Intro to Stem Cells and Regeneration Flashcards
What are the criteria for being a stem cell?
Stem cells can self-renew and differentiate
Define self-renewing
When stem cell divides and the cell retains all of its existing properties = remaining in undifferentiated state
Define differentiation
When a stem cell receive a signal from the environment it responds by expressing a certain set of genes
This happens in a stable manner, so that when the env signal is removed the genes stay being expressed
What type of division do stem cells go through?
Asymmetrical division 80% of the time
20% can be other things such as symmetrical division
How can we tell if a cell is a stem cell?
Most of the time it is impossible
But we can go based of the criteria
Define potency
The ability of ANY cell to differentiate
Define totipotent
A cell that can give rise to EVERY cell
Define pluripotent
A cell that can give rise to make all SOMATIC cells and 3 germ layers
(but not extaembryonic cells or cannot give rise to a whole organism)
What can pluripotent cells not give rise to?
Extraembryonic tissue or an ENTIRE organism
(The cell may be able to make every cell in that organism though)
When does potency become restricted?
With developmental age and tissue restriction
What is an embryonic stem cell?
Derived from the inner cell mass of blastocysts
AND
Maintained indefinitely in vitro
What are the 3 characteristics of embyonic stem cells?***
Pluripotent = can make all germ layers
Fast cycling (peculiar cell cycle)
Symmetrically expanding
What are somatic stem cells?
Also known as adult stem cells, are found in many tissues throughout the body
(while embryonic stem cells are found in embryos)
What are the characteristics of somatic stem cells?
Rare (uncommon)
Slow cell cycle
Both (a)symmatric cell division
Unspecialised
Why are somatic stem cells unspecialised?
They do not do most of the work in that tissue because are not specialised to fulfil that specific function
What is regeneration?
Homeostasis & repair
Tissues with natural turnover (blood, skin, etc..)
Does regenration need stem cells?
No
How does regeneration occur in the mucsle?
Satellite cells merge with myofibres after damage and can help it repair
So stem cells are known as “reserve cells” for injury repair
Why do different organism have different regerneation potential?
Because they have different genetics
What is lineage restriction? ***
Is the biological process where developing cells progressively lose their ability to differentiate into multiple cell types and become committed to a specific lineage or fate, ensuring the formation of specialized cell types during development
What experiment looked into axolotl regeneration?
Created a fluorescent axolotl
Transplanted different tissues into non-fluorescent axolotl
Damaged the recipient to see how transplanted cells respond
What ages were the fluorescent axolotl cells transplanted?
Either embryo stage or adult
Conclusion of axolotl regeneration?
Complete dedifferentiation into a pluripotent cell is NOT needed for limb regeneration
The transplanted cells dedifferentiated to a blastema = heterogeneous colection of restricted progenitor cells
This means the cells stay in their own lineage
Example: if they transplanted skin them amputated, the cells only contributed to the skin not all tissues
What are the two theories of the lineage of stem cells?***
They come from the 3 primary germ layers (more true)
OR
Stem cells are set aside early on in development as a special pool of cells (no evidence of this)
What is stemness?
Concept that stem cells share common characteristics
Meaning they may share transcriptional profiles
What technique was used to look for stemness?
Microarrays to compare ESC, HSC and NPC with differentiated cells of the same lineage
Microarray = lab tool that analyse expression of genes or proteins
What genes did they find in common between the different stem cells?
The genes that allows stem cells to be metabolically active
