Stem cells and stem cell therapies Flashcards
What is the definition of a stem cell?
Unspecialised cell with the ability to self-renew and the capability of differentiating into multiple cell types i.e. a cell that can divide many times and be instructed to differentiate into more than one type of cell
What are the different types of stem cells?
- Embryonic stem cells - (totipotent)
- Adult (somatic) stem cells - multipotent
- Induced pluripotent stem cells (IPSCs) - totipotent
What is the inner cell mass (ICM)?
Gives rise to the epiblast and hypoblast
epiblast gives rise to all cells in the adult
How are ES cells derived?
ES cells are cells of the inner cell mass must be amplified - small number of cells in inner cell mass
How are ES cells derived and amplified?
In feeder layer culture they divide indefinitely
Can be persuaded to differentiate into any of the 200 cell types in the body
Conditions needed for this are not yet known
In many media, more than one cell type is produced
What are pros of ES cells?
- Generate every cell type
- Grow in culture indefinitely
- Cells are young (telomere length)
What are cons of ES cells?
- Obtaining embryos is very difficult
- Amplification of cells from one embryo takes a long time
- Can differentiate incorrectly
- Formation of teratomas can happen
- Ethical issues
What are adult stem cells?
Found in post-natal tissues
Theoretically every cell in the body can have them
Used for tissue renewal/repair
Generally dormant or proliferate very slowly in situ
Limited potential i.e. neural stem cells = neurons and glia
How are adult stem cells derived and amplified?
Easy to harvest = skin
Hard to harvest = brain
Amplifying in culture is hard as they don’t proliferate very fast and its not indefinite
Differentiation has same basic issues as ES cells just with few derivatives
What are pros of adult stem cells?
Ability to harvest stem cells for an individual - reduces rejection
Limited potential decreases risk of teratomas forming or forming wrong cell type in situ
Few ethical concerns
What are cons of adult stem cells?
Hard to generate enough cells to be useful
Conditions to generate all possible cell types unknown
What are induced pluripotent stem cells?
Artificially created - involves reprogramming somatic cells to become ES cells - typically skin derived fibroblasts reprogrammed
What are pros of induced pluripotent stem cells?
Prove easy to amplify
Make all cell types
No ethical concerns
What are cons of induced pluripotent stem cells?
Not identical to ES cells (gene expression)
Have a shorter telomere length
What are problems associated with reprogramming somatic cells to become ES cells?
- iPS retain epigenetic profiles as those adult tissues from which they are derived
- iPS cells have significantly higher rates of cell death than ESC
- iPS cells prematurely age
- iPS cells generate an immune response causing a mouse to reject them even though the iPSCs were made from the cells of that mouse
