9. Stem Cells Flashcards
Define a “stem cell niche”
Stem cells being regulated by the cells around them.
Why can stem cells divide “functionally without limit?”
Because they express telomerase, which keeps their telomeres from getting too short.
Why is it important that stem cells divide slowly?
Because unchecked, undifferentiated cell replication could be devastating if it attained cancerous quality.
What are the characteristics of a Totipotent Stem Cell?
Has the ability to give rise to all the cells in an organism, including extraembryonic tissues
What are the characteristics of a Pluripotent Stem Cell?
Has the ability to give rise to all cells of that given embryo, and all adult cells after it. (Cannot grow extraembryonic tissues)
What are the characteristics of a Multipotent stem cell?
They can give rise to any cell of a given lineage.
Where might one gather pluripotent stem cells?
In the inner cell mass of a blastocyst.
How do founder cells determine the size of large organs?
They emit short range signals that encourage growth up to a set number of cell diameters.
What are transit amplifying cells?
They are not stem cells, as they are committed.
They are pre-programmed to have a finite number of divisions.
They create a set number of terminally differentiated cells as a method of growth control.
What is different about stem cell division from normal cell division?
They use divisional asymmetry - one cell differentiates, and one cell remains a stem cell.
The DNA strand that was originally in the mother stem cell - with all of its methylation patterns, unique transcription factors etc - remains in the mother cell (immortal strand hypothesis)
What is environmental asymmetry?
When a cell divides into two identical progeny, but the environment changes one into something else.
What would happen if you put a mouse embryonic stem cell into a blastocyst of a different mouse?
It would integrate into the blastocyst, and you would have a chimeric mouse
What type of stem cell can give rise to a teratoma?
An embryonic stem cell
What prevents us from using embryonic stem cells as a direct therapeutic agent?
Their ability to form teratomas, rather than fixing the tissue around them.
How do you grow Embryonic Stem Cells (ES cells?)
Why must you use serum free medium?
- Isolate them from an embryo
- Place them on a plate of irradiated “feeder cells” (often mouse fibroblasts that express growth factors)
Serum contains growth factors that can cause stem cell differentiation
(Surprise card from the DSA so I don’t forget)
What is the equation to calculate a patient’s estimated osmolality?
Estimated osmolality = 2 x Na + Glucose / 18 + BUN / 2.8
What are Nanog, Oct4, Sox2, and FoxD3?
What are Cripto and GDF-3?
They are transcription factors that maintain pluripotent stem cells.
Growth factors found in pluripotent stem cells
What do hematopoietic stem cells give rise to?
What about mesenchymal stem cells?
Blood components (platelets, RBC, WBC)
Tissues (bone, cartilage, fat, etc)
What is special about cord blood?
It can be used to treat a variety of disorders without genetic manipulation.
What sort of regenerative therapies use adult stem cells?
Neuro-regeneration
Bone marrow transplants
What are the challenges for regenerative medicine?
Immune rejection
Lack of knowledge
Ethics
What is somatic cell nuclear transfer?
What are the benefits?
A combination of cloning and embryonic stem cell technology.
Overcomes the issue of rejection by using the patient’s own genes.
Enables the reprogramming of adult cells, removing the ethical issue.
How might one induce pluripotency in an adult fibroblast cell?
Reprogram them (using viruses) and treat with embryonic stem cell transcription factors (KLF4, SOX2, c-Myc, Nanog, Oct 3/4, LIN-28)
What is the risk with induced pluripotent stem cell therapy?
Much higher risk for teratoma formation than with natural ES cells.
How are cells prepared in somatic cell nuclear transfer?
What are you left with?
Take an egg cell, take the nucleus out, fuse a (nucleated) somatic cell with the egg, and stimulate division.
You are left with a blastocyst, from which you can remove the inner cell mass as you would normally.
What are the challenges of SCNT?
Very technically demanding
Hard to source human egg cells
