L9 Regenerative biology Flashcards
What is regenerative biology?
Regeneration is the ability of organisms to restore damaged or diseased structures in form and function.
Which vertebrates have more regenerative capabilities aquatic or terrestrial?
Aquatic vertebrates have more regenerative capabilities than terrestrial vertebrates (limb, eye, spinal cord, heart).
Which organisms have the ability to regenerate the whole body?
Simple organisms like planarian, hydra, and starfish.
What is morpholaxis?
Morpholaxis is a form of regeneration in which a lost body part is regenerated by remodeling existing tissues, rather than by growing new ones
Eg. hydra
What is epimorphosis?
Epimorphosis is a process of rebuilding a lost structure through active cell growth and differentiation.
Eg. salmander l
What are the signals caused by early wound?
- ATP is released by damaged cells.
- Intracellular calcium is elevated.
- Reactive oxygen (H2O2) is released.
These molecules act as signals over the first few minutes to initiate the wound response
Explain the process of wound response (3)
Wound response:
1. Causes cytoskeletal change to close the wound. The cells on the edge will form “purse strings” to close the wound if its small enough
- Recruits immune cells to the site
- Initiates regeneration or scar formation depending upon the regenrative capabilities.
What is fibrosis (Scarring)?
Fibrosis (scarring) is permanent and caused when fibroblasts secrete high levels of extracellular matrix (collagens etc).
What are the steps in salamander regeneration? (4)
- Amputation - Early wound signals
- Wound closure - Cytoskeletal rearrangement and epithelial movement.
- Wound epithelium - Signalling from wound epithelium inducing dedifferentiation.
- Blastema - Blastema cells proliferate then regrowth begins.
What is the first sign of salamander regeneration?
The formation of the wound epithelium is the first sign that regeneration has begun.
What are the features of wound epithelium?
Wound epithelium is thicker than the surrounding skin and is known to secrete signals. The formation of the wound epithelium is the first sign that regeneration has begun.
What is the difference between wound epithelium and blastema?
Wound epithelium is similar to the AER and the blastema is similar to the progress zone.
Regeneration recapitulates development
What are the two hypotheses for formation of blastema cells?
- Multipotent blastema cells - Muscle to a single proliferative cell which further develops to cartilage, muscle or dermis cells.
- Lineage restricted blastema cells - cartilage, muscle and dermis develop 3 individual proliferative cells into individual seperate cells.
What is a blastema?
A blastema is essentially a mass of undifferentiated cells that forms at a wound site.
These cells have the remarkable ability to develop into the various tissues required to regenerate a lost body part
Which are the only two cells that transdifferentiate?
Only dermis and cartilage.
What is the minimum size of fragment of planaria that can regenrate?
Planaria - flatworms
The minimum size of fragment that can regenerate is 1/279th (0.3%)
What are neoblasts?
Neoblasts are the adult stem cell of planaria and are scattered through out the animal
What are the regenerative features of planaria?
Neoblasts are the adult stem cells of planaria
Some neoblasts are pluripotent, others are lineage restricted.
Head regeneration involves epimorphosis
Regeneration from small fragments results in small animals – morphallaxis
What are the features of hydra in cell arrangement?
Simple animal with two germ layers and adult stem cells called interstitial cells
They are continually growing due to the interstitial cells and reproduce by budding
Is cell division and interstitial cells needed for regeneration in hydra?
No - Cell division and the interstitial cells are not required for regeneration -> morphallaxis.
What is the limit for zebrafish heart to regrow?
If 20% of the ventricle of an adult zebrafish heart is removed it will regrow.
List the steps of zebrafish heart regenration
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 and the regenerated cardiomyocytes become active.
What is vascularisation?
Vascularization refers to the process of forming blood vessels within a tissue or organ
Which parts of the human body can regenrate?
Bones in small quantites, skin can regenerate after heavy damage as well, muscle growth is limited and liver can regrow as well in limited quantities compared to zebrafish and other vertebrates.
What is BMP2?
BMP2 soaked beads induce skeletal regeneration from digit and limb amputations.
What is BMP?
BMP is a ligand that is important during skeletal development
Development and regeneration use the same set of genes
This slide is that verterbrates use the sam egeense required for development in a wat to regenrate themeselves but we as mammals eventhough we hav ethose genes we are not able to use them for regeneration.
This suggests that mammals could regenerate if only scientists could figure out how to activate the regeneration program
