Stem Cells Flashcards
pluripotent
can give rise to most cell types in the body
-embryonic stem cells
multipotent
can give rise to a few cell types
-adult stem cells
Idea of basic therapy
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
differentiate embryonic stem cells
-use cell specific “cocktail” to induce specific differentiation pathway
oligodendrocytes to remyelinate after spinal cord injury
-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
where do we get stem cells from?
-embryonic stem cells-from 5 day old blastocysts (pluripotent)
-adult stem cells (multipotent)
what are disadvantages for embryonic stem cells?
-potential for tumor formation
-ethical concerns, legal status
where do embryonic stem cells come from?
day 5 blastocyst->inner cell mass
in vitro fertilization
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)
what is a large problem with injecting stem cells into humans?
stem cells from these embryos are recognized as foreign upon introduction introduction into a person and be rejected by their immune system
what is a possible solution for rejection?
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)
Somatic cell nuclear transfer (SCNT)
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
B-cell replacement using type 1 diabetes SCNT
can only be transplanted into immunodeficient mice
when can de-differentiation occur?
cancer can de-differentiate to an earlier developmental phenotype
John Gurdon’s Experiment
-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
Yamanaka’s strategy
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
Induced pluripotent stem cells (iPS cells)
cells that are genetically reprogrammed to act like embryonic stem cells
-can be used instead of 5 day old blastocyst
can we re-program cells without integrating DNA into the host chromosomes?
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
age-related macular degeneration (AMD)
good candidate for cell based stem cell therapy
-leaky blood vessels release free floating blood into eye
retinal pigment epithelium (RPE)
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
can you replace dying RPE with new RPE
-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
was tumorigenesis a concern with replacing the RPE?
transplanted RPE into pigs which was highly successful
-cells didn’t express proliferation
-scaffolds without RPE had poor photoreceptor survival
