Stem Cells I Flashcards
What are stem cell characteristics
Not terminally differentiated, divide w/o limit, renewal of themselves, option to remain stem cells or differentiate, and slow division
What is totipotency
Form a whole organism/organ system. Includes embryonic and extra-embryonic tissues. Ex: zygote, placenta to help embryo survive
**ability of a cell to give rise to all cells of an organism, including embryonic and extra-embryonic tissue eg zygote
What is pluripotency
Give rise to cells in embryo and adult tissues ex embryonic stem cells
**ability of a cell to give rise to all cells of the embryo and subsequently adult tissues eg embryonic stem cells
What is multipotency
Present in a particular organ system ex brain cells give rise to many different cell types but these cells are only specific for the brain (adult stem cells)
**ability of a cell to give rise to different cell types of a given lineage eg adult stem cells
What is asymmetric division in the maintenance of stem cells?
Creates 2 cells. 1 of the 2 cells will get determinant which maintains stem cells renewal and maintain population. Other without determinant thus differentiates
Whats is independent choice in the maintenance of stem cells?
Division makes 2 identical cells but outcome is random and/or influenced by the environment. Ie.both cells can be stem cells or both differentiate or one stem cells and one differentiate. (Various combinations and explains sharp increase in stem cells when needed for repair)
What are differential internal signals?
Gene expression; controlled by the cell’s genes
What are the differential external signals?
Controlled by the cell’s microenvironment. We can control the microenvironment ie chemical secretion, physical contact, molecules such as: ECM, GFs, O2 tension, ionic strength, pH and ATP
What are founder stem cells?
Proportions of the parts of body are determined early in development, an organ/tissue has fixed # of founder cell populations programmed to have fixed # of cell divisions
Adult organs need to be renewed. Accomplished via:
Founder stem cells dividing giving rise to 1 daughter cell that remains a stem cell and a set of cells that have a set # of transit amplifying divisions
Founder cells are programmed to divide a finite number of times ie transit amplifying divisions. T/F?
True
Adult stem cells aka multipotent are designed for what?
Forma s internal repair system
The epidermis is for:
Outer layer protection and response to stimuli; stratified layer make of keratinocytes
Dermis is rich in:
Collagen to provide toughness
Hypodermis:
Fatty layer to keep us warm
What prompts the cells in the basal layer to divide?
Will stay as stem cells if cells are in contact with basal laminal. If lose contact, will differentiate
Basal cell layer contains:
Stem cells (dividing cells)
Prickle cell layer:
Have numerous desmosome that attach tufts of keratin filaments
Granule cell layer:
Apoptotic signals, waterproof barrier, forms boundary between the inner metabolically active strata and outer dead epidermis cells
What are some examples of multipotent cells?
Epidermal, intestinal, hematopoeitic, neural stem cells
Basal cells are the dividing cells. Some divide and maintain layers and others migrate to layers above. T/F: change in gene expression w/ each step of differentiation as migrates to layers
True. As migrate, undergo partial degradation where dependent on partial activation of apoptotic machinery
Proliferative potential of epidermal stem cells directly correlates with expression of:
Beta-1 subunit of integrin (controls size of stem cell population. Beta-1 integrin expression goes down with loss of contact with basal lamina)
What are the factors governing renewal of epidermis?
RATE of stem cell division
PROBABILITY that one of the daughter cells will remain a stem cell
Rate of division of TRANSIT AMPLIFYING CELLS
TIMING OF EXIT from basal layer and time to differentiate and eventually slough off
Over-activation of hedgehog =
Lose control/dividing more than necessary
Deficit of hedgehog signal=
Loss of sebaceous glands ie baldness
Up-regulation of Wnt signaling =
Tumors extra hair follicles develop
Loss of Wnt signaling =
Failure of hair follicle development
Notch signaling restricts=
Restrict size of stem cell population (lateral inhibition = transit amplifying cells)
TGF-beta =
Repair. Divide more than normal = scar tissue
Regulation of epidermis renewal via:
Contact with basal lamina mediated by integrin signaling (maintenance that include stem cell markers and proliferative potential that directly correlates with Beta-1 subunit of integrin). Helps to control size of stem cell population
Hair grows upward from
Dermal papilla
Sebaceous glands secrete oily liquid called
Sebum
Hair follicle undergoes cycle of:
Growth, regression, and rconstruction
Hair follicle stem cells present in:
Bulge that help in reconstruction
ECM secreted by _ provide what type of support?
Secreted by fibroblast provide mechanical support
What supplies nutrients and oxygen and removes waste products?
Blood vessels lined with endothelial cells
What provides defense against microbes in the skin
Macrophages and dendritic cells
Lymphocytes provide:
Adaptive immune response
Nerve fibers of the skin provide:
Sensory information
What are transit amplifying cells?
Cells mixed with stem cells and other cells that divide frequently. Programmed to divide for a limited number of times.
