Stem-cells are a population of undifferentiated cells which
are able
- to divide for indefinite period,
• to self-renew,
• to generate a functional progeny of highly specialized
cells.
These cells can be present anywhere in the body and divide in case of need. According to the capability of differentiation, they were named
• Totipotent (fertilized egg)—which can form all cell lines
including the placenta.
• Pluripotent (embryonic cell)—they can form most of the
cell lines except the placenta.
• Multipotent (e.g., hematopoietic)—they have limited
capacity to form one committed cell line such as blood
cells, skin, neurons, myocytes, and endothelial cells.