Adult stem cells Flashcards
Where are embryonic stem cells found?
In the BLASTOCYST
Where are tissue stem cells found?
Fetus, baby and throughout life (adult stem cells)
What potency does the zygote have?
TOTIpotent
What happens to the cells of the blastocyst at the 32-cell stage?
Cells on the OUTSIDE acquire different fates to the cells on the INSIDE
What do the cells on the outside of the blastocyst become?
What does this give rise to?
TROPHECTODERM
Gives rise to the placenta
What do the cells on the inside of the blastocyst do?
What do they become?
- Start to pull away from the trophectoderm and cluster together
Forms:
- The inner cell mass, which forms the embryo
What are ES cells?
EMBRYONIC stem cells:
- Cells of the inner cell mass of the blastocyst stage embryo
What the ES cells do when cultured in a dish?
1) To grow MORE cells (self-renew)
2) Can DIFFERENTIATE into a specialised cell type
What causes the ES cells in culture to differentiate?
Exposure of the cells to an array of factors (known about through study of embryogenesis)
What is the use of ES cells useful for?
What is the use not useful for?
Useful as:
- A TOOL for the study of specific cell populations (for drug screening)
Not useful as:
- REGENERATIVE medicine - ES cells are from NON-host tissue (rejection)
What is a stem cell?
A cell which has ENDLESS RENEWAL - forming a daughter cell that looks exactly like the mother
A cell which can differentiate into multiple lineages/fates to a specialised cell type (HIGH potency)
What forms a progenitor cell?
How is it different to a stem cell?
A stem cell restricting its fate
Different to a stem cell:
- Limited self-renewal
- Limited potency/differentiation
Why is self-renewal of stem cells needed?
To MAINTAIN the stem cell pool (don’t run out)
How do stem cells self-renew?
Every cell division occurs asymmetrically:
- Retains one stem cell
- Forms one specialised cell
Why is differentiation of stem cells needed?
- To REPLACE the dead/damaged cells throughout your lifetime
OR
- To ADD new cells - increasing organ size or generating cell types that are specifically needed at a CERTAIN TIME in life
Describe the balance between self-renewal and differentiation of stem cells
CHANGES throughout lifetime:
In the embryo - LOTS of differentiation
Once body built - Less differentiation
Why does the amount of stem cells decrease from the embyro to the adult body?
- In the embyro - lots of differentiation to build body tissues etc, so need lots of stem cells
- In the adult body - only REGENERATION (less stem cells)
What are adult/tissue specific stem cells?
What do they produce? Why?
- MULTIPOTENT stem cells that are retained in each body tissue in order to maintain the body tissue throughout life
- Produce specialised, differentiated somatic cells (as differentiated cells DO NOT divide) - within their specific cell lineage
What happens to a cell when it is in a differentiated state?
No longer mitotic - G0
How are multipotent adult stem cells protected?
In specialised niches in many organs
What is cellular homeostasis?
The BALANCE between stem cells and differentiated cells
The constant/periodic generation of NEW cells to replace the old, damaged and dying cells
What is the differentiation state of an adult stem cell?
Partially differentiated
What 3 roles do adult stem cells play a role in?
1) Maintaining cell populations
2) Help to heal
3) Role in aging
Describe the balance of cellular homeostasis?
- Every cell lost –> need to gain ONE
BUT, this changes throughout life, eg:
- Growth
- Pregnant females - produce more RBC
What mechanisms that control if ASCs are going to self renew or differentiate similar to?
The control mechanisms that build the embyro
What are 5 types of adult stem cells?
1) Hematopoietic
2) Mesenchymal
3) Epithelial
4) Muscle
5) Neural