Stem Cells Flashcards
Embryonic stem cell
Can become almost any cell type in body (pluripotent)
What is a stem cell?
Single cell that can replicate self or differentiate into many cell types
Adult stem cell
Differentiate into subset of related cell types (multipotent)
Embryonic stem cells can…
- treat many diseases
- ethical issues
- genetic engineering in mammals (knock out gene in mice)
- core set of transcription factors (OSKMs) maintain ES cell
Induced pluripotent stem cells (iPS)
- from patients own cells
- can cure diseases
- safety is not 100%
- differentiated cells can be produced from cultured iPS cells
Adult stem cells
- important in growth, healing, and repair of cell loss via wear and tear
- blood & bone marrow stem cells used to treat disease (rare and can only become a subset of related cell types)
What are the 2 types of Adult (somatic) stem cells?
- Stem cells in epithelia of small intestine
2. Haematopoietic stem cells
Stem cells in small intestine
- renew itself at greater rate than any other tissue in the body
- molecular mechanisms well understood
Absorptive cell (small intestine)
Take nutrients from gut lumen
Goblet cell (small intestine)
Secrete protective coat of mucus
Parieth cell (small intestine)
Secrete protein to kill bacteria
Enteroendoceine cell (small intestine)
Secrete serotonin and peptide hormones to regulate growth
2 fates of stem cell’s daughter cells
- Self renew
2. Terminally differentiated cell
2 types of ways to divide (daughter cells)
- Asymmetric division
2. Independent choice
Asymmetric division
Determined by asymmetry in dividing stem cell
Independent choice
Determined by stochastically or/and environment
Parieth cells create stem cell niches…
- at the bottom of crypt in small intestine
- room for 15 stem cells at bottom of each crypt
- not enough room for all cells so some forced to move up and as a result differentiate
WNT signaling
Maintains pathway for proliferation
NOTCH signaling
Inhibit pathway to differentiation
In Adenoma what happens?
WNT signaling cannot be turned off as cells move up and differentiate so they continue to divide
Haematopoietic stem cells
- all types of blood cells are made by a common stem cell in one marrow: H. Stem cells
- most complex stem cell system
- commitment is a stepwise process
- single stem cell fan reconstitute entire blood system (in mice)
- ## in humans same process used to treat/ eukaemia by bone marrow transplant
Haematopoietic stem cells depends on contact with stromal cells
- when contact is lost, stem cell loses stem cell potential
- stromal cells is not complete dependence of stem cells, as same have been found in blood stream
Cancer stem cells
- can be responsible for growth of some rumors
- radiotherapy or chemotherapy often kill fast feeling cells, but slow growing cells not killed causing the disease to resurrect
