Male germ line stem cells: from cell biology to cell therapy

Research using stem cells has several applications in basic biology and clinical medicine. Recent advances in the establishment of male germ line stem cells provided researchers with the ability to identify, isolate, maintain, expand and differentiate the spermatogonia, the primitive male germ cells, as cell lines under in vitro conditions. The ability to culture and manipulate stem cell lines from male germ cells has gradually facilitated research into spermatogenesis and male infertility, to an extent beyond that facilitated by the use of somatic stem cells. After the introduction of exogenous genes, the spermatogonial cells can be transplanted into the seminiferous tubules of recipients, where the transplanted cells can contribute to the offspring. The present review concentrates on the origin, life cycle and establishment of stem cell lines from male germ cells, as well as the current status of transplantation techniques and the application of spermatogonial stem cell lines.     

The Primate Embryo Gene Expression Resource in embryology and stem cell biology

The analysis of temporal patterns of gene expression in embryos is an essential component of any research program seeking to understand molecular mechanisms that control development. Little is known of early regulatory mechanisms that operate in primate oocytes and preimplantation-stage embryos. Such studies have been hindered by the cost of obtaining, and limited availability of, non-human primate oocytes and embryos, and by ethical and legal constraints on studies of human embryos. Over the past 4 years we have established the Primate Embryo Gene Expression Resource (PREGER) to circumvent these limitations. A set of over 200 samples of rhesus monkey oocytes and embryos has been converted to cDNA libraries, which are, in turn, used for a variety of molecular analyses. Both the libraries and cDNA dot blots can be distributed free of charge to anyone wishing to study gene expression at these stages. This includes providing an inexpensive and rapid method for confirming and extending results of gene discovery approaches such as microarray analysis. PREGER includes an on-line resource with a database and other useful tools for embryologists. The resource is being expanded to incorporate samples from other species and from embryonic stem cells.     

Mesenchymal stem cell; history, biology and clinical application

In the last years, stem cells have drawn the attention of various sectors of society for many reasons. From the basic point of view, stem cells represent an ideal model to study cell differentiation and self-renewal mechanisms. However, their potential in cell therapy and regenerative medicine has triggered the increasing amount of knowledge in this area. Mesenchymal stem cells belong to the select group of adult stem cells. They have differentiation potential towards mesenchymal tissues such as bone, cartilage, stroma and fat. Recently, both in vivo and in vitro reports have shown a greater plasticity of mesenchymal stem cells, showing not only a mesenchymal cell fate but also those leading to endothelial, nervous and muscular lineages. For these reasons, the study of mesenchymal stem cells has gained great interest and many articles have been published. In the present review, we have presented a global vision of this topic, including its history, biologic features, sources, isolation methods and an overview on their clinical application.     

Influence of polyunsaturated fatty acids and their metabolites on stem cell biology

Proinflammatory cytokines and essential fatty acids (EFAs) and their metabolites are altered in coronary heart disease, stroke, diabetes mellitus, hypertension, cancer, depression, schizophrenia, Alzheimer's disease, and collagen vascular diseases, indicating that these diseases not only are low-grade systemic inflammatory conditions but also have defects in the metabolism of EFAs. EFAs and their metabolites such as eicosanoids, lipoxins, resolvins, protectins, maresins, and nitrolipids are biologically active molecules that regulate gene expression and enzyme activity, modulate inflammation, the immune response, and gluconeogenesis by direct and indirect pathways, function directly as agonists of a number of G-protein-coupled receptors, and thus regulate several cellular processes. EFAs and their metabolites activate phosphatidylinositol 3-kinase/murine thymoma viral oncogene homolog 1 (Akt) and p44/42 mitogen-activated protein kinases and stimulate gluconeogenesis and cell proliferation by Ca²⁺, phospholipase C/protein kinase, events that are also necessary for stem cell proliferation. Stem cells are pluripotent and expected to be of benefit in the management of many clinical conditions. Therefore, I propose that the beneficial actions of EFAs and their metabolites seen in coronary heart disease, stroke, diabetes mellitus, hypertension, atherosclerosis, cancer, depression, schizophrenia, Alzheimer's disease, and collagen vascular diseases could be ascribed to their ability to enhance the proliferation and differentiation of embryonic stem cells in addition to their capacity to suppress inflammation.     

Barriers in contribution of human mesenchymal stem cells to murine muscle regeneration

AIM: To study regeneration of damaged human and murine muscle implants and the contribution of added xenogeneic mesenchymal stem cells(MSCs).METHODS: Minced human or mouse skeletal muscle tissues were implanted together with human or mouse MSCs subcutaneously on the back of non-obese diabetic/severe combined immunodeficient mice. The muscle tissues(both human and murine) were minced with scalpels into small pieces( 1 mm3) and aliquoted in portions of 200 mm3. These portions were either cryopreserved in 10% dimethylsulfoxide or freshly implanted. Syngeneic or xenogeneic MSCs were added to the minced muscles directly before implantation. Implants were collected at 7, 14, 30 or 45 d after transplantation and processed for(immuno)histological analysis. The progression of muscle regeneration was assessed using a standard histological staining(hematoxylin-phloxinsaffron). Antibodies recognizing Pax7 and von Willebrand factor were used to detect the presence of satellite cells and blood vessels, respectively. To enable detection of the bone marrow-derived MSCs or their derivatives we used MSCs previously transduced with lentiviral vectors expressing a cytoplasmic LacZ gene. X-gal staining of the fixed tissues was used to detect β-galactosidase-positive cells and myofibers.RESULTS: Myoregeneration in implants of fresh murine muscle was evident as early as day 7, and progressed with time to occupy 50% to 70% of the implants. Regeneration of fresh human muscle was slower. These observations of fresh muscle implants were in contrast to the regeneration of cryopreserved murine muscle that proceeded similarly to that of fresh tissue except for day 45(P 0.05). Cryopreserved human muscle showed minimal regeneration, suggesting that the freezing procedure was detrimental to human satellite cells. In fresh and cryopreserved mouse muscle supplemented with LacZ-tagged mouse MSCs, β-galactosidase-positive myofibers were identified early after grafting at the wellvascularized periphery of the implants. The contribution of human MSCs to murine myofiber formation was, however, restricted to the cryopreserved mouse muscle implants. This suggests that fresh murine muscle tissue provides a suboptimal environment for maintenance of human MSCs. A detailed analysis of the histological sections of the various muscle implants revealed the presence of cellular structures with a deviating morphology. Additional stainings with alizarin red and alcian blue showed myofiber calcification in 50 of 66 human muscle implants, and encapsulated cartilage in 10 of 81 of murine muscle implants, respectively.CONCLUSION: In mouse models the engagement of human MSCs in myoregeneration might be underestimated. Furthermore, our model permits the dissection of speciesspecific factors in the microenvironment.     

The AHEC contribution to social work education

The Area Health Education Center (AHEC) Program is a Federal initiative funded by the Public Health Service. The goal of the program is to improve the distribution and quality of training for health professionals. Funds are awarded to schools of medicine or osteopathy which in turn subcontract with at least two other health professional schools. Each project recipient must establish an AHEC center to plan and coordinate community-based educational experiences for health professions students in designated health shortage areas. The AHEC program fosters interdisciplinary training among health professionals. As part of the basic program thrust, some AHECs have included the social work profession in their program design. The Massachusetts AHEC, through Boston University's School of Social Work, established a health care concentration and interdisciplinary rotation that included students from social work, psychology, nursing, and medicine. Other examples of AHEC-sponsored training are presented from Baltimore, the eastern shore of Virginia, and several centers in Massachusetts. Through the AHEC training mechanism, social work students as well as practitioners in the field have the opportunity to encounter the most current and urgent issues in health care practice.     

The contribution of benzene to smoking-induced leukemia

Cigarette smoking is associated with an increased risk of leukemia; benzene, an established leukemogen, is present in cigarette smoke. By combining epidemiologic data on the health effects of smoking with risk assessment techniques for low-dose extrapolation, we assessed the proportion of smoking-induced total leukemia and acute myeloid leukemia (AML) attributable to the benzene in cigarette smoke. We fit both linear and quadratic models to data from two benzene-exposed occupational cohorts to estimate the leukemogenic potency of benzene. Using multiple-decrement life tables, we calculated lifetime risks of total leukemia and AML deaths for never, light, and heavy smokers. We repeated these calculations, removing the effect of benzene in cigarettes based on the estimated potencies. From these life tables we determined smoking-attributable risks and benzene-attributable risks. The ratio of the latter to the former constitutes the proportion of smoking-induced cases attributable to benzene. Based on linear potency models, the benzene in cigarette smoke contributed from 8 to 48% of smoking-induced total leukemia deaths [95% upper confidence limit (UCL), 20-66%], and from 12 to 58% of smoking-induced AML deaths (95% UCL, 19-121%). The inclusion of a quadratic term yielded results that were comparable; however, potency models with only quadratic terms resulted in much lower attributable fractions--all < 1%. Thus, benzene is estimated to be responsible for approximately one-tenth to one-half of smoking-induced total leukemia mortality and up to three-fifths of smoking-related AML mortality. In contrast to theoretical arguments that linear models substantially overestimate low-dose risk, linear extrapolations from empirical data over a dose range of 10- to 100-fold resulted in plausible predictions.     

The contribution of 'story' to children's development

Story plays an essential part in the growth and development of the mind and all that it contains. It gives insights into human nature, expression to thoughts, ideas and desires and aids in the organisation of experience. It opens up the possibilities of other ways of life, of new and different approaches and views in human relationships. New worlds we didn't know existed are created and familiar worlds are given new structures, put into new frameworks and we are given a deeper understanding of our own, and others', intentions, attitudes and emotions.

Reading the following article in the light of the power of story, we find that narrative in the form of books becomes an important part of learning and ultimately in shaping lives and society. Writers, parents and teachers, therefore, should consider the values presented in books, whether implicit or explicit, and be able to justify what they offer to children in the form of literature.

This article was written with the intention of showing the importance of narrative in the development of young minds. It considers the responses we can make to literature and how this may determine the shape of our thinking. Tracing the history of children's books and the social pressures exerted on them, we see the importance placed on the values that are presented. In the light of the power of story, we see the important part books play in influencing individual lives, and the responsibility of adults in what they offer to children.     

The nutritional contribution to bovine spongiform encephalopathy

Evidence that changes in feeding style alter the membrane fatty acid composition of ruminant tissue is presented here by comparing zoo giraffe with the same species from their natural habitat. The membrane changes seen are similar to those used experimentally to make animals susceptible to basic brain protein and encephalomalacia. Similar membrane responses have been noted in cattle. Use of animal protein and increased nitrogen in cattle feeds would lead to a relative deficiency of essential fatty acids in the cell membranes and hence reduced membrane stability. By analogy with crazy chick disease (nutritional encephalomalacia) and experimental encephalomyelitis in rats, the possibility that the changes in animals feeds would have depleted cattle tissue membranes and made them susceptible to BSE is discussed. The assumption being made is that the principle of a requirement of essential fatty acids for neural integrity and immune system function would apply to cattle as well as to other species.     

The ethical challenge of stem cell research.

This article analyzes the ethical issues raised by embryonic stem cell research and recent recommendations by the National Bioethics Advisory Commission (NBAC) regarding federal support for this research. The authors identify the key ethical issue as the moral significance that should be granted to early embryos and discuss arguments supporting the diverse answers to that question and the implications each view has on the formulation of rules and policies for stem cell research. The authors conclude that several of NBAC's recommendations regarding the derivation of stem cells from embryos for research are ethically justifiable and sound public policy.     

干细胞专利技术现状研究

目的了解国内、外干细胞相关专利的情况，为更好地应用知识产权对我国干细胞技术领域的研究成果进行保护提供合理化建议。方法根据干细胞研究专业术语确定相关主题词，以德文特（Derwent）数据库为背景，对多个专利数据库进行检索、筛查和分类，建立干细胞专利数据库。从专利的角度人手，对数据库中的2571篇国际及228篇国内干细胞专利文献进行分类分析。结果干细胞研究领域的专利申请情况总体呈上升趋势；早期专利申请主要涉及遗传工程中的DNA或RNA、载体、宿主等方面，随着研究的发展，涉及人或动物细胞或组织的专利申请逐渐增多，1998年后涉及人类细胞或组织的专利申请数量有了大幅增加，但目前仍以动物源性的细胞或组织为主（15．9％）；国内2001年以后申请的专利集中在人或动物来源的细胞或组织方面，以涉及人源细胞或组织的占首位（28．1％）。结论国内外干细胞相关专利现状的分析表明，国内在干细胞研究方面存在一定优势，应从多角度应用知识产权对研究成果进行保护。