TOPIC E STEM CELLS

Question 1

What are stem cells?

Answer 1

• UNDIFFERENTIATED CELLS that can self renew (indefiinitely in theory) and give rise to differentiated cells

Question 2

What are the 3 types of stem cells?

Answer 2

• Embryonic stem cells (ES cells)
• Adult stem cells –> skin, blood, gut lining, brain (replenish old or damaged cells)
• Induced pluripotent stem cells (iPS)

Question 3

How often do progenitor cells replace the intestinal villi?

Answer 3

• Every 4 days

Question 4

Where can adult stem cells be found?

Answer 4

• In the umbilical cord blood

- Bone marrow

Question 5

What are 3 potential uses for stem cells?

Answer 5

1. Regenerative medicine
2. Modelling and treating human disease
3. Understanding and treating birth defects

Question 6

What does regenerative medicine do in terms of stem cells?

Answer 6

• 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

Question 7

What does modelling and treating human disease with stem cells involve?

Answer 7

• 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)

Question 8

What does understanding and treating birth defects mean for a potential use of stem cells?

Answer 8

• Add drugs that inhibit or stimulate a process in birth defects –> follow the normal development and test drugs

Question 9

What are potential uses of ES stem cells?

Answer 9

• Chron’s disease, storke, Alzheimers, muscular dystrophy , blindness, deafness

Question 10

What are ES stem cells derived from?

Answer 10

• The INNER CELL MASS of the embryo –> pluripotent

Question 11

What are general characteristics of ES cells?

Answer 11

• 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)

Question 12

What are ES cells propagated in vitro in the presence of and what are examples?

Answer 12

• 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

Question 13

What are characteristics of HUMAN ES cells?

Answer 13

• Number of growth factors allow hESC propagation in vitro

Question 14

What is the proof that hESC s are indeed hESCs?

Answer 14

1. Self renewing and expression of pluripotency markers
2. Can form 3 germ layers
   - IN VITRO–> embryoid bodies
   - IN VIVO –> Tetromas when injected into immunodefficient mice

Question 15

How is the differentiation of Beta cells identified?

Answer 15

• By expression of markers! e.g. Insulin for beta islet cells

Question 16

What are the two factors that are PROOF that ES cells can differentiate into particular cell types?

Answer 16

1. 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?

Question 17

What are the PROBLEMS with ES cells? (5 things)

Answer 17

1. IN VITRO–> there are heterogenous cell populations (not good if you want to turn into one particular cell type
2. Transplanted cells may NOT behave normally
3. 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)
4. Cells may be REJECTED IMMUNOGICALLY (not genetically matched)
5. Ethical Concerns (destruction of early embryo-blasstocyst)

Question 18

What can stem cell behavior be influenced by?

Answer 18

• The environment (signalling factor present)

Question 19

If you think you have isolated pancreatic beta stem cells, what evidence do you need to prove this? (3 pieces of evidence)

Answer 19

1. They need to self renew in culture
2. Express pancreatic cell marker in culture
3. Can behave as Beta cells IN VIVO (e.g. insulin production in vivo)

Question 20

What is the normal function of adult stem cells?

Answer 20

• Homeostasis
• Replenishment
• Found in stem cell niches (microenvironment)

Question 21

What is an example of a multipotent stem cell?

Answer 21

• hematopoetic stem cell (committed stem cell)

Question 22

What are mesenchymal stem cells (MSCs)?

Answer 22

• Multipotent stem cells

- Because they can’t form from 3 germ layers

Question 23

`Where are MSCs found?

Answer 23

• Adipose, Muscle, thymus, dental pulp, umbilical cord, placenta

Question 24

What can MSCs differentiate into?

Answer 24

• Bone, cartilage, muscle depending on cues

e. g. elasticity of matrix which cells are grown on + pancreatic growth factors

Question 25

What have MSCs been shown to possibly reverse in mice?

Answer 25

- Osteoperosis --> increased markers of bone deposition

Question 26

What is a way of not destroying embryos for ES stem cells?

Answer 26

- Induced Plutipotent Stem Cells (iPS)

Question 27

What are iPS stem cells derived from?

Answer 27

- differentiated adult cells that have been INDUCED back into stem cells by REPROGRAMMING with certain facotrs

Question 28

Can iPS cells express stem cell markers and self renew and differentiate?

Answer 28

- YES! | - But can't differentiate into all cell types

Question 29

In the making of iPS cell, what reprogramming factors are the cells treated with and what effect does this have? (3 effects)

Answer 29

- 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)

Question 30

Can iPS cells be used in the same way as ES cells clinically /for research?

Answer 30

- YES--> regenerative medicine, disease modelling, drug discovery

Question 31

How has sickle cell disease been 'cured' in vitro?

Answer 31

- 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

Question 32

What can stem cell therapy be used to treat?

Answer 32

- Macular degeneration - Neurodegenerative conditions - Liver and heart diseases

Question 33

What is cloning?

Answer 33

- Genetically IDENTICAL copies of DNA or organism

Question 34

What are two types of cloning used in cells and tissues?

Answer 34

1. Reproductive cloning (copy elite animals, some endangered animals) 2. Therapeutic cloning (Disease therapy, replaced damaged tissue)

Question 35

What is the old version of the reproductive and therapeutic cloning?

Answer 35

- SCNT (somatic cell nuclear transfer) | - Now iPS cells replace this and skip the step of nuclear transfer)

Question 36

What is the rough technique of SCNT?

Answer 36

- Replacing the nucleus of ovum (egg cell) with somatic cell

Question 37

What was the problem with the cloning for Dolly the sheep?

Answer 37

- She was cloned from an adult sheep BUT this means the telomeres are SHORT and thus may have died early from this

Question 38

Is the SCNT technology that was used to make Dolly the most up to date for therapeutic cloning?

Answer 38

- 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