Chapter 5 - Stem Cells

make entire islet (not just the B-islet cells, but rather all the cells that make up the islet) and transplant it into patient

what are organoids used for in terms of type 1 diabetes treatment

1) remove HLA antigen that triggers immune response → this is the antigen normally present that the immune system recognizes and leads to it attacking the B-cells

2) encapsulate transplant → immune cell can’t get in, but insulin can still get out (doesn’t evoke immune response)

2 ways to make immune-evasive iPSCs and brief description

chemically induced pluripotent stem cell → instead of using the 4 transcription factors and harnessing a virus, it uses chemicals to cause cell to turn in stem cell

what is a CiPSC and how is it different from a normal iPSC

normal iPSCs harness the power of viruses which raises some safety concerns, but CiPSCs don’t have to use viruses

why are CiPSCs used over normal iPSCs?

self-renewal and potency

what are the 2 main traits of stem cells

cell has the ability to divide and recreate itself (some stem cells can divide without limits)

what is the concept of self-renewal

cell has the ability to give rise to progeny that can become differentiated cell types

what is the concept of potency

1) asymmetric cell division → stem cell division gives 1 stem cell and 1 committed cell

2) symmetrical renewing → stem cell division gives 2 more stem cells (itself)

3) symmetrical differentiation → stem cell division give 2 committed cells

what are the 3 different types of stem cell divisions and brief description

multipotent stem cell → committed stem cell → progenitor cell → differentiated cell(s)

what is the adult stem cell lineage order

totipotent → capable of making every cell in the embryo and the placenta

pluripotent → capable of making every cell except cells in the trophoblast (placenta)

multipotent → committed to making smaller range of cell types

totipotent vs pluripotent vs multipotent potential

zygote and first 4-8 cells it gives rise to

what is the source of a totipotent stem cell

inner cell mass of blastocyst

what is the source of a pluripotent stem cell

embryo or adult brain

what is the source of multipotent stem cell

a particular germ layer → such as it can only become cells in the ectoderm

when saying multipotent stem cells are limited in what they can become, what is limitation typically

a progenitor cell is no longer capable of endless self-renewal (limited number of divisions before they differentiate)

what is the main difference between a stem cell and a progenitor cell

totipotent → pluripotent → multipotent → limited differentiation potential → limited division potential → functional differentiated cell

order of maturational series of a stem cell

adult (multipotent) stem cell

what type of stem cell is a hematopoietic stem cell

lymphoid progenitor cell (cells of the immune system) OR myeloid progenitor cell (blood cells)

what are the 2 types of progenitor cells a hematopoietic stem cell can become

brain and skeletal muscle

what adult stem cells have a low turnover rate

mesenchymal stem cells, intestine, hematopoietic stem cells, epidermis, hair follicle, and sperm

what adult stem cells have a high turnover rate

bone marrow

what is the niche location of hematopoietic stem cells

1) neurotransmitter release

2) endocrine signaling

3) juxtacrine signaling/cell adhesion

4) asymmetric localization of cytoplasmic determinant

5) paracrine signaling

6) ECM adhesion / mechanical force

what are the main 6 stem cell regulatory mechanisms

asymmetric localization of cytoplasmic determinant

which stem cell regulatory mechanism is the only one that’s not extracellular

ECM binds to receptor on the stem cell and tells it t divide AND the mechanical force it puts on cell can tell it what to become

how is ECM adhesion/mechanical force a stem cell regulatory mechanism?

hormones are signals that can tell the cell what to do

how is endocrine signaling a stem cell regulatory mechanism

it’s autonomous specification, so something from egg cytoplasm telling it to divide

how is asymmetric localization of cytoplasmic determinant a stem cell regulatory mechanism?

intracellular changes such as transcriptional regulation or epigentic regulation

what type of changes do stem cell regulatory mechanisms typically lead to

they seem to have more potential of cell types they can make (such as both osteoblasts and adipocytes which are vastly different) BUT they aren’t well understood

what are the potential benefits of mesenchymal stem cells and what is a drawback

the elasticity of the matrices upon which the cells sit (the ECM can be hard or soft depending on what proteins are present in it)

what is mesenchymal stem cell differentiation influenced by

higher substrate elasticity → harder

lower substrate elasticity → softer

higher vs lower substrate elasticity in terms of ECM

the embryo

what does the inner cell mass in the blastocyst become during development

Oct4, Nanog, and Sox2 → they tell the cells to remain embryonic stem cells

what 3 transcription factors do cells in the ICM highly express and what do they lead to

it’s where the ICM was and it becomes the embryo

what is the epiblast

primordial germ cells from the fetus which gives embryonic germ cells which can culture pluripotent stem cells

other than from the ICM of the blastocyst-stage embryo, where else can you obtain pluripotent stem cells

the epiblast

embryonic stem cells divide further to give rise to what

it’s the equivalent of the blastopore but in humans → opening where cells are moving through during gastrulation

what is the primitive streak

ectoderm

during gastrulation, what germ layer(s) do cells that DONT move through the primitive streak become?

endoderm or mesoderm

during gastrulation, what germ layer(s) do cells that DO move through the primitive streak become?

1) regenerative medicine → regenerate cells that are lost

2) disease modeling → use cell as model of disease to see what happens

2 reasons why using human models to study development and disease is important

a ball of cells like a tumor with characteristics from all 3 germ layers

what is a teratoma

1) positives → reset epigenetic marks

2) negative → moral issues, may have immune rejection

positives and negatives of ESCs

1) positives → patient specific so less chance for immune rejection, no moral issues since taking from adult somatic cells

2) negatives → takes longer/more effort, epigenetic memory not completely reset

positives and negatives of iPSCs

1) use patient-specific iPSCs to study pathology

2) use iPSC-derived differentiated cells for screening drugs

3) combine gene therapy with patient-specific iPSCs to treat disease

4) use patient-derived iPSC-derived cells in transplants (no immune rejection)

4 major uses of iPSCs

Oct3/4, c-Myc, Sox2, Klf4 → Yamanaka factors (person that discovered it)

what 4 transcription factors are misexpressed when creating iPSCs and what is another name for these 4 factors

they are associated with pluripotency → tell cell to remain pluripotent AND they activate Nanog which further helps with pluripotency

what are the transcription factors Oct3/4 and Sox2 important in in iPSCs generation

it’s important in opening up chromatin (tends to be more open in embryonic cells, so trying to replicate that)

what is the TF c-Myc important in in iPSC generation

it plays an important role in preventing cell death, allowing us to retain more pluripotent stem cells

what is the TF Klf4 important in in iPSC generation

1) start with differentiated cell like fibroblast

2) use virus to misexpress the 4 transcription factors

3) infect fibroblast with the virus with the 4 TFs

4) give the iPSC what’s needed to differentiate into desired cell type

explain process of generating iPSCs

single gene diseases and when we know what is causing it (such as sickle cell anemia)

when curing a human disease using iPSCs plus recombinant genetics, what type of disease does it work best on

1) harvest tail tip fibroblasts

2) infect fibroblasts with Oct4, Sox2, Klf4, and c-Myc viruses

3) correct the sickle-cell mutation in iPS cells by specific gene targeting (such as through CRISPR)

4) differentiate them into hematopoietic stem cells

5) do bone marrow transplant → kill off all hematopoietic progenitors already present and replace with the ones created

process of curing sickle cell anemia in mouse using iPSCs plus recombinant genetics

many iPSCs that make a “miniature” version of the organ of interest

what makes up an organoid

the cells sort out due to CAMs into how they would be expected in the organ in the human body

when making organoids, what do the cells typically do on their own with minimal assistance

modeling human diseases

in addition to treating diseases, what else can organoids be used for