Session 4 - healing and repair Flashcards
Where are the differentiated cells of regeneration derived from?
-Stem cells
What is asymmetric division?
-The division undergone by stem cells; One daughter cell remains as a stem cell and the other differentiates into a specialist cell type
Define unipotent
-Cells only produce one type of differentiated cell, eg epithelia
Define multipotent
-Can produce several types of differentiated cell, eg haematopoietic
Define totipotent
-Can produce any type of cell eg embryonic stem cell
What is a labile cell population?
-A cell population which undergoes rapid active proliferation eg epithelia
What is a stabile cell population?
- A population of cells which are in a resting state, yet have the ability to exit G0 and enter the cell cycle
- Eg renal tubule epithelium/hepatocytes
What is a permanent cell population?
-The cels are unable to divide and thus unable to regenerate
What are the two main factors which control regeneration?
- Growth factors
- Contact between basement membrane and adjacent cells
How do growth factors control regeneration?
-Promote proliferation in the stem cell population via extracellular signals which are transduced into the cell and control the expression of genes which control cell cycle
What type of molecules are growth factors?
- Hormones (eg oestrogen,testosterone, GH)
- Proteins (EGF, PDGF, FGF)
How does contact with basement membranes and adjacent cells control regeneration?
- Contact inhibition -> signalling through adhesion molecules inhibits proliferation in intact tissues
- Loss of contact promotes proliferation
What are E-cadherins?
- Calcium-dependant adhesion transmembrane proteins which dimerise with E-cadherins of other cells and link the actin cytoskeletons together
- Play a role in contact inhibition through regulatory proteins
What is fibrous repair?
-Replacement of functional tissue by scar tissue
When does fibrosis repair and scarring occur?
- When there is cell injury to permanent populations
- When the collagen framework is destroyed in labile and stable cell population
What are the three key components of fibrous repair?
- Cell migration
- Angiogenesis
- Extracellular matrix production and remodelling
What tissue forms before fibrous repair?
-Granulation tissue
What cell types migrate during fibrous repair?
- Inflammatory cells (neutrophils/macrophages/lymphocytes)
- Endothelial cells
- Fibroblasts/myofibroblasts
What role do inflammatory cells play in fibrous repair?
- Responsible for phagocytosis of deris
- Release chemical mediators to influence repair
Why do endothelial cells migrate to the site of injury in fibrous repair?
-For angiogenesis
Why are fibroblasts/myofibroblasts involved in fibrous repair?
- Extracellular matrix production
- Wound contraction
What is angiogenesis?
-The development of a new blood supply
Why is angiogenesis critical in wound healing?
- Delivery of oxygen and nutrients
- Provides access for inflammatory cells and fibroblasts