2. • Replacement of damaged tissue by new healthy
one.
• Types:
• Regeneration: of the same type.
• By CT deposition:
– fibrosis: (scarring): all except CNS.
– Gliosis: in CNS.
3. What determines the type of
repair?
• By type of damaged cells as different cell
types have different capacity to divide.
Labile cells: Stable cells: Permenent cells:
•Contineously actively divide.
• have short G0
•Complete regeneration after
injury.
•E.g: surface epithelia & mm.
•G0 :physiological state of non
division of quiescent cells that
re-enter mitotic cell cycle when
needed.
•Limited capacity of division.
• remain in long G0 till need.
•Repair by regeneration or
fibrosis.
•E.g: parenchymal cells of
glandular organs,
mesenchymal cells as
fibroblats.
•No division in postnatal
life.
•Repair by CT deposition.
•E.g:nerve cells(gliosis),
cardiac ms. Cells
(fibrosis).
4. Factors affecting repair
I. Factors affecting efficiency & type of repair:
Local factors:
– Type of damaged cells.
– Blood supply e.g ischaemia lead to defective repair.
– Persistent infection or FB.
– Extent of tissue damage.
General factors:
– Age.
– Nutritional difficiencies e.g ptn, vit.C, D & zinc.
– Glucocorticoids & cytotoxic drugs.
– Endocrinal ds. E.g diabetes & cushing.
5. Factors affecting repair (cont.)
• II.Factors controlling the michanism of repair:
GF:
• Stimuli that control cell division.
• Mostly produced my macrophages.
• Include:
– EGF: mitogenic for epith. Cells & fibroblasts.
– PDGF:mitogenic for fibroblasts, neuroglia cells & smooth ms.
– FGF: fibroblast proliferation & form. Of new bl. Vs.
– TGFα: stimulatory (fibroblast proliferation ), inhibitory
(collagen degradation).
– TGFβ: stimulatory (fibrogenesis) inhibitory (growth inhibition
action).
– IL1 & TNF.
6. II.Factors controlling the michanism of
repair (cont.):
Cell to cell interaction (contact inhibition):
Normally: cells are in intimate contact prevent un-needed
division, due to inhibitory signals, receptors interaction &
chalones (growth inhibition factors as TGFβ which suppress
mitosis).
With tissue damage cell loss loss of contact inhibition
stimulate cells to divide till contact again ( at end of repair)
contact inhibition
Cell to matrix interaction:
Normally: with ECM ptns (fibronectin & laminin) with role in
cell migration, proliferation, differentiation & adhesion.
Abnormality in this interaction serious effects (as abnormal
repair).
7. II.Factors controlling the michanism of
repair (cont.):
Cell to cell interaction (contact inhibition):
Normally: cells are in intimate contact prevent un-needed
division, due to inhibitory signals, receptors interaction &
chalones (growth inhibition factors as TGFβ which suppress
mitosis).
With tissue damage cell loss loss of contact inhibition
stimulate cells to divide till contact again ( at end of repair)
contact inhibition
Cell to matrix interaction:
Normally: with ECM ptns (fibronectin & laminin) with role in
cell migration, proliferation, differentiation & adhesion.
Abnormality in this interaction serious effects (as abnormal
repair).
