Repair and Regeneration

Question 1

Granulation tissue

Answer 1

Fibroblasts and vascular endothelial cells proliferate in the first 24 to 72 hrs of the repair process to form a specialized type of tissue called granulation tissue.

Characteristic histological feature is the presence of new small blood vessels (angiogenesis) and the proliferation of fibroblasts.

Fibroblasts proliferate and form collagen and ECM components.

Endothelial cells proliferate and form new vessels. New vessels transport oxygen and nutrients to site of injury, macrophages and waste products are removed.

Question 2

Re-epithelialization

Answer 2

Type of repair of suprainstructure (if possible). Epithelimum (either endoderm or ectoderm-derived) can regenerate from new epithelial cells derived from adjacent cells (basal cells in skin, basal cells in esoghagus, epithelial cells in bronchus, hepatocytes in live, epithelial cells in renal tubules, Alveolar Type II cells–> Type I cells) or stem cells ( stem cells in hair follicles, stem cells in depths of crypts in duodenum or colon)

Question 3

Regeneration

Answer 3

Tissue-based macrophage in liver (Kupffer cell) can regenerate into new liver tissue.

Question 4

Resolution without/with minimal scar

Answer 4

Seen in a range of injuries, followed by re-epithelialization or regeneration.

Question 5

Scar Formation

Answer 5

Normal Scar: Initial scar is created by Collagen type III, followed by remodeling with Collagen Type I.

Pathologic scar:
Caused by:
a) inadequate granulation tissue formation

b) Excess/exuberant scar formation/repair
- exuberant granulation tissue
- other variants:
1) cirrhosis (persistent liver injury overcomes regeneration potential)
2) Hypertrophic scar (scar raised beyond boundary of wound, can regress)
3) Keloid scar (scar raised beyond boundary of wound, CANNOT regress)
4) Desmoid tumor (aggressive fibromatoses or benign neoplasm)

Question 6

Systemic factors that adversely influence repair

Answer 6

Systemic:
Nutritional: Impair collagen synthesis
-protein deficiency
-vitamin C deficiency

Metabolic: delay repair

• Diabetes
• Glucocorticoids (inhibit collagen synth)

Vascular: Ischemia, venous drainage

• thrombosis
• arteriosclerosis and atherosclerosis/diabetic change
• Venous drainage impairment: varicose veins

Question 7

Local factors that adversely impact repair

Answer 7

Infection
Persistence of insult (e.g. hep C and ethanol)
Trauma (early movement prior to completion of repair)
Trauma( foreign material)
Size/location