Human neural stem cells genetically modified for brain repair in neurological disorders

Existence of multipotent neural stem cells (NSC) has been known in developing or adult mammalian CNS, including humans. NSC have the capacity to grow indefinitely and have multipotent potential to differentiate into three major cell types of CNS, neurons, astrocytes and oligodendrocytes. Stable clonal lines of human NSC have recently been generated from the human fetal telencephalon using a retroviral vector encoding v‐myc. One of the NSC lines, HB1.F3, carries normal human karyotype of 46XX and has the ability to self‐renew, differentiate into cells of neuronal and glial lineages, and integrate into the damaged CNS loci upon transplantation into the brain of animal models of Parkinson disease, HD, stroke and mucopolysaccharidosis. F3 human NSC were genetically engineered to produce L‐dihydroxyphenylalanine (L‐DOPA) by double transfection with cDNA for tyrosine hydroxylase and guanosine triphosphate cylohydrolase‐1, and transplantation of these cells in the brain of Parkinson disease model rats led to L‐DOPA production and functional recovery. Proactively transplanted F3 human NSC in rat striatum, supported the survival of host striatal neurons against neuronal injury caused by 3‐nitropro‐pionic acid in rat model of HD. Intravenously introduced through the tail vein, F3 human NSC were found to migrate into ischemic lesion sites, differentiate into neurons and glial cells, and improve functional deficits in rat stroke models. These results indicate that human NSC should be an ideal vehicle for cell replacement and gene transfer therapy for patients with neurological diseases. In addition to immortalized human NSC, immortalized human bone marrow mesenchymal stem cell lines have been generated from human embryonic bone marrow tissues with retroviral vectors encording v‐myc or teromerase gene. These immortalized cell lines of human bone marrow mesenchymal stem cells differentiated into neurons/glial cells, bone, cartilage and adipose tissue when they were grown in selective inducing media. There is further need for investigation into the neurogenic potential of the human bone marrow stem cell lines and their utility in animal models of neurological diseases.     

碱性成纤维细胞生长因子等体外诱导成人骨髓间充质干细胞分化为神经元样细胞的研究

目的 成人骨髓间充质干细胞(hMSCs)体外定向诱导分化为神经元样细胞。方法 采用Percoll分离液离心分离hMSCs，体外扩增，分别采用含碱性成纤维细胞生长因子(bFGF)和2-巯基乙醇(2-ME)等无血清DMEM诱导hMSCs分化为神经元。免疫组化鉴定神经元烯醇化酶(NSE)、神经丝蛋白(NF)、胶质纤维酸性蛋白(GFAP)。结果 hMSCs在体外扩增传至5代后，流式细胞仪显示99．5％，97．8％，98．8％hMSCs表面抗原CD29、CD44、CD90表达阳性。接种到12孔板，3d后加入bFGF和2-ME联合或2-ME单种诱导剂诱导后，hMSCs胞体收缩，突起伸出；免疫组化显示诱导出的神经元样细胞NSE、NF表达阳性，GFAP阴性。结论 成人骨髓间干细胞在体外可以分化为神经元样细胞。     

Peripheral glial cell differentiation from neurospheres derived from adipose mesenchymal stem cells

Mesenchymal stem cells derived from bone marrow and adipose tissue are being considered for use in neural repair because they can differentiate after appropriate induction in culture into neurons and glia. The question we asked was if neurospheres could be harvested from adipose-derived stem cells and if they then could differentiate in culture to peripheral glial-like cells. Here, we demonstrate that adipose-derived mesenchymal stem cells can form nestin-positive non-adherent neurosphere cellular aggregates when cultured with basic fibroblast growth factor and epidermal growth factor. Dissociation of these neurospheres and removal of mitogens results in expression of the characteristic Schwann cell markers S100 and p75 nerve growth factor receptor and GFAP. The simultaneous expression of these glia markers are characteristic features of Schwann cells and olfactory ensheathing cells which have unique properties regarding remyelination and enhancement of axonal regeneration. When co-cultured with dorsal root ganglion neurons, the peripheral glial-like cells derived from adipose mesenchymal stem cells aligned with neuritis and stimulated neuritic outgrowth. These results indicate that neurospheres can be generated from adipose-derived mesenchymal stem cells, and upon mitogen withdrawal can differentiate into peripheral glial cells with neurotrophic effects.     

Comparative analysis of neuroectodermal differentiation capacity of human bone marrow stromal cells using various conversion protocols

Human adult bone marrow-derived mesodermal stromal cells (hMSCs) are able to differentiate into multiple mesodermal tissues, including bone and cartilage. There is evidence that these cells are able to break germ layer commitment and differentiate into cells expressing neuroectodermal properties. There is still debate about whether this results from cell fusion, aberrant marker gene expression or real neuroectodermal differentiation. Here we extend our work on neuroectodermal conversion of adult hMSCs in vitro by evaluating various epigenetic conversion protocols using quantitative RT-PCR and immunocytochemistry. Undifferentiated hMSCs expressed high levels of fibronectin as well as several neuroectodermal genes commonly used to characterize neural cell types, such as nestin, beta-tubulin III, and GFAP, suggesting that hMSCs retain the ability to differentiate into neuroectodermal cell types. Protocols using a direct differentiation of hMSCs into a neural phenotype failed to induce significant changes in morphology and/or expression of markers of early and mature glial/neuronal cells types. In contrast, a multistep protocol with conversion of hMSCs into a neural stem cell-like population and subsequent terminal differentiation in mature glia and neurons generated relevant morphological changes as well as significant increase of expression levels of marker genes for early and late neural cell types, such as nestin, neurogenin2, MBP, and MAP2ab, accompanied by a loss of their mesenchymal properties. Our data provide an impetus for differentiating hMSCs in vitro into mature neuroectodermal cells. Neuroectodermally converted hMSCs may therefore ultimately help in treating acute and chronic neurodegenerative diseases. Analysis of marker gene expression for characterization of neural cells derived from MSCs has to take into account that several early and late neuroectodermal genes are already expressed in undifferentiated MSCs.     

大鼠胚胎神经干细胞的冷冻复苏

目的：建立大鼠胚胎神经干细胞冷冻复苏方法，探讨冻存后神经干细胞的活力及生物学特性。方法：采用10％BSA＋7．5％DMSO作冷冻保护剂，于液氮中冻存；采用细胞培养和间接免疫荧光染色方法对冻存后细胞的活力，形态及分化能力作鉴定。结果：不同的冻存时间，细胞代数，组织来源以及神经营养因子对冻存后细胞存活率没有明显差异（P＞0．05）。冷冻保存复苏后培养的大鼠胚胎神经干细胞能够存活，能在体外多次传代，并能分化成神经元，星形胶质细胞细胞和少突胶质细胞。结论：大鼠神经干细胞的冻存复苏并不影响其原有的生物学特性包括其正常的，增殖能力和多向分化能力。     

Transplantation of placenta-derived mesenchymal stem cell-induced neural stem cells to treat spinal cord injury

Because of their strong proliferative capacity and multi-potency, placenta-derived mesenchymal stem cells have gained interest as a cell source in the field of nerve damage repair. In the present study, human placenta-derived mesenchymal stem ceils were induced to differentiate into neural stem cells, which were then transplanted into the spinal cord after local spinal cord injury in rats. The motor functional recovery and pathological changes in the injured spinal cord were observed for 3 successive weeks. The results showed that human placenta-derived mesenchymal stem cells can differentiate into neuron-like cells and that induced neural stem cells contribute to the restoration of injured spinal cord without causing transplant rejection. Thus, these cells promote the recovery of motor and sensory functions in a rat model of spinal cord injury. Therefore, human placenta-derived mesenchymal stem cells may be useful as seed cells during the repair of spinal cord injury.     

神经干细胞的来源

神经干细胞是近年来神经科学领域研究的一个热点。神经干细胞可来源于胚胎干细胞和成年干细胞，前者包括早期胚胎细胞和胎儿神经组织细胞，由于从胚胎获取干细胞面l临伦理学的束缚，从成年来源的神经干细胞将是未来临床应用更具可行性的途径。成年来源的神经干细胞包括存在于成年神经组织中的干细胞和从其他组织中分化得到的干细胞，其中骨髓基质细胞具有多分化潜能，在适当的条件下可以诱导分化出神经干细胞，目前备受关注。     

成年小鼠嗅球神经干细胞的培养和鉴定

目的 建立完善的成年小鼠嗅球神经千细胞分离培养和鉴定方法,探索新的成年神经干细胞种子来源. 方法 用无血清方法 分离培养成年小鼠嗅球来源的神经干细胞;用克隆培养、5-溴2-脱氧尿嘧啶核昔(BrdU)整合的方法 检验培养细胞的干细胞特性;用免疫荧光细胞化学的方法 检测BrdU、神经干细胞标记物巢蛋白(nestin)和SOX2、分化的细胞标记物Tuj1、胶质纤维酸性蛋白(GFAP)、04的表达. 结果 从成年小鼠嗅球能够分离、培养出具有自我更新、增殖能力的神经球.构成神经球的细胞呈nestin和SOX2阳性,它们分化后产生TuJ1阳性的神经元、GFAP阳性的星形胶质细胞、04阳性的少突胶质细胞. 结论 成年小鼠嗅球存在神经干细胞,其能够在体外进行培养、增殖、分化.是神经干细胞的新的种子来源.     

新生小鼠端脑组织神经干细胞诱导分化为胆碱能神经元的研究

目的探讨新生小鼠端脑组织神经干细胞是否能够分化成胆碱能神经元。方法取新生小鼠端脑组织．用无血清方法分离培养神经干细胞；用克隆培养的方法检验培养细胞的干细胞特性；用免疫荧光细胞化学的方法检测神经干细胞标志巢蛋白（nestin）及干细胞诱导分化后神经元标志微管相关蛋白2（MAP2）、星形胶质细胞标志胶质纤维酸性蛋白（GFAP）、胆碱能标志胆碱乙酰转移酶（CHAT）；比较不同的诱导分化条件（5％胎牛血清、5％胎牛血清＋碱性成纤维细胞生长因子）对胆碱能神经元分化的影响。结果从新生小鼠端脑组织分离培养出具有自我更新、扩增能力的神经球；各培养基中神经球均为nestin阳性。诱导分化后均能够产生MAP2阳性神经元、GFAP阳性星形胶质细胞以及ChAT阳性的胆碱能神经元。分化培养中加入碱性成纤维细胞生长因子能够提高胆碱能神经元分化的比例。结论新生小鼠端脑组织神经干细胞能够分化成胆碱能神经元。     

Human bone marrow stem cells exhibit neural phenotypes and ameliorate neurological deficits after grafting into the ischemic brain of rats

There is now evidence to suggest that bone marrow mesenchymal stem cells (MSCs) not only differentiate into mesodermal cells, but can also adopt the fate of endodermal and ectodermal cell types. In this study, we addressed the hypotheses that human MSCs can differentiate into neural cells when implanted in the brain and restore sensorimotor function after experimental stroke. Purified human MSCs were grafted into the cortex surrounding the area of infarction 1 week after cortical brain ischemia in rats. Two and 6 weeks after transplantation animals were assessed for sensorimotor function and then sacrificed for histological examination. Ischemic rats that received human MSCs exhibited significantly improved functional performance in limb placement test. Histological analyses revealed that transplanted human MSCs expressed markers for astrocytes (GFAP(+)), oligodendroglia (GalC(+)), and neurons (beta III(+), NF160(+), NF200(+), hNSE(+), and hNF70(+)). The morphological features of the grafted cells, however, were spherical in nature with few processes. Therefore, it is unlikely that the functional recovery observed by the ischemic rats with human MSC grafts was mediated by the integration of new "neuronal" cells into the circuitry of the host brain. The observed functional improvement might have been mediated by proteins secreted by transplanted hMSCs, which could have upregulated host brain plasticity in response to experimental stroke.     

不同代数的成人骨髓间充质干细胞体外转化为神经细胞的实验研究

目的　探讨不同代数的成人骨髓间充质干细胞 ( h MSCs)体外向神经元细胞转化的效率 ,为骨髓间充质干细胞应用于临床提供可靠的实验数据。方法　采用 β-巯基乙醇做为诱导剂 ,选用第 2、4、6、8代 h MSCs在体外诱导 6 h后 ,用细胞化学及免疫组织化学检测神经元细胞、星形胶质细胞标记蛋白的表达。结果　第 2、4、6代h MSCs诱导后胞浆中均可见深蓝色的颗粒状尼氏体 ,第 8代 h MSCs诱导 6 h后胞浆中未见明显的深蓝色尼氏体结构。不同代数的 h MSCs经诱导 6 h后均表达 NSE、NF- M,不表达 GFAP;第 2、4、6代的阳性率无显著性差异 ( P>0 .0 5 ) ,第 8代与第 2、4、6代的阳性率有显著性差异 ( P<0 .0 5 )。结论　 β-巯基乙醇在体外可定向诱导 h MSCs转化为神经元细胞 ,第 2、4、6代的阳性率明显高于第 8代。     

Quiescent neural cells regain multipotent stem cell characteristics influenced by adult neural stem cells in co-culture

The source of cells participating in central nervous system (CNS) tissue repair and regeneration is poorly defined. One possible source is quiescent neural cells that can persist in CNS in the form of dormant progenitors or highly specialized cell types. Under appropriate conditions, these quiescent cells may be capable of re-entering the mitotic cell cycle and contributing to the stem cell pool. The aim of this study was to determine whether in vitro differentiated neural stem cells (NSC) can regain their multipotent-like stem cell characteristics in co-culture with NSC. To this end, we induced neural differentiation by plating NSC, derived from the periventricular subependymal zone (SEZ) of ROSA26 transgenic mice in Neurobasal A/B27 medium in the absence of bFGF. Under these conditions, NSC differentiated into neurons, glia, and oligodendrocytes. While the level of Nestin expression was downregulated, persistence of dormant progenitors could not be ruled out. However, further addition of bFGF or bFGF/EGF with conditioned medium derived from adult NSC did not induce any noticeable cell proliferation. In another experiment, differentiated neural cells were cultured with adult NSC, isolated from the hippocampus of Balb/c mice, in the presence bFGF. This resulted in proliferating colonies of ROSA26 derived cells that mimicked NSC in their morphology, growth kinetics, and expressed NSC marker proteins. The average nuclear area and DAPI fluorescence intensity of these cells were similar to that of NSC grown alone. We conclude that reactivation of quiescent neural cells can be initiated by NSC-associated short-range cues but not by cell fusion.     

Neuroprotective effects of human bone marrow mesenchymal stem cells against cerebral ischemia are mediated in part by an anti-apoptotic mechanism

Transplantation of human bone marrow mesenchymal stem cells(hMSCs) stands as a potent stroke therapy, but its exact mechanism remains unknown. This study investigated the anti-apoptotic mechanisms by which hMSCs exert neuroprotective effects on cerebral ischemia. Primary mixed cultures of rat neurons and astrocytes were cultured and exposed to oxygen-glucose deprivation. A two-hour period of "reperfusion" in standard medium and normoxic conditions was allowed and immediately followed by hMSCs and/or Bcl-2 antibody treatment. Cell viability of primary rat neurons and astrocytes was determined by 3-(4,5-dimethylthianol-2-yl)-2,5 diphenyl tetrazolium bromide and trypan blue exclusion methods. hMSC survival and differentiation were characterized by immunocytochemistry, while the concentration of Bcl-2 in the supernatant was measured by enzyme-linked immunosorbent assay to reveal the secretory anti-apoptotic function of hMSCs. Cultured hMSCs expressed embryonic-like stem cell phenotypic markers CXCR4, Oct4, SSEA4, and Nanog, as well as immature neural phenotypic marker Nestin. Primary rat neurons and astrocytes were protected from oxygen-glucose deprivation by hMSCs, which was antagonized by the Bcl-2 antibody. However, Bcl-2 levels in the supernatants did not differ between hMSCand non-treated cells exposed to oxygen-glucose deprivation. Neuroprotective effects of hMSCs against cerebral ischemia were partially mediated by the anti-apoptotic mechanisms. However, further studies are warranted to fully elucidate this pathway.     

Human skin-derived stem cells migrate throughout forebrain and differentiate into astrocytes after injection into adult mouse brain

Recent evidence indicates that neural stem cell properties can be found among a mammalian skin-derived multipotent population. A major barrier in the further characterization of the human skin-derived neural progenitors is the inability to isolate this population based on expression of cell surface markers. Our work has been devoted to purified human skin-derived stem cells that are capable of neural differentiation, based on the presence or absence of the AC133 cell surface marker. The enriched skin-derived AC133(+) cells express the CD34 and Thy-1 antigens. These cells cultured in a growth medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) proliferate, forming spheres, and differentiate in vitro into neurons, astrocytes, and rarely into oligodendrocytes. Single cells from sphere cultures initiated from human purified AC133(+) cells were replated as single cells and were able to generate new spheres, demonstrating the self-renewing ability of these stem cell populations. Brain engraftment of cells obtained from human purified AC133(+)-derived spheres generated different neural phenotypes: immature neurons and a most abundant population of well differentiated astrocytes. The AC133-derived astrocytes assumed perivascular locations in the frontal cortex. No donor-derived oligodendrocytes were found in the transplanted mouse brains. Several donor small, rounded cells that expressed endothelial markers were found close to the host vessel and near the subventricular zone. Thus, mammalian skin AC133-derived cells behave as a multipotent population with the capacity to differentiate into neural lineages in vitro and, prevalently, endothelium and astrocytes in vivo, demonstrating the great plasticity of these cells and suggesting potential clinical application.     

Differentiation of human adult CD34+ stem cells into cells with a neural phenotype: role of astrocytes

It has recently been reported that adult hematopoietic stem cells can differentiate into neural cells, opening new frontiers in therapy for neurodegenerative diseases. In this study, adult human hematopoietic stem cells (HSCs) were isolated via magnetic bead sorting, using a specific CD34 antibody and cultured with human astrocyte culture conditioned medium (ACM). In order to evaluate their differentiation into neurons and/or astrocytes, ACM-treated cultures were probed for the expression of several neural markers. We observed morphological modifications and, after 20 days of treatment, cell morphology displayed extending processes. Immunocytochemistry, Western blotting and RT-PCR showed the expression of neuronal markers such as neurofilaments, neuron specific enolase (NSE) and NeuN in ACM-treated HSCs cultured in poly-L-lysine-coated dishes. On the contrary, when the same ACM-treated cells were grown on a plastic substrate, they expressed high levels of glial fibrillary acidic protein (GFAP), with only weak expression of neuronal markers. Nestin, a neural progenitor cell marker, was present in treated cells, regardless of the substrate. These results demonstrate that astrocytes can generate a suitable microenvironment for inducing HSCs to differentiate into neural cells. Therefore, adult bone marrow may represent a readily accessible source of cells for treating neurodegenerative diseases.     

Neurons derived from human-induced pluripotent stem cells express mu and kappa opioid receptors

Neuroprotection studies have shown that induced pluripotent stem(iPS) cells have the possibility to transform neuroprotection research. In the present study, iPS cells were generated from human renal epithelial cells and were then differentiated into neurons. Cells in the iPScell group were maintained in stem cell medium. In contrast, cells in the iPS-neuron group were first maintained in neural induction medium and expansion medium containing ROCK inhibitors, and then cultivated in neuronal differentiation medium and neuronal maturation medium to induce the neural stem cells to differentiate into neurons. The expression of relevant markers was compared at different stages of differentiation. Immunofluorescence staining revealed that cells in the iPS-neuron group expressed the neural stem cell markers SOX1 and nestin on day 11 of induction, and neuronal markers TUBB3 and NeuN on day 21 of induction. Polymerase chain reaction results demonstrated that, compared with the iPS-cell group, TUBB3 gene expression in the iPS-neuron group was increased 15.6-fold. Further research revealed that, compared with the iPS-cell group, the gene expression and immunoreactivity of mu opioid receptor in the iPS-neuron group were significantly increased(38.3-fold and 5.7-fold, respectively), but those of kappa opioid receptor had only a slight change(1.33-fold and 1.57-fold increases, respectively). Together, these data indicate that human iPS cells can be induced into mu opioid receptor-and kappa opioid receptor-expressing neurons, and that they may be useful to simulate human opioid receptor function in vitro and explore the underlying mechanisms of human conditions.     

Differentiation of mesenchymal stem cells into neuronal cells on fetal bovine acellular dermal matrix as a tissue engineered nerve scaffold

The purpose of this study was to assess fetal bovine acellular dermal matrix as a scaffold for supporting the differentiation of bone marrow mesenchymal stem cells into neural cells following induction with neural differentiation medium.We performed long-term,continuous observation of cell morphology,growth,differentiation,and neuronal development using several microscopy techniques in conjunction with immunohistochemistry.We examined specific neuronal proteins and Nissl bodies involved in the differentiation process in order to determine the neuronal differentiation of bone marrow mesenchymal stem cells.The results show that bone marrow mesenchymal stem cells that differentiate on fetal bovine acellular dermal matrix display neuronal morphology with unipolar and bi/multipolar neurite elongations that express neuronal-specific proteins,including βIII tubulin.The bone marrow mesenchymal stem cells grown on fetal bovine acellular dermal matrix and induced for long periods of time with neural differentiation medium differentiated into a multilayered neural network-like structure with long nerve fibers that was composed of several parallel microfibers and neuronal cells,forming a complete neural circuit with dendrite-dendrite to axon-dendrite to dendrite-axon synapses.In addition,growth cones with filopodia were observed using scanning electron microscopy.Paraffin sectioning showed differentiated bone marrow mesenchymal stem cells with the typical features of neuronal phenotype,such as a large,round nucleus and a cytoplasm full of Nissl bodies.The data suggest that the biological scaffold fetal bovine acellular dermal matrix is capable of supporting human bone marrow mesenchymal stem cell differentiation into functional neurons and the subsequent formation of tissue engineered nerve.     

Immortalized neural stem cells differ from nonimmortalized cortical neurospheres and cerebellar granule cell progenitors

Pluripotent neural stem cells (NSCs) have been used as replacement cells in a variety of neurological disease models. Among the many different NSCs that have been used to date, most robust results have been obtained with the immortalized neural stem cell line (C17.2) isolated from postnatal cerebellum. However, it is unclear if other NSCs isolated from different brain regions are similar in their potency as replacement therapies. To assess the properties of NSC-like C17.2 cells, we compared the properties of these cells with those reported for other NSC populations identified by a variety of different investigators using biological assays, microarray analysis, RT-PCR, and immunocytochemistry. We show that C17.2 cells differ significantly from other NSCs and cerebellar granule cell precursors, from which they were derived. In particular, they secrete additional growth factors and cytokines, express markers that distinguish them from other progenitor populations, and do not maintain karyotypic stability. Our results provide a caution on extrapolating results from C17.2 to other nonimmortalized stem cell populations and provide an explanation for some of the dramatic effects that are seen with C17.2 transplants but not with other cells. We suggest that, while C17.2 cells can illustrate many fundamental aspects of neural biology and are useful in their own right, their unique properties cannot be generalized.