Stem cells are unspecialized cells that can differentiate into diverse specialized cell types and can self-renew to produce more stem cells. There are several types of stem cells including totipotent stem cells found in early embryos that can differentiate into any cell type, pluripotent stem cells like embryonic stem cells that can differentiate into any cell type but not extraembryonic tissues, and multipotent adult stem cells that reside in tissues and can differentiate into a limited number of closely related cell types to replace damaged cells. Stem cell potency refers to the differentiation potential of the cell with totipotent stem cells having the greatest potential and unipotent stem cells the lowest.

1. STEM CELLS and TYPES OF
STEM CELLS

2. What are Stem Cells?
 Cells that can divide and differentiate
into diverse specialized cells and can self-
renew to produce more stem cells.
 Also defined as unspecialized cells whereby
all specialized cells come from**

3. What are Stem Cells?
 Cells that can divide and differentiate
into diverse specialized cells and can self-
renew to produce more stem cells.
 Also defined as unspecialized cells whereby
all specialized cells come from**

4. What properties define a stem cell?
Unspecialized
nature
Differentiation Self-renewal

5. Unspecialized nature
 Stem cells do not have any tissue-specific
structures that allow it to perform special
functions.
 However, these cells give rise to specialized
cells.

6. Differentiation
 The process where unspecialized cells
acquire specific cellular traits, which
convert them into specialized cell types.
 Example: Blood stem cell

7. A tentative scheme of hemopoiesis.

8. Differentiation
 As stem cells differentiate, they are said to
become committed – they can no longer
differentiate into cell types outside of the
specified lineage.

9. Self-renewal
 The process where a stem cell divides to
produce at least one daughter cell that
remains an undifferentiated stem cell.
 It expands or maintains the stem cell
population throughout the life of an
organism.

10. terminally
differentiated
cell

11. Potency of Stem Cells
 Defined as the capacity to differentiate into
specialized cell type & be able to give rise to
any mature cell type.

12. OLIGOPOTENT,
UNIPOTENT
MULTIPOTENTPLURIPOTENTTOTIPOTENT
Potency of Stem Cells

13. Totipotent Stem Cell
 [toti = whole, potent = able to]
 A single cell which can give rise to all cell
types of an organism including
extraembryonic cells*
 Examples: fertilized egg, cells produced
by the first few divisions of fertilized egg**

14. Pluripotent Stem Cells
 [pluri = several, potent = able to]
 Have the potential to differentiate into all
cell of the embryo proper,* but not cells of
the extraembryonic tissues**
 Unrestricted in developmental potential***
 Ex.: Embryonic stem cells (ESCs), iPS, SCNT

16. Embryonic stem cells (ESCs)
 Derived from the inner mass of a blastocyst that
forms 5-7 days after zygote formation
 May be grown indefinitely in culture in the
primitive embryonic state*
 Retain the property of pluripotency during
extended growth in vitro
 Ex.: mouse ESCs, human ESCs

17. Production of differentiated cells from mouse ES cells in culture.

18. Type of stem cell Where do they come
from?
The cells they are able
to make
Advantages of these
stem cells
Drawbacks of these
stem cells
PLURIPOTENT
STEM CELLS
E.g. embryonic stem
cells (ESC), induced
pluripotent stem (iPS)
cells, somatic cell
nuclear transfer
(SCNT) stem cells.
ESC – Derived from
human blastocysts
(early stage
embryos) about 5–7
days old.
iPS cells – derived
from reprogrammed
somatic cells, such
as a skin cell.
SCNT stem cells –
derived from cloned
blastocyst made
from a
reprogrammed
somatic cell and
enucleated egg
Any cell in the body. Can be grown in
large quantities in
the laboratory. Can
be manipulated to
grow into different
cell types in the
laboratory.
iPS and SCNT –
these cells are an
identical match to
the somatic cell
donor and can be
used to study disease
and avoid immune
rejection.
Due to the
pluripotent nature
they also carry a risk
of cancer if not
treated properly
before transferred to
a patient.
As ESCs are not
patient specific
treatments using
them may trigger
rejection by the
patient’s immune
system.

19. Multipotent Stem Cells
 [multi = many, potent = able to]
 Stem cell populations that exist in their host tissues
for the lifetime of the organism – tissue-resident
stem cells.
 Cells that can differentiate into a number of cells but
only those of closely related family of cells*
 Ex.: cord blood stem cells, adult stem cells in the
bone marrow, brain, skin, skeletal muscle

20. Multipotent Stem Cells
 Tissue-resident stem cells have been used to
treat human diseases*
 Other stem cell populations in the body to
restore damaged tissues involved in
degenerative diseases such as diabetes,
osteoarthritis and multiple sclerosis.

21. Multipotent Stem Cells
 Important in maintenance of tissues during the
lifetime of an organism*
 Exist in low numbers in a stem cell niche**
 Cells are quiescent – not actively dividing
 They can be difficult to identify, isolate and
culture

22. Oligopotent Stem Cells
 Can differentiate into only a few cell types.
 Examples: lymphoid or myeloid stem
cells

23. Unipotent Stem Cells
 Can produce only one cell type, their own.
 Have the property of self-renewal, which
distinguishes them from non-stem cells.
 Examples: muscle stem cells, unipotent
progenitor cells forming most epithelial
tissues, hepatoblast