成体干细胞多能性研究进展

成体干细胞是存在于机体组织的一类原始状态细胞,它们能够进行自我复制和特异分化,用于维持新陈代谢和创伤修复,年珲来越来越多的实验表明成体干细胞多向分化潜能,一种组织的干细胞可以分化成其他组织类型的细胞。作者介绍了国际上对成体干细胞概念的新看法,讨论了成体干细胞多能性的调控机理及与之相关的研究方法,还简要概括了成体干细胞在理论和临床应用上的重要意义。     

神经干细胞分离培养方法的介绍

在成体的许多组织中发现了多能干细胞,这些干细胞可以进行自我复制,参与组织的正常修复。神经干细胞在体外能分化为神经元、星形胶质细胞和少突胶质细胞,并具有多向分化潜能。成体神经干细胞和胚胎干细胞都能分化成成体神经系统中的各种神经细胞。神经干细胞具有自我更新能力,因此神经干细胞可以应用于神经损伤或者神经疾病的修复。本文概述了神经干细胞体外分离培养的方法及其生长影响因子。     

成体干细胞的可塑性:横向分化还是细胞融合?

近年来研究显示成体干细胞(adult stem cells)具有可塑性(plasticity),不仅可以生成它们所在组织的成熟细胞,而且在特定环境下能分化成其他组织类型细胞,这种跨系或跨胚层分化现象称为横向分化或转分化(transdifferentiation)。横向分化已为成体干细胞的研究和临床应用包括组织器官损伤的修复提供了新的思路和应用前景。然而,最近的一些研究进展又引出不同的解释,即成体干细胞的可塑性是由于细胞融合(cellfusion)的结果。在此,就成体干细胞的可塑性、横向分化、细胞融合等方面研究作一综述。     

成体干细胞的研究及潜在应用

成体干细胞(adultstemcells)存在于人和哺乳动物的多种成体中,具有自我更新和一定的分化潜能.现已从骨髓、软骨、血液、神经、肌肉、脂肪、皮肤、角膜缘、肝脏、胰腺等许多组织中获得干细胞,并在部分成体干细胞的体外分离培养、扩增及诱导分化等研究中取得突破性进展,发现部分成体干细胞具有预想不到的分化潜能.成体干细胞不仅是发育生物学研究的理想模型,而且是细胞移植治疗、人工组织或器官构建的种子细胞和基因治疗的理想载体细胞,因此,在揭示生命的本质和规律及再生医学中有十分广阔的应用前景.     

成体干细胞在1型糖尿病中的应用研究及展望

成体干细胞存在于机体已分化的组织中,可在一定条件下分化为特定类型的细胞。成体干细胞来源广,移植后不存在免疫排斥反应,在1型糖尿病治疗领域有广阔的应用前景,可以作为受损伤或无功能的β细胞的替代细胞。该文主要概述了近年来成体干细胞在1型糖尿病中的应用研究及面临的问题。     

干细胞概述

干细胞是存在于胚胎和成体中的一类特殊细胞,它能长期地自我更新,在特定的条件下具有分化形成多种终末细胞的能力,不同来源的干细胞分化潜能各异。从早期胚胎内细胞团分离的胚胎干细胞能分化形成个体所有的细胞类型,并具有在体外无限增殖的能力,是最具有临床应用前景和研究价值的干细胞之一。在成体各种组织和器官中也存在成体干细胞,用于维持机体结构和功能的稳态。近期有关成体干细胞可塑性的研究和成体组织中多能干细胞存在的证据扩大了人们对成体干细胞分化潜能的认识。干细胞具有的多向分化潜能和自我更新能力使其成为未来再生医学的重要种子细胞,并成为研究人类早期胚层特化和器官形成、药物筛选以及基因治疗的最佳工具。     

成体干细胞可塑性的事实、质疑和展望

成体干细胞的可塑性是指存在于成年组织或器官中的不成熟细胞跨胚层分化的一种能力。近年来相关研究很多,有人认为成体干细胞具有可塑性,如造血干细胞可以分化为神经外胚层细胞和内胚层细胞：有人对其持怀疑态度,认为成年造血干细胞发育可塑性证据不足,成体干细胞不能跨胚层分化。由于分离纯化、检测手段等的局限,大多数研究均存在这样或那样的不足和误区,彻底研究清楚还有很长的路要走。     

组蛋白乙酰化对成体干细胞生物学性状的影响

成体干细胞（adult stem cells,ASCs）是指存在于一种已经分化组织中的未分化细胞,它们可以再生修复损伤的组织和器官,是组织工程和细胞治疗的理想细胞。但是ASCs在体外扩增过程中容易发生自主分化和衰老,影响其在临床的广泛应用。组蛋白乙酰化作为表观遗传调节的重要机制,参与细胞分化、衰老及凋亡等众多细胞活动的调控。该文就组蛋白乙酰化对成体干细胞生物学性状的影响进行综述。     

小鼠胚胎干细胞移植入成体大鼠脑内的区域特异性存活与分化

全能区域非特异性的胚胎干细胞是研究成体不同脑区控制干细胞分化能力的十分有力的工具。胚胎干细胞源性神经前体细胞移植入成体脑后可分化为功能性神经元,但是未分化的胚胎干细胞在成体脑内各个部位的存活、生长与分化的潜能差异尚不清楚。本文旨在探讨成体脑组织对胚胎干细胞的影响及胚胎干细胞在成体脑内的一系列行为。将少量转绿色荧光蛋白未分化的小鼠胚胎干细胞移植入成体大鼠脑内不同部位,分别于移植5、14和28d后处死大鼠,进行形态学观察及免疫组化定性,以了解未分化的小鼠胚胎干细胞在大鼠脑内不同区域的存活、生长与分化。结果发现未分化的小鼠胚胎干细胞可逐步整合入受体组织并向nestin阳性神经前体细胞分化。移植细胞及其后裔在海马生长最为旺盛,而在隔区最差（P〈0．01）;移植细胞分化为神经干细胞的效率也是在海马最高,而在隔区最低（P〈0．01）。提示只有部分脑区适合胚胎干细胞及其后裔生存,并提供促进其分化的有益环境。因此,由于位置特异的微环境因子及环境因素的存在,宿主组织特性对决定中枢神经系统疾病的细胞替代疗法策略是相当重要的。     

脂肪干细胞的研究进展

成体干细胞包括多能诱导干细胞、胚胎干细胞、脐带血干细胞、脂肪干细胞等,其中脂肪干细胞因其取材方便,无伦理限制,且能诱导成多胚层细胞而成为最有应用前景的成体干细胞之一。脂肪干细胞可以诱导分化为脂肪细胞、骨细胞、软骨细胞、肌细胞和神经元,在特定的条件下,可以构建皮肤,骨和软骨组织工程,是多种组织工程的理想种子细胞,有非常重要的研究和应用价值。本文综述了ADSC的分离培养、诱导分化,并着重对脂肪干细胞在组织工程临床应用方面的最新发展进行了阐述,以期为深入研究脂肪干细胞提供理论基础。     

Stem cell plasticity, cell fusion, and transdifferentiation

One of the most contentious issues in biology today concerns the existence of stem cell plasticity. The term "plasticity" refers to the capacity of tissue-derived stem cells to exhibit a phenotypic potential that extends beyond the differentiated cell phenotypes of their resident tissue. Although evidence of stem cell plasticity has been reported by multiple laboratories, other scientists have not found the data persuasive and have remained skeptical about these new findings. This review will provide an overview of the stem cell plasticity controversy. We will examine many of the major objections that have been made to challenge the stem cell plasticity data. This controversy will be placed in the context of the traditional view of stem cell potential and cell phenotypic diversification. What the implications of cell plasticity are, and how its existence may modulate our present understanding of stem cell biology, will be explored. In addition, we will examine a topic that is usually not included within a discussion of stem cell biology--the direct conversion of one differentiated cell type into another. We believe that these observations on the transdifferentiation of differentiated cells have direct bearing on the issue of stem cell plasticity, and may provide insights into how cell phenotypic diversification is realized in the adult and into the origin of cell phenotypes during evolution.     

Regenerating the epigenome

The ability of some organisms to regenerate parts of their body has fascinated scientists for decades. The process of regeneration depends on the potential of certain cells to proliferate and contribute to the formation of new tissue. Organisms have evolved two strategies by which to achieve this: the maintenance of adult stem cells and the induction of stem-cell properties in differentiated cells. In both cases, cells must undergo extensive epigenetic reprogramming to attain the specialized functions of the new tissue. Ultimately, the regenerative capacity of a tissue might depend on the plasticity of the cellular epigenome, which determines the ability of the cell to respond to injury-related signals. Understanding this epigenetic plasticity will allow the development of strategies to stimulate the regeneration of damaged tissues and organs in humans.     

BM stem cells and cardiac repair: where do we stand in 2004?

Adult BM stem cells are being investigated for their potential to regenerate injured tissues by a process referred to as plasticity or transdifferentiation. Although data supporting stem cell plasticity is extensive, a controversy has emerged based on findings that propose cell-cell fusion as a more appropriate interpretation for this phenomenon. A major focus of this controversy is the claim that acutely infarcted myocardium in adult hearts can be regenerated by BM stem cells. Many researchers consider the adult heart to be a post-mitotic organ, whereas others believe that a low level of cardiomyocyte renewal occurs throughout life. If renewal occurs, it may be in response to cardiac stem cell activity or to stem cells that migrate from distant tissues. Post-mortem microscopic analysis of experimentally induced myocardial infarctions in several rodent models suggests that cardiomyocyte renewal is achieved by stem cells that infiltrate the damaged tissue. For a better understanding of the possible involvement of stem cells in myocardial regeneration, it is important to develop appropriate technologies to monitor myocardial repair over time with an emphasis on large animal models. Studies on non-human primate, swine and canine models of acute myocardial infarctions would enable investigators to utilize clinical quality cell-delivery devices, track labeled donor cells after precision transplantation and utilize non-invasive imaging for functional assays over time with clinical accuracy. In addition, if stem cell plasticity is to reach the next level of acceptance, it is important to identify the environmental cues needed for stem cell trafficking and to define the genetic and cellular mechanisms that initiate transdifferentiation. Only then will it be possible to determine if, and to what extent, BM stem cells are involved in myocardial regeneration and to begin to regulate precisely tissue repair.     

Adult stem cell plasticity and methods of detection

The ability to selectively produce one or more differentiated cell types at will from totipotent stem cells would be of profound clinical importance, as it would enable the specific replacement of damaged/dysfunctional cell types within the body, potentially curing numerous diseases. Until recently, it was thought that the only cells that possessed sufficient immaturity to be capable of giving rise to more than one tissue type in vitro and in vivo were the embryonic stem cells. However, recent studies have now provided compelling evidence that the adult bone marrow, brain and skeletal muscle contain stem cells that possess the remarkable ability to trans-differentiate and give rise to progeny of alternate embryologic derivations. These recent findings have shattered the existing dogma that the stages of embryologic development are irreversible. In this review, we present a brief summary of the most significant findings in the field of stem cell plasticity, emphasizing studies involving the hematopoietic system, discussing the models used thus far, and finishing with our findings on human stem cell plasticity using the fetal sheep model.     

Stem cells and regenerative medicine

Stem cells have been defined as clonogenic cells that undergo both self-renewal and differentiation to more committed progenitors and functionally specialized mature cells. Of late years, stem cells have been identified in a variety of tissues of an adult body. Depending on the source, they have the potential to form one or more, or even all cell types of an organism. Stem cell research provided some outstanding contributions to our understanding of developmental biology and offered much hope for cell replacement therapies overcoming a variety of diseases. The establishment of human ES cell lines enabled us to generate all tissues we comprise. Recently, excitement has been evoked by the controversial evidence that adult stem cells have a much higher degree of developmental plasticity than previously imagined. More recently, the existence of multipotent somatic stem cells in bone marrow has been reported. Combined with these discoveries and achievements as well as the developing technologies, scientists are now trying to bring stem cell therapies to the clinic.     

干细胞生物工程研究展望

 由于最近两年干细胞研究技术的突破 ,一门崭新的学科“干细胞生物工程”已经形成 .人类胚胎干细胞在体外的成功培养以及一种组织的干细胞 (成体干细胞 )向另一种组织细胞横向分化的发现 ,为利用“干细胞生物工程”技术治疗疾病奠定了基础 .本综述着重介绍干细胞研究领域的一些新概念和新技术以及干细胞分化的基因调控 .对干细胞生物工程的临床应用前景作了概括性讨论     

The neural stem cell niche

The neural stem cell niche defines a zone in which stem cells are retained after embryonic development for the production of new cells of the nervous system. This continual supply of new neurons and glia then provides the postnatal and adult brain with an added capacity for cellular plasticity, albeit one that is restricted to a few specific zones within the brain. Critical to the maintenance of the stem cell niche are microenvironmental cues and cell-cell interactions that act to balance stem cell quiescence with proliferation and to direct neurogenesis versus gliogenesis lineage decisions. Ultimately, based on the location of the niche, stem cells of the adult brain support regeneration in the dentate gyrus of the hippocampus and the olfactory bulb through neuron replacement. Here, we provide a summary of the current understanding of the organization and control mechanisms of the neural stem cell niche.