2 Stem Cells & Tissue Engineering Flashcards
What are the SIMILARITIES between determination & differentiation? (3)
1) both result not from changes in genes, but changes in gene EXPRESSION (except for immune system & gametes)
2) both result from alteration in chromatin structure and transcription factor expression
3) both are often quite permanent and heritable through many cell divisions
What are the DIFFERENCES between determination & differentiation?
1) Determination occurs prior to overt differentiation
2) Differentiation results in the cell’s acquisition of functional properties (via shape polarity, orientation w respect to neighbours, appropriate organelles & proteins which enable it to carry out metabolic signalling, transport or contractile functions required in a particular tissue, etc.)
Define cell plasticity.
Cells that are normally committed to one lineage can be switched to a different lineage pathway
What are the 3 processes in which cell plasticity may be observed? Define them.
1) TRANSDIFFERENTIATION: conversion of 1 mature cell type to another mature cell type
2) METAPLASIA: conversion of 1 tissue type to another tissue type
3) DE-DIFFERENTIATION: reversion of a mature cell to a stem or progenitor state
- optional- 4) REPROGRAMMING of a cell of any potency to pluripotency (iPS)
Under what conditions can plasticity be observed? (2)
1) Tissue damage and regeneration
2) Experimental induction via ectopic expression of master regulator transcription factors (iPS)
Give an example of metaplasia occurance.
BARRETT’S OESOPHAGUS
CAUSE: GI reflux (acid reflux from stomach) causes tissue damage
EFFECT: squamous epithelial lining of oesophagus is converted into something resembling intestinal lining
Define the capabilities of a TOTI-, PLURI-, and MULTIpotent cell.
TOTI: can give rise to a new individual given apropriate maternal support
* restricted to very early stages of development (max. morula/blastula)
PLURI: can give rise to all types of adult tissue cells + extraembryonic tissue (cells which support embryonic development)
MULTI: can give rise to several types of mature cells
What are the 3 types of adult tissues / adult stem cells / tissue stem cells? Give explanations and/or examples where possible.
1) CONTINUOUSLY renewing
e. g. bone marrow, skin
2) CONDITIONALLY renewing: turnover still occurs but at a much slower rate; unless tissue damage occurs, SCs or other mechanisms to replace damaged cells are quiescent.
e. g. liver, kidney
3) NON renewing: actually just extremely slow turnover
e. g. cardiac muscle
What is the definition of a stem cell? (2013 Q6a, 6m)
Hint: 2 key properties
A primitive cell which can either self-renew or give rise to more specialised cell types i.e. SCs are the ancestors at the top of family tress of related cell types.
What are the characteristics of stem cells? (8)
1) capable of self renewal and differentiation
2) responds to signals which regulate their growth & proliferation, enabling them to meet changing demands
3) may give rise to transit amplifying cell compartment(s)
4) are often lacking specialised organelles / show high nucles:cytoplasm ratio
5) contain long-lived expressed telomerases
6) are slowly dividing
7) few in number / form a minority component in tissues
8) may be restricted spatially to specific zones / niches e.g. gut’s crypt
What is a transit amplifying cell compartment?
An area containing cells which are not fully differentiation but still multiplying, essentially amplifying the number of cells heading towards a particular lineage.
What markers can be used to identify specific differentiation stages in cell linaeges? (4)
1) transcription factors
2) cell surface moleucles
3) cytostructural molecules e.g. intermediate filaments
4) specific functional gene products
The discovery of novel stem cell populations disproved the previously held notion that some tissues are static. List the findings on adult neurogensis as discussed in lectures. (3)
1) occurs in subventricular zone (SVZ) & hippocampus
2) new neurons from the SVZ wind up in olfactory epithelium
3) hippocampal neurogensis may have a role in learning & memory
What are the 4 types of differentiated gut cells and their function(s)?
1) ENTEROCYTES: absorb digested food i.e. macronutrients
2) GOBLET CELLS: produce mucin, which protects the intestinal lining from its contents
3) ENTEROENDOCRINE CELLS: produces gut hormones
4) PANETH CELLS: produces defensins & lysozome of the innate immunity
What is a stem cell niche? (2012 Q5b, 3m)
A very speicifc micro environment
- containing cells producing extrinsic factors to
- exert precise control over SC renewal & differentiation.
