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BIO230 Section 2 > 2.6: Tissue Renewal & Stem Cells > Flashcards

2.6: Tissue Renewal & Stem Cells Flashcards

1
Q

what two processes do tissue maintenance involve

A

molecular (new molecules (lipids, proteins)) and cellular turnover (new cells in tissues)

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2
Q

what does cellular turnover involve

A

cell division and cell death

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3
Q

where can new cells come from

A
  • stem cell division (common)
  • differentiated cell division (sometimes)– liver hepatocytes, pancreatic B cells
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4
Q

t/f all cells have molecular turnover and different cell types only differ in rates

A

true

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5
Q

t/f ALL cells have molecular turnover, MOST tissues have SOME cellular turnover

A

true

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6
Q

describe which cells have higher rates of cellular turnover and which have less

A
  • rapid cellular turnover: typically cells exposed to harsh environments or activities (eg skin cells, cells lining the gut lumen, blood cells)
  • no cellular turnover: typically cells with highly specialized structure and function (eg auditory hair cells, photoreceptor cells)
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7
Q

t/f some cell types canNOT be renewed, BUT these still undergo molecular turnover

A

Ttrue

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8
Q

describe what characteristics are those of cell types that cannot be renewed

A
  • often sensory cells with specialized architecture: photoreceptor cells in eyes for vision, auditory hair cells in the inner ear for hearing
  • when these cells are lost, they cannot be replaced
  • loss of these cells can lead to vision and hearing defects with age, disease, or damage
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9
Q

explain a pulse chase experiement and why do we do it

A
  • it is used to describe that even non-renewable cells undergo MOLECULAR turnover - even if they don’t divide
    1. a pulse of radiolabeled leucine is supplied to photoreceptor cells
    2. the labelled leucine is incorporated into new proteins in a new photoreceptive disc
    3. more new proteins are made (with non labeled leucine) and new discs move into the outer segment
    4. the labeled proteins are pushed up the outer segment
    5. at the end of their life, the labeled proteins are removed from the cell
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10
Q

cell turnover occurs in many unhealthy/healthy tissues, can can be stem cell dependent or independent

A

healthy

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11
Q

describe 4 properties of stem cells

A
  1. can divide indefinitely (can last you your entire life)
  2. are not terminally differentiated (keep specializing)
  3. can self-renew: child cell can remain a stem cell
  4. can differentiate: child cell can become a differentiated cell
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12
Q

why must stem cells be highly regulated by specific mechanisms

A

because the more a stem cell divides in a particular tissue = there is a greater risk of cancer in that tissue

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13
Q

stem cell undergoes either asymmetric or symmetric division, ___________________________ are partitioned between child cells

A

internal stem cell fate determinants

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14
Q

what happens if you only have asymmetric division of stem cells

A

you will never get MORE stem cells bc one child cell will inherit all of the stem cell fate determinant and remain a stem cell and the other child differentiates

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15
Q

differentiate between asymmetric and symmetric division of stem cells

A

asymmetric: one child cell will inherit all of the stem cell fate determinant and remain a stem cell and the other child differentiates
symmetric: bold child cells inherit some stem cell fate determinant and both remain stem cells

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16
Q

describe how stem cell fates can be determined by external factors and which type of division is this related to

A
  • stem cell undergoes symmetric division
  • differences in the environment of the child cells determines whether they remain as stem cells or differentiate
  • flexible: both child cells can take on the same fate if they experience the same environment
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17
Q

define flexibility in regards to stem cell fate determination

A

both child cells can take on the same fate if they experience the same environment

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18
Q

state what a stem cell niche can promote

A

a stem cell niche can promote self renewal

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19
Q

what can stem cell niches be defined by and examples

A
  • secreted signal molecules
  • direct cell-cell contact
    examples: ecm concentrates secreted signal molecules around a stem cell, a niche supporting cell (not stem) could be near a stem cell and tells the stem to stay stem
20
Q

what happens if a stem cell leaves the niche

A

the stem cell will differentiate – becomes progenitor cells

21
Q

cell-cell contacts can determine ?

A

stem cell fate

22
Q

describe cell-cell contacts in terms of stem cell division

A

after asymmetric division, one child cell is pushed out of contact with the niche (it can be done through specific lining up of mitotic spindles)
- the cell that maintains contact with the niche will remain a stem cell
- the cell that loses contact with the niche will differentiate

23
Q

what can slow division of stem cells protect it from

A
  • random mutations from dna replication
  • telomere depletion
24
Q

what are transit amplifying cells and what do they do

A
  • one stem cell child cell turns into a transmit amplifying cell (same as progenitor), which divides rapidly to increase cell numbers before final differentiation
  • progenitor cells undergo stepwise differentiation
  • more differentiated cells have fewer cell fates
25
Q

explain how transit amplifying cells and progenitor cells differ

A

they are the same

26
Q

define the following terms
1. totipotent
2. pluripotent
3. multipotent
4. unipotent
5. terminally differentiated

A
  1. totipotent: can produce any cell type
  2. pluripotent: can produce any adult cell type
  3. multipotent: can produce multiple different cell types
  4. unipotent: can produce only one cell type
  5. terminally differentiated: fully differentiated and will not usually divide again
27
Q

what is the basal lamina an example of

A

a stem cell niche

28
Q

highlight the stem cell concepts in the epidermis (niche, division, progenitor cells, differentiation)

A
  • the basal lamina provides a stem cell niche (stays stem cells if touching)
  • stem cells divide via symmetric divisions in the basal layer
  • transit amplifying cells undergo many divisions and migrate into the prickle cell layer
  • cells differentiate further in the later layers
  • dead cells flake off from the surface
29
Q

highlight stem cells concepts in blood stem cell progeny differentiation (specificity, order of differentiation, asymmetry)

A
  • cell fate becomes increasingly specific as blood stem cells differentiate into common progenitors, then terminally differentiated cells
  • signals can establish environmental asymmetry to promote specific branches, depending on the need for specific cell types
    multipotent hematopoietic stem cell –> multipotent hematopoietic progenitors –> common lymphoid progenitor & common myeloid progenitor –> differentiated cell
  • transit amplifying cells increase cell numbers before final differentiation, slow stem cell self renewal protects the stem cells
30
Q

provide 2 examples of stem cells you have as an adult

A
  • blood
  • skin
31
Q

in the blood, transit amplifying cells increase/decrease cell numbers before final differentiation, slow/fast stem cell self renewal protects the stem cells

A

increase, slow

32
Q

what is the order of blood stem cell progeny differentiation?

A

multipotent hematopoietic stem cell –> multipotent hematopoietic progenitors –> common lymphoid progenitor & common myeloid progenitor –> differentiated cell

33
Q

describe transplantation experiments in hematopoietic stem cells

A
  • x-irradiation halts blood production and mice will die without blood cell renewal/further treatment
  • different cells (bone marrow injected from healthy donor) were transplanted into mice to see whether they could recover
    –> mouse can surivive if the injected SC colonize its hematopoietic tissues and generate steady supply of new BC
  • only 1/100,000 cells is a multipotent blood SC, transplant of 4-5 MSC can restore all blood types (including stem cells)
34
Q

the processes of transplantation experiments form the basis of what treatment

A

bone marrow transplants to treat leukemia

35
Q

which 3 subpopulations of cells can be used in transplant experiments

A

multipotent hematopoietic stem cells, granulocytes/macrophage progenitor, neutrophil

36
Q

A graduate student uses x-irradiation to halt blood cell production in a
mouse and then injects isolated committed progenitor cells from a healthy
donor into the irradiated mouse’s bone marrow. Which of the following will
most likely be observed?
a) The irradiated mouse will live a long and healthy life, with a steady
supply of differentiated blood cells.
b) The irradiated mouse will live a long and healthy life, with a steady
supply of committed progenitors and differentiated blood cells.
c) The irradiated mouse will die from immune acceptance.
d) The irradiated mouse will live for a short time, but will die due to a
decrease in blood cells.

A

D. A is wrong be we need multipotent hematopoietic SC

37
Q

list some potential drawbacks of embryonic stem cells

A

ethical concerns, immune rejection, potential for cancer to develop (ie if culture cells get into someone)

38
Q

explain what it means for embryonic SC to have full development potential

A

the cells of an early embryo (blastocyst) has different layers. the outer is the zona pellucida, second is the trophectoderm (becomes extra embryonic tissue like the placenta) and the inner most cell mass is pluripotent which becomes the embryonic body. this inner cell mass can be cultured (can be cultured indefinitely) and turns into the embryoid body which can be any kind of cell.

39
Q

describe how cultured embryonic SC can be created without a fertilized embryo

A

the process is called somatic cell nuclear transfer (SCNT). an unfertilized egg is taken from the specimen, gets denucleated (meiotic spindle and assc chromosomes removed) and merged with somatic donor cells using electric pulses causing them to fuse. the reconstructed zygote has a full amt of dna. the cell divides into an embryo (or u can harvest cells for culture) and placed into foster mother. the offspring will have the same genome as the adult somatic donor.

40
Q

which type of stem cells can be made from adult cells

A

induced pluripotent stem cells (iPS)

41
Q

what is the difference between an embryonic SC and a differentiated adult cell from the same individual?

A

they have the same genome but have differences in genome expression. genome expression can be reprogrammed to change any adult skin cell into a pluripotent stem cell. these transcription factors are called OSKM factors or yamanaka factors.

42
Q

state the type of transcription factors that can be used to change genome expression to convert differentiated adult skins cells into iPS, give examples

A

OSKM factors/Yamanaka factors
KIf4, Oct4, Sox2, Myc

43
Q

what is the grouping of the following called: KIf4, Oct4, Sox2, Myc and their use

A

transcription factors called OSKM factors/Yamanaka factors
they change genome expression to convert differentiated adult skin cells into iPS cells

44
Q

t/f can you expose iPS cells to different factors to trigger differentiation

A

yes

45
Q

almost all plant cells are ____potent stem cells

A

totipotent

46
Q

How do OSKM factors reprogram cells to become pluripotent stem cells?
a) They are transcription factors that change gene expression to alter cell
fate.
b) They are hormones that cause growth changes to alter cell fate.
c) They are receptors that directly change cell signaling to alter cell fate.
d) They are cyclin-dependent kinases that change the cell cycle to alter
cell fate.

A

A

BIO230 Section 2 (12 decks)

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