10.14 Wound healing

Question 1

wound healing

• repair
• regeneration
• cell types

Answer 1

• repair: replacement by scar (fibrosis)
• regeneration: replacement by cells (similar but not exactly the same kind). only in tissue capable of dividing
• cell types
  
  • labile cells: continuously dividing (skin, epith, endoth)
  • stable cells: quiescent but can be stimulated to divide (liver)
  • “permenant” cells: terminally differentiated (neutrophils, plasma cells)

Question 2

labile cells

Answer 2

• skin: epithelial stem cells in hair follicle
• intestine: crypt cells from intestine crypts
• liver: hepatic stem cells
• eye: corneal stem cells around cornea of eye (not on the cornea)

Question 3

stable cells

Answer 3

• priming (cytokines: TNF, IL-6) >> proliferation (HGF, TGF-alpha, norepinephrine, insulin, thyroid hrm, growth hrm) >> growth inhibition (TGF-beta, activin)
• when a portion of liver is cut off, the liver doesn’t grow from the cut edge, but the remaining part grows out

Question 4

repair process

Answer 4

• granulation tissue formation: VEGF, angiopoeitins, PDGF, TGF-beta (growth inhibition for liver)
• growth factors (EGF, PDGF, TGF-alpha,-beta, GFG, IL1/TNF)
• fibrosis (scarring: collagen deposition (TGF-beta)

Question 5

TGF alpha and beta

Answer 5

• TGF-alpha: proliferation of liver, growth factors in repair process
• __
• TGF-beta: growth inhibition for liver after proliferation, granulation tissue formation factor, growth factor, collagen deposition

Question 6

Timing of wound healing

• initial
• 1-3 days
• 3-5 days
• 1 week
• 1-4 week
• 2-3 months

Answer 6

• initial: clot, scab formation
• 1-3 days: acute inflammation and exudation
• 3-5 days: macrophages, PMN repalced by mononuclear leukocytes (macrophages)
• 1 week: granulation tissue, fibroblasts
• 1-4 week: more scar, less granulation tissue
• 2-3 months: remodeling of scar

Question 7

angiogenesis

• make new
• from pre-existing

Answer 7

• mobilization of endothelial precursor cells from bone marrow makes new blood vessels
• pre-existing vessels can have capillary sprouting (used by tumor also)

Question 8

fibrosis

Answer 8

fibroblast Golgi produces helical pro-collagen which is cleaved to become collagen outside of the cell

• collage ndeposition linearly increases from approx. 2 days after wounding
• scar tissue does not have melanocytes: white
• heavy scarring leads to tissue contraction
• “organizing” means fibrosis (organizing pneumonia, thrombus)

Question 9

factors in fibrosis

Answer 9

Question 10

wound healing of liver

• cells only
• cells and matrix

Answer 10

• cells only: cells regenerate
• cell + matrix: proliferation of remaining cells and repair by scarring

Question 11

primary vs. secondary union

Answer 11

• primary: clean, incised wound >> minimal scarring
• secondary: large, “dirty” wound >> significant scarring, granulation tissue and wound contraction

Question 12

pathology of wound healing

• too much
• too little
• absence

Answer 12

• too much: strictures (scar tissue invading into lumen), keloids (excessive amount of collagen), exuberant granulation tissue (pyogenic granuloma aka “proud flesh)
• too little: fistulas (e.g., Chrons dz; “tunnelling” in the intestines), sinus tracts, dehiscence (wound is pulled apart before healing; in MI)

Question 13

collagenase regulation

Answer 13