L08: Stem Cells Flashcards
What are the 2 ways a stem cell divides
Asymmetrically
Symmetrically
What does asymmetrical division of the stem cells result in
One 1 cell that is identical to parent and one slightly different cell
What does asymmetrical division occur in
Tissue maintenance
What does symmetrical division result in
2 identical daughter cells to parent cell
When is symmetrical division involved
Embryonic development for tissue expansion
At rest what state do stem cells sit in
Quiescent
What triggers the stem cells to divide
A signal
What happens to stem cells as they divide
Lose potency and differentiate
What determines how the stem cells divide i.e symmetrical or asymmetric
Stem cells niche
What is a stem cell niche
Components that sit outside the stem cells and produce signal e.g cytokines that signal to stem cell to divide
What is the similarity of embryonic stem cells and adult stem cell
Both have self renewal and capacity to differentiate
Where are adult stem cells derived form
Foetus
What is the role of the adult stem cells
Maintain organs throughout life
Where are embryonic cell stem derives from
Early embryos
What does embryonic stem cells not represent
A cell in the adult
What potential does embryonic stem cell give rise to
Every Cell types in the body
From 1 cell to 8 cell stage what is the potency of embryonic stem cells
Totipotent
What are the embryonic stem cells when the morula forms
Pluripotent
What can happen to the some of the cells in the inner cell mass
Stay pluripotent to form the gametes at the genital ridge
What does the inner cell mass form
The embryo
What does the outer cell mass from
The placenta
What 2 layers does the inner cell mass become
Epiblast
Hypoblast
What are the 3 important transcription factors to keep a cell pluripotent
Oct 4
Sox 2
Nanog
What happens to the stem cell when you add a cytokine called LIF
1) lif activates stat 3
2) stat 3 inhibits the differentiation of mesoderm and endoderm
What happens to stem cell when you ad BMP
1) BMP activates SMAD
2) SMAD inhibits the differentiation into the ectoderm
What does the epiblast differntiate into
Ectoderm
What does the hypoblast become
Endoderm
What occurs during gastrulation
1) primitive streak forms on the epiblast
2) cell of the epiblast migrate inwards and detach to slip beneath it, this is invagination
3) first cells invade the hypoblast and invade it to become the endoderm
4) remaining cells of the epiblast are known as the ectoderm
5) some of the invaginate epiblast cells remain in the space between the ectoderm and endoderm to form the mesoderm
What cells displace the hypoblast to become the endoderm
Epiblast
What cells from the mesoderm
Invaginate Epiblast
What is the cell migration from epiblast down to allow 3 germ layers formation (endoderm,mesoderm and ectoderm) governed by
Gene call FGF8
What does the FGF8 gene control the movement of cells by
Downregulating e-Cadherin
What are the challenges with stem cell therapy
- to produce sufficient numbers
- Ensure they are safely screened for no tumour formation
- Immune rejection
To get embryonic stem cell to differentiate what do we need to understand
The cytokine signals and at what time they are added
What happens when you ad activin A to an embryonic stem cell
Differentiation into endoderm
What happens to OCT4, SOX2, NANOG transcription factors if the cells differntiate into the endoderm
Become downregulated
What does mesenchymal stem cells have the ability to differentiate into
Adipocytes
Oligodendrocytes
Coroncytes
Therefore what can mesenchymal stem cells be used in
Supporting transplant to liver
Regenerate fading muscle
Help myocardial infarction where there is scaring of the heart
How do we stop immune rejection when we use stem cells
Via a patient specific pluripotent stem cell line
What are the 2 ways of inducing patient specific pluripotent stem line
- therapeutic cloning
- induced pluripotent stem cells
How does a patient specific pluripotent stem cell work via therepautic cloning
1) transfer a somatic cell nucles from a patient and transfer into a empty oocyte
2) trigger cell division
3) inner cell mass is removed at the blastocytes and can be cultures to make specific cells
Why doesn’t therepeutic cloning cause rejection
Because the embryonic cell is derived from the patients own somatic cells and therefore would not be rejected
Describe how an induced pluripotent stem cell works
1) you collects a differentiated cell from the patient
2) you reverse the differntiation by giving pluripotency inducing transcription factors of sox-2, cox4, c-myc, klf-4
3) this gives rise the induce pluripotent stem cells
What does totipotent mean
Capable of giving rise to any (mesoderm, ectoderm,endoderm) cell type plus extra embryonic cells (placenta) e.g zygote up 8 cell stage
What does pluripotent mean
Cell that can give rise to all cell types from the 3 germ layers (endoderm, ectoderm, mesoderm) that make up the body but not the placenta.
This is the inner cell mass of the blastocyst
What does multipotent mean
Cells that can develop into more than one cell type but are limited than pluripotent cells e.g adult stem cells are multipotent
What does unipotent mean
Cell that is able to differentiate into a single cell type e.g differentiated cells
What are the clinical uses of adult stem cells
Bone marrow transplant
Skin- skin grafting
Cartilaginous tissue bronchus replacement
