Lecture 9 - Regenerative biology

Question 1

What is regenerative biology?

Answer 1

regeneration is the ability of organisms to restore damaged or diseases structures in form & function

Question 2

Do hydra use morpholaxis or epimorphosis?

Answer 2

morpholaxis

Question 2

What type of organisms have a really food ability to regenerate (whole body regeneration)?

Answer 2

simple (smaller animals)

Question 2

Do aquatic vertebrates or terrestrial vertebrates have more regenerative capabilities?

Answer 2

aquatic (limb, eye, spinal cord, heart)

Question 3

Do salamander’s limbs use morpholaxis or epimorphosis?

Answer 3

epimorphosis

Question 4

What is morpholaxis?

Answer 4

involves using existing cells and repatterning them to incorporate a designated area which will represent the anterior

• involves de-differentiation and trans-differentiation

Question 5

What is epimorphosis?

Answer 5

involves de differentiation and/or stem cells (proliferation)

• there is growth (of the missing area
• the cells at the area which has been cut becomes regenerative cells & proliferation - likely to also have stem cells which can contribute to the growth

Question 6

How does wounding cause an immediate wound response?

Answer 6

• signals highly conserved, even in plants, to be wounded

Question 7

What are the early wound responses?

Answer 7

• ATP is released by damaged cells (quick process)
• Intracellular calcium is elevated (highly conserved as a wound response)
• reactive oxygen (H2O2 - hydrogen peroxide) is released

These signals act as signals over the first few minutes to initiate the wound response.

Question 8

What are the 3 steps of the wound response?

Answer 8

1. cytoskeleton changes to close wound. Cells on the edge form “purse strings” to close the wound.
2. immune cells are recruited from blood stream & skin. Neutrophils identify wound signals and look for bacteria which may have entered due to wound - also triggers the repair of the wound.
3. initiates regeneration of scar formation (depending on regenerative capabilities) - occurs once wound is sealed off.

Question 9

What are the 2 results after a wound response?

Answer 9

• regeneration
• scarring

Question 10

What is fibrosis?

Answer 10

scarring (permanent)

Question 11

What causes fibrosis (scarring)?

Answer 11

caused when fibroblasts secrete high levels of extracellular matrix (collagens)

Question 12

What are the 4 stages of salamander regeneration?

Answer 12

1. Amputation - early wound signals (development of a stump)
2. Wound closure - cytoskeletal rearrangements & epithelial movement
3. Wound epithelium - signaling from wound epithelium to induce de-differentiation (develops hard skin)
4. Blastema - blastema cell proliferate - then regrowing begins

Question 13

What is the first sign that regeneration has begun?

Answer 13

the formation of a wound epithelium

Question 14

What is the AER (apical ectodermal ridge)?

Answer 14

one of the main signaling centres during limb development

Question 15

What is the blastema formed of?

Answer 15

cells that partially de-differentiate

Question 16

Describe the process by which multipotent blastema cells are created?

Answer 16

muscle cell can become dedifferentiated before differentiating into different cells (e.g. cartilage, muscle, dermis)

Question 17

What are lineage-restricted blastema cells?

Answer 17

cells can only differentiate to the same type of cell

Question 18

What type of blastema cells are found in a salamander?

Answer 18

lineage-restricted blastema cells (however some can be multipotent

Question 19

What is an example of whole body regeneration?

Answer 19

Planaria - can regenerate from 1/279th of body (0.3%)

Question 20

What is the name given to adult stem cells in planaria?

Answer 20

neoblasts - they are scattered throughout the animal (pluripotent)

Question 21

What type of regenerative technique is involved in planaria head regeneration?

Answer 21

epimorphosis

Question 22

What type of regenerative technique is used to regenerate from small fragments that results in small animals?

Answer 22

morphallaxis

Question 23

What is the name given to adult stem cells in hydra?

Answer 23

interstitial cells

Question 24

How do interstitial cells in hydra reproduce?

Answer 24

budding

Question 25

If 20% of the ventricle of an adult zebrafish is removed, what would happen?

Answer 25

it would regrow

Question 26

Describe the process by which a zebrafish's heart would regrow?

Answer 26

1. wounding causes activation of the epicardium - a thin layer of cells that encapsulates the heart. 2. activated epicardium secretes retinoic acid, IGF2 and hedgehog signals. 3. cardiomyocytes (muscle cells) de-differentiate and proliferate at the wound site. 4. Vascularisation takes place & the regenerated cardiomyocytes become active.

Question 27

What are 4 features that humans can regenerate?

Answer 27

- bone - skin - muscle - liver