Lecture 3 Flashcards
How are embryonic stem cells obtained?
At the 32 cell stage, the cells around the outside differentiate into trophectoderm, leaving the pluripotent cells in the inner cell mass which can be removed and cultured on a petridish
What is the function of embryonic stem cells?
They are pluripotent (genetically different state) and can be induced by an array on differential factors to induce different cell types
What are the main properties/roles of stem cells?
They undergo mitosis to give rise to a daughter that is identical to the mother for self renewal and another that undergoes differentiation to produce multiple lineages and eventually becomes a specialised cell.
What is the definition of a true pluripotent stem cell?
A cell that can give rise to ectoderm, mesoderm and endoderm
What are progenitor cell properties?
Are more restricted than multipotent cells- have limited differentiation and self renewal= can only go down a particular group
How do stem cells maintain homeostasis and why?
If they divide 4 times they give rise to 4 specialised cells. Need a balance between self renewal and generating specialised cells. Are needed to replenish tissues, organ growth or generating a specific cell type at a particular time point.
What are adult stem cells and give an example?
They are stem cells retained during development that are used to replace damaged tissue. E.g. skin stem cells are multipotent and can give rise to 30 skin cell types meaning they are tissue specific. Blood is in bone marrow and was first discovered.
Why do we need a one to one replacement of dead/damaged cells?
If the cells aren’t replaced the tissue will die, if too many cells are made then a tumour will arise
What does adult stem cell optimum mean?
It means that they have a specialised feedback loop to maintain tissue homeostasis. The optimum can change e.g. when weight lifting
What are the 5 types of adult stem cells?
1) mesenchymal= bones, tendons, fat, cartilage, muscle
2) epithelial= skin and fat
3) muscle
4) neural= glial, neurons and retina
5) hematopoietic= blood, immune cells
What are niches and how were they discovered?
They were discovered when white blood cell levels in children were low- hematopoietic stem cells are found in a niche in bone marrow. Stem cells are attached by specialised cell adhesion molecules to stromal support cells. When they give rise to a progenitor, it feeds back to the stromal and stem cell - constant feedback from the cell and environment to maintain homeostasis.
What are the types of hematopoietic cells and how are they maintained in an undifferentiated state?
Lymphoid= B and T lymphocytes and NK-cells
myeloid= the rest
Secreted factors from support cells e.g. SCF maintain the stem cell fate along with BMP and JAK/STAT signalling
How are HSCs activated?
They are usually quiescent and sit in the endosteal zone near the osteoblastic lining cells. They are activated by signals coming from vascular endothelial cells or CAR cells which causes them to activate and migrate into the vascular niche. They act to replace active stem cells or replace lost quiescent stem cells.
What are the properties of muscle stem cells?
They are called satellite cells and run up and down the muscle fibre underneath the basal cell lamina- normally quiescent
How are skeletal muscles self renewed?
MyoD and PAX7 are TFs- MyoD is for differentiation, PAX7 is for self renewal. Found that ECM proteins, shh, cilia and diet are involved in asymmetric cell division
