Lecture 34: Stem Cells Flashcards
Define stem cell
A primitive cell that can either self-renew or give rise to more specialized cell types
______________ refers to the ability of a cell to give rise to all cells of an organism, including embryonic and extraembryonic tissues (cells which support embryonic development)
Totipotency
______________ refers to the ability of a cell to give rise to all cells of the embryo and subsequently adult tissues
Pluripotency
What is the primary example of a pluripotent cell?
Embryonic stem cell
_________________ refers to the ability of a cell to give rise to different cell types of a given lineage
Multipotency
What is the primary example of a multipotent cell?
Adult stem cells
What is the overall hierarchy of stem cells?
Totipotent
Pluripotent
Multipotent
Endoderm, mesoderm, and ectoderm cell lines are considered to be _____________ embryonic stem cells
Pluripotent
The zygote is considered to be a _____________ embryonic stem cell
Totipotent
If the adult organ needs to be renewed, ____________ stem cells can divide as stem cells giving rise to one daughter cell that remains a stem cell and a set of cells that have a set number of transit amplifying divisions
Founder
True or false: each organ or tissue has a fixed number of founder cell populations programmed to have a fixed number of divisions
True
What defines the size of large final structures?
Founder stem cells because they have a fixed number of divisions
What controls the founder stem cell population?
Short range signals from things like growth factors
Are founder stem cells totipotent, multipotent, or pluripotent?
Multipotent, they are considered to be adult stem cells
True or false: transit amplifying cells can divide an unlimited number of times
False, they are programmed to divide a LIMITED number of times
How do stem cells become frequently dividing transit amplifying cells?
Founder stem cells become TACs when they leave the basal layer and are incorporated into the layers above
Characteristics of stem cells include:
Not terminally _____________
Can ____________ without limit
Undergo ___________ division
Differentiated
Divide
Slow
When stem cells divide, what are the two resulting cells?
One cell with stem cell characteristics, one with the ability to be differentiated
Are adult stem cells tissue specific?
Yes
Out of a steady pool of stem cell population, precisely 50% must remain as stem cells. What two processes accomplish this?
Divisional asymmetry
Environmental asymmetry
Which type of asymmetry in the maintenance of stem cells involves asymmetric division leading to 2 cells - one with stem cell characteristics and another with factors that give it the ability to differentiate?
Divisional asymmetry
Which type of asymmetrical division relating to the maintenance of stem cells produces 2 identical cells, but the environment influences/alters one of the cells to become terminally differentiated?
Environmental asymmetry
What two processes work closely in sync to maintain our stem cell pool?
Asymmetric division and independent choice
What hypothesis states that stem cells of some tissues selectively retain original DNA.
Immortal strand hypothesis
The immortal strand hypothesis postulates that the original strand of DNA is preserved across generations of stem cells that retain their stem cell characteristics. So what happens with the other stem cell, and why is this hypothesis important?
The other cell gets a newly synthesized strand
This is important because the stem cell will not obtain genetic errors due to getting a newly synthesized strand
What are the 5 types of stem cells?
- Embryonic
- Adult
- Fetal
- Cord blood
- Induced pluripotent
What type of stem cells can become any tissue?
Embryonic
What type of stem cells are tissue-specific?
Adult
What type of stem cells are multipotent adult stem cells that reside in the liver and have become progenitor cells for a subset of tissues?
Fetal stem cells
What type of stem cells come from a fully developed organ so they are not pluripotent?
Cord blood stem cells
What type of stem cells come from adult cells so they are not embryonic, but they are pluripotent. These are considered the best case scenario when legal/ethical considerations have to be made in terms of harvesting stem cells.
Induced pluripotent stem cells
All political and ethical issues aside, what type of stem cell is most ideal for a therapy for damaged brain tissue?
Embryonic stem cells - because they can become any tissue needed.
Embryonic stem cells are derived from what early embryonic structure?
Inner cell mass
The cells from the inner cell mass are:
A. Totipotent
B. Multipotent
C. Pluripotent
D. Determined
C. Pluripotent
What are the 3 different protocols used for ES cell differentiation?
Cells differentiated as embryoid bodies (key is that there are no signals to become an organism so they stop dividing)
Cells differentiated on stromal cells
Cells differentiated on extracellular matrix proteins
What stage of the embryo are embryonic stem cells derived from?
Blastocyst stage - inner cell mass
True or false: Embryonic stem cells derived from the blastocyst stage of the embryo are capable of proliferating indefinitely in culture with unrestricted developmental potential
True
What happens when embryonic stem cells harvested from the blastocyst stage are put back into the blastocyst?
They integrate well with the embryo and develop into different cell types with characteristics appropriate for that site (even germ cells)
What happens when embryonic stem cells are injected into an embryo at a later stage or into an adult?
They fail to receive appropriate sequences of cues for proper differentiation. There is no control mechanism once injected to guide it to a certain spot, so if it lands in an inappropriate location it can become cancer
The defining feature of an embryonic stem cell is its ability to differentiated into a wide range of tissues. Therefore, they have the dangerous potential to give rise to disorganized growths called _____________, which may contain tissues like teeth and bone in strange locations
Teratomas
In order to avoid teratoma formation after embryonic stem cell injections, what precautions can be taken?
Make sure you are targeting the right tissues by manipulating the cell culture prior to injection. This is done to stop differentiation so they have less tendency to go back to some other tissue type. Give it as much of a stromal environment as possible.
True or false: teratomas have been discovered after ES injection in vivo followed by inappropriate differentiation into cartilage, bone, skin, nerves, gut, and respiratory lining
True
Which of the following would be most useful in re-programming a stem cell?
A. Transcription factors
B. Growth factors
A. Transcription factors
Which of the following would be associated with stromal differentiation of stem cells?
A. Transcription factors
B. Growth factors
A. Transcription factors
Which of the following is associated with outside-in signaling of stem cells?
A. Transcription factors
B. Growth factors
B. Growth factors (like FGF or RA)
ES cells may be derived at high frequency from good quality embryos. What does the initial serum contain?
Medium + mouse or human embryonic fibroblast feeder cells
What factor is needed to cause differentiation of ES cells into adipocytes, neurons, and smooth muscle?
Retinoic acid
Retinoic acid is important for production of different cell types of ES cells. Which of the following is not a cell type requiring the action of RA?
A. Adipocytes
B. Neurons
C. Astrocytes
D. Smooth muscle
C. Astrocytes
Astrocytes and oligodendrocytes require fibroblast growth factor
There has been recent promising “proof-of-principle” research indicating that ES cells are strong, reliable, and establish pluripotency with a solid theoretical experimental foundation to induce development of specialized cell types. How does this research apply to organ transplantation?
It would solve rejection problems
There is wide potential for stem cell therapies in US patient populations. What medical condition has the highest number of patients that could potentially benefit from stem cell-based therapies?
Cardiovascular disease
Successful treatment of the following diseases in animal models was completed with what type of stem cells?
Severe immune deficiency Diabetes Parkinson's Spinal injury Demyelination Myocardial infarction
Embryonic stem cells
The central strategies of regenerative medicine involve harvesting two cell types: primary cells and ESCs (or iPSCs). What is the purpose of harvesting primary cells?
These can be reprogrammed into desired cell types and transplanted into a host
The central strategies of regenerative medicine involve harvesting two cell types: primary cells and ESCs (or iPSCs). What is the purpose of harvesting ESCs or iPSCs?
They can be directed to differentiate into desired cells types and then transplanted into a host
Name some of the challenges for regenerative medicine and transplantation therapy:
Production of required cell type in sufficient numbers and _______ form
What _____ to transplant
Delivery and proper __________
Problems of tissue/immune __________
Embryonic or fetal-derived grafts may be __________
Some transplantation sites may be immunologically ____________
Pure Cell Integration Rejection Immunogenic Privileged
What is the primary advantage of using mature stem cells?
Immune response is less likely because patients are using their own cells
They are also partly specialized so they require less coaxing to become specialized cells
What are some disadvantages to using mature stem cells?
They are only multipotent - so there is limited flexibility
Less common (especially with age), limited longevity, difficult to find and extract
What is the primary advantage to early stem cells?
Immortal, pluripotent, easy to extract, readily available
What are the primary disadvantages to using early stem cells?
Immune rejection possible, difficult to control
Immune rejection is a serious problem in adult stem cells if they are grafted from a genetically different person, so an identical genotype is needed. What process involves taking the nucleus from a somatic cell of a patient and injecting it into the oocyte of a donor replacing the oocyte nucleus?
Somatic cell nuclear transfer
The blastocyst generated from this hybrid oocyte and ES cells is then isolated and can be used in the patient to avoid an immune reaction
An alternative approach to stem cell therapy may be better. If adult cells could be converted into ES-like cells by manipulating _______________ directly
Gene expression
What are the key determinants of ES cell character?
Gene regulatory proteins
Biochemical comparisons of ES cells with other cell types suggest some candidate genes for direct manipulation of gene expression. What are the 4 potential gene regulatory proteins?
Oct3/4
Sox2
Myc
Klf4
When Oct3/4, Sox2, Myc, and Klf4 are injected into ______________, they become ES like cells, including the ability to differentiate into other cell types
Fibroblasts
What is the yield of ES-like stem cells from alternative approaches like direct manipulation of gene expression using regulatory proteins?
Low, and these are not identical to ES cells
What 4 transcription factors are essential for establishment and maintenance of pluripotent stem cells in the embryo?
Nanog
Oct4
Sox2
FoxD3
What transcription factor is required for early stages of pluripotent cell differentiation?
GCNF
What 2 growth factors are found in pluripotent cells?
Cripto and GDF-3
What type of stem cells reside in tissues and respond to demands of growth or repair?
Adult stem cells
Proper tissue organization, growth, or repair require that there be ____________ on developmental potential of stem cells. These limits are strictly imposed by powerful molecular restraints on ________ ___________ and are heritable during many rounds of cell division
Restrictions
Gene expression
An adult stem cell may show relaxation of the molecular restraints on gene expression in an altered environment, possible accounting for __________. Even so, this is observed usually at low frequency.
Plasticity
True or false: anything that is not an embryonic stem cell is an adult stem cell
True
What are the 3 primary advantages to harvesting umbilical cord blood for stem cells?
Undifferentiated
No ethical problems
No gene manipulation
What type of stem cells come from cord blood?
Hematopoietic stem cells
What type of stem cells one from cord tissue?
Mesenchymal stem cells
True or false: hematopoeitic and stromal stem cells can become any cell type
False
What type of stem cells are found in cord blood, bone marrow, and peripheral blood?
Hematopoeitic stem cells
What type of stem cells are found in Wharton’s jelly, bone marrow, adipose tissue, and tooth pulp?
Mesenchymal stem cells
What type of mesenchymal stem cell has the natural ability to differentiate into bone, cartilage, muscle, tendon/ligament, adipose tissue, or other potential structure with the proper growth factor applied?
Adipose-derived mesenchymal stem cells (AD-MSCs)
An example of adult stem cell therapy involves harvesting hematopoeitic stem cells from bone marrow –> transplanting them into cell culture to multiply –> transplanting them into leukemia patient. How do these cells go from pluripotent to the RBCs necessary for the patient?
Pluripotent –> multipotent –> myeloid progenitor –> erythrocytes
Each type of specialized stem cell has a _________ of its developmental history and seems committed to its fate. This limits its clinical use
Memory
What are 2 different sources of potential human embryonic stem cells?
Somatic cell nuclear transfer (SCNT)
Induced pluripotent (iPS) cells
What are the potential sources of eggs used in SCNT? (These are the cells that your somatic cells replace the nucleus)
Self, mother, relative, egg bank
What are some of the problems associated with SCNT?
Inefficient, technically demanding, needs to be available in many or all hospitals
How is reprogramming done without using an egg or making an embryo?
Combine a pluripotent cell with an adult cell and fuse them; the hybrid cell shows activation of the embryonic genome. You can also inject pluripotent genes into an adult cell and it will then become pluripotent
What effect do growth factors have on stem cells?
They bind membrane receptors and control TF activation of differentiation genes (main effect is activation of proliferation)
What transcription factor turns off TGF signaling temporarily?
Noggin
Which of the following does not have the potential to develop teratomas?
A. iPS stem cells
B. ES cells
C. EC cells from nuclear transfer
D. Stem cells from fusion of somatic cells with ES
E. All of the above have the potential to form teratomas
E
Challenges of stem cell maintenance include __________ and ____________ aberrations that can occur at multiple steps of pluripotent stem cell maintenance.
Genomic
Epigenomic
