Regeneration Flashcards
where do embryonic stem cells come from?
the blastula
what are the 4 sources of adult stem cells and what cells do they produce?
mesenchymal cells that form bone cells, cartilage cells and fat cells
blood stem cells that form red blood cells, white blood cells and platelets
satellite cells that form muscle cells
germ cells that form oocytes and sperm
what is a stem cell niche?
special environments that allow stem cells to be maintained
what cells form from the dermis and basement membrane?
keratinocytes
where is the stem cell niche that produces skin cells?
the basal layer of the epidermis
how does the signalling molecule Wnt maintain stem cell population?
inhibits differentiation
where is Wnt released from?
the dermis
what causes stem cells in the skin to be released and allowed to differentiate?
notch signals that inhibit integrins that anchor keratinocytes to the basement membrane
how does EGF maintain the skin stem cell population?
inhibits notch activity so cells don’t differentiate
what are the 2 stem cell niches for hair follicles?
the bulge and the dermal papilla area
what is the stem cell niche for cells lining the gut?
the crypt cells
supported by sub-mucosal cells
why do cells lining the gut need to be replenished constantly?
the gut is a harsh alkaline environment
how do stem cells divide?
the cell divides to produce 2 daughter cells, one is a stem cell and one is a trans-amplifying cell
what is a trans-amplifying cell?
a cell that will divide into 2 differentiating cells
how do stem cells divide by population asymmetry?
the cell can divide to form 2 stem daughter cells (less common)
it can divide to form one stem cell and one differentiating cell (most common)
it can divide to form 2 differentiating cells (less common)
what causes junctional epidermolysis bullosa (JEB) and what is the main symptom?
mutations in adhesion genes such as LAMB3 that help adhere the dermis and the epidermis
skin blistering and peeling
which 2 genes are markers for stem cells?
Bim1
Lgr5
in somatic cell nuclear transfer which donor is the embryo genetically identical to?
it is genetically identical to the egg donor but not the nuclear donor
what is the role of the signals BMP and noggin?
BMP allows stem cells to become trans-amplifying cells
noggin inhibits BMP to maintain the stem cell population
what is lineage tracing used for and how does it work?
used to show the fate of a cell
it is done by making a transgene that is controlled by the promotor for Lgr5
a marker called beta galactosidase turns blue if the cell contains the transgene
how can embryonic stem cells be cultured from mice?
- take the blastocyst from pregnant mice
- isolate and culture the epiblast cells
- maintain the embryonic stem cells using BMP (which in this case promotes stem cell identity) and LIF
what is the role of BMP and LIF in mice embryonic stem cells?
maintain the expression of epiblast markers which prevent differentiation
what happens if you remove BMP and LIF from cultured embryonic mice stem cells?
they will differentiate into different cell types under specific conditions
how do induced pluripotent stem cells form
genetically engineer adult differentiated cells to express pluripotency markers using an inactivated virus
how are chimera mice made?
mixing embryonic stem cells with a normal embryo to make different tissues in the adult mouse
they will have a mixed genetic identity
what is a teratoma and how can it to be used to study cell differentiation?
a type of benign cancer tumour that contains different tissues and can produce many different stem cells
the embryonic stem cells can be directed to adopt different cell fates using specific conditions
what is somatic cell nuclear transfer?
this is when the nucleus from an egg (host) cell is removed and replaced with a nucleus from a donor cell
the embryo produced from the egg cell is genetically identical to the donor
how was somatic cell nuclear transfer used to clone frogs?
scientists removed skin cells from an adult frog and grew them in a petri dish
they took an unfertilised egg cell from another frog and removed the maternal nucleus using UV
they transferred the nucleus from the skin cells to the egg cell
they fertilised the egg and it grew into a tadpole that was genetically identical to the adult frog
how did scientists discover blastula nuclei are totipotent?
the tadpoles produced from somatic cell nuclear transfer using blastula nuclei grew into adult frogs compared to the tadpoles produced from the nuclei of adult frogs which didn’t
how can in vivo drugs be used in regenerative medicine?
they induce tissues surrounding the damaged tissue to form stem cells and repair the damage
what is the function of the Pdx1 gene?
it regulates pancreatic cell differentiation
how can diabetes be treated using iPS cells?
cells are taken from the patient and cultured using somatic cell nuclear transfer
the cells are grown into a blastocyst to produce embryonic stem cells which are harvested and cultured
the iPS cells can be programmed to differentiate into insulin-producing cells that express Pdx1 and are injected into the patient
what are clonal cells?
a group of genetically identical cells that share a common ancestry (all derived from the same cell)
what are organoids?
small, 3D organs or tissues that self-assemble from stem cells
what is regeneration in biology?
the ability of organisms to restore damaged or diseased structures in form and function
what are the two types of regenerative biology?
morphallaxis and epimorphosis
what is morphallaxis?
where cells are taken and reprogrammed to replace the missing tissue without proliferation
what is epimorphosis?
where regenerative cells form and proliferate to grow out and replace damaged tissue
what happens when tissue is damaged in the immediate wound response?
ATP is released from damaged cells and binds to receptors on adjacent cells
calcium ions are released to increase intracellular calcium levels
hydrogen peroxide is released
what happens during the wound response?
- hydrogen peroxide release causes cytoskeletal changes to close the wound, cells on the edge connect and the cytoskeleton contracts to close the wound
- immune cells are recruited to the wound to prevent pathogens entering, neutrophils migrate to the injury from the bloodstream and form a scrum
- regeneration or scar formation is initiated depending on the regenerative capabilities
how does fibrosis (scarring) happen?
fibroblasts secrete high levels of extracellular matrix
what can humans regenerate?
a small amount of bone, skin, muscle and liver
what is the role of the BMP ligand?
skeletal development
when beads soaked in BMP were added to the tip of a mouse’s finger the limb grew
how do salamanders regenerate?
there is the wound response and the wound closes over
epithelia at the end of the stump thickens and secretes signals into the rest of the limb inducing de-differentiation of cells surrounding the wound
blastemal cells proliferate and re-differentiate to reform the limb in the correct identity
how are blastemal cells formed in salamanders? (there are 2 ways)
multipotent blastemal cells differentiate into the correct cell type
cells surrounding the injury trans-differentiate and migrate to the correct location
how do planaria regenerate?
they can go through whole-body regeneration
they contain adult stem cells called neoblasts that are scattered through the animal
they can be pluripotent or lineage restricted
they use epimorphosis for head regeneration and morphallaxis for the rest of the body
how do hydra regenerate?
they have two germ layers and adult stem cells called interstitial cells
they are continuously growing as interstitial cells form buds that grow into new tissue
