Lecture 5 Flashcards
What are stem cells ? Only present in what kind of organisms ?
unspecialized cells that can divide to produce more stem cells or differentiate into other cell types.
Only present in multicellular organisms
why are stem cells important ?
they replace tissue-specialized cells in case of :
- damage
- normal tissue turnover
How is the stem cell pool maintained ? (two ways)
1) self-renewal by symmetrical division (expansion of pool)
2) asymmetrical division : one daughter cell remains a stem cell for maintenance, the other differentiates
What are the 2 types of asymmetrical division?
1) Divisional
2) environmental : environment stimulates the differentiation
what is a stem cell niche ? and its roles ?
specific microenvironment that comprises the signals that maintain cells, regulate self-renewal and differentiation.
It provides a sheltering environment and safeguards against excessive stem cell production (can lead to cancer)
What are the two types of niche that coexist ?
quiescent storage niche and self-renewing niche
3 ways used by niche to regulate cells
direct contact, release of soluble factors, regulate function of intermediate cell (f.ex immune cells)
6 types of signals that regulate stem cell fate
1)interaction with other cells
2) inflammation (immune cells)
3) hypoxia and metabolism (ex circadian rhythm)
4) physical properties (stiffnedd of substrate f.ex)
5) ECM proteins
6) secreted factors (cytokines, growth factors, hormones, …)
cite the five cell types in the stem cell hierarchy
1) totipotent -> form complete organism (only in morula)
2) pluripotent -> form all cell types in human body (only in blastocyte)
3) multipotent -> form a nb of cell types
4) progenitor -> form cells of one specific tissue (they are present in every organ)
What are embryonic stem cells ? 4 derms ? Advantages and disadvantages ?
From blastocyte (pluripotent) -> can form ectoderm, endoderm, mesoderm, germ line.
Adv : abundant, can form any tissue (some are easy to generate), can be propagated indefinitely.
Dis : ethical / religious concerns, high chance of transformation into cancer (teratoma), immunological rejection, in vitro instability
What are induced pluripotent cells ? what can they form ? + and - ?
they are reprogrammed somatic (differentiated) cells. They can form the 3 derm lines but not the germ line.
+ : no ethical concern or rejection, can be used for regenerative medicine or drug screening
- : slow and inefficient reprogramming protocols
What does reprogramming mean ?
use reprogramming factors to activate certain genes
What are adult stem cells ? what needs to be done before we can use them ? Careful about what ?
multipotent and progenitor.
They need to be expanded ! (because they are rare)
Careful to not expand too much because it can cause a loss of regenerative properties.
advantages of adult stem cells (5)
1) no ethical concern
2) good differentiation potential
3) not immunogenic (same person)
4) easy procurement
5) not tumorigenic
What are HSC ?
hematopoietic stem cells -> all blood cells depending on which marker is expressed
