Stem cells Flashcards
what are hematopoietic stem cells?
SC that give rise to blood cells - in the bone marrow
originate from mesoderm
what are Paneth cells?
epithelial cell of the small intestine, provide niche for intestinal stem cells
what are the features of adult stem cells?
lineage restricted multi potent stem cells
rare
highly regulated
proliferation and differentiation under physiological control
function to maintain tissue homeostasis and repair
what occurs in asymmetrical division?
stem cell has internal asymmetry and divides in such a way that two daughter cells are different at birth
describe brdU pulse labelling
normally given to young animal, in which tissue is growing rapidly
you wait for many days/weeks before fixing tissue and staining with antibody that recognises DNA in which the brdU has been incoorperated.
brdU is taken up by any cell that in S phase of division cycle at time of initial pulse.
because brdU would be expected to dilute by half at the point of any subsequent division, any cells remained strongly labelled at time of fixation are assumed to have undergone no or few divisions since replicating their DNA at the time of pulse
what is the stem cell niche hypothesis?
proposed that stem cells within fixed compartments that promote and maintain their characteristics
microenvironments or niches regulate the behaviour of stem cells by preserving their quiescent state or controlling balance between self renewal and differentiation after activation.
describe the niche of the small intestine
functional region composed of villi covered with differentiated cells
and proliferative region - Lieberkuhns crypts containing Stem Cell niches
villi extend to intestinal cavity
numerous crypts surround base of each villus
how does the small intestine regenerate in relation to its niche?
pluripotent stem cells of the crypt give rise to goblet, enterocytes and enterondocrine and paneth cells
first 3 cell types migrate upwards on the villus and several days later reach top, die and shed.
paneth cells however remain at crypt base living longer than villus cells (about 3 weeks)
small intestine has rapidly proliferating stem cells.
describe the niche of Drosophila germ cells
testis is a tube 2mm in length.
distal part ends with a terminal papilla which contains germ proliferation centre.
three cell types within it, apical cells, germ SC’s, and cyst progenitor cells
what are fundamental properties of stem cell niches
main biological role of niche is to maintain viability and self renewal of stem cells for long periods
usually well supplied with blood vessels and nerve endings and physically protect STEM CELLS.
How is quiescence maintained in hematopoietic stem cells?
By CXCL12 (a cytokinine) and stem cell factor (SCF)
