肿瘤干细胞及肝癌肿瘤干细胞

肿瘤干细胞理论认为只有存在于肿瘤中的少量干细胞性质的细胞群体对肿瘤发生和发展起着决定作用,肿瘤是由干细胞突变积累而形成的无限增殖的异常组织,这一理论的提出使人们对肿瘤发生机制的认识上升到了一个新的高度,也引起了研究者的广泛关注;肝癌是我国常见的恶性肿瘤之一,我国肝癌死亡率居世界之首,目前对肝癌的研究是我国恶性肿瘤防治的重点工作,现对当前肿瘤干细胞与肝癌肿瘤干细胞相关方面的最新研究进展作一概述。     

Fusion of Tumour Cells with Host Cells

THE A9 cell is an 8-azaguanine-resistant derivative of the L cell line¹. It lacks the enzyme inosinic acid pyrophosphorylase and is thus unable to grow in media such as HAT² in which endogenous synthesis of nucleic acid is blocked by aminopterin. The A9 line has little ability to grow progressively in vivo. Inocula of 5 × 10⁴ to 2 × 10⁶ cells produced progressive tumours in only 12% of X-irradiated newborn syngeneic C3H mice³. One of these tumours was explanted as a cell suspension into Eagle's minimal essential medium containing 15% foetal calf serum and then subcultivated in this medium with 5% foetal calf serum. At each passage, cells were inoculated into X-irradiated newborn syngeneic C3H or semi-allogeneic C3H×X F₁ mice (X designates a number of different allogeneic parents). Between 80 and 90% of the inoculated animals developed progressive tumours. The cell line was therefore designated A9HT (high take incidence). The karyotype of the A9HT line was found to be similar to that of the A9 line, but with a slightly reduced total chromosome number. The modal chromosome number of A9HT was about 53, compared with about 57 for A9 (see ref. 4). A9 and A9HT both had between 20 and 30 bi-armed chromosomes and a number of marker chromosomes in common. A detailed comparison of the karyotypes of the two lines examined by the quinacrine fluorescence technique has been made⁵. The A9HT line, like its A9 parent, lacks inosinic acid pyrophos-phorylase and is unable to grow in HAT medium.     

体细胞重编程逆转为干细胞的研究进展

目前细胞和发育生物学上的研究成果为生物医学研究提供了广泛的前景.将完全分化的细胞重编程,不经过胚胎逆转为多能干细胞状态,这点燃了再生医学应用的新希望,这一成果从法律、道德、伦理等不同方面被人们所接受.通过体细胞克隆胚胎获得干细胞所面临的破坏胚胎的伦理限制,促使研究者去寻求将分化细胞重编程逆转为干细胞的新方法.主要论述了体细胞重编程的原理、过程及不经过胚胎逆转为多能干细胞的方法.     

Place Cells,Grid Cells,and Memory

The hippocampal system is critical for storage and retrieval of declarative memories, including memories for locations and events that take place at those locations. Spatial memories place high demands on capacity. Memories must be distinct to be recalled without interference and encoding must be fast. Recent studies have indicated that hippocampal networks allow for fast storage of large quantities of uncorrelated spatial information. The aim of the this article is to review and discuss some of this work, taking as a starting point the discovery of multiple functionally specialized cell types of the hippocampal–entorhinal circuit, such as place, grid, and border cells. We will show that grid cells provide the hippocampus with a metric, as well as a putative mechanism for decorrelation of representations, that the formation of environment-specific place maps depends on mechanisms for long-term plasticity in the hippocampus, and that long-term spatiotemporal memory storage may depend on offline consolidation processes related to sharp-wave ripple activity in the hippocampus. The multitude of representations generated through interactions between a variety of functionally specialized cell types in the entorhinal–hippocampal circuit may be at the heart of the mechanism for declarative memory formation.The scientific study of human memory started with Herman Ebbinghaus, who initiated the quantitative investigation of associative memory processes as they take place (Ebbinghaus 1885). Ebbinghaus described the conditions that influence memory formation and he determined several basic principles of encoding and recall, such as the law of frequency and the effect of time on forgetting. With Ebbinghaus, higher mental functions were brought to the laboratory. In parallel with the human learning tradition that Ebbinghaus started, a new generation of experimental psychologists described the laws of associative learning in animals. With behaviorists like Pavlov, Watson, Hull, Skinner, and Tolman, a rigorous program for identifying the laws of animal learning was initiated. By the middle of the 20th century, a language for associative learning processes had been developed, and many of the fundamental relationships between environment and behavior had been described. What was completely missing, though, was an understanding of the neural activity underlying the formation of the memory. The behaviorists had deliberately shied away from physiological explanations because of the intangible nature of neural activity at that time.Then the climate began to change. Karl Lashley had shown that lesions in the cerebral cortex had predictable effects on behavior in animals (Lashley 1929, 1950), and Donald Hebb introduced concepts and ideas to account for complex brain functions at the neural circuit level, many of which have retained a place in modern neuroscience (Hebb 1949). Both Lashley and Hebb searched for the engram, but they found no specific locus for it. A significant turning point was reached when Scoville and Milner (1957) reported severe loss of memory in an epileptic patient, patient H.M., after bilateral surgical removal of the hippocampal formation and the surrounding medial temporal lobe areas. “After operation this young man could no longer recognize the hospital staff nor find his way to the bathroom, and he seemed to recall nothing of the day-to-day events of his hospital life.” This tragic misfortune inspired decades of research on the function of the hippocampus in memory. H.M.’s memory impairment could be reproduced in memory tasks in animals and studies of H.M., as well as laboratory animals, pointed to a critical role for the hippocampus in declarative memory—memory, which, in humans, can be consciously recalled and declared, such as memories of experiences and facts (Milner et al. 1968; Mishkin 1978; Cohen and Squire 1980; Squire 1992; Corkin 2002). What was missing from these early studies, however, was a way to address the neuronal mechanisms that led information to be stored as memory.The aim of this article is to show how studies of hippocampal neuronal activity during the past few decades have brought us to a point at which a mechanistic basis of memory formation is beginning to surface. An early landmark in this series of investigations was the discovery of place cells, cells that fire selectively at one or few locations in the environment. At first, these cells seemed to be part of the animal’s instantaneous representation of location, independent of memory, but gradually, over the course of several decades, it has become clear that place cells express current as well as past and future locations. In many ways, place cells can be used as readouts of the memories that are stored in the hippocampus. More recent work has also shown that place cells are part of a wider network of spatially modulated neurons, including grid, border, and head direction cells, each with distinct roles in the representation of space and spatial memory. In this article, we shall discuss potential mechanisms by which these cell types, particularly place and grid cells, in conjunction with synaptic plasticity, may form the basis of a mammalian system for fast high-capacity declarative memory.     

Dendritic Cells: Migratory Cells that are Attractive

Dendritic cells (DC) are professional antigen presenting cells, playing an important role in the initiation of T- and T cell dependent immune responses. DC are highly mobile cells and the sequential migration of DC in and out of tissues is accompanied by phenotypical as well as functional changes instrumental to their function as sentinels of the immune system. Herein, we will review recent progress in understanding the origin of DC, their migratory behaviour and their capacity to attract and interact with lymphocytes, with emphasis on the chemokine system.     

Oocyte-like Cells Induced from Mouse Spermatogonial Stem Cells

ABSTRACT: BACKGROUND: During normal development primordial germ cells (PGCs) derived from the epiblast are the precursors of spermatogonia and oogonia. In culture, PGCs can be induced to dedifferentiate to pluripotent embryonic germ (EG) cells in the presence of various growth factors. Several recent studies have now demonstrated that spermatogonial stem cells (SSCs) can also revert back to pluripotency as embryonic stem (ES)-like cells under certain culture conditions. However, the potential dedifferentiation of SSCs into PGCs or the potential generation of oocytes from SSCs has not been demonstrated before. RESULTS: We report that mouse male SSCs can be converted into oocyte-like cells in culture. These SSCs-derived oocytes (SSC-Oocs) were similar in size to normal mouse mature oocytes. They expressed oocyte-specific markers and give rise to embryos through parthenogenesis. Interestingly, the Y- and X-linked testis-specific genes in these SSC-Oocs were significantly down-regulated or turned off, while oocyte-specific X-linked genes were activated. The gene expression profile appeared to switch to that of the oocyte across the X chromosome. Furthermore, these oocyte-like cells lost paternal imprinting but acquired maternal imprinting. CONCLUSIONS: Our data demonstrate that SSCs might maintain the potential to be reprogrammed into oocytes with corresponding epigenetic reversals. This study provides not only further evidence for the remarkable plasticity of SSCs but also a potential system for dissecting molecular and epigenetic regulations in germ cell fate determination and imprinting establishment during gametogenesis.     

IDS Transfer from Overexpressing Cells to IDS-Deficient Cells

Iduronate sulfatase (IDS) is responsible for mucopolysaccharidosis type II, a rare recessive X-linked lysosomal storage disease. The aim of this work was to test the ability of overexpressing cells to transfer IDS to deficient cells. In the first part of our work, IDS processing steps were compared in fibroblasts, COS cells, and lymphoblastoid cell lines and shown to be identical: the two precursor forms (76 and 90 kDa) were processed by a series of intermediate forms to the 55- and 45-kDa mature polypeptides. Then IDS transfer to IDS-deficient cells was tested either by incubation with cell-free medium of overexpressing cells or by coculture. Endocytosis and coculture experiments between transfected Lβ and deleted fibroblasts showed that IDS transfer occurred preferentially by cell-to-cell contact as IDS precursors are poorly secreted by transfected Lβ. The 76- and 62-kDa IDS polypeptides transferred to deleted fibroblasts were correctly processed to the mature 55- and 45-kDa forms. Lβ were not able to internalize the 90-kDa phosphorylated precursor forms excreted in large amounts in the medium of overexpressing fibroblasts. Enzyme transfer occurred only by cell-to-cell contact, but the precursor forms transferred in Lβ after cell-to-cell contact were not processed. This absence of maturation was probably due to a mistargeting of IDS precursors in these cells.     

Dendritic Cells and Regulatory T Cells in Atherosclerosis

Although macrophages and other immune system cells, especially T cells, have been shown to play disease-promoting roles in atherosclerosis, less is known about the role of antigen presenting cells. Functional, immune stimulating dendritic cells (DCs) have recently been detected in aortic intima, the site of origin of atherosclerosis. We had compared DCs with macrophages in mice with experimental atherosclerosis, to clearly define cell types by developmental and functional criteria. This review summarizes recent advances in studies of DCs in humans and in mouse models of atherosclerosis, as well as providing a simple strategy to measure regulatory T (Treg) cells in the mouse aorta.     

Stem Cells

Russian Journal of Developmental Biology -     

Immobilized Cells

Three basic types of immobilization (i.e. without carrier, entrapment and immobilization on the carrier surface) of microbial cells, nonmicrobial cell populations and subcellular organelles are reviewed. These are further developed into a number of combined and less frequently used techniques of immobilization and application of cell biocatalysts for industrial biotransformations in pharmacy, food industry and agriculture, including novel approached and some unpublished authors’ results.     

种子细胞——组织工程连载之三

种子细胞也是组织工程的核心研究内容,获得足够数量和质量的种子细胞是开展体外组织工程的必要基础。用于组织工程的种子细胞必须具有形成新组织结构的能力,主要来源于自体、同种异体或异种,在具体应用时各有利弊。一些成体干细胞由于不存在伦理争议以及发育分化条件相对简单等优势是重要的种子细胞,包括造血干细胞、骨髓干细胞、神经干细胞、脂肪干细胞、皮肤干细胞。人胚胎干细胞及其组织工程要真正在临床医学中得到应用,还有很长的一段路要走。其他一些细胞也可以作为组织工程种子细胞,包括内皮细胞、上皮细胞、成纤维细胞、骨细胞、成骨细胞、角质细胞、前脂肪细胞、脂肪细胞、肌腱细胞等。这些细胞已分化,分裂能力有限,但仍应用于组织工程。理想的种子细胞具有一定标准。     

Increased Lysis of Stem Cells but Not Their Differentiated Cells by Natural Killer Cells; De-Differentiation or Reprogramming Activates NK Cells

The aims of this study are to demonstrate the increased lysis of stem cells but not their differentiated counterparts by the NK cells and to determine whether disturbance in cell differentiation is a cause for increased sensitivity to NK cell mediated cytotoxicity. Increased cytotoxicity and augmented secretion of IFN-γ were both observed when PBMCs or NK cells were co-incubated with primary UCLA oral squamous carcinoma stem cells (UCLA-OSCSCs) when compared to differentiated UCLA oral squamous carcinoma cells (UCLA-OSCCs). In addition, human embryonic stem cells (hESCs) were also lysed greatly by the NK cells. Moreover, NK cells were found to lyse human Mesenchymal Stem Cells (hMSCs), human dental pulp stem cells (hDPSCs) and human induced pluripotent stem cells (hiPSCs) significantly more than their differentiated counterparts or parental lines from which they were derived. It was also found that inhibition of differentiation or reversion of cells to a less-differentiated phenotype by blocking NFκB or targeted knock down of COX2 in monocytes significantly augmented NK cell cytotoxicity and secretion of IFN-γ. Taken together, these results suggest that stem cells are significant targets of the NK cell cytotoxicity. However, to support differentiation of a subset of tumor or healthy untransformed primary stem cells, NK cells may be required to lyse a number of stem cells and/or those which are either defective or incapable of full differentiation in order to lose their cytotoxic function and gain the ability to secrete cytokines (split anergy). Therefore, patients with cancer may benefit from repeated allogeneic NK cell transplantation for specific elimination of cancer stem cells.     

树突细胞联合细胞因子诱导的杀伤细胞对急性白血病细胞的体外杀伤作用

目的:研究细胞因子诱导的杀伤细胞(CIK)与同源树突状细胞(DC)共培养后CIK细胞的表型、增殖活性的变化,及抗急性白血病细胞活性.方法:正常人外周血单个核细胞诱导DC和CIK细胞,将DC与CIK共培养,以CIK细胞单独培养为对照.用台盼蓝活细胞计数计算细胞扩增倍数,MTT法测定杀伤活性,流式细胞术分析免疫表型.结果:DC-CIK细胞增殖能力明显高于CIK细胞(P＜0.05); DC、CIK细胞共培养后,CD3+ CD8+、CD3+ CD56+双阳性细胞比率较同条件下CIK细胞组显著增多(P＜0.05);在2.5∶1-20∶1的效靶比范围内,DC-CIK共培养物对AML细胞的杀伤率显著高于CIK细胞(P＜0.05),且杀伤率与效靶比呈正相关.结论:DC-CIK细胞的增殖能力、对AML细胞的杀伤活性均高于CIK细胞,为DC-CIK细胞免疫治疗提供了实验和理论依据.