Stem cells

A stem cell is an undifferentiated cell capable of self-renewal, to differentiate into other cell types and proliferate in culture. Stem cells are derived either from the embryo or fetus, or adult tissues with or without transformation, they can also be obtained by nuclear transfer. Due to these properties, they can be used to regenerate or recreate the destroyed tissues : it is cellular therapy.

Stem cells are characterized by two main properties:

•           The ability to replicate in giving new stem cells. They share this property with cancer cells can multiply indefinitely;
•           The ability to transform sous une certaine pression chimique under some chemical pressure (in a given culture medium) to a differentiated mature cell: for example, a liver cell, pancreas, skin, etc..

Potentiality of stem cells :

All stem cells do not have the same potential of differentiation. Thus, we find :

Unipotent stem cell : able to provide only a single cell type (liver, skin, brain, etc..), but capable of self- regeneration, what distinguishes of precursor cells;

Multipotent stem cells : (fetal and adult cells) capable of giving born to multiple cell types, as myeloid stem cells of bone marrow which are at the origin of blood cells.

Pluripotent stem cells : (embryonic stem cells or induced pluripotent stem cells), derived from  an embryo from a 5 to 7 days or artificially obtained after transformation of adult cells, which may give born to more than 200 cell types representative of all body tissues ;

Totipotent stem cells : cells derived from the first divisions of the fertilized egg (until the fourth day), capable of giving born to all cell types of the body and the alone to allow full development of the individual.

embryonic stem cells