Peripheral nerve proxima///+ distal transected nerve heals spontaneously by contraction healing and neuroma (neural scar) formation The endoneurial stroma is a nonregenerative tissue Following transection, it forms neural scar(neuroma) Irreversible injury Contraction occurs
Peripheral nerve The endoneurial stroma is a nonregenerative tissue.Following transection, it forms neural scar (neuroma). Irreversible injury. Contraction occurs. transected nerve heals spontaneously by contraction and neuroma (neural scar) formation
SUMMARY SO FAR Regenerative Nonregenerative tissues tissues, rever- Reversible injury. sible injury No contraction. Contraction scar SKIN epidermis dermis BM NERVE myelin endoneurial stroma BM
SUMMARY SO FAR Regenerative tissues. Reversible injury. No contraction. Nonregenerative tissues. Irreversible injury. Contraction +scar. SKIN epidermis dermis BM NERVE myelin endoneurial stroma BM
Conclusion: Inverse relation between contraction and regeneration During adult healing, no contraction is observed following injury to epithelia or basement membrane Contraction is only observed following injury to stroma Contraction only observed following irreversible injury
Conclusion: Inverse relation between contraction and regeneration • During adult healing, no contraction is observed following injury to epithelia or basement membrane. • Contraction is only observed following injury to stroma. • Contraction only observed following irreversible injury
3. Antagonistic relation between contraction and regeneration a. Data from spontaneously healing wounds b. Blocking of contraction using scaffolds c. Isolation of contraction during island' grafting d. scar formation vs inhibition of contraction e. Contraction during impaired healing
3. Antagonistic relation between contraction and regeneration a. Data from spontaneously healing wounds b. Blocking of contraction using scaffolds c. Isolation of contraction during “island” grafting d. Scar formation vs inhibition of contraction e. Contraction during impaired healing
Quantitative description of healing processes Initial wound area is Ao Wound eventually closes up spontaneously. Final area is Af Final wound area is distributed among fractions that closed by contraction ( %C), scar formation %s) or regeneration (%R) This is the configuration of the final state Wound closure rule c+S+R=100
Quantitative description of healing processes • Initial wound area is A o • Wound eventually closes up spontaneously. Final area is A f . • Final wound area is distributed among fractions that closed by contraction (% C), scar formation (%S) or regeneration (% R). • This is the configuration of the final state. • Wound closure rule: C + S + R = 100