SC_Adv_research

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  • SC_Adv_research

    1. 1. <ul><li>Summer 2007 Workshop </li></ul><ul><li>in Biology and Multimedia </li></ul><ul><li>for High School Teachers </li></ul>
    2. 2. Stem Cell Research Overview Mountainous Path
    3. 3. Outline <ul><li>What are Stem Cells? </li></ul><ul><li>Potential Uses </li></ul><ul><li>Claims Against Using Stem Cells </li></ul><ul><li>Cultivation Process </li></ul><ul><li>Stem Cells and Cloning </li></ul><ul><li>Stem Cell Theory of Cancer </li></ul><ul><li>Worldwide Status </li></ul>
    4. 4. What are stem cells? <ul><li>Stem cells are undifferentiated cells that have many potential scientific uses: </li></ul><ul><ul><li>Cell based therapies </li></ul></ul><ul><ul><ul><li>Often referred to as regenerative or reparative medicine </li></ul></ul></ul><ul><ul><li>Therapeutic cloning </li></ul></ul><ul><ul><li>Gene therapy </li></ul></ul><ul><ul><li>Cancer research </li></ul></ul><ul><ul><li>Basic research </li></ul></ul>
    5. 5. Two types of stem cells <ul><li>Embryonic Stem Cells (ESC): received from: </li></ul><ul><ul><li>Embryos created in vitro fertilization </li></ul></ul><ul><ul><li>Aborted embryos </li></ul></ul><ul><li>Adult Stem Cells (ASC): can be received from: </li></ul><ul><ul><li>Limited tissues (bone marrow, muscle, brain) </li></ul></ul><ul><ul><ul><li>Discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury or disease </li></ul></ul></ul><ul><ul><li>Placental cord </li></ul></ul><ul><ul><li>Baby teeth </li></ul></ul>
    6. 6. Source of ESC <ul><li>Blastocyst </li></ul><ul><ul><li>“ ball of cells” </li></ul></ul><ul><ul><li>3-5 day old embryo </li></ul></ul><ul><ul><li>Stem cells give rise to multiple specialized cell types that make up the heart, lung, skin, and other tissues </li></ul></ul><ul><li>Human ESC were only studied since 1998 </li></ul><ul><ul><li>It took scientists 20 years to learn how to grow human ESC following studies with mouse ESC </li></ul></ul>
    7. 7. How are embryonic stem cells harvested? <ul><li>Human ES cells are derived from 4-5 day old blastocyst </li></ul><ul><li>Blastocyst structures include: </li></ul><ul><ul><li>Trophoblast : outer layer of cells that surrounds the blastocyst & forms the placenta </li></ul></ul><ul><ul><li>Blastocoel : (“blastoseel”) the hollow cavity inside the blastocyst that will form body cavity </li></ul></ul><ul><ul><li>Inner cell mass : a group of approx. 30 cells at one end of the blastocoel: </li></ul></ul><ul><ul><ul><li>Forms 3 germ layers that form all embryonic tissues (endoderm, mesoderm, ectoderm) </li></ul></ul></ul>
    8. 8. Blastocyst http://www. ivf -infertility.com /infertility/infertility5. php
    9. 9. Unique characteristics of Stem Cells <ul><li>Stem cells can regenerate </li></ul><ul><ul><li>Unlimited self renewal through cell division </li></ul></ul><ul><li>Stem cells can specialize </li></ul><ul><ul><li>Under certain physiologic or experimental conditions </li></ul></ul><ul><ul><li>Stem cells then become cells with special functions such as: </li></ul></ul><ul><ul><ul><li>Beating cells of the heart muscle </li></ul></ul></ul><ul><ul><ul><li>Insulin-producing cells of the pancreas </li></ul></ul></ul>
    10. 10. Unspecialization <ul><li>Stem Cells are unspecialized </li></ul><ul><ul><li>They do not have any tissue-specific structures that allow for specialized function </li></ul></ul><ul><ul><li>Stem cells cannot work with its neighbors to pump blood through the body (like heart muscle cells) </li></ul></ul><ul><ul><li>They cannot carry molecules of oxygen through the bloodstream (like RBCs) </li></ul></ul><ul><ul><li>They cannot fire electrochemical signals to other cells that allow the body to move or speak (like nerve cells) </li></ul></ul>
    11. 11. Self - Renewal (Regeneration) <ul><li>Stem cells are capable of dividing & renewing themselves for long periods </li></ul><ul><ul><li>This is unlike muscle, blood or nerve cells – which do not normally replicate themselves </li></ul></ul><ul><ul><li>In the lab, a starting population of SCs that proliferate for many months yields millions of cells that continue to be unspecialized </li></ul></ul><ul><ul><ul><li>These cells are capable of long-term self-renewal </li></ul></ul></ul>
    12. 12. Specialization of Stem Cells: Differentiation <ul><li>Differentiation : unspecialized stem cells give rise to specialized (differentiated) cells in response to external and internal chemical signals </li></ul><ul><ul><li>Internal signals : turn on specific genes causing differential gene expression </li></ul></ul><ul><ul><li>External signals include: </li></ul></ul><ul><ul><ul><li>Chemicals secreted by other cells such as growth factors, cytokines, etc. </li></ul></ul></ul><ul><ul><ul><li>Physical contact with neighboring cells </li></ul></ul></ul>
    13. 13. Differentiation <ul><li>Why do your body cells look different although they all carry the same DNA, which was derived from one fertilized egg? </li></ul><ul><li>Differentiation example (http://learn.genetics.utah.edu/units/biotech/microarray/) </li></ul>
    14. 14. Potential of Stem Cells (vocab) <ul><li>Totipotent (total): </li></ul><ul><ul><li>Total potential to differentiate into any adult cell type </li></ul></ul><ul><ul><li>Total potential to form specialized tissue needed for embryonic development </li></ul></ul><ul><li>Pluripotent (plural): </li></ul><ul><ul><li>Potential to form most or all 210 differentiated adult cell types </li></ul></ul><ul><li>Multipotent (multiple): </li></ul><ul><ul><li>Limited potential </li></ul></ul><ul><ul><li>Forms only multiple adult cell types </li></ul></ul><ul><ul><ul><li>Oligodendrocytes </li></ul></ul></ul><ul><ul><ul><li>Neurons </li></ul></ul></ul>
    15. 15. Adult Stem Cells <ul><li>Adult or somatic stem cells have unknown origin in mature tissues </li></ul><ul><ul><li>Unlike embryonic stem cells, which are defined by their origin (inner cell mass of the blastocyst) </li></ul></ul>
    16. 16. http://www.stemcellresearch.org/testimony/20040929prentice.htm Reprinted with permission of Do No Harm.
    17. 17. Adult stem cells continued <ul><li>Adult stem cells typically generate the cell types of the tissue in which they reside </li></ul><ul><ul><li>Stem cells that reside in bone marrow give rise to RBC, WBC and platelets </li></ul></ul><ul><ul><li>Recent experiments have raised the possibility that stem cells from one tissue can give rise to other cell types </li></ul></ul><ul><ul><ul><li>This is known as PLASTICITY </li></ul></ul></ul>
    18. 18. Adult Stem Cell Plasticity Examples <ul><li>Blood cells becoming neurons </li></ul><ul><li>Liver cells stimulated to produce insulin </li></ul><ul><li>Hematopoietic (blood cell producing) stem cells that become heart cells </li></ul><ul><li>CONCLUSION: Exploring the use of adult stem cells for cell-based therapies has become a very important (and rapidly increasing) area of investigation by research scientists! </li></ul>
    19. 19. Adult stem cells: A brief history <ul><li>Adult stem cell research began about 40 years ago </li></ul><ul><li>Stem cell discoveries in 1960s: </li></ul><ul><ul><li>Bone marrow contains 2 populations of stem cells </li></ul></ul><ul><ul><ul><li>Hematopoietic stem cells – forms all blood cell types </li></ul></ul></ul><ul><ul><ul><li>Bone marrow stromal cells – mixed cell population that generates bone, cartilage, fat and fibrous connective tissue </li></ul></ul></ul><ul><ul><li>Rat brain contains two regions of dividing cells, which become nerve cells </li></ul></ul>
    20. 20. History Cont. <ul><li>Stem Cell Discoveries in the 1990s </li></ul><ul><ul><li>Neural stem cells in brain are able to generate the brain’s three major cell types </li></ul></ul><ul><ul><ul><li>Astrocytes </li></ul></ul></ul><ul><ul><ul><li>Oligodendroglial cells </li></ul></ul></ul><ul><ul><ul><li>Neurons </li></ul></ul></ul>http://www.alsa.org/images/cms/Research/Topics/cell_targets.jpg
    21. 21. Adult Stem Cell Facts <ul><li>Adult stem cells were found in many more tissues than expected </li></ul><ul><li>Some may be able to differentiate into a number of different cell types, given the right conditions </li></ul><ul><li>General consensus among scientist: </li></ul><ul><ul><li>Adult stem cells DO NOT have as much potential as embryonic stem cells </li></ul></ul><ul><li>CLARIFICATION : not all new adult cells arise from stem cells </li></ul><ul><ul><li>Most arise by MITOSIS of differentiated cells </li></ul></ul>
    22. 22. Potential Uses of Stem Cells <ul><li>Basic research – clarification of complex events that occur during human development & understanding molecular basis of cancer </li></ul><ul><ul><li>Molecular mechanisms for gene control </li></ul></ul><ul><ul><li>Role of signals in gene expression & differentiation of the stem cell </li></ul></ul><ul><ul><li>Stem cell theory of cancer </li></ul></ul>
    23. 23. Potential uses cont. <ul><li>Biotechnology (drug discovery & development) – stem cells can provide specific cell types to test new drugs </li></ul><ul><ul><li>Safety testing of new drugs on differentiated cell lines </li></ul></ul><ul><ul><li>Screening of potential drugs </li></ul></ul><ul><ul><ul><li>Cancer cell lines are already being used to screen potential anti-tumor drugs </li></ul></ul></ul><ul><ul><ul><li>Availability of pluripotent stem cells would allow drug testing in a wider range of cell types & to reduce animal testing </li></ul></ul></ul>
    24. 24. Potential uses cont. <ul><li>Cell based therapies : </li></ul><ul><ul><li>Regenerative therapy to treat Parkinson’s, Alzheimer’s, ALS, spinal cord injury, stroke, severe burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis </li></ul></ul><ul><ul><li>Stem cells in gene therapy </li></ul></ul><ul><ul><ul><li>Stem cells as vehicles after they have been genetically manipulated </li></ul></ul></ul><ul><ul><li>Stem cells in therapeutic cloning </li></ul></ul><ul><ul><li>Stem cells in cancer </li></ul></ul>
    25. 25. Embryonic vs Adult Stem Cells <ul><li>Totipotent </li></ul><ul><ul><li>Differentiation into ANY cell type </li></ul></ul><ul><li>Known Source </li></ul><ul><li>Large numbers can be harvested from embryos </li></ul><ul><li>May cause immune rejection </li></ul><ul><ul><li>Rejection of ES cells by recipient has not been shown yet </li></ul></ul><ul><li>Multi or pluripotent </li></ul><ul><ul><li>Differentiation into some cell types, limited outcomes </li></ul></ul><ul><li>Unknown source </li></ul><ul><li>Limited numbers, more difficult to isolate </li></ul><ul><li>Less likely to cause immune rejection, since the patient’s own cells can be used </li></ul>
    26. 26. Claims against ESC (unsubstantiated thus far!) <ul><li>Difficult to establish and maintain * </li></ul><ul><li>Difficulty in obtaining pure cultures from dish* </li></ul><ul><li>Potential for tumor formation and tissue* destruction </li></ul><ul><li>Questions regarding functional differentiation </li></ul><ul><li>Immune rejection </li></ul><ul><li>Genome instability </li></ul><ul><li>Few & modest results in animals, no clinical treatments </li></ul><ul><li>Ethically contentious </li></ul>* = same problem with ASC
    27. 27. Cell Culture Techniques for ESC <ul><li>Isolate & transfer of inner cell mass into plastic culture dish that contains culture medium </li></ul><ul><li>Cells divide and spread over the dish </li></ul><ul><li>Inner surface of culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide </li></ul>
    28. 28. <ul><li>This coating is called a FEEDER LAYER </li></ul><ul><ul><li>Feeder cells provide ES cells with a sticky surface for attachment </li></ul></ul><ul><ul><li>Feeder cells release nutrients </li></ul></ul><ul><li>Recent discovery: methods for growing embryonic stem cells without mouse feeder cells </li></ul><ul><ul><li>Significance – eliminate infection by viruses or other mouse molecules </li></ul></ul><ul><li>ES cells are removed gently and plated into several different culture plates before crowding occurs </li></ul>
    29. 29. http://www.news.wisc.edu/packages/stemcells/illustration.html Images depict stem cell research at the University of Wisconsin Madison.
    30. 30. Cloning of whole organisms <ul><li>Purpose: </li></ul><ul><ul><li>Reproductive cloning in animals </li></ul></ul><ul><ul><li>Therapeutic cloning in animals </li></ul></ul><ul><ul><li>Breeding animals or plants with favorable traits </li></ul></ul><ul><ul><li>Producing TRANSGENIC animals that: </li></ul></ul><ul><ul><ul><li>Make a therapeutic product (vaccine, human protein etc) </li></ul></ul></ul><ul><ul><ul><li>Act as animal models for human disease </li></ul></ul></ul><ul><ul><ul><li>Deliver organs that will not be rejected (cells lacking cell surface markers that cause immune rejection) </li></ul></ul></ul><ul><ul><li>Vaccines in biotech industry: steps in cloning a gene </li></ul></ul>
    31. 31. SCNT: Somatic Cell Nuclear Transfer <ul><li>SCNT is a method used for: </li></ul><ul><ul><li>Reproductive cloning such as cloning an embryo </li></ul></ul><ul><ul><li>Regenerative cloning to produce “customized” stem cells & overcome immune rejection </li></ul></ul><ul><li>Blastula stage cannot continue to develop in vitro </li></ul><ul><ul><li>It must be implanted into surrogate mom </li></ul></ul><ul><ul><li>Surrogate mom is just a container that provides protection & chemical signals necessary for development </li></ul></ul>
    32. 32. http://www. kumc . edu / stemcell /early.html Reprinted with permission from the University of Kansas Medical Center.
    33. 33. http://www.stemcellresearch.org/testimony/20040929prentice.htm Reprinted with permission of Do No Harm.
    34. 34. Challenges of Reproductive Cloning <ul><li>Many animals were cloned after Dolly </li></ul><ul><ul><li>Cats, pigs, mice, goats, cattle, rabbits </li></ul></ul><ul><li>Obstacles: </li></ul><ul><ul><li>Very inefficient process </li></ul></ul><ul><ul><li>Most clones have deleterious effects & die early </li></ul></ul><ul><ul><li>Surviving clones show premature aging signs </li></ul></ul><ul><ul><li>Signs of abnormal embryonic development: </li></ul></ul><ul><ul><ul><li>Clones & their placentas grow much faster than expected in surrogate mom </li></ul></ul></ul>
    35. 35. Therapeutic Cloning <ul><li>3 goals of therapeutic cloning by SCNT in humans: </li></ul><ul><ul><li>Use embryo as source for ES cells </li></ul></ul><ul><ul><li>Use ES cells to generate an organ </li></ul></ul><ul><ul><ul><li>In this case the organ generated will carry cells with the same genetic markers as the patient (recipient) </li></ul></ul></ul><ul><ul><li>Correct genetic error in ESC in blastula stage </li></ul></ul>
    36. 36. Pitfalls of therapeutic cloning (1) Some immune rejection may occur- WHY? <ul><ul><li>About 1% of the DNA in the clone will NOT be identical to donor cell (patient) </li></ul></ul><ul><ul><li>It will be identical to egg cell used in SCNT </li></ul></ul><ul><ul><li>REASON: mitochonrial DNA in eggs </li></ul></ul><ul><ul><ul><li>Human mitochondria carry about 13 genes, some of which code for surface proteins </li></ul></ul></ul>
    37. 37. Pitfalls of therapeutic cloning (2) <ul><li>Large number of eggs needed for SCNT </li></ul><ul><li>To harvest large number of eggs: </li></ul><ul><ul><li>Excessive hormone treatment of females to induce high rate of ovulation </li></ul></ul><ul><ul><li>Surgery to retrieve eggs </li></ul></ul><ul><ul><ul><li>Both can be harmful to female human </li></ul></ul></ul><ul><ul><ul><li>Cow/pig females may be used </li></ul></ul></ul><ul><ul><li>Cow/pig eggs will carry species-specific mitochondrial genes </li></ul></ul><ul><ul><ul><li>Mixing species is reason for concern! </li></ul></ul></ul>
    38. 38. Common Opinions <ul><li>Reproductive cloning is a criminal offense (it is ILLEGAL worldwide!) </li></ul><ul><li>Therapeutic cloning is acceptable, however there is still significant controversy over whether: </li></ul><ul><ul><li>the clone is implanted into the uterus of surrogate mom? OR </li></ul></ul><ul><ul><li>the clone is explanted into culture dish to generate ES cells </li></ul></ul>
    39. 39. Stem Cell Theory of Cancer <ul><li>1855: Rudolf Virchow developed the Embryonal- Rest Hypothesis </li></ul><ul><ul><li>Microscopic examination of tumor samples revealed many morphological (structural & functional) resemblances to ESC in a developing fetus </li></ul></ul><ul><li>Isolation of teratoma: nonmalignant tumors </li></ul><ul><ul><li>Teratoma represents a ball of almost all cell types </li></ul></ul><ul><ul><li>This indicates that teratoma may originate from unregulated stem cells that can give rise to almost all tissues </li></ul></ul>
    40. 40. Teratoma <ul><li>Ovarian Teratoma </li></ul><ul><ul><li>You can see teeth! </li></ul></ul>http://home.earthlink.net/~radiologist/ tf /040802. htm Image courtesy of Leonard J. Tyminski, M.D., Radiologist at earthlink.net
    41. 41. Current Efforts with SC and Cancer <ul><li>Determine difference between cancer & normal stem cells </li></ul><ul><li>Identify potential points in pathways critical for the survival of cancer SCs </li></ul><ul><li>Develop therapies that specifically target cancer SC </li></ul><ul><li>Duke University Explanation </li></ul>Drawn by Christine Rodriguez Tumor stem cell Tumor cell
    42. 42. Status of SC research in other countries <ul><li>Great Britain </li></ul><ul><ul><li>Very liberal policies on research </li></ul></ul><ul><ul><li>Therapeutic cloning allowed, use of excess embryos & creation of embryos allowed </li></ul></ul><ul><ul><li>Stem cell research allowed </li></ul></ul><ul><li>France </li></ul><ul><ul><li>Less liberal politics </li></ul></ul><ul><ul><li>Use of excess embryos from IVF allowed </li></ul></ul><ul><ul><li>Reproductive AND therapeutic cloning banned </li></ul></ul><ul><li>Germany </li></ul><ul><ul><li>Very strict policies </li></ul></ul><ul><ul><li>Use of excess embryos and creation of embryos banned </li></ul></ul><ul><ul><li>Scientists can IMPORT embryos </li></ul></ul>
    43. 43. Debate in US <ul><li>Federal funding available for research using the Bush lines only: </li></ul><ul><ul><li>ES cell lines that were already in existence by 8/9/01 </li></ul></ul><ul><li>Disadvantage of Bush stem cell lines: </li></ul><ul><ul><li>May have lost regenerative ability </li></ul></ul><ul><ul><li>May have accumulated mutations or infections </li></ul></ul><ul><li>Private companies continue to pursue stem cell research </li></ul><ul><ul><li>Use of human embryos for IVF & therapeutic cloning is legal in most states </li></ul></ul><ul><ul><ul><li>No federal funding </li></ul></ul></ul><ul><ul><li>Some states are considering banning both </li></ul></ul>
    44. 44. Global Status <ul><li>Ongoing debate regarding use of embryos </li></ul><ul><li>United Nations: proposal for a global policy to ban reproductive cloning only </li></ul>
    45. 45. References <ul><li>Stem cells & Cloning Stem cells & Cloning; David A. Prentice, Benjamin Cummings, 2003 </li></ul><ul><li>http://www.pbs.org/wgbh/nova/sciencenow/3302/06.html </li></ul><ul><li>http://www.stemcellresearch.org </li></ul><ul><li>http://www.stemcells.nig.gov/info/nasics/nasics7.asp </li></ul><ul><li>http://www.stemcells.nig.gov/info/scireport/2006report.htm </li></ul><ul><li>http://www.whitehouse.gov/news/re;eases/2001/08/20010809-2.html </li></ul><ul><li>Stem cells in class; Badran, Shahira; Bunker Hill Community College, 2007, Boston Museum of Science Biotechnology Symposium </li></ul><ul><li>Harvard Stem Cell Institute </li></ul>

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