Stem Cells Flashcards
3 Stages of cells
Stem cell
Transit-amplyfing cell
Differentiated cell
Stem cell
Cell that can continuously produce unaltered progeny cells (self-renewal) and also has ability to produce progeny cells that have different more restricted properties (specialization)
Transit-amplifyng cell
Proliferative stem-cell progeny fated for differentiation (cells can proliferate but not forever)
Differentiated cells
Cells which make necessary functions
progenitor cells
stem cells and transit amplifying cells
Generic term for any dividing cell w/ capacity to differentiate; includes putative stem cells which have not yet demonstrated self-renewal
Main properties of stem cells
- long term self-renewal
- increased proliferative potential (can proliferate alot)
- capacity to multilineage differentiation (differentiation -> different lineages)
- multi-drug resistnat (need protection bc immature/ developing so resistant)
- Telomerase expression (higher telomerase lets cells proliferate)
embryonic stem cells
pluripotent stem-cell lines derived from early embryos b4 formation of tissue germ layers
adult (tissue) stem cells
derived from or resident in fetal or adult tissue w/ potency limited to cells of that tissue; these cells sustain turnover and repair throughout life in some tissues (present all the time in adult and embryo, maintain integrity of who organism)
Degrees of potency
Totipotent -> pluripotent -> multipotent -> oligopotent -> unipotent
totipotent
sufficient to form entire organism (can produce everything during formation) ex zygote, plant meristem cells
pluripotent
able to form all bodies cell lineages including germ cells and some or all extraembryonic cell types (ex embryonic stem cells)
Multipotent
can form multiple lineages that constitute an entire tissue or tissues (ex hematopoietic stem cells)
* can’t do all 3 germ layers
oligopotent
able to form 2 or more lineages with in a tissue; ex neural stem cell that creates subset of neurons in brain
unipotent
forms single lineage (spermatogonial stem cells)
Stem cell hierarchy
Totipotent Zygone Pluripotent Blastocyst (inner cell mass -> embryonic stem cells -> germ layers) (also primordial germ cells -> embryonic germ cells) Multipottent (CANT do all 3 germ layers( Progenitor organs
ESC
embryonic stem cells; harnest 2-3 days mouse can culture and grow in lab or can transfer to adult mouse
ECC
embryonic carcinoma cells, will reduce tumors; harvest 3-7 days mouse
EGC
embryonic germ cells; harvest 9-13 days mouse
Chimeric mice
test embryonic stem cell potential by generation of chimeric mice followed by germ line transmission (put stem cells from gray mouse and black mouse in blastocyst and alter embryo and end up with chimeric adult mouse with cells from 2 mouse strains should make grey (unicolor) and black (unicolor) offspring with black mouse
Shows embryonic stem cells can -> complete mouse
Human pluripotent embryonic stem cells
derived from in vitro cultured cells of inner cell mass in blastocyst after fertilization (day 5-7)
Human pluripotent embryonic germ cells
derived in vitro cultured cells of primordial germ cells of fetus at weeks 5-7
Stem cells as source of cells and tissues
want cells as source of particular source of tissue (direct cells -> some tissues)
problems with human embryonic stem cells
- very small cells hard to collect large number blastocyst to establish new embryonic stem cell lines
- limited number and poor quality of available cell lines
- possibility of immune rejection
- ethical concerns
sources of adult stem cells
generally focus on getting bone marrow cells; bone marrow cells are very useful
How can we identify adult stem cells
- immunodetection assay
- functional properties like enzymatic activty
- label retention
- formation of monoclonal spheres/ organdies in several consecutive rounds of dissociation and regeneration
- formation of complete tissue after signal cell transplantations in several consecutive rounds of dissociation and regentation
- cell linage (fate) tracing
characterization of adult stem cells
- purify a population of cells (w/ specific cell surface markers)
- transplant a single cell into host (serial dilutions of cell populations)
- observe self-renewal and reconstitution of tissue organ or lineage of origin (serial transplantation)
cell linage tracing
have genetic label particular cell and see what happens over certain period of time; self renewal- can do it several times in serial transplantations)
Adult stem cell locations
not located on their own they are in their own microenviornments
- intestinal crypt
- hair-follicle bulge
- corneal limbus
- mammary gland terminal end bud
intestinal stem cells regulated by
adjacent cells b/c ligands and signaling pathways which produce WNT gives signal to stem cells to proliferate
- WNT- responsive crypt stem cell between WNT-producing Paneth cell and WNT-producing stroll cell
WNT off
Absence of Wnt destruction complex consisting of Axis, APC, and GSK3 in cytoplasm binds to and phosphorylates beta-catenin which is degraded; Dvl (disheveled) required for activating pathway as well, in nucleus TCF (tissue cell factor) in inactive state bc bound to Groucho
WNT on
Binding WNT to frizzled and Lrp5/6 receptors induces association of axin w/ phosphorylated lipoprotein receptor protein (LRP) destruction complex falls apart Beta-catenin is stabilized binds TCF in nucleus -> up regulation target genes including Axin2 and Lgr5
bone marrow transplant
kill hematopoietic stem cells in body and put in donor marrow and reconstitute hematopoietic stem cells
inside patient:
stem cell -> multi potential stem cell -> myeloid progenitor cell -> erythrocytes (RBCs)
Regenerative potential stem cells
epidermal and corneal epithelium (corneal regeneration grow corneal cell and transplant them)
Holoclone
stem cells
meroclone
cells with intermediate differentiation
paraclone
differentiated cells
gene therapy to treat epidermolysis bullosa
genetically modify epidermal cells infect with LAMB3 cells and grow on plate than transplant to human body; several types of cells initially present then over time get to more differentiated cells
Concentrated bone marrow aspirate imroves
full thickness cartilage repair in horses; transplant mesenchymal stem cells fix cartilage in horses
Embryonic vs adult stem cells
Embryonic Stem Cells Adult Stem Cells
Cells obtained from inner Cells obtained from
Cell mass of blastocyst specific fetal and
And primordial germ cells postnatal tissues,
Of aborted fetuses includes umbilical
cord and placenta
Pluripotent- flexible, give rise multipotent- give
To any cell type in the body. rise to multiple but
limited cell types
Difficulties to collect a large limited potential for
Number of blastocyst and to differentiation;
Establish new embryonic stem difficulties to get
Cell lines; limited number and sufficient amounts
Poor quality of available of cells from some
cell lines Ethical concerns organs (ie can’t take
brain cells from
someone)
* both share possibility of immune rejection*
Induction of pluripotent stem cells from
adult human fibroblasts by defined factors (if you take TFs (transcription factors and put them in hydroblasts these factors will be expressed in cells and will get human induced pluripotent stem cells and can then get human embryonic stem cells
pluripotent stem cells induced from adult human dermal fibroblsats
in humans can take cells inject in mouse and will form teratoma (all 3 germ layers) which shows by most parameters pluripotent stem cells from adult are v similar to embryonic stem cells
stem cells and lung cancer
the hope is you will be able to take healthy cells IiPS) cells from lung grow a regenerated organ from the iPS cells and put it in there person
beaten cardyomyoctes
derived from human induced pluripotent cells
Medical application of iPS cells
the hope is that you can take skin biopsy take patient specific iPS cells and either use gene targeting to repair disease-causing mutation and get healthy cells to transplant back into human or can take affect cells screen for therapeutic compounds treat with drugs and transplant back into patient
how do you get pluripotent cells
you can reprogram mature cells
iSP
induced pluripotent cells (get these by reprograming mature cells)
problems with induced pluripotent cells
- Human iPS cells and ES may not be identical (majority are very similar)
- Potential of malignant transformation due to reprogramming factors (c-Myc and Klf4 are oncogenes)
- if iPS cells can form entire embryo do they represent human life similar to ES cells as some believe (no answer?)
Fibroblats + transcription factors Gata4, Mef2c, and Tbx5
functional cardiomyocytes (transcription factors lead to specific tissue targets)
Engineering cell identity
can direct differentiation to certain cell types which you can then transplant into a patient; this is not ready for clinical application yet
future of stem cell studies
How to
- Isolate (eg using cell surface markers)
- grow, maintain, store
- differentiate (all into muscle or neurons)
- make an organ (combination of different cell lineages in 3D cultures)
- use therapeutically (regeneration and gene therapy)
- Avoid malignant transformation
- Address ethical concerns
