Stem cells are unspecialized cells that can develop into different cell types. There are two main types: embryonic stem cells, which are pluripotent, and somatic or adult stem cells, which are multipotent, unipotent, or oligopotent. Stem cell division is triggered by internal genetic signals and external chemical and physical signals from other cells. Stem cells divide through obligate asymmetric or stochastic methods to maintain their numbers. Induced pluripotent stem cells are generated by genetically reprogramming adult cells, while cord blood contains pluripotent stem cells that can be used for regenerative medicine.

1. STEM CELLS
Ahmed Fayez Ahmed
Al_Azhar medicine university

2. Contents:-
 Stem Cells
 Types of Embryonic Stem Cells
 Types of Somatic Stem Cells
 Stem Cell division & the signals that trigger the division
 Normal Stem Cells division, Up normal Stem Cells division & Cancer cells
 Division methods of STEM CELLS
 Induced Pluripotent Stem Cells
 Cord Blood

3. WHAT ARE STEM CELLS?

4. Stem Cells are:
• Definition: Unspecialized &
undifferentiated cells that Can develop to
different specialized types of tissue in the
body.
• Place: They are found in various parts of
human body at every stage of development
from embryo to adult.
• Characteristics of any S.C type (coming):
• Self-renewal: the ability to go through
numerous cycles of cell division while
maintaining the undifferentiated state.
• Potency: the capacity to differentiate into
specialized cell types.
Dr. Ahmed Fayez

5. TYPES OF STEM CELLS:

6. Types Of Stem Cells
Stem Cells
Embyonic S.C
Totipotent
(Omni potent)
Pluripotent
Somatic S.C
Unipotent Oligopotent Multipotent
Dr. Ahmed Fayez

7. TYPE: EMBRYONIC STEM CELLS

8. Embyonic Stem Cells
Totipotent (a.k.a. omnipotent)
 stem cells can differentiate into
embryonic and extraembryonic cell
types.(Amnion, Yolk sac, Chorion,
Placenta, Umbilical Cord)
 They are: the Zygot & the cells produced
by the first few divisions of the fertilized
egg are also totipotent (Zygot divides
into 2, 4, 8, 16 cells ”morula”)
 N.B: Toti: means ‘whole’ as they make
the whole organism
Pluripotent
 stem cells are the descendants of
totipotent cells and can differentiate into
nearly all cells (except the
extraembryonic cell )
 They are: the inner cell mass, Bilamenlar
& Trilamenlar germ disc
 The differentiate into more than 200
types of cells
 N.B: Pluri: means ‘Several’
Dr. Ahmed Fayez

9. TYPE: SOMATIC STEM CELLS

10. Somatic Stem Cells (a.k.a. Adult S.C / Tissue S.C)
• Produce amany types of cells that in one
family
• e.g. Hematoid stem cells (make all types of
the blood & lymph cells
Multipotent
• Can produce Few types of cells
• e.g. lymphoid s.c (make many types
of lymph types like T, B, Nk cells
Oligopotent
• Can produce one type of cells
• e.g. : Muscle S.CUnipotent
Dr. Ahmed Fayez

11. MORE EXAMPLES OF MULTIPOTENT
STEM CELLS

16. STEM CELLS DIVISION

17. Stem cells can give rise to specialized
cells. When unspecialized stem cells
give rise to specialized cells, the
process is called differentiation. While
differentiating, the cell usually goes
through several stages, becoming
more specialized at each step

18. THE SIGNALS THAT TRIGGER EACH
STEP OF THE DIFFERENTIATION
PROCESS

19. The internal signals:
They are controlled by a cell's genes, which are interspersed across long strands of
DNA & carry coded instructions for all cellular structures and functions.
Notes:-
• Every stem cell has its internal signals to differentiate to a specific cells. For
example, a hematopoietic Sc gives rise to many types of blood cells. But It cannot
give rise to other cells.
• A series of mutations in a cell causes it to proliferate more than its immediate
neighbors. As the cluster of dividing cells grows over time, further mutations turn
atypical hyperplasia into a cancer (carcinoma)
Dr. Ahmed Fayez

20. The external signals
The external signals for cell
differentiation include chemicals
secreted by other cells, physical
contact with neighboring cells,
and certain molecules in
the microenvironment.
NB: the stem cell can make
produce many types of cells.
But the type it'll produce
depends on the
microenvironment conditions.
Dr.Ahmed Fayez

21. DIVISION METHODS OF STEM CELLS
Rule: the number of stem cells is fixed

22. • Obligate asymmetric replication:-
• Stem sell make 1 mother cell that replace the stem cell (Self-renewal)
& 1 daughter cell (differentiate to the cell).
Dr. Ahmed Fayez

23. Stochastic differentiation:-
• Stem cell divide into 2 daughter cell!!
• In the same time another Stem Cell makes 2 mother cell (the number
is still the same)
Dr. Ahmed Fayez

24. INDUCED PLURIPOTENT STEM
CELLS (IPS)

25. Induced Pluripotent Stem Cells (IPS)
• They are adult cells that have been genetically reprogrammed to
an Plutipotent cell–like state (by being forced to express genes
and factors important for maintaining the defining properties of
embryonic stem cells)
• Mouse iPSCs were first reported in 2006, and human iPSCs were first
reported in late 2007.
• It is the used in transplantation & regenerative medicine.
• tissues derived from iPSCs will be a nearly identical match to the cell
donor and thus probably avoid rejection by the immune system
• why?
• As it made from the body cell it self so it has the same antgens.
• It had been used to make heart , liver , retina , heart valves in labs
Dr. Ahmed Fayez

26. How to genetically reprogrammed a stem cell?
Viruses are currently used to introduce the reprogramming factors into adult cells, and this
process must be carefully controlled and tested before the technique can lead to useful
treatment for humans

27. More Information
in 2006 , Shinya Yamanaka found a new way to ‘reprogramme’ adult, specialized cells
to turn them into stem cells. These laboratory-grown stem cells are the iPS cells.
So how are these iPS cells made?
Yamanaka added four genes( Oct 4 / Klf 4 / Sox 2 / c-Myc ) to skin cells from a
mouse. This started a process inside the cells called reprogramming and, within 2 – 3
weeks, the skin cells were converted into induced pluripotent stem cells. Scientists
can now also do this with human cells, by adding even fewer than four genes.
Dr. Ahmed Fayez

29. CORD BLOOD: IS THE BLOOD IN
UMBILICAL CORD (IT HAS
PLURIPOTENT STEM CELLS)
It is also used to in regenerative midicne.

30. HOPE TO BE USEFUL