1. Stem Cells
Science in the News
Adapted by your
teacher
Ms. Boehm

2. • What is a stem cell?
• Where do stem cells come from?
• What are stem cells good for?

3. Stem Cell Capable of dividing and making new cells of many types
2. Capable of self-renewal
(One daughter cell is like parent)
Differentiation: the process by which a cell undergoes a change to become a specialized cell type

4. Pluripotent cell (Embryonic Stem Cell)
Differentiation occurs step-by-step
Stem Cells
Pluripotent cell (Embryonic Stem Cell)

5. Differentiation occurs step-by-step
Stem Cells
Pluripotent cell (Embryonic Stem Cell)
Multipotent cell (Adult Stem Cell)

6. Embryonic Stem Cells Bridge the Gap from the
Fertilized Egg to the Fully Formed Organism
Adult Mouse
(Cell Division and Differentiation)
Fertilized Egg
(“Totipotent”)
Embryo
(“Pluripotent” Cells)

7. Each of these different
Muscle cell
Lens cell
IMPORTANT!!!!!
Each of these different
cell types has
the same DNA
Pancreas cell

8. How do cells with the same DNA
end up so different?
Protein A
Muscle
Cell
Gene A is on
Gene B is off
DNA X
Gene A
Gene B
Lens
Cell
Gene A is off
Gene B is on X
Pancreas
Cell
Gene A is on
Gene B is on

9. Where do stem cells come from?

10. Embryonic Stem Cells Pluripotent
Derived from the blastocyst 3-5 days after fertilization
Egg +
Zygote
Blastocyst
Fetus
Sperm

11. Embryonic Stem Cells A blastocyst contains 200-250 cells.
inner cell mass (embryo)
trophoblast (placenta)
A blastocyst contains cells.
The inner cell mass is only cells
There are 10,000,000,000,000 cells in a human adult

12. 1. Obtain cells from blastocyst
Inner cell mass

13. 2. Grow cells on a dish in the lab

14. ESCs grow on “feeder” cells
Provides nutrients to stem cells
Structural support for growth

15. 3. Cells grow in the dish Able to self-renew
Actual stem cells seen under microscope

16. ESCs have the potential to produce different types of cells
Liver
Muscle
Blood
Skin

17. And Where are the adult stem cells?
Neural
Brain cell types
Skin
Skin and hair
Gut
Gut derivatives
eye
Eye cell types
Blood & marrow
Blood cell types
Each type of adult stem cell is found in the tissue it makes.
A single totipotent stem cell can grow into an entire organism.
Pluripotent stem cells cannot grow into a whole organism, but they can become any other type of cell in the body.
Multipotent stem cells can only become particular types of cells: e.g. blood cells, or bone cells.
• mixed among the differentiated cells in that tissue

18. Different Types of Stem Cells: What and Where?
Embryonic
Adult
Potential:
• Can make all cell types (TOTIPOTENT)
• Only make certain cell types (MULTIPOTENT)
How they are obtained:
• Isolate from inner cell mass of embryo (blastocyst stage)
• Found in from adult tissue (but for most types we don’t know how to find them)

19. What are stem cells good for?

20. replace dead or damaged cells
Stem cells could
replace dead or damaged cells
Stem cells could be transplanted directly into diseased tissue where they would become the desired cell type or
Stem cells could be coaxed into specializing in the lab and then transplanted as differentiated tissue
Replacement is permanent!
(stem cells are self-maintaining)

21. A bone marrow transplant is an adult stem cell transplant
Leukemia

22. A bone marrow transplant is an adult stem cell transplant
Implant with Blood
Stem Cells
Blood Cells
Regenerated
Leukemia
(remove bone marrow)
1. Stem cells contribute to all blood cell types
2. After several months, the new cells still populate blood

23. Challenges of using adult stem cells

24. Challenge 1: Not yet found in all tissues
Pancreas

25. Challenge 2: Not easily accessible in all tissues
Brain
How are we going to get stem cells from the brain of the patient??
Muscles

26. Challenge 3. Rare & Difficult to isolate
Need “markers” to differentiate stem cells from other types of cells

27. Embryonic vs. Adult Stem Cells
Embryonic Stem Cells
Technical difficulties: How to direct specific differentiation
Controversy: Ethical considerations
Adult Stem Cells
Technical difficulties: Need to improve isolation techniques and optimize culturing conditions

28. Embryonic stem (ES) cells may be used to treat
deteriorating brain cells
Parkinson’s Disease: Selective death of subset of neurons
Partial replacement
of lost neurons
Mouse model of
Parkinson’s disease
Inject mouse ES cells
Into diseased brain
Could be used to treat Alzheimer’s, Huntington’s,
spinal cord injury, etc…
Still in experimental infancy, but shows much promise
for many diseases.

29. Where do the blastocysts come from?
In vitro fertilization
Aim to help infertile couples conceive children
Egg is fertilized with sperm in the lab
LAB
Zygote
Blastocyst
Sperm
Egg
Fertilization

30. In vitro fertilization
Implanted back into woman
Blastocyst
Frozen
Embryonic stem cells

31. Problem of immune rejection
Each person has own unique set of DNA
Body’s immune system rejects cells that do not belong to the individual
Need to match donor cells/tissues/organs to recipient
Stem cells used must be genetically compatible with patient
Embryonic stem cell lines derived from IVF will not be compatible
Somatic Cell Nuclear Transfer (SCNT)
= THERAPEUTIC CLONING

32. Somatic cell nuclear transfer (SCNT)
Somatic Cell = Any cell of the body, except sperm and egg
Nuclear Transfer = Moving the genetic material (DNA) of one cell to another
Nucleus of an egg is removed and replaced with the DNA of an adult cell
Creates patient-specific ES cell line

33. Therapeutic cloning vs. Reproductive cloning

34. What is cloning?
Clones = INDIVIDUALS that are genetically identical to another
 Identical twins are clones
Clones = CELLS that are genetically identical to another =

35. CLONING
CLONING

36. REPRODUCTIVE CLONING THERAPEUTIC CLONING
Need to be implanted into a surrogate mother
“Personalized”
Stem cells for tissue
therapy

37. 1. Remove nuclear DNA from egg

38. 1. Remove nuclear DNA from egg

39. 2. Insert DNA from donor into egg

40. 2. Insert DNA from donor into egg

41. THERAPEUTIC CLONING
“Personalized”
Stem cells for tissue
therapy

42. Advanced Cell Technology, Worchester, Massachusetts