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.     

Somatische Stammzellen des zentralen Nervensystems

During neural development, the nervous system is created from stem cells that have the potential to proliferate, to reproduce (self-renew) themselves, and to differentiate into the appropriate neuronal and glial phenotypes. Although the adult brain has traditionally been thought of as a structure with very limited regenerative capacity, these neural stem cells have recently been shown to exist in the adult central nervous system (CNS) as well. In vitro and following transplantation, neural stem cells obtained from the fetal and adult brain are able to generate neurons, astrocytes, and oligodendrocytes, the three major CNS cell types. Therefore, neural stem cells are potential sources for specialized neural cells needed to treat a variety of neurological disorder. The present review describes how somatic stem cells of the central nervous system can be cultivated in vitro and to which extend stem cell transplantation is effective in animal models for neurological diseases. Finally, a perspective is given on the potential clinical use of human neural stem cells for the treatment of neurological diseases.     

Spermatogonia: origin, physiology and prospects for conservation and manipulation of the male germ line

In recent years, the scientific community has become increasingly interested in spermatogonia. Methodological breakthroughs, such as germ cell transplantation and spermatogonial culture combined with novel germ line transfection strategies, have provided interesting new opportunities for studying the physiology of spermatogonial stem cells and their interaction with the stem cell niche. Furthermore, intense research into pluripotent and adult stem cells has generated new insight into the differentiation pathway of germ line stem cells and has opened new perspectives for stem cell technologies. The present review briefly introduces the physiology of spermatogonial stem cells and discusses future directions of basic research and practical approaches applicable to livestock maintenance and animal reproduction.     

Derivation characteristics and perspectives for mammalian pluripotential stem cells

Pluripotential stem cells have been derived in mice and primates from preimplantation embryos, postimplantation embryos and bone marrow stroma. Embryonic stem cells established from the inner cell mass of the mouse and human blastocyst can be maintained in an undifferentiated state for a long time by continuous passage on embryonic fibroblasts or in the presence of specific inhibitors of differentiation. Pluripotential stem cells can be induced to differentiate into all the tissues of the body and are able to colonise tissues of interest after transplantation. In mouse models of disease, there are numerous examples of improved tissue function and correction of pathological phenotype. Embryonic stem cells can be derived by nuclear transfer to establish genome-specific cell lines and, in mice, it has been shown that embryonic stem cells are more successfully reprogrammed for development by nuclear transfer than somatic cells. Pluripotential stem cells are a very valuable research resource for the analysis of differentiation pathways, functional genomics, tissue engineering and drug screening. Clinical applications may include both cell therapy and gene therapy for a wide range of tissue injury and degeneration. There is considerable interest in the development of pluripotential stem cell lines in many mammalian species for similar research interests and applications.     

肝细胞移植治疗肝衰竭的研究进展

近年来许多研究证明肝细胞移植对急慢性肝衰竭有明显的治疗作用,是急慢性肝衰竭患者等待肝源、向原位肝移植过渡的有效方法。此文就肝细胞移植治疗肝衰竭的机制、肝细胞源、移植方式及实验和临床研究等方面的进展作了综述。     

Embryonic stem cell therapy in experimental stroke: host-dependent malignant transformation

INTRODUCTION: Therapeutic application of embryonic stem cells in neurodegenerative disorders like stroke is widely investigated in preclinical animal models. AIM: The authors studied the therapeutic potential of murine embryonic stem cells in two rodent models of stroke. METHODS: Undifferentiated and predifferentiated stem cells were implanted into the non-ischemic hemisphere of mice and rats following focal brain ischemia. The brains were analysed by immunohistochemistry and histology. The in vitro differentiation of the cells was checked by immunocytochemistry and Western-blot. RESULTS: After xenotransplantation in rats undifferentiated cells migrated along the corpus callosum towards the ischemic injury. Later stem cells differentiated into neurons in the border zone of the lesion. In the homologous mouse brain, the same murine embryonic stem cells did not migrate, but produced highly malignant teratocarcinomas at the site of implantation, independent of whether they were predifferentiated in vitro to neural progenitor cells. These experiments demonstrated a hitherto unrecognized adverse outcome after xenotransplantation and homologous transplantation of embryonic stem cells. CONCLUSION: This observation raises serious concerns about safety provisions when the therapeutic potential of human embryonic stem cells is tested in preclinical animal models. The clinical trials are based on the positive outcome of the xenologous experiments.     

干细胞治疗子宫内膜损伤的研究进展

感染因素或宫腔手术操作导致的子宫内膜损伤阻碍胚胎的着床和发育,严重影响妇女的身心健康与生育能力。但目前治疗手段有限且效果欠佳。干细胞具有自我更新和分化潜能,在病变损伤组织的修复过程中发挥重要作用。骨髓间充质干细胞、脐带间充质干细胞、子宫内膜干细胞、脂肪干细胞和人羊膜上皮细胞等多种干细胞治疗子宫内膜损伤已在动物模型和临床研究中开展,并展现出巨大的潜力。干细胞治疗可促进子宫内膜细胞再生,改善子宫内膜厚度和微血管密度,提高受孕率并改善生育结局。干细胞治疗从形态和功能上改善子宫内膜,促进月经和生殖功能的恢复,为治疗子宫内膜损伤提供一种新策略。     

Embryonic stem cells in companion animals (horses, dogs and cats): present status and future prospects

Reproductive technologies have made impressive advances since the 1950s owing to the development of new and innovative technologies. Most of these advances were driven largely by commercial opportunities and the potential improvement of farm livestock production and human health. Companion animals live long and healthy lives and the greatest expense for pet owners are services related to veterinary care and healthcare products. The recent development of embryonic stem cell and nuclear transfer technology in primates and mice has enabled the production of individual specific embryonic stem cell lines in a number of species for potential cell-replacement therapy. Stem cell technology is a fast-developing area in companion animals because many of the diseases and musculoskeletal injuries of cats, dogs and horses are similar to those in humans. Nuclear transfer-derived stem cells may also be selected and directed into differentiation pathways leading to the production of specific cell types, tissues and, eventually, even organs for research and transplantaton. Furthermore, investigations into the treatment of inherited or acquired pathologies have been performed mainly in mice. However, mouse models do not always faithfully represent the human disease. Naturally occurring diseases in companion animals can be more ideal as disease models of human genetic and acquired diseases and could help to define the potential therapeutic efficiency and safety of stem cell therapies. In the present review, we focus on the economic implications of companion animals in society, as well as recent biotechnological progress that has been made in horse, dog and cat embryonic stem cell derivation.     

Germ cell transplantation for the propagation of companion animals, non-domestic and endangered species

The transplantation of spermatogonial stem cells between males results in a recipient animal producing spermatozoa carrying a donor's haplotype. First pioneered in rodents, this technique has now been used in several animal species. Importantly, germ cell transplantation was successful between unrelated, immuno-competent large animals, whereas efficient donor-derived spermatogenesis in rodents requires syngeneic or immuno-compromised recipients. Transplantation requires four steps: recipient preparation, donor cell isolation, transplantation and identifying donor-derived spermatozoa. There are two main applications for this technology. First, genetic manipulation of isolated germ line stem cells and subsequent transplantation will result in production of transgenic spermatozoa. Transgenesis through the male germ line has tremendous potential in species in which embryonic stem cells are not available and somatic cell nuclear transfer and reprogramming pose several problems. Second, spermatogonial stem cell transplantation within or between species offers a means of preserving the reproductive potential of genetically valuable individuals. This might have significance in the captive propagation of non-domestic animals of high conservation value. Transplantation of germ cells is a uniquely valuable approach for the study, preservation and manipulation of male fertility in mammalian species.     

间充质干细胞移植治疗肝衰竭研究进展

肝衰竭病死率高,其治疗始终是棘手的问题.近年来,干细胞移植作为一种治疗肝衰竭的有效方法得到越来越广泛的应用.间充质干细胞(MSC)是一种具有自我更新和多向分化潜能的干细胞,且体外易于扩增,因此是细胞治疗较为理想的选择.MSC的许多生物特性为临床治疗肝衰竭提供了新策略.此文就MSC表面标志及移植尝试等方面的进展进行综述.     

间充质干细胞移植治疗肝衰竭研究进展

肝衰竭病死率高,其治疗始终是棘手的问题.近年来,干细胞移植作为一种治疗肝衰竭的有效方法得到越来越广泛的应用.间充质干细胞(MSC)是一种具有自我更新和多向分化潜能的干细胞,且体外易于扩增,因此是细胞治疗较为理想的选择.MSC的许多生物特性为临床治疗肝衰竭提供了新策略.此文就MSC表面标志及移植尝试等方面的进展进行综述.     

间充质干细胞移植治疗肝衰竭研究进展

肝衰竭病死率高,其治疗始终是棘手的问题.近年来,干细胞移植作为一种治疗肝衰竭的有效方法得到越来越广泛的应用.间充质干细胞(MSC)是一种具有自我更新和多向分化潜能的干细胞,且体外易于扩增,因此是细胞治疗较为理想的选择.MSC的许多生物特性为临床治疗肝衰竭提供了新策略.此文就MSC表面标志及移植尝试等方面的进展进行综述.     

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。     

Male germ cell transplantation in livestock

Male germ cell transplantation is a powerful approach to study the control of spermatogenesis with the ultimate goal to enhance or suppress male fertility. In livestock animals, applications can be expanded to provide an alternative method of transgenesis and an alternative means of artificial insemination (AI). The transplantation technique uses testis stem cells, harvested from the donor animal. These donor stem cells are injected into seminiferous tubules, migrate from the lumen to relocate to the basement membrane and, amazingly, they can retain the capability to produce donor sperm in their new host. Adaptation of the mouse technique for livestock is progressing, with gradual gains in efficiency. Germ cell transfer in goats has produced offspring, but not yet in cattle and pigs. In goats and pigs, the applications of germ cell transplantation are mainly in facilitating transgenic animal production. In cattle, successful male germ cell transfer could create an alternative to AI in areas where it is impractical. Large-scale culture of testis stem cells would enhance the use of elite bulls by providing a renewable source of stem cells for transfer. Although still in a developmental state, germ cell transplantation is an emerging technology with the potential to create new opportunities in livestock production.     

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).     

Viral vectors for malaria vaccine development

A workshop on viral vectors for malaria vaccine development, organized by the PATH Malaria Vaccine Initiative, was held in Bethesda, MD on October 20, 2005. Recent advancements in viral-vectored malaria vaccine development and emerging vector technologies were presented and discussed. Classic viral vectors such as poxvirus, adenovirus and alphavirus vectors have been successfully used to deliver malaria antigens. Some of the vaccine candidates have demonstrated their potential in inducing malaria-specific immunity in animal models and human trials. In addition, emerging viral-vector technologies, such as measles virus (MV), vesicular stomatitis virus (VSV) and yellow fever (YF) virus, may also be useful for malaria vaccine development. Studies in animal models suggest that each viral vector is unique in its ability to induce humoral and/or cellular immune responses. Those studies have also revealed that optimization of Plasmodium genes for mammalian expression is an important aspect of vaccine design. Codon-optimization, surface-trafficking, de-glycosylation and removal of toxic domains can lead to improved immunogenicity. Understanding the vector's ability to induce an immune response and the expression of malaria antigens in mammalian cells will be critical in designing the next generation of viral-vectored malaria vaccines.     

Allogeneic stem cell transplantation. An economic comparison of bone marrow, peripheral blood, and cord blood technologies

OBJECTIVES: To compare outcome attributes of three available technologies for stem cell transplantation--bone marrow transplantation (BM), peripheral blood cell transplantation (PB), and cord blood transplantation (CB). To compare the cost per recipient for the three technologies, incorporating all donor and antigen matching functions, as well as the transplantation procedures. METHODS: Review of relevant literature using the CancerLit and HealthSTAR databases (plus earlier searches of MEDLINE and Embase) to summarize outcome differences. Estimations of cost per transplant using models drawing on Canadian experience. RESULTS: The literature review indicated that PB may have a modest advantage over BM in terms of outcomes. The literature indicated that CB has longer engraftment times (although this may be due to inadequate controls). Our modeling exercise indicated that costs for PB and BM are similar. CB has a higher cost per recipient, due in large part to the higher testing costs for every donated unit. CONCLUSIONS: Current literature is inadequate to provide an outcomes comparison of CB, PB, and BM. Viewed from a system-wide perspective, CB is a higher cost technique. However, PB and CB are emerging as technologies, and so our results should be viewed alongside the notion that there may be a steep learning curve in these technologies.     

Stem cell therapy for diabetes mellitus: progress, prospects and challenges

Curative therapy for diabetes mellitus mainly implies replacement of missing insulin-producing pancreatic beta cells, with pancreas or islet-cell transplants. The limited supply currently available from cadaveric donor islets for transplantation, however, determines that researchers must explore alternative sources of graft material. Stem cells represent a promising solution to this problem, and current research is being aimed at the creation of islet-endocrine tissue from these undifferentiated cells. Both embryonic stem cells (derived from the inner cell mass of a blastocyst) and adult tissue stem cells (found in the postnatal organism) have been used to generate surrogate beta cells or otherwise restore beta cell functioning. Nevertheless, cell replacement therapies that are stem cell based will remain fiction rather than fact until we can efficiently and reproducibly ensure that stable, fully functional cells can be generated in vitro. It is also critical to ensure that any surrogate or regenerated beta cells have perfectly regulated insulin production, which is essential for physiological glucose homeostasis. As in every emerging field in biology, early reports seem confusing and conflicting. Therefore, discrepancies between different results need to be reconciled. In addition, encouraging studies in rodent models may ultimately set the stage for large-animal studies. In this review, the authors provide insight into research efforts to overcome existing hurdles for this promising therapy.     

人卵巢癌荷瘤裸鼠两种皮下移植瘤模型的构建及生长特性的比较

目的:构建人卵巢上皮癌裸鼠皮下移植瘤动物模型,并对实体瘤组织块移植及细胞悬液移植的肿瘤模型及其生长特性进行了一系列比较研究,以期为研究卵巢癌的发病机制及靶向治疗措施确定体内实验的最佳模型,并提供充分的理论依据。方法:随机选择10只6～8周龄的裸鼠,分为实体瘤组织块移植组和细胞悬液移植组,每组各5只。通过显微外科手术将瘤体小块接种到裸鼠腋下皮肤,将另一部分瘤体碾碎制成细胞悬液,将1×107个/ml的细胞悬液0.2 ml裸鼠腋下皮肤内注射。动态追踪两组肿瘤模型的生长情况及体内肿瘤的转移情况,处死荷瘤鼠取出肿瘤组织后做病理学检查。结果:全部裸鼠均皮下成瘤,成功率为100%。组织块接种的裸鼠肿瘤生长速度比细胞接种的裸鼠明显快,接种21天后处死裸鼠,组织块接种组比细胞接种组明显增大,两组肿瘤平均体积差异有统计学意义(P<0.05)。通过尸检发现所有裸鼠均未出现淋巴及其他器官的转移,病理学检查提示两组裸鼠移植瘤都具有人卵巢癌组织学特征。结论:构建了人卵巢癌裸鼠皮下移植瘤模型,两种方法建立的动物模型均可用于从整体水平对卵巢癌进行相关研究,是理想的卵巢癌动物模型。人卵巢癌组织块接种法构建的动物模型更适合用于周期较短的实验研究。     

骨髓间充质干细胞移植对Tourette综合征大鼠纹状体脑源性神经营养因子表达的影响

目的 考察骨髓间充质干细胞(MSC)移植对Tourette综合征(TS)大鼠纹状体内脑源性神经营养因子(BDNF)表达的影响,探讨MSC移植治疗TS的作用机制。方法 采用立体定向技术向大鼠纹状体内微量灌注抗基底神经节抗体(ABGA),制备自身免疫TS动物模型;采用密度梯度离心法在体外分离、培养和扩增大鼠MSC,经流式细胞仪鉴定后将MSC标记并移植到TS大鼠纹状体内。通过ELISA及RT-PCR技术检测大鼠脑内BDNF水平。结果 将MSC移植到TS大鼠纹状体内,自移植后7 d开始观察到TS大鼠的刻板行为减少。TS大鼠纹状体内BDNF水平升高(P<0.05);MSC移植后TS大鼠纹状体内BDNF含量下降。结论 MSC移植能减少TS大鼠的刻板行为、降低TS大鼠体内的BDNF含量。