Current Challenges for the Advancement of Neural Stem Cell Biology and Transplantation Research

Transplantation of neural stem cells (NSC) is hoped to become a promising primary or secondary therapy for the treatment of various neurodegenerative disorders of the central nervous system (CNS), as demonstrated by multiple pre-clinical animal studies in which functional recovery has already been demonstrated. However, for NSC therapy to be successful, the first challenge will be to define a transplantable cell population. In the first part of this review, we will briefly discuss the main features of ex vivo culture and characterisation of NSC. Next, NSC grafting itself may not only result in the regeneration of lost tissue, but more importantly has the potential to improve functional outcome through many bystander mechanisms. In the second part of this review, we will briefly discuss several pre-clinical studies that contributed to a better understanding of the therapeutic potential of NSC grafts in vivo. However, while many pre-clinical animal studies mainly report on the clinical benefit of NSC grafting, little is known about the actual in vivo fate of grafted NSC. Therefore, the third part of this review will focus on non-invasive imaging techniques for monitoring cellular grafts in the brain under in vivo conditions. Finally, as NSC transplantation research has evolved during the past decade, it has become clear that the host micro-environment itself, either in healthy or injured condition, is an important player in defining success of NSC grafting. The final part of this review will focus on the host environmental influence on survival, migration and differentiation of grafted NSC.     

干细胞移植与神经修复

背景：随着生命科学发展,利用干细胞来源的组织工程技术,有可能使受损的神经组织恢复再生能力。 目的：针对较为重要的几种干细胞在神经系统修复中的临床应用做一综述,以期阐明各自适用范围和临床效度,为临床医师按需选择提供参考。 方法：应用计算机检索PubMed 数据库中1998至2011年期间的关于干细胞移植在神经修复方面研究的文章,检索词为“Stem cells, Transplantation, Nerve repair”,限定语种为“English”。同时,检索万方数据库中2006至2011年期间的相关文章,检索词为“干细胞,移植,神经修复”,限定语种为中文。 结果与结论：初次检索得到288篇文章,选择与移植干细胞的来源、分化、特征及其在神经修复方面相关的文章,包括基础研究和临床研究,观察对象无论为人或动物,均进行审校。根据纳入标准,在排除重复和个案报道类文章之后,重点选择32篇文章进行综述。说明干细胞移植为神经系统疾病的治疗提供了一条新途径,使传统认为的不可修复、不可再生的神经组织的结构修复和功能重建成为可能。干细胞移植是一个全新的领域,还有许多问题亟待解决。     

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.     

Enumeration of neural stem and progenitor cells in the neural colony-forming cell assay

Advancement in our understanding of the biology of adult stem cells and their therapeutic potential relies heavily on meaningful functional assays that can identify and measure stem cell activity in vivo and in vitro. In the mammalian nervous system, neural stem cells (NSCs) are often studied using a culture system referred to as the neurosphere assay. We previously challenged a central tenet of this assay, that all neurospheres are derived from a NSC, and provided evidence that it overestimates NSC frequency, rendering it inappropriate for quantitation of NSC frequency in relation to NSC regulation. Here we report the development and validation of the neural colony-forming cell assay (NCFCA), which discriminates stem from progenitor cells on the basis of their proliferative potential. We anticipate that the NCFCA will provide additional clarity in discerning the regulation of NSCs, thereby facilitating further advances in the promising application of NSCs for therapeutic use.     

Stem cells in nephrology: present status and future

Stem cell biology is currently developing rapidly because of the potential therapeutic utility of stem cells. The ability to acquire any desired phenotype raises hope for regenerative therapies. Manipulation of these cells is a potentially valuable tool; however, the mechanisms of stem cell differentiation and plasticity are currently beyond our control. In the field of nephrology, the presence of adult kidney stem cells has been debated. Renal adult stem cells may be descendants of some early kidney progenitors, or may be derived from bone marrow. Evidence of a hematopoietic stem-cell contribution to renal repair encourages the possibility of bone marrow or stem cell transplantation as a means of treating autoimmune glomerulopathies. The transplantation of fetal kidney tissue containing renal progenitors, which then develop into functional nephrons, is a step towards renal regeneration. According to recent reports, the development of functional nephrons from human mesenchymal stem cells in rodent whole-embryo culture is possible. Establishing in vitro self organs from autologous stem cells would be a promising therapeutic solution in light of the shortage of allogenic organs and the unresolved problem of chronic allograft rejection.     

中枢神经系统干细胞研究进展

近年来，中枢神经系统干细胞的研究方法和其在临床应用方面的价值日益成为神经干细胞研究的焦点，本文对于神经干细胞的发现，最新的神经干细胞研究技术以及神经干细胞在中枢神经系统退变性疾病，缺血损伤和肿瘤治疗等方面的研究进展作一概述。     

Promoting remyelination through cell transplantation therapies in a model of viral-induced neurodegenerative disease

Multiple sclerosis (MS) is a central nervous system (CNS) disease characterized by chronic neuroinflammation, demyelination, and axonal damage. Infiltration of activated lymphocytes and myeloid cells are thought to be primarily responsible for white matter damage and axonopathy. Several United States Food and Drug Administration-approved therapies exist that impede activated lymphocytes from entering the CNS thereby limiting new lesion formation in patients with relapse-remitting forms of MS. However, a significant challenge within the field of MS research is to develop effective and sustained therapies that allow for axonal protection and remyelination. In recent years, there has been increasing evidence that some kinds of stem cells and their derivatives seem to be able to mute neuroinflammation as well as promote remyelination and axonal integrity. Intracranial infection of mice with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in immune-mediated demyelination and axonopathy, making this an excellent model to interrogate the therapeutic potential of stem cell derivatives in evoking remyelination. This review provides a succinct overview of our recent findings using intraspinal injection of mouse CNS neural progenitor cells and human neural precursors into JHMV-infected mice. JHMV-infected mice receiving these cells display extensive remyelination associated with axonal sparing. In addition, we discuss possible mechanisms associated with sustained clinical recovery. Developmental Dynamics 248:43–52, 2019. © 2018 Wiley Periodicals, Inc.     

Biology of the adult enteric neural stem cell.

An increasing body of evidence has accumulated in recent years supporting the existence of neural stem cells in the adult gut. There are at least three groups that have obtained them using different methodologies and have described them in vitro. There is a growing amount of knowledge on their biology, but many questions are yet unanswered. Among these questions is whether these cells are part of a permanent undifferentiated pool or are recruited in a regular basis; in addition, the factors and genes involved in their survival, proliferation, migration, and differentiation are largely unknown. Finally, with between 10 and 20% of adults suffering from diseases involving the enteric nervous system, most notably irritable bowel syndrome and gastroesophageal reflux, what is the possible role of enteric nervous stem cells in health and disease? Developmental Dynamics 236:20–32, 2007. © 2006 Wiley‐Liss, Inc.     

Large-scale expansion of mammalian neural stem cells: a review

A relatively new approach to the treatment of neurodegenerative diseases is the direct use of neural stem cells (NSCs) as therapeutic agents. The expected demand for treatment from the millions of afflicted individuals, coupled with the expected demand from biotechnology companies creating therapies, has fuelled the need to develop large-scale culture methods for these cells. The rapid pace of discovery in this area has been assisted through the use of animal model systems, enabling many experiments to be performed quickly and effectively. This review focuses on recent developments in expanding human and murine NSCs on a large scale, including the development of new serum-free media and bioreactor protocols. In particular, engineering studies that characterise important scale-up parameters are examined, including studies examining the effects of long-term culture of NSCs in suspension bioreactors. In addition, recent advances in the human NSC system are reviewed, including techniques for the evaluation of NSC characteristics.     

Bone marrow-derived stem cell therapy in ischemic heart disease

Since the first experiments of cell transplantation into the heart were performed in the early 1990s, the identification of adult stem cells has triggered attempts to regenerate damaged heart tissue by cellular transplantation. Until recently, a multitude of adult stem or progenitor cells from various tissues have been proposed to meet this end. Bone marrow in particular has emerged as the most promising source for stem and progenitor cells because, besides being the organ of hematopoietic maintenance, it contains a complex assortment of stem and progenitor cells. A large body of provocative experimental evidence for vascular and myocardial regeneration by these cells has generated further enthusiasm for their use. However, many questions remain unanswered in this new field of research regarding the therapeutic potential and the mechanisms responsible for the observed therapeutic effects. In this review, the authors discuss the therapeutic capacity of currently available representative bone marrow-derived stem and progenitor cells for treating ischemic heart diseases.     

Kidney regeneration by xeno-embryonic nephrogenesis

Establishment of a functional whole kidney de novo has not received much attention because of the formidable challenges and the slow pace of advances in this field of research. This situation has changed recently with publication of data revealing the catastrophic nature of Medicaid costs for dialysis-related diseases. An innovative approach is needed in our search for therapies for kidney diseases and to provide a substitute for dialysis as soon as possible. Regenerative medicine offers great hope for realizing this goal. We established a system by which human mesenchymal stem cells can differentiate into a functional renal unit using a program of nephrogenesis in a developing xeno-embryo. In this article, recent research in the field of developing whole kidneys is reviewed, and possible therapeutic applications for kidney diseases are proposed in combination with our knowledge of the emerging field of kidney stem cell biology.     

神经干细胞移植治疗大鼠局灶性脑缺血损伤

背景：近年来,神经干细胞移植已成为治疗神经退行性疾病和中枢神经系统损伤的研究热点。 目的：探讨神经干细的定向分化调控机制和神经干细胞移植治疗大鼠局灶性脑缺血损伤的研究进展。 方法：以“neural stem cells, stem cell transplantation, ischemic brain injury”为检索词,检索Pubmed数据库1990至2012年相关文献;以“神经干细胞,干细胞移植,缺血性脑损伤”为检索词,检索CNKI数据库2005至2012 年相关文献。分析神经干细的定向分化调控机制和神经干细胞移植治疗大鼠局灶性脑缺血损伤的内容,排除重复研究。 结果与结论：①体外分离培养的神经干细胞有胚胎来源、脐血来源和成体来源,主要采用机械分离法和胰酶消化法进行分离。②目前体外培养的神经干细胞分离鉴定的标记物有巢蛋白、波形蛋白1、5-溴脱氧尿嘧啶核苷、神经元特异性烯醇化酶等。③神经干细胞的分化调节是通过正负双重作用实现的,负性调节是通过对称性的分裂来增加神经干细胞数量,包括Notch信号途径和一些生长因子等。正性调节诱导神经干细胞分化,包括参与细胞合成的骨形态发生蛋白信号途径等。④神经干细胞移植的时间窗选择在实验动物脑缺血两三周后,时间过早和过晚均不适合细胞的存活。神经干细胞通过脑立体定位仪直接进行脑内移植治疗大鼠局灶性脑缺血损伤,移植后可见细胞在局灶性脑缺血大鼠脑室内和梗死中心均可长期存活,并可广泛迁移,移植神经干细胞后观察到其运动行为学评分有明显提高。缺血性脑卒中的神经干细胞移植治疗还存在一些问题需要解决,未来的临床应用前景广阔,是缺血性脑卒中患者的新希望。     

干细胞移植在心血管疾病应用中急待解决的问题

背景：干细胞作为细胞移植的种子细胞治疗心血管疾病已成为近年来研究的热点,许多动物实验及临床研究均表明干细胞移植是提高心功能新的治疗措施。 目的：针对干细胞在心血管疾病应用中的移植种类选择、移植途径、移植时机及其安全性问题进行综述。 方法：由第一作者应用计算机检索2000/2010 PubMed数据库及中国期刊全文数据库中有关干细胞移植在心血管疾病中应用的文章,英文检索词为“stem cell transplantion,cardiovascular disease”,中文检索词为“干细胞移植,心血管疾病”。排除重复性研究及无关研究,共保留25篇文章进行综述。 结果与结论：干细胞移植可以改善缺血心肌的灌注,减少心肌细胞死亡,限制左室重构,从而从根本上改善患者的心功能,降低死亡率。但干细胞移植治疗心血管疾病的研究目前还处于初级阶段,尚有许多问题急待解决。     

Stem Cell Therapy for Bronchopulmonary Dysplasia: Bench to Bedside Translation

Bronchopulmonary dysplasia (BPD), a chronic lung disease affecting very premature infants, is a major cause of mortality and long-term morbidities despite of current progress in neonatal intensive care medicine. Though there has not been any effective treatment or preventive strategy for BPD, recent stem cell research seems to support the assumption that stem cell therapy could be a promising and novel therapeutic modality for attenuating BPD severity. This review summarizes the recent advances in stem cell research for treating BPD. In particular, we focused on the preclinical data about stem cell transplantation to improve the lung injury using animal models of neonatal BPD. These translational research provided the data related with the safety issue, optimal type of stem cells, optimal timing, route, and dose of cell transplantation, and potency marker of cells as a therapeutic agent. Those are essential subjects for the approval and clinical translation. In addition, the successful phase I clinical trial results of stem cell therapies for BPD are also discussed.     

Stem cell therapy for neurodegenerative diseases: the issue of transdifferentiation

In the past few years research on stem cells has exploded as a tool to develop potential therapies to treat incurable neurodegenerative diseases. Stem cell transplantation has been effective in several animal models, but the underlying restorative mechanisms are still unknown. Several events such as cell fusion, neurotrophic factor release, endogenous stem cell proliferation, and transdifferentiation (adult cell acquisition of new unexpected identities) may explain therapeutic success, in addition to replacement of lost cells. This issue needs to be clarified further to maximize the potential for effective therapies. Preliminary stem transplantation trials have already been performed for some neurodegenerative diseases. There is no effective pharmacological treatment for amyotrophic lateral sclerosis, but recent preliminary data both in experimental and clinical settings have targeted it as an ideal candidate disease for the development of stem cell therapy in humans. This review summarizes recent advances gained in stem cell research applied to neurodegenerative diseases with a special emphasis to the criticisms put forward.     

Sex, the underestimated potential determining factor in brain tissue repair strategy

Neural stem cells (NSCs) hold a lot of potential for the development of brain repair strategies. However, difficulties in clinical translation suggest that improving the "know how" demands that we improve our fundamental knowledge on mechanisms that regulate NSC transplantation outcome. In this article, we will focus on recent works conducted in our laboratory and by others supporting the fact that the sex of NSCs (the donor) may be a determining factor in the outcome of NSCs grafts. In particular, we will discuss the intrinsic sexual dimorphism recently reported in NSCs showing a differential expression of estrogen receptor alpha and beta as well as aromatase and how it affected NSCs transplantation outcome. An emphasis will be put on the importance of taking such sexual dimorphism into consideration for the design of future brain repair strategies.     

VEGF转基因神经干细胞移植对大鼠急性放射性脑损伤后脑组织中NSE表达的影响

目的： 探讨血管内皮生长因子（VEGF）转染的神经干细胞(NSC)对放射性脑损伤的影响。方法：将Sprague-Dawley(SD)大鼠随机分为对照组、放射性脑损伤组、NSC和转染VEGF的NSC治疗组, 放射性脑病模型成功制备后1周脑内移植转染VEGF的NSC,移植后1周、2周、3周、4周和6周末取其脑组织,用免疫组织化学法测定神经元特异性烯醇化酶(NSE)阳性细胞数,Western blotting法检测NSE蛋白表达情况。结果：与对照组相比, 放射性脑损伤组大鼠脑组织中NSE阳性细胞数显著下降(P<0.05);与放射性脑损伤组相比,NSC治疗组和转染VEGF的NSC治疗组在移植3周后NSE阳性细胞数明显增加(P<0.05), 与NSC治疗组比较,在移植6周末转染VEGF的NSC治疗组NSE的阳性细胞数增加更明显(P<0.05)。与放射性脑损伤组比,NSC治疗组和转染VEGF的NSC治疗组在移植3周末NSE蛋白表达量明显增加(P<0.05), 与NSC治疗组比较,在移植6周末转染VEGF的NSC组NSE蛋白表达量增加更明显(P<0.05)。结论：转染VEGF的NSC移植可提高放射性脑损伤组织中NSE的含量。     

干细胞移植治疗肝脏疾病的研究进展

背景：干细胞移植治疗肝病是近年来众多学者研究的热点,干细胞移植的基本理论和临床应用研究都取得了很大的进展。 目的：对干细胞移植的理论依据、干细胞来源、移植方式、实验与临床研究、存在问题及前景进行简要综述。 方法：应用计算机检索中国学术期刊全文数据库(CNKI)和Pubmed数据库中2001-01/2011-11关于干细胞移植治疗肝病的文章,检索主题词“干细胞,移植,肝脏疾病,肝损伤”或“stem cell,transplantation,hepatic disease, hepatic injury”。初检索到192篇文献,据纳入标准保留31篇进行分析、综述。 结果与结论：干细胞来源充足,容易获取,可以体外增殖培养,干细胞移植操作简单,安全性高,尤其自体干细胞移植可完全避免移植排斥反应。但自体干细胞移植肝脏疾病的安全性和有效性尚无公识,需更长期的观察。