Lecture 35. Tissue Homeostasis Flashcards
What forms the basis for tissue homeostasis and repair?
Tissue stem cells
What are tissue stem cells?
Rare cell types, in a specific niche, that can renew themselves over the life time of the organ and produce ‘ daughter’ cells - differentiate into one or more cell lineages.
What are the two essential properties of stem cells?
- Self renewal - proliferate without limit
- Potency - the resulting cells can either remain as a stem cell or will become committed to terminal differentiation
Totipotent stem cells
May be able to generate all possible differentiated cells e.g fertilised egg cell - zygote
Pluripotent stem cells
Limited range of differentiated cells e.g embryonic stem cells
Oligopotent stem cells
Few or just one cell type e.g epidermal stem cell
What are transit amplifying cells?
Cells committed to going through a specific number of divisions before terminal differentiation
Do all keratinocytes have potential?
No
Which keratinocytes have potential
Those that have a higher level of β1 integrin protein
When is the pattern of organ growth/size laid down and what signals does this process use?
During embryonic growth via short-range signals
What three fundamental processes determine organ/body size?
Cell division
Cell growth
Cell death
Mitogens
Remove the hand-brake on the cell cycle - cell division
Growth Factors
Increase cell mass - protein synthesis
Survival Factors
Suppression of apoptosis
What does Epidermal Growth Factor (EGF) do?
Stimulates cell growth and differentiation - EGFR
What does Fibroblast Growth Factor (FGF) do?
Cell proliferation and differentiation – FGFR, interacts with cell-surface-associated heparan-sulfate proteoglycans
What does the Wnt signalling pathway involve?
Involves series of proteins passing signals from cell surface receptors to nucleus
Gene expression and cell-cell communication
Consequences of losing the Wnt signalling pathway
Loss of hair follicles
Consequences of overexpressing the Wnt signalling pathway
Excessive follicle growth and tumours
What is tissue growth dependent on?
Dynamic process of vascularisation
What happens in vasculogenesis?
Early embryonic endothelial cells form the first primary blood vessels
What happens in angiogenesis?
The first primary blood vessels form an elaborate network of vasculature branching to every finer vessels is created
The process of angiogenesis
1) First the basal lamina of existing vessels break down.
2) Endothelial cells (EC) migrate into the interstitial space.
3) Endothelial cells proliferate.
4) The lumen develops and matures
5) Vessel is stabilised by pericyte recruitment
