Advanced Placement Biology and Stem Cells Click on the cartoon above for a tutorial on Stem Cells...
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Transcript of Advanced Placement Biology and Stem Cells Click on the cartoon above for a tutorial on Stem Cells...
Advanced Placement Advanced Placement Biology Biology
and and Stem CellsStem Cells
Click on the cartoon above for a tutorial on Click on the cartoon above for a tutorial on
Stem Cells The Nature of Stem Cells and Embryology
What is a Stem Cell?• A cell that has the ability to continuously
divide and differentiate (develop) into various other kind(s) of cells/tissues
• Stem cells are different from other cells of the body in that they have the ability to differentiate into other cell/tissue types.
• This ability allows them to replace cells that have died. With this ability, they have been used to replace defective cells/tissues in patients who have certain diseases or defects.
Stem Cell ApplicationsStem Cell Applications• Tissue repair
nerve, heart, muscle, organ, skin Regenerate spinal cord, heart tissue or any
other major tissue in the body.• Cancers
Studies show leukemia patients treated with stem cells emerge free of disease
Injections of stem cells have also reduces pancreatic cancers in some patients.
• Autoimmune diseases diabetes, rheumatoid arthritis, MS
Click on the picture to watch a video on the skin shooter
Replace Skin
Kinds of Stem CellsKinds of Stem Cells
Stem cell Stem cell typetype DescriptionDescription ExamplesExamples
TotipotentTotipotent Each cell can develop Each cell can develop into a new individualinto a new individual
Cells from early (1-Cells from early (1-3 days) embryos3 days) embryos
PluripotentPluripotent Cells can form any (over Cells can form any (over 200) cell types200) cell types
Some cells of Some cells of blastocyst (5 to 14 blastocyst (5 to 14 days)days)
MultipotentMultipotentCells differentiated, but Cells differentiated, but can form a number of can form a number of other tissuesother tissues
Fetal tissue, cord Fetal tissue, cord blood, and adult blood, and adult stem cellsstem cells
Illustration by Matt Bohan, 2007
Embryonic Stem cells are obtained from In-Vitro Fertilization embryos that were not used - http://www.news.wisc.edu/packages/stemcells/illustration.html
This cellCan form the
Embryo and placenta
This cellCan just form the
embryo
Fully mature
EMBRYONIC STEM CELLSEMBRYONIC STEM CELLS
Blastocyst
http://stemcells.nih.gov/info/basics/ "Image courtesy of NIH resource for stem cell research"http://en.wikipedia.org/wiki/Image:Blastocyst_English.svg
Umbilical Cord Stem Cells
• Also Known as Wharton’s Jelly• Adult stem cells of infant origin• Less invasive than bone marrow• Greater compatibility• Less expensive
• Skin • Fat Cells• Bone marrow• Brain• Many other organs
& tissues
Adult Stem CellsAn undifferentiated cells found among specialized or differentiated cells in a tissue or organ after birth
Umbilical Cord Stem Cells
Three important functions:
1. Plasticity: Potential to change into other cell types like nerve cells
2. Homing: To travel to the site of tissue damage
3. Engraftment: To unite with other tissues
STEM CELLS HAVE ALSO BEEN FOUND IN “MATURE” ORGANS
Illustration by Matt Bohan, 2007
Differences between embryonic stem cells and adult stem cells
• They have different self-renewal capabilities– Embryonic stem cells: near indefinite self-renewal– Adult stem cells: limited self-renewal
• They have different differentiation potentials– .Embryonic stem cells: differentiate into all cell types in an
organism– Adult stem cells: differentiate into restricted cells types.
• They differ in how they respond to external stimuli– Embryonic stem cells are readily to change upon stimulation– Adult cells emphasize on stability and need to be activated by
cues, e.g. injuries.
PROS AND CONS OF EACH TYPEPROS AND CONS OF EACH TYPE
• EMBRYONIC– CELL LINES LAST
AND LAST AND LAST
– MULTIPOTENT
– EASY TO FIND
– ETHICAL ISSUES - WHEN DOES LIFE BEGIN?
• ADULT – CELL LINES DO
NOT LAST
– NOT MULTIPOTENT
– HARD TO LOCATE
– NO ETHICAL ISSUES
Why the Controversy Over Stem cells?Why the Controversy Over Stem cells?
• Embryonic Stem cells are derived from extra blastocysts that would otherwise be discarded following IVF.
• Extracting stem cells destroys the developing blastocyst (embryo).
-Questions for Consideration-• Is an embryo a person?• Is it morally acceptable to use embryos for
research?• When do we become “human beings?”
People in the US affected by diseases that may be helped by stem cell research
Condition Number of Persons AffectedCardiovascular diseases 58 MillionAutoimmune diseases 30 MillionDiabetes 16 MillionOsteoporosis 10 MillionCancer 8.2 MillionAlzheimer's disease 4 MillionParkinson's disease 1.5 MillionBurns (severe) 0.3 MillionSpinal cord injuries 0.25 MillionBirth defects 150,000 (per year)Total 128.4 Million --------------------------------------------------------------------------------------Data from the Patients' Coalition for Urgent Research, Washington, DC (according
to Perry, Ref. 267).
How can scientists ensure ethical conduct in stem cell research
• Education for researchers– Routine emphasis by principle investigators– Emphasis by funding agencies– Classes and seminars
• Education for the public– Understand the importance of research– Understand that scientists are under ethical guidance
• Communication and open dialogue– Understand each others’ opinion– Reach a rationale common ground.
• Last step: Legal reinforcement
Useful Resources
• National Institute of Health resource for stem cells (http://stemcells.nih.gov)
• International Society for Stem Cell Research: “Guidelines for the Conduct of Human Embryonic Stem Cell Research (www.isscr.org)”
• National Academy of Science: “Guidelines for human embryonic stem cell research” (http://www.nap.edu/openbook.php?isbn=0309096537)