Stem cells 3 - Regeneration

Question 1

Does the gut regenerate after irradiation?

Answer 1

• yes
• cells that were previously not expressing Lgr5 now can
• likely happens by transit amplifying cells further towards the villus
• the crypt is empty, so likely the niche then becomes occupied

Question 2

What are transit amplifying cells?

Answer 2

• non-differentiated but proliferating
• between stem cell and differentiated

Question 3

Explain gut regeneration from organoids

Answer 3

• Lgr5+ cells from healthy gut
• cultured to form organdies
• transplanted into mice with damaged gut
• form healthy gut

Question 4

What are the layers of the skin?

Answer 4

Bottom up
- Dermis
- basal cells - undifferentiated and proliferate (stem cells)
- suprabasal cells - move towards outer surface, lay down protein matix, cells die - terminally differentiated
- cornified layers

Question 5

Explain the culturing of human epidermal cells

Answer 5

• forms holoclone, monoclonal and paraclone cells
• can be cultured indefinitely
• holoclones can have long term propagation (stem cells)

Question 6

Explain the need for muscle regeneration

Answer 6

• decreased use - degeneration
• increased use - regelation

Question 7

What are the stem cells for muscles?

Answer 7

Satellite cells - long cells

Question 8

What do satellite cells express?

Answer 8

Pax3

Question 9

Name 3 organs that regenerate poorly?

Answer 9

• lens
• brain
• heart

Question 10

Explain hydra regeneration

Answer 10

• cut in half
• cells sense their position by the head and foot ends creating a gradient that inhibit foot and head production in the wrong place
• each end regenerates
• gradient is restored before growth
• then grows

Question 11

Explain planarians regeneration

Answer 11

• cut in half - will regenerate
• cut in 3 - all 3 will regenerate
• thin middle cut - abnormal regeration - no morphogen gradient
• first cut, then second cut, thin middle section - will regenerate - anterior posterior gradient has become established
• multipotent stem cells - different than in hydra

Question 12

Explain axelotl limb regeneration

Answer 12

• cell type in blastema de-differentiating, proliferating, then de-differentiating
• re-differentiate into cell type which they originally were - not multipoint

Question 13

What is a blastema?

Answer 13

• area of growth and differentiation