What are stem cells?
The body of each person consists of different cells. Some of these cells are specialised, others are undifferentiated. The undifferentiated cells, that can produce specialised cells, are called stem cells. There are many different types of stem cells but they all have some features in common:
- Stem cells are not differentiated but are capable of differentiating into specialized cell types.
- If stem cells divide, the daughter cells can either become stem cells or they can turn into specific cell types, e.g. muscle cells, nerve cells, blood cells, bone cells etc.
Stem cells have the ability to either change into a multitude of different cell types (pluripotency) or only into cells that belong to one closely related family of cells (multipotency). The two most known kinds of stem cells are pluripotent embryonic stem cells on the one hand and multipotent adult stem cells on the other hand.
- If stem cells divide, the daughter cells can either become stem cells or they can turn into specific cell types, e.g. muscle cells, nerve cells, blood cells, bone cells etc.
Pros and cons of stem cell research
Scientists aim at using stem cells to grow specific cells, tissues and even entire organs in the laboratory, so that defective organs or cells could be replaced. This could lead to treatments and cures for diseases like Parkinson, diabetes or hearth diseases - but before these visions can be used in day to day medical practice, more research must be carried out This is because embryogenic stem cells may change into unwanted cells: for example cancer cells or instead of forming vessel cells they could form bits of bone in hearts that they are supposed to be repairing. Opponents of stem cell research have also ethical and moral objections: they say that human life gets killed for science, as researchers sometimes destroy embryos to obtain stem cells. That is why more research is done into adult stem cells that are found for example in the bone marrow and are not subject to so much controversy.
Current stem cell therapy
Currently, only bone marrow stem cells are used for routine therapy. They are applied in the treatment of various blood diseases (e.g. leukemia) or heart attacks. The stem cells are extracted from the bone marrow, purified and subsequently injected in the coronary vessels. There, they stimulate the generation of new vessels and prevent more cardiac muscle cells from dying. In addition, various studies have shown that new forms of therapy, some using other types of adult stem cells, have been proven effective.
Novel research
As the usage of embryonic stem cells is limited in most countries, scientists try to take other adult cells, for example skin or fat cells, and turn them into cells that are undifferentiated and can create most kinds of cells. These cells are called (protein) induced pluripotent stem cells ((p)iPS) and are very similar to embryonic stem cells. But there are still problems when using pluripotent stem cells as it is difficult to make sure that these cells differentiate into the needed cell type. So further research is needed to better understand the differentiation process.
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