Stem Cells

Question 1

1. Explain the basics of stem cells, their niches, and the commitment (differentiation) of stem cells into different lineages.
2. Explain the concept of adult stem cell plasticity.
3. Explain the concept of reprogramming adult somatic cells into induced pluripotent stem (iPS) cells or embryonic-like stem cells.
4. Describe the role of stem cells in the initiation and maintenance of cancer.

Answer 1

x

Question 2

Totipotent:

Answer 2

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

Question 3

Pluripotent:

Answer 3

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

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

Adult stem cells have (more/less/equal) potential as embryonic stem cells?

Answer 6

less. They are not pluripotent. only

renew the tissue that they were derived from

Question 7

As an example of adult stem cells transdifferentiating into cell types of a lineage other than their own, a group in 2005 demonstrated what upon injury to the skin? (mouse experiment)

Answer 7

That cells descended from hematopoetic stem cells from a bone marrow transplant in a mouse were present in epithelial cells of the skin. When injured, the skin
recruited even more bone marrow cells to the site of injury. This represents a blood to epithelial lineage
transdifferentiation.

Question 8

How do you reprogram adult somatic cells (fibroblasts)?

Answer 8

o Obtain a 2-4mm punch biopsy from patient
o Using standard protocols, plate whole biopsy and culture out the fibroblast population. Expand.
o Seed fibroblasts in culture dish and add cocktail of transcription factors (SOX2, OCT4, etc)
o 3-4 weeks later: pick colonies of potential iPS cells based on morphology
o Expand clones and characterize to confirm pluripotency and self-renewal
o Freeze down bank of patient-specific induced pluripotent stem cells

Question 9

Reprogrammed pluripotent cells behave like embryonic stem cells, true or false?

Answer 9

True.

Question 10

Most traditional therapies target the 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. _____ is a drug that attempts to address this contingency. How does it work?

Answer 10

Cyclopamine.

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

Question 11

What are iPS cells? What could they be used for?

Answer 11

Induced Pluripotent Stem (iPS) Cells. Autografts [The generation of iPSC from the same EB patient
would not only potentially avoid the complication of
immune rejection, but also provide a source of
rejuvenated adult stem cells that are most likely
exhausted as a result of unsuccessful attempts to
repair blistered tissues]

Question 12

What are three obstacles in using iPS cells?

Answer 12

1. The development of alternative strategies for reprogramming adult skin cells into iPS cells without the use of viral vectors.
2. The development of efficient methods for differentiating
   genetically corrected iPS cells into tissue specific lineages.
3. The development of efficient, safe methods for homologous recombination

Question 13

What may be the solutions to these problems?

Answer 13

Viral vectors —-> mRNA
Genome editing —-> crisper, zinc fingers
differentiating lineages —-> Keratinocyte and Mesenchymal lines