Stem Cell Research- A Magical Cure
By: Priyanka Shetty
What are stem cells?
Stem
cells are one of the most fascinating areas of biology. This promising area of
science is leading scientists to investigate the possibility of cell-based
therapies to treat disease. Cells are the structural and functional units of
all living organism. Stem cells differ from other cells in the body in three
main ways. Stem cells are unspecialized. They have not developed into cells
that perform a special function. Unspecialized stem cells have the ability to
renew themselves for long periods of time by cell division. Stem cells can differentiate, which means they can
divide and produce mature cells that have the potential to become other, more
specialized cell types or tissues, such as heart cells, skin cells or nerve
cells. These new cells and tissues are used to repair or replace damaged or
diseased cells in the body. These unique characteristics are why stem cell
research holds such great promise for the treatment of life-threatening
diseases.
Categories of Stem Cells
There are
many types of stem cells but the two most important are embryonic stem cells
and adult stem cells. Embryonic stem
cells come from a four to five-day-old embryo. They have the ability to
form virtually into any type of cell found in the human body, but are not
capable of developing into a whole new organism. These are considered the most
valuable stem cells.
Adult stem cells are more specialized than embryonic stem cells. They have a restricted
ability to produce different cell types and to self-renew. Adult stem cells are
rare. Their primary functions are to maintain the steady state functioning of a
cell—called homeostasis—and, with limitations, to replace cells that die
because of injury or disease. Furthermore, adult stem cells are dispersed in
tissues throughout the mature human and behave very differently, depending on
their local environment.
Unlike
embryonic stem cells, which are defined by their origin (the inner cell mass of
the blastocyst), adult stem cells share no such definitive means of
characterization. In fact, no one knows the origin of adult stem cells in any
mature tissue. Most of the information about adult stem cells comes from
studies of mice. The list of adult tissues reported to contain stem cells is
growing and includes bone marrow, peripheral blood, brain, spinal cord, dental
pulp, blood vessels, skeletal muscle, epithelia of the skin and digestive
system, cornea, retina, liver, and pancreas.
Another
important stem cell is a hematopoietic (blood forming) stem cell. These cells
give rise to all the types of blood cells. Blood cells are responsible for
constant maintenance and immune protection of every cell type of the body. This
relentless and brutal work requires that blood cells, along with skin cells,
have the greatest powers of self-renewal of any adult tissue. Mesenchymal stem
cells can transform into bone, cartilage, fat and connective tissue. Umbilical
cord stem cells have been used in the treatment of blood diseases, such as
leukemia. Neural stem cells can give rise to nerve cells and two categories of
non-neuronal cells.
Stem cells can also be classified by the extent to
which they can differentiate into different cell types:
Totipotent
Stem Cells- are
cells that are capable of forming a completely new embryo, which can develop
into a new organism. A fertilized egg cell is totipotent as it has the
potential to develop into a new organism.
Pluripotent
Stem Cells- can
differentiate into any cell type in the adult organism, except for totipotent
stem cells and the cells of the placenta. Embryonic stem cells and embryonic
germ cells are pluripotent.
Multipotent
Stem Cells- are
stem cells that only have the potential to make a few cell types in the body.
Adult stem cells are multipotent.
Unipotent
Stem Cells- are
stem cells that self-renew as well as give rise to a single mature cell type.
Pros of Stem Cell Research
There are
many ways in which human stem cells can be used in basic and clinical research.
Studies of human embryonic stem cells can give scientists information about the
complex events that occur during human developments. Scientists already found
out that some of the most serious medical conditions such as cancer and birth
defects are due to abnormal cell division and differentiation. Differentiation
is the normal process through which cells mature so they can carry out the jobs
they were meant to do. Human stem cells could also be used to test new drugs.
Cancer cell lines, for example, are used to screen potential anti-tumor drugs.
Perhaps
the most important potential application of human stem cells is the generation
of cells and tissues that could be used for cell-based therapies. Stem cells
could be used to cure many diseases including cancer, Parkinson’s, diabetes, kidney
diseases, multiple sclerosis, macular degeneration, spinal injuries, paralysis,
Alzheimer’s, stroke, burns, heart disease, osteoarthritis, rheumatoid
arthritis, anemia, autism, cerebal palsy, chronic fatigue syndrome, depression,
diverticulitis, epilepsy, leukemia, immune suppression, and Lupus.
Stem
cells are also opening new opportunities. Embryos usually form inside the
mother's body and then grow into healthy babies. Scientific researchers,
however, have learned how to form embryos outside the body, in a laboratory.
This has been a wonderful development for mothers and fathers, who have been
unsuccessful in having a baby. Scientists can develop embryos and then implant
them in the mother to grow into normal, healthy babies. This means many couples
who couldn't have babies now can. Everyday, scientists are discovering new
diseases that could potentially be cured by stem cell research. Stem cell
research can possibly extend the human life span due to the replacement of
tissues in aging organs.
Reference:
~ http://www.bootstrike.com/Genetics/StemCells/proandcon.html