Stem Cells and Cell Differentiation

Embryonic Stem Cells -Blastocyst Stage

3 parts:– Trophoblast– Blastocoel

(“blastoseel”) or blastocyst cavity

– Inner cell mass

Millions of cells can come from one blastocyst

http://www.kumc.edu/stemcell/images.html

1. What are Stem Cells?

a. Stem cells are different from all other cells in the body.

b. Stem cells have 2 distinct properties:1. They are unspecialized cells that are

capable of renewing (regenerating) for long periods of time.

2. They can give rise to different types of somatic cells (specialized body cells).

Stem Cell Differentiation

http://stemcells.nih.gov/info/basics/basics4.asp

2. Types of Stem Cells

a. Embryonic1. Obtained from in

vitro fertilization, or aborted embryos

2. 3 or 4 day old embryo; blastocyst stage

3. Source of controversy

2 types of Stem Cells

a. Adult1. Found among some

differentiated cells in a specific tissue or organ; placental cord; baby teeth

Adult Stem Cells Embryonic Stem Cells

Aka Mature, somatic Aka Early, blastocytic

Come from developed body tissues, umbilical cord, placenta (after birth)

Come from the inner cell mass of a blastocyst

Multipotent - produces limited cell types

Pluripotent - produces all cell types

First isolated in 1960s First Isolated in 1998

Funding (1999-2004) $2.24 billion

Funding (2002-2004) $55 million

Results - over 50 therapeutic uses for humans

Results - no human trials, some success with animal trials to date

3. Unique Properties of Stem Cells

a. Regenerationi. Stem cells can replicate

themselves over longer periods of time than other body cells

b. Differentiationi. Stem cells are unspecialized

cells that can produce specialized body cells by first producing an intermediary cell

http://www.kumc.edu/stemcell/images.html

3. Unique Properties of Stem Cells

ii. Stem cells differentiate by the activation of certain genes in DNA.iii. The genes that are activated determine the type of cell the stem cell will become.

4. GENE REGULATION

a. Virtually every cell in your body contains a complete set of genes

b. But they are not all turned on in every tissue

c. Each cell in your body expresses only a small subset of genes at any time

d. During development different cells express different sets of genes in a precisely regulated fashion

GENE REGULATION

e. Gene regulation occurs at the level of transcription or production of mRNA

f. A given cell transcribes only a specific set of genes (exons) and not others (introns)

Pluripotent Differentiation

http://www.kumc.edu/stemcell/images.html

http://www.stemcellresearch.org/testimony/20040929prentice.htm Reprinted with permission of Do No Harm.

4. How Do You Make Stem Cells?

a. Fertilized Egg

b. Isolate blastocyst

c. Remove inner cell mass

d. Place into petri dish coated with feeder cells to promote division

e. Differentiation!

5. Potential Uses of Stem Cell Research

a. Cell based therapies:1. Regenerative therapy to treat

Parkinson’s, Alzheimer’s, ALS, spinal cord injury, stroke, severe burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis

2. Stem cells in therapeutic cloning3. Stem cells in cancer

6. SCNT - Somatic Cell Nuclear Transfera. Remove nucleus from

egg cell and implant nucleus from patient’s cell to create fertilized egg.

b. Remove inner cell mass from blastocyst and place in petri dish for stem cell development & differentiation

c. Cells will be almost identical to patient so rejection will not occur when transplantated. http://www.kumc.edu/stemcell/early.html Reprinted with permission from the

University of Kansas Medical Center.

1.

2.

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7. Cloning

a. Reproductive Cloning1. Producing new organisms

genetically identical to donor

b. Therapeutic Cloning1. Make a therapeutic product

(vaccine, human protein etc.)

2. Deliver organs that will not be rejected

3. Act as animal models for human disease

c. Breeding animals or plants with genetically favorable traits (genetic engineering)

6. Debate in USa. Federal funding available for research is

strictly limitedi. ES cell lines that were already in existence by

8/9/01ii. Federal funding cannot be used on new

embryonic stem cells

b. Private companies continue to pursue stem cell research

i. No federal funding

7. Differentiation due to Environmental Factorsa. Some cells differentiate

due to environmental factors.

b. Many disorders and diseases are the result of environmental differentiation

i. Cancer

ii. Fetal Alcohol Syndrome

iii. Mesothelioma

References Stem cells & Cloning Stem cells & Cloning; David A.

Prentice, Benjamin Cummings, 2003 http://www.pbs.org/wgbh/nova/sciencenow/

3302/06.html http://www.stemcellresearch.org http://www.stemcells.nig.gov/info/nasics/nasics7.asp http://www.stemcells.nig.gov/info/scireport/

2006report.htm http://www.whitehouse.gov/news/releases/

2001/08/20010809-2.html Stem cells in class; Badran, Shahira; Bunker Hill

Community College, 2007, Boston Museum of Science Biotechnology Symposium

Harvard Stem Cell Institute