical cord blood cells (HUCBCs) are administered intravenously after a middle cerebral artery occlusion, they reliably produce behavioral and anatomical recovery, and protect neural tissue from progressive change. However, our results indicate that the cells do not exert their effects by engraftment in the peri-infarct region, even though they migrate to the site of injury. The objective of the present study was to determine if the cells induce recovery by decreasing inflammation. We used a combination of in vivo and in vitro studies to show that HUCBCs decrease inflammation in the brain after stroke and thereby enhance neuroprotection. After stroke and transplantation, there was a decrease in CD45/CD11b- and CD45/B220-positive (+) cells. This decrease was accompanied by a decrease in mRNA and protein expression of pro-inflammatory cytokines and a decrease in nuclear factor kappaB (NF-kappaB) DNA binding activity in the brain of stroke animals treated with HUCBCs. In addition to modulating the inflammatory response, we demonstrate that the cord blood cells increase neuronal survival through non-immune mechanisms. Once thought of as "cell replacement therapy," we now propose that cord blood treatment in stroke reduces inflammation and provides neuroprotection. Both of these components are necessary for effective therapy.

Maternal transplantation of human umbilical cord blood cells provides prenatal therapy in Sanfilippo type B mouse model

Numerous data support passage of maternal cells into the fetus during pregnancy in both human and animal models. However, functional benefits of maternal microchimerism in utero are unknown. The current study attempted to take advantage of this route for prenatal delivery of alpha-N-acetylglucosaminidase (Naglu) enzyme into the enzyme-deficient mouse model of Sanfilippo syndrome type B (MPS III B). Enzymatically sufficient mononuclear cells from human umbilical cord blood (MNC hUCB) were intravenously administered into heterozygote females modeling MPS III B on the 5th day of pregnancy during blastocyst implantation. The major findings were 1) administered MNC hUCB cells transmigrated and diffused into the embryos (E12.5); 2) some transmigrated cells expressed CD34 and CD117 antigens; 3) transmigrated cells were found in both the maternal and embryonic parts of placentas; 4) transmigrated cells corrected Naglu enzyme activity in all embryos; 5) administered MNC hUCB cells were extensively distributed in the organs and the blood of heterozygote mothers at one week after transplantation. Results indicate that prenatal delivery of Naglu enzyme by MNC hUCB cell administration into mothers of enzyme-deficient embryos is possible and may present a significant opportunity for new biotechnologies to treat many inherited disorders.

Lumbar Puncture Delivery of Bone Marrow Stromal Cells in Spinal Cord Contusion: A Novel Method for Minimally Invasive Cell Transplantation

Cell transplantation as a treatment for spinal cord injury is a promising therapeutic strategy whose effective clinical application would be facilitated by non-invasive delivery protocols. Cells derived from the bone marrow are particularly attractive because they can be obtained easily, expanded to large numbers and potentially used for autologous as well as allogeneic transplantation. In this study we tested the feasibility of a novel minimally invasive method--lumbar puncture (LP)--for transplanting bone marrow stromal stem cells (MSC) into a clinically relevant spinal cord contusion model. We further sought to determine optimal protocols for performing such minimally invasive cell transplantation. Sprague-Dawley rats received a moderate contusion injury at the midthoracic level followed by LP transplantation of MSC derived from transgenic rats that express the human placental alkaline phosphatase (AP) reporter gene. The recipients were analyzed histologically to evaluate the extent of cell delivery and survival at the injury site. We found that MSC delivered by LP reached the contused spinal cord tissues and exerted a significant beneficial effect by reducing cyst and injury size. Transplantation within 14 days of injury provided significantly greater grafting efficiency than more delayed delivery, and increasing MSC dosage improved cell engraftment. The techniques described here can easily be translated to patients, thus accelerating clinical application of stem cell therapies.

Novel cell therapy approaches for brain repair

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

Origin and distribution of bone marrow-derived cells in the central nervous system in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is associated with increased numbers of microglia within the central nervous system (CNS). However, it is unknown whether the microgliosis results from proliferation of CNS resident microglia, or recruitment of bone marrow (BM)-derived microglial precursors. Here we assess the distribution and number of BM-derived cells in spinal cord using transplantation of green fluorescent protein (GFP)-labeled BM cells into myelo-ablated mice over-expressing human mutant superoxide dismutase 1 (mSOD), a murine model of ALS. Transplantation of GFP+ BM did not affect the rate of disease progression in mSOD mice. Mean numbers of microglia and GFP+ cells in spinal cords of control mice were not significantly different from those in asymptomatic mSOD mice and showed no change with animal age. The number of GFP+ cells and microglia (F4/80+ and CD11b+ cells) within the spinal cord of mSOD mice increased compared to age-matched controls at a time when mSOD mice exhibited disease symptoms, continuing up to disease end-stage. Although we observed an increase in the number of GFP+ cells in spinal cords of mSOD mice with disease symptoms, mean numbers of GFP+ F4/80+ cells comprised less than 20% of all F4/80+ cells and did not increase with disease progression. Furthermore, the relative rates of proliferation in CD45+GFP- and CD45+GFP+ cells were comparable. Thus, we demonstrate that the microgliosis present in spinal cord tissue of mSOD mice is primarily due to an expansion of resident microglia and not to the recruitment of microglial precursors from the circulation.

Administration of human umbilical cord blood to low birth weight infants may prevent the subsequent development of type 2 diabetes

Both epidemiological and experimental studies have shown that impaired growth in utero due to maternal malnutrition, resulting in low birth weight, is associated with a high incidence of glucose intolerance, insulin resistance, and type 2 diabetes in adult life. Maternal malnutrition is a worldwide problem and unavoidable; therefore, prevention of type 2 diabetes in low birth weight infants who reach adulthood is difficult to achieve. Administration of human umbilical cord blood (HUCB) mononuclear cells into type 1 and type 2 diabetic mice has been shown to improve both their blood glucose levels and survival. It has also been shown that the progenitor cells derived from HUCB improve not only glycemia but also other disease conditions, including systemic lupus erythematosis, amyotrophic lateral sclerosis, Alzheimer's disease, stroke, brain damage in animals and certain malignancies in humans. Transfusion of unrelated HUCB, although abundantly available, is underutilized as a therapeutic agent. Therefore, we propose the hypothesis that transfusion of HUCB to low birth weight infants be considered a therapeutic modality to prevent the development of type 2 diabetes in their adulthood.

Administration of human umbilical cord blood cells delays the onset of prostate cancer and increases the lifespan of the TRAMP mouse

Stem cell transplantation to improve the onset and survival of animals or humans with prostate cancer has not been studied adequately. In this study, we examined whether intravenous administration of human umbilical cord blood (HUCB) mononuclear cells into TRAMP (transgenic adenocarcinoma of the mouse prostate) mice can delay the onset of prostate cancer and improve survival of these mice before and after the development of cancer. Twenty TRAMP mice were randomly divided into 2 groups. One group of 10 mice received 200 x10(6) HUCB mononuclear cells retro-orbitally into the venous plexus at the age of 6 weeks. Another group of 10 mice did not receive HUCB cells and served as control mice. The presence of tumor was detected by abdominal palpation, which was confirmed by biopsy. When 4 of the 10 control mice developed the tumor, they were treated with the same dose of HUCB cells. Either at the time of death or sacrifice, various tissues were examined for the presence of HUCB cell total RNA by reverse transcriptase PCR. Also, the tissues were examined histologically for the presence of metastasis and carcinoma. Kaplan-Meier survival plots were used to assess the lifespan of the mice. The data show that the control mice developed the tumor much earlier than the treated mice (control vs treated: 238+/-38 vs 311+/-40 days; P<0.001). Also, transplantation of HUCB cells either before or after the development of tumor significantly increased the life span compared to that of control mice. Persistence of human RNA either in blood or spleen was associated with prolonged survival. No graft vs host disease was observed in any of the mice. In conclusion, transplantation of HUCB mononuclear cells via intravenous administration into TRAMP mice retards not only the development of prostate cancer but also increases the lifespan of these mice.

Sertoli cells improve survival of motor neurons in SOD1 transgenic mice, a model of amyotrophic lateral sclerosis

Cell replacement therapy has been widely suggested as a treatment for multiple diseases including motor neuron disease. A variety of donor cells have been tested for treatment including isolated preparations from bone marrow and embryonic spinal cord. Another cell source, Sertoli cells, have been successfully used in models of diabetes, Parkinson's disease and Huntington's disease. The ability of these cells to secrete cytoprotective proteins and their role as 'nurse cells' supporting the function of other cell types in the testes suggest their potential use as neuroprotective cells. The current study examines the ability of Sertoli cells injected into the parenchyma of the spinal cord to protect motor neurons in a mouse model for amyotrophic lateral sclerosis. Seventy transgenic mice expressing the mutant (G93A) human Cu-Zn superoxide dismutase (SOD1) received a unilateral spinal injection of Sertoli-enriched testicular cells into the L4-L5 ventral horn (1 x 10(5) cells total) prior to the onset of clinical symptoms. The animals were euthanized at the end stage of the disease. Histological and morphometric analyses of the transplant site were performed. A significant increase in the number of surviving ChAT positive motor neurons was found ipsilateral to the injection compared with contralateral and uninjected spinal cord. The ipsilateral increase in motor neuron density was dependent upon proximity to the injection site. Sections rostral or caudal to the injection site did not display a similar difference in motor neuron density. Implantation of a Sertoli-cell-enriched preparation has a significant neuroprotective benefit to vulnerable motor neurons in the SOD1 transgenic model. The therapeutic benefit may be the result of secreted neurotrophic factors present at a critical stage of motor neuron degeneration in this model.

Amyotrophic lateral sclerosis: recent advances and future therapies

PURPOSE OF REVIEW

Amyotrophic lateral sclerosis is a rare but fatal motoneuron disorder. Despite intensive research riluzole remains the only available therapy, with only marginal effects on survival. Here we review some of the recent advances in the search for a disease-modifying therapy for amyotrophic lateral sclerosis.

RECENT FINDINGS

A number of established agents have recently been re-investigated for their potential as neuroprotective agents, including beta-lactam antibiotics and minocycline. Progress has also been made in exploiting growth factors for the treatment of amyotrophic lateral sclerosis, partly due to advances in developing effective delivery systems to the central nervous system. A number of new therapies have also been identified, including a novel class of compounds, heat-shock protein co-inducers, which upregulate cell stress responses thereby mediating neuroprotection. Non-drug-based therapies are also under development, with progress in gene-silencing and stem cell therapies.

SUMMARY

In the past few years, significant advances have been made in both our understanding of amyotrophic lateral sclerosis pathogenesis and the development of new therapeutic approaches. However, caution must be exercised in view of the long-standing failure to successfully transfer therapeutic compounds to the clinic. A deeper awareness in the research community of the need for clinically relevant preclinical studies, coupled with a better understanding of the issues surrounding clinical trial design for amyotrophic lateral sclerosis, offers hope that the growing list of validated preclinical therapeutics can finally yield an effective disease-modifying treatment.

Stroke-induced Migration of Human Umbilical Cord Blood Cells: Time Course and Cytokines

The therapeutic window for treatment of individuals after stroke is narrow, regardless of the treatment regime; extension of this window would provide a major therapeutic advance. In prior reports, we demonstrated significant improvements in the behavioral defects of rats that received human umbilical cord blood (HUCB) cells 24 h after a middle cerebral arterial occlusion. These effects paralleled the recruitment of these cells to the site of tissue damage. While the administration of HUCB cells 24 h after stroke was effective, the optimal time to administer these cells after stroke has not been established. Here, we investigated the migration of HUCB cells to ischemic tissue extracts. After ischemic assault, brain tissue was homogenized, and the supernatants were assayed for their ability to attract HUCB mononuclear cells as well as for levels of several cytokines. We demonstrate increased migratory activity of HUCB cells toward the extracts harvested at 24-72 h after stroke. The extracts possessed increased levels of certain cytokines and chemokines, suggesting their participation in HUCB cell migration. The results from this study are promising in that the current 3-h therapeutic window for the treatment of stroke victims, using approved anticoagulant treatment, may be extended with the use of HUCB cell therapy 24-72 h post stroke. Last, the chemokines present in the supernatant provide a sound starting point to start examining the mechanisms responsible for the in vivo migration of HUCB cells after the induction of stroke.

Cellular genetic therapy

Cellular genetic therapy is the ultimate frontier for those pathologies that are consequent to a specific nonfunctional cellular type. A viable cure for there kinds of diseases is the replacement of sick cells with healthy ones, which can be obtained from the same patient or a different donor. In fact, structures can be corrected and strengthened with the introduction of undifferentiated cells within specific target tissues, where they will specialize into the desired cellular types. Furthermore, consequent to the recent results obtained with the transdifferentiation experiments, a process that allows the in vitro differentiation of embryonic and adult stem cells, it has also became clear that many advantages may be obtained from the use of stem cells to produce drugs, vaccines, and therapeutic molecules. Since stem cells can sustain lineage potentials, the capacity for differentiation, and better tolerance for the introduction of exogenous genes, they are also considered as feasible therapeutic vehicles for gene therapy. In fact, it is strongly believed that the combination of cellular genetic and gene therapy approaches will definitely allow the development of new therapeutic strategies as well as the production of totipotent cell lines to be used as experimental models for the cure of genetic disorders.

Human umbilical cord blood progenitors: the potential of these hematopoietic cells to become neural

The mononuclear fraction from human umbilical cord blood (HUCB) contains a significant number of stem/progenitor cells that in theory could be come any cell in the body, including neurons. Taking into consideration that transdifferentiation would be a very rare event and also knowing that overlapping genetic programs for hematopoiesis and neuropoiesis exist, we undertook a characterization of the HUCB mononuclear fraction, including analysis of cellular subpopulations and their morphology, cell viability, proliferation, and expression of neural and hematopoietic antigens. Two cell populations were apparent-adherent and floating fractions. The adherent fraction was mainly lymphocytes (~53%) expressing hematopoietic antigens. Upon replate, the floating population had many cells that expressed stem cell antigens. More of the cells in this subfraction expressed neural proteins. Neurotrophin receptors trkB and trkC were present in both cell fractions, although expression was higher in the floating fraction. Our initial characterization suggests that a subpopulation of cells exists within the HUCB mononuclear fraction that seems to have the potential to become neural cells, which could then be used in the development of cell-based therapies for brain injuries and diseases.

Transplantation of Human Umbilical Cord Blood-Derived Adherent Progenitors Into the Developing Rodent Brain

The results of several recent studies suggest that human umbilical cord blood (HUCB)-derived cells have the potential to undergo neural differentiation both in vitro and in vivo. Transplantation into the embryonic ventricular zone provides a unique opportunity to study the migration and differentiation of nonneural somatic progenitor cells in response to instructive cues within the developing neuroepithelium. We isolated an adherently growing population of HUCB-derived cells expressing CD13, CD29, CD49e, CD71, CD73, CD166, Flk-1, and vimentin but lacking CD34 and CD45. On transplantation into the ventricles of embryonic day 16.5 rat embryos, these cells formed subventricular clusters that extended into a variety of host brain regions, including striatum, cortex, hippocampus, thalamus, hypothalamus, tectum, pons, and cerebellum. Donor cells identified with an antibody to human nuclei or human-specific DNA in situ hybridization maintained expression of their original marker antigens and showed no expression of the neural markers MAP2 and NeuN (neurons), GFAP (astrocytes), and CNP (oligodendrocytes). In contrast to grafted primary neural cells, they remained largely confined to subventricular clusters with little evidence for intraparenchymal integration. Thus, the neurogenic environment of the embryonic ventricular zone does not promote the elaboration of a neural phenotype in HUCB-derived cells.

Transplantation of Human Umbilical Cord Blood Cells Benefits an Animal Model of Sanfilippo Syndrome Type B

Sanfilippo syndrome type B is caused by alpha-N-acetylglucosaminidase (Naglu) enzyme deficiency leading to an accumulation of undegraded heparan sulfate, a glycosaminoglycan (GAG). Cell therapy is a promising new treatment and human umbilical cord blood (hUCB) cell transplantation may be preferred for delivery of the missing enzyme. We investigated the ability of mononuclear hUCB cells administered into the lateral cerebral ventricle to ameliorate/prevent histopathological changes in mice modeling Sanfilippo syndrome type B. These are the first results supporting enzyme replacement by administered hUCB cells. In vivo, transplanted hUCB cells survived long-term (7 months), migrated into the parenchyma of the brain and peripheral organs, expressed neural antigens, and exhibited neuron and astrocyte-like morphology. Transplant benefits were also demonstrated by stable cytoarchitecture in the hippocampus and cerebellum, and by reduced GAGs in the livers of treated mutant mice. A hUCB cell transplant may be an effective therapeutic strategy for enzyme delivery in Sanfilippo syndrome type B.

Human cord blood stem cells generate human cytokeratin 18-negative hepatocyte-like cells in injured mouse liver

Differentiation of adult bone marrow (BM) cells into nonhematopoietic cells is a rare phenomenon. Several reports, however, suggest that human umbilical cord blood (hUCB)-derived cells give rise to hepatocytes after transplantation into nonobese diabetic-severe combined immunodeficient (NOD-SCID) mice. Therefore, we analyzed the hepatic differentiation potential of hUCB cells and compared the frequency of newly formed hepatocyte-like cells in the livers of recipient NOD-SCID mice after transplantation of hUCB versus murine BM cells. Mononuclear cell preparations of hUCB cells or murine BM from enhanced green fluorescent protein transgenic or wild-type mice were transplanted into sublethally irradiated NOD-SCID mice. Liver regeneration was induced by carbon tetrachloride injury with and without subsequent hepatocyte growth factor treatment. By immunohistochemistry and reverse transcriptase-polymerase chain reaction, we detected clusters of hepatocyte-like cells in the livers of hUCB-transplanted mice. These cells expressed human albumin and Hep Par 1 but mouse CK18, suggesting the formation of chimeric hepatocyte-like cells. Native fluorescence microscopy and double immunofluorescence failed to detect single hepatocytes derived from transplanted enhanced green fluorescent protein-transgenic mouse BM. Fluorescent in situ hybridization rarely revealed donor-derived hepatocyte-like cells after cross-gender mouse BM transplantation. Thus, hUCB cells have differentiation capabilities different from murine BM cells after transplantation into NOD-SCID mice, demonstrating the importance of further testing before hUCB cells can be used therapeutically.

Healing a broken heart with stem cells

We discuss here the rapid progress of stem cell therapy in myocardial infarction. In particular, we focus on the issue of transdifferentiation as a "hallmark" of the stem cell's potential to replace damaged cells of the heart. A study by Henning and colleagues in this issue of Cell Transplantation supports the alternative notion of a nontransdifferentiation-mediated protection of the heart as an equally robust mechanism underlying the therapeutic potential of stem cells.

Engraftment of freshly isolated or cultured human umbilical cord blood cells and the effect of cyclosporin A on the outcome

Human umbilical cord blood (HUCB) is a potentially valuable resource for cell therapy. The present study investigated the short-term survival of intrastriatal grafts of either freshly isolated or cultured HUCB cells and the effect of the immunosuppressive agent cyclosporin A (CSA) in host rat brains. The group injected with either freshly isolated or cultured HUCB cells was subdivided into CSA or saline controls. Freshly isolated and cultured HUCB cells displayed surface markers CD33, CD44, CD45, CD51/61 and CD90/Thy-1. The hematopoietic progenitor marker CD34 was expressed only in freshly isolated cells. The majority of injected HUCB cells were localized within a 500-mum radius from the injection site in the striatum; however, a subpopulation migrated along the corpus callosum. There was no significant statistical difference in the cell count between freshly isolated and cultured HUCB cells with or without CSA. Some grafted HUCB cells expressed either a neural or microglial marker. There was weak up-regulation of major histocompatibility complex (MHC) class I antigen in rats either with or without CSA. However, there were considerably fewer positive cells labeled with an MHC class II antigen in CSA groups. These results suggest that neither freshly isolated nor cultured HUCB cells induce acute rejection after intrastriatal transplantation up to 14 days. CSA suppressed up-regulation of MHC class II antigen in the host brain.

Neural stem cells and their use as therapeutic tool in neurological disorders

Spontaneous neural tissue repair occurs in patients affected by inflammatory and degenerative disorders of the central nervous system (CNS). However, this process is not robust enough to promote a functional and stable recovery of the CNS architecture. The development of cell-based therapies aimed at promoting brain repair, through damaged cell-replacement, is therefore foreseen. Several experimental cell-based strategies aimed at replacing damaged neural cells have been developed in the last 30 years. Although successful in promoting site-specific repair in focal CNS disorders, most of these therapeutic approaches have failed to foster repair in multifocal CNS diseases where the anatomical and functional damage is widespread. Stem cell-based therapies have been recently proposed and might represent in the near future a plausible alternative strategy in these disorders. However, before envisaging any human applications of stem cell-based therapies in neurological diseases, we need to consider some preliminary and still unsolved issues: (i) the ideal stem cell source for transplantation, (ii) the most appropriate route of stem cell administration, and, last but not least, (iii) the best approach to achieve an appropriate, functional, and long-lasting integration of transplanted stem cells into the host tissue.

Pluripotent fates and tissue regenerative potential of adult olfactory bulb neural stem and progenitor cells

Neural stem cells and progenitor cells reside in the adult olfactory bulb (OB) core of mouse, rat, and human. Adult rodent OB core cells have the capacities for self-renewal and multipotency and form neurospheres. The differentiation fates of these neurosphere-forming cells were studied in vitro and in vivo. Adult OB neurospheres were comprised of stem cells and neuronal and glial progenitor cells. OB neurospheres in co-culture with primary embryonic striatal neurons and cortical neurons generated cells with morphological and neurochemical phenotypes of striatal and cortical neurons, respectively. Transplanted OB cells, delivered as dissociated cells or as intact neurospheres, dispersed, survived for long-term, extended neurites, migrated, expressed neuronal or glial markers, and formed synapses with host neurons when placed into the environment of the nonlesioned and lesioned central nervous system (CNS). Grafted cells in the CNS also showed angiogenic capacity by forming blood vessels. In a model of spinal motor neuron degeneration, adult OB neurosphere cells transplanted into lesioned spinal cord adopted phenotypes of motor neurons and had a robust potential to become oligodendrocytes. OB core cells in co-culture with skeletal myoblasts generated skeletal muscle cells. Chimeric skeletal muscle was formed when mouse OB neurospheres were transplanted into rat skeletal muscle. Within skeletal muscle, adult OB neurosphere cells became myogenic progenitor cells to form myotubes de novo. We conclude that the adult mammalian OB is a source of pluripotent neural stem cells and progenitor cells that have the potential to become, in a context-dependent manner, specific types of cells for regeneration of tissues in brain, spinal cord, and muscle.

Human umbilical cord blood cells express neurotrophic factors

Freshly isolated or culture-expanded human umbilical cord blood mononuclear cells (CBMNCs) have been known to express neural phenotypes in vitro and to differentiate into neural cells and improve neurological function recovery after being administrated into rodent models of neurological diseases. However, the mechanism of action remains unclear. The present study observed that CBMNCs expressed higher level mRNAs of several neurotrophic factors than adult peripheral blood mononuclear cells (PBMCs). In addition, a significantly increase in the levels of brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT4/5) was found in culture supernatants of CBMNCs compared to that of PBMNCs. These findings indicate that CBMNCs express several neurotrophic factors and suggest that the neurotrophic factors secreted by CBMNCs may be responsible for amelioration of central nervous system deficits in animal models after CBMNC administration.

Effect of human umbilical cord blood cells on glycemia and insulitis in type 1 diabetic mice

Several studies have shown that transplantation of embryonic stem cells into diabetic animals either improved or normalized blood glucose levels. In this study, we examined the dose-dependent effect of early (prediabetic stage) intravenous administration of human umbilical cord blood (HUCB) mononuclear cells on blood glucose levels, survival, and insulitis in nonobese diabetic (NOD) mice with autoimmune type 1 diabetes. The results show that mice treated with HUCB cells significantly lowered their blood glucose levels and increased their lifespan, as compared with untreated mice. Also, a significant reduction in insulitis was observed in treated than in untreated mice. The mice that received the highest dosage (200 x 10(6)) of cells had greater reduction in blood glucose levels and the degree of insulitis than the mice that received lower dosage (100-150 x 10(6)) of cells. Prolonged lifespan in the former group of mice seems to be related to better control of blood glucose levels. Thus, administration of HUCB cells in the prediabetic stage without any immunosuppression improves type 1 diabetes by protecting the islets from insulitis in NOD mice.

Wild-type bone marrow cells ameliorate the phenotype of SOD1-G93A ALS mice and contribute to CNS, heart and skeletal muscle tissues

Amyotrophic lateral sclerosis (ALS) is a progressive, lethal neurodegenerative disease without any effective therapy. To evaluate the potential of wild-type bone marrow (BM)-derived stem cells to modify the ALS phenotype, we generated BM chimeric Cu/Zn superoxide dismutase (SOD1) mice by transplantation of BM cells derived from mice expressing green fluorescent protein (GFP) in all tissues and from Thy1-YFP mice that express a spectral variant of GFP (yellow fluorescent protein) in neurons only. In the recipient cerebral cortex, we observed rare GFP+ and YFP+ neurons, which were probably generated by cell fusion, as demonstrated by fluorescence in situ hybridization (FISH) analysis, suggesting that this phenomenon is not limited to Purkinje cells. GFP-positive microglial cells were extensively present in both the brain and spinal cord of the affected animals. Completely differentiated and immature GFP+ myofibres were also present in the heart and skeletal muscles of SOD1 mice, confirming that BM cells can participate in striated muscle tissue regeneration. Moreover, wild-type BM chimeric SOD1 mice showed a significantly delayed disease onset and an increased life span, probably due to a positive 'non-neuronal environmental' effect rather than to neuronogenesis. This improvement in SOD1-G93A mouse survival is comparable with that previously obtained using some safer pharmacological agents. BM transplantation-related complications in humans preclude its clinical application for ALS treatment. However, our data suggest that further studies aimed at improving the degree of tissue chimerism by BM-derived cells may provide valuable insights into strategies to slow ALS progression.

Minimally invasive delivery of stem cells for spinal cord injury: advantages of the lumbar puncture technique

Object. Stem cell therapy has been shown to have considerable therapeutic potential for spinal cord injuries (SCIs); however, most experiments in animals have been performed by injecting cells directly into the injured parenchyma. This invasive technique compromises the injured spinal cord, although it delivers cells into the hostile environment of the acutely injured cord. In this study, the authors tested the possibility of delivering stem cells to injured spinal cord by using three different minimally invasive techniques.

Methods. Bone marrow stromal cells (BMSCs) are clinically attractive because they have shown therapeutic potential in SCI and can be obtained in patients at the bedside, raising the possibility of autologous transplantation. In this study transgenically labeled cells were used for transplantation, facilitating posttransplantation tracking. Inbred Fisher-344 rats received partial cervical hemisection injury, and 2 × 106 BMSCs were intravenously, intraventricularly, or intrathecally transplanted 24 hours later via lumbar puncture (LP). The animals were killed 3, 10, or 14 days posttransplantation, and tissue samples were submitted to histochemical and immunofluorescence analyses. For additional comparison and validation, lineage restricted neural precursor (LRNP) cells obtained from E13.5 rat embryos were transplanted via LP, and these findings were also analyzed.

Conclusions. Both BMSCs and LRNP cells home toward injured spinal cord tissues. The use of LP and intraventricular routes allows more efficient delivery of cells to the injured cord compared with the intravenous route. Stem cells delivered via LP for treatment of SCI may potentially be applicable in humans after optimal protocols and safety profiles are established in further studies.

Stem cell therapy for human neurodegenerative disorders-how to make it work

Recent progress shows that neurons suitable for transplantation can be generated from stem cells in culture, and that the adult brain produces new neurons from its own stem cells in response to injury. These findings raise hope for the development of stem cell therapies in human neurodegenerative disorders. Before clinical trials are initiated, we need to know much more about how to control stem cell proliferation and differentiation into specific phenotypes, induce their integration into existing neural and synaptic circuits, and optimize functional recovery in animal models closely resembling the human disease.

Stem-cell therapy for amyotrophic lateral sclerosis

CONTEXT

With the lack of effective drug treatments for amyotrophic lateral sclerosis (ALS), and compelling preclinical data, stem-cell research has highlighted this disease as a candidate for stem-cell treatment. Stem-cell transplantation is an attractive strategy for neurological diseases and early successes in animal models of neurodegnerative disease generated optimism about restoring function or delaying degeneration in human beings. The restricted potential of adult stem cells has been challenged over the past 5 years by reports on their ability to acquire new unexpected fates beyond their embryonic lineage (transdifferentiation). Therefore, autologous or allogeneic stem cells, undifferentiated or transdifferentiated and manipulated epigenetically or genetically, could be a candidate source for local or systemic cell-therapies in ALS.

STARTING POINT

Albert Clement and colleagues (Science 2003; 302: 113-17) showed that in SOD1G93A chimeric mice, motorneuron degeneration requires damage from mutant SOD1 acting in non-neuronal cells. Wild-type non-neuronal (glial) cells could delay degeneration and extend survival of mutant-expressing motorneurons. Letizia Mazzini and colleagues (Amyotroph Lateral Scler Other Motor Neuron Disord 2003; 4: 158-61) injected autologous bone-marrow-derived stem cells into the spinal cord of seven ALS patients. These investigators reported that the procedure had a reasonable margin of clinical safety. WHERE NEXT? The success of cell-replacement therapy in ALS will depend a lot on preclinical evidence, because of the complexity and precision of the pattern of connectivity that needs to be restored in degenerating motoneurons. Stem-cell therapy will need to be used with other drugs or treatments, such as antioxidants and/or infusion of trophic molecules.