lec 9 Flashcards
How was the first adult stem cell discovered?
Haematopoeitic stem cells (HSC)
showed that it can reconstitute the BM after irradiation by irradiating mice and replacing the BM as a treatment
Why are HSCs stem cells
they give rise to different lineages and also are self renewing
What is the HSC niche
osteoblasts of bone
What are the stem cells contained in bone marrow?
HSC and MSC (mesenchymal)
MSC can differentiate into osteoblasts, chondrocyte and are found around the vessels
Function and niche of MSC
it homes to site of injury in the body where it can differentiate to help repair and regeneration
niche is thought to be from the vessel walls.
Why is TA (transit amplifying cells) important?
TA cells allow for a quicker proliferation and differentiation of cells
They have a limited number of rounds of division
They protect against acquisition of mutations within the stem cells (as they have a limited amount of divisions and will die after a certain amount of time)
CANCER in the INTESTINES (FAP)
The cell/stem cell can only mutate during division, so by using TA we divide the stem cell less times and less frequently. Thus reducing chance of mutation.
In Familial Adenomatous Polyposis (FAP) there is a mutation in the APC gene of chromosome 5 which is responsible for differentiation and outmigration of TA cells from the crypt, therefore we get profileration of the TA cells but no migration therefore ending up with polyps and cell mass formations in the crypt.
What is the pulse chase method?
In this experiment we are taking advantage of the fact that stem cells are slow cycling. So a pulse of BrdU over several days will theoretically be incorporated into all cells as well as stem cells as they would have divided at least once during the pulse phase. The chase is when over a long period of time the BrdU is slowly dilute out every time the cell divides. Because stem cells are slow cycling and TA cells divide more often we will be able to see a darker blue for the stem cells and a diluted out TA cell and other divided cells at the end of the chase.
What are the methods we can detect adult stem cells?
pulse - chase method
lineage tracing
clonality or clonal analysis
What is lineage tracing?
This experiment shows us the differentiation capabilities of the stem cells.
A reporter mouse is generated which has inducible labelling of all cells in the bulge with LacZ (LacZ over GFP as there are less false positives). All the progeny of these bulge cells will be labelled with LacZ after induction. We trace the descendants of the bulge cells and the multiple cell types can be seen to be incorporated with the LacZ indicating stem cells are multipotent.
Inducible by tamoxifen as it will cleave off the K15 which blocks the LacZ.
What is clonal analysis
This experiment is done in vitro and shows the proliferative capacity of the stem cells.
The cells are taken and cultured over a long time and the TA cells can be seen proliferating and differentiated limitedly and eventually dies out.
The stem cells will still survive over a long time.
