Biomedical Engineering Reference
In-Depth Information
Chapter 2
Stem Cell Concept: Entity or Function?
The ignorance, the root of every evil.
Plato
Stem cells derive from different sources:
Embryonic tissues
Fetal tissues
Cord blood
Adult tissues (different kind throughout the body)
They have the unique ability of self-renewal and plasticity, e.g., to multiply for a
long time without a change and to produce cells that differentiate into specialized
structures. New stem cells can be created to replenish stem cell population.
Genes that regulate these two distinct mechanisms are recently discovered:
1. The key gene that initiates the signaling process that instructs a stem cell to
renew itself instead of differentiating into another type of cell is found in the
model of drosophila (Erika Matunis and Natalia Tulina, from Department of
Embryology at the Carnegie Institution in Washington-Science) [
1
] .
2. The cascade of signals that start with the JAK-STAT signaling pathway where
unpaired genes called Upd expressed in hub cells activating this cascade. When
the pathway is activated, the STAT transcription factor—gene that controls the
transcription of other genes—binds to target genes to change the cell's pattern of
gene expression and help the cell to self-renew [
2
] .
Depending on their origin they have varying capacity to multiply and differentiate
from other cell types. It is not possible at present to predict which types of cells will
be best suitable for various therapeutic situations. Embryonic stem cells are derived
from pre-embryos at the blastocyst stage and may give rise to all bodily tissues and
cells (have been shown capable of differentiating into all the different tissues and cell
types of the body, and therefore have the highest, totipotent potential).
