stem cell is the mother of all cells , it’s a blank unspecialized
immature cell that has the capacity of self-renewal and
differentiated cells regeneration .
stem cell has some properties that make it different from
Self-renewal : stem cells are capable of dividing and
renewing themselves for long periods
Differentiation: stem cells are blank cells that can be
transformed to other types of cells.
Plasticity: the ability of stem cells from one tissue to
generate specialized cell type of another tissue, for
example hemopoietic cells may give rise to skeletal,
myocardial and hepatic cells.
Potency: it’s the differentiation potential of the stem cells
and according to potency stem cells can be classified.
Classification of stem cells
According to potency
Totipotent: stem cells produced from fusion of an egg
and sperm. Cells produced by the first few divisions of
the fertilized egg are also totipotent. These cells can be
differentiated into embryonic and extra embryonic cell
types (e.g. placenta)
Pluripotent: stem cells derived from inner cell mass of
the blastocyst and can differentiate into cells derived
from any of the three germ layers excluding the
Multipotent: stem cells that can produce only cells of
closely related family of cells for example
hematopoietic stem cells can differentiate into red
blood cells. White blood cells, platelets, etc.. .
Oligopotent: stem cells that can differentiate to only
few cells, for example lymphoid stem cells.
Bipotent: dual differentiation, for example oval cells can
differentiate into hepatic and biliary epithelium.
Unipotent: stem cells that can produce only one cell
According to their Origin
Embryonic stem cells: isolated from the inner cell mass of
the blastocyst of the discarded embryos after IVF( in vitro
fertilization) or from aborted embryos ,which has an
ethical debate in different thoughts and religions as
embryos are destroyed when inner cell mass is taken.
Fetal stem cells: obtained from aborted fetal gonadal
Cord blood stem cells: obtained from the remaining
blood in the umbilical cord after delivery, these cells
contain a big deal of hemopoietic stem cells.
Adult stem cells: are multipotent stem cells present in few
numbers in many sites(bone marrow and niches) of
Embryonic VS Adult stem cells
Embryonic Stem Cells Adult Stem Cells
can be differentiated to any cell
many but not any
Unlimited self-renewal capacity Limited self- renewal
Easier to get
IVF , Reproductive clonoing
Difficult to be obtained
blastocyst is destroyed
Are there other sources of
stem cells ?
The answer was negative till the emergence of the
last few years , science have exceeded the classic
limit of stem cells knowledge by the appearance of
Induced pluripotent stem
In the year of 2007 , professor Shinya
Yamanaka and his research team said
that aduld defferenitated cells can be
transformed into pluripotent cells ,
and they published their results of
transforming adult human
fibroblasts into pluripotent cells by
Shinya Yamanaka was
given Nobel Prize in
physiology for the year
2012 in grateful to his
promising work .
The evidence of success
of the trial is the ability of
the induced cells to
develop tumors (teratoma)
which is a sure sign of
their pluripotency by the
capacity to develop into
Stimulus –Triggered Acquisition
of pluripotency (STAP)
The newest breakthrough in the field of
stem cell research was declared by the
beginning of this year (2014) by the
valuable research of Haruko Obokata .
simply , adult cells like lymphocytes were
exposed to strong external stimulus like
transient low PH resulting in
After doing the resarch using lymphoctes , Obokata did it on other cells
of the bdoy and the same results were obtained.
some people are in favor of the stem cell and they have
their own motives …
embryonic stem cells will decrease human suffering.
embryonic stem cells are taken from excess IVF that will
be discarded anyway ..so it’s better to use them.
the other face of the debate is against stem cells
research entirely and specially against embryonic stem
cells ..also they have their own thoughts about that..
taking the cells from the blastocyst destroys it ..that’s
embryonic stem cells research will open the door to
reproductive cloning ..and that will replace the role of
the emergence of the great discovery
of ShinyaYamanaka and the STAP
technique will put an end for this
debate for sure ..there will no need to
destroy embryos anymore ..as adult
own cells will be transformed into
pluripotency by usage of some
transcription genes or some stressor
factors..we can save embryos .
Applications of stem cells
- Basic research
Stem cell theory of cancer
Role of signals in gene transcription and
differentiation of stem cells.
specific cell lines to test new drugs and decrease
Development effictive antitumor drugs
-cell based therapy:
regerative therapy for many diseases like
Parkinsonism , Alzhimer’s ,spinal cord injury , stroke ,
burns , heart diseases , diabetes …
Researchers in California report that they
have reversed the equivalent of type 1
diabetes in mice through transplants of stem
cells.Their experiments have replaced cells in
the pancreas damaged by the disease that
are unable to make insulin.
Stem cells may have a promising role in the
treatment of extenxive burns and lrge ulcer
through providing suffiecent numbers of
epidermal and epithelial cell lines that can be
used in replacing damged tissues.
Studies confirmed significant
effects of pluripotent stem
cell grafting in 6-OHDA and
MPTP animal models of
Pluripotent stem cells can
nestle in affected organs and
can differentiate into a
variety of cells, including
neural (dopamine producing)
cells. (Pub-med, Jan 2014)