Chronic inflammation and wound healing Flashcards
Complete resolution of acute inflammation has what outcomes?
- Return to normal vascular permeability
- Drainage of proteins and fluid into lymphatics
- Drainage into macrophages
- Phagocytosis of degenerative neutrophils and necrotic debris
- Disposal of macrophages
Under what specific conditions does chronic inflammation occur?
- Persistent infections with e.g. parasites, fungi
- Prolonged irritation
- Cellular immune response, autoimmunity
- Viral infections
Which cells are involved in active inflammation?
- Macrophages
- Lymphocytes
- Plasma cells
Which cells characterise chronic inflammation?
Macrophages
Why do macrophages accumulate in chronic inflammation?
- continued recruitment of monocytes
- local proliferation of macrophages
- immobilisation of macrophages by cyokines
What are the main essential roles of macrophages during chronic inflammation?
- Phagocytosis
- Antigen presentation (MHC II)
- Secretory functions
- Wound healing
- Regulation of monocyte and granulocyte pools
What is a plasma cell?
An Ig producing differentiated B-cell
Out of neutrophils and macrophages, which is mitotically active?
Macrophages
Which cell type is terminally differentiated when arriving at the site of injury?
Neutrophils
What happens to macrophages when they arrive at the site of injury?
They differentiate into tissue macrophages, which get activated by inflammatory stimuli
Tissue destruction is induced by…?
Inflammatory cells
What are the main repair/regeneration steps?
- connective tissue replacement of damaged tissue
- proliferation of small blood vessels (angiogenesis)
- fibrosis (scarring)
What does regeneration vs repair depend on?
- how severe the injury is
- whether there is damage to the basement membrane or not
- type of tissue that is injured, some are better at regeneration
What are labile cells?
Continuously dividing cells due to a population of stem cells e.g. epidermis, GI tract
What are stable cells?
Quiescent cells (dormant, low levels of replication)
Proliferate in response to injury
e.g. liver hepatocytes
What are permanent cells?
Non-diving cells, cannot undergo mitosis
e.g. skeletal muscle cells
What is the role of growth factors in regeneration and repair?
Work via receptors and initiate signalling pathways that influence the cell cycle
Cause proliferation of epithelial cell, parenchymal cells, and fibroblasts
Define scarring
Deposition of collagen fibres as an attempt to replace lost tissue by fibroblasts
When does scarring occur?
With tissue destruction including damage to both parenchymal cells and stromal framework
Describe the formation of granulation tissue
- begins from approx 24hrs after injury
- fibrin is an essential framework
- contains small new blood vessels and proliferating fibroblasts
- inflammation still present
- oedematous
What are the main steps of angiogenesis?
- Degradation of basement membrane
- Migration of endothelial cells
- Proliferation of endothelial cells
- Recruitment of periendothelial cells
What is VEGF?
Increase in vascular permeability which leads to an increased deposition of fibrinogen and fibronectin in EMC
Which factors from inflammatory cells trigger fibroblast migration and proliferation?
GFs, IL-1, TNF
What are the 5 main steps of scarring?
- formation of granulation tissue
- angiogenesis
- migration and proliferation of fibroblasts
- extracellular matrix deposition
- tissue remodelling
