免疫学论文(全英文)

The Researching of Embryonic Stem Cells

Summary : Embryonic stem cells have the value of

significant biological basis research and medical . Research on embryonic stem cells originated from the 1970s, the current research focus on the characteristics and clinical application of the basic biology of embryonic stem cells. At the same time, there are also many of the issue of embryonic stem cell research.

Keywords: Embryonic stem cells, concepts, applications, problems

The basic concept of Stem Cells

Definitions

Stem cells with the ability to self-replicate, under certain conditions,it can differentiate into various functional cells.

Classification

Totipotent stem cells Including embryonic stem cells , germline stem cells. they can differentiate into the systemic 200 variety of cell types, and further form any of the body's tissues and organs, and with the ability to develop into a complete individual.

Pluripotent stem cells,which have the potential to differentiate into a variety of cells and tissues, but such cells have lost the ability to develop into a complete individual.

Designed pluripotent stem cells, Such cells only to one or more closely related to the two types of cell differentiation.

The source of stem cells

The source of stem cells may have four sources: ① the separation of the inner cell mass cells from the well-developed blastocysts, such as fibroblast feeder cells co-cultured so that the proliferation of embryonic stem cells. ② from 5 to 9 weeks of embryonic gonads isolated human embryonic stem cells. The ③ obtained from malignant of embryonic tumors or teratomas cells. ④ reproductive cloning (therapeutic cloning) by somatic cell nuclear transfer (SCNT), the egg is about to go nuclear transplantation into another somatic cell nuclear cloning so that the formation of the blastocyst, and then separation of the inner cell mass, embryonic stem cells.

The applications of ES cell

For the production of transgenic animals and cloning of animals

The use of ES cells as a vector, in vitro transformation of ES cells, so that the number of gene integration loci, the degree of expression and stability of the inserted gene and screening and so on at the cellular level, thereby obtaining a stable, satisfactory transgenic ES cell lines, production of transgenic animals. Nuclear transfer ES cell donor nucleus in the short term, the availability of a large number of genotype and phenotype identical individuals. This method is superior to the somatic cell cloned animals, but the latter is the success rate of cloning animals, prone to severe immune defects and mutations (French Agricultural Research Institute, said 90% of cloned cattle not grow normally). Mouse embryonic stem cells can produce sperm, egg, and successful fertilization can even bred laboratory egg from the female and male cells, to promote the study of reproductive and cloning.

For developmental biology research

Early mammalian embryo small volume, but also in the uterus, in order to study cell

differentiation in vivo and its mechanism is almost impossible, and stem cells, especially ES cells have unique developmental pluripotency, in particular in vitro culture conditions and under the joint action of the inducing agent after a certain precursor cell stage, to differentiate into nerve, muscle, cartilage, blood cells, epithelial cells and fibroblasts, ES cells is the study of a particular type of cell differentiation model to explore certain precursors cell origin and cell lineage evolved the ideal experimental system. Application of gene chip biotechnology, cell gene transcription and expression of comparing ES cells at different developmental stages, not only to determine the molecular mechanisms of embryonic development and cell differentiation, but also found a new gene.

for new drug research and tissue and organ repair, treatment, research

ES cells provide the research tools of the new drug's pharmacology, toxicology and drug metabolism at the cellular level, both to reduce the number of animals required drug experiments, but also easy to find effective and lasting treatment. No matter the tissues and organs of autologous or allogeneic transplantation to repair the defect, are limited by objective conditions, in particular the lack of sources of seed cells. Now , the birth and development of stem cell engineering, tissue and organ transplantation research has entered a new stage, is expected to solve the above problems. It has been reported that mouse ES cells under special conditions to differentiate into osteoblasts and tissue engineering, the formation of bone tissue may be used in bone repair.

It has been

demonstrated that cells derived from the ES cell has been able to or may treat many diseases, the treatment of heart disease such as myocardial cells, leukocytes treat leukemia, pancreatic islet cells to treat diabetes, liver cells, the treatment of hepatitis, the treatment of osteoarthritis of the cartilage cells, skin cells treated burns and trauma, the treatment of osteoporosis, bone cells, nerve cells in the treatment of Parkinson's disease. The problems of ES cell studies

The biggest limitation is that the ethical problems of embryonic stem cell research.

Whether human embryonic stem cells must destroy embryos? Whether they would artificially created embryos in order to obtain stem cells more? Fact, scientists are actively working to overcome these difficulties. For example, human eggs for materials produced by chemical stimulation parthenogenetic development for the embryo. Such embryos do not develop into the individuals obtained in this way (due to lack of paternal chromosomes), embryonic stem cells can circumvent ethical problems. There are scientists using genetic modification techniques to create not mouse embryos in the uterus, can obtain embryonic stem cells from such embryos.

Immune rejection and biosafety issues

Embryonic stem cells will be applied to the clinical, there are two major obstacles

Not overcome. The first is immune rejection. Because embryonic stem cells are not from the patients themselves, it must be subject to the patient's immune system attacks. Scientists now think by nuclear transplantation of the patient to go nuclear eggs to solve the problem of immune rejection, but no exact success reported. This nuclear transfer technology faces more ethical issues and technical problems, once the breakthrough will produce revolutionary results. The second obstacle is the biological safety of embryonic stem cells. Currently established human embryonic stem cell lines mostly use animal

products as nutrients, these animal products may bring a viral infection, such as a series of complex issues, if hastily applied to the human body is irresponsible.

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