Stem cell therapy for neurological disease and injury

Despite the anatomical protection provided to the central nervous system (CNS) by the skull and vertebral column, it is still vulnerable to a variety of injuries as well as a number of neurodegenerative diseases. There is little endogenous repair of the CNS, so functional recovery from injury is typically modest. Most neurodegenerative diseases are progressive in their course and few effective therapies exist to delay this disease progression or to promote any recovery. With the understanding that the adult brain can support the generation of new neurons in certain locations and with advances in understanding the biology of such stem or progenitor cells, there is now considerable hope that neural or non-neural derived stem cells can be used for structural brain repair. This review provides an overview of our current understanding of the biology of neural stem cells and their ability to integrate into the mature CNS. The prospects for using grafted stem cells or recruiting endogenous stem cells to treat neurological injury or disease are evaluated.     

A stem cell ... is stem cell?

We are used to associate stem cells with renewable tissues such as blood, gut and skin. But some cells in the adult central nervous system have the capacity to generate new neurons and glial cells as well and as such, they are considered to be neural stem cell. Yet their ability to generate neurons and glia, and their presence in the central nervous system throughout life, suggests new, intriguing possibilities for recovery and repair after damage to the central nervous system--and unexpectedly, the regeneration of blood tissues. After transplantation into irradiated hosts, neural stem cells were found to produce a variety of blood cell types including myeloid and lymphoid cells as well as early hematopoietic cells. Therefore, the developmental potential of stem cells is not restricted to the differentiated elements of the tissue in which they reside. Multipotential stem cells can persist in an undifferentiated state, and depending on specific environmental conditions function as a stem cell for many different tissues.     

Neurogenesis and neurodegenerative diseases in human

Acute and chronic neurodegenerative diseases are the most common neurological disorders in human and affect millions of individuals worldwide. While the specific clinical presentation varies among such diseases, their common feature is neural cell death. Yet, despite major advances in the understanding of neural cell death, effective treatment for these diseases remains one of the foremost challenges for medicine today. The transplantation of embryonic cells into the diseased brain in human has emerged out a mere theory and is possible as a practical application. This advancement, however, has raised important ethical, technical and immunological concerns. Studies have documented that neurogenesis occurs in the adult brain and that endogenous neural stem/progenitor cells (NSCs) respond to neurodegenerative diseases, suggesting that it might be possible for dead or injured neural cells to be replaced by endogenous NSCs. In this regard it is especially interesting to know the biological behaviors of endogenous NSCs in response to neurodegenerative diseases. Understanding the mechanisms underlying these changes could lead to the development of new strategies for treating neurological diseases using endogenous NSC pool.     

神经干细胞移植的方法选择及其在脊髓损伤中的应用

脊髓损伤是一种创伤性中枢神经系疾病,常伴有脊髓损伤平面以下感觉、运动、自主神经功能丧失,常导致患者终身残疾,且并发症较多,甚至死亡。至今尚无有效的治疗方法从根本上修复已损伤的脊髓功能。神经干细胞具有自我更新、增殖和多向分化等潜能,其移植后可向神经元分化并替代已坏死的神经元,形成新的突触,重建神经通路促进脊髓功能的修复,为脊髓损伤患者的康复带来曙光。近年来许多科学家对神经干细胞进行基因修饰,基因调控,或联合其他细胞、生物材料以及改变移植时间、途径等多方面进行深入研究,来提高移植效率,虽然取得了长足的进展,但仍存在一些不足之处尚待进一步完善,如神经干细胞移植的途径、时机、次数的相关标准,移植细胞的免疫排斥、长期存活、定向分化,神经干细胞的来源及伦理,移植的安全性等。本文拟对神经干细胞移植方法,移植时间,移植途径进行综述,并对神经干细胞移植所存在的问题及应用前景进行展望。     

Possibilities of investigation and clinical application of adult human stem cells

Multipotent adult tissue stem cells have high plasticity and transdifferentiation ability. The stem cell therapy can be the solution of curing many severe diseases such as osteogenesis imperfecta, hepatic failure, heart muscle damage after myocardial infarction, I-type diabetes, variety of central nervous system disorders such as brain injury, stroke, Parkinson's disease and other neurodegenerative disorders. Isolation of certain types of stem cells is solved nowadays, but low frequency of these cells and lack of special identification markers make their isolation and search more difficult. The more and more developed in vitro cell culture technologies, the widespread macromolecule amplification and examination techniques of molecular biology and the gene technology tools for genetic modification of stem (and other) cells contribute to research and therapeutic applications of stem cells. Transfer of new genetic material to stem cells and expression of the gene product in daughter cells--because missing or damaged genes can be replaced--is an exiting approach of the treatment of congenital (enzyme deficiencies) and acquired human diseases (cancers).     

Targeting DNA Methylation in the Adult Brain through Diet

Metabolism and nutrition have a significant role in epigenetic modifications such as DNA methylation, which can influence gene expression. Recently, it has been suggested that bioactive nutrients and gut microbiota can alter DNA methylation in the central nervous system (CNS) through the gut–brain axis, playing a crucial role in modulating CNS functions and, finally, behavior. Here, we will focus on the effect of metabolic signals in shaping brain DNA methylation during adulthood. We will provide an overview of potential interactions among diet, gastrointestinal microbiome and epigenetic alterations on brain methylation and behavior. In addition, the impact of different diet challenges on cytosine methylation dynamics in the adult brain will be discussed. Finally, we will explore new ways to modulate DNA hydroxymethylation, which is particularly abundant in neural tissue, through diet.     

Irradiation-injured brain tissues can self-renew in the absence of the pivotal tumor suppressor p53 in the medaka ( Oryzias latipes ) embryo

The tumor suppressor protein, p53, plays pivotal roles in regulating apoptosis and proliferation in the embryonic and adult central nervous system (CNS) following neuronal injuries such as those induced by ionizing radiation. There is increasing evidence that p53 negatively regulates the self-renewal of neural stem cells in the adult murine brain; however, it is still unknown whether p53 is essential for self-renewal in the injured developing CNS. Previously, we demonstrated that the numbers of apoptotic cells in medaka ( Oryzias latipes ) embryos decreased in the absence of p53 at 12–24 h after irradiation with 10-Gy gamma rays. Here, we used histology to examine the later morphological development of the irradiated medaka brain. In p53-deficient larvae, the embryonic brain possessed similar vacuoles in the brain and retina, although the vacuoles were much smaller and fewer than those found in wild-type embryos. At the time of hatching (6 days after irradiation), no brain abnormality was observed. In contrast, severe disorganized neuronal arrangements were still present in the brain of irradiated wild-type embryos. Our present results demonstrated that self-renewal of the brain tissue completed faster in the absence of p53 than wild type at the time of hatching because p53 reduces the acute severe neural apoptosis induced by irradiation, suggesting that p53 is not essential for tissue self-renewal in developing brain.     

Stem cell strategies for Alzheimer's disease therapy

We have found much evidence that the brain is capable of regenerating neurons after maturation. In our previous study, human neural stem cells (HNSCs) transplanted into aged rat brains differentiated into neural cells and significantly improved the cognitive functions of the animals, indicating that HNSCs may be a promising candidate for cell-replacement therapies for neurodegenerative diseases including Alzheimer's disease (AD). However, ethical and practical issues associated with HNSCs compel us to explore alternative strategies. Here, we report novel technologies to differentiate adult human mesenchymal stem cells, a subset of stromal cells in the bone marrow, into neural cells by modifying DNA methylation or over expression of nanog, a homeobox gene expressed in embryonic stem cells. We also report peripheral administrations of a pyrimidine derivative that increases endogenous stem cell proliferation improves cognitive function of the aged animal. Although these results may promise a bright future for clinical applications used towards stem cell strategies in AD therapy, we must acknowledge the complexity of AD. We found that glial differentiation takes place in stem cells transplanted into amyloid-( precursor protein (APP) transgenic mice. We also found that over expression of APP gene or recombinant APP treatment causes glial differentiation of stem cells. Although further detailed mechanistic studies may be required, RNA interference of APP or reduction of APP levels in the brain can significantly reduced glial differentiation of stem cells and may be useful in promoting neurogenesis after stem cell transplantation.     

Neurodegeneration and inflammation.

Recent studies have demonstrated a strong link between neurodegeneration and chronic inflammation. The central nervous system (CNS) has very limited regenerative capacity. Neural cell death occurs by apoptosis and necrosis. Necrosis in the CNS usually follows ischemic or traumatic brain injury. Apoptosis is known as programmed cell death and often demonstrates histologic features of acute and chronic neurologic diseases. The innate immune response is protective to the CNS to defend against pathogens. Temporary up-regulation of inflammatory events is natural and does not lead to cell death. If this inflammatory process is up-regulated, neurodegenerative changes may occur. There has been a proven link between the inflammatory response, increased cytokine formation, and neurodegeneration. Both pharmaceutic and nutrition interventions for treating chronic neurodegenerative diseases, such as Alzheimer's disease or multiple sclerosis, will be focused on reducing or terminating the chronic inflammatory response.     

Zinc and neurogenesis: making new neurons from development to adulthood

Stem cell proliferation, neuronal differentiation, cell survival, and migration in the central nervous system are all important steps in the normal process of neurogenesis. These mechanisms are highly active during gestational and early neonatal brain development. Additionally, in select regions of the brain, stem cells give rise to new neurons throughout the human lifespan. Recent work has revealed key roles for the essential trace element zinc in the control of both developmental and adult neurogenesis. Given the prevalence of zinc deficiency, these findings have implications for brain development, cognition, and the regulation of mood.     

Telomeres shorten with age in rat cerebellum and cortex in vivo

Normal somatic cells have a finite replicative capacity. With each cell division, telomeres, the ends of linear chromosomes, progressively shorten until they reach a critical length, at which point the cells enter replicative senescence. Some cells maintain their telomeres by the action of the telomerase enzyme. Glia, particularly microglia, are the only adult cell type in the central nervous system (CNS) that exhibit a significant mitotic potential, and are thus susceptible to telomere shortening. Previous research in our laboratory has found that telomeres shorten in rat microglia with increasing time in vitro. Our current hypothesis is that telomeres shorten in rat brain in vivo with increasing age. Tissue samples of cerebellum and cortex were obtained from Sprague-Dawley rats of various ages. Genomic DNA and total protein was isolated from each sample for telomere length measurement via Southern blot analysis (up to 5 months) and telomerase activity measurement via TRAP analysis (up to 6 months), respectively. Telomere shortening occurs in vivo in both rat cerebellum and cortex from day 21 to approximately 5 months of age. Cortex samples possessed shorter telomeres than did cerebellum samples. The longest telomeres undergo the most dramatic shortening, while the shortest telomeres exhibit only slight attrition. Telomerase activity slowly increases from day 21 to approximately 6 months of age, with the cerebellum exhibiting higher activity than cortex in all instances. These results indicate that telomere shortening occurs in rat brain in vivo with increasing age, and that the low levels of telomerase activity present may be preferentially recruited to maintain the shortest telomeres while allowing the longer ones to shorten more rapidly. Since microglia are thought to be the only mature cells of the postnatal CNS undergoing appreciable cell division, we propose that the telomere shortening occurring in the adult rat brain with age can be largely attributed to microglial cell division. Our findings provide an impetus to further investigate the pattern of telomere length and telomerase activity that emerges with further aging in the rat brain.     

Stem cell transplantation in the treatment of gastrointestinal diseases

The stem cells with self-renewal ability are capable to form one or more cell types. They will be in the target of cell and gene therapy because of their multipotency and easy retrieval. Application of adult mesenchymal, neuronal, epidermal and haematopoietic stem cell can be favourable in the treatment of cardiac (myocardial infarction), bone (osteoarthritis), neurological (Parkinson's, Alzheimer's) and hematological (hemophilia, thrombocytopenia) disorders. Authors summarize the knowledge in connection with their application in the therapy of gastrointestinal diseases. Haematopoietic stem cell transplantation has been successful for the treatment of refractory Crohn's disease, as well as in selected group of celiac patients. Mesenchymal stem cell transplantation has been proved beneficial in the prevention of liver fibrotic process. It will gain more grounds in the treatment of autoimmune liver diseases: autoimmune hepatitis, primary biliary cirrhosis and primary sclerosing cholangitis in the future. Well-designed, multicentric, prospective studies are needed to confirm the results of case reports and clinical studies with small group of patients.     

蛋白质糖基化修饰在儿童中枢神经系统疾病中的作用

蛋白质糖基化修饰是一种重要的翻译后修饰,对蛋白质的功能和结构形成具有重要作用,参与调控生物体的多项生命活动,如细胞粘附、转移、细胞间通讯、受体激活、信号转导等。近年来发现多种糖基化途径参与大脑发育的过程,异常的糖基化蛋白表达对大脑发育产生负面影响,并参与神经系统疾病的发生、发展。本文就蛋白质的糖基化修饰对神经功能的影响及糖基化异常导致的儿童中枢神经系统疾病进行论述,为儿童中枢神经系统疾病寻找新的糖基化蛋白诊断标志物和治疗靶点提供视角。     

Mesenchymal stem cell; history, biology and clinical application

In the last years, stem cells have drawn the attention of various sectors of society for many reasons. From the basic point of view, stem cells represent an ideal model to study cell differentiation and self-renewal mechanisms. However, their potential in cell therapy and regenerative medicine has triggered the increasing amount of knowledge in this area. Mesenchymal stem cells belong to the select group of adult stem cells. They have differentiation potential towards mesenchymal tissues such as bone, cartilage, stroma and fat. Recently, both in vivo and in vitro reports have shown a greater plasticity of mesenchymal stem cells, showing not only a mesenchymal cell fate but also those leading to endothelial, nervous and muscular lineages. For these reasons, the study of mesenchymal stem cells has gained great interest and many articles have been published. In the present review, we have presented a global vision of this topic, including its history, biologic features, sources, isolation methods and an overview on their clinical application.     

Endocrine links between food reward and caloric homeostasis

Both intrinsic and extrinsic (endocrine) inputs to the central nervous system (CNS) modulate motivation for feeding. Endocrine inputs such as insulin and leptin can have very rapid effects, but also the potential for chronic actions to decrease rewarding attributes of food. Future studies should elucidate the neural and cellular mechanisms which underlie these endocrine actions in the CNS.     

A European discussion about stem cells for therapeutic use

Stem cells as a source material for growing cellular transplants to repair dysfunctional organs appear to be a new challenge for medical science. Though stem cells are also present in foetal and adult organs, embryonic stem cells from the pre-implantation embryo in particular have the potency to proliferate easily in vitro and the capacity to differentiate into all the body's organ-specific cells. Therefore, these are the ideal cells for developing new cell transplantation therapies for diseases such as Parkinson's disease, diabetes mellitus and heart failure. The use of spare in vitro fertilization (IVF) embryos or pre-implantation embryos specially created to harvest human embryonic stem cells is, however, controversial and an ethical problem. In a European discussion platform organised by the European Commission Research Directorate-General, the status quo of the progress was presented and subsequently commented upon and discussed in terms of medical-ethical, social, industrial and patient interests. The expectations of this new medical technology were high, but clinical trials seem only acceptable once the in vitro differentiation of stem cells can be adequately controlled and once it is known how in vitro prepared stem cells behave after implantation. The ethical justification of the use of in vitro pre-implantation embryos remains controversial. The prevailing view is that the interests of severely ill patients for whom no adequate therapy exists, surmounts the interest of protection of a human in vitro pre-implantation embryo, regardless of whether it was the result of IVF or of transplantation of a somatic cell nucleus of the patient in an enucleated donor egg cell (therapeutic cloning).     

鼠IGF-1基因转染鼠神经干细胞的研究

目的：构建胰岛素样生长因子-1（IGF-1）基因修饰的神经干细胞（NSCs），用于神经系统疾病的治疗。方法：通过酶切和连接的方法构建IGF-1基因重组逆转录病毒载体pLXSN-IGF-1，转染包装细胞获得病毒液，测滴度后感染从胎龄14d的SD大鼠全脑中分离出的神经干细胞（NSCs），在转基因NSC中检测IGF-1基因的表达，观察转基因对NSCs增殖的影响。结果：酶切及序列分析证实逆转录病毒载体pLXSN-IGF-1构建正确，NSCs转基因后能检测到IGF-1基因表达，且仍然保持着未分化状态。能够自我更新以及具有多向分化潜能，并且生长速率加快。结论：成功构建了转IGF-1基因神经于细胞。     

In vitro models for the evaluation of the neurotoxicity of methylmercury. Current state of knowledge

BACKGROUND: In adults, MeHg poisoning is characterized by damage to discrete anatomical areas of the brain (visual cortex, loss of neurons from the granule layer of the cerebellum). However, the immature central nervous system (CNS), which is extremely sensitive to MeHg neurotoxicity, shows a diffuse and widespread damage disorganization of cerebral cortex cytoarchitecture, disappearance of granule cells with narrowing of the molecular layer. While adverse effects have been unequivocally demonstrated in poisoning incidents in humans (visual abnormalities, sensory impairment of the extremities, cerebellar ataxia, hearing loss, muscle weakness, tremor and mental deterioration), the implications of lower level exposures, such as those occurring in fish-eating populations, are still controversial. The high affinity of MeHg for thiol groups makes proteins and peptides bearing cysteines the predominant targets for structural and functional modification by MeHg in all subcellular compartments. METHODS: The identification of MeHg cellular and sub-cellular targets in the CNS is complicated by the fact that it is difficult to observe the outcomes directly in vivo. In neurobiology, in vitro cell culture techniques have been successfully developed and employed to address specific questions of cell biology and nervous system functioning and provide a means to systematically study the complexity of cellular functions of the CNS elements. Moreover, they provide a convenient experimental tool for testing possible functions or postulates in vivo that otherwise might not be conducted. RESULTS: Several mechanisms have been proposed as being implicated in the neurotoxic effects of MeHg. Examples of MeHg molecular effects which may be relevant to risk assessment are presented, including cell death mode, effects on microtubules, calcium signalling, oxidative stress, effects on neurotransmitter systems. CONCLUSIONS: Molecular and cellular approaches permit exploration of early biological responses to chemical or physical agents and definition of the role of these early effects in altered cellular structure and function.     

Nerve growth factor and multiple sclerosis: studies on animal models and in humans

We first reported that the level of nerve growth factor (NGF), a pleiotrophic factor produced in central nervous system (CNS) implicated in growth, differentiation and repair of brain neurones, undergoes through significant changes in brain of patients with multiple sclerosis (MS) and of its animal model experimental autoimmune encephalomyelitis (EAE). Recently, much attention has been evolved around these studies, reinforcing the hypothesis about the role of NGF in this disorder. Indeed, current studies indicate that NGF stimulates growth and differentiation of stem cell in EAE, exerts anti-inflammatory action and reduces the severity of EAE in non-human primate, prospecting the clinical potentiality of NGF for MS. However, despite these findings, crucial evidences, such as, the identification and characterisation of the mechanism(s) implicated in tissue repair and in inflammatory responses, needs to be done to evaluate the role of NGF to identify potential therapeutic strategies for this demyelinating disorder.     

不同程度的睡眠不足对大学生躯体感觉诱发电位、脑干听觉诱发电位和视觉诱发电位的影响

为研究睡眠不足对大学生中枢神经系统功能造成的影响,我们对不同程度睡眠不足大学生进行了上肢短潜伏时躯体感觉诱发电位、脑干听觉诱发电位和视觉诱发电位的测试。结果表明,上肢短潜伏时躯体感觉诱发电位无显著变化,脑干听觉诱发电位和视觉诱发电位各波潜伏时较对照组有延长趋势,彻夜不眠者显著延长(P<0.05)。从而提示这表明睡眠不足降低了中枢神经系统对内在和外在刺激的应激能力。