Lecture 9

Question 1

what is a problem when trying to use tissue specific stem cells?

Answer 1

they are difficult to isolate and maintain in vitro

Question 2

where can you isolate tissue specific stem cells from?

Answer 2

foetal tissue

Question 3

what are 2 things adult stem cells have to protect themselves against and how do they do this?

Answer 3

1) ageing
2) mutations
they do this by limiting the number of replications they have to make

Question 4

what happens as you move down the hierarchy of stem cells?

Answer 4

Differentiation becomes restricted, potency becomes reduced and fate decisions become irreversible

Question 5

3 reasons why the generic model doesn’t apply to all adult stem cell systems?

Answer 5

1) not all adult stem cells are multi potent, some are unipotent e.g germ cells
2) not all adult stem cells are not quiescent (not dividing/multiplying) some are constantly
3) Flow through hierarchy is not always unidirectional
- each different tissue is likely to have evolved slightly different strategies to maintain the tissue normally and during repair

Question 6

what is the fastest self renewing tissue in mammals?

Answer 6

the small intestine villi - continuous proliferation from the base - CBC (crypt base columnar) cells are the long term stem cells

Question 7

what is the definition of a stem cell niche?

Answer 7

A local tissue microenvironment that hosts and influences the behaviours and characteristics of stem cells

• has a defined anatomical location
• regulates self renewal

Question 8

what does removal from a stem cell niche result in?

Answer 8

cellular differentiation - therefore difficult to grow in vitro

Question 9

what 2 things do stem cell niches give signal for?

Answer 9

1) self renewal

2) surpassing differentiation

Question 10

what 4 things do stem cell niches provide?

Answer 10

• physical support
• soluble factors
• Cell mediated interactions
• Maintain and regulate the functions of stem cells

Question 11

what 3 things do cells in niches interact which each other through?

Answer 11

1) cell surface receptors
2) gap junctions
3) soluble factors

Question 12

what are the 2 cells in niches which interact with each other?

Answer 12

1) stem cells

2) stromal support cells

Question 13

2 examples of soluble factor interactions?

Answer 13

autocrine and paracrine factors

Question 14

what are 3 jobs of ECMs (cell adhesion molecules)?

Answer 14

1) anchor the stem cells to niche
2) Polarity cue for stem cell mitosis
3) Platform for signalling

Question 15

what can manipulation to a niche result in?

Answer 15

a change in stem cell behaviour

Question 16

what properties do stem cells have to have to repair tissue?

Answer 16

1) supply large numbers of differentiated cells
2) protect themselves from accumulating mutations
3) stop themselves ageing - adult stem cells have much lower levels of telomerase than ES cells

Question 17

what are the advantages or progenitors?

Answer 17

they allow adult stem cells to only divide a few times protecting them from mutations whilst still being able to repair tissue

Question 18

what are the stem cells for skeletal muscle?

Answer 18

satellite cells - if damage occurs cells re-enter the cell cycle and under go either symmetric divisions to remake stem cell pool and asymmetric divisions: myogenesis

Question 19

describe the niche concept ‘occupancy’

Answer 19

cell cell adhesion between stem cells and niche locates SCs in niche, near to self-renewing signals

Question 20

describe the niche concept ‘fate’

Answer 20

signals from the niche regulate stem cell self renewal, survival and maintenance

Question 21

describe the niche concept ‘asymmetric division’

Answer 21

the physical organisation of niche can polarise stem cells, this ensures an asymmetric division