stem cells and differentiation

Question 1

Embryonic stem cells are

Answer 1

pluipotent and have the potential to differentiate into all cell types.

Question 2

Totipotent:

Answer 2

Ability to give rise to all cells of the organism (epiblast) and all extraembryonic tissues (trophectoderm, extraembryonic endoderm)
*anything, placenta included

Question 3

Pluripotent:

Answer 3

Ability to give rise to cell types of all germ layers (mesoderm, ectoderm, endoderm)
*Just body

Question 4

Multipotent:

Answer 4

Ability to give rise to cell types of a specific lineage

Question 5

Stem cell niche:

Answer 5

microenvironment in which stem cells are found, which interacts with stem cells to regulate stem cell fate.

Question 6

During embryonic development, various niche factors act on embryonic stem cells to ______

Answer 6

alter gene expression, and induce their proliferation or differentiation for the development of the fetus.

Question 7

Within the human body, stem cell niches maintain adult stem cells in a ______ state, but after tissue injury, ________

Answer 7

quiescent

the surrounding micro-environment actively signals to stem cells to either promote self renewal or differentiation to form new tissues.

Question 8

Several factors are important to regulate stem cell characteristics within the niche:

Answer 8

1. cell-cell interactions between stem cells
2. interactions between stem cells and neighboring differentiated cells
3. interactions between stem cells and adhesion molecules
4. extracellular matrix components
5. the oxygen tension
6. growth factors
7. cytokines
8. physiochemical nature of the environment including the pH, ionic strength and metabolites, like ATP

Question 9

The stem cells and niche may induce ______

Answer 9

each other during development and reciprocally signal to maintain each other during adulthood.

Question 10

adult stem cells are not

Answer 10

pluripotent

but can transdifferentiate

Question 11

how do you reprogram adult somatic cells (fibroblasts)?

Answer 11

1. Obtain biopsy
2. plate biopsy and culture out the fibroblast population. Expand.
3. Seed fibroblasts in culture dish and add transcription factors
4. 3-4 weeks later: pick colonies
5. Expand clones and characterize to confirm
6. Freeze down bank of induced pluripotent stem cells

Question 12

Benefit of personalized medicine

Answer 12

You’d be able to differentiate cell types of interest for the patient’s disease that are completely matched to that patient, eliminating the issue of immune rejection.

Question 13

Stem cells are likely targets of carcinogens because:

Answer 13

they are the only cells to permanently reside in epithelial tissues.

Question 14

Most cancers are cancers of the:

Answer 14

epithelium (breast, lung, colon, etc)

Question 15

Cancer stem cells likely exist in

Answer 15

all types of cancer

While they comprise a very rare population of cells in a human tumor, their presence is very sinister

Question 16

Most traditional therapies target the

Answer 16

rapidly dividing cells that comprise the majority of the tumor population.

Thus, you can get nearly complete ablation of a patient’s cancer, but leave behind the cancer stem cells. The result is that the stem cells can repopulate the tumor and the patient relapses tumor can come back.

Question 17

If you can hit both the

Answer 17

main body of the tumor and the cancer stem cells, you should be able to kill the tumor and prevent its return.
example: cyclopamine

Question 18

Cyclopamine mechanism:

Answer 18

1. Interacts with smoothened to prevent activation of the hedge hog pathway
2. Targets cancer stem cells with minimal side effects