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Extensive summary of all 5 lectures. Note: For the very last lecture, the last part concerning treatment of junctional EB is not very clearly summarized.
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Exam preparation Trends in Stem Cell BiologyExam date: 27 October 2020
Table of Contents
Lecture 1 – Pluripotency ................................................................................................................................. 2
Lecture 2 – Reprogramming .......................................................................................................................... 10
Lecture 3 – Neurobiology .............................................................................................................................. 21
Lecture 4 – Hematopoietic stem cells ............................................................................................................ 31
Lecture 5 – Epidermal stem cells in treatment............................................................................................... 43
,Lecture 1 – Pluripotency
Epigenetics and Pluripotency in mouse embryonic stem cells
What are Stem Cells?
Stem Cells are biological cells that can differentiate into other types of cells and can
divide to produce more of the same type of stem cells (self-renewal),
Thus, key aspects of stem cells:
1. Differentiation
2. Self-renewal
In mammals, there are two broad types of stem cells:
1. Embryonic stem cells (ESCs) à which are isolated from the inner cell mass of
blastocysts
2. Adult stem cells
1. Different forms of cell potency during development in vivo
- Totipotent state: Single cell that can develop into everything
- Pluripotent state: Cell can form ecto-, meso- and endoderm
o E.g. the inner cell mass, which already contains two defined,
irreversible cell populations.
During embryonic development, cells lose their potency. This can be mimicked in a
culture dish (in vitro):
2
,Potency is graphically reflected by the Waddington’s landscape:
The following question arises: Is canalization of development driven by genetic or
epigenetic factors? à Epigenetic factors mainly drive embryonic development,
since the genome is quite stable and does not really change anymore.
Conclusion: cells lose their potency during in vivo development.
2. Different pluripotent cells in vitro (from mice):
There are five different types of pluripotent cells:
1. Embryonic Stem Cells (ESCs)
2. Embryonal Carcinoma Cells (ECs)
3. Embryonic Germ Cells (EGCs)
4. Epiblast stem cells (EpiSCs; primed ES cells)
5. Induced Pluripotent Stem Cells (iPSCs)
Pluripotency is only a transient state within an embryo.
ESCs are a culture phenomenon à being able to capture cells in a particular state,
in tissue culture.
Characteristics of pluripotency:
1. They can still form every cell in an organism (ecto-, meso-, endoderm)
2. Self-renewal
How to test for pluripotency?
In mice:
- Multilineage differentiation in vitro/vivo (germline colonization)
- Clonogenicity
- Extensive proliferation in vitro under well-defined culture conditions
- Known marker genes/proteins (Oct4, Nanog, Sox2, SSEA, etc.)
- Normal stable karyotype
3
, In practice of absolute proof – in mice:
- Check if they contribute to all somatic lineages/produce germ line (chimerism)
- Check if they form teratomas (benign)
In human:
- Multilineage differentiation in vitro (NOT in vivo à ethical issues)
- Clonogenicity
- Extensive proliferation in vitro under well-defined culture conditions
- Known marker genes/proteins (Oct4, Nanog, Sox2, SSEA, etc.)
- Normal, stable karyotype
In practice of absolute proof – in human:
- You cannot check for contribution to all somatic lineages/germ line production
(chimerism) & teratoma development à ethical issues. Therefore, these things
are investigated in mice.
Conclusion: ES cells, like some other in vitro cells, are pluripotent.
3. Application of ES cells:
Why are ESCs so interesting?
- ES cells are the only cells that will form the complete body.
o Pluripotency, self-renewal
Applications:
Model for embryonic development:
- Regenerative medicine (grow in
large quantities + differentiate – see
image on right)
- Generation of KO-mouse
- Disease model (because
differentiate into desired
specialization)
- Cytotoxicity tests (especially during
pregnancy, for foetus)
Ethical concern that arises: can we use
human ESCs?
4
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