Unit 18: Stem Cells

Question 1

what is totipotency?

Answer 1

ability to form a fully formed, complex, multicellular organism

Question 2

what are the requirements to be a tissue?

Answer 2

1. mechanical strength (connective tissues)
2. delivery of oxygen and nutrients and removal of waste (blood vessels)
3. electrical signaling (nerve cells)
4. disposal of dead and damaged cells (macrophages, lymphocytes)

Question 3

which cells originate outside the tissue and then invade it during development?

Answer 3

nerve cell axons, endothelial cells, schwann cells

Question 4

which cells originate outside the tissue and then invade it continuously?

Answer 4

macrophages, other blood cells

Question 5

what are the 3 factors contributing to tissue stability?

Answer 5

• cell communication
• selective cell adhesion
• cell memory

Question 6

what is cell memory?

Answer 6

when cell preserve their distinct identity and pass it onto their progeny

Question 7

what is selective cell adhesion?

Answer 7

homophilic binding and other selective attachments keeping cells in their proper place

Question 8

how long does it take for intestinal cells to renew?

Answer 8

3-6 days

Question 9

how long does it take fornerve cells to renew?

Answer 9

trick question they NEVER do

Question 10

what do osteoclasts do?

Answer 10

slowly eat away old bone matrix

Question 11

what do osteoblasts do?

Answer 11

deposit new bone matrix

Question 12

how long does it take blood cells to be removed from bone marrow?

Answer 12

120 days

Question 13

how long does it take for skin to be renewed?

Answer 13

2 months

Question 14

what makes a cell terminally differentiated? give some examples.

Answer 14

unable to divide themselves.

red blood cells, epidermal cells in upper layers of skin, cells in gut epithelium

Question 15

where do replacement cells come from for terminally differentiated cells?

Answer 15

proliferating precursor cells which come from undifferentiated stem cells

Question 16

how can stem cells be identified if they are difficult to spot in tissues?

Answer 16

specific molecular markers

Question 17

how do stem cells differentiate into the appropriate cell type?

Answer 17

• express specific transcription regulators
• developmentally restricted

Question 18

describe how cell replacement occurs in the lining of the small intestine?

Answer 18

we have stem cells at the bottom of crypts which give rise to precursor cells.

the precursor cells move upward in the epithelial sheet and then differentiate into absorptive/secretory cells

differentiated cells die when they get to the top of villi

Question 19

what are crypts?

Answer 19

epithelial tissue that descend down into underlying connective tissue

Question 20

describe cell replacement in the stratified epithelium epidermis?

Answer 20

• the stem cells and precursor cells are attached to the basal lamina
• differentiating cells travel outward from site of origin, perpendicular to cell sheet
• terminally differentiated/dead cells are shed from kin surface

Question 21

what is hematopoiesis?

Answer 21

the process of forming many possible types of blood cells and platelets from one hematopoietic stem cell

Question 22

where are hematopoietic stem cells found?

Answer 22

bone marrow

Question 23

describe how Wnt proteins stimulate cell proliferation in intestine.

Answer 23

• the signal molecule promoting proliferation is located in the crypt
• crypt cells secrete proteins that prevent Wnt pathways outside the cell from being stimulated

when Wnt active, we get cell proliferation

Question 24

how do stem cells repair lost and damaged tissues?

Answer 24

proliferate indefinitely and produce progeny that differentiate

continuously renew normal tissues

Question 25

how do we treat people with leukemia? what is this treatment analogous to in mice?

Answer 25

- iridate or give cytotoxic drugs that destroy the cancerous cells - bone marrow transplant gives the patient new hematopoietic cells - analogous to what we do when mice lose their hematopoietic stem cells

Question 26

what does it mean when a cell is pluripotent?

Answer 26

can proliferate indefinitely while retaining ability for unrestricted differentiation

Question 27

which cells give rise to all tissues and cell types in body?

Answer 27

embryonic stem cells

Question 28

progeny ES cells integrate into whatever site they come to occupy, which means ____

Answer 28

they adopt the characteristics and behaviors of normal cells

Question 29

mice ES cells are used to study what?

Answer 29

gene function and organism development

Question 30

what are some issues that may arise from the use of ES cells to repair human tissues?

Answer 30

immune rejection - immune system can destroy these cells if they are genetically different ethical considerations - is the use of human embryos to produce ES cells ethical?

Question 31

what are induced pluripotent cells (iPS cells)? what cells are turned into iPS cells?

Answer 31

differentiated adult cells that can be induced into an ES cell like state ex. fibroblasts

Question 32

iPS cells can induce expression of what transcription factors?

Answer 32

Oct4, Sox2, Klf4

Question 33

describe some cell-based therapies utilizing iPS and what condition they treat.

Answer 33

skeletal muscle fibers - muscular dystrophy nerve cells - parkinsons insulin secreting cells - type 1 diabetes cardiac muscle cells - heart attack

Question 34

can iPS cells be used to study the potential effects of candidate drugs?

Answer 34

yes they can

Question 35

how can iPS cells be used to treat individuals suffering from genetic illnesses?

Answer 35

take out fibroblasts from individual suffering from genetic disease, add Oct4, Sox2, Klf4 to make them iPS cells, repair the disease causing mutation, induce the cells' differentiation and put them back in!!!

Question 36

how can iPS cells be used to study the potential effects of candidate drugs?

Answer 36

take out fibroblasts from individual, add Oct4, Klf4, Sox2 to make them iPS cells, let cells differentiate, add drug that reverses diseases to affected cells, give human the drug if it works out!

Question 37

ES cells and iPS cells can be forced to differentiate and self assemble into what?

Answer 37

organoids

Question 38

what are organoids?

Answer 38

miniature organs grown in lab resembling actual organs in terms of organization

Question 39

human ES cells can form what type of organoid structure?

Answer 39

multilayered retina!

Question 40

what is the most complex organoid to have been produced?

Answer 40

human brain

Question 41

what is the purpose of organoids?

Answer 41

studying organ development by: - identifying/manipulating genes - exploring cell-cell interactions - how are developmental pathways impacted by disease?