C1-HC5 Flashcards
There are 2 types of organoids:
Embryonic stem cell derived organoids
Somatic stem cells derived organoids
What are Embryonic stem cell derived organoids?
Embryonic stem cell derived organoids
○ You have stem cells (embryonic or induced pluripotent) and you force development from these embryonic stem cells to a tissue of interest in vitro. These embryonic stem cells have been grown for many years, just in a dish on feeder cells. Later they found out which signals were provided by these feeder cells and made a cocktail of these signals so the cells can grow without this feeder cells.
○ Chimeric mice experiment: People took embryonic cells from a white mouse and injected these into a blastocyst of a black mouse. The embryonic stem cells start to mix with the other cells of the inner cell mass. What you get is a chimera (black-white colour coat).
Embryonic stem cells can still make everything, to they are really pluripotent!!
Mini organs:
Represent the fetal stage of an organ. Even very complex structures can be made.
Made from embryonic stem cells.
4 characteristics of intestinal stem cells:
Characteristics of intestinal stem cells:
- Intestinal stem cells are not quiescent (‘rustig’); they divide frequently (every 22 h).
- They are not rare: up to 5% of crypt cells
- They do not divide asymmetrically: when a stem cell divides, you get 2 stem cells. This is also called competition for their niche cells.
- The stem cell hierarchy is not uni-directional:
○ When LGR5 stem cells divides and one of the cells actually starts to differentiate, the moment you would damage all the stem cells, these cells that are on their way to specialize can become stem cells again > gives robustness to the intestinal epithelium (when you damage stem cells, there are always cells that can take over the function).
What is the Wnt pathway and where is it expressed?
Wnt pathway:
- Pathway that drives development, and self-renewal.
- Wnt is expressed in:
○ Paneth cells
○ Transit amplifying cells: these cells are thought to be able to divide a few times before they are fully differentiated.
○ Crypt base columnar cells.
3 characteristics of stem cells:
Characteristics:
- Stem cells are functionally defined.
- Multipotent: the capacity to make all the different cell types.
- Longevity: the cells are there as long as the animal lives
What are Paneth cells?
Paneth cells are highly specialized secretory epithelial cells located in the small intestinal crypts of Lieberkühn
What is the process: Neutral drift towards clonality.
Neutral drift towards clonality.
Steps: there is a restricted niche space for stem cells: the purple stem cell divides (symmetrically), but there is not enough space for all the cells, so random, one of the other cells will be pushed out. This is a continuous process (cells divide every 24 h).
It is a very robust system and it is a very well developed system to maintain the integrity of the most fit stem cell.
Pro’s of organoids:
Pro’s of organoids:
- Unlimited expansion: grow as long as you want (especially for mouse intestinal organoids)
○ This is not the case for the liver. This may be due to not yet optimal growth factor conditions or that the epigenetic makeup is these cells is different from the intestinal stem cells.
- Non-transformed: no additional factors are added to keep them in their pluripotent state. They are held in this proliferative state by the niche factors.
- Genetically stable
- Cryo-conservation: freeze them in liquid nitrogen and store for a few years.
- Single cell cloning
- Phenotypically stable
Epithelial organoid cultures have been derived from many tissues of murine and human origin. Name three of these tissues.
Possible answers: (o)esophagus, colon & rectum, liver, pancreas, salivary gland, skin (epidermis), small intestine, stomach, taste buds, fallopian tube, mammary gland, prostate, lung
