Stem Cells – The Source of All Cell
Types and Tissues
Stem cells are an essential component of the body’s regenerative process, providing
replacement cells to a variety of tissues and organs butterfieldgrain, including blood, muscle, skin,
and brain. These cells can be derived from embryos, adult tissue, or a variety of
other sources and are found in both healthy adults and those with diseases.
Embryonic stem cells are stem cells derived from the inner cell mass of a
mammalian embryo (called a blastocyst) at a very early stage in development.
These cells are the source of all specialized cell types and tissues that develop in the
developing organism.
They are the source of all specialized blood-forming cells that give rise to red and
white blood cells in bone marrow. They also give rise to all specialized skin cells,
sperm and eggs.
Many other specialized tissues and organs are derived from embryonic stem cells in
adult animals, such as the heart, skin, and lungs. Researchers have used these cells
to produce therapies for a wide range of diseases and disorders, from cancer to
spinal cord injury.
Research on human embryonic stem cells has led to early-stage clinical trials that
have tested a number of different therapies for conditions such as Parkinson disease
and heart failure. The FDA approved the first stem cell-based therapy in 2009, called
GRNOPC1, for the restoration of nerve function in people with acute spinal cord
injuries.
Scientists also have discovered that stem cells can be derived from the amniotic
fluid and umbilical cord blood of pregnant women, a discovery that is helping to
understand how human birth occurs. These stem cells have the ability to change
into specialized cells that form the heart, intestines, and nervous system of the
fetus.
A pluripotent stem cell is a cell that has the ability to differentiate into any cell type
within the body. This differentiation process involves several steps that result in the
formation of a specific tissue-specific cell. It is triggered by signals that the cell
receives from surrounding cells, its microenvironment, and certain molecules in the
cells themselves.
Some of these signals may be induced by growth factors or by other signals, such as
physical contact with neighboring cells. Regardless of which type of signal is
triggered, the end result is the same: the stem cell differentiates into a specialized
cell.
Although scientists are learning more about how and when stem cells become
specialized, there is still much to learn. This is because some of the cells that
differentiate are genetically mutated, resulting in defective or abnormal tissue.
Reprogramming of adult cells to assume a pluripotent stem cell-like state is an
emerging technique that could help reduce the ethical concerns that arise with using
embryonic stem cells, especially since these reprogrammed cells will not be rejected
by the recipient’s immune system. This technique is called induced pluripotent stem
cells (iPSCs).
Although these studies are still in early stages, they provide hope for the future of
therapeutics based on the ability to use stem cells in ways that will improve human
health. As with any medical treatment, however, make sure you understand the
science behind a particular therapy before you decide to participate in it.