Clonal analysis of thymus-repopulating cells presents direct evidence for self-renewal division of human hematopoietic stem cells

To elucidate the in vivo kinetics of human hematopoietic stem cells (HSCs), CD34+CD38- cells were infected with lentivirus vector and transplanted into immunodeficient mice. We analyzed the multilineage differentiation and self-renewal abilities of individual thymus-repopulating clones in primary recipients, and their descending clones in paired secondary recipients, by tracing lentivirus gene integration sites in each lymphomyeloid progeny using a linear amplification-mediated polymerase chain reaction (PCR) strategy. Our clonal analysis revealed that a single human thymus-repopulating cell had the ability to produce lymphoid and myeloid lineage cells in the primary recipient and each secondary recipient, indicating that individual human HSCs expand clonally by self-renewal division. Furthermore, we found that the proportion of HSC clones present in the CD34+ cell population decreased as HSCs replicated during extensive repopulation and also as the differentiation capacity of the HSC clones became limited. This indicates the restriction of the ability of individual HSCs despite the expansion of total HSC population. We also demonstrated that the extensive self-renewal potential was confined in the relatively small proportion of HSC clones. We conclude that our clonal tracking studies clearly demonstrated that heterogeneity in the self-renewal capacity of HSC clones underlies the differences in clonal longevity in the CD34+ stem cell pool.     

恶性脑胶质瘤U87细胞系肿瘤干细胞放疗敏感性的体外实验研究

目的探讨脑胶质瘤细胞系U87细胞及其肿瘤干细胞（CSCs）对体外放疗的敏感性。方法应用神经干细胞（NSCs）培养基分离培养形成细胞球克隆,检测细胞球细胞的NSCs特性。采用不同剂量放射线照射U87细胞及其CSCs,应用集落形成实验和生存曲线检测其生存情况。结果 U87细胞在NSCs培养基中形成悬浮的细胞球克隆,具有自我更新和多向分化能力,表达CD133、Nestin;两种细胞的存活率均随照射剂量增加而下降,且CSCs的存活率明显高于U87细胞（P〈0.01）。结论在体外条件下,CSCs的放射敏感性明显低于U87细胞,其可能是恶性脑胶质瘤放疗抵抗的主要原因。     

大肠癌细胞系Lovo中亚群(SP)细胞的分离培养和鉴定

目的:应用无血清培养液(SFM)培养Lovo细胞系,克隆分离具有干细胞样特性SP细胞.方法:应用SFM培养Lovo细胞,分离成球样生长的细胞群作为SP细胞,并通过有限稀释,分化,自我更新,含血清培养基(SSM)和SFM交替培养及Musashi-1化学染色方法来鉴定SP细胞.结果:Lovo细胞中约含有0.54%-0.62%的SP能够在无血清培养基中能够存活、增殖,形成悬浮的肿瘤细胞球;在SFM中加入血清可促使SP细胞分化;SP细胞可以连续传代,并可交替培养于SSM和SFM中,细胞形态无明显变化;SP细胞Musashi-1染色阳性.结论:应用SFM可从Lovo细胞中分离出极少量的具有干细胞特性的SP细胞.     

Cells previously identified as retinal stem cells are pigmented ciliary epithelial cells

It was previously reported that the ciliary epithelium (CE) of the mammalian eye contains a rare population of cells that could produce clonogenic self-renewing pigmented spheres in culture. Based on their ability to up-regulate genes found in retinal neurons, it was concluded that these sphere-forming cells were retinal stem cells. This conclusion raised the possibility that CE-derived retinal stem cells could help to restore vision in the millions of people worldwide who suffer from blindness associated with retinal degeneration. We report here that human and mouse CE-derived spheres are made up of proliferating pigmented ciliary epithelial cells rather than retinal stem cells. All of the cells in the CE-derived spheres, including the proliferating cells, had molecular, cellular, and morphological features of differentiated pigmented CE cells. These differentiated cells ectopically expressed nestin when exposed to growth factors and low levels of pan-neuronal markers such as beta-III-tubulin. Although the cells aberrantly expressed neuronal markers, they retained their pigmented CE cell morphology and failed to differentiate into retinal neurons in vitro or in vivo. Our results provide an example of a differentiated cell type that can form clonogenic spheres in culture, self-renew, express progenitor cell markers, and initiate neuronal differentiation that is not a stem or progenitor cell. More importantly, our findings highlight the importance of shifting the focus away from studies on CE-derived spheres for cell-based therapies to restore vision in the degenerating retina and improving techniques for using ES cells or retinal precursor cells.     

Sphere-forming cell subpopulations with cancer stem cell properties in human hepatoma cell lines

Background

Cancer stem cells (CSCs) are regarded as the cause of tumor formation and recurrence. The isolation and identification of CSCs could help to develop novel therapeutic strategies specifically targeting CSCs.

Methods

Human hepatoma cell lines were plated in stem cell conditioned culture system allowed for sphere forming. To evaluate the stemness characteristics of spheres, the self-renewal, proliferation, chemoresistance, tumorigenicity of the PLC/PRF/5 sphere-forming cells, and the expression levels of stem cell related proteins in the PLC/PRF/5 sphere-forming cells were assessed, comparing with the parental cells. The stem cell RT-PCR array was performed to further explore the biological properties of liver CSCs.

Results

The PLC/PRF/5, MHCC97H and HepG2 cells could form clonal nonadherent 3-D spheres and be serially passaged. The PLC/PRF/5 sphere-forming cells possessed a key criteria that define CSCs: persistent self-renewal, extensive proliferation, drug resistance, overexpression of liver CSCs related proteins (Oct3/4, OV6, EpCAM, CD133 and CD44). Even 500 sphere-forming cells were able to form tumors in NOD/SCID mice, and the tumor initiating capability was not decreased when spheres were passaged. Besides, downstream proteins DTX1 and Ep300 of the CSL (CBF1 in humans, Suppressor of hairless in Drosophila and LAG1 in C. elegans) -independent Notch signaling pathway were highly expressed in the spheres, and a gamma-secretase inhibitor MRK003 could significantly inhibit the sphere formation ability.

Conclusions

Nonadherent tumor spheres from hepatoma cell lines cultured in stem cell conditioned medium possess liver CSC properties, and the CSL-independent Notch signaling pathway may play a role in liver CSCs.     

Altered stem cell (CFU-S) function following infection of hematopoietic cells with a virus carrying V-src

Long-term murine bone marrow cultures were used to support the growth and development of hematopoietic cells. After hematopoiesis was established, the cultures were infected with a recombinant murine amphotropic virus carrying the avian sarcoma virus src gene and the CFU- S kinetics were examined. The CFU-S from the src-infected cultures displayed a reduced seeding efficiency in the standard spleen colony assay. The self-renewal capacity of these CFU-S was tested by their ability to reestablish hematopoiesis when serially transplanted on irradiated bone marrow cultures and by serial passage in spleens of irradiated mice. In both tests, cells from the src-infected cultures exhibited an enhanced ability to sustain a high level of self-renewal. The other property of stem cells which may be measured is the probability of self-renewal at each cell division which dictates the distribution between stem cells and differentiated type progeny. CFU-S from the src-infected cultures had higher average probabilities of self- renewal and therefore reduced differentiation. These differences suggest that expression of src had indirectly or directly altered the normal differentiation program of the stem cells.     

Transgenic mice produced by retroviral transduction of male germ-line stem cells

Male germ-line stem cells are the only cell type in postnatal mammals that have the capability to self-renew and to contribute genes to the next generation. Genetic modification of these cells would provide an opportunity to study the biology of their complex self-renewal and differentiation processes, as well as enable the generation of transgenic animals in a wide range of species. Although retroviral vectors have been used as an efficient method to introduce genes into a variety of cell types, postnatal male germ-line stem cells have seemed refractory to direct infection by these viruses. In addition, expression of genes transduced into several types of stem cells, such as embryonic or hematopoietic, is often attenuated or silenced. We demonstrate here that in vitro retroviral-mediated gene delivery into spermatogonial stem cells of both adult and immature mice results in stable integration and expression of a transgene in 2-20% of stem cells. After transplantation of the transduced stem cells into the testes of infertile recipient mice, approximately 4.5% of progeny from these males are transgenic, and the transgene is transmitted to and expressed in subsequent generations. Therefore, there is no intrinsic barrier to retroviral transduction in this stem cell, and transgene expression is not extinguished after transmission to progeny.     

胃癌干细胞的分离鉴定以及干细胞特性研究

背景:肿瘤干细胞(CSCs)已成为当前肿瘤研究的热点之一,开展相关研究的首要问题是CSCs的分离和鉴定,悬浮培养法是分离CSCs的重要方法。目的:分离、鉴定胃癌干细胞(GCSCs)并评价其干细胞特性。方法:人胃癌细胞株MKN45、MGC803、SGC7901以含表皮生长因子(EGF)、碱性成纤维细胞生长因子(bFGF)的无血清培养基悬浮培养。对培养得到的第三代肿瘤球,以集落形成实验检测其克隆形成能力,免疫荧光法检测GCSCs标记物,细胞划痕实验和Transwell小室细胞侵袭实验检测其迁移、侵袭能力,CCK-8实验检测其对顺铂的耐药性。结果:培养得到的肿瘤球高表达干细胞标记物CD44、CD54,低表达胃壁细胞标记物H+/K+-ATPase,克隆形成能力、划痕愈合速度和Transwell小室穿膜细胞数明显大于或多于普通胃癌细胞,差异有统计学意义(P0.05)。顺铂对肿瘤球的50%抑制浓度明显高于普通胃癌细胞。结论:应用无血清培养基悬浮培养法能成功获得GCSCs富集的肿瘤球;肿瘤球具有较强的自我更新、增殖、迁移、侵袭能力和多向分化潜能,对化疗药物更易产生耐药性。     

脑胶质瘤干细胞的体外培养与生物学特性观察

目的体外培养人脑胶质瘤干细胞并观察其生物学特性。方法应用无血清培养技术,从手术中获取的人脑胶质瘤组织培养得到肿瘤干细胞,诱导其分化后与原肿瘤组织细胞进行比较。应用细胞免疫荧光技术鉴定肿瘤干细胞表面标志物。结果分别在间变性星形细胞瘤和胶质母细胞瘤中培养得到悬浮生长的肿瘤干细胞球,其能在体外自我更新、增殖,形成新的克隆性细胞球,保持连续稳定的传代,能表达神经干细胞表面标志物CD 133。在含血清培养基中能够分化为与原肿瘤组织相似的贴壁生长的细胞。结论人脑胶质瘤中存在一定量的肿瘤干细胞,能够自我更新增殖、诱导分化、表达干细胞标志物CD 133。为探讨脑胶质瘤的发病机制奠定了基础。     

CD133(+) gallbladder carcinoma cells exhibit self-renewal ability and tumorigenicity

AIM:To identify cancer stem cells(CSCs) in human gallbladder carcinomas(GBCs).METHODS:Primary GBC cells were cultured under serum-free conditions to produce floating spheres.The stem-cell properties of the sphere-forming cells,including self-renewal,differentiation potential,chemoresistance and tumorigenicity,were determined in vitro or in vivo.Cell surface expression of CD133 was investigated in primary tumors and in spheroid cells using flow cytometry.The sphere-colony-formation ability and tumorigenicity...     

Evidence of an epithelial stem/progenitor cell hierarchy in the adult mouse lung

The role of lung epithelial stem cells in maintenance and repair of the adult lung is ill-defined, and their identity remains contentious because of the lack of definitive markers for their prospective isolation and the absence of clonogenic assays able to measure their stem/progenitor cell potential. In this study, we show that replication of epithelial–mesenchymal interactions in a previously undescribed matrigel-based clonogenic assay enables the identification of lung epithelial stem/progenitor cells by their colony-forming potential in vitro. We describe a population of EpCAM^hi CD49f^pos CD104^pos CD24^low epithelial cfus that generate colonies comprising airway, alveolar, or mixed lung epithelial cell lineages when cocultured with EpCAM^neg Sca-1^pos lung mesenchymal cells. We show that soluble fibroblast growth factor-10 and hepatocyte growth factor partially replace the requirement for mesenchymal support of epithelial colony formation, allowing clonal passaging and demonstration of their capacity for self-renewal. These data support a model in which the adult mouse lung contains a minor population of multipotent epithelial stem/progenitor cells with the capacity for self-renewal and whose descendants give rise to airway and alveolar epithelial cell lineages in vitro.     

β1- and α6-integrin are surface markers on mouse spermatogonial stem cells

Although spermatogenesis is essential for reproduction, little is known about spermatogonial stem cells. These cells provide the basis for spermatogenesis throughout adult life by undergoing self-renewal and by providing progeny that differentiate into spermatozoa. A major impediment to our understanding of the biology of these stem cells is the inability to distinguish them from spermatogonia that are committed to differentiation. We made use of the known association of stem cells with basement membranes and our spermatogonial transplantation assay system to identify specific molecular markers on the stem cell surface. Selection of mouse testis cells with anti-beta1- or anti-alpha6-integrin antibody, but not anti-c-kit antibody, produced cell populations with a significantly enhanced ability to colonize recipient testes and generate donor cell-derived spermatogenesis. We demonstrate spermatogonial stem cell-associated antigens by using an assay system based on biological function. Furthermore, the presence of surface integrins on spermatogonial stem cells suggests that these cells share elements of a common molecular machinery with stem cells in other tissues.     

Hedgehog signaling maintains a tumor stem cell compartment in multiple myeloma

The cancer stem cell hypothesis suggests that malignant growth depends on a subset of tumor cells with stem cell-like properties of self-renewal. Because hedgehog (Hh) signaling regulates progenitor cell fate in normal development and homeostasis, aberrant pathway activation might be involved in the maintenance of such a population in cancer. Indeed, mutational activation of the Hh pathway is associated with medulloblastoma and basal cell carcinoma; pathway activity is also critical for growth of other tumors lacking such mutations, although the mechanism of pathway activation is poorly understood. Here we study the role and mechanism of Hh pathway activation in multiple myeloma (MM), a malignancy with a well defined stem cell compartment. In this model, rare malignant progenitors capable of clonal expansion resemble B cells, whereas the much larger tumor cell population manifests a differentiated plasma cell phenotype that pathologically defines the disease. We show that the subset of MM cells that manifests Hh pathway activity is markedly concentrated within the tumor stem cell compartment. The Hh ligand promotes expansion of MM stem cells without differentiation, whereas the Hh pathway blockade, while having little or no effect on malignant plasma cell growth, markedly inhibits clonal expansion accompanied by terminal differentiation of purified MM stem cells. These data reveal that Hh pathway activation is heterogeneous across the spectrum of MM tumor stem cells and their more differentiated progeny. The potential existence of similar relationships in other adult cancers may have important biologic and clinical implications for the study of aberrant Hh signaling.     

Proliferative capacity of murine hematopoietic stem cells.

The present study demonstrates a decrease in self-renewal capacity with serial transfer of murine hematopoietic stem cells. Production of differentiated cell progeny is maintained longer than stem cell self-renewal. In normal animals the capacity for self-renewal is not decreased with increasing donor age. The stem cell compartment in normal animals, both young and old, appears to be proliferative quiescent. After apparent recovery from the alkylating agent busulfan, the probability of stem cell self-renewal is decreased, there is a permanent defect in the capacity of the bone marrow for serial transplantation, and the stem cells are proliferatively active. These findings support a model of the hematopoietic stem cell compartment as a continuum of cells with decreasing capacities for self-renewal, increasing likelihood for differentiation, and increasing proliferative activity. Cell progress in the continuum in one direction and such progression is not reversible.     

Direct isolation of human central nervous system stem cells

Stem cells, which are clonogenic cells with self-renewal and multilineage differentiation properties, have the potential to replace or repair damaged tissue. We have directly isolated clonogenic human central nervous system stem cells (hCNS-SC) from fresh human fetal brain tissue, using antibodies to cell surface markers and fluorescence-activated cell sorting. These hCNS-SC are phenotypically 5F3 (CD133)(+), 5E12(+), CD34(-), CD45(-), and CD24(-/lo). Single CD133(+) CD34(-) CD45(-) sorted cells initiated neurosphere cultures, and the progeny of clonogenic cells could differentiate into both neurons and glial cells. Single cells from neurosphere cultures initiated from CD133(+) CD34(-) CD45(-) cells were again replated as single cells and were able to reestablish neurosphere cultures, demonstrating the self-renewal potential of this highly enriched population. Upon transplantation into brains of immunodeficient neonatal mice, the sorted/expanded hCNS-SC showed potent engraftment, proliferation, migration, and neural differentiation.     

CD117阳性细胞亚群在肝癌细胞系HepG2中的分离及其特性

目的:观察从人肝癌细胞系HepG2中分离的CD117+细胞生物学行为,探讨肝癌中CD117+细胞亚群的干细胞特性.方法:采用无血清悬浮培养法培养HepG2细胞,流式细胞术检测HepG2及球体细胞中CD117的表达比例.用流式细胞分选技术从HepG2成球细胞中分离CD117+的肿瘤细胞,进行无血清悬浮培养,观察其成球能力.CCK-8法观察CD117+细胞的增殖能力和顺铂对CD117+细胞的抑制率,计算IC50和耐药指数(RI).结果:HepG2细胞能在无血清培养基中存活、增殖并形成细胞球,成球率为6.21%±2.03%;流式细胞检测发现球体细胞中CD117+细胞的比例比HepG2细胞提升了9倍;CD117+细胞在无血清培养基中成球率和增殖能力均显著高于未分选细胞和CD117细胞;CD117+细胞在各浓度的顺铂作用下抑制率均较未分选细胞和CD117细胞明显降低,三者IC50分别为12.229μmol/L、7.970μmol/L和7.345μmol/L,CD117+细胞和未分选细胞耐药系数RI为1.165和1.076.结论:人肝癌细胞系HepG2中的CD117+细胞是具有肿瘤干细胞特性的细胞亚群,CD117可能是肝...     

Human embryonic stem cell telomere length impacts directly on clonal progenitor isolation frequency

The pluripotentiality of human embryonic stem cells is expected to yield an abundance of clinically useful cell types. Using physiologic oxygen culture systems, we show that it is possible to isolate highly proliferative clonal progenitor cells from partially differentiated human embryonic stem cells. These progenitors have similar, though not identical, immunophenotypes with a resemblance to bone marrow-derived adherent stem cells. Through telomere length analysis of multiple early senescing clones, we were able to show that the starting telomere length of a human embryonic stem cell line impacts on the proliferative potential of clonally isolated partially differentiated mortal progeny. Proliferative clones undergo growth arrest with telomere lengths consistent with telomere-driven replicative senescence. To bypass this phenomenon, we transduced progenitor cells with ectopic hTERT (the limiting catalytic component of telomerase). This enabled telomerase immortalization without affecting differentiation potential or immunophenotype. In summary we describe the derivation of clonal progenitor cells from human embryonic stem cells and the relevance of parental cell telomere length to the frequency of highly proliferative clone isolation.     

A recombinant retrovirus encoding alkaline phosphatase confirms clonal boundary assignment in lineage analysis of murine retina.

Recombinant retroviruses encoding the histochemically detectable enzyme beta-galactosidase have been used to investigate lineage in the vertebrate nervous system. Identification of the descendants of individual progenitors is straightforward when progeny cells are arranged in a reproducible, clustered pattern, but difficulties in interpretation arise when progeny migrate extensively and/or in an irregular pattern. To better resolve clonal boundaries, additional histochemical marker viruses that engender distinctive reaction products can be used in combination with lacZ-bearing viruses. To this end, we have created a retrovirus vector, DAP, encoding an easily assayable enzyme, human placental alkaline phosphatase. DAP was found to be at least as useful as a lacZ-encoding retrovirus (e.g., BAG) with respect to high viral titer, stability of expression, and in identification of infected cells in vivo. Moreover, it was found to be neutral with respect to postnatal rodent retinal development and offered superior staining characteristics relative to lacZ. Coinfection of rodent retina with DAP and BAG allowed an examination of the clonal nature of radial arrays of labeled retinal cells that previously had been described as products of a single infected progenitor. Of 1100 radial arrays examined for the presence of both DAP- and BAG-infected cells, only 1.2% were the result of infection with more than one virus.     

Self-renewal of hemopoietic stem cells during mixed colony formation in vitro.

Replating experiments have shown that the self-renewal of pluripotent hemopoietic stem cells can be studied in vitro by clonal analysis techniques. The number of daughter stem cells detectable in individual primary clones produced in vitro varies markedly from one clone to another. These findings are consistent with a general model of stem cell differentiation in which the choice to self-replicate or not is ultimately determined at the single-cell level by a mechanism involving a random-event component that is intrinsic to the stem cell itself. Hemopoietic stem cells were identified by their ability to generate macroscopic-sized colonies having a visible erythroid component (i.e., gross red color) in standard methylcellulose assays containing medium conditioned by pokeweed mitogen-treated spleen cells and erythropoietin. In assays of replated primary or secondary colonies, inclusion of irradiated marrow-cell feeders was found to be an additional requirement. The mixed erythroid-megakaryocyte-granulocyte nature of colonies identified simply as macroscopic and erythroid was confirmed by cytochemical stains for lineage-specific markers. Marked variation in self-renewal was a feature of marrow stem cells both before and after maintenance in flask culture, although the overall self-renewal capacity exhibited by flask-cultured cells was approximately 5-fold higher. Variation in self-renewal was not correlated with primary colony size, which also varied over a wide range (0.2-9 X 10(5) nucleated cells per colony). Variation in stem cell self-renewal has been previously associated with hemopoietic stem cell proliferation in vivo. Its persistence in vitro in assays of dilute single-cell suspensions casts doubt on the significance of microenvironmental influences in directing stem cell differentiation.     

无血清培养胆囊癌GBC-SD细胞形成肿瘤细胞球的鉴定

目的:分离扩增肿瘤干细胞,并鉴定其生物学性质.方法:用无血清培齐基培养人胆囊癌GBC-SD细胞得到肿瘤细胞球.将肿瘤细胞球传代扩增,并用含血清培养基培养促使其分化;将肿瘤球和普通GBC-SD细胞分别种入96孔板,MTT检测增殖能力,并将肿瘤球和普通GBC-SD细胞分别植入裸鼠皮下,观察移植瘤的形成:流式细胞术检测CD15s和CD24在肿瘤球细胞和普通GBC-SD细胞中的表达,筛选细胞表面标志物.结果:在无血清培养基中,胆囊癌细胞可以形成少量的肿瘤细胞球,并显示很强的自我更新和增殖能力,含血清环境能够诱导其分化而贴壁生长;在动物实验中,肿瘤球细胞较普通GBC-SD细胞显示更强的致瘤能力(80.00%vs 10.00%,P<0.05);标志物CD15s在肿瘤球的表达较普通GBC-SD细胞明显增高(2.56%±0.38%vs 10.77%±0.93%,t=18.25,P<0.05).结论:人胆囊癌细胞GBC-SD的肿瘤干细胞可以通过无血清培养环境来分离和扩增,CD15s可能为其细胞表面标志物.