Stem Cells

Question 1

pluripotent

Answer 1

can give rise to most cell types in the body
-embryonic stem cells

Question 2

multipotent

Answer 2

can give rise to a few cell types
-adult stem cells

Question 3

Idea of basic therapy

Answer 3

use stem cells to repair or replace damaged cells, organs or body parts
-isolate stem cell
-“instruct” them to go to a particular phenotype
-deliver to patient

Question 4

differentiate embryonic stem cells

Answer 4

-use cell specific “cocktail” to induce specific differentiation pathway

Question 5

oligodendrocytes to remyelinate after spinal cord injury

Answer 5

-human embryo stem cells with growth factors and hormones to convert them to oligodendrocytes
-then injected into rats 7 days after spinal cord injury
-transplant of oligodendrocytes helped restore spinal cord function
-doesn’t work if cells injected 10 months after injury bc glial scar forms

Question 6

where do we get stem cells from?

Answer 6

-embryonic stem cells-from 5 day old blastocysts (pluripotent)
-adult stem cells (multipotent)

Question 7

what are disadvantages for embryonic stem cells?

Answer 7

-potential for tumor formation
-ethical concerns, legal status

Question 8

where do embryonic stem cells come from?

Answer 8

day 5 blastocyst->inner cell mass

Question 9

in vitro fertilization

Answer 9

1.FSH administered during first 12 days of cycle
2.LH administered to induce super ovulation
3.24 eggs retrieved by aspiration of follicles
4.eggs are fertilized with sperm
5.cells are cultured
6.3 day old embryo (genetic testing can be performed)

Question 10

what is a large problem with injecting stem cells into humans?

Answer 10

stem cells from these embryos are recognized as foreign upon introduction introduction into a person and be rejected by their immune system

Question 11

what is a possible solution for rejection?

Answer 11

make stem cells that look like your own cells
-use your own stem cells, use umbilical cord blood
-make a blastocyst that is genetically identical to you and harvest inner cell mass (somatic cell nuclear transfer)

Question 12

Somatic cell nuclear transfer (SCNT)

Answer 12

1.remove nucleus from a human oocyte
2.insert nucleus from patients skin cell
3.induce development without sperm by placing oocyte with calcium with electric shock
4.resulting stem cells are genetically identical to patient

Question 13

B-cell replacement using type 1 diabetes SCNT

Answer 13

can only be transplanted into immunodeficient mice

Question 14

when can de-differentiation occur?

Answer 14

cancer can de-differentiate to an earlier developmental phenotype

Question 15

John Gurdon’s Experiment

Answer 15

-radiation is used on frog egg which destroys the nucleus
-nucleus from fully differentiated skin cell is inserted into enucleated egg->egg develops into tadpole
-skin cell had to somehow de-differentiate
-can make stem cells from any person if we can make stem cells from any person

Question 16

Yamanaka’s strategy

Answer 16

1.ID 2 dozen “embryonic-only” genes that are active in normal pluripotent stem cells but not adult cells
2.introduce all of these genes into adult skin cells
3.adult skin cells de-differentiate into pluripotent stem cells
4.Oct4, Sox2, Klf4, c-Myc can be used for reprogramming

Question 17

Induced pluripotent stem cells (iPS cells)

Answer 17

cells that are genetically reprogrammed to act like embryonic stem cells
-can be used instead of 5 day old blastocyst

Question 18

can we re-program cells without integrating DNA into the host chromosomes?

Answer 18

1.replace retroviral vectors with other vectors that don’t integrate into host chromosome->like adenovirus
-also avoids problem of mutagenesis
2.just add proteins themselves or drug that induces pluripotency

Question 19

age-related macular degeneration (AMD)

Answer 19

good candidate for cell based stem cell therapy
-leaky blood vessels release free floating blood into eye

Question 20

retinal pigment epithelium (RPE)

Answer 20

provides crucial support for photoreceptors
-photorecepters are embedded in the RPE
-death of RPE=death of photoreceptors (which is common in old people)
-function-blocking Ab can be used to stop further loses

Question 21

can you replace dying RPE with new RPE

Answer 21

-differentiate human embryonic stem cells (hESC) into RPE
-place into back of retina so they are juxtaposed with photoreceptors
-was successful, patients showed improvement in sight

Question 22

was tumorigenesis a concern with replacing the RPE?

Answer 22

transplanted RPE into pigs which was highly successful
-cells didn’t express proliferation
-scaffolds without RPE had poor photoreceptor survival