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11. regenerative biology 1 Flashcards

1
Q

why is the discovery of iPSC good for regenerative medicine?

A
  • there is a shortage of donors

- tissues can be made for patient - not immunosuppressant’s

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2
Q

what can damage tissue? (4)

A
  • trauma such as accidents
  • illness
  • removing tumours can damage surrounding tissue
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3
Q

what may we be able to do in the future in terms of people that are born without limbs?

A

correct their developmental program and use cell therapy to generate limb

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4
Q

there is a limit to how much regenerative experiments we can do on human cells. what do we not have that allows us to do more on human cells?

A

organoids

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5
Q

Salamanders have fights in the wild and bite off each other’s limbs off, what have they evolved?

A

a way to rapidly regernate limbs without blood loss, injection and cancer

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6
Q

what have we lots the ability to do and why may this be the case?

A

regernate limbs
>excess cells division runs the risk of cancer
>Urodele’s have decided during the course of evolution that this is worth the risk

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7
Q

how can salamander limb regeneration give us some idea about human limb regeneration?

A

they don’t seem to get cancer even though this would be a good site for tumour formation
>this may give us some ideas on how we can safely direct limb regeneration in humans
>it might also tell us that limb regernation is humans is too much of a cancer risk

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8
Q

is there an regeneration in mammals and what clinical application may this have?

A

yes, we may be able to enhance this clinically

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9
Q

how can 3D printed scaffolds be used in regenerative medicine?

A
  • you can print tissue and organs onto scaffolds

- you can print signalling onto scaffolds to direct stem cells how to behave

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10
Q

what is a potential way to cause regernation of a tissue in vivo? and what do you need to determine in order to do this? (3)

A

activate adult stem cells
>where to find stem cells
>how to activate the niche and get cells out of G0
>need to make sure you don’t deplete stem cells

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11
Q

what is a second potential way to cause regernation of a tissue in vivo?

A

use exogenous adult stem cells

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12
Q

what are MSC useful for?

A

they enter circulation and migrate to damaged tissue, they can release signals/chemicals/survival factors which rescue damaged tissue and modulate inflammation

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13
Q

what things do you need to consider when regenerating human tissue (6)

A
  • potential immune response (MHC profile)
  • risk of cancer
  • risk of infection
  • the delivery - how do you get cells where you want them
  • circulation for new tissue - add blood vessel progenitors?
  • how will biomaterial interact with patients tissue - might want to design them to degrade
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14
Q

you need to consider how the biomaterial will interact with the patients tissue, give an example of this

A

bones transplants ground against patients bones and caused damage

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15
Q

when a wound is made, what species specific decision is made?

A

whether to heal or regernate

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16
Q

why are fibrotic scars formed?

A

reduce blood loss, reduce the risk of infection and reduce the risk of cancer

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17
Q

humans tend to scar and not regenerate, what can other animals do?

A

slightly heal the wound and then start to regenerate

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18
Q

what can inhibit regernation and give an example (2)

A

> scarring can inhibit regeneration (physical barrier)
when spinal cord in humans is cut, nerve in theory could grow back but astrocyte scar don’t allow nerve to grow past
secreted proteins
astrocyte scars also release inhibitory factors

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19
Q

rebuilding a tissue requires more cell to be made, how is this done?

A

de-differentiation and re-entry into the cell cycle

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20
Q

what is compensatory hyperplasia and where does it occur in invertebrates?

A

> some cells will divide to compensate loss

  • blood vessels
  • liver
  • cardiac muscle (newts)
  • pancreas
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21
Q

there is strain specific variation in regeneration, describe this in terms of mouse ear hold punch

A

> two different strain had holes punched in their ears

>one strain can close the hole and the other cannot

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22
Q

what is the name for lizard like salamanders? and what does this include?

A

Urodele

>newts and axolotl

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23
Q

how are Urodeles special?

A

they are the only vertebrate that can almost perfectly replace lost/injured structure after metamorphosis from larval stage

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24
Q

what tissues can urodeles regernate?

A
  • limb
  • tail
  • spinal cored
  • heart ventricles
  • retina
  • lens
  • jaw
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25
Urodels have a range of different strategies for limb regerantion for different tissues, how can this also vary?
can vary with stage of development (larval/post-metamorphosis)
26
where can you amputate a Urodeles limb and still se regeration? how many times can this be done?
anywhere between the shoulder (proximal) and the hand (distal) >repeatedly
27
what is the initial wound response in Axolotl?
to avoid fluid loss and infection they form wound epithelium
28
once wound epithelium in Axolotl is formed, what happens?
``` reorganise ECM (upregulate MMPs) break down and remodel damaged tissue to allow access for cells that are going to going to regenerate limb ```
29
when does de-differentiation in the Axolotl start after amputation?
this starts a few minutes after amputation - cells near site de-differentiate, they migrate and proliferate under the wound epithelium
30
what is the blastema?
a mound of proliferating cells from which regernation will occur - cells start to re-differentiate to new limb
31
how might the new limb differ from the old one?
it may be shorter but will still function the same
32
what time frame after amputation is key for deciding start to re-differentiate to new limb?
24 hours
33
what type of cells are needed near the wound epithelium and what do they release?
macrophages | >anti-inflammatory cytokines and antifibrogenic cytokines
34
why are macrophages needed?
calm down inflammation and stop the laying down of fibrous ECM material (stop scarring)
35
what potential therapeutic could these macrophages be used for?
keloid scars are when people scar too much | >macrophages could be used to reduce scarring
36
what happens when there is late depletion of macrophages in a reforming Axolotl limb?
there is a bit of limb regernation as the blastema partly formed
37
what happens when there are nor macrophages in Axolotl?
there is no limb regeneration - fibrotic stump formed | >no TGF-β, MMPs or blastema
38
what is an important signalling pathway in salamander limb regeneration?
TGF-β - lack of this when macrophages are depleted may also contribute to lack of limb formation
39
name the two matrix metalloproteinase that are seen in salamander limb regeneration
MMP3 and MMP9 - lack of these means less fibrous ECM broken down (scaring)
40
define the blastema
de-differentiated mesenchymal cell at the end of the stump, generate the new limb
41
what did a paper published in nature 2009 do?
they re-examined blastema biology through GFP labelling in salamanders >they took labelled Axolotl cells and transplanted them into Axolotl limb >amputate limb to see how they contribute to blastema
42
what was the results from the paper published in nature 2009?
the donor cells could not go to the distal end of the limb, they hung around the more proximal regions of growing limb >cartilage contributes to the blastema >cartilage cells do not make muscle
43
how do cartilage contributes to the blastema ?
they hold information to direct differentiation of nearby cells - they tell certain cells where they are going to be in the new limb
44
why do cartilage cells do not make muscle?
they do not cross the lineage to be muscle cells
45
before this 2009 paper, what was the pervious dogma about the blastema?
that it is a homogeneous group of multipotent/pluripotent stem cells
46
what did the 2009 paper shows about the blastema that contradicted the dogma?
mixture of different mesenchymal progenitor cells covered by an epidermis >there is a little bit of trans-differentiation >but mostly cells maintain their lineage as they re-differentiate
47
from the 2009 paper, what is determined about de-differentiation?
cells had not completely de-differentiated - they maintain some lineage genomics >cells not re-programmed them back to pluripotency
48
do cells retain positional identity? do grafted cells remember where they came from and does this affect how they behave in the blastema? and how was this determined?
>cartilage-derived blastema cells do >Schwann cell-derived blastema do not and so can do anywhere in the regenerating limb >they looked at protein only expressed in upper arm in cells derived from upper arm which were grafted into blastema, this remained in cartilage and not in Schwann
49
name the protein that is only expressed in the upper arm of salamanders?
MEIS 112 protein
50
where can grafted Schwann cells go in the regenerating limb?
anywhere as they have forgotten their positional identity
51
where do grafted cartilage cells go in the regenerating limb?
they don't forget where they can from and so they will go back there - might be useful in giving position information to their surrounding
52
what sort of identity do cartilage cells have?
proximo-distal positional identity
53
what can be used to wipe out positional indentity in cells in the blastema?
thyroid hormone which acts via the retinoic acid receptor
54
in terms of where the wound is made, how much of the arm does it regernate?
makes limb structures distal to its site of origin - only makes whats needed
55
when will cartilage cells switch on MEIS and what is this part of?
they will only switch on MEIS after upper arm amputation, this is part of distal transformation
56
when will myogenic blastema derived cells expresses MEIS?
they will express it regardless of the amputation sites
57
considering when cartilage and muscle express MEIS, what can be suggested from this?
connective tissue could guide muscle development and regeneration - remembers where it came from and supports the cells around it to differentiate
58
describe muscle generation in Newts and how is this different from Axolotl
- newt myofibres de-differentiate, disassemble and form proliferation Pax7- cells (they have satellite cells but they don't use them) - axolotl myofibres don’t de-differentiate and they use Pax7+ satellite cells i. e. although evolutionarily close they regernate muscle differently
59
describe skeletal muscle
multi-nuclear fused myofibres
60
what happens to muscles after the age of 50, what can be taken from salamanders in this case?
>lose muscle strength and muscle stem cells start to behave less efficiently >looking at how salamanders regernate their limbs may give us some ideas on how to regenerate our own
61
skeletal muscle regeneration can occur after an amputation or disease, on a smaller scale when else can it occur?
during extreme exercise
62
how is muscle regernation different at different stages of the newt life?
in the larval form, they use stem cells | once they have undergone metamorphosis they de-differentiate to muscle myofibres
63
briefly describe how limb regernation occurs after amputation
the epithelial cells proliferate to cover the injured area and forma multiple layers apical cap. signalling from the regeneration regions initiate de-differentiation of mature cells followed by proliferation, growth and re-differentiation.
64
name so genes that are upregulated in the 24 hours after limb regernation in comparison to limb healing, and what implication does this have on humans?
cellular stress genes and chromatin remodellers >maybe in the human regerantion scenario we need to add chromatin remodellers to the pool of cells, can this be done safely?

SCRA (19 decks)

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