L23: Stem Cells

Question 1

stem cell

Answer 1

cell that is capable of extensive self renewal, creating more stem cells AND more differentiated progeny.

Stem cells play critical roles in homeostasis
and injury repair throughout life.

Question 2

types of stem cells

Answer 2

Question 4

adult stem cells

Answer 4

committed stem cells that give rise to a limited set of cells and tissue types (multipotent).

Examples: hematopoietic, epidermal, neural, hair,
melanocyte, muscle, tooth, gut, germline stem cells

Present throughout the life of the individual; but they are
rare and difficult to isolate, ~1/1000

Question 5

adult stem cells reside in a special regualtory environment called a ….

Answer 5

NICHE

Question 6

stem cell niche in the mammalian intestine

Answer 6

role of paneth cell (niche cell) - secretes Wnt, creates a barrier

Question 7

challenges for using adult stem cells in therapy

Answer 7

Difficult to find and isolate
because of scarcity

• Need to identify the niche condition
• Need different types of adult stem cells for different therapies
• They generally grow poorly in culture and are difficult to expand
• Need to overcome histo-incompatibility (rejection by the immune system of foreign cells)

Adult stem cells can be used in therapy
eg: bone marrow transplantation

Question 8

embryonic stem cells

Answer 8

derived from cells transiently present in embryogenesis; when cultured, can remain undifferentiated, but can give
rise to any cell in the body under appropriate conditions (pluripotent)

Question 9

ES cells have tremendous therapeutic potential

Answer 9

ask tutor

Question 10

problems associated with the use of ES cells in therapy

Answer 10

Technical problems:
* Histo-incompatibility (ES cells are not patient-derived
and can be rejected by the patient’s immune system)
* The differentiation pathways are not well known and are difficult to identify

Ethical problems:
* Is it ethical/moral to create human blastocysts just for
the purpose of generating stem cells for therapies?
* Is a blastocyst a human individual with rights?

Question 11

nuclear transfer stem cells = NTSCs

Answer 11

Question 12

problems associated with therapeutic cloning

Answer 12

Technical problem: success rate is very low (Dolly:
1/434 nuclei transplanted), a lot of eggs need to be donated

Ethical problem: Is it ethical/moral to create human blastocysts just for the purpose of generating stem cells? Is a blastocyst a human individual with rights?

Question 13

induced pluripotent stem cells (iPS cells)

Answer 13

mature cells can be reprogrammed to become pluripotent

Question 14

OSK transcription regulator are necessary and sufficient for pluripotency

Answer 14

Question 15

master regulators of pluripotency participate in a self-sustained positive feedback loop

Answer 15

Question 16

problems associated with the use of iPS cells in therapy

Answer 16

Technical problems:
* The pluripotency factors must be turned off in order to allow iPS cells to differentiate and to avoid tumorigenesis
* iPS cells are not identical to ES cells (eg. differences in some epigenetic marks)
* Somatic cells used to make iPS cells may carry damaging mutations
* Safety of reprogramming is not completely known
* Although straightforward it is still very costly to create iPS cells for every patient

Question 17

basic science applications of ESCs

Answer 17

Question 18

example of gene knockout experiment: leptin knockout mice are obese

Answer 18

KO experiment helped show that leptin is a hormone which regulates body fat as well as the sensation of hunger, and its loss results in obesity, susceptibility to diabetes, and other complications.

Question 19

Reprogrammed skin cells combined with gene therapy can treat sickle cell anemia in a mouse model

Answer 19

Question 20

organoids - study human mini organs in a dish using IPSCs

Answer 20

can be used as an experimental tool (epithelial functions), diagnostic tool (cystic fibrosis), and as a therapeutic tool (ulcerative colitis)

Question 21

adult hematopoietic stem cells are frequently used in clinics

Answer 21