Stem CellsStem 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?What Is a Stem Cell? Unspecialized cellsUnspecialized cells Give rise to more Give rise to more

than 225 than 225 specialized cells in specialized cells in the bodythe body

Serve as the Serve as the body’s repair body’s repair systemsystem– Renew itselfRenew itself– Replenish other Replenish other

cellscells

In Summary: Two Major In Summary: Two Major Types of SCTypes of SC

Mature Stem CellsMature Stem Cells Early Stem CellsEarly Stem Cells

a.k.a. Adult (includes a.k.a. Adult (includes umbilical cord & umbilical cord & placenta)placenta)

a.k.a. Embryonic; a.k.a. Embryonic; blastocysticblastocystic

Cells obtained from Cells obtained from specific mature body specific mature body tissues, umbilical cord, tissues, umbilical cord, placentaplacenta

Cells obtained from Cells obtained from inner cell mass of a inner cell mass of a blastocystblastocyst

Multipotent — Multipotent — Give rise to multiple but Give rise to multiple but limited cell typeslimited cell types

Pluripotent — Pluripotent — Flexible, give rise to Flexible, give rise to any cell type in the bodyany cell type in the body

What Are the Sources of What Are the Sources of Mature Stem Cells?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 Where Are Early Stem Cells Found?Found?

5 days ofdevelopment

Who did it Who did it first?first?

In 1998, In 1998, U. Wisconsin U. Wisconsin research research team isolates team isolates stem cells stem cells from from IVF-IVF-blastocystsblastocysts

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?How Big Is a Blastocyst?

What Are the What Are the Characteristics?Characteristics?

Early stem Early stem cells are cells are pluripotentpluripotent

Retain the Retain the special special ability to ability to develop develop into nearly into nearly any cell any cell typetype

teratomateratoma

TeratomaTeratoma

Additional Potential Dilemmas – Therapeutic Cloning to Obtain Matched 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.

Cultured mouse embryonic stem cells.

Some Thorny Ethical Questions

Is it ethical to harvest embryonic stem cells from the “extra” embryos created during in vitro fertilization?

Are these masses of cells a human?

Somatic Cell Nuclear Somatic Cell Nuclear Transfer (SCNT)Transfer (SCNT)

Sometimes referred to as Sometimes referred to as

““therapeutic cloning”therapeutic cloning”

SCNT: Asexual ReproductionSCNT: 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 What Should You Know About SCNT?SCNT?

Purpose: Purpose: – Find cures and therapies for diseasesFind cures and therapies for diseases– Awaken the natural capacity for self-Awaken the natural capacity for self-

repair that resides in our genes repair that resides in our genes Potential Results:Potential Results:

– Patients will receive own stem cells to Patients will receive own stem cells to treat diseasetreat disease

– No need for donor matchNo need for donor match Like transplantation, but without rejection Like transplantation, but without rejection

How Would SCNT Treat How Would SCNT Treat Disease?Disease?

What Should You Know About What Should You Know About SCNT?SCNT?

No reputable scientist wants to clone No reputable scientist wants to clone human beingshuman beings

SCNT stem cells are SCNT stem cells are alivealive in a Petri in a Petri dishdish

Unless implanted in uterus, you can Unless implanted in uterus, you can not generate a fetusnot generate a fetus

Evidence suggests that SCNT stem Evidence suggests that SCNT stem cells may never develop into a human cells may never develop into a human even when implantedeven 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/cloning/clickandclone/

Both Kinds of SCR are Both Kinds of SCR are NeededNeeded

Mature Stem CellsMature Stem Cells Early Stem CellsEarly Stem Cells

First isolated in 1960sFirst isolated in 1960s First isolated in 1998First isolated in 1998

50+ years of research50+ years of research 9 years of research9 years of research

Federal Funding = Federal Funding = >$2.7 Billion (FY02-06)>$2.7 Billion (FY02-06)

Federal Funding = Federal Funding = $132 Million (FY02-06)$132 Million (FY02-06)

Results: 50+ human Results: 50+ human therapiestherapies

Results: Only in animal Results: Only in animal trials; No human trialstrials; No human trials

What Are the Current State What Are the Current State Restrictions?Restrictions?

Which States Currently Support Which States Currently Support ESCR?ESCR?

http://www.pbs.org/wgbh/nova/sciencenow/3209/04.html