Transcript Stem Cell Research Overview
Summer 2007 Workshop
in Biology and Multimedia
for High School Teachers
Stem Cell Research Overview
Straight Path
Outline
Potential Uses for Stem Cells
What are Stem Cells?
Stem cells are different from all other cells in the body.
Stem cells have 2 distinct properties: – They are unspecialized cells that are capable of renewing (regenerating) for long periods of time.
– They can give rise to different cell types (differentiation).
Stem Cell Differentiation
http://stemcells.nih.gov/info/basics/basics4.asp
2 types of Stem Cells
Embryonic – Obtained from in vitro fertilization, or aborted embryos – 3 or 4 day old embryo; blastocyst stage Adult – Found among some differentiated cells in a specific tissue or organ; placental cord; baby teeth
Unique Properties of Stem Cells
Regeneration
– Stem cells can replicate themselves over longer periods of time than other body cells Differentiation – Stem cells are unspecialized cells that can produce specialized body cells by first producing an intermediary cell http://www.kumc.edu/stemcell/images.html
Differentiation Animation
Differentiation (http://learn.genetics.utah.edu/units/biotech/microarray/)
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
Blastocyst Vocabulary
Trophoblast - outer shell of blastocyst.
Blastocoel blastocyst.
- fluid-filled space within Inner cell mass - group of 30+ cells on one end of the blastocoel, this is what produces the specialized cells needed for adult life.
Stem Cell Potential
Cell Type
Totipotent Pluripotent Multipotent
Description Examples
Each cell can develop into a new individual Cells from 1-4 day old embryos Cells can form any cell type Some cells of blastocyst (5 14 days old) Cells differentiated, but can form a number of other tissues Fetal tissue, cord blood, and adult stem cells
Pluripotent Differentiation
http://www.kumc.edu/stemcell/images.html
Adult Stem Cells (ASC)
ASCs are undifferentiated cells found among differentiated cells in a tissue or organ They are able to regenerate and differentiate into the major cell type of the tissue or organ in which they are found. (Multipotent) Recent experiments have raised the possibility that stem cells from one tissue/organ can create other cell types – This is known as PLASTICITY
http://www.stemcellresearch.org/testimony/20040929prentice.htm
Reprinted with permission of Do No Harm.
Adult Stem Cell Facts
Adult stem cells were found in many more tissues than expected Some may be able to differentiate into a number of different cell types, given the right conditions General consensus among scientist: – Adult stem cells DO NOT have as much potential as embryonic stem cells CLARIFICATION : not all new adult cells arise from stem cells – Most arise by MITOSIS of differentiated cells
Potential Uses for Stem Cell Research
Basic research – clarification of complex events that occur during human development & understanding molecular basis of cancer Biotechnology (drug discovery & development) – stem cells can provide specific cell types to test new drugs
Potential Uses Continued. . . .
Cell based therapies : – Regenerative therapy to treat Parkinson’s, Alzheimer’s, ALS, spinal cord injury, stroke, severe burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis – Stem cells in gene therapy • Stem cells as vehicles after they have been genetically manipulated – Stem cells in therapeutic cloning – Stem cells in cancer
Adult Stem Cells
Aka Mature, somatic Come from developed body tissues, umbilical cord, placenta (after birth) Multipotent - produces limited cell types First isolated in 1960s Funding (1999-2004) $2.24 billion Results - over 50 therapeutic uses for humans
Embryonic Stem Cells
Aka Early, blastocytic Come from the inner cell mass of a blastocyst Pluripotent - produces all cell types First Isolated in 1998 Funding (2002-2004) $55 million Results - no human trials, some success with animal trials to date
How Do You Make Stem Cells?
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Fertilized Egg Isolate blastocyst Remove inner cell mass Place into petri dish coated with feeder cells to promote division Differentiation!
Cloning
Reproductive Cloning – Producing new organisms genetically identical to donor Therapeutic Cloning – Make a therapeutic product (vaccine, human protein etc) – Deliver organs that will not be rejected – Act as animal models for human disease Breeding animals or plants with genetically favorable traits (genetic engineering)
SCNT - Somatic Cell Nuclear
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Transfer
Remove nucleus from egg cell and implant nucleus from patient’s cell to create fertilized egg.
Remove inner cell mass from blastocyst and place in petri dish for stem cell development & differentiation Cells will be almost identical to patient so rejection will not occur when transplantated.
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http://www.kumc.edu/stemcell/early.html
Reprinted with permission from the University of Kansas Medical Center.
http://www.stemcellresearch.org/testimony/20040929prentice.htm
Reprinted with permission of Do No Harm.
Problems with Therapeutic Cloning (1)
Some immune rejection may occur WHY?
– About 1% of DNA in the clone will not be identical to patient – It will be identical to egg cell used in SCNT due to the mitochondrial DNA in the cytoplasm of the egg cell
Problems with Therapeutic Cloning
Large number of eggs needed for SCNT which can only be obtained with: – Excessive hormone treatment of females – Surgery to remove eggs Both processes are potentially harmful to females!
Current Efforts with SC and Cancer
Tumor stem cell
Determine difference between cancer & normal stem cells Identify potential points in pathways critical for the survival of cancer SCs Develop therapies that specifically target cancer SC Duke University Explanation
Tumor cell
Drawn by Christine Rodriguez
Status of SC research in other
countries
Great Britain – Very liberal policies on research – Therapeutic cloning allowed, use of excess embryos & creation of embryos allowed – Stem cell research allowed France – Less liberal politics – Use of excess embryos from IVF allowed – Reproductive AND therapeutic cloning banned Germany – Very strict policies – Use of excess embryos and creation of embryos banned – Scientists can IMPORT embryos Click here to see a map of the stem cell policy around the world!
Debate in US
Federal funding available for research using the Bush lines only: – ES cell lines that were already in existence by 8/9/01 Disadvantage of Bush stem cell lines: – May have lost regenerative ability – May have accumulated mutations or infections Private companies continue to pursue stem cell research – Use of human embryos for IVF (in vitro fertilization) & therapeutic cloning is legal in most states • No federal funding – Some states are considering banning both
Global Status
Ongoing debate regarding use of embryos United Nations: proposal for a global policy to ban reproductive cloning only
What do you think?
Click on the link to take a poll on YOUR opinion regarding using cloning for stem cell research.
Cloning for Stem Cell Research Poll
Summary
Stem Cell Review Film Clip
References
Stem cells & Cloning Stem cells & Cloning; David A. Prentice, Benjamin Cummings, 2003 http://www.pbs.org/wgbh/nova/sciencenow/3302/06.ht
ml 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/2001/08/200 10809-2.html
Stem cells in class; Badran, Shahira; Bunker Hill Community College, 2007, Boston Museum of Science Biotechnology Symposium Harvard Stem Cell Institute