![]() In recent years, science has discovered new types of adult stem cells in tissues in which no stem cells had previously been suspected. If, for instance, the skin is injured by a cut or burn, the skin stem cells there are activated and form new skin cells through division and differentiation. It is now assumed that adult stem cells occur in all tissues of the human body and can regenerate it, for example in the case of injury. they are usually only able to form cells of a certain cotyledon (cf. Multipotent stem cells can develop into different cell types for a certaintissue, i.e. This ability is known as multipotency (Latin: more than one ability). For example, skin stem cells can only produce different cell types of the skin, but not blood or nerve cells. Further information on cell nuclear transfer can be found on the website of the German Reference Centre for Ethics in the Life Sciences (DRZE).įigure 2 and 3 were kindly provided by the German Reference Centre for Ethics in the Life Sciences (DRZE).Īdult stem cells (also known as somatic or tissue stem cells) are already specialized stem cells that can only form certain cell types of the human body. The method has so far only been used on animal cells. The cells obtained by this method are also pluripotent. In the case of a donated egg cell, the cell nucleus is removed and the nucleus of a somatic cell is used instead. However, it is possible to import hES cells from other countries for research purposes under strict conditions.Īnother way of producing embryonic stem cells is what is known as therapeutic cloning, which is based on somatic cell nuclear transfer (SCNT). In Germany, the production of hES cells in the laboratory is prohibited. ![]() In order to produce hES cells, blastocysts are usually used that have been produced for artificial insemination (in vitro fertilization) but are no longer used for implantation. In addition, the cells can be multiplied in the laboratory and kept in cell culture. This is called differentiation (see Figure 4). nerve cells, from embryonic stem cells by adding certain growth factors. In the laboratory, it is possible to produce certain cell types, e.g. Research is carried out worldwide with both animal and human embryonic stem cells (hES cells). They are, therefore, not yet fixed to a specific tissue type (see Figure 4). Pluripotent stem cells are characterized by the ability to produce all three cotyledons (ectoderm, endoderm, mesoderm). This characteristic is called pluripotency (Latin: many abilities) in contrast to the totipotent, single-cell embryos (=originating cell), which are always at the very beginning of individual development. the isolated cells, has the potential to develop under controlled conditions into any cell type of the human body, but the embryonic stem cells can no longer form a complete organism. In order to obtain embryonic stem cells, the outer cell layer of the blastocyst must be destroyed so that the remaining cells of the inner cell mass (embryoblast) can be isolated and converted into cell cultures in the laboratory (see Figure 3). At this early stage, no organs have been formed, it is merely a kind of cell cluster (see Figure 2). This is a developmental stage that a human embryo goes through on the 5 thday after fertilization. They only occur at a very early stage of embryonic development, the blastocyst. Embryonic stem cells (ES cells) are not found in the adult body.
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