introduction to stem cell
TRANSCRIPT
DEFINITION
• A cell that has the ability to continuously divide anddifferentiate (develop) into various other kind(s) ofcells/tissues.
• the body is made up of about 200 different kinds ofspecialised cells such as muscle cells, nerve cells, fat cellsand skin cells.
• all cells in the body come from stem cells.
• a stem cell is a cell that is not yet specialised.
• the process of specialisation is called differentiation.
• once the differentiation pathway of a stem cell has beendecided, it can no longer become another type of cell on itsown.
STEM CELL HISTORY
1998 - Researchers first extract stem cells from human embryos
1999 - First Successful human transplant of insulin-making cells
from cadavers
2001 - President Bush restricts federal funding for embryonic
stem-cell research
2002 - Juvenile Diabetes Research Foundation International
creates $20 million fund-raising effort to support stem-cell
research
2002 - California stem cell research
2004 - Harvard researchers grow stem cells from embryos using
private funding
2004 - Ballot measure for $3 Billion bond for stem cells
STEM CELL CHARACTERISTICS
‘Blank cells’ (unspecialized)
Capable of dividing and renewing themselves for long
periods of time (proliferation and renewal)
Have the potential to give rise to specialized cell types
(differentiation)
TYPES OF STEM CELL
Stem cell
type Description Examples
TotipotentEach cell can develop into
a new individual
Cells from early (1-3
days) embryos
PluripotentCells can form any (over
200) cell types
Some cells of
blastocyst (5 to 14
days)
Multipotent
Cells differentiated, but
can form a number of
other tissues
Fetal tissue, cord
blood, and adult
stem cells
KINDS OF STEM CELL
1. Embryonic stem cells come from a five to six-day-old embryo. Theyhave the ability to form virtually any type of cell found in thehuman body.
2. Embryonic germ cells are derived from the part of a humanembryo or foetus that will ultimately produce eggs or sperm(gametes).
3. Adult stem cells are undifferentiated cells found among specialisedor differentiated cells in a tissue or organ after birth. Based oncurrent research they appear to have a more restricted ability toproduce different cell types and to self-renew.
WHY ARE STEM CELLS SPECIAL?
Stem cells can:
1. self-renew to make more stem cells.
2. differentiate into a specialised cell type.
Embryonic stem cells (pluripotent)
Stem cells that can become
many types of cells in the
body are called pluripotent
Tissue stem cells (multipotent)
Stem cells that can
become only a few types
of cells are called
multipotent
TISSUE STEM CELLS
• often known as adult stem cells
• also includes stem cells isolated from fetal and cord blood
• reside in most tissues of the body where they are involved in repair and replacement
• generally very difficult to isolate
• already used to treat patients (haematologicalmalignancies, diseases of the immune system)
Bone marrow Kidney Lung
8-cell blastocystfertilised egg
2-cellegg
Day 0 Day 1 Day 2 Day 3 Day 6
• Donated excess IVF embryos
Images from www.advancedfertility.com
Where do embryonic stem cells come from?
Inner cell mass
Embryonic stem cells
• derived from donated IVF
embryos
• can be grown indefinitely
in the laboratory in an
unspecialised state
• retain ability to specialise
into many different tissue
types – know as
pluripotent
• can restore function in
animal models following
transplantationHuman embryonic stem cells can become any
cell in the body including these beating heart
cells
human embryonic
stem cells
INDUCED PLURIPOTENT STEM CELLS
• derived from adult cells in2007 - very recent discovery!
• can be grown indefinitely in
culture in an undifferentiated
state
• similar properties to
embryonic stem cells as can
differentiate into many
different tissue types –
pluripotent
• can create stem cells directly
from a patient for research
Induced change in
gene expression
pluripotent
stem cells
Starting cells from
donor tissue
iPS Cells
WHAT MAKES STEM CELLS SO VALUABLE?
Cell Therapy
Research
New Drugs
Pluripotent
stem cells
Tissue stem
cells
No one stem cell type fits all applications.
Research must continue using all types of stem cells.
APPLICATIONS
Disease
• Diabetes, Spinal cord
injury, Parkinson’s
disease, heart
disease
Genetic based Disease
• Cystic fibrosis,
Huntington’s
CHALLENGES TO STEM CELL/CLONING
RESEARCH
1. Stem cells need to be differentiated to theappropriate cell type(s) before they can beused clinically.
2. Recently, abnormalities in chromosomenumber and structure were found in threehuman ESC lines.
3. Stem cell development or proliferation
must be controlled once placed into
patients.
4. Possibility of rejection of stem cell
transplants as foreign tissues is very high.
5. Contamination by viruses, bacteria, fungi, and
Mycoplasma possible.
6. The use of mouse “feeder” cells to grow ESC
could result in problems due to
xenotransplantation.
UNKNOWNS IN STEM CELL/CLONING RESEARCH
• It is uncertain that human embryonic stem cells in vitro can give rise to all the different cell types of the adult body.
• It is unknown if stem cells cultured in vitro(apart from the embryo) will function as the cells do when they are part of the developing embryo
REFERENCES
www.stemcellcentre.edu.au
www.stemcellchannel.com.au