BDNF improves the effects of neural stem cells on the rat model of Alzheimer's disease with unilateral lesion of fimbria-fornix. Neurosci Lett. 2008;440:331-335. [PMID: 18579298 DOI: 10.1016/j.neulet.2008.05.107]

Clinical experience with stem cells and other cell therapies in neurological diseases

To overcome the limited capacity of the CNS for regeneration, the theoretical alternative would be to use stem cells for more effective management of chronic degenerative and inflammatory neurological conditions, and also of acute neuronal damage from injuries or cerebrovascular diseases. Although the adult brain contains small numbers of stem cells in restricted areas, this intrinsic stem cell repertoire is small and does not measurably contribute to functional recovery. Embryonic cells carrying pluripotent and self-renewal properties represent the stem cell prototype, but there are additional somatic stem cells that may be harvested and expanded from various tissues during adult life. Stem cell transplantation is based on the assumption that such cells may have the potential to regenerate or support the survival of the existing, partially damaged cells. This review summarizes the state-of-the-art and the clinical worldwide experience with the use of various types of stem cells in neurological diseases.

Recent preclinical evidence advancing cell therapy for Alzheimer's disease

Alzheimer's disease (AD) causes brain degeneration, primarily depleting cholinergic cells, and leading to cognitive and learning dysfunction. Logically, to augment the cholinergic cell loss, a viable treatment for AD has been via drugs boosting brain acetylcholine production. However, this is not a curative measure. To this end, nerve growth factor (NGF) has been examined as a possible preventative treatment against cholinergic neuronal death while enhancing memory capabilities; however, NGF brain bioavailability is challenging as it does not cross the blood-brain barrier. Investigations into stem cell- and gene-based therapy have been explored in order to enhance NGF potency in the brain. Along this line of research, a genetically modified cell line, called HB1.F3 transfected with the cholinergic acetyltransferase or HB1.F3.ChAT cells, has shown safety and efficacy profiles in AD models. This stem cell transplant therapy for AD is an extension of the neural stem cells' use in other neurological treatments, such as Parkinson's disease and stroke, and recently extended to cancer. The HB1 parent cell and its associated cell lines have been used as a vehicle to deliver genes of interest in various neurological models, and are highly effective as they can differentiate into neurons and glial cells. A focus of this mini-review is the recent demonstration that the transplantation of HB1.F3.ChAT cells in an AD animal model increases cognitive function coinciding with upregulation of acetylcholine levels in the cerebrospinal fluid. In addition, there is a large dispersion throughout the brain of the transplanted stem cells which is important to repair the widespread cholinergic cell loss in AD. Some translational caveats that need to be satisfied prior to initiating clinical trials of HB1.F3.ChAT cells in AD include regulating the host immune response and the possible tumorigenesis arising from the transplantation of this genetically modified cell line. Further studies are warranted to test the safety and effectiveness of these cells in AD transgenic animal models. This review highlights the recent progress of stem cell therapy in AD, not only emphasizing the significant basic science strides made in this field, but also providing caution on remaining translational issues necessary to advance this novel treatment to the clinic.

Alzheimer's disease: biological aspects, therapeutic perspectives and diagnostic tools

Alzheimer's disease (AD) is the most common form of dementia among older people. Dementia is an irreversible brain disorder that seriously affects a person's ability to carry out daily activities. It is characterized by loss of cognitive functioning and behavioral abilities, to such an extent that it interferes with the daily life and activities of the affected patients. Although it is still unknown how the disease process begins, it seems that brain damage starts a decade or more before problems become evident. Scientific data seem to indicate that changes in the generation or the degradation of the amyloid-b peptide (Aβ) lead to the formation of aggregated structures that are the triggering molecular events in the pathogenic cascade of AD. This review summarizes some characteristic features of Aβ misfolding and aggregation and how cell damage and death mechanisms are induced by these supramolecular and toxic structures. Further, some interventions for the early diagnosis of AD are described and in the last part the potential therapeutic strategies adoptable to slow down, or better block, the progression of the pathology are reported.

Protoplasmic astrocytes enhance the ability of neural stem cells to differentiate into neurons in vitro

Protoplasmic astrocytes have been reported to exhibit neuroprotective effects on neurons, but there has been no direct evidence for a functional relationship between protoplasmic astrocytes and neural stem cells (NSCs). In this study, we examined neuronal differentiation of NSCs induced by protoplasmic astrocytes in a co-culture model. Protoplasmic astrocytes were isolated from new-born and NSCs from the E13-15 cortex of rats respectively. The differentiated cells labeled with neuron-specific marker β-tubulin III, were dramatically increased at 7 days in the co-culture condition. Blocking the effects of brain-derived neurotrophic factor (BDNF) with an anti-BDNF antibody reduced the number of neurons differentiated from NSCs when co-cultured with protoplasmic astrocytes. In fact, the content of BDNF in the supernatant obtained from protoplasmic astrocytes and NSCs co-culture media was significantly greater than that from control media conditions. These results indicate that protoplasmic astrocytes promote neuronal differentiation of NSCs, which is driven, at least in part, by BDNF.

Human neural stem cells genetically modified to express human nerve growth factor (NGF) gene restore cognition in the mouse with ibotenic acid-induced cognitive dysfunction

Alzheimer's disease (AD) is characterized by degeneration and loss of neurons and synapses throughout the brain, causing the progressive decline in cognitive function leading to dementia. No effective treatment is currently available. Nerve growth factor (NGF) therapy has been proposed as a potential treatment of preventing degeneration of basal forebrain cholinergic neurons in AD. In a previous study, AD patient's own fibroblasts genetically modified to produce NGF were transplanted directly into the brain and protected cholinergic neurons from degeneration and improved cognitive function in AD patients. In the present study, human neural stem cells (NSCs) are used in place of fibroblasts to deliver NGF in ibotenic acid-induced learning-deficit rats. Intrahippocampal injection of ibotenic acid caused severe neuronal loss, resulting in learning and memory deficit. NGF protein released by F3.NGF human NSCs in culture medium is 10-fold over the control F3 naive NSCs at 1.2 µg/10(6) cells/day. Overexpression of NGF in F3.NGF cells induced improved survival of NSCs from cytotoxic agents H2O2, Aβ, or ibotenic acid in vitro. Intrahippocampal transplantation of F3.NGF cells was found to express NGF and fully improved the learning and memory function of ibotenic acid-challenged animals. Transplanted F3.NGF cells were found all over the brain and differentiated into neurons and astrocytes. The present study demonstrates that human NSCs overexpressing NGF improve cognitive function of learning-deficit model mice.

Human neural stem cells over-expressing choline acetyltransferase restore cognition in rat model of cognitive dysfunction

A human neural stem cell (NSC) line over-expressing human choline acetyltransferase (ChAT) gene was generated and these F3.ChAT NSCs were transplanted into the brain of rat Alzheimer disease (AD) model which was induced by application of ethylcholine mustard aziridinium ion (AF64A) that specifically denatures cholinergic nerves and thereby leads to memory deficit as a salient feature of AD. Transplantation of F3.ChAT human NSCs fully recovered the learning and memory function of AF64A animals, and induced elevated levels of acetylcholine (ACh) in cerebrospinal fluid (CSF). Transplanted F3.ChAT human NSCs were found to migrate to various brain regions including cerebral cortex, hippocampus, striatum and septum, and differentiated into neurons and astrocytes. The present study demonstrates that brain transplantation of human NSCs over-expressing ChAT ameliorates complex learning and memory deficits in AF64A-cholinotoxin-induced AD rat model.

The effects of different phenotype astrocytes on neural stem cells differentiation in co-culture

Astrocytes were reported to show neuroprotective effects on neurons, but there was no direct evidence for a functional relationship between astrocytes and neural stem cells (NSCs). In this experiments, we examined neuronal differentiation of NSCs induced by protoplasmic and fibrous astrocytes in a co-culture model respectively. Two types of astrocytes and NSCs were isolated from E13 to 15 cortex of rats. The neuronal differentiation of NSCs was examined after co-culture with two kinds of astrocytes. There were more neuronal marker β-tublin III positive cells from NSCs co-cultured with protoplasmic astrocytes. However the differentiated neurons, whether co-cultured with protoplasmic astrocytes or fibrous astrocytes, both expressed glutamate AMPA receptor subunit GluR2 protein and exhibited biological electrical reactivity after stimulated by glutamine. Therefore, these findings indicated that two types of astrocytes could induce the differentiation of NSCs and also possibly induce functional maturation of differentiated neurons, among which protoplasmic astrocytes have the ability to promote neuronal differentiation of NSCs compared with fibrous astrocytes.

Stem cell technology for neurodegenerative diseases

Over the past 20 years, stem cell technologies have become an increasingly attractive option to investigate and treat neurodegenerative diseases. In the current review, we discuss the process of extending basic stem cell research into translational therapies for patients suffering from neurodegenerative diseases. We begin with a discussion of the burden of these diseases on society, emphasizing the need for increased attention toward advancing stem cell therapies. We then explain the various types of stem cells utilized in neurodegenerative disease research, and outline important issues to consider in the transition of stem cell therapy from bench to bedside. Finally, we detail the current progress regarding the applications of stem cell therapies to specific neurodegenerative diseases, focusing on Parkinson disease, Huntington disease, Alzheimer disease, amyotrophic lateral sclerosis, and spinal muscular atrophy. With a greater understanding of the capacity of stem cell technologies, there is growing public hope that stem cell therapies will continue to progress into realistic and efficacious treatments for neurodegenerative diseases.

Human neural stem cells overexpressing choline acetyltransferase restore cognitive function of kainic acid-induced learning and memory deficit animals

Alzheimer disease (AD) is a progressive neurodegenerative disease, which is characterized by loss of memory and cognitive function. In AD patients dysfunction of the cholinergic system is the main cause of cognitive disorders, and decreased activity of choline acetyltransferase (ChAT), an enzyme responsible for acetylcholine (ACh) synthesis, is observed. In the present study we investigated if brain transplantation of human neural stem cells (NSCs) genetically modified to encode ChAT gene improves cognitive function of kainic acid (KA)-induced learning deficit rats. Intrahippocampal injection of KA to hippocampal CA3 region caused severe neuronal loss, resulting in profound learning and memory deficit. F3.ChAT human NSCs transplanted intracerebroventricularly improved fully the learning and memory function of KA-induced learning deficit animals, in parallel with the elevation of ACh levels in cerebrospinal fluid. F3.ChAT human NSCs migrated to the KA-induced injury site (CA3) and differentiated into neurons and astrocytes. The present study demonstrates that human NSCs expressing ChAT have lesion-tropic property and improve cognitive function of learning deficit model rats with hippocampal injury by increasing ACh level.

BDNF concentrations are decreased in serum and parietal cortex in immunotoxin 192 IgG-Saporin rat model of cholinergic degeneration

The neurotrophin brain-derived neurotrophic factor (BDNF) has been extensively studied because of its role in survival, differentiation and function of neurons undergoing degeneration in pathological conditions such as cholinergic neurons in Alzheimer's disease (AD). However, despite these evidences, the role of BDNF in these events is still matter of debate because central and peripheral BDNF levels are often found in opposite direction. Another puzzling factor is represented by pharmacological treatments known to cause alterations of BDNF peripheral levels. Thus, a pivotal issue would be to verify whether brain and serum BDNF changes are interconnected as well as the possibility that different stages of cholinergic degeneration are characterized by different changes in BDNF brain and serum levels. With this in mind in this study we used a rat model of cholinergic degeneration based on intracerebroventricular (i.c.v.) injections of 192 IgG-Saporin and measured brain and serum BDNF concentrations by enzyme-linked immunosorbent assay (ELISA) at 3, 7 and 15days from immunotoxin injection. We found that BDNF levels were reduced in parietal cortex and serum of Saporin-treated rats at 15days from lesion. Moreover, a positive correlation between serum and parietal cortex was observed at 15days from lesion. These alterations were not present at the earlier post-operative time points. In conclusion, this study shows that BDNF levels are reduced in a rat model of cholinergic degeneration and suggests that these alterations may occur at later stages. In addition, a positive correlation between serum and parietal cortex changes is observed. Even if the cause for the relationship between BDNF in serum and this brain region is unknown, these data may help to elucidate the significance of peripheral and central BDNF changes in brain pathological conditions.

Physical exercise alleviates debilities of normal aging and Alzheimer's disease

Both healthy aging and the pathologic incidence of disorders associated with aging involve an array of debilities. Physical exercise harnesses implicit and inherent biologic characteristics amenable to the putative interventional influences under clinical, institutional or laboratory conditions. The neurodegenerative and pathophysiologic progressions that constitute Alzheimer's disease (AD), amnestic mild cognitive impairment (aMCI), normal aging, and different animal models of AD have shown the existence of several putative mechanisms. A large variety of moderating factors have demonstrated that the ever-proliferating plethora of neurotrophic factors, neurogenesis as observed through generality of expression and neuronal arborization. The insistent efficacy of brain vascular angiogenesis may delay also the comorbid incidence of depressive disorders with dementia pathology. The pathogenesis of aging may be contained by selective treatments: these diverse conditions, linked to the basis of the aging concept, have been shown, to greater or lesser extents, to respond to a variety of scheduled applications of physical exercise. The range of reports that provide accounts of the mechanisms mediating the positive progressive response to exercise intervention is far-ranging; these studies indicate that subtle changes at molecular, neuronal, vascular and epigenetic levels may exert notable consequence at functional expression and, perhaps most essentially, offer convincing expectancy of significant benefits.

Biological mechanisms of physical activity in preventing cognitive decline

In order to guarantee better conditions for competition, the nervous system has developed not only mechanisms controlling muscle effectors, but also retrograde systems that, starting from peripheral structures, may influence brain functions. Under such perspective, physical activity could play an important role in influencing cognitive brain functions including learning and memory. The results of epidemiological studies (cross-sectional, prospective and retrospective) support a positive relationship between cognition and physical activities. Recent meta-analysis confirmed a significant effect of exercise on cognitive functions. However, the biological mechanisms that underlie such beneficial effects are still to be completely elucidated. They include supramolecular mechanisms (e.g. neurogenesis, synaptogenesis, and angiogenesis) which, in turn, are controlled by molecular mechanisms, such as BDNF, IGF-1, hormone and second messengers.

Capillary electrophoresis of bone marrow stromal cells with uptake of heparin-functionalized poly(lactide-co-glycolide) nanoparticles during differentiation towards neurons

This study analyzes the varying electrophoretic mobility and zeta potential of bone marrow stromal cells (BMSCs) during their differentiation towards neurons. Electrophoresis of primary BMSCs and neuron growth factor (NGF)-induced neuron-like cells with the uptake of heparin-functionalized poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) are also investigated. Immunofluorescent images revealed that a high concentration of NGF accelerated the differentiation of BMSCs into neurons. When the concentration of NGF increased, the absolute values of electrophoretic mobility and zeta potential of the differentiating BMSCs increased. In addition, a longer inductive period yielded higher charge of the differentiating BMSCs and a smaller uptake amount of heparin-functionalized PLGA NPs. However, an increase in the loading efficiency of heparin on PLGA NPs enhanced the uptake and reduced the electrical characteristics of the primary and differentiating BMSCs. Hence, a general rule is drawn that an increase in the uptake of heparin-functionalized PLGA NPs decreased the electrophoretic mobility and zeta potential of BMSCs during differentiation towards neurons.

Recombinant human NGF-loaded microspheres promote survival of basal forebrain cholinergic neurons and improve memory impairments of spatial learning in the rat model of Alzheimer's disease with fimbria-fornix lesion

Neurotrophic factors are used for the experimental treatment of neurological disorders, such as Alzheimer's disease. However, delivery of the neurotrophic factors into the brain remains a big challenge. Recombinant human nerve growth factor (NGF)-loaded microspheres were fabricated and characterized in vitro and in vivo in our previous study. The present study was to assess the therapeutic benefit of rhNGF-loaded microspheres in treating the rat model of Alzheimer's disease with fimbria-fornix lesion. Recombinant human NGF-loaded microspheres were implanted into the basal forebrain of the rats with fimbria-fornix lesion. Four weeks after implantation in the basal forebrain, immunohistochemical analysis showed that rhNGF-loaded microspheres had a significant effect on the survival of axotomized cholinergic neurons in the medial septum (MS) and vertical diagonal branch (VDB) (p<0.05). Y-maze tests showed rhNGF-loaded microspheres can significantly improve the ability of spatial learning and memory of the rats with fimbria-fornix lesion (p<0.05). These results indicate that rhNGF-loaded microspheres are an effective means for the treatment of Alzheimer's disease.

Effects of engrafted neural stem cells in Alzheimer's disease rats

Cell therapy is thought to have a central role in restorative therapy, which aims to restore the function of the damaged nervous system. Neural stem cells (NSCs) can differentiate into neurons, astrocytes and oligodendrocytes. The purpose of this study was to evaluate the therapeutic effects of transplanting NSCs into rats which have the animal model of Alzheimer's disease (AD). NSCs from the hippocampus and NSCs-derived glial cells labeled with 5'-Bromo-2'-deoxyuridine (BrdU) were transplanted into two groups of transected rat basal forebrain. Nestin staining, glial fibrillary acidic protein (GFAP) staining and double-labeling immunofluorescence were used to detect the engrafted cells in the basal forebrain. Immunohistochemical detection of p75(NGFR) showed that the number of cholinergic neurons of the NSCs-transplanted group was significant higher than that of the glia-transplanted group in medial septum (MS) and vertical diagonal branch (VDB) (P<0.05). Learning and memory abilities were also measured by Y-maze test. The results indicate that transplanted NSCs can differentiate into cholinergic neurons, which may play an important role in the therapeutic effects of transplanted NSCs.