Stem cells Export Flashcards
Give an example (2) of regenerative medecine achieved through stem cells
Beta-cell replacment for T1D
Goals : production of glucose-responsive, insulin secreting beta cells and functional integration
Challenges : integration, survival, durability of engrafted beta cells, reccurent immune attacks
To date : phase 1-2 clinical trial ongoing
Give an example (1) of regenerative medecine achieved through stem cells
Stem cell trials for repairing retinal pigment epithelium in AMD (age-related macular degeneration) :
Goals : restoration of function with iPSCs
Challenges : precise localized delivery, potentially oncogenic mutation led to halt of trial
What are the challenges of pluripotent stem cells ?
Cost of iPSC culture
Optimization of the differentiation protocol
Abscence of data on the whole body (compared to in vivo studies)
What are the advantages of pluripotent stem cells ?
Unlimited source human cells or tissues
Possibility to derive from PSCs cells or tissues of interest
Identification of targets for therapy
Identification of active drugs
Prediction of drug toxicology
What are the causes of attrition in drug development ?
Disrepancies with the animal models used in preclinical studies
Differences in the pathophysiology (immune diseases, CNS)
Differences in the drug toxicology and metabolism
Diffferences among humans in drug responses
Different genetic backgrounds
Differences difficult to predict
What are interesting observations made fromm NPCs derived from Twin-DS-iPSCs ?
Decreased number, impaired proliferation and increased cell death
Shift from neuronal to astroglial and oligodendroglial phenotype
Reduced number and length of neurites (axons and dendrites)
Reduced number of glutamatergic neurons
Increased DYRK1A expression and activity
What are the effects of inhibiting DYRK1A by shRNA ?
Imrpoved neurogenesis
Into what cells can T21-iPSCs be used to study ?
iPSCs from monozygotic twins discordant for trisomy 21 (D21-iPSCs & T21-iPSCs) can be used to study :
neural cells (cognitive impairment)
hematopoietic cells and B lymphocytes (AML, ALL)
skeletal muscles cells (muscle weakness)
trophoblastic cells (spontaneous abortion)
What is the challenge with differentiating embryonic stem cells into specialized cells ?
Finding the correct conditions (cytokines, growth factors, mediums) that drive the differentiation of an ECS into a mature cell
How do you generate chimeric mice ?
Inject iPSCs into the blastocyst
Transfer the blastocyst into the uterus of the recipient
Chimeric mouse
??? Profit
Briefly describe the diff. of iPSCs into EBs
iPSCs are suspended to form embryoid bodies (day 4)
They then are adhered to form differentiated tissue with all 3 germ layers (day 21)
What criterias define iPSCs ?
Morphology similar to ESCs
Unlimited self-renewal
Transgene silencing
Expression of pluripotency markers
In vitro diff. into derivatives of the 3 germ layers
What 3 methods exist to reprogram somatic cells into iPSCs ?
Retroviral or lentiviral transduction
Adenoviral transduction
Plasmid transfection
What factors were used to derive the first human iPSCs ?
Yamanaka induced pluripotent stem cells fromm human fibroblasts with 4 factors :
oct3/4
sox2
c-myc
klf4
What are induced pluripotent stem cells ?
A type of stem cell by reprogramming adult somatic ells into pluripotent stem cells. First done with mouse induced pluripotent stem cells by Yamanaka S. in Japan by identifying 24 candidate genes that play a pivotal role in the maintenance of ESC identity.
Briefly define mesenchymal stem cells
Origin in the bone marrow
gives rise to :
bone
fat
cartilage
They are currently being investigated for :
promoting angiogenesis
anti-inflammatory properties
stimulate endogenous cell formation
Briefly define gut stem cells (GSCs)
Origin in the small intestin
give rise to :
goblet cells
endocrine cells
columnar cells
Briefly define neural stem cells (NSCs)
Origin in specific areas of the brain
gives rise to :
neurons
oligodendrocytes
astrocytes (type 1 and 2)
Briefly define hematopoietic stem cells
Origin the bone marrow
Give rise to specialized blood cell types :
NK cells
Platelets
macrophages
etc.
What are commited progenitors ?
“transient amplifying cells”
multipotent
divide rapidly
no self-renewal
lead to specialized cells
Where and what is the role of tissue stem cells?
Found throughout the whole body to replace damaged or used up cells. They are multipotent as they can make multiple types of specialized cells, but not all.
Give an example of genome editing used in a human embryo
Crispr-Cas9 can be used to knock out the CCR5 gene, the “doorway” to HIV into human cells. Used by chinese professor for IVF with HIV-positive fathers
What is the status of human embryonic stem cells reserach in CH ?
Permissive with restrictions : hESC research is allowed with IVF embryos up to 7 days post-fertilization (informed consent). Cloning and creations of embryos for research is prohibited.
What are EBs composed of ?
Embryoid bodies are composed of derivatives of the 3 germ layers : ectoderm, mesoderm and endoderm
What are the “core regulatory circuits” that determine pluripotency ?
OCT3/4 : maintains self-renewancy of pluripotent stem cells
SOX2 : essential for embryonic dvlp. Downregulation of SOX2 leads to differentiation of ESCs
NANOG : Necessary to promote pluripotency in combination with OCT3/4 and SOX2
Give characteristics of embryonic stem cells in culture
Self-renewal (copying) : unlimited proliferation in vitro
Possibilty of obtaining an unlimited number of cells
Normal karyotype (if no chr. aberrations)
Proliferation as 2D colonies
Need of feeder cells (embryonic fibroblasts) or extracellular matrix (matrigel) to culture
Specific media needed for proliferation and pluripotency maintenance
Basic fibroblast growth factor (bFGF)
Give the characteristics of a blastocyst
Days 5-6
64 - 128 cells
trophoblast present
inner cell mass
Where are tissue stem cells found ?
In the fetus, baby and throughout life
Where are embryonic stem cells found ?
In the inner cell mass of the blastocyst, a very early embryo (5 to 14 days)
Classify each of these stem cells into the 4 known categories of stem cells : esc, ipsc, differentiated cells, zygote, adult stem cell.
Totipotent : zygote
Pluripotent : ipsc, embryonic stem cells
Multipotent : adult stem cell
Unipotent : differentiated cell
What are the 4 classes of stem cells ?
Totipotent stem cells : found only in early embryos, each cell can form a complete organism
Pluripotent stem cell : found in the undifferentiated inner cell mass of the blastocyst (5 to 14 days) and can form any of the 200 cell types in the body
Multipotent : derived from fetal tissue, cord blood and adult stem cells. These are already differentiated, but can form a number of tissues
Unipotent : able to contribute to only one mature cell type but still able to self-renew
Why do stem cells self-renew and differentiate ?
Self renewal : to maintain the stem cell pool
Differentiation : to replace dead or damaged cells throughout life
What are the 2 charcteristics of stem cells ?
Capable of self-renewal (copying)
Differentiation into specialized cells
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