6/ stem cell niche Flashcards
mesenchymal stem cells form..
- bone cells (made from osteoblasts)
- cartilage cells (chondrocytes)
- fat cells (adipocytes)
what do blood stem cells make
red blood cells, white blood cells, platelets
what do satellite stem cells make
muscle
what do germ stem cells make
oocytes and sperm
whats the term for the environment adult stem cells are found in
niche
classical stem cell division
- stem cell divides - one replacement and one differentiated cell
what term is for stem cells dividing to form 2 more stem cells
transit-amplifying
3 ways of division, population asymmetry in stem cells and % of outcomes
- 8%: stem cell divides to form 2 stem cells
- 84%: stem cell divides to form one stem cell and one differentiated cell
- 8%: stem cell divides and both daughters differentiate
3 main skin layers
epidermis, dermis and subcutis
epidermis made up of
keratinocytes
what does the dermis contain
fibroblasts and blood vessels
what stimulates keratinocyte proliferations
signals from the dermis and BM
proliferation and differentiation from BM to outer layer of dead cells
- basal keratinocytes are stem cells
- divide to produce daughter cells that move up and continue to divide
- cells produce different keratins as they move towards the surface (markers to study cells)
- at skin surface daughter cells die
signals regulating the basal stem cell niche
- Wnt signals from dermis inhibit differentiation (maintain stem cell pop)
- integrins hold cells to BM, keep recieveing signal from wnt preventing differentiation (maintain stem cell pop)
- notch signals in maturing keratinocytes inhibit integrins (more differentiation)
- EGF inhibits notch (maintain stem cell pop)
additional stem cell niches in the hair follicle and what this suggests
- bulge: in extreme damage, contribute to epidermis and sebaceous glands
- different stem cell niches can provide cells after serious damage
- dermal papilla additional niche at base of follicle
junctional epidermolysis bullosa JEB - caused by, mutation, burn patients, extension to JEB
- Adhesion between dermis and epidermis impaired
- mutations in adhesion genes like LAMB3
- basal keratinocytes can be cultures from a patient and used to replace skin after burns
- culture cells from JEB patients, replace damaged gene, grow basal keratinocytes, put back in patients
what can you use to introduce DNA (eg correct gene) into cells
inactivated viruses
how are cells of the small intestine adapted to live in a harsh environment
- cells need to be continually replenished
- cells at end of villi continually shed
cells of the small intestine
- enterocyte - absorption
- goblet cells - secrete mucus
- enteroendocrine cells - secrete peptide hormones
- paneth cells - secrete anti-microbial peptides (at bottom of crypt)
- stem cells
- submucosal cells - help maintain stem cells
where are intestinal stem cells?
base of crypt
how many cells make up a crypt? in mice how many cells does crypt produce per hour?
- 250
- 12
what genes do slow and fast dividing stem cells of the intestinal crypt express?
- slow - Bim1
- fast - Lgr5
- markers for stem cells
how do we know lgr5 positive cells are stem cells
- can determine fate of a cell through lineage tracing
- transgenes can be made that cause single cells to express a marker. transgene controlled by promotor for lgr5
- marker is bacterial gene beta galactosidase which turns cells blue
- from bottom of crypt upwards long column of cells - can see what they differentiate into
intestinal stem cell maintenance
- wnt (stem cell maintenance)
- BMP inhibits maintenance (activates differentiation)
- noggin/gremlin inhibits BMP (stem cell maintenance)
