Module 7: Developmental Biology Flashcards
List the 4 different types of stem cells
- Totipotent
- Embryonic stem cells
- Adult stem cells
- Blastocyst
Discuss in detail: Totipotent stem cells
- lasts for about 2 weeks
- can differentiate into all body cells and extra-embryonic cells (umbilical cord, placenta)
Discuss in detail: Embryonic stem cells
- pluripotent ‘immortal’ cell that propagates indefinitely
- it is a cell that has the potential to differentiate into a cell of any germ layer
Discuss in detail: Adult stem cells
- grown up, not necessarily belonging to adults
- multi-potent, gives rise to limited cell types and do not divide indefinitely (age and lose regenerative potential)
e.g. haematopoietic lineage (blood stem cells)
~blood stem cells
~platelets
~white blood cells
~erythrocytes
Discuss in detail: Blastocyst stem cells
- inner cell mass
- trophectoderm
- pluripotent stem cells taken from inner cell mass
- blastocysts last for 2 weeks before attached to mother
Discuss other definitions of types of stem cells
- Autologous: stem cells from own body
- Allogenic: stem cells from donor
- Somatic stem cells: from body
Discuss how stem cell plasticity reduces over time
- stem cells don’t revert back to undifferentiated states after being committed to a lineage (unless artificially induced)
- e.g. lymphoid progenitor cells (immune system), myeloid progenitor cells (blood cells)
Discuss Blood therapies
- bone marrow stem cell transplant
- repopulate bone marrow after chemotherapy
Discuss Vision therapies
- cornea/epithelium can scar or retain water leading to loss of vision
- limbic system stem cell deficiency can cloud vision and lead to blindness
- new therapy, dispersed corneal cells cultured for 2 weeks on special substrates
~not as clear as the original limbic cells but ‘close enough’
Discuss skin therapies
- Human fibroblasts seeded
- Proliferate and full the scaffold
- Secret dermal collagen (etc. creating alive skin)
- Dermal matrix forms around scaffold
- Graft onto patient
List 7 overall points with regards to Generating pluripotent stem cells; the future of cloning
- Sources of pluripotent stem cells
- Somatic cell nuclear transfer (Dolly)
- World’s first primate cloned embryonic stem cells 2007
- Human induced pluripotent stem cells have been cloned
- there are some problems with induced pluripotent stem cells
- Transdifferentiation: the reprogramming of one cell type to another
- Human neural stem cells to induce functional myelination
Discuss in detail: Sources of pluripotent stem cells
- from IVF cells
- from blastocysts with or without cloning
- from foetus (foetal tissues, umbilical cord: only blood lineages)
- from adult tissue induced pluripotent stem cells
Discuss in detail: Somatic cell nuclear transfer (Dolly)
- Dolly the sheep was successfully cloned from a mammary somatic cell and a donor egg in 1996
~the nucleus is removed from an egg cell and replaced by a nucleus from a differentiated somatic (body) cell - the named her Dolly after Dolly Parton’s mammaries
- success rates are low in SCNT
- permission to clone using human embryos (autologous stem cells) limited in many countries (ethics)
Discuss in detail: The worlds first primate cloned embryonic stem cells (2007)
- humans cloned in 2013
- no need for eggs
Discuss in detail: problems with induced pluripotent stem cells
- low success
- choice of somatic cell may have pre-existing mutation (if mutations are trying to be cured)
- do transgenes cause mutations ?
- does reprogramming cause mutations?
