regeneration and repair

Question 1

outline the differences between bodily regeneration and bodily repair

Answer 1

resolution:
- initiating factor removed
- tissue undamaged or able to regenerate
repair:
- initiating factor still present
- tissue damaged and unable to regenerate

Question 2

describe the process of healing by first intention and outline the steps of this process.

Answer 2

• haemostasis - platelets and cytokines forms a haemotoma and causes vasoconstriction - limiting blood loss to the area
• the closed wound edges allow for easy clot formation
• inflammation - to remove any cell debris or pathogens
• proliferation - inflammatory cells release cytokines which cause fibroblasts to proliferate to form granulation tissue
• angiogenesis occurs (formation of blood vessels)
• fibroblasts produce collagen
• remodelling - collagen fibres deposited in the wound

Question 3

describe the process of healing by secondary intention and outline the steps of this process.

Answer 3

• haemostasis - a large fibrin mesh fills the wound
• inflammation - larger amount
• proliferation - granulation tissue forms at the bottom of the wound - once this grows and fills the wound, only then can the epithelia grow
• remodelling - would contraction may occur and inflammatory responce begins to resolve

Question 4

what is an important cell for wound contraction during secondary intention healing?

Answer 4

• myofibroblasts
• theyre modified smooth muscle cells
• contain actin and myosin
• also deposit collagen

Question 5

name the cells which can regenerate

Answer 5

• hepatocyes
• pneumocytes
• all blood cells
• gut epithelium
• skin epithelium
• osteocytes

Question 6

name the cells which cannot regenerate

Answer 6

• myocardial cells
• neurons

Question 7

briefly outline the different steps involved in the physiological processes of tissue repair and inflammatory resolution

Answer 7

Hemostasis:
Blood clot formation to stop bleeding and provide a scaffold for repair.

Inflammation:
Immune cells clear debris and pathogens, releasing signals for repair such as cytokines, chemokines and growth factors

Proliferation:
Fibroblasts and endothelial cells proliferate to form new tissue and blood vessels (angiogenesis).

Granulation Tissue Formation:
New connective tissue and capillaries fill the wound area.

Matrix Deposition:
Fibroblasts produce extracellular matrix components (e.g., collagen) for structural support.

Epithelialization:
New epithelial cells cover the wound surface.

Inflammatory Resolution:
Anti-inflammatory signals promote immune cell clearance and tissue homeostasis.

Remodeling (Maturation):
Collagen and other matrix components are reorganized to restore tissue strength and function.

Question 8

list the factors that can inhibit tissue healing and inflammation resolution.

Answer 8

• Chronic Inflammation
• Infection
• Poor Blood Supply (Ischemia)
• Malnutrition
• Diabetes
• Age
• Corticosteroid Use (Steroid Medications)
• Smoking

Question 8

outline the whole process of tissue repair and inflammatory resolution.

Answer 8

Hemostasis:
- Cells: platelets
Molecular mechanism:
- Thrombin activates platelets and triggers clot formation by forming fibrin from fibrinogen
- Fibrin forms clot matrix

Inflammation:
- Cells: neutrophils and macrophages
Molecular mechanism:
- Endothelial and immune cells release TNF-a, IL-1 and IL-6
- Chemokines attract neutrophils
- Prostaglandins and laukotrines amplify inflammatory response

Proliferation (tissue formation):
Cells:
- Fibroblasts – secrete collagen to form tissue
- Endothelial cells – angiogenesis
Molecular mechanism:
- VEGF – stimulate endothelial cell proliferation and angiogenesis
- PDGF and fibroblast growth factor – stimulate fibroblast migration and ECM synthesis
- TGF-beta – promotes fibroblast activation, ECM deposition, and tissue remodelling

Granulation tissue formation:
- Cels: fibroblasts, endothelial cells and a growing ECM, macrophages
Molecular mechanism:
- VEGF and FGF continue to promote angiogenesis and fibroblast activity allowing the formation of granulation tissue
- TGF-b supresses excessive inflammation

Tissue remodelling and maturation:
- Cells: fibroblasts model ECM by producing collagen and mature endothelial cells stabilize blood vessels formed during angiogenesis
Molecular mechanism:
- Matrix metalloproteinases break down the provisional ECM to allow remodelling and tissue maturation
- TGF-B and collagenases regulate collagen synthesis and remodelling of ECM

Inflammatory resolution:
- Cells: macrophages shift from M1 to M2 phenotype and Tregs help control and suppress excessive inflammation
Molecular mechanism:
- Resolving and protectin promote resolution of inflammatory by stopping neutrophil recruitment and promoting macrophage clearance of apoptotic cells
- IL-10 inhibits further production of pro-inflammatory cytokines and aids the transition to tissue repair.