Adult SCs and Organoids Flashcards
Roisin L3 (36 cards)
what is the name of the intermediate cell type between stem cells and differentiation cells?
progenitor cells, or transit-amplifying cells
define progenitor cell
a multipotent cell committed to a specific lineage, cannot differentiate into other cell types.
has a limited number of divisions before they terminally differentiate into target cell
little self-renewal
give two important examples of where adult tissue-specific stem cells are found
Blood
Intestine (intestinal lining)
also, epidermis (obviously)
(outermost of three layers of skin)
define hematopoiesis
blood cell production
a single progenitor cell gives rise to all blood cells, including RBC, WBC and platelets
differentiation pathway depends on extracellular signals
where does hematopoiesis occur?
usually in the bone marrow
except T lymphocytes - develop in the Thymus
(macrophages and some dentritic cells develop from monocytes circulating in blood)
define the stem cell niche and what it is comprised of
the microenvironment where a SC is found
Comprises of surrounding cells, ECM and molecular signals
Describe the role of the stem cell niche
provides the physical, chemical and cellular signals that influence cell fate.
regulated to maintain undifferentiated state
OR promote differentiation: extracellular signal molecules that decide the identity/fate of SCs present in high concentrations
Size of niche –> # of SCs
SC matures and moves out of niche
name three types of extracellular signalling in SC niches
Direct contact
Soluble factors
Intermediate cells
describe direct contact signalling in SC niches
directly binding to ECM or other cells through membrane-bound proteins and junctions
describe soluble factors as extracellular signalling in SC niches
diffusible signalling molecules secreted by cells in the niche
(bind to receptors on SCs to activate intracellular pathways)
describe how intermediate cells play a role in extracellular signalling in SC niches
produce signals / modify environment to indirectly influence SC behaviour
describe the physical structure of the lining of the small intestine
single-layered epithelium
arranged in villi (project into gut lumen) and crypts (descend into underlying CT)
draw diagram!
how is the epithelial lining of the small intestine renewed?
cell proliferation occurs in crypts
SCs at the crypt base, interspersed among non dividing differentiated cells (Paneth cells)
progeny of SCs move upward toward the villi, after a few divisions, will differentiate
Name four types of cells that SCs in the epithelium of the lining of the small intestine can differentiate into.
- Enterocytes
- Goblet cells
- Paneth cells
- Enteroendocrine cells
SCs in the lining of the small intestine can differentiate into enterocytes. define
enterocytes = absorptive cells
pick up nutrients and water, exclude pathogens/toxins
SCs in the lining of the small intestine can differentiate into goblet cells. define
goblet cells = mucus secreting cells
what are the two main roles of Paneth cells?
- part of the innate immune system: secretes protein to kill bacteria
- secretes Wnt (a signalling molecule) that helps maintain SC population
SCs in the lining of the small intestine can differentiate into enteroendocrine cells. define
specialised secretory cells: secrete hormones (serotonin and peptide hormones that aid in homeostasis maintenance/digestion)
IN RESPONSE TO the contents of the gut (ie. senses intestinal environment)
name the two main lineages developing from HSCs (hematopoietic stem cells)
myeloid or lymphoid lineage
what cells does the common myeloid progenitor (CMP) give rise to?
erythrocytes (RBC) (technically from the erythroid progenitor, early commitment)
+ innate immune cells: megakaryocytes (platelet-producing), granulocytes (neutrophils etc), monocytes, macrophages (sometimes from macrophage progenitor) etc
what cells does the common lymphoid progenitor (CLP) give rise to?
T cells, B cells (both lymphocytes)
NK cells
tissue aging is the result of
decline in SC function
ability to maintain tissue homeostasis decreases over time
two types of tissues have cells that can divide even though fully differentiated, and hence can regenerate without the use of stem cells. name them
pancreatic beta cells
hepatocytes in the liver
small populations of SCs act as backup mechanism
what is dedifferentiation?
a reversible loss of cell identity, often in response to stress or injury, where a differentiated cell downregulates its specialised functions and regains plasticity
differentiated cells –> progenitors
progenitors –> SCs
