Stem cells

Thèmes abordés

Stem cells, zygote, sources, differentiation

Résumé du document

Presently, stem cells play an important part in the medical world.
It's recurrent to hear or read about new researches, discoveries or outstanding
accomplishment about stem cells.
Through this presentation we will see, successively, in a first part, the definition of stem cells:
what they are, their origin and what there are able to do.
In a second part we shall approach new discoveries and possible treatments using stem cells.
We will finish with the problems set by stem cells and their limits.

Extraits

[...] So in ideal conditions we could define stem cells as immortal. - Second, under specific conditions, stem cells may be induced to become and develop into specialized tissues and organs with special functions, like skin or muscle. In some organs, such as the bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. But in other organs, such as the pancreas and the heart, there is no pool of stem cells to renew the organ, so a damaged tissue in this part of the body will be catastrophic. [...]

[...] Stem cells could potentially be used to grow a particular type of tissue or organ. Utilisation of stem cells can generate new skin tissues that can be grafted on burnt victims. These cells have recently been directed to differentiate into specialized brain cells, so treatments are promising. Thus, transplanted stem cells and tissues may be used to treat brain disease such as Parkinson's and Alzheimer's by filling in damaged tissue Stem cells, which differentiate into healthy heart cells developed in a laboratory, may be transplanted into patients with heart disease, to regenerate the heart with healthy tissue. [...]

[...] That's why the body's immune system must be reduced to minimize the immune reaction set off by the transplanted cells. Presently the grown-up stem cells reveal more and more their possibilities and capacities. They will be able, one day, to replace the embryonic ones, because those require the taking of ovules, which is a procedure at risk for the health of the woman donor. Moreover the risk for the long-term physical health is still not well-known. It would thus be necessary to make more long-term studies. [...]

[...] (See added picture at the end: Annex Embryonic stem cells can be grown easier in culture than adult stem cells. Moreover, adult stem cells are rare in mature tissues, so isolating these cells from an adult tissue is challenging and methods to increase their numbers in-vitro have not yet been worked out. This is an important distinction, because therapies require a large number of cells, which is difficult to produce with adult stem cells. Another important differentiation between adult and embryonic stem cells is that adult cells and tissues derived from them are currently less likely to initiate rejection after transplantation. [...]

[...] Opposed to them, in contrast, some people think that life begin from a certain stage of gestational development, after the development of certain organs or after a certain time period. IIc) Limitation of the use of stem cells: In a cell therapy, many obstacles must be overcome to use the potential of stem cells: - first, a source of stem cells must be found. In general, embryonic and foetal stem cells are believed to be more versatile than tissue-specific stem cells. - second, stem cells need to be identified and isolated. Some environmental conditions must be respected to differentiate cells into specialized cells required for a particular therapy. [...]