Stem Cells Flashcards
Describe the 3 features of stem cells
- state potency
- Undifferentiated and unspecialised cells: no tissue-specific structures for tissue-specific functions
- Capable of extensive proliferation and self-renewal via mitosis
- Upon receiving appropriate mlc signals→ differential gene expression→ differentiate into various specialised cell types
Describe symmetrical division and its purpose
Symmetrical division: produce 2 daughter stem cells w the same differentiation potential as parent cell → maintains pool of stem cells for further division
Describe asymmetrical division and its purpose
When SC stimulated by mlc signals for differentiation: produce…
- 1 daughter stem cell→ maintains pool of SC for further division
- 1 progenitor daughter cell→ to increase or renew population of specialised cells in a specific tissue
How are SC able to differentiate?/What accounts for the diff in characteristics?
Mlc signal (e.g. growth factors/hormones)→ signal transduction→ response: differential gene expression, where some specific genes are expressed, others not expressed→ synthesis of tissue-specific proteins→ specialised functions
Define/What is the function of totipotent SCs?
Can differentiate into all cell types making up organism, including extra-embryonic tissue like placenta
- Can form entire organism
Define/What is the function of pluripotent SCs?
Can differentiate into all cell types making up organism, except extra-embryonic tissue like placenta
- It alone cannot form entire organism as placenta needed for foetal nourishment/ development
Define/What is the function of multipotent SCs?
Can differentiate into several related cell types, but far fewer types than pluripotent embryonic SC
What is the source for totipotent SCs?
- Zygotic SC from fertilised egg/zygote
- Cells produced within the first 3 division (8 cell stage) after egg is fertilised
What is the source for pluripotent SCs?
Embryonic SC from inner cell mass of blastocyst
What is the source for multipotent SCs?
- *Blood/Haematopoietic SC from bone marrow: can differentiate in all types of blood cells
- Neural SC: differentiate into nerve/neural supporting cells
Explain the normal functions of stem cells in a living organism, giving an example
- Self-renewal→ ensure constant pool of SC
- Differentiate into specialised cells→ Growth and development
- Differentiate into specialised cells→ Regenerate cells lost (due to cell death and injury)
- E.g. Blood/haematopoietic SC in bone marrow: blood is a tissue containing many diff specialised cells. Haematopoietic SC constantly proliferate and differentiate into various specialised blood cell types to replace those lost through normal cell death→ maintains immune and transport function of blood
What are the 2 methods for stem cell therapy?
- Remove all existing haematopoietic SC from body→ transplant h. SC/adult neural SCs from normal, healthy bone marrow donors
- Remove SC from patient & modify its genome by inserting a normal, functional allele (e.g. viral vector)→ reintroduce modified SC
What are the advantages of SC therapy?
- Multipotent adults SC can differentiate into → restore function of damaged/diseased
- Self-renewing SC→ transplanted SC can constantly replicate in patient to maintain a constant pool of SC→ no need for repeated transplants-
What are the arguments against using embryonic SC?
- Embryo has the status of a human. Embryonic SC research violates the sanctity of life and is tantamount to murder
- Current benign applications may lead to abuse in the future. Once human status is denied to embryos, this precedent may extend to other categories of human beings such as the profoundly disabled or the elderly infirm
- Takes a purely utilitarian view of the embryo: just a source of spare parts
- Possibility of unforeseen consequences in treated patients: possible risks of tumour formation, immunological reactions, unexpected behaviour of the cells, and unknown long-term health effects
What are the arguments for using embryonic SC?
- Embryos are not equivalent to human life:
> Embryos not conscious, cannot feel, cannot survive outside the womb.
> Blastocysts are a cluster of human cells that have not differentiated into distinct organ tissue, making cells of the inner cell mass no more “human” than a skin cell. - Surplus embryos created via in vitro fertilisation are destroyed/stored for long periods of time past their viable storage life. These can be used for creating new SCs lines for research which would otherwise be destroyed.
- Existing SC lines that can be used, instead of destroying new human embryos to establish new SC lines
- Can potentially treat a wide range of diseases: potential to grow indefinitely in lab env + can differentiate into almost all types of bodily tissue
