What are stem cells and why are they important?
Stem cells have two important characteristics that distinguish them from other types of cells. First,
they are unspecialized cells that renew themselves for long periods through cell division. The second is
that under certain physiologic or experimental conditions, they can be induced1 to become cells with
special functions such as the beating cells of the heart muscle or the insulin-producing cells of the
Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells (look below)
and adult stem cells. ...Scientists discovered ways to obtain or derive stem cells from early mouse embryos more
than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery,
in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory.
These are called human embryonic stem cells. The embryos used in these studies were created for
infertility3 purposes through in vitro fertilization4 procedures and when they were no longer needed
for that purpose, they were donated for research with the informed consent of the donor.
Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called
a blastocyst5, stem cells in developing tissues give rise to the multiple specialized cell types that
make up the heart, lung, skin, and other tissues. In some adult tissues, such as bone marrow, muscle,
and brain, discrete populations of adult stem cells generate replacements for cells that are lost
through normal wear and tear, injury, or disease.
It has been hypothesized by scientists that stem cells may, at some point in the future, become the
basis for treating diseases such as Parkinson's disease, diabetes, and heart disease.
Scientists want to study stem cells in the laboratory so they can learn about their essential properties
and what makes them different from specialized cell types. As scientists learn more about stem cells, it
may become possible to use the cells not just in cell-based therapies, but also for screening6 new drugs
and toxins and understanding birth defects. However, as mentioned above, human embryonic stem cells have
only been studied since 1998. Therefore, in order to develop such treatments scientists are intensively
studying the fundamental properties of stem cells, which include:
1. determining precisely how stem cells remain unspecialized and self renewing for many years; and
2. identifying the signals that cause stem cells to become specialized cells.
Stem Cells for the Future Treatment of Parkinson's Disease
Parkinson's disease (PD) is a very common neurodegenerative disorder that affects more than 2% of the
population over 65 years of age. PD is caused by a progressive degeneration and loss of dopamine
(DA)-producing neurons, which leads to tremor, rigidity7, and hypokinesia (abnormally decreased
mobility). It is thought that PD may be the first disease to be amenable to8 treatment using stem
cell transplantation. Factors that support this notion include the knowledge of the specific cell
type (DA neurons) needed to relieve the symptoms of the disease. In addition, several laboratories
have been successful in developing methods to induce embryonic stem cells to differentiate into
cells with many of the functions of DA neurons.
In a recent study, scientists directed mouse embryonic stem cells to differentiate into DA neurons by
introducing the gene Nurr1. When transplanted into the brains of a rat model of PD, these stem
cell-derived DA neurons reinnervated the brains of the rat Parkinson model, released dopamine and
improved motor function.
Regarding human stem cell therapy, scientists are developing a number of strategies for producing
dopamine neurons from human stem cells in the laboratory for transplantation into humans with
Parkinson's disease. The successful generation of an unlimited supply of dopamine neurons could
make neurotransplantation widely available for Parkinson's patients at some point in the future.
C. 630 words
1. to induce - einleiten, erzeugen
2. pancreas - Bauchspeicheldrüse
3. infertility - Unfruchtbarkeit
4. in vitro fertilization - künstliche Befruchtung
5. blastocyst - Blastozyt, Keimbläschen
6. to screen - aussieben, überprüfen
7. rigidity - Steifheit
8. amenable to - zugänglich für
1. Which two types of stem cells are there?
2. If stem cells can be induced to become special cells, what practical application would they offer?
3. What can a 3-5-day-old embryo be used for?
4. What is it that scientists primarily want to learn about stem cells?
5. What makes the German government so sceptical of the research with human embryonic stemm cells?