TOPIC E STEM CELLS Flashcards
What are stem cells?
- UNDIFFERENTIATED CELLS that can self renew (indefiinitely in theory) and give rise to differentiated cells
What are the 3 types of stem cells?
- Embryonic stem cells (ES cells)
- Adult stem cells –> skin, blood, gut lining, brain (replenish old or damaged cells)
- Induced pluripotent stem cells (iPS)
How often do progenitor cells replace the intestinal villi?
- Every 4 days
Where can adult stem cells be found?
- In the umbilical cord blood
- Bone marrow
What are 3 potential uses for stem cells?
- Regenerative medicine
- Modelling and treating human disease
- Understanding and treating birth defects
What does regenerative medicine do in terms of stem cells?
- Replacing diseased OR lost tissues or body parts
- Stem cells cultured in tube then placed back into body for regeneration
- e.g. bone marrow–> leukemia treatment
- Nerve cells for parkinsons
What does modelling and treating human disease with stem cells involve?
- Looking at patient stem cells in dish —> add growth factors to let them differentiate (e.g. neurons) –> see if certain drugs work on those cells)
What does understanding and treating birth defects mean for a potential use of stem cells?
- Add drugs that inhibit or stimulate a process in birth defects –> follow the normal development and test drugs
What are potential uses of ES stem cells?
- Chron’s disease, storke, Alzheimers, muscular dystrophy , blindness, deafness
What are ES stem cells derived from?
- The INNER CELL MASS of the embryo –> pluripotent
What are general characteristics of ES cells?
- Self renew
- Pluripotency markers e.g. Oct4
- Differentiate into new VARIETY of cell types of transplanted into immune defficient mice
- LONG TELOMERES at ends of chromosomes (compared to differentiated and ages which have shorter telomeres)
What are ES cells propagated in vitro in the presence of and what are examples?
- propagated in presence of growth factors
- e.g. LIF cytokine (mouse ES cells) keeps the cells from differentiating (to maintain stem cell) and FgF and Wnts for human ES cells
What are characteristics of HUMAN ES cells?
- Number of growth factors allow hESC propagation in vitro
What is the proof that hESC s are indeed hESCs?
- Self renewing and expression of pluripotency markers
- Can form 3 germ layers
- IN VITRO–> embryoid bodies
- IN VIVO –> Tetromas when injected into immunodefficient mice
How is the differentiation of Beta cells identified?
- By expression of markers! e.g. Insulin for beta islet cells
What are the two factors that are PROOF that ES cells can differentiate into particular cell types?
- Express CELL-TYPE SPECIFIC MARKERS IN VITRO (Dish)
2. Should behave as those cells IN VIVO e.g. Can ES beta pancreatic cells produce insulin when transplanted?
What are the PROBLEMS with ES cells? (5 things)
- IN VITRO–> there are heterogenous cell populations (not good if you want to turn into one particular cell type
- Transplanted cells may NOT behave normally
- Cells can have tumorigenic potential (If you gorget to differentiate one ES cell out of mayny differeentiated ones it can proliferate and cause a tumor)
- Cells may be REJECTED IMMUNOGICALLY (not genetically matched)
- Ethical Concerns (destruction of early embryo-blasstocyst)
What can stem cell behavior be influenced by?
- The environment (signalling factor present)
If you think you have isolated pancreatic beta stem cells, what evidence do you need to prove this? (3 pieces of evidence)
- They need to self renew in culture
- Express pancreatic cell marker in culture
- Can behave as Beta cells IN VIVO (e.g. insulin production in vivo)
What is the normal function of adult stem cells?
- Homeostasis
- Replenishment
- Found in stem cell niches (microenvironment)
What is an example of a multipotent stem cell?
- hematopoetic stem cell (committed stem cell)
What are mesenchymal stem cells (MSCs)?
- Multipotent stem cells
- Because they can’t form from 3 germ layers
`Where are MSCs found?
- Adipose, Muscle, thymus, dental pulp, umbilical cord, placenta
What can MSCs differentiate into?
- Bone, cartilage, muscle depending on cues
e. g. elasticity of matrix which cells are grown on + pancreatic growth factors
What have MSCs been shown to possibly reverse in mice?
- Osteoperosis –> increased markers of bone deposition
What is a way of not destroying embryos for ES stem cells?
- Induced Plutipotent Stem Cells (iPS)
What are iPS stem cells derived from?
- differentiated adult cells that have been INDUCED back into stem cells by REPROGRAMMING with certain facotrs
Can iPS cells express stem cell markers and self renew and differentiate?
- YES!
- But can’t differentiate into all cell types
In the making of iPS cell, what reprogramming factors are the cells treated with and what effect does this have? (3 effects)
- Oct4 and Sox2 activate NANOG (pluripotency) and BLOCK differentiation
- c-myc–> opens CHROMATIN –> makes genes accessible to Sox2, Oct4 and nanog
- Klf4–> PREVENTS cell death (antiapoptotic)
Can iPS cells be used in the same way as ES cells clinically /for research?
- YES–> regenerative medicine, disease modelling, drug discovery
How has sickle cell disease been ‘cured’ in vitro?
- Harvest fibroblasts in mouse tail tip
- infect with Oct4, Sox2, Klf4, c-myc VIRUSES
- Get mouse derived iPS cells
- Correct sickle cell mutation via CRSPR-cas9
- Differentiate into embryoid bodies
- Transplant corrected hematopoetic progentirs BACK into irradiated mice
What can stem cell therapy be used to treat?
- Macular degeneration
- Neurodegenerative conditions
- Liver and heart diseases
What is cloning?
- Genetically IDENTICAL copies of DNA or organism
What are two types of cloning used in cells and tissues?
- Reproductive cloning (copy elite animals, some endangered animals)
- Therapeutic cloning (Disease therapy, replaced damaged tissue)
What is the old version of the reproductive and therapeutic cloning?
- SCNT (somatic cell nuclear transfer)
- Now iPS cells replace this and skip the step of nuclear transfer)
What is the rough technique of SCNT?
- Replacing the nucleus of ovum (egg cell) with somatic cell
What was the problem with the cloning for Dolly the sheep?
- She was cloned from an adult sheep BUT this means the telomeres are SHORT and thus may have died early from this
Is the SCNT technology that was used to make Dolly the most up to date for therapeutic cloning?
- NO!
- Because iPS cells skips the step of taking the nucleus out of the somatic cell –> iPS cells just turn somatic cell BACK into iPS cell
