stem cells Flashcards
What are STEM CELLS?
Cells require genetic determination to develop and differentiate
Gene expression
Pre-existing mRNA
pre-existing proteins
The 4 main differentiated cell types found in the epithelial lining of the small intestine.
All highly specialised/differentiated.
Yellow arrow is direction of secretion/uptake of materials of each type of cell
Transmit amplifying cells
Stem cells in many tissues divide only rarely but give rise to transit amplifying cells-daughters committed to differentiation that go through limited series of rapid divisions before completing the process.
Eg. Each division gives rise to 8 terminally differentiated progeny
Stem-cell populations are established in ‘NICHES’
Specific locations that regulate participation in tissue generation, maintenance & repair.
Protects stem cells
Restricts ‘over-active’ stem cells from proliferating across organism
Maintained by genetic and physiological cues
What are the different types of stem cell?
adult - bone marrow, mostly multipotent
foetal - early differentiating organs, umbilical cord tissues
amniotic - free floating in amniotic fluid
stem cells in plants
meristems contain undifferentiated, dividing cells
Almost all plant tissues are totipotent
You can reconstitute a whole plant from only a few cells
Auxin
Cytokinin
How does the “Potency” of stem cells differ?
IPS cells
Induced pluripotent stem (iPS) cells:
Take Fibroblast cell from transgenic mouse
Mouse transgenic for Ab resistance gene linked to pluripotency gene promoter
Add genes to activate promoter
Select for cells with active promoter
Inject into embryos of normal mice
Cross chimaeric mice to normals
How can Stem Cells (or undifferentiated cells) be used?
Transformation
Therapeutics
Research(cell culture)
Tissue engineering
…organ growth
What is the molecular/cellular basis of cancer?
Unregulated proliferation of cells
No control to restrict numbers of cells
Tumour suppressor genes:
limit cell division
Promote cell death (apoptosis)
Oncogenes:
Encourage cell proliferation
“Gain of function” mutations
How can Stem Cells help in the fight vs cancer?
therapies for cancer:
Surgery-removal of the tumour and surrounding cells
Radiotherapy- target specific tissues to kill off rapidly dividing cells
Chemotherapy-chemical poisons to damage/inhibit rapidly dividing cells
Pharmaceuticals-block cell signalling or communication & interfere with genetic control
stem cells and cancer:
*Standard model for cancer formation is that all the tumour cells divide
*Stem Cell model suggests that only a small population of cells (the Stem Cells) divide
*Mutations in adult stem cells likely to be passed on to MORE cells than mutations in differentiated cells
*Tumour cells are less differentiated than other cell types, they are self-renewing and more resistant to apoptosis (just like adult stem cells)
*Many epithelial tumours are a result of mutations in adult stem cells
