Lecture 18: Repair and regeneration Flashcards
What is regeneration?
Cells can regrow
Restoration of normal structure and function
What is repair?
Cells cannot regrow
Scar formation
Loss of function
After injury and acute inflammation, what pathways can be taken?
Regeneration
Repair
Chronic inflammation
Two most important factors determining outcome of injury?
- ability of the cells to replicate
- ability to rebuild complex architectural structures
What different cell types in the repair / regeneration of cells cycle?
- Continuously cycling labile cells
2 Permanent Cells - Quiescent stable cells
What different cell types in the repair / regeneration of cells cycle?
- Continuously cycling labile cells
2 Permanent Cells - Quiescent stable cells
What is the labile cell population and characteristics?
High normal turnover
Active stem cell population
Excellent regenerative capacity
Example: Epithelia
What is the stable quiescent cell population and characteristics?
Low turnover
(physiological)
Turnover can massively increase
(if needed)
Good regenerative capacity
Example: liver, renal tubules
What is the permanent cell population and characteristics?
No turnover
(physiological)
Long life cells
No regenerative capacity
Example: neurons, striated muscle cells
Stem cell characteristics?
Prolonged self-renewal
Asymmetric replication
Reservoirs in many adult tissues
How do Stem cells form?
- Terminal
differentiation
2.Differentiating
compartment
3.Amplifying cell
compartment
What is the population of Stem cells?
Present in many labile and stable cell populations
Located in specific areas (basal)
Survival = crucial to regeneration
Give an example of the rebuild of complex architectures which is limited?
Glomeruli, lung
An example of when survival of connective tissue is essential?
Cirrhosis
How does complete restitution occur?
Loss of labile cell population can be completely restored
e.g minor skin abrasion
Cells at edge of defect multiply to cover defect
What is contact inhibition?
when cells cover defect proliferation stops
What is complex regeneration controlled by?
growth factors
cell-cell interactions
cell-matrix interactions
These mechanisms are lost in neoplasia
What does regeneration depend on?
tissue cell kinetics
architecture
stem cell survival
how does healing by regeneration affect specialised function?
Restitution of
specialised function
How does healing by repair affect specialised function?
Loss of specialised
function
What happens during repair of cells/tissues?
Normal structure cannot be replaced
Healing by non-specialised fibrous tissue (‘Scar’)
Functional consequences
What is Organisation?
the repair of specialised tissue by formation of a fibrous scar
What is an example of organisation?
Example = common consequence of pneumonia and infarction
Organisation characteristics?
Basic stereotyped pathological process
Production of granulation tissue (often on scaffold of fibrin)
Removal of dead tissue by phagocytosis
Granulation tissue contracts and accumulates collagen
Scar forms
Organised area = firm and puckered
