Stem Cells
The Stem Cell Concept
A stem cell is an
undifferentiated,
dividing cell that gives
rise to a daughter cell
like itself and a
daughter cell that
becomes a specialized
cell type.
What Is a Stem Cell?
Unspecialized cells
 Give rise to more
than 225
specialized cells in
the body
 Serve as the
body’s repair
system

– Renew itself
– Replenish other
cells
In Summary: Two Major Types
of SC
Mature Stem Cells
Early Stem Cells
a.k.a. Adult (includes
umbilical cord & placenta)
a.k.a. Embryonic;
blastocystic
Cells obtained from specific
mature body tissues,
umbilical cord, placenta
Cells obtained from inner
cell mass of a blastocyst
Multipotent —
Pluripotent —
Give rise to multiple but
limited cell types
Flexible, give rise to
any cell type in the body
What Are the Sources of
Mature Stem Cells?
Mature Body Tissues
Stem Cells are Found in the Adult, but the Most Promising
Types of Stem Cells for Therapy are Embryonic Stem
Cells
Where Are Early Stem Cells
Found?
Who did it first?
 In 1998,
U. Wisconsin
research team
isolates stem
cells from
IVF-blastocysts
5 days of
development
The Inner Cell Mass is the Source of Embryonic Stem Cells
The embryo is destroyed by separating it into individual cells for the collection
of ICM cells.
How Big Is a Blastocyst?
What Are the Characteristics?

Early stem
cells are
pluripotent
Retain the
special
ability to
develop into
nearly any
cell type
 teratoma

Teratoma
Additional Potential Dilemmas – Therapeutic Cloning to Obtain
Matched Embryonic Stem Cells
Cultured mouse embryonic stem cells.
Cells from any source other than you or an identical twin present the
problem of rejection.
If so, how can matched embryonic stem cells be obtained?
A cloned embryo of a person can be made, and embryonic stem cells
harvested from these clones.
Some Thorny
Ethical Questions
Are these masses of
cells a human?
Is it ethical to
harvest embryonic
stem cells from the
“extra” embryos
created during in
vitro fertilization?
Somatic Cell Nuclear
Transfer (SCNT)
Sometimes referred to as
“therapeutic cloning”
SCNT: Asexual Reproduction
 No sperm involved
 Transfers nucleus
from a mature cell into
a donor egg
 Requires electric or
chemical stimulus to
begin dividing
 Functionally
different from regular
fertilized egg
What Should You Know About
SCNT?

Purpose:
– Find cures and therapies for diseases
– Awaken the natural capacity for self-repair
that resides in our genes

Potential Results:
– Patients will receive own stem cells to
treat disease
– No need for donor match
 Like transplantation, but without rejection
How Would SCNT Treat Disease?
What Should You Know About
SCNT?

No reputable scientist wants to clone
human beings
SCNT stem cells are alive in a Petri dish
 Unless implanted in uterus, you can not
generate a fetus
 Evidence suggests that SCNT stem cells
may never develop into a human even
when implanted

The Biotechnology
of Reproductive
Cloning
Even under the best of
circumstances, the
current technology of
cloning is very
inefficient.
Cloning provides the
most direct
demonstration that all
cells of an individual
share a common
genetic blueprint.
Therapeutic Cloning
Is there any ethical difference between therapeutic and reproductive cloning?
The Next Step?
Highly unlikely.
Attempts at human cloning are viewed very unfavorably in the scientific community.

http://learn.genetics.utah.edu/units/clonin
g/clickandclone/
Both Kinds of SCR are Needed
Mature Stem Cells
Early Stem Cells
First isolated in 1960s
First isolated in 1998
50+ years of research
9 years of research
Federal Funding =
>$2.7 Billion (FY02-06)
Federal Funding =
$132 Million (FY02-06)
Results: 50+ human
therapies
Results: Only in animal
trials; No human trials
What Are the Current State
Restrictions?
Which States Currently Support
ESCR?

http://www.pbs.org/wgbh/nova/scienceno
w/3209/04.html