| الوصف: |
Repair or reconstruction after a peripheral nerve injury is a challenge because functional outcome is still unsatisfactory. Treatment in patients with diabetes may be further demanding. Nerve regeneration after nerve injury was investigated, using various repair and reconstruction models, including immediate and delayed repair, bioengineered conduits, or nerve autografts as well as a possibility to stimulate regeneration with the lactoferrin-derived peptide PXL01 in healthy Wistar and diabetic Goto-Kakizaki (GK) rats. I focused on axonal outgrowth in relation to expression of Heat Shock Protein 27 (HSP27) (neuroprotection), Schwann cell response (activated and apoptotic) as well as macrophage response (activated – invading and pro-healing) in sciatic nerve and dorsal root ganglia (DRG). In Paper I, expression of injury-induced HSP27 was investigated with respect to axonal outgrowth after no or immediate nerve repair or repair after a short delay in healthy and diabetic GK rats. A nerve injury, with or without any type of repair, increased HSP27 expression in the injured nerve and in DRG without any impact on axonal outgrowth. A delayed nerve repair had no influence on axonal outgrowth. Paper II focused on nerve regeneration in hollow and modified (inserted membrane with or without gold or goldcobalt oxide nanoparticles) conduits used to reconstruct a nerve defect in healthy rats. Chambered conduits, especially the modified with inserted membrane with nanoparticles, increased axonal outgrowth and with improvement of other aspects of regeneration (i.e., increased HSP27 expression and activated Schwann cells but less apoptotic Schwann cells). In Paper III, a substance that suppress inflammation - the lactoferrin-derived peptide PXL01 with its sodium hyaluronate carrier - was used to potentially stimulate nerve regeneration after immediate nerve repair in healthy rats. Local application of PXL01, compared to sodium hyaluronate or to saline, had an anti-inflammatory effect (activated CD68 stained macrophages) without affecting pro-healing (CD206 stained) macrophages, but did not influence nerve regeneration. In Paper IV, application of PXL01 was compared to saline regarding nerve regeneration in nerve autografts in healthy and diabetic GK rats. PXL01 increased axonal outgrowth in sciatic nerve, despite a decrease in activated Schwann cells. The treatment increased HSP27 ratio in DRGs. Diabetes decreased axonal outgrowth and impacted activated Schwann cells and sensory neurons in sciatic nerve and DRG, respectively, and had some influence on HSP27 expression and pro-healing macrophages in nerve autografts.In conclusion, injured sciatic nerves should appropriately be repaired, but a short delay does not influence axonal outgrowth. HSP27 expression in sciatic nerve or in DRG, despite increased after nerve injury with or without a repair, is not associated with axonal outgrowth after any repair or reconstruction procedure. Nerve regeneration can be improved in modified bioengineered nerve conduits, particularly if nanoparticles are added to an inserted membrane. PXL01 decreases inflammation, without affecting prohealing macrophages, after nerve repair without any effect on nerve regeneration, indicating its potential use to treat “tethered/scarred” neuroma. In hypoxic environments, like nerve autografts, nerve regeneration is improved by application of PXL01. Diabetes increases HSP27 expression in uninjured nerves and decreases axonal outgrowth, independent of repair or reconstruction modality, after injury. |