12. regenerative biology 2 Flashcards

1
Q

what was discovered in 2001?

A

that there soluble factors in serum that are important for muscle regernation - particularly in re-entry to the cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how do you get more proliferation when growing muscle cells in culture?

A

plate them at low density - this way they are not contact inhibited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is required for de-differentiation regeneration of myofibres in vivo in newts? and why is this?

A

direct clipping - cutting off the end of fibres
- they need to be physically damaged to trigger cell cycle re-entry
>need to trigger start of programmed cell death in order to regenerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what happens when newt skeletal muscle is fragmented (breaking up of multinuclear structure)?

A

programmed cell death response - involves caspase response, this may act on cells or be released from cell (they are not sure)
>from this, this paper were able to get terminally differentiated skeletal muscle cells into regernative progenitors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens when skeletal muscle cells are injured?

A

most of them will die

>some don’t die and re-enter cell cycle and de-differentiate and contribute to regenerating muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what two things do axolotl regernating limbs need to do in order for there to be cell cycle re-entry by differentiated cells ?

A

> trigger a programmed cell death response

>down regulate TS p53

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

if p53 is not down regulated what happens?

A

cell cycle re-entry cannot be triggered = no regeneration/impaired regeneration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why do we not want to interfere with p53 in humans?

A

it is regarded as the ‘guardian of the genome’ - interfering with this will lead to cancer
>this may be one of the reason why we cannot regenerate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

a paper want to see what pushed myotubules to divide, what did they do? what protein did they identify?

A

screened blastema secreted proteins for effects on division of cultures myotubes
- to see how salamanders re-enter the cell cycle safely
>MLP (MARKS-like protein)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what did they do to show that MLP is important during regernation?

A
  • did a big cloning screen
  • saw the effect on dissociated cells
  • purified active protein
  • made antibodies to see where it was
  • KO
  • added it ectopically
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

MLP is very good at inducing the blastema. what can it induce?

A

significant increase in length of blastema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what was seen when anti-MLP was used to block it affect in a wide range of regernating tissues?

A

blocking it has an affect on dividing nuclei - MLP upregulates division
>this shows it is widely used in axolotl to regenerate tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is it proposed that the ‘serum factor’ may do?

A

this might P Rb allowing it to release E2F and drive proliferation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what do we know about the S phase re-entry factor in serum?

A

it is being cleaved by thrombin - serum and thrombin can trigger cell cycle re-entry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

is thrombin cleaving a factor in the serum or on the cells? and how was this determined?

A

thrombin cleaves something in the serum
>pre-incubate the serum with thrombin, inhibit thrombin then treat cells with the serum - this was shown to trigger cell cycle re-entry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what can the S phase re-entry factor also stimulate cell cycle in?

A

newt iris pigmented epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what might being able to identify this S-phase cell cycle re-entry factor determine?

A

why salamanders can re-grow limbs and we cannot

>may also allow for us to do mammalian regernation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

mouse muscle cell line was treated with serum or newt blastema extract, what happened?

A

cells immediately upregulated genes like fos and c-myc, left G0 and entered G1
>they resist entry into cell cycle and do not enter S phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

some people are born without limbs, what might we want to be able to do?

A

kick start embryonic development in that part of the body again

20
Q

how does embryonic development in salamander differ from regeneration?

A

> embryonic development doesn’t need nerves

>blastema division and growths needs nerves (depends on nerve derived factors)

21
Q

what can be used to induce ectopic limbs in salamanders?

A

re-direct the nerve, damage the tissue and the nerve will generate a limb to grow in a ectopic position

22
Q

what are some of the nerve derived factors? and what implication does this have on humans?

A

BMP and FGF drive blastema cell proliferation

>we will need to think about nerve derived factors if we ever get to this stage in humans.

23
Q

what protein sets up a proximodistal gradient and what is this set up by?

A

Prod1 - this is set up by MEIS

24
Q

where is Prod1 found?

A

only in salamanders not in humans

25
what does Prod1 do?
- it binds nAG and can interact with EGFR - this stimulates S cell entry - and induces MMP9
26
what natural regernation occurs in mammals?
very limited ability to regenerate lost/damaged tissue or heal without scarring
27
what do mammals do that Urodeles don't?
scar
28
why might we not regenerate? (4)
- don't want to down regulate TS - our circulation is under high pressure and so want strong healing response - we have a very mature immune system - we have a scarring response
29
what might it be hard to introduce a bioscaffold into?
the hostile environment of regeneration
30
name two types of animals that have lots of division in their brain postnatally
fish and salamanders - can regernate lots of their brain
31
what is seen in the brain of zebrafish?
self-renew neural precursor cells throughout brain - these use different TF from embryonic development
32
which neurones die is Parkinsons?
DN - these neurons die and drive the shaking and inability to move
33
what happens when of midbrain dopamine neurons in newts are ablated? and what is a key component in this? and how does this compare to embryonic development?
this induces NSC in the normally quiescent midbrain to proliferate and undertake full DN regulation >Shh signalling >this is similar to embryonic development
34
even injury is not enough to re-activate neuogenic genes that are epigentically switches off. describe why most of the mammalian brain cant regenerate?
>injury induced to the brain >proliferation and recruitment of glia around injury but no neurogenesis >glia induces olig2 expression >this supresses neurogenesis
35
what can be inhibited to allow neurogenesis in mice the brain? and what implication may this have on therapy?
olig2 >when people have a stroke you can get into the area and safely get cells to make new neurones (currently v restricted by epigenetics)
36
describe Deer antler regeneration
``` every year the males generate antlers >this is stem cell based >they don't get cancer >doesn't need nerves >the large casting wounds don't scar ```
37
what type of mice have amazing skin regernation, and what could this be applied to?
African spiny mouse >these mice can loose chucks of their skin and regrow them (most other mice would scar/die) >this includes regernation of hair follicles, sebaceous glands, dermis and cartilage >in dorsal and ear >this could be applied to burns victims
38
what is the only part of mature mammalian limb to regenerate? and what does this require?
fingertip | >the nail be needs to be intact
39
describe new fingertips that are made in mammals
they are shorter but have minimal scaring | >this process does not always work perfectly
40
does the regeneration come from stem cells/already committed progenitors after fingertip amputation in mice?
lineage restricted and not pluripotent stem cell activity (cells are not completely de-differentiated) >ectoderm contributes to epidermis, nail and sweat glands and not to mesoderm tissue
41
the activation of what in the nail epithelium couples nail growth to digit regernation? and what happens when this is KO?
Wnt signalling | >don’t get fingertip regeneration
42
why do we need the nail bed for fingertip regernation?
Wnt responsive stem cells are present
43
in addition to stem cells which respond to Wnt, what else is there in the fingertip blastema?
some committed progenitors
44
what can we learn from natural regernation? (6)
- understand the wound healing regernation switch - how to prevent scars - understand how to control endogenous cells division and de-differentiation, and their re-differentiation - including positional identify - nerve dependency - understand how to make the local environment permissive for regeneration
45
in order to allow regernation in humans what will we need to do in this 24 hours period after wound?
remove factors that are blocking regeneration
46
what is the argument that challenges the want for humans tissue regernation?
we will be able to develop better prosthetics to challenge regeneration anyways so why bother with further regenerative research.